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 ON 
 
 INTELLIGENCE.
 
 TAINE'S WORKS. 
 
 2 VOls. 
 
 /. NOTES ON ENGLAND. 
 
 II. ENGLISH LITERATURE. 
 
 III. ON INTELLIGENCE. 
 
 IV. THE PHILOSOPHY OF GREEK ART. 
 
 V. THE PHILOSOPHY OF ART IN THE 
 
 NETHERLANDS. 
 VI. THE IDEAL IN ART. 
 VII. ITALY, ROME AND NAPLES. 
 VIII. ITALY, FLORENCE AND VENICE. 
 
 HOLT & WILLIAMS, Publishers 
 
 25 BOND STREET, NEW YORK.
 
 ON 
 
 INTELLIGENCE 
 
 BY 
 
 H. TAINE, D.C.L. OXON 
 
 TRANSLATED FROM THE FRENCH BY 
 
 T . D . H A Y E 
 
 AND REVISED WITH ADDITIONS BY THE AUTHOR 
 
 NEW YORK 
 
 HOLT & WILLIAMS 
 1872
 
 McCain Co., 
 
 STBRKOTYPEBS, 
 NlWBCEOH, N. T. 
 
 LANGE, LITTLE & HILLHAN, 
 
 PKl.VTKUS, 
 
 108 to 114 WOOSTEB ST., V. Y.
 
 THE Work an author has most fully meditated ought to 
 be honored by the name of the friend whom he has most 
 respected. I dedicate this book to the Memory of FRANZ 
 WOEPKE, Orientalist and Mathematician, who died at Paris, 
 
 in March, 1864. 
 
 H. TAINE.
 
 It I 
 
 IF I am not mistaken, we mean nowadays by Intelligence, 
 what was formerly called Understanding or Intellect that 
 is to say, the faculty of knowing ; this, at least, is the sense 
 in which I have taken the word. 
 
 At all events, I here intend to examine our knowledge, 
 that is to say our cognitions, and nothing else. The words 
 faculty, capacity, pozver, which have played so great a part in 
 psychology, are only, as we shall see, convenient names by 
 means of which we put together, in distinct compartments, 
 all facts of a distinct kind ; these names indicate a character 
 common to all the facts under a distinct heading ; they do 
 not indicate a mysterious and profound essence, remaining 
 constant and hidden under the flow of transient facts. This 
 is why I have treated of cognitions only, and, if I have men- 
 tioned faculties, it has been to show that in themselves, and 
 as distinct entities, they do not exist. 
 
 Such a precaution as this is very necessary. By means of 
 it, psychology becomes a science of facts ; for our cognitions 
 are facts ; we can speak with precision and detail of a sensa- 
 tion, of an idea, of a recollection, of a prevision, as well as of 
 a vibration, or other physical movement ^ in the one case as 
 in the other there is a fact in question ; it may be reproduced, 
 observed, described ; it has its precedents, its accompani- 
 ments, its consequents. In little, well-selected, important, 
 significant facts, stated with full details and minutely noted, 
 we find at present the materials of every science ; each of 
 them is an instructive specimen, the head of a rank, a salient 
 example, a clear type to' which a whole row of analogous 
 cases conform ; our main business is to know its elements, 
 how they arise, in what manner and under what conditions 
 they combine, and what are the constant effects of combina- 
 tions so produced.
 
 viii PREFA CE. 
 
 Such is the method it has been attempted to follow in 
 this work. In the first part, the elements of knowledge have 
 been determined; by consecutive reductions we have arrived 
 at the most simple elements, and have passed from these to 
 the physiological changes which are the condition of their 
 origin. In the second part, we have first described the mech- 
 anism and general effect of their combination ; then, applying 
 the law we have discovered, we have examined the elements, 
 formation, certitude, and range of the principal kinds of our 
 knowledge, from that of individual things to that of general 
 things, from the most special perceptions, previsions, and 
 recollections, up to the most universal judgments and axioms. 
 
 In these inquiries, Consciousness, our principal instrument, 
 is not sufficient in its ordinary state ; it is no more sufficient 
 in psychological inquiries than the naked eye in optical in- 
 quiries. For its range is not great ; its illusions are many 
 and invincible ; it is necessary continually to beware of it ; 
 to test and correct its evidence, nearly always to assist it, to 
 present objects to it in a brighter light, to magnify them and 
 construct for its use a kind of microscope or telescope ; at all 
 events, to arrange the surroundings of the object, to give it 
 the necessary relief by means of contrasts, or to find beside 
 it indications of its presence, indications plainer than it is, 
 and indirectly pointing out its nature. 
 
 Here lies the principal difficulty of the analysis. As far 
 as pure ideas and their relations with names are concerned, 
 the principal aid has been afforded by names of numbers, and, 
 in general, by the notations of arithmetic and algebra ; thus 
 we have brought again into light a great truth guessed at by 
 Condillac, and which has lain for a century dormant, buried, 
 and as though lifeless, for want of satisfactory evidence. As 
 to images, their effacement, their revival, their antagonist 
 reductives, the necessary magnifying is found in the singular 
 and extreme cases observed by physiologists and medical 
 men, in dreams, in somnambulism and hypnotism, in illusions 
 and the hallucinations of sickness. As to sensations, signifi- 
 cant instances are found in the sensations of, sight, and es- 
 pecially in those of hearing. By means of such evidence, and 
 of the recent discoveries of physicists and physiologists, we
 
 PREFACE. ix 
 
 have attempted to construct or sketch out the whole theory 
 of elementary sensations, to advance beyond the ordinary 
 bounds, up to the limits of the mental world, to indicate the 
 functions of the principal parts of the brain, to conceive the 
 connection of molecular nervous changes with thought. 
 Other abnormal cases, borrowed both from students of in- 
 sanity, and from physiologists, have enabled us to explain 
 the general process of illusion and rectification, whose suc- 
 cessive stages constitute our various kinds of knowledge. 
 After this, to elucidate our knowledge of bodies, and of our- 
 selves, valuable indications have been found in the profound 
 and closely reasoned analysis of Bain, Herbert Spencer, and 
 Stuart Mill, in the illusions of persons who have lost limbs, 
 in all the different illusions of the senses, in the education of 
 the eye in persons born blind who have recovered their sight 
 by operations, in the singular alterations which the idea of 
 self undergoes during sleep, hypnotism, and madness. We 
 have then been able to enter upon the examination of the 
 ideas and general propositions which make up the sciences, 
 properly so called, to profit by Mr. Mill's acute and accurate 
 inquiries respecting Induction, to establish against Kant and 
 Mill a new theory of necessary propositions, to study by a 
 series of examples what is termed the explanatory reason of 
 a law, and to conclude with general views on science and 
 nature, while pausing before the metaphysical problem which 
 'is the first and last of all. 
 
 Between psychology thus conceived and history as it is 
 now written, the relationship is very close. For history is 
 applied psychology, psychology applied to more complex 
 cases. The historian notes and traces the total transforma- 
 tions presented by a particular human molecule, or group of 
 human molecules ; and, to explain these transformations, 
 writes the psychology of the molecule or group ; Carlyle has 7 
 written that of Cromwell ; Sainte-Beuve that of Port Royal ; 
 Stendhal has made twenty attempts on that of the Italians ; 
 M. Renan has given us that of the Semitic race. Every pers- 
 picacious and philosophical historian labors at that of a man, 
 an epoch, a people, or a race ; the researches of linguists, 
 mythologists, and ethnographers have no other aim ; the
 
 x PREFACE. 
 
 task is invariably the description of a human mind, or of 
 the characteristics common to a group of human minds; and, 
 what historians do with respect to the past, the great novel- 
 ists and dramatists do with the present. For fifteen years I 
 have contributed to these special and concrete psychologies ; 
 I now attempt general and abstract psychology. To com- 
 prise it exhaustively, there would be required a theory of 
 the Will in addition to the theory of the Intelligence ; if I 
 may judge of the work I do not venture to undertake by 
 that which I have attempted to accomplish, my strength is 
 not equal to this ; all that I venture to hope is that the reader 
 will grant me his indulgence, in consideration of the difficulty 
 of the task and the length of the effort. 
 
 H. TAINE. 
 
 December, 1869.
 
 I LIBRARY I 
 
 -^p- Jf 
 
 LlNOl^^ 
 
 -~ "^^^ 
 
 TABLE OF CONTENTS. 
 
 PART THE FIRST 
 THE ELEMENTS OF KNOWLEDGE. 
 
 BOOK I. 
 OF SIGNS. 
 
 CHAPTER I. 
 
 OF SIGNS IN GENERAL AND OF SUBSTITUTION. 
 
 PAOB 
 
 I. Different examples of signs A sign is a present experience which 
 suggests to us the idea of a possible experience I 
 
 II. Names are a species of signs Examples Proper names A proper 
 name is a sensation or image of the eye or ear, which calls' up in us 
 a group of more or less definite images 2 
 
 III. Frequently this group is not called up Examples The name then 
 becomes the substitute of the group 2 
 
 IV. Other examples of substitution In arithmetic In algebra Nature 
 and importance of substitution ,. 4 
 
 CHAPTER II. 
 
 OF GENERAL IDEAS AND SIMPLE SUBSTITUTION. 
 
 I. Proper and common names Importance of common or general names 
 They are the first terms of couples The second terms of such 
 couples are general and abstract characters 7
 
 ii CONTENTS. 
 
 PAOE 
 
 II. Consequences of this Experience of such second terms is impossible 
 
 Reasons of this impossibility Different examples Difference be- 
 tween the vague image aroused by the name, and the precise charac- 
 ter denoted by the name Difference between the sensible image and 
 pure idea 8 
 
 III. Actual formation of a general idea That which is evolved in us, 
 when we have seen a series of similar objects, is a final tendency 
 resulting in a metaphor, a sound, or an expressive gesture Contem- 
 porary instances Early instances A general name is the residuum of 
 an expressive sound When we conceive a general quality, there is 
 nothing more in our minds than a tendency to name, and a name 
 This name is the substitute of an impossible experience 10 
 
 IV. A general Idea is nothing but a name provided with two characters 
 The first is the property of being called up on the perception of each 
 individual of a class The second, the property of calling up in us 
 images of individuals of this class, and of this class only By these 
 two properties, the general name corresponds exclusively to the 
 general quality, and becomes its mental representative Utility of 
 this substitution 12 
 
 V. Formation of general names in the case of little children The 
 faculty of language is founded on the consecutive tendencies which 
 survive the experiences of similar individual cases, and correspond 
 to what there is in common to these individuals rExamples of this 
 tendency in children Special meanings given by them to the names 
 we teach them Originality and variety of their invention Their 
 tendencies to name finally coincide with ours Acquisition of lan- 
 guage Difference between human and animal intelligence 15 
 
 VI. Passage from abstract to collective names The name which denoted 
 a general quality denotes a group of general qualities Examples 
 The name then becomes the substitute of several other names, and the 
 mental representative of a group of general qualities These sub- 
 stitutes are what we term Ideas 19 
 
 CHAPTER III. 
 
 OF GENERAL IDEAS AND REPEATED SUBSTITUTIONS. 
 
 I. Certain General Characters do not produce in us a distinct impression 
 They are therefore incapable of exciting in us a general tendency 
 and a name Indirect process by which we arrive at conceiving 
 thtm Example in the case of numbers Their mental representa- 
 tive is a name of number Formation of names of numbers Series 
 of superimposed substitutions Our idea of a number is that of a 
 name substituted for another name combined with unity 22 
 
 II. Examples in Geometry Our Idea of a circle is not the sensible 
 figure we imagine, but a group of combined names, mental represen-
 
 CONTENTS. xiii 
 
 PAGE 
 
 tatives of certain abstract characters Substitution of the formula 
 for the impossible experience We conceive the ideal object by 
 means of its formula Universal employment of substitution in 
 mathematics 25 
 
 III. Examples in the cases of Infinite Series Time and Space In the 
 case of an infinite series or quantity, we do not conceive the 
 totality of its terms, but certain of its terms, and one of their 
 abstract characters represented in us by a name Substitution of 
 the formula for the impossible experience We conceive the infinite 
 series or quantity by means of its formula 27 
 
 IV. Summary Our general Ideas are names, substitutes for impossible 
 experiences Psychological Illusion which consists in distinguishing 
 the idea from the name Singular effects and general cause of this 
 illusion It is natural that signs should cease to be observed, and 
 end by being considered as mere nothings False theories on the 
 pure spirit The mental representative we term a pure idea, is 
 never more than a name pronounced, understood, or imagined 
 Names are a class of Images The Laws of Ideas are reduced to the 
 Laws of Images . 2q 
 
 BOOK II. 
 OF IMAGES. 
 
 CHAPTER I. 
 
 OF THE NATURE AND REDUCTION OF IMAGES. 
 
 I. An Experience An Image is a spontaneously reviving sensation, 
 usually less energetic and precise than the sensation proper The 
 force and precision of the image varies in individuals and according 
 to its kinds Personal Instances Instances of children accustomed 
 to calculate mentally Precocious mathematicians Blindfolded chess- 
 players Painters who can draw portraits or make copies from memory 
 Schools of Art in which this faculty is cultivated Other instances 
 of the voluntary revival of visual sensations Sensations of the other 
 sense have their corresponding images Images corresponding to au- 
 ditor/ s^a.-v tions Examples 33 
 
 II. Circumstances increasing the precision and force of the image In 
 such a' ca-e it becomes more and more like the sensation Instances 
 in which the sensation is recent Instances in which the sensation 
 is immediately expected Examples of images corresponding to 
 sensations of hearing, of sight, of smell, of taste, of touch Equal 
 and similar effects of the image and the corresponding sensation 
 In these cases the image is taken, at least momentarily, for the 
 sensation corresponding to it 39
 
 iv CONTENTS. 
 
 PAGB 
 
 III. How, in spite of this, it differs from the corresponding sensation 
 The illusion accompanying it is speedily rectified The image inva- 
 
 . riably comprises an illusion of greater or less duration Dugald 
 Stewart's Law Instance of an American preacher Testimony of 
 M. Flaubert Instance of an English painter Evidence of a chess- 
 player Observations of Goethe and of M. Maury Voluntary hallu- 
 cinations Various circumstances under which the image becomes hal- 
 lucinatory These extreme cases are evidence as to the normal state 
 In the normal state, the illusion is at once destroyed It is destroyed 
 by the presence of an antagonist or reductive 41 
 
 IV. Cases in which the contradicting sensation is too feeble or is annulled 
 Hypnagogic Hallucinations Experiments of M. Maury Personal 
 experience Passage from the simple image to the hallucinatory image, 
 and from that to the simple image Other cases in which the contra- 
 dictory sensation is annulled Wounds in battle Hallucinations 
 strictly so-called Hallucinations of sight after the prolonged use of 
 the microscope Partial restoration of the antagonist sensation Path- 
 ological instances In such cases, the hallucination is destroyed 
 Story of Nicolai General means of destroying the hallucination 
 Case in which a sensation calls up an illusion properly so-called 
 Story of Dr. Lazarus In such cases, the suppression of the exciting 
 sensation destroys the illusion 46 
 
 V. Other antagonists Reminiscences and general judgments form, by 
 their combination, a body of auxiliary reductives Their influence is 
 more or less prompt and energetic Different examples Cases in 
 which their influence is not sufficient The antagonistic sensation, 
 which is the special reductive, is then annulled Examples in intoxi- 
 cation and illness The patient then concludes the hallucination to be 
 an hallucination Instances in which all reductives are annulled, or 
 of complete mental alienation Remarkable case recorded by Dr. 
 Lhomme 60 
 
 VI. General views as to the thinking being The mind is a collection of 
 images, like a polypus General views as to the normal reasonable 
 wakeful state Mutual equilibrium of various images Constant re- 
 pression of the rising hallucination by special reductives Necessity 
 of sleep Summary as to images Their characters and relations to 
 sensation The image is the substitute of the sensation 66 
 
 CHAPTER II. 
 
 LAWS OF THE REVIVAL AND OBLITERATION OF IMAGES. 
 
 I. The image of a sensation may rise after a considerable interval Ex- 
 amples It may then rise without having done so during the interval 
 Examples Singular, morbid instances of the revival of images 
 which seemed obliterated Recollection of a language learned in
 
 CONTENTS. xv 
 
 PAGE 
 
 childhood, and afterwards forgotten Automatic recollection of a series 
 of sounds heard mechanically Probability that every sensation we 
 experience preserves an indefinite aptitude for revival 70 
 
 II. Different sensations have not all this aptitude for revival in an equal de- 
 gree Examples General circumstances augmenting this aptitude 
 Extreme attention, voluntary or involuntary The persistence of im- 
 pressions acquired in fancy is thus explained In what attention con- 
 sists Competition between our different images The Law of Natural 
 Selection is applicable to Mental Events Another circumstance which {/* 
 augments the aptitude for revival Repetition Examples Why these 
 two circumstances augment the aptitude for revival 73 
 
 III. Special circumstances calling up, at a particular moment, one image 
 rather than another Example The reviving image has already, 
 either by contiguity or by similitude commenced to revive Why par- 
 tial revival excites complete revival 77 
 
 IV. Absence of the indicated circumstances Want of attention Want of 
 repetition Enormous number of sensations which thus lose their apt- 
 itude for revival Cases in which two tendencies neutralize each other 
 Repetition and variety of experience blunt the image Origin of 
 general names, and of the vague images accompanying them The 
 majority of our sensations do not exist in our minds in the state of ex- 
 press images, but in the state of dull consecutive tendencies. ... 80 
 
 V. General views as to the history of images and ideas They are in per- 
 petual conflict for preponderance Effect of internal laws and external 
 incidents in determining which preponderates Temporary oblitera- 
 tion, prolonged or definitive, of a whole group of images Partial and 
 total paralysis of memory, excited by fatigue, loss of blood, blows, 
 apoplexy Examples Forgetfulness of names Forgetfulness of 
 spoken names, but not of the meaning of written names Restoration of 
 lost faculties Appearance of new faculties Examples Aptitudes and 
 faculties are connected with the organic state Possibility of two or- f 
 ganic states severed from one another, and recurring periodically in the 
 same individual Case of an American lady Two lives and two men- 
 tal states may thus be met with in the same person Instances In 
 what the moral personality consists Two moral personalities may suc- 
 ceed cne another in the same individual What forms the continuity 
 of a distinct moral person is the continuous revival of the same dis- 
 tinct group of images 84
 
 BOOK III. 
 OF SENSATIONS. 
 
 CHAPTER I. 
 
 OF SENSATIONS OF HEARING AND THEIR ELEMENTS. 
 
 PAO1 
 
 I. Reduction of ideas to a class of images, and of images to a class of 
 sensations Enumeration of ihe principal kinds of sensations What 
 is meant by the word sensation Distinction between the property of 
 the external object which excites the sensation, and the sensation it- 
 self Distinction between the crude sensation and the apparent posi- 
 tion attributed to it by consciousness Distinction between the sensa- 
 tion and the state of the nerves and nervous centres Special and 
 primitive character of sensation 93 
 
 II. Classification of sensations by Gerdy, Mueller, Longet, and Bain Its 
 practical convenience and scientific inadequacy In what the classified 
 sensations differ from other facts also classified We cannot distin- 
 guish the elements of sensations Physical and Physiological Science 
 cannot distinguish these elements, but only the conditions of whole 
 sensations Sensations appear to be irreducible to other more simple 
 data Psychology seems, with reference to them, what Chemistry is 
 with reference to simple bodies 95 
 
 III. Psychology stands with reference to them as Chemistry did with refer- 
 ence to Chemical compounds before the discovery of simple bodies 
 Analysis of the sensations of sound Various kinds of sounds They 
 are, in appearance, irreducible to one another The Wheel of Savart 
 and the Siren of Helmholtz Musical Sound The continuous sensa- 
 tion is then composed of successive elementary sensations Instance 
 of very deep sounds We can distinguish in these the successive ele- 
 mentary sensations Each of them has a certain duration, and passes 
 from a minimum to a maximum of intensity Instance of certain mu- 
 sical notes Savart's experiment Enormous number of elementary 
 sensations succeeding in a second to form a whole sensation of acute 
 sound Their number increases in proportion to the acuteness of the 
 sound In this case the elementary sensations cease to be distinguish- 
 able by consciousness Appearance which the elementary sensation 
 must therefore assume It actually assumes this appearance The char- 
 acters of deep, acute, high, low, full, drawn-out, firm, vibrating, found 
 in the total sensation are explained by the arrangement of the element- 
 ary sensations 99
 
 CONTENTS. xvii 
 
 PAQB 
 
 IV. Continuation of the analysis of sensations of sound Explanation of 
 the sensation of intensity Explanation of the sensation of tone 
 Discovery of Helmholtz Explanation of the sensation of noise Con- 
 struction of the whole of the total sensations of sound by means of the 
 elementary sensations of sound Analysis of the elementary sensation 
 of sound It is composed of a maximum, a minimum, and an infinite 
 number of intermediate states 104 
 
 CHAPTER II. 
 
 SENSATIONS OF SIGHT, OF SMELL, OF TASTE, OF TOUCH, AND THEIR ELEMENTS. 
 
 I. Total sensations of sight The spectrum Infinite number of total 
 sensations of color There are at least three elementary sensations of 
 color It is sufficient to admit three Theories of Young and Helmholtz 
 Experimental confirmation of this theory Partial paralysis of the 
 aptitude for experiencing sensations of color Experience which raises 
 to a maximum the sensation of violet and of red The three elemen- 
 tary sensations are those of red, violet, and probably green. ... no 
 
 II. Construction of the various sensations of spectral color by the combina- 
 tions of these elementary sensations Sensation of white Comple- 
 mentary colors Law governing the mixture of spectral colors Their 
 saturation and their proximity to white Sensation of black, or \rant 
 of retinal sensation It furnishes a new element for the composition of 
 the various total sensations of color Different examples Summary 
 We cannot distinguish by consciousness the elements of the elemen- 
 tary sensations of color Why Analogy of these elementary sensa- 
 tions and the elementary sensations of sound Proof that there are 
 elements in these as in the others Wheatstone's Experiment Enor- 
 mous number of successive elements composing an elementary sensa- 
 tion of color Indications and conjectures as to the ultimate elements 
 Consciousness perceives aggregates only 114 
 
 III. Total sensations of taste and smell Increased difficulties Reason 
 of these difficulties Preliminary distinctions Smell Sensations of 
 smell strictly so called must be separated from those of nasal touch 
 Examples And from those of the alimentary canal Examples And 
 from those of the nerves of the air passages Examples We thus iso- 
 late sensations of pure smell Their types Taste Sensations of taste 
 strictly so called must be separated from other accompanying sensations 
 Accompanying sensations of smell and of nasal touch Accompany- 
 ing sensations of temperature and touch in the mouth Sensations of 
 taste proper, vary with the different parts of the mouth Experiments 
 of Guyot and Admyrault Extreme complication of the sensations of 
 taste and even those of pure taste Their types The action of the 
 olfactory and gustatory nerves probably has, as immediate antecedent, 
 a chemical combination, that is to say a system of molecular displace-
 
 >ui CONTENTS. 
 
 PAGE 
 
 ments Analogy between this antecedent and the vibration of ether 
 which excites the action of the retina Indications as to the mode of 
 action of the olfactory and gustatory nerves Most probably it consists 
 in a succession of actions, similar to one another and extremely short, 
 each of which excites an elementary sensation of smell or taste 
 Theory of the four special senses Each of them is a special idiom 
 constructed to represent a single order of facts General theory of 
 the senses They are all idioms The sense of touch is a general 
 
 idiom 117 
 
 IV. Total sensations of touch Increasing difficulties Reason of these 
 difficulties Preliminary distinctions First group of sensations of 
 touch ; muscular sensations Cases of paralysis in which they are ab- 
 sent Observations of Landry The two groups of nerves are distinct 
 The two groups of sensations are similar There are three kinds of 
 sensations for all the nerves of touch Sensations of contact, of tem- 
 perature, of pleasure and pain Each of these three kinds may be 
 singly preserved or abolished Observations on sick persons 
 Known conditions of each kind Experiments and observations 
 Opinion of Weber These distinctions are distinct types of activity 
 for the same nerve Experiments of Fick The different characters 
 we find in the aggregate sensations of contact, temperature, pleasure, 
 and pain, are capable of being explained by the different arrangement 
 
 of the same elementary sensations 126 
 
 V. Summary Blanks in the theory Researches which may supply them 
 The nervous action which excites a sensation is never more than a 
 displacement of nervous molecules To this elementary displacement 
 corresponds an elementary sensation The differences of total sensa- 
 tions are all caused by the diversities of grouping of the same elemen- 
 tary sensations General process and economical method followed by 
 nature in the construction of the mind 137 
 
 BOOK IV. 
 
 OF THE PHYSICAL CONDITIONS OF MENTAL EVENTS. 
 
 CHAPTER I. 
 
 OF THE FUNCTIONS OF THE NERVOUS CENTRES. 
 
 I. Conclusion of psychological analysis Commencement of the physio- 
 logical analysis 143 
 
 II. The external physical event is an accessory and distant condition 
 of the sensation It only excites the sensation through a medium ; 
 the excitation of the nerve Different kinds of sensitive nerves 
 Each has its special action The action of each is different Every
 
 CONTENTS. xix 
 
 PAGE. 
 
 nerve is capable of spontaneous action Subjective and consecutive 
 sensations Altered sensations Experiments and observations of 
 Physiologists 144 
 
 III. The nerve is a simple conductor Molecular action must be propa- 
 gated from its peripheral to its central extremity Whatever may be 
 the point of its course from which the molecular action starts, the sen- 
 sation is the same Illusions of persons who have suffered amputa- 
 tions The action of the nerves only excites sensation through a me- 
 dium, the action of the nervous centres In what the molecular move- 
 ment propagated in the nerve consists It may be propagated in both 
 directions Experiments of Bert and Vulpian If any nerve when 
 irritated excites a certain sensation it is from its central extremity be- 
 ing in connection with some portion of the nervous centres The 
 simple excitation of the nervous centres is sufficient to produce sensa- 
 tion Proof by hallucinations Instances observed by writers on in- 
 sanity Hallucinations following the prolonged use of the microscope 
 Observations of M. Robin Action of the nervous centres is the 
 necessary and sufficient condition of sensation 147 
 
 IV. The different portions of the encephalon The rachiclian bulb When 
 it alone is preserved, there are no longer sensations strictly so called 
 Experiments of Vulpian Distinction between the reflex cry and cry 
 of pain The annular protuberance Experiments of Longet and 
 Vulpian The action of the protuberance is the sufficient and neces- 
 sary condition of sensations of touch, of hearing, and of taste The 
 corpora bigemina or quadrigemina Experiments of Flourens, Longet, 
 and Vulpian The action of these tubercles is the sufficient and neces- 
 sary condition of sensations of sight Probable existence of another 
 centre whose action is the necessary and sufficient condition of sensa- 
 tions of smell 152 
 
 V. The action of these centres is the sufficient and necessary condition of 
 crude sensations Accordance of the results of Physiology and Psychol- 
 ogy Structure of the encephalon The cerebral lobes or hemispheres 
 Their gray substance Relation of intelligence to the volume and 
 extent of this gray substance The action of the cerebral lobes is the 
 sufficient and necessary condition of images or reviving sensations, 
 and consequently of all the mental operations which outstep the limits 
 of crude sensation Experiments of Flourens and Vulpian Accord- 
 ance of pathological observations 156 
 
 VI. Internal structure of the cerebral lobes Their white substance is 
 conducting only Functions of the gray substance Physiological and 
 pathological proofs Gaps in physiology The various departments of 
 gray substance fulfil identical functions, and form a group of repeating 
 and multiplying organs Pathological and physiological proofs One 
 hemisphere supplies the place of the other A portion of the hemi- 
 spheres, if large enough, supplies the place of the rest Application of 
 psychological data One element of the hemispheres repeats the action
 
 CONTENTS. 
 
 of the sensory centres, and transmits it to the other elements Why 
 the magnitude of the hemispheres and the development of their cor- 
 tical layer increases the extent of the intelligence Mechanism of the 
 formation, survival, and indefinite repetition of images Physiological 
 causes of the conflict, preponderance, and succession of images La- 
 tent images To what physiological state of the cerebral elements 
 they correspond The predominant image corresponds to a physiolo- 
 gical action propagated through the majority of the cerebral elements 
 The image is so much the weaker as the cerebral elements in which 
 the corresponding physiological action takes place are the less numer- 
 ous All we can know by consciousness are aggregates The latent 
 state is but the rudimentary state 162 
 
 VII. Summary Beneath aggregates observable by consciousness lie their 
 elements, which are invisible to consciousness Characters and signs 
 of elementary mental events Reflex phenomena Experiments of 
 Vulpian, Landry, Duges, and Claude Bernard Indications of mental 
 events in the inferior and secondary nervous centres The segments 
 of the maiTOw Probable analogy of these events and elementary sen- 
 sations Successive degrees and constant correspondence of the molec- 
 ular movement of a nervous centre, and the mental event . . . 170 
 
 CHAPTER II. 
 
 RELATIONS OF THE FUNCTIONS OF THE NERVOUS CENTRES, AND MENTAL EVENTS. 
 
 I. Distinction of physical and moral The second order of facts is 
 
 connected with the first This connection seems inexplicable Ad- 
 vantage of the preceding reductions and of the theory of elementary 
 sensations 178 
 
 II. Situation of the difficulty Notion of molecular movement in the 
 cells and fibres of the nervous centres Even if we suppose it to be 
 completely elucidated we still find its idea and that of a sensation are 
 irreducible to one another 179 
 
 III. Another method of investigation The two ideas may be irreducible 
 to one another without the two orders of facts being irreducible to one 
 another Two objects seern different to us when we acquire their 
 ideas in different ways Examples This general law is applicable to 
 the present case Absolute difference between the process by which 
 we acquire the idea of a sensation and the process by which we ac- 
 quire the idea of the nervous centres and their molecular movements 
 
 The two ideas must be irreducible to one another iSl 
 
 IV. Another series of reasons The aspect of the sensation, and that of its 
 ultimate elements must be wholly and entirely different Hypothesis 
 of two heterogeneous events Hypothesis of one and the same event 
 known under two aspects Results of the first hypothesis It is un-
 
 CONTENTS. xxi 
 
 PAUK 
 
 scientific Probability of the second Of the two points of view that 
 of consciousness is direct, and that of external perception is indirect 
 The molecular movement is but a sign of the mental event Direct 
 and remarkable confirmation of the second hypothesis The sensation 
 and its elements are the only real events of nature Rudimentary and 
 infinitesimal sensations The nervous system is but an apparatus of 
 complication and perfectionment Presence of elementary mental 
 events in the whole organized world Their probable presence below 
 this Double scale and corresponding stages of the physical and 
 
 moral world 184 
 
 V. The two faces of nature Clear and obscure portions of the physical 
 world Clear and obscure portions of the moral world To the clear 
 portions of the one correspond obscure portions of the other, and re- 
 ciprocally Each of them by its bright parts lightens up the obscuri- 
 ties of the other Comparison of the two aspects to 
 text accompanied to an incomplete translation . . /y^. . \>J 
 
 CHAPTER III. 
 
 THE HUMAN PERSON AND THE PHYSIOLOGICAL 
 
 ^s/<. 
 
 I. Usual opinion as to the human personality and its faculufei^-Me'aft* . , <. 
 
 ing of the word faculty or power Mechanical forces F^jrce 01" 
 These words do not denote any occult being All they denote is a 
 character of an event, that is to say, its particularity of being con- 
 tantly followed by another Metaphysical illusion erecting forces into 
 distinct essences 191 
 
 II. Metaphysical illusion forming of self a distinct substance Meaning of 
 
 the verb to be Our successive events are the successive components 
 
 of our self In what the faculties of the Ego consist Examples . . 194 
 
 III. Progressive ruin of scholastic entities Scientific idea of forces and be- 
 ings Its application to self and to matter Mathematical 'idea of 
 atoms A real substance is nothing more than a distinct series of 
 events A force is nothing more than the property of one of these 
 events, to be followed by one of the same series or of another series 
 Idea of nature 198 
 
 IV. The series which makes up the Ego is a fragment in the whole aggre- 
 gate of animal functions Physiological aspect Order of nervous cen- 
 tres and nervous activities The ganglia, the segments of the marrow, 
 the layers of the encephalon Pyschological aspect Order and in- 
 creasing complication of the mental events indicated or proved in the 
 different centres In proportion as the animal descends the zoological 
 scale, the different centres become more and more independent Ex- 
 periments and observations of Duges, Landry, and Vulpian Funda- 
 mental plurality of the animal The individual, animal or human, is 
 nothing more than a svstem . 200
 
 CONTENTS. 
 
 PART THE SECOND. 
 OF THE DIFFERENT KINDS OF KNOWLEDGE. 
 
 BOOK I. 
 
 THE GENERAL MECHANISM OF KNOWLEDGE. 
 
 CHAPTER I. 
 
 OF ILLUSION. PAGE 
 
 I. Summary of the first part Elements of human knowledge Principal 
 compounds formed by their combinations The formation and rectifi- 
 cation of illusions are two processes by which our various kinds of 
 ^ knowledge are built up in our minds 205 
 
 II. Examples Illusion produced at the theatre Optical illusions Illu- 
 sions of persons who have lost limbs The sufficient condition^ of be- 
 lief or affirmative judgment is the presence of the ordinary sensation 
 It does not matter whether the sensation be accompanied by its ordin- 
 ary antecedents Proofs When the condition of the mental process is 
 given, it is pursued blindly, as in the case of the vital process . . . 207 
 
 III. Consequences of this External perception is a true hallucination Ex- 
 amples In the normal and ordinary state, our dream within corre- 
 sponds to things without Psychological illusion as to external percep- 
 tion We are tempted to take it for a simple spiritual act Analogous 
 psychological illusion as to other acts of cognition 210 
 
 IV. Part played by the image which is substituted for sensation It excites 
 the same hallucinatory process Examples Case in which this pro- 
 cess becomes developed Observations of M. Maury on hypnagogic 
 hallucinations Hypnotism and somnambulism Braid's experiments 
 on suggestion Cases mentioned by Dr. Carpenter Experiments of 
 Dr. Tuke Predominance of images and of the action of the hemi- 
 spheres 213 
 
 V. Consequences Presence of images in all sensible representations and 
 in all pure ideas And again, in all external perceptions, recollections,
 
 CONTENTS. xx Ki 
 
 PAGE 
 
 previsions, and acts of consciousness General tendency of the mind 
 to hallucination In all our mental operations, there is an hallucina- 
 tion, at all events in an incipient state Examples of its development 
 Mental phrases which become external voices Effaced images 
 which, on revival, become hallucinatory Our various mental opera- 
 tions are but the various stages of this hallucination 219 
 
 CHAPTER II. 
 
 OF RECTIFICATION. 
 
 I. Example of rectification Case of reverie Double effect of the antago- 
 nist reductives The representation grows weak and ceases to appear 
 a real object Even when the representation remains distinct and 
 colored, it ceases to appear a real object General mechanism of this 
 last rectification It consists in a negation It is accomplished by the 
 attachment of a contradictory representation Various points on which 
 the contradiction may attach 226 
 
 II. Applications Rectification of theatrical illusions Rectification of 
 optical illusions Rectification of illusion by a person who has lost a 
 limb Rectification by a person under hallucination of his illusion 
 The illusion is checked either at its first, or at one of its subsequent 
 stages 227 
 
 III. Various states and degrees of the contradictory representation Case 
 in which it is feeble Case in which it is intense Case in which it is 
 transformed into a sensation Physiological theory of these different 
 states Persisting action of the centres of sensation Reflected action 
 
 of the hemispheres on the centres of sensation 230 
 
 IV. Abnormal state and maximum degree of the representation The an- 
 tagonist sensation is then ineffectual and the contradictory represen- 
 tation is not a sufficient reductive The contradictory representation 
 is only effectual upon groups of images of no higher degree than its 
 own 233 
 
 V. Normal state of wakefulness Example The first stage of rectifica- 
 tion, recollection The present image appears as a past sensation 
 Recollection, like external perception, is an illusion which results in 
 a cognition Our present dream corresponds to an anterior sensation 
 Psychological illusion respecting memory We are tempted to take 
 the knowledge of our past states for a simple spiritual act .... 235 
 
 VI. Mechanism of memory Examples The present sensation negatives 
 the surviving image of the anterior sensation It negatives the image 
 only as being a contemporary sensation The ordinary hallucinatory 
 process is checked in one point only The surviving image appears 
 as a sensation which is not present Causes of its apparent recoil 
 Every image occupies a fragment of duration and has two extremities,
 
 xxiv CONTENTS. 
 
 PAGE- 
 
 one anterior and one posterior Circumstances casting it back into 
 the past Circumstances projecting it into the future Examples 
 Successive displacements and apparant wanderings of the image prior 
 to situating itself at a greater or less distance in the past or future 
 It becomes situated by intercalation and enclosure 238 
 
 VII. Last stage of rectification Examples The image then appears as a 
 pure present image Representations, images, conceptions, and ideas 
 strictly so called Cases in which they are blunted and deprived of 
 individual peculiarities In this case they cannot become situated 
 either in the past, the present, or the future Cases in which they are 
 precise and provided with individual peculiarities Picturesque or 
 poetical vision In this case, they are promptly excluded from their 
 apparent place in the present, the past, or the future In both cases, i 
 the complete repression is immediate or prompt It is the common 
 result of the present sensation, of connected recollections, and ordinary 
 previsions 242 
 
 VIII. Psychological illusion as to consciousness We are inclined to take 
 the knowledge of our present state for a simple and spiritual act of 
 mind The representation, conception, or idea, recognized as such, is 
 but one and the same fact at two periods, in the state of illusion and 
 in that of repressed illusion Common process by which our different 
 kinds of cognitions are built up 247 
 
 BOOK II. 
 
 THE KNOWLEDGE OF BODIES. 
 
 CHAPTER I 
 
 EXTERNAL PERCEPTION AND THE IDEAS OF WHICH THE IDEA OF BODY IS 
 
 COMPOSED. 
 
 I. General character of external perception It is a true hallucination 
 The proofs in detail Its first phase is a sensation, and this sensation 
 is in itself sufficient to excite the semblance of an external body present 
 or absent After perception, there is within us, together with the 
 image of the sensation experienced, a semblance of the object per- 
 ceived, and this representation tends to become hallucinatory In 
 many instances the apparent object differs from the real object Three 
 marks of the semblance Whether confounded or not, in whole or in 
 part, with the real object, it always follows the sensation .... 250 
 
 II. In what the semblance consists It comprises, among other elements, 
 the affirmative conception of a thing possessed of properties Analysis
 
 CONTENTS. xxv 
 
 PACK 
 
 of this conception, notion, or idea A thing is nothing more than the 
 aggregate of its properties A substance is nothing more than an 
 aggregate of subsisting properties A body is nothing more than a 
 cluster of sensible properties 255 
 
 [II. Sensible properties of bodies Bodies as odorous, sapid, sonorous, col- 
 ored, hot, or cold All we understand by these properties is the power 
 of exciting in us some particular land of sensation Bodies as solid or 
 resisting Stuart Mill's analysis Primitively, resistance is nothing 
 more to us than the power of arresting a commenced series of muscu- 
 lar sensations Bodies as polished, rough, pungent, smooth, hard, soft, 
 sticky, damp All we understand by these properties is the power of 
 exciting some particular mode or modification of a sensation or of a 
 series cf muscular and tactile sensations 255 
 
 IV. Geometrical and mechanical properties of bodies Extension, figure, 
 situation, mobility These notions combined with that of resistance 
 form the essential part of the notion of body They are compounds 
 whose elements are notions of distance Bain's analysis A muscular 
 sensation more or less intense gives us the notion of resistance A 
 longer or shorter series of muscular sensations gives us the notion of 
 greater or less distance Notion of distance in one direction or notion 
 of linear extension Notion of distance in more than one direction, or 
 notion of extension of surface and volume Notion of position No- 
 tion of form An entire series of muscular sensations may be ex- 
 hausted in a greater or less time Notion of velocity Double sen- 
 sible measure of the amplitude of the same movement effected by the 
 same limb Final notion of the transit effected or of the space passed 
 through Mill's theory To what the notion of empty space traversed 
 and of continuous solid extension are reducible All the properties 
 of bodies are reducible to the power of exciting sensations . . . 257 
 
 TT. Analysis of the word power It signifies that certain sensations are 
 possible under certain conditions and necessary under certain condi- 
 tions Every property of a body is reducible to the possibility of a cer- 
 tain sensation under certain conditions and to the necessity of the 
 same sensation under the same conditions with a complementary one 
 added Confirmation of this paradox These possibilities and neces- 
 sities are lasting and independent These two properties are the es- 
 sential characters of substance By degrees, they come into opposition 
 to transient and dependent sensations, and seem to be data of a dis- 
 tinct kind and of a higher importance Development of this theory by 
 Stuart Mill 264 
 
 VI. Addition to the theory Bodies are not only permanent possibilities 
 of sensation, but aho permanent necessities of sensation In this re- 
 spect, they are forces What a body is with respect to us What a 
 body is with respect to another body Three groups of properties or 
 powers in a body These powers are otherwise never defined than by 
 their relation to the events of the sentient subject, of the body itself,
 
 xxvi CONTENTS. 
 
 PAGE 
 
 or of another body Among these powers there are some to which the 
 others are reducible Among these events, there is one, motion, which 
 may be substituted for the others Scientific Idea of body as of a 
 movable motor Scientific Idea of solidity, vacuum, line, surface, 
 volume, force, defined with relation to motion The elements of all 
 these ideas are never anything more than sensations, and more or less 
 elaborate extracts from sensation 274 
 
 VII. Correction applied to theory Bodies are not only permanent possi- 
 bilities and necessities of sensation Process by which we attribute to 
 them motion Analogies and differences between this process and the 
 process by which we attribute to animated bodies sensations, images, 
 ideas, and volitions similar to our own 278 
 
 VIII. Summary Materials by whose assemblage the notion or conception 
 of a body is formed Animal portion of this conception Human por- 
 tion of this conception Employment of names Intervention of 
 metaphysical illusion First elements of the hallucinatory semblance 282 
 
 CHAPTER II. 
 
 EXTERNAL PERCEPTION AND THE EDUCATION OF THE SENSES. 
 
 I. We assign a locality to our sensations This operation is distinct from 
 sensations and requires a certain lapse of time to accomplish Experi- 
 ments of physiologists 285 
 
 II. Sensations of touch are not situated at the spot in which we place 
 them What is produced there is, in the normal state, a nervous dis- 
 turbance which is one of their antecedents Illusion of persons who 
 have lost limbs Observations and experiments of Mueller Diseases 
 and compressions of the nervous trunk Sensations wrongly localized 
 by paralytic persons insensible to pain Sensations wrongly localized 
 after autoplastic operations Experiments and observations of Weber 
 Law governing localization We situate our sensation at the spot in 
 which we have been accustomed to meet with its usual condition or 
 cause 286 
 
 HI. Consequences We situate our sensations of sound and color beyond 
 the limit our body Examples Alienation of our sensations of color 
 They seem to us a property of the colored bodies Mechanism of 
 this alienation Proof that color is nothing more than a sensation ex- 
 cited by a state of the retina Subjective colors Subjective sensation 
 of complementary colors Luminous figures arising from the com- 
 pression of the eye Sensation of light excited by the section of the 
 optic nerve Visual sensations produced by the prolonged or reflected 
 excitation of the visual centres Various applications of the law gov- 
 erning localization Part of exploring touch Case in which the 
 situation of the sensation remains vague Internal sensations Case
 
 CONTENTS. 
 
 in which the places assigned to the causes of two nervous disturbances 
 is the inverse of the places of the disturbances themselves Images are 
 inverted on the retina Two stages of localizing judgment Why it is 
 sensations of color and sound go through these two stages Why it is 
 sensations of contact, pressure, and taste go through the first only 
 Intermediate positions of sensations of smell and of heat Ambiguous 
 character of sensations of smell, heat, and cold which seem to us to be 
 partially sensations and partially properties of a body Summary 
 The localizing judgment is always false Its practical utility . . 292 
 
 IV. Elements of the localizing judgment Examples It is composed of 
 tactile and muscular images or visual images Tactile and muscular 
 Atlas We can ascertain its presence in the case of persons born blind 
 Case in which we can ascertain its presence in ourselves Examples 
 How this tactile and muscular chart performs its functions It is 
 primitive Visual Atlas It is ulterior The localization of a sensa- 
 tion is effected by the adjunction of the visual or tactile and muscular 
 images attached to the sensation In the case of instinct, this adjunc- 
 tion is spontaneous \Vith man, it is an acquisition of experience . 302 
 
 V. Differences of the two Atlases Spontaneous formation of the tactile 
 and muscular atlas Derived formation of the visual atlas Primitive 
 localization of visual sensations Crude sensations of the retina W r hat 
 is added to them by the education of the eye Observations made on 
 persons born blind and restored to sight by an operation Cases 
 recorded by Cheselden, Ware, Home, Wardrop, and Nunneley 
 To the retinal and muscular sensations of the eye is added the image 
 of the muscular sensations of transport and locomotion of the limbs 
 and whole body This association is an effect of experience Opinion 
 of Helmholtz The retinal and muscular sensations of the eye become 
 abbreviatory signs Analogy between these sensations and names 
 They are, like names, substitutes of images Usually, these images 
 remain in a latent state and cannot be distinguished by consciousness 
 Comparative process by which we estimate great distances We 
 then compare signs only 305 
 
 VI. First notion of visible extension A very short series of muscular and 
 retinal sensations of the eye is the substitute of a very long series of 
 tactile and muscular sensations of the body and limbs Manner in 
 which persons born blind imagine extension How is it that we be- 
 lieve that we perceive by sight a great number of distant and co-exist- 
 ing points The visual atlas is an abbreviatory summary of the tactile 
 and muscular atlas Greater convenience and almost exclusive em- 
 ployment of the visual atlas Circumstances in which the tactile and 
 muscular atlas is still employed It remains atrophied and rudimen- 
 tary, through the predominance of the other Case in which the other 
 cannot develop itself Perfection of touch in blind persons Instances 319 
 
 VII. Consequences of the situation our sensations appear to have They 
 appear extended and continuous Consequently, the bodies which we
 
 xxviii CONTENTS. 
 
 PAGE 
 
 know by means of them appear extended and continuous How far 
 this belief is misleading The idea of extension is not innate but ac- 
 quired Idea of our body Corporal enclosure of the Ego Idea of an 
 external body We conceive it, with reference to our localized sensa- 
 tions, as a thing beyond it : and, with reference to our body, as a 
 thing without it Projection of sensations of sight and hearing into 
 this outer world Their definitive alienation Completion of the in- 
 ternal semblance which at present constitutes for us an external per- 
 ception Why it appears as other than ourselves, and without us . 327 
 
 VIII. How far this hallucination is true in the normal state Our illusion 
 is equivalent to a cognition What there is of truth in the localizing 
 judgment At the spot in which the sensations of the first group ap- 
 pear situated is found situated the starting point of the nervous dis- 
 turbance At the spot in which the sensations of the second group ap- 
 pear situated is found situated the starting point of the undulation of 
 air or ether What there is of truth in the external perception To 
 the differences which distinguish the sensations of the second group 
 correspond differences in the type of the undulations and in the char- 
 acters of their starting points To the corporal substance we pro- 
 nounce permanent there correspond a permanent possibility and ne- 
 cessity of sensations, and, in general, of events Every external per- 
 ception is reduced to the assertion of a general fact conceived with its 
 conditions Usual accordance of the real and mental law General 
 adaptation of the internal order to the external order Spontaneous 
 establishment, progressive perfection, very simple mechanism of this 
 adaptation 331 
 
 BOOK III. 
 
 THE KNOWLEDGE OF MIND. 
 
 CHAPTER I. 
 
 THE KNOWLEDGE OF MIND. 
 
 I. Part of the Idea of Self in mental life Its almost incessant presence 
 The Ego compared with its events 338 
 
 II. Ideas of which the Idea of the Ego is composed Among other ideas it 
 comprises that of a permanent being connected with a certain organized 
 b oc jy What we mean by this connection More precise ideas of 
 which the Idea of the Ego is composed Idea of a group of capacities 
 or faculties 339
 
 CONTENTS. xxbc 
 
 PAOK 
 
 III. What we understand by the words capacity and faculty They only 
 denote the possibility of certain events under certain conditions and 
 the necessity of the same events under the same conditions, with the 
 addition of a complementary one These possibilities and necessities 
 are permanent Capital importance which we attach to them Meta- 
 physical illusion which their name excites The only real elements of 
 our being are our events 340 
 
 IV. The distinctive character common to all these events is to appear as 
 internal Examples Mechanism of the rectification Every repre- 
 sentation, conception, or idea, at its second moment, is compelled to 
 appear as internal Our emotions and volitions are but the affective 
 and active side of our ideas Hence it follows that they also must 
 appear as internal The sensations which we localize in our bodies ap- 
 pear as internal The sensations which we localize outside our bodies 
 appear as events foreign to us, or as properties of bodies foreign to us. 342 
 
 V. Our past as well as our present events appear internal The series 
 of these events appears as a chain Mechanism of memory which binds 
 them together link by link By the law of the revival of images, the 
 image of one of our events calls up those of the preceding and follow- 
 ing one Abbreviatory process by which we quickly ascend or descend 
 long distances in the whole series Examples Prominent points in 
 our past life We leap from prominence to prominence Effect of 
 this rapid survey Disengagement of a character common to all the 
 successive elements of the series Idea of a stable -within This idea 
 is the idea of Self Completion of this idea by that of permanent fac- 
 ulties and capacities Final opposition of the Ego and its events . 345 
 
 VI. To what real compound the idea of Self actually corresponds It is 
 the product of a long and complex elaboration Preliminary opera- 
 tions required to form it It is, therefore, susceptible of error Various 
 classes of errors with respect to self Case in which external events 
 are introduced into the idea of self Various examples Starting 
 point of the illusion In novelists In uncultivated minds In dreams 
 With madmen In hypnotism Case in which events appertaining 
 to self are attributed to another formal alienation of sensations of 
 sound and color Psychical hallucinations Intellectual conversations 
 of mystics Story of Blake Other examples Starting point and pro- 
 gress of the illusion Passage from the psychical to the sensorial hal- 
 lucination Case in which the whole series of our past, present, and 
 possible events is replaced by an external series Starting point of the 
 illusion Suggestions in hypnotism Experiments of Drs. Tuke and 
 Elliotson Examples among monomaniacs Patients persuaded that 
 they are some person other than themselves, that they are changed into 
 animals or into inanimate bodies, that they are dead Analogous be- 
 liefs in dreams Mechanism of the idea of self in the normal state 
 Mechanism of the idea of self in the abnormal state Analogy be- 
 tween the mental and the vital process 349
 
 xxx CONTENTS. 
 
 PAOK 
 
 VII. General veracity of recollection Given the mechanism of recollection 
 its play is usually sure To the clear and circumscribed present image, 
 there almost invariably corresponds an antecedent sensation of which 
 the image is the remnant To the apparent position of the driven 
 back image there almost invariably corresponds the real position of 
 the antecedent sensation General veracity of the notion we have of our 
 faculties Incessant experience controls, rectifies, and consolidates it 
 Cohesion of its elements Exceptional circumstances must occur in 
 order to disjoin these elements or to insert foreign ones among them 
 General reason for the agreement of our thoughts and things . . 360 
 
 VIII. How, from the idea of our own mind, we form the fdea of other minds 
 Analogy of other living bodies and our own This analogy suggests 
 to us by association the idea of a mind similar to our own Various, 
 numerous, and constant verification of this spontaneous induction. 363 
 
 IX. General summary and connected view In all the preceding opera- 
 tions, an image or group of images is consolidated with a sensation or 
 a group of sensations, with an image or a group of images, by virtue 
 of the laws of the revival and association of images Increasing 
 complication of the mental compound Enormous complication 
 of the compound which constitutes the idea of an individual 
 Every mental compound is a couple and, in this respect, a cog- 
 nition When the first term of the couple is repeated by the pres- 
 ent sensation, the second term becomes a prevision Mechanism of 
 the prevision and projection of the second term into the future In 
 the majority of instances, our prevision agrees with the foreseen event 
 Usual correspondence of the mental with the real law Two states 
 of the mental couple It acts before being distinguished Opposition 
 of animal to human thought Passage from the first to the second 
 After ideas of individual things, rise ideas of general things . . . 365
 
 ./ 
 
 CONTENTS. xxxi 
 
 BOOK IV. 
 
 THE KNOWLEDGE OF GENERAL THINGS. 
 CHAPTER I. 
 
 OF GENERAL CHARACTERS AND GENERAL IDEAS. PAGE 
 
 General characters Examples They are the object of general 
 ideas 371 
 
 i. General Ideas which are Copies. 
 
 I. Part of general characters in nature A group of general characters 
 common to all the moments of a series of events constitutes the indi- 
 vidual A group of general characters common to many individuals 
 constitutes the class General characters are the fixed and uniform por- 
 tion of existence They are not pure conceptions or fictions of our 
 mind Their effectiveness in nature They are more or less general 
 The more general they are, the more abstract they are 372 
 
 II. To these general extracts, general and abstract ideas correspond in 
 our minds These ideas are names usually accompanied by a vague sen- 
 sible representation Examples The sensible representation is a 
 residue of many blunted and confounded recollections The name is 
 a significant sound, that is to say a sound connected with that which 
 all the sensible perceptions and representations of the individuals of 
 the class have in common, and connected with that alone In this 
 respect it is the mental representative of their common portion and be- 
 comes a general idea Mechanism of this exclusive connection Ob- 
 servations on children Analogy of infantile and scientific invention 
 In what human intelligence is distinguished from animal intelli- 
 gence How, in the child, transmitted names become significant 
 words Indications furnished by its barbarisms Observations of Dr. 
 Lieber The child receives words, but creates their meanings . . 376 
 
 III. Gradual adaptation of general ideas to things Scientific research 
 To the general characters whose group constitutes a class we add 
 others This addition has no limit Corrections afforded by these ad- 
 ditions to the general idea Instances in zoology and chemistry Per- 
 fectionment of our classifications 382 
 
 IV. General characters appertaining to the elements of the classified indi- 
 viduals Idea of the leaf in botany Idea of the anatomical plan in 
 zoology Idea of electric action Idea of gravitation Disengagement
 
 ;xii CONTENTS. 
 
 PAGE 
 
 of the most universal and most stable characters Retrenchment of 
 accessory and transient characters Summary The general idea is 
 adjusted to its object, first by addition, then by subtraction . . . 385 
 
 2. General Ideas which are Models. 
 
 I. General Ideas whose objects are possible only We construct such 
 ideas Ideas of Arithmetic Notion of Unity The property of being 
 a unit is nothing more than the aptitude of entering as an element 
 into a collection All facts or individuals present this property We 
 isolate it by means of a sign which becomes its mental representative 
 Successive inventions of different kinds of signs to represent the series 
 of abstract units First forms of calculation The ten fingers Peb- 
 bles Addition and subtraction by means of the fingers and pebbles 
 Names of number, substitutes for fingers and pebbles Convenience, 
 small number and simple combinations of these new substitutes 
 Final substitutes, ciphers They are the most abbreviatory of all 
 We thus form collections of mental units without thinking of adapting 
 them to collections of real units Subsequently and through experi- 
 ence, every collection of real units finds itself adapted to a collection 
 of mental units Examples Our numbers are preliminary outlines. 388 
 
 II. All the general ideas we construct are preliminary outlines Ideas of 
 geometry Notions of the surface, the line, and the point Their 
 origin The surface is the limit of the sensible body, the line is the 
 limit of the surface, the point is the limit of the line Convenient sym- 
 bols by which we represent these general characters Surface of the 
 board or paper, lines and points in ink or chalk Analogy between 
 these substitutes and the fingers or pebbles in arithmetic Last gen- 
 eral idea introduced into geometry, the idea of motion Its origin 
 New aspect it gives to the primary ideas of geometry The line is the 
 continuous series of the successive positions of the point in motion 
 The surface is the continuous series of the successive positions of the 
 line in motion The solid is the continuous series of the successive 
 positions of the surface in motion If for the point, line and surface, 
 we substitute their symbols, these constructions become sensible 
 Other constructions The straight line The broken line The curved 
 line The angle The right angle The perpendicular The polygon 
 The circumference The plane The three solids of revolution 
 The sections of the cone Indefinite number of these constructions 
 To the most general of these mental constructions there are real con- 
 structions which correspond There are in nature, surfaces, lines, and 
 points, at least so far as our senses are concerned There are in 
 nature, surfaces, lines, and points in motion To the least general of 
 these constructions there are real constructions which approximately 
 correspond Why this correspondence is approximate only Exam- 
 ples The real construction is more complex than the mental con-
 
 CONTENTS. xxxiii 
 
 PAGE 
 
 struction The two constructions become mutually adjusted by the 
 complication of the one and the simplification of the other Utility of 
 preliminary outlines 393 
 
 III. Ideas of mechanics Notions of rest, motion, velocity, force, mass 
 Their origin and their formation Lines, ciphers, and names are 
 their symbols Diversity and indefinite number of the compounds 
 constructed with these elements To the most simple of these mental 
 constructions there are real constructions which correspond Tenden- 
 cies of bodies at rest or possessed of a uniform rectilinear motion to 
 persevere indefinitely in their state To such of these mental con- 
 structions as are less simple there are also certain real constructions 
 which correspond Hypothesis of uniformly accelerated velocity ; case 
 of heavy bodies which fall A movable body acted on by a uniform 
 rectilinear movement and by another movement wh6se velocity is 
 uniformly accelerated ; case of the planets How preliminary out- 
 lines must be constructed to have a chance of agreeing with things 
 Three conditions Their elements must be fashioned in accordance 
 with the elements of things Their elements must be the most general 
 possible Their elements must be combined as simply as possible. 397 
 
 IV. Other mental constructions We may form such for all classes of ob- 
 jects Physical and Chemical hypothesis Among these outlines there 
 l dre some to which we are desirous that things should conform Men- 
 tal Construction of the Useful, the Beautiful, and the Good These 
 outlines, so constructed, become springs of action 401 
 
 CHAPTER II. 
 
 THE COUPLES OF GENERAL CHARACTERS AND GENERAL PROPOSITIONS. 
 
 I. General characters form couples Two general characters coupled to- 
 gether form a law To conceive a law, is mentally to enounce a gen- 
 eral proposition . . 403 
 
 II. Examples of these coupled characters Practical utility of their connec- 
 tions These connections are of various kinds Unilateral or simple 
 connections Bilateral or double connections The two characters 
 may be simultaneous They may be successive Antecedent and con- 
 sequent Frequency of this last case The antecedent then takes the 
 name of cause 403 
 
 III. In what the connection consists Stuart Mill's analysis The word 
 Cause does not denote any secret and mysterious virtue comprised in 
 the first character Its precise meaning Given the first character, 
 that is enough for the second to be also given There is nothing 
 strange in general characters having, like particular facts, antecedents,
 
 CONTENTS. 
 
 companions, and consequents The difficulty is, to isolate the general 
 characters Two artifices of method for evading the difficulty Two 
 kinds of Laws 406 
 
 i. Laws concerning Real Things. 
 
 I. First general judgments of the infant Mechanism of their formation 
 Passage from animal judgment to human judgment General judgments 
 become multiplied They are the summary and measure of anterior 
 experience How subsequent experience rectifies them Gradual adap- 
 tation of our couples of mental characters to the couples of real char- 
 acters We believe at present that every general character is connec- 
 ted with another Provisional admission of this hypothesis It is the 
 principle of Scientific Induction 409 
 
 II. Various methods of Scientific Induction When a known character is 
 given, this is sufficient to give another character which was unknown 
 Search for the unknown character from this indication Method of 
 Agreement Method of Difference Method of concomitant varia- 
 tions Various examples All these methods are processes of elim- 
 ination They are efficient in proportion to the magnitude of 
 the eliminations they effect When the elimination is complete, 
 the residue contains the unknown character of which we are in 
 search Complementary Method of Deduction Example Theory of 
 Herschel and Mill Example of these various methods in the inquiry 
 into the antecedent of dew 412 
 
 2. Laws concerning Possible Things. 
 
 I. Lengthiness of the processes described above Laws thus discovered 
 are probable only beyond the circle of our experience The most gen- 
 eral are last discovered 426 
 
 II. Propositions concerning possible things are different in character 
 Universal truth of mathematical theories We cannot conceive an in- 
 stance in which these propositions are false The most general are 
 formed first Among the most general, there are some called axioms, 
 on which the others depend, and which we admit without demonstra- 
 tion 426 
 
 III. Two kinds of proof for the theorems of the so-called Sciences of Con- 
 struction Example Difference of the two methods of proof Axioms 
 are unproved theorems They are analytical propositions We either 
 dispense with their demonstration because the analysis required is 
 very easy, or evade their demonstration because the analysis required 
 is very difficult Axioms of identity and contradiction Axiom of the 
 alternative Analysis demonstrating it Latent ideas contained in the 
 two members of the proposition expressing it These undisengaged 
 ideas determine our conviction There are latent and proving ideas 
 of the same kind in the terms of the other axioms 428
 
 CONTENTS. xxxv 
 
 PAGB 
 
 IV. Mathematical axioms Axioms as to equal quantities augmented or 
 diminished by equal quantities Experimental and inductive proof 
 Analytical and deductive proof Case of artificial magnitudes or col- 
 lections of natural units Two of these collections are equal when 
 they contain the same number of units Case of natural magnitudes 
 or collections of artificial units Two of these magnitudes are equal 
 when they coincide and are confounded in one same magnitude 
 Disengagement of the idea of identity included and latent in the idea 
 of equality 43 2 
 
 V. Principal geometrical axioms Axioms concerning the straight line 
 Definition of the straight line Propositions derived from it Two 
 straight lines' having two points in common coincide in all their in- 
 termediate, and in all their ulterior extent Axioms relating to paral- 
 lel lines Definition of parallel lines Propositions derived from it 
 Two lines perpendicular to the same straight line are equi-distant 
 throughout Examination of Euclid's Postulate 438 
 
 VI. Underlying mental process which accompanies the experience of the 
 eyes and imagination This process consists in the silent recognition 
 of a latent identity The experience of the eyes and imagination is 
 nothing more than a preliminary indication and a subsequent confirm- 
 ation Its utility Case in which this indication and this confirmation 
 are wanting Axioms of mechanics Their late discovery Ordinary 
 experience does not suggest them How scientific experience discov- 
 ered them Opinion which places them among truths of experience 
 Many of them are, in addition to this, analytical propositions Prin- 
 ciple of Inertia Exact enunciation of the axiom The difference of 
 place and moment is, by hypothesis, without influence or of no effect 
 Limits of the axiom thus extended and demonstrated Principle of 
 the parallelogram of velocities and of forces Exact enunciation of 
 the axiom The co-existence of a second movement in the same mov- 
 able body is, by hypothesis, without influence or of no effect Passage 
 from the idea of velocity to that of force 446 
 
 VII. Axioms relating to Time and Space Mathematical Idea of Time and 
 Space Every determinate duration or extension has something be- 
 yond it Analysis of this conception Every determinate magnitude, 
 artificial or natural, has in the same way something beyond it, and is 
 found comprised in an infinite series Examples A number A 
 straight line Demonstration of the axiom It is an analytical propo- 
 sition Every addition effected implies an addition that may be ef- 
 fected Discovery of the ideas of identity and indifference included 
 and latent in the terms of the axiom All the axioms we have exam- 
 ined are analytical propositions more or less disguised 453 
 
 VIII. Importance of the question Origin, formation, and value of axioms 
 and the theories derived from them Opinion of Kant Opinion of 
 Stuart Mill Conclusions of Kant and Stuart Mill on the range of the 
 human mind and on the nature of things Proposed theory What it
 
 CONTENTS. 
 
 PAGE 
 
 concedes and denies in the two preceding theories There is an in- 
 trinsic and necessary connection between the two ideas whose couple 
 forms a theorem There is an intrinsic and necessary connection be- 
 tween the two general characters which correspond to these two ideas 
 It remains for us to know whether these general characters are actu- 
 ally met with in things They are met with wherever the theorems 
 are applicable 456 
 
 CHAPTER III. 
 
 THE CONNECTION OF GENERAL CHARACTERS, OR THE EXPLANATORY REASON 
 
 OF THINGS. 
 
 i. Nature of the Explanatory Intermediate. 
 
 I. In many cases the connection of two data is explained What is asked 
 by the word why Intermediate and explanatory datum which, being 
 connected to the first and the second, connects the second to the first 
 Premises, conclusion, reasoning 462 
 
 II. Propositions in which the first datum is an individual Examples In 
 this case the intermediate is a character more general than the indi- 
 vidual and comprised in it Propositions in which the first datum is 
 a general thing This the case with laws The intermediate is then 
 the reason of the law Successive discoveries which have determined 
 the reason of the fall of bodies Here again the explanatory inter- 
 mediate is a more general and more abstract character included in 
 the first datum of the law Present hypothesis of physicists on the ex- 
 planatory reason of gravitation Same conclusion 462 
 
 III. Laws in which the explanatory intermediate is a transient character 
 communicated to the antecedent by its surroundings Law connect- 
 ing the sensation of sound with the vibration transmitted from an 
 external body Same conclusion as in the preceding case The inter- 
 mediate is then a series of successive general characters .... 465 
 
 IV. Laws in which the intermediate is a sum of simultaneous general 
 characters Of the composition of causes Law of the motion of a 
 planet Law in which the first datum is a sum of separable data 
 Examples in arithmetic and geometry In this case the intermediate 
 is a general character repeated in all the elements of the first datum 
 Example in zoology Law of the connection of organs The inter- 
 mediate repeated in each organ is the property of being useful These 
 kinds of intermediates are the most instructive Summary The ex- 
 planatory reason of a law is a general intermediate character, simple 
 or multiple, included directly or indirectly in the first datum of the 
 law . , 467
 
 CONTENTS. xxxvii 
 
 PAGE 
 
 V. Of explanation and demonstration The first datum contains the in- 
 termediate which contains the second datum Hence three connected 
 propositions Order of these propositions In what the scientific 
 syllogism consists 472 
 
 2. Methods of finding the Explanatory Intermediate. 
 
 I. The position and characters discovered in the intermediate afford the 
 means of finding it Method in the sciences of construction Advan- 
 tages they have over the sciences of experience The intermediate is 
 always included in the definition of the first datum of the law We 
 may always derive it thence by analysis Example, the demonstration 
 of axioms Other examples Theorem of the equality of the opposite 
 sides of the parallelogram How intermediates enclose one another 
 In what the skill and labor of the geometrician consist Method he 
 follows in his constructions The more complex compounds have 
 simpler factors The properties of these simpler factors are the inter- 
 mediates by which the more complex compounds possess their proper- 
 ties The last intermediate is always a property of the primitive 
 factors This property is the ultimate reason of the mathematical law 
 Place of axioms They enounce those properties of the factors or 
 primitive elements which are the simplest and most general of all 
 Analysis must apply, then, to the primitive elements Primitive ele- 
 ments of the line Discovery of a character common to all the elements 
 or points of a line Definition of a line by the constant ratio of its 
 co-ordinates Analytical Geometry Primitive elements of a magni- 
 tude The infinitesimal calculus In every law enounced by a science 
 of construction, the ultimate reason of the law is a general character 
 included in the elements of the first datum of the law 474 
 
 II. Method in the experimental Sciences Their disadvantages Insuffi- 
 ciency of analysis Why we are compelled to employ experience and 
 induction Law connecting dew with cooling Included intermedi- 
 ates connecting the second datum of this law to the first The method 
 of discovering the intermediate differs, according as it is a question 
 of real or mental compounds, but the connection of the second datum 
 and of the first is formed in the same way Very advanced experi- 
 mental sciences Analogy of these sciences and of the mathematical 
 sciences Their most general laws correspond to axioms They 
 enounce, like axioms, properties of primitive factors How far these 
 laws still differ from axioms They are provisionally irreducible. . 482 
 
 III. Same arrangement in the less advanced experimental Sciences Their 
 most general laws also enounce properties of primitive factors Sci- 
 ences in which the primitive factors may be observed Zoology 
 General characters of organs Cuvier's law Geoffroy Saint-Hilaire's 
 law History General characters of the individuals of an epoch, of a 
 nation, or of a race Psychology General characters of the elements 
 of knowledge All these general characters are explanatory interme-
 
 CONTENTS. 
 
 diates They are the more explanatory in proportion as they apper- 
 tain to more general and more simple primitive factors Explanation 
 is at an end when we arrive at primitive factors which we can neither 
 observe nor conjecture Present limits of physiology, physics, and 
 chemistry Beyond known factors the simpler unknown factors may 
 have either different or the same properties According as one or the 
 other of these hypotheses is true, the explanation has or has not 
 limits 487 
 
 IV. Another disadvantage of the experimental Sciences They have to 
 answer to questions of origin Historical portion of every experimen- 
 tal science Laplace's hypothesis Researches of mineralogists and 
 geologists Darwin's Ideas Views of historians General Theory of 
 Evolution Gaps Daily progress which fills them up The formation 
 of a compound is explained by the properties of its elements and by 
 the characters of the antecedent circumstances The explanatory in- 
 termediate is the same in this and in the preceding cases . . . 493 
 
 3. If every Fact or Law has its Explanatory Reason. 
 
 I. Convergence of all the preceding conclusions They indicate that, in 
 every couple of actually connected events, there is an explanatory in- 
 termediate which necessitates this connection At all events we be- 
 lieve that it is so We predict, by analogy, the characters of the inter- 
 mediate in the cases in which it is still unknown to us Examples 
 We extend this law by analogy to all points of space and all moments 
 of time 498 
 
 ' II. Groundwork of this induction From our ignorance in certain cases 
 of the explanatory reason, we cannot conclude that it does not then 
 exist The cause of our ignorance is known to us The gaps of sci- 
 ence are explained by its conditions Examples To presume the ab- 
 sence of the explanatory reason is a gratuitous hypothesis The pre- 
 sumptions are in favor of the presence of an explanatory reason of 
 which we are ignorant Other presumptions suggested by the exam- 
 ple of the sciences of construction In these sciences, every law has its 
 known explanatory reason The gaps of the experimental sciences are 
 caused by their conditions and by the particular turn of their method 
 Proof What geometry would be if formed by induction The gaps 
 of geometry would then be the same as those of physics or chemistry 
 The Sciences of Construction are a preliminary model of that which 
 the experimental sciences might be Analogy of their arrangements 
 Identity of the materials The only difference between our mental 
 and real compounds is, that the first are the more simple Employ- 
 ment of mental compounds in order to understand real compounds 
 Consequences The application of mathematical and mechanical laws 
 is universal and necessary Refutation of Stuart Mill All numbers, 
 forms, movements, and forces of physical nature are subject to neces- 
 sary laws Very probably, all the physical changes in the world, and
 
 CONTENTS. xxxix 
 
 PAGE 
 
 probably all the physical changes beyond our world, are reducible to 
 movements which have movements for their conditions Idea of the 
 physical universe as a collection of movable motors subject to the law 
 of the Conservation of Force 500 
 
 III. Recapitulation of the inductive proofs which make us believe in the 
 principle of the Explanatory Reason Our natural inclination to ad- 
 mit it Employment made of it by scientific men for the purpose of 
 induction Opinion of Claude Bernard Opinion of Helmholtz Ex- 
 planation of this belief by the innate structure of our mind Another 
 explanation Analogy of this principle and of the axioms previously 
 demonstrated It is probable that, like them, it may be demonstrated 
 by analysis Demonstration Latent identity of the terms enouncing 
 it Limits of the axiom so demonstrated and understood The axiom 
 of Cause is derived from it Consequences of the axiom of explanatory 
 reason The intervention of experience is necessary in order that it 
 may be applied Possible application of the axiom to the problem of 
 existence General Summary of the present psychological theory . . 507 
 
 END OF THE TABLE OF CONTENTS.
 
 LIBRARY 
 
 ON INTELLIGENCE 
 
 PAET THE FiKST. 
 THE ELEMENTS OF KNOWLEDGE. 
 
 BOOK I. 
 
 OF SIGNS. 
 
 CHAPTER I. 
 
 OF SIGNS IN GENERAL AND OF SUBSTITUTION. 
 
 I. IF we ascend the Arc de 1'Etoile, and look down on the 
 Champs Elysees, we see a number of black or variously colored 
 specks stirring about on the roadway or pavements. That is 
 all our eyes distinguish. But we know that each of these specks 
 is a living body, with active limbs, a wise economy of organs, 
 and a thinking brain actuated by some project oh inward desire 
 in short, is a human being. The presence of the specks has 
 indicated the presence of persons. The first have been signs of 
 the second. 
 
 Associations of this kind are continually being met with. 
 At night we look up to the starry sky, and say to ourselves 
 that each of these brilliant points is an enormous mass like the 
 sun. When we walk in the fields on an autumn evening, we 
 see the blue smoke rising calmly in the distance, and think at 
 once of the slow fires with which the peasants, are burning up 
 the stubble. We turn over sheets of music, and, while the eye 
 follows the black and white marks with which the lines are dot- 
 ted, we hear mentally the sounds they indicate. A sharp cry 
 of a particular tone comes from a neighboring room, and we pic- 
 ture to ourselves the face of a child, crying no doubt because 
 1
 
 2 OF SIGNS. [BOOK I. 
 
 he has hurt himself. The greater part of our ordinary judg- 
 ments are made up of connections like these. When we drink 
 or walk, or use our limbs for any purpose, we foresee, by means 
 of a perceived fact, a fact which we do not yet perceive ; animals 
 do the same; according to the color or smell of an object, they 
 eat or leave it. In all these cases a present experience suggests 
 the idea of another possible experience ; from the first we im- 
 agine the second ; the perception of an event, object, or char- 
 acter, arouses the conception of another event, object, or char- 
 acter. When we touch the first link of the couple we picture to 
 ourselves the second link, and the first is the sign of the second. 
 
 II. In this great family of signs there is one species whose 
 properties are remarkable ; these are names, 
 
 Let us first consider proper names, which are the easier to 
 study from each one denoting some particular, precise thing ; 
 as, for example, the names Tuileries, Lord Palmerston, Luxem- 
 bourg, Notre Dame, etc. These clearly belong to the family we 
 have just described, and each of them is the sensible and ap- 
 parent first term of a couple. When I hear the word Lord 
 Palmerston pronounced, or read the fourteen letters of which 
 it is made up, I form a mental image of his brisk erect figure, 
 gesticulation, and smile, just as I have seen him in his place in 
 Parliament. Again, when I read or hear the word Tuileries, I 
 picture more or less vaguely, in more or less mutilated forms, a 
 level garden, flower-beds enclosed with rails, marble statues, the 
 rounded heads of chestnut-trees, the fall and plume of a foun- 
 tain, and the rest. A short insignificant sensation, acting 
 through our eyes or ears, has the property of calling up in us a 
 certain image, or series of images, more or less definite, and 
 the connection between the first and second terms of this coup- 
 le is so precise, that in a hundred million instances, and for 
 two millions of men, the first term invariably calls up the 
 second. 
 
 III. Suppose now that instead of dwelling on the word Tuil- 
 eries, and calling up the different images connected with it, I 
 glance quickly at a phrase like this : " There are many public 
 gardens in Paris, both small and great, some no bigger than a 
 drawing-room, others as large as a park, the Jardin des Plantes, 
 the Luxembourg, the Bois de Boulogne, the Tuileries, Champs
 
 CHAP. I.] OF SIGNS IN GENERAL. 3 
 
 Elysees, the squares, besides the new parks which are being laid 
 out, all very neat and well looked after." I ask the ordinary 
 reader who has just gone through this list with ordinary speed, 
 if, when his eye ran over the word Tuileries, he saw mentally 
 as before, some fragmentary image, some patch of blue sky ap- 
 pearing through trees, the attitude of some statue, some vague- 
 ly extending avenue, the sparkling of water in a basin? Assur- 
 edly not, his eye ran over it too quickly ; there is a notable dif- 
 ference between this and the preceding operation. In the first, 
 the sign aroused pictures more or less faded of the sensation, 
 revivals more or less enfeebled of the experience ; in the second, 
 the sign did not arouse them. In the one case, the two links 
 of the couple appear; in the other, the first link alone appears. 
 Between these two operations are an infinite number of inter- 
 mediate states occupying the whole interval ; these states con- 
 nect the intense half-sight with the dry notation, by a series of 
 degradations, rubbings out, and losses, which strip by degrees 
 the complete and puissant image, till they leave us nothing but 
 a simple word. 
 
 This word so reduced is not however a lifeless symbol, with- 
 out trace of signification ; it is more like the trunk of a tree, 
 stripped indeed of its leaves and branches, but capable of repro- 
 ducing them ; we understand it as we pass it, and with whatever 
 speed we may pass it ; it does not come to us as a stranger, or 
 strike us as an intruder ; in its long association with the expe- 
 rience and image of the object, it has contracted certain affinities 
 and repugnances ; and in passing through us carries with it this 
 retinue of affinities and repugnances ; however briefly we retain 
 the word, the image to which it corresponds commences to 
 form ; the image accompanies the word in a nascent state, and, 
 though not actually formed, acts on us as if it were. Read, for 
 instance, a sentence like this: " London, the capital of Eng- 
 land, has several fine gardens Hyde Park, Regent's Park, and 
 the Tuileries." We experience a certain shock and surprise; 
 we point involuntarily in two directions, towards Paris and 
 towards a far distant city. The image of the Tuileries is 
 aroused with the Seine and quays beside it, and we are arrested, 
 when we try to transport them elsewhere. But before the 
 image appeared, we experienced a resistance in the word itself,
 
 4 OF SIGNS. [BOOK I. 
 
 a resistance which was strengthened and renewed when the 
 image reappeared. Prolong and vary the experiment ; you 
 will find in the word a system of tendencies all corresponding to 
 those of the image, all acquired by it in its connection with the 
 experience and the image, but now spontaneous, and acting, 
 sometimes to connect it with, sometimes to sever it from, other 
 words or groups of words, images or groups of images, experi- 
 ences or groups of experiences. In this way the simple name 
 is enabled to take the place of the image it arouses, and conse- 
 quently, of the experience it recalls ; it performs their office and 
 becomes their substitute. 
 
 IV. In the case we have considered, the obliteration of 
 the image forming the second member of the couple is, as gen- 
 erally happens with proper names, gradual and involuntary. 
 Let us consider another case, in which we suddenly and volun- 
 tarily suppress it ; the reader will then see the operation more 
 clearly set out. 
 
 My garden is surrounded by a hedge, and my fruit is stolen ; 
 I determine on enclosing it with a wall. I get what workmen 
 I can in the village four, for instance and at the end of the 
 day I find they have built twelve metres of wall. This is not 
 fast enough ; I send to the next village for six other workmen, 
 and ask myself how many metres a day will be added to the 
 wall. To find out this, I no longer picture to myself workmen 
 with their blouses and trowels the wall with its stones and 
 mortar, but replace my first workmen by the figure four, the 
 first amount of work by the figure twelve, the whole of the 
 workmen by the figure ten, the unknown amount of work they 
 will do by the sign x, and write down the following propor- 
 tion : 
 
 12 X 10 
 4 : 12 : : 10 x = = 30. 
 
 4 
 
 Henceforth, barring accident or drunkenness, if the new men 
 work like the old, and all continue to work together as the first 
 four began, my ten men will build thirty metres a day. Oper- 
 ations of this kind occur daily, and all practical calculations are 
 made in this way. For the real objects first imagined, figures 
 are substituted which replace them partially ; they replace them
 
 CHAP. I.] OF SIGNS IN GENERAL. 5 
 
 in the only point of view in which we need consider them, that 
 is, in point of number. This once effected, we forget the ob- 
 jects represented ; they recede into the background ; we only 
 consider the figures, we assemble, compare, transpose, and ma- 
 nipulate them as more convenient equivalents, and the figure 
 we finally arrive at indicates the object, or group of objects, at 
 which we wish to arrive. 
 
 Substitution goes further than this, and figures substituted 
 for things have in turn letters substituted for them. After sev- 
 eral similar calculations, I observe that in all such cases the 
 proportion is written in the same way, that the first figure al- 
 ways represents the first workmen ; the second, their work; the 
 third, the whole number of workmen ; the fourth, the unknown 
 work ; and thus I pass from arithmetic to algebra. Hence- 
 forth I replace the first figure by A, the second by B, the third 
 by C, and write down as follows : 
 
 BXC. 
 
 A : B : : C : x = 
 
 A. 
 
 And I see that, in every such case, if I want to know the 
 amount of work which will be done by all the workmen, it will 
 be sufficient to multiply their number by that representing the 
 work done by the first lot, and then to divide the product by 
 the number of the workmen first employed. 
 
 Instead of this simple case, let us consider the labor of an 
 analyst who writes equations by the hour. He lays aside the 
 figures, but indirectly he is working on them, just as an arith- 
 metician lays aside the facts, but works indirectly on the facts. 
 He effaces figures from his mind as the other effaces things. 
 Each of them arranges and combines signs, and these signs are 
 substitutes. The fact is, they are not like proper names, sub- 
 stituted for the whole of the object they represent, but merely 
 for a portion or an aspect of such object. The letter used in 
 algebra does not fully replace the arithmetical cipher with its 
 precise quantity, but only as regards its function and place in 
 the equation it enters into. The arithmetical cipher does not 
 fully replace the thing it stands for, with all its qualities and 
 characters, but only, as regards quantity and number. Each re- 
 places part only of the imagined object, that is to say, a frag-
 
 6 OF SIGNS. [BOOK I. 
 
 ment an extract ; the cipher a more complex extract ; the let- 
 ter a less complex one, that is to say, an extract from the first 
 extract. But the substitution, though partial, is none the less 
 actual. Two complete and infinitely fertile sciences depend 
 on it, and derive their efficacy from it. The reader must par- 
 don me for dwelling on simple remarks like these. In the for- 
 mation of couples, such that the first term of each suggests the 
 second term ; and, in the aptitude of this first term to stand, 
 wholly or partially, in place of \\\z second, so as to acquire, either 
 a definite set of its properties, or all those properties combined, 
 we have, I think, the first germ of the higher operations which 
 make up man's intelligence ; we shall now consider them in 
 detail.
 
 CHAP. II.] SIMPLE SUBSTITUTION. 
 
 CHAPTER II. 
 
 OF GENERAL IDEAS AND SIMPLE SUBSTITUTION. 
 
 I. NAMES, as we know, are divided into proper and com- 
 mon ; and these are correctly distinguished by saying that the 
 first, as Caesar, Tuileries, Cromwell, correspond to a single object ; 
 while the second, as tree, triangle, color, correspond to an indef- 
 inite group of objects. These last are the most numerous, and 
 the most in use in every individual mind ; there are thirty or 
 forty thousand of them in a language, and they make up of 
 themselves the whole dictionary. Further than this, they are 
 the most important ; by their aid we make classifications, judg- 
 ments, and reasonings, and pass, in short, from crude, loose expe- 
 rience to orderly complete knowledge. Let us consider them at- 
 tentively. We should attain a truth of capital importance, and 
 infinite in its consequences, could we determine, not as gram- 
 marians and logicians, but as psychologists, their true nature 
 and precise office. 
 
 Like all signs, and especially like all names, each one is the 
 first term of a couple, and draws with it a second term. But 
 this second term has remarkable characteristics, which distin- 
 guish it from all others, and give the name peculiar qualities. 
 Logicians and grammarians tell us rightly that a common 
 name, like tree or polygon, is a general or abstract name. It 
 is general because it corresponds to a class (genus) or group of 
 similar objects ; the name of tree to all trees, poplars, oaks, 
 cypress, birch, etc. ; the name of polygon to all polygons, tri- 
 angles, quadrilaterals, pentagons, hexagons, etc. It is abstract 
 because it denotes an extract, that is, a portion, of an individual, 
 and a portion which is found in every individual of the group ; 
 the name tree expresses the quality common to all kinds of 
 trees, poplars, oaks, cypress, birch, etc. ; that of polygons rep- 
 resents the quality common to all sorts of polygons, triangles,
 
 g OF SIGNS. [BOOK I. 
 
 quadrilaterals, pentagons, hexagons, etc. We see the connec- 
 tion between these two characters of a name ; it is general be- 
 cause it is abstract ; it corresponds to a whole class, because the 
 object it denotes, being but a fragment, may be found in all the 
 individuals of the class, which, similar in this point, remain, 
 nevertheless, dissimilar in other points. Here we have a couple 
 of a new kind, since its second term is not an object of which 
 we can have perception and experience, that is to say, an en- 
 tire and determined fact, but a portion of a fact, a fragment for- 
 cibly and artificially severed from the natural whole to which it 
 belongs, and without which it cannot subsist. 
 
 II. Can we have experience, perception, or sensible rep- 
 resentation of this detached and isolated fragment ? Assur- 
 edly not ; for that would be a contradiction. When I have seen 
 on the slate triangles, quadrilaterals, pentagons, hexagons, etc. ; 
 and, in contrast, beside them, circles and ellipses, and call the 
 first polygons, I have not mentally a sensible representation of 
 a pure or abstract polygon ; for the pure polygon is a figure with 
 several sides, but whose sides do not make up any particular 
 number ; hence all experience and sensible representation are 
 excluded ; for since the sides are many, they make such a num- 
 ber as three, four, five, six, etc. In saying many, we mean a 
 determined fixed number. To tell one to see or imagine many 
 sides, and at the same time not to see or imagine three, four, or 
 any definite number of sides, is, in one breath, to order and forbid 
 the same operation. Similarly, when having seen in the country 
 thirty different trees, oaks, lime trees, beach, and poplars I use 
 the word tree, I do not find in my mind a colored figure rep- 
 resentative of a tree in general ; for a tree in general has height, 
 trunk, leaves, etc., without having any particular height, trunk, 
 or leaves ; and it is impossible to represent to one's self size 
 and form, unless the size and form are of some kind or oth- 
 er that is to say, individual and precise. In fact, at the 
 word tree, especially if read slowly and attentively, there rises 
 in me a vague image so vague that I cannot for the moment 
 say whether it is a fir or an apple tree. And so in hearing the 
 word polygon, I trace in my mind, but very indistinctly, lines 
 cutting each other, and tending to enclose a space, without 
 knowing whether the figure in process of construction will turn
 
 CHAP. II.] SIMPLE SUBSTITUTION. g 
 
 out quadrilateral or a pentagon. But this uncertain image is 
 not the abstract tree, nor the abstract polygon ; the softness 
 of its outline does not hinder its having a particular outline ; 
 it is shifting and obscure, and the object denoted by the name is 
 neither shifting nor obscure ; it is a very precise extract, and 
 can often be defined exactly. We can express with rigorous 
 exactness what constitutes a triangle, and, almost as exactly, 
 what constitutes an animal. The triangle is a figure enclosed by 
 three lines, which cut each other in pairs, and not that undecided 
 image, on a dusky or whitish ground, with angles more or less 
 acute, which shifts continually, becoming at will scalene, or 
 isosceles, or right angled. The animal is an organized body 
 which is nourished, reproduces its species, feels, and moves, and 
 not that formless and varying thing, changing from vertebrate 
 to articulate or to mollusc, and only emerging from its indis- 
 tinctness when it takes the color, size, and structure of an in- 
 dividual. 
 
 Thus we find a wide gulf between the vague and shifting 
 image which the name suggests, and the precise and fixed ex- 
 tract which the name denotes. The reader may convince 
 himself of this by considering the word myriagon and its mean- 
 ing. A myriagon is a polygon with ten thousand sides. It is 
 impossible to imagine such a thing even when definite and 
 special, much less when general and abstract. However lucid 
 and comprehensive may be the mind's view, after five or six, 
 twenty or thirty lines drawn out consecutively with great dif- 
 ficulty, the image becomes confused and indistinct ; and yet my 
 conception of a myriagon has nothing confused or indistinct 
 about it. What I conceive, is not a myriagon like this, in- 
 complete and tumbling to pieces, but a complete myriagon all 
 whose parts co-exist simultaneously ; I can hardly imagine the 
 first, but can readily conceive the second. What I conceive 
 then, differs from what I imagine ; and my conception is not the 
 same thing as the shifting figure which accompanies it. But, on 
 the other hand, this conception exists ; there is something in me 
 representing the myriagon, and corresponding to it exactly. 
 In what then does this internal representative this exact cor- 
 respondent consist ? and what passes within me when I hear 
 a general name, and, by means of it, think of a quality common
 
 IO OF SIGNS. [BOOK I. 
 
 to many individuals of a general thing in short, of an abstract 
 character ? 
 
 III. To answer this, let us consider in order several cases 
 in which, when we have gone through a series of similar objects, 
 we have mentally extracted from them a quality, or general 
 character, which we denote by an abstract name. The reader 
 has no doubt visited galleries of pictures arranged in schools ; 
 if we walk for a couple of hours among the works of Titian, 
 Tintoret, Giorgione, and Veronese, and on leaving seat our- 
 selves on a bench, and close our eyes, we experience reminis- 
 cences of what we have seen ; we see again inwardly such and 
 such a fair or rosy half-bending figure, some grand old man ma- 
 jestically draped in silken robes, strings of pearls on naked arms, 
 chestnut hair curling over a snowy neck, colonnades of veined 
 marble rising against a blue sky, here and there the sprightly 
 figure of a little girl, the smile of a goddess, the ample propor- 
 tions of a smooth shoulder, the blaze of red hangings against a 
 green background ; in short, a hundred partial and disorderly 
 revivals of what we have just seen. If, at this moment, we 
 seek for the dominant character ruling in this various world, 
 we find nothing ; we feel indeed that it is beautiful, but do not 
 yerMistinguish in what the beauty lies; we are acted on by 
 twenty different tendencies which rise and as quickly fade ; we 
 attempt such expressions as voluptuous, rich, facile, luxuriant ; 
 they are not suitable, or but partially so. We then begin again 
 by dividing our inquiries, we pass by turns in review landscapes, 
 architecture, dress, types, expressions, attitudes, coloring; we 
 find for each of these fragments some principal and striking 
 trait, we attempt to note them in passing by a familiar or ex- 
 aggerated word, then, collecting all these summaries we try to 
 summarize them further in some abbreviative phrase which 
 may serve as a focus for all these dispersed rays. We approach 
 our object, and at last a definitive, or nearly definitive, tendency 
 is disengaged. It appears, in words, by such expressions as ex- 
 pansiveness, happiness, noble pleasure ; while our inner sight 
 has at the same moment seized on some corresponding image, 
 an opening flower, a smiling face, a bending unconstrained form, 
 the rich and full harmony of sweet-toned instruments, the breath 
 of perfumed air in the country ; here are expressive compari-
 
 CHAP. II.] SIMPLE SUBSTITUTION. ! x 
 
 sons and metaphors, that is to say, sensible representations, 
 special recollections, revived sensations, all analogous in tone 
 and character to what we have just experienced. They are 
 effects and expressions of the final tendency which has been 
 formed. In the case of an artist, the formation, disengagement, 
 and effects of the tendency are plainer still. The whole body 
 speaks ; often, if at a loss for a word, a gesture expresses the 
 meaning ; a grimace, a start, an imitative noise, becomes a sign 
 in place of a name ; to represent an avenue of old oaks, the 
 stature becomes erect, the feet are planted firmly on the ground, 
 the arms extend stiffly, or form sharp angles at the elbows ; to 
 represent a cluster of honeysuckle or ivy, the stretched-out 
 fingers trace arabesques in the air, while the muscles of the face 
 assume changing folds. This mimicry is natural language, and 
 with some habit of internal observation you guess the corre- 
 sponding mental state. In fact, the experiences we undergo, 
 and their images which recur to us, are not pure knowledge ; 
 they affect us while they teach us ; they are at once a disturb- 
 ance and a light. Each one of them is accompanied by one or 
 many slight shocks, and each of them has for effect one or more 
 slight tendencies. Beneath images and experiences, vegetation 
 that thrives in the light, there is an obscure world of impulsions, 
 repugnances, startling shocks, sketchy, disorderly, discordant 
 solicitations, which we can barely distinguish, but which are 
 nevertheless the inexhaustible and ever-springing source of our 
 actions. These are the countless little emotions which, at the 
 close of our prolonged examination, sum themselves up in an 
 impression of a whole, and consequently, in a final and definite 
 tendency, and this tendency results in an expression. What- 
 ever this expression may be the imitative gesture of the artist, 
 the metaphorical half-sight of the poet, the expressive panto- 
 mime of the savage, the animated tones of the impassioned man, 
 the dry tone and abstract language of the calm reasoner the 
 mental operation is always the same; and if we inquire into 
 w r hat passes in us when, from several perceptions, we disen- 
 gage a general idea, we find and find only the formation, 
 completion, and preponderance of a tendency uiJtich urges an 
 expression, and, among other expressions, a name. 
 
 To revert to our first example. I observe in turn pines,
 
 12 OF SIGNS. [BOOK I. 
 
 ash, chestnuts, beech, oak, a whole forest ; I remark the spring- 
 ing trunk and spreading branches which form the two distinct- 
 ive characters of a tree ; I form a general conception of a 
 tree and use the word tree. This simply means that a certain 
 tendency in my mind corresponding to these two characters 
 and to these two characters only has at last become distinct 
 and predominant. On fifty consecutive occasions, and with- 
 out a single contradictory instance, it has in turn been aroused 
 at the sight of fifty trees ; and it only has been aroused on each 
 one of these fifty occasions. All other tendencies correspond- 
 ing to the peculiarities of the different trees, are effaced and 
 annulled by mutual contradiction ; it alone survives, and results, 
 as do all tendencies, in an expression. Mentally, this result is 
 an image, more or less vague that of a slender, then spread- 
 ing stem ; outwardly, it becomes the attitude and imitative 
 gesture of the body ; in primitive language, among infant races, 
 at the origin of speech, it is a poetical and figurative imitation 
 of another kind, of which we find fragments here and there ; 
 now-a-days, it has become a simple word, which we learn purely 
 by way of notation, the dry remains of the little symbolical 
 drama and living mimicry by which the first inventors, true 
 artists, translated their impressions. 
 
 IV. The reader now sees how it is we conceive a general 
 quality ; when we have seen a series of objects possessing a 
 common quality, we experience a certain tendency, a tendency 
 which corresponds to the common quality, and to it alone. It 
 is this tendency which calls up the name ; and when it arises 
 the name only is imagined or pronounced. We do not perceive 
 qualities or the general characters of things ; we only experience 
 in their presence such and such a distinct tendency, which, in 
 spontaneous language, results in a certain mimicry, and, in our 
 artificial language, in a certain name. We have, strictly speak- 
 ing, no general ideas ; we have tendencies to name and names. 
 But a tendency is nothing distinct in itself; it is the com- 
 mencement, the rudiment, the sketch, the approximation, 
 whether easy or difficult, to some thing, image, or name, or other 
 determinate act, which is its full development and accomplish- 
 ment ; it is the elementary form of the act which is its final 
 state. As to positive and definite acts, when we conceive or
 
 CHAP. II.] SIMPLE SUBSTITUTION. l ^ 
 
 know abstract qualities, all that passes in us are names, some 
 in process of being expressed or mentally imagined ; others al- 
 ready expressed and imagined. What therefore we call a gen- 
 eral idea, a comprehensive view, is only a name ; no't the sim- 
 ple sound that vibrates in the air and strikes our ear, or the 
 collection of letters which blacken the paper and attract the 
 eye, not even these letters perceived mentally, or this sound 
 pronounced mentally, but this sound or these letters endued, 
 when we experience or imagine them, with a double property, 
 that of arousing in us images of individuals belonging to a cer- 
 tain class, and of these individuals only ; and the property of 
 reviving when, and only when, an individual of this same class 
 is present to our memory or experience. The only difference 
 between the word tree, which has a meaning, and the word eter, 
 which has none, is that on hearing the second we do not imag- 
 ine any object or series of objects belonging to a distinct class, 
 and there is no object or series of objects belonging to a distinct 
 class which suggest to us such a word, whilst on hearing the 
 first word we involuntarily picture to ourselves an oak, a pop- 
 lar, a pear tree, or some other tree, and on seeing a tree, of 
 whatever kind, we involuntarily pronounce the word tree. In- 
 stead of eter put the word arbre ; to any one unacquainted with 
 French, the two words are of equal value, and result in the same 
 want of effect ; to a Frenchman the word arbre has precisely 
 the properties which we have just found in the word tree. A 
 name, then, which we understand is a name connected with all 
 the individuals which we can perceive or imagine belonging to 
 a certain class and only with the individuals of this class. In 
 this way it corresponds to the common and distinctive quality 
 which constitutes the class and separates it from other things, 
 and corresponds to this quality only ; wherever the quality is, 
 there is the name ; whenever this quality is absent there is no 
 name ; it is aroused by it, and by it only. Thus it becomes its 
 mental representative, and the substitute of an experience to 
 which we cannot attain. It stands in place of this experience, 
 it fulfils its office, and is equivalent to it. 
 
 Admirable and spontaneous artifice of our nature : we can 
 neither perceive general qualities nor maintain them separate 
 in our minds ; and yet, they are the precious veins which con-
 
 !4 OF SIGNS. [BOOK I. 
 
 stitute the essence and are the foundation of the classification 
 of things, and, to enable us. to emerge from gross animal expe- 
 rience, to seize the order and internal structure of the world, 
 we must draw them from their ore and conceive them apart. 
 We make a circuit, we associate with each abstract and gener- 
 al quality a little special complex fact, a sound, a figure easy 
 to imagine and reproduce ; we make the association so close 
 and precise, that henceforward, the quality cannot appear or be 
 missing in things without the appearance or absence of the name 
 in our minds, and reciprocally. The couple so formed resem- 
 bles those physical and chemical instruments, which, by a tri- 
 fling sensible change, the displacement of a needle, the altera- 
 tion of a color, bring within the range of our senses, decompo- 
 sitions of substances, or variations of currents, to which our 
 senses cannot otherwise attain. The sudden reddening of a 
 stained paper or the greater or less twist of a suspended needle 
 are connected with an inner change or a certain degree of hid- 
 den action, and we observe the second things to which we can- 
 not directly attain, in the first to which we do attain. And 
 similarly, when we are dealing with a general quality of which 
 we can have neither experience nor sensible representation, we 
 substitute, and substitute legitimately, a name for the impossible 
 representation. It has the same affinities and repugnances as 
 the representation, the same hindrances to and conditions of ex- 
 istence, the same extent and limits of presence ; affinities and 
 repugnances, hindrances and conditions of being, extent and 
 limits of presence, all we meet in the one we meet, indirectly, 
 in the other. Owing to this correspondence, the general char- 
 acters of things are brought within range of our experience ; for 
 the names expressing them are, themselves, either small expe- 
 riences of sight, the ear, the vocal muscles, or internal images, 
 that is to say, revivals more or less clear, of these experiences. 
 An extraordinary difficulty has been surmounted ; with beings 
 whose life is but one varied and continuous experience, special 
 and complex impressions can alone be found ; out of these spe- 
 cial and complex impressions nature has manufactured the equiv- 
 alents of others, which are neither special nor complex, and 
 which, as they cannot be so, would seem as if they must escape 
 forever by necessity and nature from beings constituted as we are.
 
 CHAP. II.] SIMPLE SUBSTITUTION. : e 
 
 V. The formation of these general names may be narrowly 
 watched ; with little children, we take them in the act. We 
 name to them such and such a particular determined object, 
 and, with an instinct of imitation common to them with mon- 
 keys and parrots, they repeat the name they have just heard. 
 Up to this point they are but as monkeys and parrots ; but 
 here there appears a delicacy of impression which is special to 
 man. We pronounce the word papa before a child in its cra- 
 dle, at the same time pointing out his father. After a little, 
 he in his turn lisps the word, and we imagine that he under- 
 stands it in the same sense that we do, or that his father's pres- 
 ence only will recall the word. Not at all. When another per- 
 son that is, one similar in appearance, with a long coat, a 
 beard, and loud voice enters the room, he calls him also 
 papa. The name was an individual one ; he has made it gen- 
 eral. In our case, it is applicable to one person only ; in his, 
 to a class. In other words, a certain tendency, corresponding 
 to what there is in common to all persons in long coats, with 
 beards and loud voices, is aroused in him in consequence of the 
 experiences by which he has perceived them. This tendency is 
 not what you were attempting to excite ; it springs up spon- 
 taneously. In it we have the faculty of language. It is 
 wholly founded on the consecutive tendencies which survive 
 the experience of similar individuals, and corresponds precise- 
 ly to what they have in common. 
 
 We see these tendencies continually at work in children, 
 and leading to results differing from ordinary language ; so that 
 we are obliged to correct their spontaneous and too hasty at- 
 tempts. A little girl, two years and a half old, had a blessed 
 medal hung at her neck. She had been told, " Ccst le bon 
 Dieu" and she repeated, " Ccst le bo Du." One day, on her 
 uncle's knee, she took his eyeglass, and said, " Ccst le bo Du 
 de mon onclc" It is plain that she had involuntarily and nat- 
 urally constructed a class of objects for which we have no 
 name ; that of small round objects, with a handle, through 
 which a hole is pierced, and hung around the neck by a ribbon ; 
 that a distinct tendency, corresponding to these four general 
 characters, and which we do not experience, was formed and 
 acting in her. A year afterwards, the same child, who was
 
 1 6 OF SIGNS. [BOOK I. 
 
 being asked the names of different parts of the face, said after 
 a little hesitation, on touching her eyelids, " These are the eye- 
 curtains." A little boy, a year old, had travelled a good deal 
 by railway. The engine, with its hissing sound and smoke, and 
 the great noise of the train, struck his attention, and the first 
 word he learned to pronounce wasfafcr (chemin de fer). Hence- 
 forward, a steamboat, a coffee-pot with spirit-lamp every thing 
 that hissed or smoked, or made a noise, was ^fafer. Anoth- 
 er instrument to which children have a great objection (excuse 
 the detail and the word I mean a clysoponipe] had, naturally 
 enough, made a strong impression on him. He had termed 
 it, from its noise, a zizi. Till he was two years and a half old, 
 all long, hollow, slender objects a scissors-sheath, a cigar-tube, 
 a trumpet, were for him zizi, and he treated them all with dis- 
 trust. These two reigning ideas, the zizi and the fafer, were 
 two cardinal points of his intelligence, and from them he set 
 out to comprehend and name other things. 
 
 In this respect the language of children is as instructive to 
 a psychologist as the embryonic states of organized bodies are 
 to the naturalist. Their language, unlike ours, is living, and 
 incessantly on the change ; not only are words defaced or in- 
 vented, but, more than this, the sense of words is not the same 
 as in our language. A child who pronounces a name for the first 
 time never takes it in the precise sense which we give it. This 
 sense is more or less extensive to him than to us ; it is propor- 
 tioned to his experience at the time ; is enlarged or reduced 
 daily by his new experience, and brought very slowly down to 
 the precise dimensions which it has for us.* A little girl, of 
 eighteen months old, had been heartily amused by her mother, 
 or nurse, hiding in play behind the door or chair, and saying, 
 " Coucou" Again, when her dinner was too hot ; when she 
 went too near the fire ; when she put out her hand to the can- 
 
 * An analogous difference appears in comparing the synonyms in two languages : 
 clergyman and ecclesiastiqtie, God and Dieu, llebe and amour, brio and brillant, girl 
 and jeun fille, do not respectively mean the same things, though we translate one 
 by the other. The two words of each couple represent two different objects, and 
 are differently understood by the two peoples. Their senses is the same in the rough ; 
 the details of their meanings are different and untranslatable in the absence of sim- 
 ilar objects and emotions in the two cases.
 
 CHAP. II.] SIMPLE SUBSTITUTION. ij 
 
 die ; when they put on her hat in the garden, to keep off the 
 hot sun, she was told " Ca bride" Here were two remarkable 
 words which, to her, represented things of supreme impor- 
 tance ; her most painful sensation and her most pleasurable 
 one. One day, seeing from a terrace the sun disappearing be- 
 hind a hill, she said, "A bule coucou." Here we have a com- 
 plete judgment, not only expressed by words which we do not 
 employ, but also corresponding to ideas, consequently to class- 
 es of objects, to general characters, to distinct tendencies, which 
 in our cases have disappeared. The hot soup, the fire on the 
 hearth, the flame of the candle, the noonday heat in the gar- 
 den, and last of all, the sun, make up one of these classes. The 
 figure of the nurse or mother disappearing behind a piece of 
 furniture, the sun disappearing behind a hill, form the other 
 class. Both are limited to this ; the tendency consecutive to 
 the first resulted in the words a bule ; the tendency consecu- 
 tive to the second in the word coucou. Such a state of mind 
 differ.5 greatly from ours ; but, nevertheless, it consists of ten- 
 dencies analogous to ours, aroused in the same way as ours, 
 corresponding to general characters as with us, but to characters 
 less general, in short, resulting in names similar in sound and 
 different in sense. 
 
 In proportion as the experience of children approaches 
 more nearly to our own, their tendencies to name coincide 
 more exactly with ours ; they become organized by degrees 
 like embryos. As in the foetus, we see, in turn, the dispropor- 
 tionate head reduced to its proper proportions, the sutures of 
 the skull harden, the cartilage turn into bone, the rudimenta- 
 ry vessels close and ramify, the communication between child 
 and mother become obstructed ; so do we see, in the language 
 of children, the two or three dominant words lose their abso- 
 lute preponderance, the general words limit their too extensive 
 meaning, gain precision for their vagueness of sense, acquire 
 connections, attachments and sutures with each other, become 
 complete by the incorporation of other tendencies, become ar- 
 ranged under these into names of smaller classes, form a sys- 
 tem corresponding to the order of beings, and at last act by 
 themselves alone, and of themselves, without the aid of assisting 
 namegivers. A child has watched its mother put on her white
 
 1 8 OF SIGNS. [BOOK I. 
 
 dress for a ball ; he has remembered the word, and in future, 
 when he meets a lady in evening dress, whether she has on red 
 or blue, he will say in his singing, curious, happy voice, " You 
 have put on your white dress'' White is too large a word ; he 
 will have for the future to reduce its application to a single col- 
 or. The same child hears his mother say to him, " You swine 
 
 * o 
 
 your head too much ; it will strike the table." He says, in a 
 curious and surprised way, "Your head will strike the table?" 
 Your again has received too large a sense ; he must be taught 
 to reduce it to mean the head only of the person he is speak- 
 ing to. The process of checking goes on ; new experience 
 will complete the tendency which produced the word white, 
 and once accomplished, it will correspond not only to the pres- 
 ence of bright fresh color, but, more than this, to the presence 
 of a particular color. Similarly, and by another series of expe- 
 riences, the tendency which produced the word your when given 
 definite precision, will correspond not only to possession, but 
 also to this supplementary circumstance, that the thing, pos- 
 sessed belongs to the person spoken to. Such is the history 
 of language : we experience spontaneously, after having come 
 in contact with a series of similar objects, a tendency which 
 corresponds to what there is in common to these objects ; that 
 is to say, to some general character, to some abstract quality, 
 to an extract from the objects, and this tendency results in a 
 gesture, in some mimicry, in some distinct sign, which in ma- 
 turity becomes a name. 
 
 Herein consists the superiority of the human intelligence. 
 Very general characters arouse in it distinct tendencies, in 
 other words, very slight resemblances between different objects 
 are sufficient to exite in us a name or spesial designation ; 
 a child succeeds here without effort, and the genius of well- 
 endowed races, as that of great men, and notably of inventors, 
 consists, in observing resemblances more or less delicate and 
 novel ; that is, in feeling arise in them, at the sight of objects, 
 certain slight and delicate tendencies, and consequently, distinct 
 names, which correspond to shades imperceptible to ordinary 
 minds, to the very slight characters hidden beneath a heap of 
 the coarse, striking circumstances, alone capable, when the mind 
 is ordinary, of leaving an impression upon it, and having a
 
 CHAP. II.] SIMPLE SUBSTITUTION. r g 
 
 response in it. This aptitude once established, the rest follows. 
 By the accumulation and contrariety of daily experiences, ten- 
 dencies and names multiply, are circumscribed, and become 
 subordinated, like the general qualities they represent; and 
 the hierarchy of things is translated and repeated within us by 
 the hierarchy of tendencies and names. 
 
 VI. On the other hand, if we may use the expression, names 
 fill out. In proportion as our experiences become more numer- 
 ous, we remark and consequently name a greater number of 
 general characters in the same object. Its name, which at first 
 denoted the single character which struck us at first sight, now 
 denotes several others. It now corresponds, not to an abstract 
 quality, but to a group of abstract qualities ; it was only general, 
 it becomes collective. 
 
 Take any animal, a cat, for instance. As all cats have points 
 of strong resemblance, and differ a good deal from our other 
 animals, we have no difficulty in learning their common name, 
 and observing their common characteristics. In other words, 
 this name corresponds to a certain distinct form, at rest or 
 moving, sleeping in a stable, or creeping cautiously along a roof. 
 This is the common popular sense, and the tendency which re- 
 sults in the name corresponds to little more than this. But a 
 naturalist takes me, and opening a cat, shows me the pouch we call 
 the stomach, the little vessels we call veins and arteries, with 
 their infinite ramifications ; the collection of smooth tubes 
 which are the intestines, and the .bars, arches, frames, cavities, 
 and hinges, which, with their connections, make up the skeleton. 
 I might remain for six months continually seeing new things. 
 If I were to work with a microscope, my life would not be long 
 enough, and, speaking accurately, no life or series of lives would 
 suffice ; beyond the observed properties, there will always re- 
 main others unobserved, tl\e unlimited matter of an unlimited 
 science. Henceforward the name corresponds for me, not 
 merely to the experience of a certain external form, but also 
 to that of a certain internal structure, that is, to an enormous 
 number of various phenomena which I have experienced, and 
 to an indefinite number which I might experience. If I have 
 paid sufficient attention to the internal structure, I shall pro- 
 nounce the word cat as confidently when I see the blanched
 
 2O OF SIGNS. [BOOK I. 
 
 skeleton, as at the sight of the living furry body. The second 
 experience now results in the same name as the first. Two 
 distinct tendencies coincide therefore in the same effect. The 
 name has become the equivalent of the characters common to 
 the different skeletons of the kind, as of the characters common 
 to the different living animals of the kind ; its presence, which 
 once aroused images only of certain velvety, living, bounding 
 forms, now arouses also images of certain bony lifeless frame- 
 works. It may arouse many other images, those of all the 
 mechanical, physical, chemical, anatomical, vital, moral peculi- 
 arities which naturalists and moralists can discover in the race 
 of cats ; it assembles them all in itself, together with the names 
 we denote them by; it is the substitute of the whole band. 
 On hearing the name cat, we can substitute for it a definition 
 or a description that is to say, replace it either by the two 
 principal names which determine its rank in the classification 
 of animals, or by the names of all the characters which our ex- 
 periences have discovered in it, and consequently, recall more 
 or less vividly to our minds, the likenesses of such experiences. 
 Henceforth, the couple whose first term is the name, comprises 
 as second term, an immense list of other words, and conse- 
 quently, as great a series of distinct tendencies, which corre- 
 spond to general characters equally distinct, and leave room be- 
 side them for an infinite number of new tendencies which ex- 
 perience may excite. Such is the power of the substitution 
 established by couples. Two. terms being the equivalents of 
 one another, the first, which is so simple, so manageable, so 
 easy to recall, is capable of replacing the second, even when the 
 second is an immense army, whose lists always open, await and 
 are continually receiving new soldiers. 
 
 The reader sees at once that in place of the name cat we 
 might put that of dog, monkey, crab, or of any animal or plant 
 whatever ; or again, that of any group, animal or vegetable, as 
 extensive or as narrow as we please, and, in general, of any group 
 moral or physical. The operation would be similar ; all general 
 names acquire extensions of meaning in the same way. Ar- 
 ranged in relation to one another, each with its retinue of ten- 
 dencies, they make up the principal furniture of a thinking 
 brain. By the side of continual experiences and reviving im-
 
 CHAP. II.] SIMPLE SUBSTITUTION. 21 
 
 ages, there are names which we term ideas ; all of them mental 
 representatives of abstract characters and general qualities, each 
 one called up' by some distinct tendency, all incessantly extend- 
 ed by new tendencies, gaining precision in their application, and 
 increased in their contents by the daily progress of discovery y 
 which, adding to their meanings, limits their application.
 
 22 OF SIGNS. [BOOK. I. 
 
 CHAPTER III. 
 
 OF GENERAL IDEAS AND REPEATED SUBSTITUTIONS. 
 
 I. THERE are things of which we can have no experience ; 
 now, since experiences are what, by their common character, 
 arouse in us a distinct tendency and the name which we term 
 an idea, it seems as if we could never attain to ideas of such 
 things. We have, nevertheless, very clear and exact ideas of 
 them. The operation, which consists in giving names to things, 
 becomes complicated, and leads us by a circuit to unhoped-for 
 successes. The same instrument is at work as before, but it 
 works by a series of substitutions, instead of a simple sub- 
 stitution. 
 
 Consider the first number that comes to hand : 36, for ex- 
 ample. When I read this sign, I thoroughly understand its 
 sense ; that is, I clearly imagine what it replaces. 36 is by defini- 
 tion ^plus i. In other words, the group we call 36 is the same 
 as that which we call 35, if to 35 we add I. 36, then, is a col- 
 .lective term which replaces two others. But 3 5, by definition, is 
 34 plus I ; 34, again, is 33 phis I ; and so on. 36, then, in final 
 analysis, is an abbreviatory expression which replaces thirty-six 
 others. Let us go back to the elements, the better to under- 
 stand this operation. 
 
 Suppose a red counter at one corner of the table, and a 
 white one at another. I may neglect all their respective qual- 
 ities, and be struck solely with the fact that a part of my im- 
 pression is repeated, and feel that what I have just experienced 
 in the case of the red counter is, up to a certain point, similar 
 to what has happened in the case of the white, and after the 
 two several experiences, may feel a distinct consecutive tenden- 
 cy, corresponding to their number, that is, to the property they 
 have of being two. This, like all other tendencies, results in a 
 sign ; let us take for this sign the ordinary word, two. Here 
 is a general name ; we shall be inclined to pronounce it, as
 
 CHAP III.] REPEATED SUBSTITUTIONS. 33 
 
 in the case of the counters, after each repeated experience. 
 Similarly, too, when we read it, or hear it, we have only to dwell 
 on it to call up inwardly, as with the word cat or birch-tree, an 
 image of a case to which it is applicable ; we think of a counter 
 beside a counter, a stone, a sound followed by a sound, as just now 
 we imagined a tapering face with white or gray fur, a slender white 
 trunk with small quivering leaves. The same is the case with 
 the words, three, four ; it is more difficult with the words, five, 
 six ; the difficulty increases with the higher numbers, and there 
 is always a figure, larger or smaller, at which the mind stops ; 
 we cannot perceive or represent distinctly to ourselves as a 
 whole, more than a certain number of facts or objects ; generally 
 five or six, more often four. To remedy this inconvenience we 
 neglect the group corresponding to the word, and fix our whole 
 attention on the word we have substituted for it ; after seeing 
 four objects together we forget them, and think only of the word 
 four, and this is allowable, since when later on we return to 
 the word and consider it, we shall see the objects again in our 
 minds without mistake or confusion. Here then we have four 
 operations replaced by one only. When a new object, similar to 
 the foregoing ones, is met with after we have pronounced the 
 word four, it will form, with the word, a new group, and will excite 
 in us a tendency analogous to that which made us use the word two 
 a tendency similar to the first from its involving an addition, 
 differing from the first from its being an addition, not of one 
 object to. another, but of an object to a group of four objects. 
 This new tendency results in a new name, five. Another, excited 
 by this previous one, will result in the word six, and so on. 
 We see that in this scale each new name is the substitute of the 
 preceding one, and consequently of the object of the pre- 
 ceding one joined to unity. 
 
 Here, again, an insurmountable difficulty has been evaded. 
 If we can imagine distinctly as a whole two, three, or even four 
 objects, we cannot do so with respect to 36 as a whole. . The 
 abstract and general property of being two, three, or four, may 
 arouse in us a tendency, arid consequently a corresponding 
 name ; on the other hand, the general and abstract property 
 of being 36, or any other considerable number, cannot do this. 
 Before an obstacle like this we must proceed indirectly ; we
 
 24 . OF SIGNS. [BOOK I. 
 
 bridge over the ditch too wide for our legs. We no longer 
 replace at once by a word the general and abstract character 
 of the group in question ; for experience cannot successfully 
 attain to such a group. Thirty-six pawns on a chess-board 
 give an impression only of a mass and a whole, without distinct 
 numerical knowledge of the individuals. We proceed more 
 slowly ; we first take a very small group, proportioned to the 
 limited range of our minds, and capable of arousing in us a ten- 
 dency and a name. We next join this name, and consequently 
 the object of the name, that is, the little group, to a new indi- 
 vidual, and this arouses in us another tendency and another 
 name ; and thus step by step we journey on to the final name, 
 and this once obtained, corresponds to the abstract character 
 which did not directly arouse a name. 
 
 In this respect the final name is very remarkable. If we 
 look for its sense we find a name only, that of the lower figure 
 to which we add unity ; the same thing happens with this lower 
 figure, and so on ; it is only at the end of this retracement of " 
 our steps, when we have descended some 30, 50, 100, 1000, or 
 10,000 stories, that we arrive again at our experience. And 
 yet this name replaces an experience, another experience which 
 we have not attained, which we cannot attain, which is above 
 man's powers, but which is in itself possible, and which a more 
 comprehensive mind might attain to : 36 denotes the quality 
 common to all groups of 36 individuals ; a quality which, as pre- 
 sented to us, does not excite any precise tendency, and which 
 a mind capable of representing before it at once 36 objects or 
 facts in a distinct state, would alone experience. By this arti- 
 fice, we attain the same results as creatures endowed with im- 
 aginations and memories far more clear and vast than our own. 
 Here, as before, all has been effected by substitution. After 
 having enabled us to arrive at abstract qualities, she affords us 
 the means of counting and measuring quantities. Thanks to 
 substitutions, we were enabled to conceive the abstract qualities 
 of individuals. Thanks to a series of repeated substitutions, 
 we are able to name, and consequently to conceive, certain ab- 
 stract properties peculiar to groups properties which the natu- 
 ral limitation of our imagination and memory seemed to hinder 
 us from* ever conceiving, that is to say, from naming.
 
 CHAP. III.] REPEATED SUBSTITUTIONS. 25 
 
 II. The efficiency of substitution extends far beyond this. 
 As the reader knows, geometrical objects do not exist in na- 
 ture. We do not meet, and probably can never meet, with 
 perfect circles, cubes, and spheres. Those we see or construct 
 are but approximately so. Nevertheless, we conceive them as 
 perfect ; we reason about figures of absolute regularity. We 
 know, with complete certainty, what is the obtuseness of each 
 angle in a regular myriagon, and to how many right angles the 
 whole of its angles taken together amount. Besides this, when 
 for the better apprehension of a geometrical theorem we con- 
 struct a diagram on paper, we trouble ourselves very little as to 
 its perfect proportions ; we admit without difficulty shaky lines 
 in our polygon, and irregular curvature in our circle. In fact, 
 we do not consider the circle traced on the paper; it is not the 
 object, but the aid of our thought ; by its means we conceive 
 something differing from it, which is neither black nor traced 
 on a white ground, nor of any particular radius, nor of unequal 
 curvature. What, then, is this object we conceive, and of which 
 experience affords us no model ? The definition tells us. A 
 circle is a closed curve, all whose points are equally distant 
 from an internal point called the centre. But what have we in 
 this phrase ? Nothing, except a series of abstract words which 
 denote the genus of the figure, and another series of abstract 
 words which denote the species of the figure, the second being 
 combined with the first, as a condition added to a condition. 
 In other terms, an abstract character denoted by the first words 
 has been joined to an abstract character denoted by the second 
 words, and the total compound thus constructed denotes a new 
 thing to which our senses cannot attain, which our experience 
 cannot come in contact with, which our imagination cannot 
 trace. There is no necessity for our attaining to, meeting with, 
 or imagining this thing ; we have its formula, and that is enough. 
 
 In fact, this formula would be rigorously the same if the 
 object had fallen within our experience. We have constructed 
 the formula before instead of after the experience, and it corre- 
 sponds all the more closely to the thing, since the thing must 
 bend to it not it to the thing. The two then make up a 
 couple whose second term, the definition, is equivalent to the 
 first term, that is, to the object. This object may remain
 
 2 6 OF SIGNS. [BOOK I. 
 
 ideal : it may itself be situated beyond our grasp ; it matters 
 little ; we have its representative. Whatever properties and re- 
 lations we find in the substitute we shall safely ascribe to the 
 thing for which it is substituted. We arrive at this indirectly, as 
 a surveyor, who, wishing to measure an inaccessible line, 
 measures a base and two angles, and knows the first quantity 
 by the three second. In this way all mathematical concep- 
 tions are formed. We take very simple abstractions, the surface 
 which is the limit of the solid, the line which is the limit of 
 the surface, the point which is the limit of the line, the unit or 
 quality of being one, that is to say, distinct existence among 
 similar things. We combine these terms together and form, 
 first, compounds of small complexity, those of two, three, four, 
 and the earlier numbers, those of plus and minus, of greater 
 and less, of longer and shorter lines ; then those of straight line 
 and curve, of triangle, of circle ; then, those of sphere, cone, 
 cylinder, and the rest. The complication of compounds goes on 
 increasing; it is unlimited. Taken together they form a king- 
 dom apart of objects which have no real existence, but which 
 are capable, like real objects, of being classed in families, genera, 
 species, and properties, of which we discover by considering in 
 their place the properties of the formulae which we substitute 
 for them. 
 
 By a strange continuation the process which has formed 
 these objects is also that which establishes their relations. 
 Arithmetic, algebra, geometry, analytical geometry, mechanics, 
 the higher calculus, all the propositions of mathematical science, 
 are substitutions. Any number we take is a substitute for the 
 preceding number added to unity. To calculate, is to replace 
 several numbers by a single one at the end of several partial re- 
 placements. To solve an equation, is to substitute terms for oth- 
 er terms with the object of arriving at a final substitution. To 
 measure, is to replace an undetermined magnitude by another 
 magnitude defined in its relation to unity. To construct a 
 diagram for the demonstration of a theorem is to substitute 
 certain known lines and angles for other lines and angles which 
 it is required to know. To find the algebraic formula of a 
 curve, is to discover mathematical relation between certain 
 lines which are connected with the curve, and to translate quality
 
 . III.] REPEATED SUBSTITUTIONS. 27 
 
 into quantity. However we may reason about numbers and 
 magnitudes, the process amounts to passing from one equivalent 
 to another equivalent by the aid of a series of intermediate 
 equivalents, to replacing magnitudes by numbers expressing 
 them, a figure by a corresponding equation, a complete quan- 
 tity by a quantity in process of completion, having the .first as 
 limit, movements and forces by lines representing them. We 
 pass from each province to the other by substitutions, and. 
 as a substitute may have substitutes, the operation has no 
 limits. 
 
 III. Leaving for the moment this extension of our process, 
 let us consider it once more at its outset. We have seen how, 
 by combining abstracts, we construct the first terms of couples, 
 the second terms of which are beyond our reach, and how, by 
 the study of the generating formula, we discover the properties 
 of the object engendered by it. In certain cases, we discover 
 in it wonderful properties, and the formula makes known to us 
 facts situated not only beyond our experience, but beyond all 
 experience. If we divide 2 by 3, we find an infinite decimal 
 fraction, 0-6666, etc., and we can prove that it is infinite. It is 
 strictly so, and without possible break ; however, far we may 
 prolong the operation, the remainder will always be 2 and the 
 quotient always 6. After a million, after a thousand million, 
 after a million million of such divisions, new terms will present 
 themselves, with the same remainder and the same quotient," 
 with a total quotient always too small, to small by a fraction 
 with 2 for numerator, and for denominator unity followed by as 
 many zeros as there are units in the number of divisions we have 
 made. Here is something infinite ; not vague, not indefinite, 
 but precise, which is expressly opposed to any limit, and so 
 clearly conceived that all its elements have their distinct and 
 express properties. Does this mean that I perceive distinctly 
 the infinite series of these elements ? Certainly not. Here 
 again, there is a substitute, the formula, from which the series 
 and the properties of its elements are derived. What we per- 
 ceive, is a general character of the dividend and remainder. 
 After the first division we can see that, the remainder being 2 
 like the dividend, must, in becoming in its turn a dividend, give 
 rise again to a remainder 2, which in its turn will do the same,
 
 2 8 OF SIGNS. [BOOK I. 
 
 and so on. In other words, we discover in the dividend this 
 property of giving rise to a similar figure, which, being similar 
 to it, has the same property as it. This abstract quality is the 
 cause of the whole series'; it forces it to be infinite, it alone is 
 what we perceive ; when we say that we conceive an infinite 
 series, it only means that we discover this property of inex- 
 haustible regeneration ; all we seize is the generating law ; we 
 do not embrace all the engendered terms. But as far as we 
 are concerned the effect is the same ; for by applying the law 
 we are able to define whatever term we please of the series, to 
 measure exactly the increase of approximation it brings to the 
 quotient, to calculate strictly the degree of error which the 
 division would include were we to stop Jiere. The perception 
 of the law is equivalent to the perception of the series ; an in- 
 finite line of distinct terms finds its substitute in an abstract 
 character, and, in place of an experience which is by defini- 
 tion impossible, we have disengaged a property whose isola- 
 tion has only required two experiences, and which is of equal 
 value to us. 
 
 And so it happens, whenever we conceive and affirm some 
 really infinite abstract magnitude, time, or space. We take a 
 fragment, some short portion of the duration comprised in our 
 successive sensations, some narrow portion of space comprised 
 in our simultaneous sensations. We consider this fragment 
 'apart ; we extract from it this property it has of being over-ex- 
 tended by a border absolutely similar to itself. We lay down, 
 as before, a general law that the magnitude in question is con- 
 tinued beyond itself by another wholly similar magnitude, and 
 this by another, and so on, without the possible intervention of a 
 limit. Our conception of infinite time and infinite space is re- 
 duced to this. But the result is the same as if the field of our 
 imagination were infinitely extended and capable of setting be- 
 fore us at a glance the whole infinite succession we call time, or 
 the extension, infinite in three directions, which we call space. 
 For starting from the general character which alone is present 
 to our minds, we are able to imagine any portion of time or space 
 as clearly, and to affirm of it as surely, as if we had experience 
 of it ; no matter what the portion be, whether a fragment of 
 duration preceding the solar system, or a portion of space be-
 
 CHAP. III.] REPEA TED SUBSTITUTIONS. 
 
 2 9 
 
 yond the furthest nebulas of Herschel. It is possible, then, to 
 represent infinite objects, series, or quantities,* by an abstract 
 property. It is enough if this is their generator. By it, indi- 
 rectly, they become present. Here we have, I think, the most 
 extraordinary example of substitution. There are other cases, 
 analogous but reversed, in mathematics ; certain quantities, 
 which go on increasing or decreasing, without the possibility 
 of a limit, replace the limit which they necessarily approach 
 without ever touching it. A polygon with an infinite number of 
 sidos inscribed in a circle is equivalent to the circle. The frac- 
 tional number I \ \ -, etc., is equivalent to the num- 
 ber 2. Here again, as before, mathematicians do but resume, 
 extend, or reverse a spontaneous process of the mind. The 
 process is explainable similarly, whether direct or reversed. 
 Given two members of a couple, one infinite, the other limited, 
 we can consider at will the one or the other, and if they corre- 
 spond strictly, can discover in the one properties belonging also 
 to the other, but not discoverable in it. 
 
 IV. To recapitulate. We do not conceive numbers, with 
 the exception of the three or four earlier ones, but their equiv- 
 alents, that is to say, the name of the preceding number 
 joined to unity ; we do not conceive infinite or ideal objects, 
 but the abstract characters which generate them ; we do not 
 conceive abstract characters, but the common names which cor- 
 respond to them. However far we may go, we always come 
 back to names. Things the most removed from our experi- 
 ence and the most inaccessible to all experience, seem present 
 to us ; what is actually present, in such a case, is a name, the 
 substitute of an abstract character which is itself the substitute 
 of the thing, and this often only through many intermediate 
 stages, till at last by a series of equivalents the chain re-touches 
 the distant object which we cannot directly reach. 
 
 Hence arise singular illusions. We believe that, in addi- 
 tion to our general words, we possess general ideas ; we dis- 
 tinguish the idea from the word ; it seems to us something 
 apart from the word, and to which the word is merely auxili- 
 
 * When we speak of an infinite quantity, it is by extension ; strictly speaking, 
 a quantity is always finite, and there is nothing infinite but series.
 
 3 o OF SIGNS. [BOOK I. 
 
 ary ; we compare it with the image, and pronounce them to 
 fulfil similar offices in distinct provinces, and that ideas bring 
 present to us general things, as images bring present individu- 
 als. We remark with Descartes, that we can readily conceive 
 a myriagon but have great difficulty in imagining it. We set 
 on one side the intelligible myriagon and the corresponding 
 precise idea, and, in contrast, the actual myriagon and the cor- 
 responding confused image. We then observe that this idea 
 is in no way similar to the image ; except in its employment ; 
 it brings before us an absent thing as the image does, but that 
 is all. It has no other properties ; it is not, like the image, an 
 echo; the echo of a sound, a smell, a color, a muscular impres- 
 sion, in short, the internal revival' of some sensation; there is 
 nothing sensible about it, and we can only define it by deny- 
 ing of it all sensible qualities ; it seems then a pure activity 
 stripped of all other qualities but that of bringing the myria- 
 gon present to our minds. We compare it to something in- 
 tangible, unextended, incorporeal ; we suppose a being as pure 
 and ethereal as itself of which it is the manifestation ; we call 
 it mind, and say that, irrespective of images, our mind knows 
 and deals with abstract qualities of things. 
 
 The mechanism of this illusion may now be readily detect- 
 ed. We have overlooked the word which is the whole sub- 
 stance of our operation; we have treated it as accessory and 
 have considered the operation, omitting what it comprises ; 
 hence a blank. This error of consciousness is of frequent 
 occurrence and may be traced to a general law. When an 
 impression, or group of impressions, is many times repeated, 
 our attention ends by fixing itself entirely on the interesting 
 and useful part ; we neglect the rest, we cease to notice it, we 
 become unconscious of it, and though present, it seems to be 
 absent. So it is, for instance, with the slight muscular sensa- 
 tions occasioned by the eye adapting itself to various distan- 
 ces ; they are the signs of these distances, and by them we de- 
 termine the degree of proximity or distance of objects. We 
 necessarily have these sensations when we judge of distances, 
 but we cannot detect them, even if we wish to. To us, they 
 are as if they did not exist ; we appear to know directly, and 
 without their aid, the positions which they alone denote ;
 
 CHAP. III.] REPEATED SUBSTITUTIONS. 3! 
 
 if ever they strike us, it is in extreme cases, as when we at- 
 tempt to read something at a distance, or inconveniently near 
 the eye, and feel sensible fatigue in the muscles ; except in such 
 cases they are invisible, and have, as it were, vanished. So 
 again, a composer who has just read some air of an opera, docs 
 not recall the crotchets, quavers, keys, staves, and all the black 
 hieroglyphics over which his eyes have passed, but only the 
 series of chords which he has heard mentally ; the signs are 
 obliterated, the sounds alone survive. When words are in 
 question, we can trace the different degrees of this obliteration. 
 The meaning of a page in manuscript is comprehended with far 
 more difficulty than that of a printed one ; our attention is 
 partly attracted by the external form of the characters, in place 
 of attaching itself solely to the sense they bear; we observe 
 the individual peculiarities of the signs, as well as what they 
 are employed to represent. But after a while, these peculiar- 
 ities cease to strike us ; when they are no longer new, they are 
 no longer singular, and no longer singular, are no longer 
 observed ; and then, in the manuscript as in print, we seem 
 no longer to be following words, but pure ideas. We see 
 now how it necessarily happens, that in our reasonings, and 
 all the higher operations of the mind, the word, though 
 present, is unperceived. From the train of our discoveries 
 we conclude that we have acted, and produced a series of 
 acts, that this series corresponds to a series of qualities, or 
 characters of things, that our activity is effective, and therefore 
 real. What then can we affirm of this internal activity? Noth- 
 ing, except that it is activity; by the disappearance of words 
 we have exhausted it of all it comprises ; we set it apart pure 
 and simple, or as we say, spiritual ; having stripped it, we be- 
 lieve it to be naked ; and when, later on, we observe that to 
 produce it we have made use of signs, we conclude that the sign 
 is but a preliminary aid to it, and a distinct reminder of it. 
 This separation and nudity are of our own effecting ; they do 
 not belong to it, but are lent it by us. 
 
 This is the first of psychological illusions, and what we term 
 consciousness swarms with such. The false theories they have 
 given rise to are as complex as they are many, and are at pres- 
 ent obstructing science. When they are cleared away, science
 
 22 OF SIGNS. [BOOK I. 
 
 will become simple again. Having discarded this illusion, we 
 see the consequences. What we have in our minds when we 
 conceive general qualities and characters of things, are signs 
 and signs only. I mean certain images or revivals of sensations 
 of the eye or ear, wholly similar to other images, except in their 
 corresponding to characters and general qualities of things, and 
 in their replacing the absent or impossible perception of these 
 characters and qualities. Thus when, neglecting present sen- 
 sations, we observe the never-resting inmates of our mind, we 
 find there images only, some prominent ones which strike the 
 attention, others faded, and seemingly worn away to shadows, 
 on account of the attention being diverted from them to their 
 uses. Here we have an element of knowledge which seemed 
 primitive, but which is reduced to another. We must now at- 
 tempt to know that other. Since our ideas may be reduced to 
 images, their laws may be reduced to laws of images ; images 
 then are what we must study.
 
 CHAP. L] NATURE AND REDUCTION OF IMAGES 33 
 
 BOOK II. 
 
 OF IMAGES. 
 
 CHAPTER I. 
 
 OF THE NATURE AND REDUCTION OF IMAGES. 
 
 I. YESTERDAY evening,* about five, I was on the quay by 
 the Arsenal, watching in front of me, across the. Seine, the sky 
 reddened by the setting sun. Fleecy clouds rose in the form 
 of a half dome, and bent over the trees of the Jardin des 
 Plantes. The whole of this vault seemed incrusted with scales 
 of copper; countless indentations, some almost burning, some 
 nearly black, extended, in rows of strange metallic lustre, up 
 to the highest part of the sky, while, all below, a long bronze- 
 colored band, extending along the horizon, was streaked and 
 cut by a black fringe of branches. Here and there, rose-col- 
 ored gleams of light rested on the pavements ; the river 
 shone softly through a rising mist ; I could see barges floating 
 with the stream, and two or three teams of horses on the 
 bank, while towards the east, the slanting beams of crane 
 stood out against the gray sky. In half an hour, all this had 
 died out ; there was but one patch of clear sky behind the Pan- 
 theon ; reddish-colored smoke was wreathing about in the dying 
 purple of the evening, and the vague colors intermingled. A 
 blue vapor hid the arches of the bridges and the edges of the 
 roofs. The apse of the cathedral stood alone, looking with 
 its pinnacles and jointed buttresses, in size and shape like an 
 empty crab-shell. Things prominent and colored but a mo- 
 ment ago, were now like mere sketches on a dull paper. Here 
 and there a gas-light shone out like a lonely star, and caught 
 the attention as other things faded away. Soon, strings of light 
 
 * 24th November, 1867.
 
 34 OF IMAGES. [BOOK II. 
 
 extended themselves as far as the eye could reach, and the in- 
 distinct flickering glare of crowded Paris rose in the west ; while 
 below the arches, along the quays, and over the weirs, the rip- 
 pling water kept up its nightly murmuring. 
 
 I saw this yesterday ; and now as I write I see it again 
 dimly, it is true, but still I see it. The colors, forms, sounds, 
 which struck me yesterday, are now renewed, or nearly so. 
 Yesterday, I experienced sensations excited by the immedi- 
 ate contact of things and immediate action of the nerves. 
 To-day impressions analogous to those sensations, though 
 remotely so, arise in me, notwithstanding the want of this ac- 
 tion and contact, notwithstanding the presence of other ac- 
 tions and contacts. It is a semirevival of my experience ; dif- 
 ferent terms might be used to express it, we might call it an 
 after-taste, an echo, a representation, a phantom, an image of 
 the primitive sensation ; it matters little ; all these compari- 
 sons mean -no more than that after a sensation excited by 
 the outer world, and not spontaneous, we find within us a 
 second event corresponding to it, which is spontaneous and 
 is not excited by the outer world, which resembles the sen- 
 sation, and is accompanied, though not so forcibly, with the 
 same emotions, which is pleasurable or the reverse, but in a 
 less degree, and is followed by some, but not all, the same 
 mental conclusions. The sensation repeats itself, though 
 with less distinctness and force, and deprived of many of its 
 surroundings. 
 
 This obliteration is more or less complete according to 
 the differences of men's minds, and this is what we mean 
 when we say that men have more or less memory. Again, 
 it is more or less complete in the same minds according to 
 the different kinds of sensations, and this is what is meant 
 by saying that such a man remembers forms, another colors, 
 another sounds. For example, in my own case, I have but 
 an ordinary memory for forms and a slightly better one for 
 colors. I can see without difficulty after several years five 
 or six fragments of an object, but not its precise and com- 
 plete outline ; I can recall more easily the whiteness of a 
 sandy path at Fontainebleau, the hundred little spots and 
 stripes made by the sprigs of wood strewed on it, its winding
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 35 
 
 curves, the faintly rose-colored tints of the heather by its 
 sides, the wretched appearance of a stunted birch clinging to 
 the side of a rock ; but I cannot trace in my mind the wind- 
 ing of the path or the jutting out of the rocks : if I mentally 
 catch sight of the swelling of some vegetable muscle my half- 
 sight stops there ; above, below, all is vague ; even involuntary 
 revivals, which are the most vivid, are only half clear to me ; 
 the most visible an most highly-colored fragment is dull and 
 tame. Compared to the sensation it is as a half-heard whis- 
 per to an articulate, ringing voice. In my case, all that is 
 reproduced uninjured and whole is the precise shade of emo- 
 tion, harsh, tender, strange, sweet, or sad, which followed 
 or accompanied the external corporeal sensation. I can thus 
 renew my pains and pleasures, the most complex and most del- 
 icate, with extreme exactness and after considerable distances 
 of time. In this respect, the incomplete and failing whisper 
 has almost the same effect as the voice. But if, instead of 
 taking the instance of a man inclined to pay principal at- 
 tention to sentiments, we look at men accustomed to observe 
 particular colors and forms, we shall find cases of images so 
 clear as to differ little from sensations. 
 
 For example, children accustomed to calculate in their 
 heads, write mentally with chalk on an imaginary board the 
 figures in question, then all their partial operations, then the 
 final sum, so that they see internally the different lines of 
 white figures with which they are concerned. The remarka- 
 ble children who are precocious mathematicians give a simi- 
 lar account of themselves.* Young Colborn, who had never 
 been at school, and did not know how to read or write, said 
 that when making his calculations, " he saw them clearly 
 before him." Another said that he "saw the numbers he 
 was working with as if they had been written on a slate. "- 
 So again, we find chess-players who play a game with their 
 eyes closed, and faces turned towards the wall. They have 
 numbered the squares and pieces; at each move of their op- 
 ponent they are told the piece moved and the new square it 
 occupies ; they give directions themselves for the movement 
 
 * Gall, " Fonctions du Cerveau," tome v. 130.
 
 36 OF IMAGES. [BOOK II. 
 
 of their own pieces, and go on in this way for many hours. 
 They often win, even when opposed to skilful players. Evi- 
 dently the figure of the whole chess-board, with the different 
 pieces in order, presents itself to them at each move, as in an 
 internal mirror, for without this they would be unable to fore- 
 see the probable consequences of their adversary's and their 
 own moves. 
 
 An American friend of mine, who has this faculty, de- 
 scribes it to me in these words : " When I am in my corner, 
 facing the wall, I see simultaneously the chess-board and all 
 the pieces, as they were in reality after the last move. And 
 as. each piece is moved, I see the whole chess-board with the 
 new change effected. If I am in doubt in my mind as to 
 the exact position of a piece, I play over, mentally, the whole 
 game from the beginning, attending carefully to the success- 
 ive movements of that piece. It is far easier to deceive me 
 when I watch the board than otherwise ; in fact, when I 
 am in my corner, I defy any one to mislead me as to the po- 
 tion of a piece without my afterwards detecting it I 
 
 see the piece, the square, and the color, exactly as the work- 
 man made them that is, I see the chess-board standing be- 
 fore my adversary, or at all events, I have an exact represen- 
 tation of it, and not that of another chess-board. So far is 
 this the case that, before retiring to the corner, I begin by 
 carefully looking at the chess-board and men as they stand, 
 and to this first impression I mentally attend and revert." 
 Usually, he does not see the table-cloth nor the shadows of 
 the pieces, nor the minute peculiarities of their make, but 
 can recall them if he wishes. He has often played chess 
 with a friend who has also this faculty, while walking along 
 the quays or in the streets. As might be expected, so exact 
 and intense a representation is repeated and lasts involunta- 
 rily. " I have never played a game," says he, " without 
 having played it over again four or five times in flie night in 
 bed, with my head on the pillow When I am sleep- 
 less and have unpleasant thoughts, I set myself to play at 
 chess, imagining a game, with all the pieces, and this occu- 
 pies my mind and drives away the besetting thoughts." 
 The first players are not the most skilful at this artifice. La-
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 37 
 
 bourdonnais could only play two games at once, mentally ; 
 having once attempted three at a time he died from the ef- 
 fort. " It is not unusual to find in clubs, fourth-rate players 
 who wake up some morning with this faculty." Some of 
 them attain an extent and clearness of imagination which 
 are simply marvellous. " Paul Morphy plays eight games at 
 a time, and Paulsens twenty. This I have seen myself." 
 Other images, far more irregular and with more variety of 
 shade, and so, it would seem, more difficult to recall, pre- 
 sent themselves with equal precision. Certain painters, 
 draughtsmen, and sculptors, after attentively considering a 
 figure, are able to draw it from memory. Gustave Ejore 
 has this faculty; Horace Vernet had it. Abercrombie* men- 
 tions a painter who copied from recollection and without the 
 aid of an engraving, a Martyrdom of Saint Peter, by Ru- 
 bens, with so perfect an imitation that the two pictures, be- 
 ing placed beside one another, considerable attention was re- 
 quired to distinguish the copy from the original. 
 
 We can follow the different stages by which the ordinary 
 image passes to this height of clearness and detail. In a school 
 of art at Paris, the pupils were practised in copying models 
 from memoiy. After four months' practice they said that " the 
 image " had become "much more distinct, and if it disappears 
 they can recall it almost at will." M. Brierre de Boismont,f 
 having studiously impressed on his mind the figure of a priest 
 of his acquaintance, says, " At present this mental representa- 
 tion is visible to me, whether my eyes be shut or open." The 
 image appeared to him " external," placed in front of him " in 
 
 the direction of the visual ray It has the size and 
 
 characters of the original; I can distinguish his features, the 
 cut of his hair, the expression of his face, his dress, and all the 
 details of his person. I see him smile, speak, preach ; I mark 
 
 even his habitual gestures The image is shadowy and 
 
 of a different nature from the objective sensation but 
 
 * ' Inquiries concerning the Intellectual, Powers," p. 126 ; and see Brierre de 
 Boismont, " Des Hallucinations," pp. 449 et seq., 26 et seq., where many analogous 
 cases are collected. See also " Annales Medico-Psychologiques," 3me Serie, ii. 295. 
 
 f Op. cit. 449 ; and De Boisbaudran, " Education de la Memoire Pittoresque," 
 
 pp. 77 and 83.
 
 38 OF IMAGES. [BOOK II. 
 
 clearly outlined and colored," and, saving this distinction of na- 
 ture, provided with all the characters belonging to the real per- 
 son, or, more precisely, with all the characters which belong to 
 the sensation experienced in the presence of the real person. 
 We may confidently assert then, that the internal event, which 
 we call a sensation, and which is produced in us when our 
 nerves, and consequently our brain, receive an impression from 
 without, is reproduced in us without impression from without 
 in the majority of cases partially, feebly, and vaguely, but in 
 many cases with greater clearness and force ; in some cases 
 with a precision and detail nearly equivalent to what we find 
 in the sensation. 
 
 The sensations of hearing, of taste, of smell, of touch, and, 
 in general, all sensations, whatever be the nerve by whose ac- 
 tion they are excited, have their images. We can all of us 
 hear tunes mentally, and in some cases the image is not far 
 removed from the sensation. Just now, thinking over a rep- 
 resentation of the " Prophet c" I repeated silently to myselt 
 the pastorale from the overture, and followed, I venture to 
 say almost felt, not only the order of the notes, their different 
 height, rests, and lengths, not only the musical phrase re- 
 peated as an echo, but also the keen, piercing tone of the 
 hautboy which plays it ; its sharp drawn-out notes of so rus- 
 tic a harshness that the nerves are startled, and filled with a 
 rough pleasure, as at the taste of raw wine. Every good musi- 
 cian experiences this sensation at will, when he follows the lines 
 of music covered with their black marks. The leader of an 
 orchestra,* questioned by M. Buchez, told him that when he 
 looked over a score " he heard as in his ear " not only the 
 chords and their succession, but also the tone of the instru- 
 ments. On the first reading over, he distinguished the quartet ; 
 at the second and succeeding ones, he added to the quartet 
 the other instruments ; and finally he perceived and appre- 
 ciated distinctly the effect of the whole. Great musicians 
 have this gift of internal hearing in an eminent degree. It 
 is well known that Mozart, having twice heard the Miserere of 
 the Sistine Chapel, wrote it down entirely from memory. As 
 
 * Brierre de Boismont, op. cit. 459.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 39 
 
 it was forbidden to copy it, the fidelity of the master of the 
 chapel was suspected, on account of the difficulty of the ex- 
 ploit.* Mozart, no doubt, on his return home, found in his 
 mind, when seated at his table, as if in a minutely exact 
 echo, these lamentations composed of so many parts and 
 carried over a series of notes so strange and delicate. When 
 Beethoven composed many of his great works after he had be- 
 come completely deaf, the combinations of notes and tones 
 which we now admire in them were present to him. They 
 were necessarily present, since he measured their effect be- 
 forehand, and measured it with rigorous precision. 
 
 II. This close resemblance of the image and sensation be- 
 comes clearer still if we consider the circumstances under which 
 the higher degrees of intensity of the image occur. A first ex- 
 citant is the extreme nearness of the sensation. When we have 
 heard a full striking tone, for example, the rich prolonged note 
 of the violoncello, clarionet, or horn, if the sound suddenly 
 ceases, we continue for some seconds to hear it mentally ; and, 
 though at the end of these seconds its image becomes feeble 
 and obscure, we continue, if we derived any pleasure from it, 
 to repeat it internally with remarkable fidelity, and without 
 letting go any 'portion scarcely of smooth or striking sound. 
 And so, when we shut our eyes after having regarded attentive- 
 ly any object, a figure in a print, the back of a book in a library, 
 the perception, which has become internal, continues for nearly 
 a second, then disappears, then renews itself, but softened ; 
 then is troubled and fails utterly, without leaving any other 
 trace than a vague outline ; and the losses which the image 
 has undergone prove by their contrast the force it had to com- 
 mence with. So it is after a smell, a taste, an impression of 
 cold, of heat, of local pain, and the rest. If the sensation, in- 
 stead of preceding, is about to follow, the effect is the same. 
 A gourmand seated before a savory dish, the steam of which 
 is rising under his nose, and into which he has already put his 
 fork, tastes beforehand its exquisite flavor, and the glands of 
 his tongue become moistened ; the image of the expected fla- 
 
 * It is necessary to have heard this Miserere, to appreciate the capacity and 
 precision of such memory for music.
 
 40 OF IMAGES. [BOOK II. 
 
 vor is equivalent to the sensation of the actual flavor ; the resem- 
 blance is carried so far that the salivary glands are equally ex- 
 cited in either case. This is why a physiologist, who wishes 
 to obtain a quantity of saliva to experiment with, ties up a 
 hungry dog a few inches from a piece of meat, and collects the 
 liquid which the flavor continually wished for and continually 
 absent discharges from the animal's jaws. So by an analogous 
 but contrary effect, any thing unpleasant we are obliged to take 
 excites vomiting by the simple thought of its taste before it 
 touches our lips. So again, a ticklish person whom we threaten 
 to tickle, and who sees our hand approaching, imagines so 
 strongly the coming sensation, that he has spasmodic feelings, 
 the same feelings, in fact, as if the sensation had taken place. 
 Many persons who are about to undergo a surgical operation, 
 feel beforehand the shooting pain which will follow the first 
 cut, and sweat and grow pale at the very thought, and some- 
 times suffer as keenly as when under the saw and knife. A 
 lady* who thought she was inhaling nitrous oxide, and who 
 had simply a bottle of common atmospheric air under her nose, 
 fell in a fainting fit. These examples show us also that the im- 
 portance of the sensation is another excitant as powerful to 
 strengthen the image as the proximity of the sensation. A 
 traveller in Abyssiniaf saw one of his men torn by a lion ; many 
 years afterwards, when he thought of the circumstance, he could 
 hear mentally the cries of the unhappy man, " and felt as if a 
 hot iron were entering his ear." Numbers of mystics:}: have 
 represented to themselves the passion of our Lord with such 
 force, that they have believed themselves to feel in their bodies 
 the rending and pain of the Saviour's wounds. Every one 
 knows the power of an image, especially when strange and ter- 
 rible, upon an excited and prepared mind : it is mistaken for a 
 sensation, and the illusion is complete. Children, and even 
 grown men, have fallen insensible before a figure, or even a cloth, 
 which they have believed to be a ghost. On recovering, they 
 have asserted that they saw flaming eyes, open jaws. In all 
 these cases the image has in no way differed, for the time at 
 
 * Mueller, " Elements of Physiology, " tr. Baly, ii. 1392. 
 
 f Brierre de Boismont, op. cit. 468. 
 
 \ Maury, " La Magie et 1'Astrologie, etc.," 2me partie, chap. iii. passim.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES, ^i 
 
 least, from the corresponding sensation, and it is only after the 
 lapse of a longer or shorter time, when the recollection has sub- 
 sided, and the circumstances have been looked into, that the 
 deceived person has recognized his mistake. 
 
 III. Hitherto we have seen the image approximating to 
 the sensation, acquiring the same clearness, the same abun- 
 dance of minute and circumstantial detail, the same force, 
 sometimes even the same persistence, furnishing the same 
 foundation for higher combinations and ulterior reasonings, 
 exciting the same impressions and same instinctive actions, 
 organic and muscular, having in short the same properties, the 
 same accompaniments, and same consequents as the sensa- 
 tion, without, however, being wholly and definitely confound- 
 ed with it. In fact, there remains a character which is dis- 
 tinctive to the image : we soon recognize it as internal, we 
 say to ourselves, at least after a moment, that the thing thus 
 sent or felt is but a phantom ; that our hearing, our sight, our 
 taste, or our smell, have experenced no real sensation. We are 
 not under the influence of hallucinations ; we do not say as 
 sick people sometimes do* " I saw and heard it as plainly as I 
 
 now see and hear you I assure you that what I 
 
 saw was as clear as the day ; and, if I doubt it, I must also 
 doubt that I see and hear you." 
 
 To explain so important a difference, we must observe 
 closely in what the recognition of an illusion consists. There 
 are two moments during the presence of the image ; one affirm- 
 ative, the other negative ; the second partially qualifying what 
 the first began to affirm. In the case of a very precise and in- 
 tense image, these two moments are very distinct : at the 
 first it seems external, situated at such and such a distance 
 from us, when a sound or visible object is in question ; situ- 
 ated in our palate, nose, or limbs, when a sensation of smell, 
 taste, local pain or pleasure is in question. " The exercise 
 both of conception and imagination,"! savs Dugald Stewart, 
 " is always accompanied with a belief (at all events, momenta- 
 ry) that their object exists There are few persons 
 
 who can look down from the battlements of a very high tower 
 
 * Baillarger, " Des Hallucinations," 374. 
 
 f " Philosophy of the Human Mind," chap. 3, i. 150-1. Ed. Hamilton.
 
 42 OF IMAGES. [BOOK II. 
 
 without fear, while their reason convinces them that they are 
 in no more danger than when standing on the ground." In 
 fact, when we look directly down to the ground, we imagine 
 ourselves suddenly taken and thrown to the bottom ; and 
 this image alone is enough to make us shudder, since, for an 
 imperceptible instant, it has the force of a belief; we draw 
 back instinctively, as if we actually felt ourselves falling. We 
 must admit, then, that " whenever the objects of imagination 
 engross the attention wholly, they produce a temporary be- 
 lief of their reality." This is why persons who experience 
 very vivid images employ, to describe them, the same words 
 as to denote the actual sensation ; and, during some seconds, 
 take their images for sensations. " I once heard," says Lie- 
 ber, " a colored preacher describing the torments of future 
 punishment. He rose, not ineloquently, from the description 
 of one anguish to another, when at last, carried away by un- 
 controllable excitement, he merely uttered, for more than a 
 minute, a succession of inarticulate sounds or cries."* No 
 doubt, during the minute in question, his mental vision had 
 all the characters of physical vision. He had before him an im- 
 aginary hell resembling a real hell, and he believed in his in- 
 ternal phantoms as in real facts. " My imaginary persons," 
 writes the clearest and most accurate of modern novelists, 
 " affect me, pursue me, in fact, I live in them. When I was de- 
 scribing the poisoning of Emma Bovary I had so strong a taste 
 of arsenic in my mouth, I was myself so far poisoned, that 
 I had two consecutive fits of indigestion, and real indigestion, 
 for I threw up my dinner." 
 
 An English painter, f whose rapidity of execution was mar- 
 vellous, explained his mode of work in this way ; " When a 
 sitter came, I looked at him attentively for half an hour, sketch- 
 ing from time to time on the canvas. I wanted no more I put 
 away my canvas, and took another sitter. When I wished to 
 resume my first portrait, / took the man and sat him in the 
 chair, where I saw him as distinctly as if he had been before 
 me in his own proper person I may almost say more vividly. I 
 
 * " Smithsonian Contributions to Knowledge," vol. ii. p. 9. 
 
 f Wigan, " A New View of Insanity. The Duality of the Mind, etc.," p. 124.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 43 
 
 looked from time to time at the imaginary figure, then worked 
 with my pencil, then referred to the countenance, and so on, 
 just as I should have done had the sitter been there when 
 I looked at the chair I saw the man. Gradually I began to 
 lose the distinction between the imaginary figure and the real 
 person ; and sometimes disputed with sitters that they had 
 been with me the day before. At last I was sure of it; 
 
 and then all is confusion I lost my senses, and was 
 
 thirty years in an asylum." When he left the asylum he 
 had still the power of painting a portrait from his internal 
 image of the model, but was persuaded not to work for fear 
 of a return of the madness. 
 
 The chess-player I have mentioned, writes again : " I never 
 think of distinguishing between my mental chess-board and 
 the actual one. As far as I am concerned, they are one ; and I 
 could only establish a distinction between them by an effort 
 of reasoning, the utility of which I have never experienced." 
 Thus, while he is playing, his mental chess-board stands to him 
 in place of the actual one. In other cases, morbid or quasi- 
 morbid, we see the image acquire complete and definite ex- 
 ternality. " Recently," says M. Maury,* " my eyes were at- 
 tracted by a dish of very scarlet cherries which were served at 
 my table. Just after dinner, the weather grew stormy, and the 
 air very close ; I felt sleep coming over me, my eyes closed ; I 
 was then thinking of the cherries, and saw in a sleepy halluci- 
 nation these same scarlet cherries, lying on the same green 
 porcelain dish on which they had appeared at dessert. Here 
 was a direct transformation of my thought into sensation." 
 Writers on insanity mention many instances of similar trans- 
 formations, f " A young man who suffered from epilepsy, 
 every fit of which was preceded by the apparition of an indented 
 wheel, with a horrible figure in the middle, assured me that 
 he had the power of producing hallucinations. He amused 
 himself by conceiving some strange object to be present ; 
 
 * " Le Sommeil, et les reves," 240. 
 
 f " Annales Medico-Psychologiques," 3me Serie, ii. 389, 390, M. Michea Cases 
 collected by Abercrombie, M. Moreau, Maisonneuve, etc. See also, Baillarger, 
 " Des Hallucinations," " Memories de 1'Acadumie de Medecine," tome xiii. p. 
 250.
 
 44 OF IMAGES. [BOOK II. 
 
 and scarcely had he formed it in imagination before it ap- 
 peared accurately before his eyes. I have myself seen an in- 
 stance of this kind in a monomaniac, a man of cultivated mind 
 and perfect sincerity of character, who assured me that he 
 had but to recall to his mind or to imagine a person or thing, 
 for the person or thing to appear at once before him with 
 every appearance of externality." 
 
 There is no need to be ill or half asleep to watch the met- 
 amorphosis by which the image projects itself from within to 
 an external position. " A friend of mind," says Abercrombie,* 
 " had been one day looking intensely at a small print of the 
 Virgin and Child, and had sat bending over it for some time. 
 On raising his head he was startled by perceiving at the farther 
 end of the apartment a female figure of the size of life, with a 
 child in her arms. The first feeling of surprise having sub- 
 sided, he instantly traced the source of the illusion, and re- 
 marked that the figure corresponded exactly with that which 
 he had contemplated in the print. The illusion continued 
 distinct for about two minutes. "f Goethe was able to pro- 
 duce in himself a complete illusion at will. "When I closed 
 my eyes," he says, " and depressed my head, I could cause 
 the image of a flower to appear in the middle of the field of 
 vision ; this flower did not for a moment retain its first form, 
 but unfolded itself, and developed from its interior new flow- 
 ers, formed of colored or sometimes green leaves. These 
 were not natural flowers, but of fantastic forms, although sym- 
 metrical as the rosettes of sculptors. I was unable to fix any 
 one form, but the development of new flowers continued as 
 
 * Op. cit. p. 63. 
 
 f Griesinger, "Traite des Malades Mentales" (translation by Doumic), p. 104 : 
 " Some observers are able to produce hallucinations at will ; that is to say, ideas 
 existing in their consciousness, and on which they firmly direct their attention, call 
 into play the sensorial functions. A person who suffered from hallucinations of 
 hearing observed that he could produce the voices himself, and said afterwards that 
 this partly assisted him in recognizing the error. M. Sandras speaks of hallucina- 
 tions he himself suffered from during an illness in which he mistook his own thoughts 
 and wishes for voices. These voices answered his mental questions as a person pres- 
 ent would have done, but always in accordance with his wishes. 
 
 " We consider the phenomena of imagination as among the functions of the inter- 
 nal sensorial apparatus, and as differing from its other functions in intensity only."
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. A? 
 
 long as I desired it, without any variation in the rapidity of 
 the changes. The same thing occurred when I figured to my- 
 self a variegated disk. The colored figures upon it under- 
 went constant changes, which extended progressively, from 
 the centre towards the periphery, exactly like the changes in 
 the modern kaleidoscope." Finally, hallucinations, that is to 
 say, projections into the outer world of simple mental im- 
 ages, have been produced, not only in full health, but with 
 the complete exercise, and, indeed, by the exercise of the will. 
 " A German writer on insanity, Dr. Brosius, of Bendorf, men- 
 tions his having produced at will his own figure, which stood 
 before him for some seconds, but which vanished immediate- 
 ly he attempted to fix his mind on his personal existence."* 
 
 These ^extreme cases show by their exaggeration the na- 
 ture of the normal state. Just as by dissecting an hypertro- 
 phied stomach we succeed in distinguishing dispositions of the 
 muscular fibres which are invisible in a healthy stomach, so 
 by examining prolonged illusions, which lasts for seconds, 
 minutes, or more, we discover the existence of fugitive illu- 
 sions, accompanying ordinary images, but so rapid, short, and 
 instantaneous, that we cannot isolate or observe them directly. 
 This illusion is none the less real, and the simple analysis 
 of the words we use to denote the image bears witness to the 
 double operation by which it is formed. We say that such 
 an image, a phantom of hearing or sight, of taste or smell, 
 which seems to be situated either in some part of our or- 
 gans, or without us, seems, erroneously, to be situated there, 
 since it is not there or without us, but internal. This phrase 
 itself indicates the recognition and correction of an error, 
 therefore of a preliminary error; we must have been deceived, 
 for the moment, since, a moment afterwards, we find out 
 the mistake. The two operations, illusion and its rectifica- 
 tion, follow so closely that they are confused into one. But 
 suppress the rectification, the first operation, illusion, will alone 
 
 * " Annales Medico-Psychologiques," ibid. I have myself had, in a dream it is 
 true, a vision of this kind (November, 1869). At the end of a dream, too long for 
 narration, my own figure appeared seated in an arm-chair near a table, in a white 
 dressing-gown striped with black ; it turned towards me, and the shock was so 
 great that I woke up with a start.
 
 46 OF IMAGES. [BOOK II. 
 
 remain, and its unaccustomed presence, when the couple is 
 dissolved, will show us its fugitive presence in the couple 
 when intact. 
 
 IV. This leads us to the consideration of cases in which the 
 rectification cannot be effected. What usually effects it is the 
 presence of a contradictory sensation. When the chess-play- 
 er imagines a black and white chess-board two paces in front 
 of him, and a moment afterwards his open eyes give him the 
 sensation of a gray or dark wall at the same distance, and in 
 the same direction, the sensation and image cannot co-exist. 
 When the novelist imagines the crushing of moistened arsen- 
 ic in his mouth, and " the horrible inky taste " which the poi- 
 son leaves, if, a moment afterwards, he takes a mouthful of 
 wine or a lump of sugar, the real and imaginary sensations ex- 
 clude one another, and the momentary illusion caused by 
 the image disappears under the ascendancy of the sensation. 
 And thus it is that in most instances the passing error, con- 
 nected for a moment with the presence of the image, disap- 
 pears, if not at the same instant, without any appreciable in- 
 terval elapsing, by the opposing shock of the real sensation. 
 Let us look, then, for a case in which the sensation disap- 
 pears and becomes as it were absent ; we find such a case in 
 the reverie preceding sleep.* The sensations produced in 
 us by the external world are then effaced by degrees ; at last 
 they seem suspended, and the images, no longer distinguished 
 from sensations, become complete hallucinations. M. Maury 
 succeeded, by having himself awakened at intervals, in observ- 
 ing a great number of them : for example, once, when sudden- 
 ly roused up, " I saw my name very distinctly on a sheet of 
 white paper, shining like the very smoothest English paper." 
 He seated himself again in his easy-chair. " My head had 
 scarcely sunk down before the hallucination returned ; but 
 now, instead of my name, I saw Greek letters and words which 
 I spelt out mechanically, and almost with a movement of the 
 lips. On several successive days I had, whether in bed or my 
 
 * Maury, " Annales Medico-Psychologiques," 3me Serie, iii. 161. And "Le 
 Sommefl et les Reves," chap. iv. M. Maury was the first to show, by a well-con- 
 nected series of experiments, the near relationship of the sensation, the recollec- 
 tion, the image, and the hallucination.
 
 CHAP L] NATURE AND REDUCTION OF IMAGES. 
 
 47 
 
 chair, similar hallucinations or real dreams, in which I appeared 
 to be reading Oriental characters. This reading of a word here 
 and there was always accompanied by a feeling of fatigue in 
 the eyes. . . . Once, above all, I saw Sanscrit characters 
 ranged in columns, according to the classification of gramma- 
 rians, and these letters had a relief and a brilliancy which tired 
 me. It must be observed that I had for some days been read- 
 ing a number of grammars of Asiatic languages, and that the 
 fatigue of my eyes was partly owing to this prolonged reading." 
 Here we not only have the image which has become an hallu- 
 cination,* but we see it in process of becoming such. We can 
 watch the progressive diminution of the sensation which 
 would contradict it, the suppression of the rectification which 
 w r ould pronounce it internal, and the increase of the illu- 
 sion which causes us to take the phantasm for a real object.f 
 I know this state from my own experience, and have many 
 times repeated the observation, above all in the daytime, when 
 fatigued and seated in a chair ; it is then sufficient for me to 
 close one eye with a handkerchief; by degrees the sight of the 
 other eye becomes vague, and it closes. By degrees, all exter- 
 nal sensations are effaced, or cease, at all events, to be remark- 
 ed ; the internal images, on the other hand, feeble and rapid 
 during the state of complete wakefulness, become intense, dis- 
 tinct, colored, steady, and lasting ; there is a sort of ecstasy, 
 accompanied by a feeling of expansion and of comfort. Warn- 
 ed by frequent experience, I know that sleep is coming on, and 
 that I must not disturb the rising vision ; I remain passive ; 
 and, in a few minutes it is complete. Architecture, landscapes, 
 moving figures, pass slowly by, and sometimes remain, with 
 incomparable clearness of form and fulness of being ; sleep 
 comes on, and I know no more of the real world I am in. Many 
 times, like M. Maury, I have caused myself to be gently 
 roused at different moments of this state, and have thus been 
 
 * Brierre de Boismont, op. cit. 160. Mile. R., after a series of hallucinations' 
 " characterized very clearly the state she had gone through. She could best com- 
 pare it, she said, to an unpleasant dream." Many sufferers from hallucinations 
 have said the same, on their recovery. The analogy between dreams and hallu- 
 cinations is certain. See Maury, ibid. chap. vi. 
 f Mueller, Physiology, tr. Baly, ii. 1394.
 
 48 OF IMAGES. [BOOK II. 
 
 able to mark its characters. The intense image which seems 
 an external object is but a more forcible continuation of the fee- 
 ble image which an instant before I recognized as internal ; 
 some scrap of a forest, some house, some person which I vaguely 
 imagined on closing my eyes, has in a minute become present to 
 me with full bodily details, so as to change into a complete hallu- 
 cination.* Then, waking up on a hand touching me, I feel th. 
 figure decay, lose color, and evaporate ; what had appeared 
 a substance is reduced to a shadow. I have frequently 
 thus watched in turn the filling out by which a simple image 
 becomes an hallucination, and the obliteration which turns the 
 hallucination into a simple image. In this double transition 
 we are able to notice the differences, and perceive the condi- 
 tions, of the two states. 
 
 First, when we are going to sleep. As the image becomes 
 more intense so it becomes more absorbing and independ- 
 ent. On the one hand, it attracts by degrees all the atten- 
 tion ; external noises and contacts become less and less sensi- 
 ble ; at last they are as if they did not exist. The image, on 
 the other hand, becomes prominent and persistent ; we seem 
 no longer actors, but spectators ; its transformations are spon- 
 taneous and automatic^ When attention and automatism 
 are at their height, the hallucination is complete, and it is pre- 
 cisely by the loss of these two characters that it is destroyed. 
 - Next, as to waking. On the one hand, at the light touch 
 that arouses us, a part of our attention is brought back to the 
 outer world. On the other hand, as memory returns, reviving 
 images and ideas surround with their train the special image, 
 they come into conflict with it, assume ascendancy over it, 
 depose it from its solitary position, restore it to social life, 
 and replace it in its habitual dependency. This opposition 
 
 * Maury, " Le Sommeil," 3^6 edition, pp. 448 and 453. Many instances are 
 cited in support of this. " As soon as the mind rests on an idea, a corresponding 
 
 hypnogogic hallucination is produced, if the eye he closed The state of 
 
 hallucination is nothing more than an intensity of the image-idea, owing to the 
 internal parts of the sensorial apparatus having become more delicate and more 
 readily excitable, and consequently undergoing, in the operation of conception 
 a more vigorous shock than in the healthy state a shock, however, of the same 
 naJiire as that which accompanies though*. 
 
 f An expression of M. Baillarger.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 
 
 49 
 
 and contention cause the stupefaction of waking, and what 
 we call being thoroughly awake is but the re-establishment 
 of equilibrium. 
 
 The ordinary image then is not a sjmple, but a double fact. 
 It is a spontaneous consecutive sensation, which, by conflict- 
 ing with another sensation, primitive and not spontaneous, 
 undergoes lessening, restriction, and correction. It comprises 
 two momentary stages, a first in which it seems localized 
 and external, and a second in which this externality and sit- 
 uation are lost. It is the result of a struggle ; ,its tendency to 
 appear external is opposed and overcome by the stronger 
 .and contradictory tendency of the sensation occasioned at the 
 same moment by the action of the nerve. Under this ef- 
 fort it grows weak and thin, it is reduced to a shadow ; we 
 call it an image, phantasm, or appearance, and, however vivid 
 or clear it may be, the conjunction of this negation is suffi- 
 cient to deprive it of its substance ; to dislodge it from its ap- 
 parent position, and to distinguish it from the true sensation. 
 
 But to take the inverse case ; it is allowed that not only in 
 sleep but when awake, and for instance in a state of ecstasy or 
 in the heat of action, though the nerve be excited, the sensa- 
 tion may be absent or as if absent, that is to say, not ob- 
 served, annulled by the presence and preponderance of some 
 other idea, image, or sensation. Such instances are by no 
 means rare. At the bombardment of St. Jean d'Ulloa, the 
 Mexicans fired a number of shot into a French vessel. A 
 sailor called out "All right! No harm's done." The next 
 minute he fell, fainting ; a ball had broken his arm ; at the 
 moment he did not feel it.* So too in a calmer state, we 
 may find sensations or fragments of sensations which are de- 
 stroyed and no longer capable of contradicting the image. 
 The image will then appear localized and external ; and, though 
 pronounced illusory by surrounding ideas, will continue to ap- 
 pear localized and external, since the sensation which could 
 alone deprive it of this character is wanting, or is as if it did 
 not exist. The hallucination is then complete, and what makes 
 it so is the annulling the only sensation or fragment of 
 
 * This fact wa"s told me by an eye-witness. 
 4
 
 5Q OF IMAGES. [BOOK II. 
 
 sensation capable of reducing it. When a man under an hal 
 lucination, with his eyes open, sees three feet from him the 
 figure of a man where there is really a mere wall covered 
 with gray paper with green stripes, the figure covers a por- 
 tion of this wall and renders it invisible to him ; the sensations 
 which this portion ought to excite are then non-existent ; but 
 nevertheless the retina, and probably the optic centres, are 
 excited in the ordinary manner by the gray and green stripes. 
 In other words, the preponderating image annuls the portion of 
 sensation which would contradict it. If, as it often happens, 
 the figure moves, the preponderating image, as it advances 
 and covers each portion of the wall, is continually blotting out 
 and exposing in turn distinct fragments of sensation. Reason 
 is not wanting in such cases; for often when in this state 
 the mind remains sound and the patient knows that the fig- 
 ure is not real ; it is the special reductive, that is to say, the 
 contradictory sensation, which fails in the conflict, and, in- 
 stead of depriving the image of its externality, becomes itself 
 effaced. 
 
 Accidents of this kind are frequent when one of the senses 
 has been greatly fatigued. " It is well known that persons who 
 are in the habit of using the microscope sometimes find objects 
 which they have been examining for a long time re-appear spon- 
 taneously some hours after they have left their work."* M. 
 Baillarger having worked some hours daily for several days, at 
 preparing specimens of brains with fine gauze, " saw all at once 
 
 gauze continually covering the objects in front of him 
 
 And this hallucination was repeated for several days." Here, 
 it is evident the special reductive was wanting ; in other words, 
 the retina having before it a green carpet, or red chair, certain 
 lines of green or of red, while producing on it their ordinary 
 physical effect, excited only a sensation amounting to nothing. 
 For this reason, a German physiologist, Gruithuisen,* who has 
 observed his own hallucinations with great accuracy, affirms 
 that he saw floating images cover the furniture of the room he 
 was in. 
 
 Other cases show the partial re-establishment of the correct- 
 
 Baillarger, " Des Hallucinations," 460. ' \ Ibid., 333, 334.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. rj 
 
 ive sensation, A person, mentioned by Sir Walter Scott,* 
 saw a skeleton at the foot of his bed. His doctor, wishing to 
 convince him of his error, placed himself between the patient 
 and the place assigned to the spectre. The patient then pro- 
 fessed that he could not see the body of the skeleton, but that 
 its skull was peering over the doctor's shoulder. This is why 
 solitude, silence, obscurity, the want of attention, all circum- 
 stances, in short, which suppress or diminish the corrective sen- 
 sation, facilitate or provoke the hallucination ; and reciprocally, 
 company, light, conversation, aroused attention, all circumstan- 
 ces giving rise to, or augmenting, the corrective sensation, de- 
 stroy or weaken the hallucination. f " If we approach a patient 
 suffering under hallucinations of hearing, and speak to him so as 
 to fix his attention, we can convince him that his pretended in- 
 visible interlocutors are silent while the conversation lasts . . ." 
 A patient observed by M. Lelut, at the hospital of the Bicetre," 
 " ceased to have hallucinations when changed into another 
 ward and with different neighbors. But this suspension last- 
 ed only a few days ; the patient soon became accustomed to 
 the new circumstances in which he found himself, and then 
 fell again into false perceptions .... With one patient there 
 must be very keen impressions, uninterruptedly kept up, to 
 suspend the hallucinations even for a short time. Scarcely is 
 the sick man left to himself, scarcely have you ceased to excite 
 him, when the phenomena recur. With others, on the con- 
 trary, the visit of the doctor to the ward is enough to cause a 
 considerable suspension." When M. Baillarger saw objects 
 covered with gauze " it was principally in the dark, and when 
 my attention was not engaged.":}: The same observer, hav- 
 ing taken haschich, could not get rid of his hallucinations 
 while in the dark, and was compelled to light a candle. Many 
 patients who see in the dark various frightful figures, dying 
 persons, corpses, etc., are freed from their visions as soon as 
 
 * " Demonology and Witchcraft," p. 27. 
 
 f Baillarger, ibid., 440 ; and Brierre de Boismont, op. cit., 388. " Those nightly 
 apparitions, which I called silly illusions by day, became frightful realities to me in 
 the evening," p. 388. " It constantly happened that the entrance of the servant 
 freed her from the presence of the phantoms," p. 242. 
 
 \ Ibid., 328, 329, 330, 444, 445.
 
 52 OF IMAGES. [BOOK II. 
 
 a light is brought into the room, A lady with whom this is 
 the case has been obliged for twenty years to have a light near 
 her when asleep. An old servant, M. G., " as soon as she 
 closes her eyes, sees animals, houses, meadows, etc. I have 
 frequently myself pressed down her eyelids, and she described 
 at once a crowd of objects which appeared to her." With 
 some people, to enter a dark room is enough to produce hal- 
 lucinations. " It is not then uncommon," says Mueller,* " to 
 find distinct images of landscapes and similar objects floating 
 before the eyes. I have been very subject to this phenome- 
 non, but have got into the habit, whenever it occurs, of open- 
 ing my eyes at once, and fixing them on the wall. The im- 
 ages still persist, but soon grow pale. They are seen which- 
 ever way the head is turned." Here the remedy is obvious ; 
 it consists in arousing a contradictory sensation. The phan- 
 tom grows pale, and loses its externality in proportion as the 
 sensation of color excited by the wall becomes more clear and 
 preponderant. And the remedy is general ; every shock that 
 brings back the attention to real sensation ; a cold bath, a 
 douche, the arrival of an unexpected or important person, 
 draws them from their indistinctness and nullity, re-establish- 
 es them more or less, and for a longer or shorter time, and 
 consequently revives with them the particular sensation which 
 is the special reductive of that illusion. 
 
 " In the summer of i832,t a gentleman in Glasgow, of 
 dissipated habits, was seized with cholera, -from which he re- 
 covered. His recovery was unattended with any thing par- 
 ticular, except the presence of phantasmata consisting of 
 human figures about three feet high, neatly dressed in pea- 
 green jackets, and knee-breeches of the same color. Being a 
 person of a superior mind, and knowing the cause of the illu- 
 sions, they gave him no alarm, although he was very often 
 haunted by them. As he advanced in strength the phantoms 
 appeared less frequently, and diminished in size, till at last 
 they were not taller than his figure. One night, while seated 
 alone, a multitude of these Lilliputian gentlemen made their 
 appearance on his table, and favored him with a dance ; but 
 
 * Op. cit.,tr. Baly, ii. 1394. f Macnish, " Philosophy of Sleep," p. 290.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 53 
 
 being at the time otherwise engaged, and in no mood to en- 
 joy such an amusement, he lost temper at the unwelcome in- 
 trusion of his pigmy visitors, and striking his fist violently on 
 the table, he exclaimed, in a violent passion, ' Get about your 
 business, you little impertinent rascal ! What the devil are you 
 doing here ?' when the whole assembly instantly vanished, 
 and he was never troubled with them more." The illness was 
 drawing to a close, and his lively feeling of anger, together 
 with the violent sensation of the blow on the table, suddenly 
 restored their normal preponderance to the visual sensations 
 which the portion of the table covered by the Lilliputians 
 ought to have given him, but had ceased to give. 
 
 Other cases show with fuller detail how it is the corrective 
 sensation leaves the sides, and appears on the scene. Nicolai,* 
 the bookseller and academician of Berlin, having suffered 
 from considerable vexations, and a periodical blood-letting to 
 which he was accustomed having been omitted, tells his story 
 thus : " On the 24th of February, 1791, having had a violent 
 altercation, I saw on a sudden, about ten paces from me, the 
 
 figure of a corpse The apparition lasted eight minutes. 
 
 At four in the afternoon, the same figure re-appeared 
 
 At six, I distinguished several figures having no connexion 
 with the first. . . . On the following day, the figure of the 
 corpse disappeared ; it was replaced by other figures, sometimes 
 
 representing friends, but more frequently strangers. 
 
 These visions were as clear and distinct in solitude as in com- 
 pany, by day as by night, in the streets as in my own house ; 
 only they ivere less frequent when in strange houses." They 
 represented men and women walking as if on business, then 
 persons on horseback, dogs, and birds. There was nothing 
 particular in their looks, stature, or dress, " but they were a 
 little paler than in real life"\ At the end of four weeks, 
 
 * Brierre cle Boismont, op. cit. 33, citing from Berliner Monats-sclnift. 1799. 
 Mai. 
 
 f M. Brierre cle Boismont (op. cit. 240) gives an account of a person who, dur- 
 ing an attack of pneumonia, had hallucinations of this kind, while preserving, like 
 Nicolai, all his reason. 
 
 " Sometimes these figures presented themselves suddenly, but more frequently 
 did not become distinguishable till after an interval, as though they had passed
 
 54 OF I iMAGES. [BOOK II. 
 
 their number increased ; they began to talk to one another, 
 and sometimes to address him, usually in pleasing language. 
 He distinguished clearly these involuntary hallucinations from 
 voluntary images. When certain figures he was acquainted 
 with had thus passed before him, he determined to attempt 
 to reproduce them mentally. " But," says he, " while seeing 
 distinctly in my mind two or three of them. I could not succeed 
 
 in making the internal image external On the othei 
 
 hand, some time after, I perceived them afresh when I was not 
 thinking of them." The special reductive was wanting in the 
 hallucination ; on the other hand, it was at work in the case 
 of ordinary attention, and simply because the degree of atten- 
 tion was ordinary. In the first case, the image arising of its 
 own accord, spontaneously, without visible connexions or ante- 
 cedents, and with personal automatic power, destroyed the 
 special reductive. In the second case, the image arising by an 
 effort of the balanced group of ideas and desires which we term 
 ourselves, allowed the special reductive to do its work. After 
 about two months, leeches were applied to the patient to make 
 up for the omitted bleeding, and he found his normal sensations 
 reappear, not all at once, but by portions and degrees. " Dur- 
 ing the operation," says he, " my room was filled with human 
 figures of all kinds. This hallucination lasted uninterruptedly 
 from eleven in the morning to half-past four, just when my di- 
 gestion was commencing. I then perceived the movements 
 of the phantoms getting slower. Soon afterwards they began 
 to grow pale : at seven they had a whitish look, they moved 
 very slowly, though their outlines were as distinct as before. 
 By degrees they became misty and appeared to dissolve into air, 
 whilst certain portions of them remained still visible during a 
 considerable time. At about eight o'clock, the room was 
 quite clear of these fantastic visitors." 
 
 When we are suddenly roused from sleep in the midst of 
 a vivid dream, we experience an impression like this, though 
 
 through a mist before showing themselves distinctly. Each figure remained visi- 
 ble five or six seconds, then disappeared, getting feebler by degrees till nothing 
 remained but an opaque dull cloud, from the midst of which another figure imme- 
 diately appeared."
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 
 
 55 
 
 of far shorter duration. In such a case, I have often seen, for 
 a passing moment, the image groivpale, waste away, and evap- 
 orate ; sometimes, on opening the eyes, a fragment of landscape 
 or the skirt of a dress appears still to float over the fire-irons or 
 on the black hearth. So, while Nicolai was recovering, the 
 parts of the wall or furniture covered by the phantoms succeeded 
 by degrees in producing their normal effect. The sensation 
 which they would naturally excite by their action on the nerve, 
 and through that on the brain, is no longer paralyzed. At 
 first., this sensation recovers a portion of its strength, and con- 
 tends on equal terms with the image ; for the phantom, if still 
 present, is misty, and the furniture or wall is vaguely apparent 
 behind it. Soon, a fragment of the sensation regains all its 
 preponderance ; a leg or the head of a phantom disappears 
 owing to the reappearance of the portion of furniture which 
 it hid. Then, the whole sensation finds itself restored and 
 complete, the phantoms have vanished, and all that remains 
 of them is the internal image which enables us to describe 
 them. 
 
 Here we see very clearly the connexion of the image and 
 sensation ; it is an antagonism, such as is met with between two 
 groups of muscles in the human frame. In order that the 
 image may produce its normal effect, that is to say, may be rec- 
 ognized as internal, it must undergo the counterpoise of a sen- 
 sation ; and if this counterpoise is absent, it will appear exter- 
 nal. Similarly, in order that the muscles on the left of the 
 face or tongue may produce their normal effect, the corre- 
 sponding muscles on the right must be intact. In the absence 
 of this counterpoise, the face or tongue are drawn towards the 
 left. The paralysis of the muscles of one side produces a de- 
 formation of the other, as the weakening or extinction of the 
 reductives of an image produces an hallucination. 
 
 As a general rule, normal sensations of any one sense, and 
 usually those of the different senses, hold together. We have 
 seen many proofs of this in the cases cited. When the atten- 
 tion is attracted by a normal sensation, that is to say, when 
 this sensation regains its ordinary preponderance, the chances 
 are that the other annulled sensations regain their ascendancy 
 at the same time. The patient who is freed at once from his
 
 56 OF IMAGES. [BOOK II. 
 
 illusions by the light of a candle, the unfortunate man who 
 hears voices which cease when conversation becomes interest- 
 ing the lunatic who regains his senses after a sudden dash 
 of cold water, are cured for a longer or shorter time by the 
 more or less durable energy restored to the special reductive. 
 So, in facial paralysis, the face drawn on one side by the action 
 of the left muscle, regains its ordinary form as the muscles on 
 the right gradually regain their power under the action of 
 electricity. 
 
 In other cases the cure follows from the same principles, 
 but is obtained by an inverse process ; I mean those in which 
 the patient is haunted, not by hallucinations, that is to say, by 
 images capable of annulling the normal sensation which ought 
 to counteract them, but by illusions, that is to say, by images 
 excited by the normal sensation, and so strong, precise, and 
 absorbing that no actual sensation from without could have 
 greater power. A state of excitement and expectation in the 
 subject will often cause a sensation, which would be accompa- 
 nied in v a calm state by images of moderate activity, to com- 
 municate an extraordinary clearness and force to the image. 
 ' A whole ship's crew were thrown into consternation by the 
 ghost of the cook, who had died a few days before. He was 
 distinctly seen by them all, walking on the water with a pecu- 
 liar gait by which he was distinguished, one of his legs being 
 shorter than the other. The cook, so plainly recognized, was 
 only a piece of old wreck."* The superstitious sailors who 
 had the figure of their shipmate and his gait fresh in their 
 minds, all, without previous concert, underwent the same 
 illusion at the sight of the uneven motion of the wreck, 
 and their imagination found in the sensation a ground to 
 build on. 
 
 What was here effected by credulity may be caused by dis- 
 ease. We see insane persons who lick the surface of a wall 
 and imagine themselves to taste delicious oranges, or who, 
 when given ripe fruit, find it rotten or poisoned ; who, when 
 they see one person, insist on taking him for another ; who 
 see the furniture of their room move about, grow bigger, or 
 
 * Moore, " The Power of the Soul over the Body," p. 170.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 57 
 
 take fantastic and frightful forms.* In such cases it often 
 happens that by suppressing the normal sensation, which is 
 the starting point of the illusion, we suppress the illusion it- 
 self, and the special reductive is found, not in the predomi- 
 nance, but in the absence of that sensation.f " D. , sev- 
 enty-five years old, of sound mind, came home one day, fright- 
 ened by a thousand phantoms which were following him. 
 Whichever way he looked, objects ivere transformed into spectres, 
 representing sometimes huge spiders which ran at him to 
 drink his blood ; sometimes soldiers with pikes. He was bled 
 in the foot ; the visions continued, accompanied by obstinate 
 attacks of sleeplessness ; a bandage was applied to his eyes ; 
 then they ceased, but returned as soon as the bandage was 
 taken off, until the patient kept it on uninterruptedly for a 
 night and part of a day. From that time he only saw phan- 
 toms at long intervals, and after some days they disappeared 
 entirely. The patient has had no relapse." Here, in place of 
 strengthening the special reductive, the special excitant was 
 suppressed, and the same result arrived at by different means. 
 In a very curious observation made by Dr. Lazarus on 
 himself, we see no less clearly how the exciting sensation, 
 alternately present and absent, alternately excites and sup- 
 presses the illusion. " I was on the Kaltbad terrace at Rigi, on 
 a very clear afternoon, and attempting to make out the Wald- 
 bruder, a rock which stands out from the midst of the gigantic 
 wall of mountains surrounding it, on whose summits we see 
 like a crown the glaciers of Titlis, Uri-Rothsdock, etc. I was 
 looking alternately with the naked eye and with a spy-glass ; 
 but could not distinguish it, with the naked eye. For the 
 space of six to ten minutes I had gazed steadfastly upon the 
 mountains, whose color varied according to their several 
 altitudes or declivities between violet, brown, and dark green, 
 and I had fatigued myself to no purpose, when I ceased look- 
 ing and turned away. At that moment I saw before me (I can- 
 not recollect whether my eyes were shut or open) the figure 
 
 * Brierre de Boismont, op. cit. 777. This was the case with Don Quixote ; the 
 sensation of two great whirlwinds of dust excited in him the image, and conse- 
 quently the sensation of two armies. 
 
 f See Griesinger, op. cit. 103, for different instances.
 
 58 OF IMAGES. [BOOK II. 
 
 of an absent friend, like a corpse. I ought here to mention 
 that I have been for years in the habit of noting down in 
 writing every group of representations which has arisen, 
 whether dreaming or awake, with special force, precision, and 
 clearness, and has affected me vividly enough to induce the 
 thought of the representation as a presentiment. I ought 
 further to mention that I have never had the fortune to see 
 one of such presentiments verified, though they have often 
 been as sudden, clear, and apparently inexplicable, as one 
 could wish*. In addition to this, I have acquired the habit, 
 intelligible enough in a psychologist, of tracing backwards 
 from such incidents, and following up the whole series of 
 antecedent representations. I have very often succeeded in 
 explaining, by the known laws of association of ideas, how 
 such presentiments have contrived to find place in the series 
 of my thoughts at the time. 
 
 On this present occasion, I asked myself at once how I 
 had come to think of my absent friend? In a few seconds I 
 regained the thread of my thoughts, which my looking for 
 the Waldbruder had interrupted, and readily found that the 
 idea of my friend had by a very simple necessity introduced 
 itself among them. My recollecting him was thus naturally 
 accounted for. But in addition to this, he had appeared as a 
 corpse. How was this? At this moment, whether through 
 fatigue or in order to think, I closed my eyes, and found at 
 once the whole field of sight, over a considerable extent, 
 covered with the same corpse-like hue, a greenish-yellow gray. 
 I thought at once that I had here the principle of the desired 
 explanation, and attempted to recall to memory the forms of 
 other persons. And, in fact, these forms too appeared like 
 corpses ; standing or sitting, as I wished, all had a corpse- 
 like tint. The persons whom I wished to see did not all ap- 
 pear to me as sensible phantoms ; and again, when my eyes 
 were open, I did not see phantoms, or at all events only saw 
 them faintly, of no determined color. I then inquired how it 
 was that phantoms of persons were affected by and colored 
 like the visual field surrounding them, how their outlines were 
 traced, and if their faces and clothes were of the same color. 
 But it was then too late, or perhaps the influence of reflection
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 
 
 59 
 
 and examination had been too powerful. All grew suddenly 
 pale, and the subjective phenomenon, which might have last- 
 ed some minutes longer, had disappeared. It is plain that 
 here an inward reminiscence, arising in accordance with the 
 laws of association, had combined with a consecutive sensation 
 of sight. The excessive excitation of the periphery of the 
 optic nerve, I mean the long-continued preceding sensation 
 of my eyes when contemplating the color of the mountain, had 
 indirectly provoked 'a subjective and durable sensation, that 
 of the complementary color ; and my reminiscence incorpo- 
 rating itself with this subjective sensation, became the corpse- 
 like phantom I have described."* This singular case shows 
 us the abnormal effect of sensation. When it exists, it in- 
 creases the force and clearness of an ordinary vague represen- 
 tation till it turns it into a sensible phantom. When it ceases, 
 the force and clearness of the sensible phantom are decreased, 
 till it returns to its ordinary state, that is, one of vague rep- 
 resentation. 
 
 Thus, in every process by which the exaggeration of images 
 is combated, all we attempt is to set up an equilibrium, not 
 that of a balance of which the two scales are on a level, but 
 that of a balance in which one scale is lower than the other. 
 In the normal state of wakefulness, the first scale which holds 
 the sensations proper, is the heavier ; the second and lighter 
 scale holds images proper. The two scales in the normal state 
 are, for the moment, on a level ; but the heavier scale imme- 
 diately weighs down the other, and our images are recognized 
 as internal. Sometimes, in illness, a weight passes from the 
 first to the second ; the second then weighs down the first, 
 and we have an hallucination proper; we are then obliged to 
 add new weights, that is, new sensations, to the first, to de- 
 stroy the preponderance. Sometimes, again, a thread at- 
 taches a weight of the second scale to a weight of the first, 
 the first scale can no longer descend, and we have an illusion 
 proper ; the first means are no longer applicable ; it would be 
 idle to add new weights, we must remove from the first scale 
 the weight with the thread which keeps the scales on a level, 
 
 * " Zur Lehre von den Sinnestauschunijen," Berlin, 1867.
 
 60 OF IMAGES. [BOOK H. 
 
 in spite of the inequality of their loads. In the first case, the 
 normal state is re-established by adding ; in the second, by 
 taking off, weights. 
 
 V. But these are not the only means in question ; for, in 
 addition to the weights constituted by the sensations, there 
 are others, lighter, but still usually sufficient in the healthy 
 state to deprive the image of its externality ; I mean recol- 
 lections. These recollections are themselves images, but con- 
 nected together and undergoing a recoil which gives them a 
 situation in time, by a mechanism we shall inquire into here- 
 after. General judgments acquired by experience are associa- 
 ted with them, and form with them a group of elements con- 
 nected among themselves, and so balanced, by their relations 
 to one another, as to form a whole of considerable cohesion, 
 and lending its entire force to each of its elements. Every 
 one may observe in his own case the reductive power of this 
 group. A few days ago, I had a very clear and perfectly con- 
 nected dream, in which I committed a ridiculous and enormous 
 absurdity, too much so to describe ; let us take something less 
 glaring, such as quietly drawing off one's boots in company, 
 and placing them on the mantel-piece beside the clock. It 
 happened in a drawing-room I like very much ; I saw distinct- 
 ly the principal guests, their dress, their attitudes, I spoke to 
 them, the scene was long, and the impression so clear that a 
 quarter of an hour after I could have described it with every 
 detail. I felt ill at ease, and was wondering how I could get 
 out of my difficulty. Just then I began to awake, and this 
 state lasted two or three minutes. My eyeswere still closed ; 
 but probably, through some feeling of cold or actual move- 
 ment, ordinary consciousness was reviving, though feebly. 
 In the first place, I was astonished at having shown such 
 frightful ill-breeding ; in other words, the vague recollection 
 of my previous actions rose up, and came into opposition with 
 my dream ; this recollection became more precise, and brought 
 on others ; the lines of the past were reformed, and at the 
 same time and in the same degree, the absurdity I had dream- 
 ed of, finding no standing-room, disappeared and evaporated. 
 Then came this judgment, based on general ideas : " It is a 
 dream." The ridiculous image, at once and definitively, be-
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 6 r 
 
 came distinct and severed from the real recollections, and en- 
 tered the region of pure phantasm. I had not yet opened 
 my eyes ; the sensation of present objects had not performed 
 its work ; at all events, it had only done so to the extent of 
 reviving ordinary recollections and general judgments ; these 
 judgments and recollections, by the fixedness of their order 
 and the cohesion of their group, had effected the necessary 
 reduction, and overcome the natural tendency by which the 
 image causes illusion. 
 
 In some cases this repression is much slower. M. Baillar- 
 ger dreamed one night that a certain person had been appoint- 
 ed editor of a newspaper ; in the morning, he believed it to 
 be true, and mentioned it to several persons, who were inter- 
 ested to hear it ; the effect of the dream persisted all the fore- 
 noon, as strongly as that of a real sensation ; at last, about 
 three o'clock, as he was stepping into his carriage, the illusion 
 passed off; he comprehended that he had been dreaming; so 
 here the reductive group did not regain its ascendancy for 
 half a day. In this respect, the detail and intensity of a vol- 
 untary image have sometimes the same power as a dream. 
 We find many examples of this in the lives of Balzac, Gerard 
 de Nerval, Edgar Poe, and other great artists. Balzac once, 
 at the house of Mme. Delphine Gay, was describing with ani- 
 mation a fine white horse he intended to present toSandeau ; 
 some days after he imagined he had actually given it, and in- 
 quired of Sandeau about it ; probably, his friend's astonish- 
 ment and denial disabused him of the notion of his present. 
 
 On other occasions, the reductive group is weakened, and 
 is not sufficient to check even an ordinary image. "An old 
 man," says M. Maury, " who had travelled a great deal, had 
 also read many accounts of travels over ground where he had 
 not been. The recollections of his wanderings and of his 
 readings had ended by becoming completely confused togeth- 
 er; and all seemed to occur at once to his mind as he lay on 
 his sofa, and he would gravely relate things he had read. For 
 example, he would say that he had been in India with Tav- 
 ernier, in the Sandwich Isles with Cook, and had then return- 
 ed to Philadelphia, and had served there under Lafayette. 
 This last statement was true." The notions of chronology
 
 62 OF IMAGES. [BOOK II. 
 
 and order of time were effaced, and no longer performed their 
 ordinary office. 
 
 Persons with lively imaginations are constantly forced to 
 make reductions which this old man had ceased to make ; the 
 general order of their recollections, fortified by the addition 
 of some new observation, is generally sufficient for this. But 
 when an image has acquired extraordinary intensity, and 
 annuls the particular sensation which is its special reductive, 
 though the order of recollections may exist and conclusions 
 be come to, we have, nevertheless, an hallucination ; in fact, 
 we may know that we are under an hallucination, but still the 
 image appears external ; our other sensations and images still 
 form a balance group, but this reductive not being the special 
 one, is insufficient. " Dr. Gregory had gone to the north 
 country by sea, to visit a lady, a near relation, in whom he 
 felt deeply interested, and who was in an advanced state of 
 consumption. In returning from the visit, he had taken a 
 moderate dose of laudanum, with the view of preventing sea- 
 sickness, and was lying on a couch in the cabin, when the 
 figure of the lady appeared before him in so distinct a manner 
 that her actual presence could not have been more vivid. He 
 was quite awake, and fully sensible that it was a phantasm 
 produced by the opiate, along with his intense mental feeling, 
 but he was unable by any effort to banish the vision."* In 
 fact, the sensation which ought to have been produced in him 
 by the gray wall of the cabin was annulled as regarded the 
 whole surface which the phantom seemed to cover ; and it is 
 very clear that reasoning has not the force of a sensation. 
 Many circumstances, organic or moral, the action of haschich,f 
 of datura, of opium, the coming on of apoplexy, different in- 
 flammatory diseases, different cerebral alterations, in short, a 
 number of causes, more or less remote or near, are capable of 
 thus strengthening an image or series of images so as to annul 
 the special sensation which should repress it, and thus bring 
 on hallucination. But if in all these cases the illusion, circum- 
 
 * Abercrombie, " Inquiry concerning the Intellectual Powers," p. 359. 
 f Brierre de Boismont, ibid., 200. Accounts given by several persons who had 
 taken haschich. Ibid., 374.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 63 
 
 scribed by secondary reductives, is at last destroyed by the 
 special one, we meet with a still greater number in which this 
 is not the case. Very frequently, patients, having admitted 
 for a length' of time that their phantoms were only phantoms, 
 have ended by believing them to be real, and equally real 
 with the persons and objects surrounding them, and this too 
 with so absolute a conviction that no experience of their own 
 or evidence of others can cure them of their error. In such 
 cases the second class of reductives are annulled, as well as 
 the special one ; the preponderating image, having paralyzed 
 the contradictory sensation, extends its dominion over the con- 
 tradictory group of other normal images, and excites delirious 
 ideas and unreasonable impulses. The person under hallu- 
 cination becomes a madman ; the loss of local equilibrium has 
 gradually brought on an increasing loss of general equilibrium, 
 as the paralysis of the muscles on the right, after causing a 
 deformation and shrinking of the face towards the left, may 
 affect by sympathy the adjoining functions, and produce gen- 
 eral disease throughout the body. 
 
 Examples of this are numerous ; I have chosen one, re- 
 ported by Dr. Lhomme, which shows in detail the several 
 stages of this spontaneous transformation, and throws great 
 light on the mechanism of the mind. 
 
 In March, 1862, the gendarme S. was on duty at an exe- 
 cution. He was on guard with the prisoner during part of 
 the night, assisted at the toilette, and was a few feet from the scaf- 
 fold when the execution took place. When the head fell, he saw 
 
 the executioner take it up to put it in the basket He says 
 
 that this made a deep impression on him ; he had been seized 
 with a nervous trembling which he could not control, at the mo- 
 ment he saw the prisoner brought up with his outer clothes re- 
 moved and neck bare ; and long after the execution, the fig- 
 ure of the bleeding head which he had seen thrown into the bas- 
 ket was constantly before him. 
 
 Some time after, talking with the quartermaster, he said 
 that he had no great opinion of Protestants. " He told me I 
 was wrong ; that there were many very good people among 
 them, and even some persons of high rank, and mentioned, as 
 an instance, the Minister of War. I kept thinking of this con-
 
 64 F IMAGES. [BOOK II. 
 
 versation, and it came into my head that the quartermaster 
 would probably report me to the Minister of War. Some days 
 afterwards I dreamed that I was actually condemned to dcatJi 
 by the Minister's order, without having had a trial. I thought 
 in my dream that I was bound with straps and was being rolled 
 like a barrel towards the guillotine. This dream impressed me 
 vividly. I told it to a comrade, who laughed at me, but it often 
 recurred to my mind ! " 
 
 On the 1st of August, going from Sancerre to Sancergues, 
 he got drunk, arrived too late, and found the barracks closed. 
 Next day the quartermaster told him that he should report 
 him to the lieutenant for being late. The 2d of August he 
 was " out of spirits, but not ill." The 3d of August, he says, 
 " I did not feel all right, though I had slept well ; / kept think- 
 ing of my dream When I went on duty as sentry, I 
 
 thought every one was staring at me, and that I heard my com- 
 rades and other persons whispering that I was going to be 
 guillotined'' 
 
 That evening he went to bed at eleven, having cleaned 
 his accoutrements for next day's drill. " I had perhaps been 
 in bed twenty minutes, and had not fallen asleep, when I 
 heard a noise in the clock over the mantel-piece, and then a 
 voice came from it, and said to me, " You must die, you must 
 die. Your head will be cut off in two days. We must have your 
 head, we must have your head ! " He started up and looked in 
 the clock, but there was nothing to be seen, so thinking it a 
 joke of his comrades, he went to bed again. The voice began 
 again, and he was looking about during part of the night. 
 About four in the morning he rose, without having slept, and 
 went to drill, but said nothing of the voice he had heard, as 
 he " still thought that his comrades had been playing him a 
 trick." Coming back he was tired, but could not eat, and 
 cleaned his accoutrements ; he felt no inclination to sleep, and 
 did not go to bed till one in the morning. He was scarcely 
 in bed when he heard the same voice and same words proceed- 
 ing from the clock. " Then I rose and walked up and down, 
 very certain that they would execute me next morning, and 
 that that was why the lieutenant had remained at Sancergues." 
 
 He rose early. " The quartermaster was surprised to see
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 65 
 
 me ready so soon, and said something in a low tone to my com- 
 rades. / thought I heard, ' See that your carbines are loaded ; 
 watch him that he does not escape ! ' ' 
 
 On this he found his horse, and set off at a gallop without 
 knowing where he was going. At last he came to a wood, 
 got off, and hid himself in a thicket, and loaded his carbine to 
 defend himself; then he determined to kill himself, and took 
 off his boots that he might draw the trigger with his foot, but 
 first knelt to say a prayer. " I was soon interrupted by a fig- 
 ure with a huge beard, who disappeared as soon as I took aim 
 at him ; and three times running I was stopped by the same 
 apparition or by figures of Punch, which disappeared as I was 
 going to fire. I saw also girls with hooped petticoats, dancing 
 in the trees above my head." 
 
 The other gendarmes came up ; he threatened to fire on 
 them, attempted to take off his white breeches to hide himself 
 better; then, hearing them return, he fired on the foremost 
 of them, and attempted to escape, but was taken. " I was 
 quite convinced that they were going to take me to execu- 
 tion, and called out ' Murder !' I even thought more than once 
 that I saw a gendarme draw his knife from his pocket to stab 
 me, and my cries increased." He was bound, and a guard put 
 over him and did not sleep all night. *' I continually heard 
 female voices saying, 'Poor fellow ! how unfortunate ! He 
 must be guillotined in two Jwurs* and his head sent to Paris by 
 six o clock. The quartermaster has the basket for it! The 
 whole day and night of the 6th I had the same ideas, and 
 could not sleep for a moment or take any kind of nourishment. 
 It was not till the /th that I was able, during the daytime, to 
 throw myself on my bed and sleep for a short time. When I 
 woke I found my head completely clear, though I recollected 
 perfectly all that had taken place. I expressed my sorrow to 
 my comrades for what had passed, and asked at once after the 
 one I had wounded." From that time the hallucinations 
 ceased : the patient's reason is unaffected ; he was calm and 
 quiet during his stay in an asylum, and is replaced in the 
 brigade of Gendarmerie, and has regularly performed his duty 
 since. 
 
 Few examples are most instructive than this ; we follow
 
 66 OF IMAGES. [BOOK II. 
 
 the hallucination from its first rise to its completed state and 
 its cure. The mental abscess begins with a terrible image, 
 combined with extreme emotion. The image constantly re- 
 viving besets the mind. It attaches itself to the idea of self, 
 and S imagines a case in which he may well be in person- 
 al danger. This connexion becomes defined, and in a dream 
 he sees himself led to the guillotine. The dream returns to 
 his mind during the day. After he has committed a fault it 
 recurs with greater force. The mental words by which he ex- 
 presses it to himself become a whispering of his comrades, and 
 then a voice in the clock. The voice returns, and his convic- 
 tion grows firmer. Unconnected hallucinations of sight, then 
 of the touch, follow. For thirty hours the voices continue, 
 and the hallucination of the ear is at its height. Then he be- 
 comes suddenly freed from them, as if the mental abscess 
 having ripened, had broken of itself.* 
 
 VI. From these examples we can form a notion of our in- 
 tellectual machinery. We must lay aside the words reason, 
 intelligence, will, personal power, and even self, as we lay aside 
 the words vital force, medicative virtue, vegetative soul ; they 
 are literary metaphors, capable at the most of convenient use 
 by way of summary or abbreviation, to express general states 
 and combined effects. All that observation detects physi- 
 ologically in the living being are cells of different kinds, ca- 
 pable of spontaneous development, and modified in the direc- 
 tion of this development by the concurrence or antagonism of 
 their neighbors. All that observation detects psychologically 
 in the thinking being are, in addition to sensations, images of 
 different kinds, primitive or consecutive, endued with certain 
 tendencies, and modified in their development by the concur- 
 rence or antagonism of other simultaneous or contiguous im- 
 ages. Just as the living body is a polypus of mutually de- 
 pendent cells, so the Active mind is a polypus of mutually de- 
 pendent sensations and images, and in the one case as in the 
 other, unity is nothing more than a harmony and an effect. 
 Every image is possessed of an automatic force, and tends 
 spontaneously to a particular state ; to hallucination, false 
 
 * " Annales Medico-Psychologiques," 46 Serie, ii. 238.
 
 CHAP, I.] NATURE AND REDUCTION OF IMAGES. 67 
 
 recollection, and the other illusions of madness. But it is ar- 
 rested in its progress by the contradiction of a sensation, of 
 another image, or group of images. The mutual arrest, the 
 reciprocal clash, the repression, produce by their combined 
 effect an equilibrium ; and the effect we have just seen pro- 
 duced by the special corrective sensation, by the connexion 
 of our recollections, by the order of our general judgments, 
 is but an instance of the constant re-arrangement and inces- 
 sant limitation which innumerable incompatibilities and con- 
 flicts are incessantly bringing about among our images and 
 ideas. This equilibrium is the state of reasonable wakeful- 
 ness. As soon as it is at an end by the hypertrophy or atro- 
 phy of an element, we are mad, wholly or partially. When 
 it lasts over a certain time, the fatigue is too great, and we 
 sleep ; our images are no longer reduced and guided by antag- 
 onistic sensations coming from the outer world, by the re- 
 pressive effect of combined recollections, by the dominion 
 of well-connected judgments ; so they then acquire their 
 full development, turn into hallucinations, arrange themselves 
 spontaneously according to new tendencies, and sleep, though 
 crowded with intense dreams, is a rest, since, suppressing a 
 constraint, it brings on a state of relaxation. 
 
 But in the mean while the reader has been able to ascertain 
 the nature of the image. For this we must remain at the 
 point at which we have provisionally placed ourselves. We 
 do not yet enter upon physiology, but confine ourselves to 
 pure psychology. We do not talk of nerves, spinal marrow, 
 or brain. We leave aside the unknown excitation which the 
 external extremity of the nerve undergoes by contact with an 
 external object, and which transmits itself to the spinal mar- 
 row, passes thence to the surface of the brain, spreads among 
 its circumvolutions, becomes persistent in the nervous centres, 
 and is, later on, renewed there. We do not examine the link 
 connecting the sensation with the image. We observe man, 
 not with the scalpel and microscope, but with that internal 
 view we call consciousness, and we compare directly the image 
 and the sensation. In this limited field, and in this precise 
 sense, we have just seen that the image, with different physi- 
 cal stimulants, and a special reductive, is of the same nature
 
 68 OF IMAGES. [BOOK II. 
 
 as the sensation. It is the sensation itself, but consecutive or 
 reviving; and from whatever point we consider it, we find it 
 coincide with the sensation. It furnishes the same combina- 
 tions of derived and superior ideas ; the chess-player who plays 
 blindfolded, the painter who copies an absent model, the mu- 
 sician who hears a score when he looks over the sheet of music, 
 form the same judgments, go through the same reasonings, 
 and experience the same emotions, as if the chess-board, the 
 model, the symphony, were actually experienced by their 
 senses. It provokes the same instinctive movements and the 
 same associated sensations : the man who has a disgusting medi- 
 cine put before him, who is about to undergo a surgical opera- 
 tion, who recalls a melancholy or terrible accident, shudders, 
 sweats, or is sick, in presence of the image alone, as he would if 
 the sensation were itself present. Though generally fragmen- 
 tary, fugitive, and weak, it arrives in many cases, in the ex- 
 treme concentration of excessive attention, in violent and 
 sudden emotions, at a state bordering closely on the corre- 
 sponding sensation, and attains the fulness of detail, the clear- 
 ness, energy, and persistence of the sensation. Finally, taken 
 alone and freed from the reduction of its special corrective, 
 it acquires apparent externality, the want of which, even at 
 its maximum of intensity, usually distinguishes it from the 
 sensation ; it acquires this for an imperceptible moment in 
 the majority of cases ; for some seconds or minutes in certain 
 well-authenticated instances ; for several hours, days, or weeks 
 in the states of half sleep, complete sleep, ecstasy, hypnotism, 
 somnambulism, hallucination ; in the disorders produced by 
 opium or haschich, in various cerebral or mental maladies ; and 
 acquires it with or without lesion, or with either partial or total 
 lesion, of the normal equilibrium which subsists between other 
 ideas and images. We may define it, then, as a repetition or 
 revival of the sensation, while at the same time we distinguish 
 it from the sensation ; first, by its origin, since it has the sen- 
 sation as its antecedent, while the sensation is preceded by 
 an excitation of the nerve ; and again, by its association with 
 an antagonist, since it has several reductives, among others, 
 the special corrective sensation, while the sensation itself 
 has no reductive.
 
 CHAP. I.] NATURE AND REDUCTION OF IMAGES. 69 
 
 Arrived at this we understand its nature : in reviving the 
 sensation, it replaces it ; it is its substitute ; that is to say, a 
 thing differing from it in certain respects, like it in others, 
 but so that both differences and resemblances have their ad- 
 vantages. What these advantages are we shall see later on. 
 Images of a certain kind constitute recollections ; that is to 
 say, knowledge of past events. Images associated with the 
 sensations of the different senses, especially with those of sight 
 *md touch, constitute acquired perceptions ; that is to say, all 
 such parts of our knowledge of external individual objects as 
 extend beyond actual crude sensation. Images of a certain 
 kind, and associated in a certain way, constitute previsions ; that 
 is to say, knowledge of future events. Just as the knowledge 
 of general qualities is only possible by the substitution of 
 signs for perceptions and images, so knowledge, whether of 
 events past or to come, or of the grouped properties which 
 make up every individual external object, is only possible by 
 the substitution of images for sensations. Nature employs, in 
 the two cases, the same process to arrive at the same effect ; 
 psychology here repeats physiology. As we see iir the his- 
 tory of respiration or of locomotion a physiological element 
 become, by a slight modification, the instrument of a more 
 complicated function, then, by a second additional modifica- 
 tion, execute a still superior function ; so in the history of in- 
 telligence, we see a psychological element give rise, by a small 
 modification, to very extended operations, then, by a second, 
 added modification, accomplish operations so complex, so deli- 
 cate, and so numerous, that they seem destined to remain 
 forever beyond our grasp.
 
 OF IMAGES. [BOOK II. 
 
 CHAPTER II. 
 
 LAWS OF THE REVIVAL AND OBLITERATION OF IMAGES. * 
 
 I. WHEN we see or touch an object, when we hear a 
 sound, when we experience a sensation of taste, of smell, of 
 cold, of pain, in short, any sensation whatever, we usually re- 
 tain the image during a second or two, unless some other sen- 
 sation, image or idea, comes in the way, and suppresses in- 
 stantly this prolongation and echo. But in many cases, and 
 above all when the sensation has been a prominent and im- 
 portant one, the image revives of itself after a longer or shorter 
 period of suppression. This spontaneous revival is its fun- 
 damental property, and may be effected after long periods 
 have elapsed. Many of us have recolleetions which go back 
 twenty, thirty, forty years, or more. I know a person, born in 
 a little provincial town, who can relate with the utmost exac- 
 titude all the circumstances of a visit of the Empress Marie- 
 Louise in 1812, can describe her dress, the dresses of the la- 
 dies and young girls appointed to receive her, can hear men- 
 tally the sound of her voice, see her gestures, her face, the at- 
 titudes of the persons appointed to present her with an address, 
 and many other things. What renders these revivals still 
 more remarkable is that they frequently occur without the 
 image having reappeared during the whole interval. On re- 
 turning, after many years' absence, to one's father's house, or 
 to one's native village, numbers of forgotten objects and facts 
 unexpectedly reappear. The mind, suddenly thronged by 
 their stirring crowd, resembles a box of dried rotifera, which 
 have lain inert some ten years, but when sprinkled with water, 
 at once revive and twist about. We mount the dark staircase, 
 we know where to find the handle of the door, we imagine 
 ourselves seated at table in cur accustomed place, we see the
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. j l 
 
 water-bottle on the right, and the salt-cellar on the left, we 
 seem to taste the flavor of some Sunday dish. We look up at 
 the wall and are surprised not to find there some old engrav- 
 ing we had stared at as children. We see the gesture and 
 stoop of some former guest, the square body and long folds of 
 a blue dress ; we almost hear the tones of voices which have 
 long been still. We come to the well, and recall the vague 
 terror with which as children, mounting on tiptoe, we looked 
 on the obscure depth and the trembling reflection of the cold 
 water at what seemed to us an infinite distance below. 
 
 Some people unconsciously preserve certain reviving'shreds 
 of long-distant impressions. " There often recurred to my 
 mind," says M. Maury, " without my knowing why, three 
 proper names, each accompanied by the name of .a town in 
 France. One day I came across an old newspaper and com- 
 menced to read it for want of any thing better to do. Among 
 the advertisements I saw one of a depot of mineral waters, 
 with the names of the druggists who sold them in the princi- 
 pal towns of France. There I found my three unknown names 
 with those of the three towns with which they were con- 
 nected in my mind. All was explained ; my memory, which 
 is excellent for words, had preserved a recollection of these 
 associated names, on which my eyes must have rested while 
 I was looking ( as had happened about two months previously) 
 for the address of a depot of mineral waters. But the circum- 
 stance had gone out of my mind without the recollection 
 being wholly effaced. Now, certainly, I could not have paid 
 much attention in so rapid a glance." 
 
 Illness sometimes causes a revival of such images as this of 
 names, which seemed, not merely torpid, but hopelessly ex- 
 tinct. " A girl was seized with a dangerous fever, and, in the 
 delirious paroxysm accompaying it, was observed to speak 
 in a strange language which, for some time, no one could un- 
 derstand. At last it was ascertained to be Welsh a tongue 
 of which she was wholly ignorant at the time she was taken 
 ill, and of which she could not: speak a single syllable after her 
 recovery. For some time the circumstance was, unaccount- 
 able, till, on inquiry, it was found that she was a native of 
 Wales, and had been familiar with the language of that coun-
 
 72 OF IMAGES. [BOOK II. 
 
 try in her childhood, but had wholly forgotten it afterwards."* 
 Again ; some fugitive impressions, not observed at the 
 time, may rise anew with strange power and automatic exact- 
 ness. Many medical writers have noticed the storyf of a 
 young woman of five-and-twenty who could neither read nor 
 write, who, during an illness, repeated long passages of Latin, 
 Greek, and Rabbinical Hebrew, but on recovery, spoke noth- 
 ing but her own language. During her delirium, several of 
 these fragments were taken down in writing from her own 
 mouth. After inquiry, it was found that she had lived, when 
 nine years old, with her uncle, a clergyman of considerable 
 learning, who was in the habit of walking of an afternoon in a 
 passage adjoining the kitchen, and there reciting favorite 
 passages of Rabbinical Hebrew and Greek. On referring to 
 his books, there were found, word for word, many of the pas- 
 sages repeated by the sick girl. The noise and articulation of 
 his voice had remained fixed in her ears. She had heard 
 them as she repeated them without understanding them.^: 
 Haschich, the death-agony, great and sudden emotion, some- 
 times cause revivals, equally minute, of sensations as little 
 observed and still farther distant. We can assign, then, no 
 limits to these revivals, and are compelled to ascribe to every 
 
 * Macnish, " Philosophy of Sleep," p. 55, n. ; and see two analogous facts cited 
 by Azam, " Annales Medico-Psychologiques," 3 e Serie.vi. 443. 
 
 \ Coleridge, " Biographia Literaria," vol. i. p. 117. 
 
 \ "A man of ordinary ability, servant of a Spanish ambassador, had frequently 
 to be present during important conferences, but did not appear to have recollect- 
 ed any thing of what had passed. He was seized with brain fever, and in his de- 
 lirium repeated with considerable order many discussions he had heard on the polit- 
 ical interests of different powers, so much so that the ambassador, who had con- 
 sidered him only as a faithful servant, came to hear him, and thought of promoting 
 him to be his secretary ; but the affection of the brain passed off, and when the 
 patient recovered, this memory had departed." (Grimaud de Caux, cited by Duval 
 Jouve, "Traite de Logique," 159.) 
 
 " I was once told by a near relative of mine, that having in her childhood 
 fallen into a river, and being on the very verge of death, .... she saw in a moment 
 her whole life, arrayed before her as in a mirror, not successively, but simulta- 
 neously ; and she had a faculty developed as suddenly for comprehending the 
 whole and every part." De Quincey, " Confessions, etc." p. 258. De Quincey 
 and other opium-eaters have observed in themselves this faculty of living mentally, 
 during a dream of a few minutes, a life of many years, and even of many centuries.
 
 CHAI-. II.] REVIVAL AND OBLITERATION OF IMAGES. 73 
 
 sensation, however rapid, unimportant or obliterated it may 
 have been, an indefinite power of revival, without mutilation 
 or loss, even after an enormous distance of time ; just as a 
 vibration of ether, which, starting from the sun, transmits itself 
 through millions of leagues till it reaches our optical apparatus, 
 with its special spectrum and its proper rays, the same at its 
 starting-point and at its place of arrival, intact, and capable, 
 by its exact conservation, of manifestating on the instrument 
 receiving it the nature of the fire from which it is emitted. 
 
 II. If, however, we compare different sensations, images, 
 or ideas, we find that their aptitudes for revival are not equal. 
 A large number of them are obliterated, and never reappear 
 through life ; for instance, I drove through Paris a day or two 
 ago, and though I saw plainly some sixty or eighty new faces, 
 I cannot now recall any one of them ; some extraordinary cir- 
 cumstance, a fit of delirium, or the excitement of haschich 
 would be necessary to give them a chance of revival. On the 
 other hand, there are sensations with a force of revival which, 
 nothing destroys or decreases. Though, as a rule, time weak- 
 ens and impairs our strongest sensations, these reappear entire 
 and intense, without having lost a particle of their detail, or 
 any degree of their force. M. Brierre de Boismont,* having 
 suffered when a child from a disease of the scalp, asserts that 
 " after fifty-five years have elapsed he can still feel his hair 
 pulled out under the treatment of the skull-cap!' For my 
 own part, after thirty years, I remember feature for feature 
 the appearance of the theatre to which I was taken for the 
 first time. From the third row of boxes, the body of the 
 theatre appeared to me an immense well, red and flaming, 
 swarming with heads ; below, on the right, on a narrow floor, 
 two men and a woman entered, went out, and re-entered, 
 made gestures, and seemed to me like lively dwarfs : to my 
 great surprise, one of these dwarfs fell on his knees, kissed 
 the lady's hand, then hid behind a screen ; the other, who was 
 coming in, seemed angry, and raised his arm. I was then 
 seven, I could understand nothing of what was going on ; but 
 the well of crimson velvet was so crowded, gilded, and bright, 
 
 * Brierre de Boismont, op. cit. 376.
 
 74 OF IMAGES. [BOOK II. 
 
 that after a quarter of an hour I was, as it were, intoxicated, 
 and fell asleep. 
 
 Every one of us may find similar recollections in his mem- 
 ory, and may distinguish in them a common character. The 
 primitive impression has been accompanied by an extraor- 
 dinary degree of attention, either as being horrible or delight- 
 ful, or as being new, surprising, and out of proportion to the 
 ordinary run of our life ; this it is we express by saying that 
 we have been strongly impressed ; that we were absorbed, 
 that we could not think of any thing else ; that our other sen- 
 sations were effaced ; that we were pursued all the next day 
 by the resulting image ; that it beset us, that we could not 
 drive it away ; that all distractions were feeble beside it. It 
 is by force of this disproportion that impressions of childhood 
 are so persistent ; the mind being quite fresh, ordinary objects 
 and events are surprising. At present, after seeing so many 
 large halls and full theatres, it is impossible for me, when I 
 enter one, to feel swallowed up, engulfed, and as it were, lost 
 in a huge dazzling well. The medical man of sixty, who has 
 experienced much suffering, both personally and in imagina- 
 tion, would be less upset now by a surgical operation than when 
 he was a child. 
 
 Whatever may be the kind of attention, voluntary or in- 
 voluntary, it always acts alike ; the image of an object or event 
 is capable of revival, and of complete revival, in proportion to 
 the degree of attention with which we have considered the 
 object or event. We put this rule in practice at every mo- 
 ment in ordinary life. If we are applying ourselves to a book, 
 or are in lively conversation, while an air is being sung in the 
 adjoining room, we do not retain it ; we know vaguely that 
 there is singing going on, and that is all. We then stop our 
 reading or conversation, we lay aside all internal pre-occupa- 
 tions and external sensations which our mind or the outer 
 world can throw in our way ; we close our eyes, we cause a 
 silence within and about us, and, if the air is repeated, we 
 listen. We say then that we have listened with all our ears, 
 that we have applied our whole minds. If the air is a fine 
 one, and has touched us deeply, we add that we have been 
 transported, uplifted, ravished, that we have forgotten the
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. 75 
 
 world and ourselves ; that for some minutes our soul was dead 
 to all but sounds. And, in fact, there are numerous examples 
 in which, under the empire of a ruling idea, all other sensations, 
 however violent, are annihilated ; such, for instance, is the 
 story of Pascal, who one night solved the problem of the cy- 
 cloid, to distract his mind from violent pain in the teeth ; 
 that again of Archimedes, who, in tracing geometrical diagrams, 
 was unconscious of the storrning of Syracuse. Such also are 
 the frequent and well-proved instances of soldiers, who, in the 
 excitement of action, do not notice their wounds, and those 
 of ecstatics, of somnambulists, and of hypnotized persons. 
 These authentic instances, and these metaphors of language, 
 all bring to light the same fact, that is to say, the more or 
 less complete and universal cancelling of all sensations, images, 
 or ideas in favor of a single one ; this last one being persist- 
 ent and absorbing, produced and prolonged with an energy 
 usually dispersed over several. In other words, we are set up 
 for a time in a fixed and determinate form ; the contrary solici- 
 tations, the different tendencies which result in another state, 
 the other images, ideas, and sensations which are striving for 
 production, remain in an incipient and abortive state. The 
 given form is incompatible with them, and checks their devel- 
 opment. What happens in us is just what takes place in a 
 solution when a crystal is formed ; the particles which had no 
 affinity for any special structure now place themselves in a 
 mass in fixed order ; their unstable equilibrium is followed 
 by a stable equilibrium whose rigid and precise direction resists 
 the different agitations of the air and the fluid. 
 
 This exclusive momentary ascendancy of one of our states 
 of mind explains the greater durability of its aptitude for re- 
 vival and for more complete revival. As the sensation revives 
 in the image, the image reappears with a force proportioned 
 to that of the sensation. What we meet with in the first 
 state is also to be met with in the second, since the second is 
 but a revival of the first. So, in the struggle for life,* in 
 
 * " Struggle for life" (Darwin). We shall see later on the development of this 
 doctrine. The theory of the great English naturalist is nowhere more precisely 
 applicable than in psychology.
 
 76 OF IMAGES, [BOOK II. 
 
 which all our images are constantly engaged, the one furnish- 
 ed at the outset with most force, retains in each conflict, by 
 the very law of repetition which gives it being, the capacity 
 of treading down its adversaries ; this is why it revives, inces- 
 santly at first, then frequently, until at last the laws of pro- 
 gressive decay, and the continual accession of new impressions, 
 take away its preponderance, and its competitors, finding a 
 clear field, are able to develope in their turn. 
 
 A second cause of prolonged revivals is repetition itself. 
 Every one knows that to learn a thing we must not only con- 
 sider it attentively, but consider it repeatedly. We say as to 
 this in ordinary language, that an impression many times re- 
 newed is imprinted more deeply and exactly on the memory. 
 This is how we contrive to retain a language, airs of music, 
 passages of verse or prose, the technical terms and propositions 
 of a science, and still more so the ordinary facts by which our 
 conduct is regulated. When, from the form and color of a 
 currant jelly, we think of its taste, or when tasting it with our 
 eyes shut, we imagine its red tint and the brilliancy of a 
 quivering slice, the images in our mind are brightened by rep- 
 etition. Whenever we eat, or drink, or walk, or avail our- 
 selves of any of our senses, or commence or continue any 
 action whatever, the same thing happens. Every man and 
 every animal thus possesses at every moment of life a certain 
 stock of clear and easily reviving images, which had their 
 source in the past in a confluence of numerous experiences, 
 and are now fed by a flow of renewed experiences. When I 
 want to go from the Tuileries to the Pantheon, or from my 
 study to the dining-room, I foresee at every turn the color- 
 ed forms which will present themselves to my sight ; it is 
 otherwise in the case of a house where I have spent two hours, 
 or of a town where I have stayed three days ; after ten years 
 have elapsed the images will be vague, full of blanks, some- 
 times they will not exist, and I shall have to seek my way or 
 shall lose myself. This new property of images is also de- 
 rived from the first. As every sensation tends to revive in its 
 image, the sensation twice repeated will leave after it a double 
 tendency, that is, provided the attention be as great the second 
 time as the first ; usually this is not the case, for the novelty
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. 
 
 77 
 
 diminishing, the interest diminishes ; but if other circumstan- 
 ces renew the interest, or if the will renovates the attention, 
 the incessantly increasing tendency will incessantly increase 
 the chances of the resurrection and integrity of the image. 
 
 III. These are but the general conditions of revival ; we 
 obtain them by comparing an image taken at any point of its 
 existence with another image at any point of its existence. 
 We have npw to compare two adjoining moments in the same 
 mind, and to determine the more special conditions which ex- 
 cite at any time the birth of one image rather than of anoth- 
 er. For this, let us consider, not only isolated sensations, but 
 also series of sensations. These have a similar tendency to*" 
 revival, and the law which is applicable to tile elements is also 
 applicable to the compounds. On some days, without wishing 
 it, we pass over in our mind some portion oour life, such as 
 a day's travel, some evening at the opera, some interesting 
 conversation. We feel ourselves brought back in a fixed 
 manner to a former state ; the ideas which attempt to throw 
 themselves in the way are unwelcome ; they are driven out, 
 or rest on the threshold ; if, at the first moment, some gap was 
 found in our recollection, it usually ends by supplying itself; 
 a forgotten detail rises unexpectedly. I recollect at this mo- 
 ment an evening spent at Laveno on the Lago Maggiore, and 
 as I dwell on it, I see my dinner at the inn, the coarse white 
 cloth, the pretty startled servant ; then, a moment after, the 
 path winding among thyme and lavender, the grayish-blue 
 lake under its moist cloud of vapor, the patches of light, the 
 glittering tracks, the sprinkled silver scales which a stray sun- 
 beam had embroidered in places on its level sheet, the im- 
 perceptible rustling made by the little waves on the shore, 
 and the bells of the cows tinkling here and there in the silence. 
 All the prominent points in the group of sensations I then had, 
 reappear in turn or together. If now, taking one of these 
 points, I inquire how it emerged, I find that it was when it had 
 already commenced to emerge. For instance, when I have re- 
 called the winding lines of the path, and imagine myself turn- 
 ing to the left, I recall the slate-colored lake and its embroid- 
 ery of shining spangles, and above, the peaked mountains de- 
 scending in green slopes to the water ; I find that the extreme
 
 78 OF IMAGES. [BOOK II 
 
 edge of the bank borders the lake, the uniform surface is 
 striped with brilliant fringes, and on the other side, the water 
 rejoins the meadows and rising slopes ; thus, the extremity 
 of one image coincides with the commencement of the next, 
 and so the latter begins to revive as the first disappears. In 
 the same way, the murmur of the tiny waves and the tinkling 
 of the bells revert to me when my visual images are those of 
 the lake and the bank ; a commencement of imaginary sound 
 accompanied the imaginary colored forms ; it disengages it- 
 self, and we feel it reproduced with all its shades, and up to 
 its end. The partial revival results in a total revival. This 
 is so true that if, upsetting the natural tendency of the images 
 to revert in the order of the sensations, I attempt to repro- 
 duce the series inversely, I am able to call up the former sen- 
 sations from the latter ones as soon as I can hit on the point 
 of contact in which they touch the ones they have followed. 
 In fact, if I now trace backwards up to my arrival at the inn, 
 I see again the old oak some twenty paces from the house, 
 two or three trunks of felled trees, and a dozen vagabonds 
 strolling about or sleeping in the warmth of the evening sun ; 
 thus by calling up the point of contact, that is to say, the com- 
 mencement of the image, I supply to the image the means of 
 reviving as a whole. In fact, to speak correctly, there is no 
 isolated and separate sensation. A sensation is a state which 
 begins as a continuation of preceding ones, and ends by los- 
 ing itself in those following it ; it is by an arbitrary severing, 
 and for the convenience of language, that we set it apart as 
 we do ; its beginning is the end of another, and its ending the 
 beginning of another. By force of the general law which con- 
 nects it to the image, its image has the same properties as 
 itself; therefore this image itself arouses at its earlier extrem- 
 ity the ending of another image, and at its later extremity 
 the commencement of another image, in such a way that 
 the precedents and consequents of the sensation have also 
 indirectly their echo in the image of the sensation. 
 
 Further than this, as different sensations are often similar 
 in part, as soon as the image of one among them appears, the 
 images of the others partially appear. When just now I was 
 describing the sparkling streaks which the sun made on the
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. 
 
 79 
 
 water, I compared them to embroidery, 'to fringes, and to 
 spangles of silver ; the portion common to these four sensa- 
 tions, present in the first, successively revived the three others. 
 Here again, the partial revival has resulted in a total revival. 
 We have often a difficulty in observing this partial revival. It 
 seems to us, at the first glance, that such an idea has arisen 
 involuntarily and by chance ; we cannot see how it is connect- 
 ed with the foregoing one. This results from the idea which 
 seems to have immediately preceded it, not having really done 
 so ; there were intermediate stages between them, which 
 habit, inattention, or the speed of the operation, have prevent- 
 ed our observing ; these intermediate stages have served for 
 an invisible transition, and it has been through them that the 
 law of Contiguity, or the law of Similarity, has applied. 
 Hobbes, one of the first originators of this theory, relates* 
 how, in the midst of a conversation on the English civil war, 
 some one suddenly asked what was the value, under Tiberius, 
 of the Roman penny; an abrupt question seemingly uncon- 
 nected with what had gone before. There was, however, a 
 connexion, and with a little thought he recovered it. The 
 English civil war, under Charles the First, Charles the First 
 delivered up by the Scotch for 2OO,ooo/. sterling, Jesus 
 Christ similarly betrayed for thirty pence under Tiberius. 
 These were the links of the chain which led the speaker to his 
 remarkable inquiry.f We see now how the celebrated laws 
 governing the association of images, and consequently that 
 of ideas,:}: are reduced to a more simple law. What excites 
 
 * "Leviathan," part i. ch. 3, vol. iii. p. 12 (Ed. Molesworth). 
 
 f " An instance of this occurs to me with which I was recently struck. Think- 
 ing of Ben Lomond, this thought was immediately followed by the thought of the 
 Prussian system of education. Now, conceivable connexion between these two 
 ideas in themselves, there was none. A little reflection, however, explained the 
 anomaly. On my last visit to the mountain, I had met upon its summit a German 
 gentleman, and though I had no consciousness of the intermediate and unwakened 
 links between Ben Lomond and the Prussian schools, they were undoubtedly 
 these, the German, Germany, Prussia, and, these media being admitted, the 
 connexion between the extremes was manifest. Sir W. Hamilton, " Lectures,'* 
 etc., i. p. 353. 
 
 \ See Bain, " Senses and Intellect." He derives all the operations of the intel- 
 lect from these two laws. See also Mervoyer, "Etude sur 1' Association des Idees' 
 (1864).
 
 80 OF IMAGES. [BOOK II. 
 
 at any moment a particular image rather than any other, is a 
 commencement of the revival ; and this revival has already 
 commenced, either by similitude, from the anterior image or 
 sensation containing a portion of the reviving image ; or by 
 contiguity, from the anterior image becoming confused at its 
 end with the commencement of the reviving image. Given 
 any image at any particular moment, we can always explain 
 its actual presence by its commencement of revival in the 
 preceding image or sensation ; and its clearness, force, apti- 
 tude for revival and other intrinsic qualities, by the amount 
 of attention it has received, and number of revivals it has 
 undergone, either in itself or in the corresponding sensation. 
 All, it will be observed, comprised in our fundamental law, 
 which discovers the tendency to revival in the sensation and 
 in its image, and which, therefore, assures to the commenced 
 image, to the image accompanied by attention, and to the 
 image strengthened by repetitions, a preponderance which 
 results in its revival. 
 
 IV. The same laws explain the opposite event ; by sup- 
 pressing or weakening the conditions which increase an image's 
 chance of revival and preponderance, we suppress its chances 
 of ascendancy and revival. In the first place, all that lessens 
 the attention lessens these chances. Every minute we expe- 
 rience twenty sensations, of heat, cold, pressure, contact, mus- 
 cular contraction ; slight sensations like these are being in- 
 cessantly produced in all parts of our bodies ; in addition to 
 this, sounds, murmurings, and hummings, are constantly go- 
 ing on in our ears ; a number of little sensations of smell and 
 taste arise in pur noses and throats ; but we are otherwise en- 
 gaged we are thinking, meditating, talking, reading and 
 during all this time we neglect other things. As regards other 
 sensations, we are as if asleep or in a dream ; the ascendancy 
 of some dominant image or sensation keeps them in a nascent 
 state. If, at the end of a minute, we attempt to recall them 
 by memory, they do not revive ; they are like seeds sown by 
 the handful, but which have not grown ; some single one, 
 more lucky, has monopolized to itself all the room and nutri- 
 ment the earth affords. It does not necessarily follow that 
 these sensations, destined to obliteration, are feeble ones :
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. gl 
 
 they may be powerful ones : it is sufficient that they should 
 be weaker than the privileged one. A musket-shot, the flash 
 of a cannon, a painful wound, frequently escape attention in 
 the heat of battle, and, not having been observed, cannot re- 
 vive ; a soldier suddenly finds he is bleeding, without being 
 able to recollect the blow he has received. In nine cases out 
 of ten, and perhaps in ninety-nine out of a hundred, the sensa- 
 tion loses in this manner its power of revival, because there 
 cannot be attention without distraction, and the predominance 
 acquired v by one impression is a predominance taken from the 
 others. Here again, things are, as it were, in a balance ; one 
 scale can only rise by lowering the other, and the lowering or 
 elevation of the one is in proportion to the elevation or lower- 
 ing of the other. 
 
 On the other hand, the want of repetition also diminish- 
 es the chances of revival. Every one knows that we forget 
 many of the words of a language when we have given up read- 
 ing or speaking it for many years. So it is with an air we no 
 longer sing, with a piece of verse we no longer recite, with a 
 neighborhood we have been long absent from. Breaks occur 
 in the train of recollections, and go on increasing like the 
 holes in an old garment. We have no difficulty in seeing how 
 continuous and vast these destructions must be ; every day we 
 lose some of our recollections, three-fourths of those of the 
 preceding day, then others among those surviving from the 
 previous month, so that before long a whole month, or even 
 year, is only represented in our memory by certain prominent 
 images, like those few peaks still appearing in a submerged 
 continent, destined, at least the most of them, themselves to 
 disappear, since the gradual obliteration is owing to a contin- 
 uous flood, invading one by one the untouched crags, and spar- 
 ing nothing but a few rocks uplifted by some extraordinary 
 circumstances to a height no wave can reach. In fact, very 
 few of our sensations, even of those accompanied by attention, 
 are often repeated. Six months ago'I was talking to such a 
 person ; after I left him, and even on the following day, I could 
 have described his appearance and dress, have repeated the 
 principal topics of conversation ; but since then I have not re- 
 newed in experience or repeated in memory the images which 
 6
 
 82 OF IMAGES. [BOOK II. 
 
 then revived in me, intact and connectedly. They are obliter- 
 ated, and now, when by chance I find some fragment of the 
 distant scene, and stop to call up the rest, my efforts are vain. 
 So it happens with nearly all the portions of our experience: 
 the impression received has been a solitary one ; in a thousand 
 such, there is at most one which is twice repeated ; in a thou- 
 sand of the repeated ones, there is scarcely one whick is repeat- 
 ed twenty times. Some few only those of permanent objects 
 surrounding us of some twenty or thirty persons, pieces of 
 furniture, monuments, streets, landscapes, derive from constant 
 repetition a multiplied aptitude for revival. With the others, 
 the aptitude is too weak; when a fragment of distant experi- 
 ence, with which they were formerly connected, reappears, they 
 do not reappear with it ; the tendency which formerly called 
 them up is vanquished by other tendencies formed in the mean 
 while ; and the recent past blocks up the way of the earlier 
 past. 
 
 Finally, on the other hand, images grow dull by repetition, 
 as bodies are worn away by friction. If we see a person eight 
 or ten times, the outline of his form and expression of his face 
 become at last much less clear in our mind than on the day 
 after we have first seen him. So it is with a monument, a 
 street, a landscape, when seen many times at different hours 
 of the day, at evening, in the morning ; on a dull day, in rain, 
 under a bright sun, if we compare them with the same monu- 
 ment, landscape, or street, watched for three minutes, and then 
 replaced by some entirely different object. The impression, 
 so precise at first, becomes less so the second time. When I 
 imagine the monument, I find indeed the outline, which has 
 remained constant all the time, but the distribution of light 
 and shade, the changing nature of the tones, the look of the 
 gray or blackened pavement, the band of sky above grayish 
 and misty in the one case, dark and tarnished in the other ; 
 sometimes a bright white, sometimes a dark purple in short, 
 all the diversities which at different moments have connected 
 themselves with its permanent form, are mutually annulled. 
 And so, when I think of a person I know, my memory wavers 
 between twenty different expressions, smiling, serious, unhap- 
 py, the face bent on one side or the other. These different
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. 83 
 
 expressions form obstacles of each other ; my recollection is 
 far clearer when I have only seen him for a minute when, for 
 instance, I have looked at his photograph or picture. 
 
 In fact, when the image of the form we have perceived 
 tends to revive, it draws with it the images of its several ac- 
 companiments. But these accompaniments being different 
 cannot revive together ; the features of the same face cannot 
 be at once smiling and severe ; the fagade of the same palace 
 cannot be at once of an intense black, as when the sun is set- 
 ting behind it, and of a rosy brightness, as when it is rising in 
 front of it. Therefore, if these mutually excluding accompa- 
 niments have an equal tendency to revive, neither one nor the 
 other will do so, and we shall feel ourselves drawn in different 
 directions by contrary tendencies which come to nothing ; the 
 images will remain in an inchoate state, and will make up what 
 we call in ordinary language an impression. This impression 
 may be strong without ceasing to be vague ; beneath the in- 
 complete image a dull agitation is going on, and as it were, a 
 swarm of feeble impulses'which usually sum themselves up in 
 an expressive gesture, a metaphor, a visible summary. Such 
 is our usual state as regards things we have many times expe- 
 rienced ; a vague image, corresponding to a portion of our 
 different experiences, a heap of contrary tendencies of nearly 
 equal force, corresponding to their different circumstances, a 
 clear notation, denoting and concentrating the whole in an 
 idea. 
 
 This law of obliteration is of considerable extent, for it is 
 applicable not only to different appearances of the same object, 
 but also to different objects of the same class ; and all the ob- 
 jects in nature may be grouped in classes. A man who has 
 passed through an alley of poplars, and wishes to figure to 
 himself a poplar, or who, after seeing a large farm-yard, wishes 
 to figure to himself a hen, experiences a difficulty. His dif- 
 ferent recollections encroach upon each other ; the differences 
 which distinguished the two hundred poplars or the hundred 
 and fifty hens are mutually obliterated ; he will preserve a more 
 precise image if he has only seen a single poplar standing in 
 a meadow or a single hen roosting in ashed. All our images 
 undergo a similar blunting ; let the reader attempt to imagine
 
 84 OF IMAGES. [BOOK II. 
 
 a rabbit, a carp, a pike, a bull, a rose, a tulip, a birch tree 
 or any other object belonging to a numerous class and of 
 which he has seen many individuals, and on the other hand, 
 an elephant, a hippopotamus, a magnolia, an American aloe, 
 or any other object of a small class, and of which he has only 
 met with one or two specimens ; in the first case the image is 
 vague and all its surroundings have disappeared ; in the sec- 
 ond it is precise, and one is able to point out the spot in the 
 Jardin des Plantes, the Parisian Conservatory, the Italian villa, 
 where the object was seen. The multiplication of experience 
 is then a cause of obliteration, and images, by annulling one 
 another, thus fall into the state of dull tendencies hindered 
 by their contrariety and equality from assuming an ascend- 
 ancy. 
 
 V. Thus we arrive at a general conception of the history 
 of images, and, consequently, of ideas in a human mind. 
 Every sensation, weak or strong, every experience, great or 
 small, tends to revive by means of an internal image which 
 repeats it, and is itself capable of repeating, even after long 
 pauses, and this indefinitely. But as sensations are numer- 
 ous, and are at every moment replaced by others, without 
 truce or termination, up to the end of life, there is a conflict 
 of preponderance between these images, and, though all tend 
 to revive, those alone do so, which have the prerogatives re- 
 quired by the laws of revival ; all the others remain incom- 
 plete or null, according to the laws of obliteration. By force 
 of this double law, groups of efficacious aptitudes are constant- 
 ly becoming inefficacious, and images are falling from the state 
 of actual to that of possible existence. Thus, human memory 
 is like a vast reservoir, into which daily experience is continu- 
 ally pouring different streams of tepid waters ; these waters 
 being lighter than the others rest on the surface and cover 
 them ; then growing cold in their turn, they descend to the 
 bottom by portions and degrees, and it is the last flow that 
 constitutes the new surface. Sometimes a particular stream, 
 from being swollen or having a higher fall, warms ancient in- 
 ert layers below, and then they remount to the light ; the 
 chance of the flow and the laws of equilibrium have warmed a 
 certain layer so as to place it above the rest. The shape of
 
 CHAP II.] REVIVAL AND OBLITERATION OF IMAGES. $c 
 
 the reservoir, the accidents of temperature, the various quali- 
 ties of the water, sometimes even shocks of earthquake, all 
 bear part in this ; and many authentic instances show us deep 
 layers uplifted suddenly and entire to the surface, sometimes 
 superficial layers plunged suddenly and entire below. 
 
 In fact, images have, as we shall see later on, certain states 
 of brain as conditions of their being ; hence, we understand 
 how an injury, a rush of blood, a deterioration of blood, any 
 change of the cerebral substance, may hinder or promote the 
 arising of certain groups of images. " I descended on the 
 same day," says Sir Henry Holland,* " two very deep mines 
 in the Hartz mountains, remaining some hours underground 
 in each. While in the second mine, and exhausted both from 
 fatigue and inanition, I felt the utter impossibility of talking 
 longer with the German inspector who accompanied me. 
 Every German word and phrase deserted my recollection, 
 and it was not until I had taken food and wine, and been 
 some time at rest, that I regained them." Similar mischances 
 are not uncommon after brain fevers or great losses of blood. 
 A lady, says Winslow,f after large uterine haemorrhage, " had 
 forgotten where she lived, who her husband was, how long 
 she had been ill, the names of her children, and even her own 
 name. She was unable to give any thing its real name, and 
 in attempting to do so, made the most singular mistakes. 
 She had been accustomed, before her illness to speak French 
 instead of English. But afterwards she seemed to have lost 
 all knowledge of French ; for, when her husband addressed her 
 in that language, she did not appear to understand what he said 
 the least in the world, though she could converse in English 
 without difficulty," After seven or eight weeks these blanks 
 in her memory began to be restored ; and after some months 
 they were entirely filled up. So a gentleman, mentioned by 
 Abercrombie, " after a blow on the head, lost his knowledge 
 of Greek, and did not appear to have lost any thing 
 
 * " Chapters on Mental Physiology," p. 167, n. cited by Winslow, " Obscure 
 Diseases," etc. p. 252. 
 
 f Winslow, ibid., p. 344. 
 
 J " Inquiry into the Intellectual Powers," p. 152.
 
 86 OF IMAGES. [BOOK II. 
 
 The loss occasionally attaches to some period of former life. 
 " A clergyman, on recovering from an apoplectic attack, was 
 found to have lost the recollection of exactly four years ; every 
 thing that occurred before that period he remembered perfectly. 
 He gradually recovered."* Another patient, who had been 
 for some ten or twelve years in Edinburgh, recollected nothing 
 of that period of his life ; on the contrary, the earlier portion, 
 which had been passed in another country, was well remem- 
 bered by him. Lately, a celebrated Russian astronomer for- 
 got, in turn, the events of the previous day, then those of the 
 year, then those of the years last past, and so on, the chasm 
 gradually increasing, till at last he could only recollect the 
 events of his childhood. His case was considered hopeless ; 
 but by a sudden stop and unforeseen return, the blank filled 
 up in an inverted manner ; the events of his youth first reap- 
 pearing, then those of his manhood, and finally, the more 
 recent, those of the previous day. His memory was wholly 
 restored at the time of his death. 
 
 Gradual recoveries like these have also been observed after 
 violent falls ; and the fissure in the memory closes up some- 
 times from one end, sometimes from the other. " Some years 
 ago," says Abercrombie,f " I saw a boy who had fallen from 
 a wall, and struck his head against a stone which lay at the 
 foot of it. He was carried home in a state of insensibility, 
 from which he soon recovered, but without any recollection 
 of the accident. He felt that his head was hurt, but he had 
 no idea how he had received the injury. After a short time 
 he recollected that he had been on the top of a wall, and had 
 fallen from it and struck against the stone, but -could not re- 
 member where the wall was. After some time longer, he re- 
 covered the recollection of all the circumstances." Others 
 when injured forget the accident only, and not the circum- 
 stances ; others the circumstances only, but not the accident. 
 Sometimes the alteration is still stranger, and affects a cer- 
 tain class of associations only. " A lady,:}: after an apoplectic 
 attack, recovered correctly her ideas of things, but could not 
 
 * " Inquiry into the Intellectual Powers," p. 151. f Ibid > P- J 4. 
 
 J Ibid., p. 149.
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. g/ 
 
 name them. In giving directions respecting family matters, 
 she was quite distinct as to what she wished to be done, but 
 could make herself understood only by going through the 
 house, and pointing to the different articles. A gentleman 
 could not be made to understand the name of an object if it 
 was spoken to him, but understood it perfectly when it was 
 written. His mental faculties were so entire that he was en- 
 gaged in most extensive agricultural concerns, and he man- 
 aged them with perfect correctness by means of a remarkable 
 contrivance. He kept before him in the room where he 
 transacted business, a list of the words which were most apt 
 to occur in his intercourse with his workmen. When one of 
 these wished to communicate with him on any subject, he 
 first heard what the workman had to say, but without under- 
 standing him further than simply to catch the words. He 
 then turned to the words in his written list, and whenever 
 they met his eye He understood them perfectly."* 
 
 This suppression of ordinary aptitudes explains the revival 
 of lost aptitudes. One particular new organic disposition may 
 be unfavorable to the first ; and so, some other new organic 
 
 * See other analogous facts in the " Dictionnaire d'Histoire Naturelle," pub- 
 lished by M. Guerin, in an article by Grimaud de Caux. (Duval Jouve, " Logique," 
 
 P- 159- 
 
 " A man of sixty, in good health, who had had an ulcer in his leg for a con- 
 siderable time, permitted it to become closed. Before long he had a slight attack 
 of apoplexy, and this was followed by a loss of memory, first of certain words, then 
 of the French language. The remarkable thing was that he recollected perfectly 
 the Piedmontese language. 
 
 "A man of science on starting for Greece was thrown out of his carriage ; a 
 box, fortunately not a yery heavy one, fell on his head ; he suffered no pain, and 
 the skin was not broken ; but he completely forgot where he had ccme from, the 
 object of his journey, the day of the week, the dinner he had just made, and all his 
 acquired knowledge. In fact, he had forgotten the names of his relations and 
 friends, and could only recall his own, those of his children, and the symbol of 
 the Trinity. He was replaced in the carriage, in order that assistance might be 
 obtained, and, after half an hour's jolting over a stony road, suddenly recovered 
 himself." 
 
 Page 162 " Some persons forget proper names ; others, like Doctor Brousson- 
 nais. substantives. Dietrich tells the story of a man who, while recollecting facts 
 had forgotten half his words. There are instances of foreign languages, the facts 
 of history, dates, etc., being entirely forgotten, while other things were recol- 
 lected."
 
 88 OF IMAGES. [BOOK II. 
 
 disposition may be favorable to the second. The first cease 
 to be active, like a nerve suddenly paralysed ; the second be- 
 come active again, like a paralysed nerve suddenly electrified. 
 We have seen an instance of this in the case of the ignorant 
 young girl who, in her delirium, recited passages of Greek 
 and rabbinical Hebrew ; in the servant who, when seized with 
 fever, spoke Welsh, which, when well, she did not understand. 
 " A man," says Abercrombie, " born in France, had spent the 
 greater part of his life in England, and for many years had en- 
 tirely lost the habit of speaking French. When under the care 
 of Mr. Abernethy for an injury of the head, he always spoke 
 French."* In other cases a similar revival as to other lan- 
 guages has been observed. " An eminent medical friend," 
 says the same author, " informs me that during fever, without 
 any delirium, he on one occasion repeated long passages from 
 Homer, which he could not do when in health." Another 
 person, who, when well, had no capacity for music, and had 
 almost forgotten the Gaelic language, sang, during an illness, 
 Gaelic songs, and that with great precision, though the melody 
 was a difficult one, and he had previously been utterly incapa- 
 ble of singing it. 
 
 Let us now conceive the existence in the same person of 
 two distinct states, such as we have been describing ; let us 
 suppose that in the first a certain group of images, in the 
 second, some other group, can alone revive, what will happen 
 if in the two states the general organic disposition is different, 
 and if this difference is a clearly marked one ? The individual 
 will have two memories, the first recalling only the events of 
 the first state, and the second recalling only .the events of the 
 second state.f A young American lady, says Macnish,^: after 
 
 * Abercrombie, op. cit. 140, 142. 
 
 f " When people have been twice hypnotized, we find that they forget complete- 
 ly when they wake the acts and thoughts artificially produced, and recover perfect 
 recollection of them on re-entering the artificial state. Mr. Braid mentions having 
 seen intelligent persons who could recollect exactly and minutely all that had 
 happened during a state of sleep six years before, and who narrated this whenever 
 they were hypnotized, while, when awake, they had no recollection of it." " De 
 la Folie Artificielle," Dr. Tuke/" Annales Medico-Psychologiques," 46 Serie, vi. 
 P- 271. 
 
 \ Macnish, p. I 3, n. citing from " The Medical Repository." New York.
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. go 
 
 a prolonged sleep, lost the recollection of all she knew. She 
 was obliged to learn again how to spell, to read, to write, to 
 calculate, and to know the persons and objects around her. 
 A few months after, she was again seized with a deep sleep, 
 and when she woke she was restored to the state she was in 
 before the first sleep, having all the knowledge and recollec- 
 tions of her youth ; but on the other hand, having entirely 
 forgotten all that had passed between the two attacks. " Dur- 
 ing four years and upwards she has passed periodically from 
 one state to the other, always after a long and sound sleep 
 
 The former condition of her existence she now calls 
 
 the Old State, and the latter the New State ; and she is as 
 unconscious of her double character as two distinct persons 
 are of their respective natures. For example, in her old state 
 she possesses all the original knowledge ; in her new state 
 only what she acquired since. If a lady or gentleman be intro- 
 duced to her in the old state, or vice versa (and so of all other 
 matters), to know them satisfactorily she must learn them in 
 both states. In the old state, she possesses fine powers of 
 penmanship, while in the new, she writes a poor awkward 
 hand, not having had time or means to become expert. Both 
 the lady and her family are now capable of conducting the 
 affair without embarrassment. By simply knowing whether 
 she is in the old or new state, they regulate the intercourse, 
 and govern themselves accordingly." This double life is often 
 found in somnambulists.* The majority of them forget on 
 awaking all they have done in their sleep, and are surprised 
 to find themselves out of bed or in the street. But this forget- 
 fulness frequently ceases on a second attack. " The somnam- 
 bulist," says M. Maury, " takes up again the chain of ideas 
 interrupted while he was awake. Thus Dr. Mesnet's patient 
 carried out, during an attack, projects of suicide she had con- 
 ceived in a previous attack and forgotten during the lucid in- 
 terval ; in the second attack she recalled all the circumstances 
 of the first. M. Macario has cited a very significant example 
 of a young girl who was violated during a fit of somnambulism, 
 
 * Maury, " Du Sommeil," 210. Todd, " Cyclopaedia," Article " Sleep." Fuel, 
 " Memoire sur la Catalepsie."
 
 OO OF IMAGES. [BOOK II. 
 
 and who, on awaking, had no recollection or consciousness of 
 what had happened. It was only in a new fit that she related 
 to her mother the outrage committed upon her." In these 
 two instances, the wakeful state only recalled the wakeful 
 state ; the state of somnambulism only recalled the state of 
 somnambulism, and each of the two alternate lives formed a 
 separate whole. 
 
 Correspondences and separations 'like these, but partial 
 and temporary, are met with in ordinary life. " Mr. Combe 
 mentions the case of an Irish porter to a warehouse, who, in 
 one of his drunken fits, left a parcel at the wrong house, and 
 when sober could not recollect what he had done with it ; but 
 the next time he got drunk, he recollected where he had left 
 it, and went and recovered it."* M. Maury again mentions 
 cases of dreams forgotten when awake, and recalled in a new 
 state of sleep. On the other hand, our ordinary memory re- 
 calls only half our states. We recall our thoughts of yester- 
 day, but not those of the night while we were asleep ; how- 
 ever vivid they may have been, even when they have pro- 
 voked actions or the beginnings of actions, cries, gestures, and 
 all that an uneasy man does in his sleep, it is very unusual, 
 for us to be able on waking to recover any portions of them.f 
 It is a strange thing, we start from an intense dream, full of 
 emotions ; and it would seem that so violent a state ought to 
 be easily reproduced, even after a considerable time. Not at all ; 
 after two or three minutes the objects so clearly perceived 
 die away in clouds ; and these clouds vanish ; half an hour 
 afterwards I shall be scarcely able to relate my dream ; if I 
 want to remember it later on, I am obliged to write it down 
 at once. The fact is that the physiological state and the cir- 
 culation of blood in the brain are not alike in sleep and when 
 awake, and the second state, favorable to the recall of its 
 own images, is not favorable to the recall of the images of 
 the first state. 
 
 But whatever be the phenomenon, rudimentary and nor- 
 mal or abnormal and complete, it shows how our images, 
 by connecting themselves, make up the group which in liter- 
 
 * Macnish, " The Medical Repository," p. 55, n. f Ibid.
 
 CHAP. II.] REVIVAL AND OBLITERATION OF IMAGES. 9! 
 
 ary and judicial language we call the moral personality. If 
 two groups are distinctly severed, so that no element of the 
 one calls up any element of the other, we shall have, as in the 
 case of the lady cited by Macnish, two moral personalities in 
 the same individual. If in one of the two states the images 
 have exact and delicate associations, if as we see in the cases 
 of many somnambulists,* superior aptitudes show themselves, 
 if, as we observe in drunkenness and after many illnesses, the 
 passions take another degree and another direction, not only 
 will these moral personalities be distinct, but there will be 
 enormous disproportions and contradictions between them. 
 No doubt, though among somnambulists, persons hypnotized 
 and in states of ecstasy, similar contrasts distinguish the or- 
 dinary from the abnormal life, these two lives are not clearly 
 nor entirely distinct ; some images of the one always, or near- 
 ly always, introduce themselves into the other ; and, when 
 man is concerned, the supposition we have made remains 
 simply a conception of the mind. But, among animals, we 
 meet with instances in which it is exactly applicable ; such as 
 that of the patrachians, and of insects which undergo meta- 
 morphoses. Their organization and nervous system bring 
 forward in turn, by their transformations, two or three moral 
 personalities in the same individual : in the chrysalis, the 
 larva, and the butterfly, instincts, images, recollections, sen- 
 sations, and appetites, are all different ; the silkworm which 
 spins, and its moth which flies, the voracious larva of the cock- 
 chafer, with its terrible apparatus of stomachs, and the cock- 
 chafer itself, are two distinct states of the same being at two 
 epochs of its development, two distinct systems of sensations 
 and images engrafted on two distinct forms of the same ner- 
 vous substance. If a sleep like that of the chrysalis were to 
 overtake us in the midst of our life, and if we were to awake 
 with an organization and a nervous machinery as much trans- 
 formed as that of the worm which has become a butterfly, 
 the break between our two moral personalities would evident- 
 ly be as great in our case as with it. The reader can now see 
 the infinite consequences of that property of our sensations 
 
 * Maury, "The Medical Repository," p. 125.
 
 g 2 OF IMAGES. [BOOK II 
 
 and images which we have termed aptitude for revival ; it as- 
 sembles in groups our internal events, and in addition to the 
 continuity of physical being constituted by permanence of 
 form, it constitutes, by the return and connexion of images, 
 the continuity of the moral being.
 
 CHAP. I.j SENSATIONS OF HEARING, ETC. 03 
 
 BOOK III. 
 
 OP SENSATIONS. 
 
 CHAPTER I. 
 
 OF SENSATIONS OF HEARING AND THEIR ELEMENTS. 
 
 I. BY reduction upon reduction we have arrived at a fact, 
 primitive and apparently irreducible, of which all the rest, 
 whether images or ideas, are but repetitions more or less trans- 
 formed and disguised. I mean sensation, and before defining 
 it, that is to say, before showing its nature, we must first de- 
 scribe it, that is, must distinguish it and bring it to light, from 
 among the heap of facts in which it is comprised. When a 
 cutting instrument is plunged into our flesh, we feel pain, and 
 this pain, taken by itself and alone, is a sensation strictly so- 
 called. There are a number of such facts, similar in nature, 
 though differing in kind and degree ; such are the sensations 
 of contact, of pressure, of tickling, usually excited in us when 
 an external body touches, in a particular way, certain portions 
 of our bodies ; such are the sensations of temperature pro- 
 duced when a certain degree of heat is added to or taken away 
 from our ordinary temperature ; such are the sensations of mus- 
 cular activity, so called from their apprising us of the tension 
 or relaxation of our muscles ; such, in short, are the sensations 
 excited in us by the particular juices of an object we taste, 
 by the volatile particles of an object we smell, by the vibrations 
 of the air which strike our organs of hearing, by the vibrations 
 of light which strike our organs of sight, and which we com- 
 monly call sensations of taste, of smell, of sound, and of color. 
 
 Many of these names are ambiguous, and the words taste, 
 smell, sound, color, heat, sometimes denote a property, more 
 or less unknown to us, of surrounding bodies, of liquid or volatile
 
 94 OF SENSATIONS. [BOOK III. 
 
 particles, of vibrations of the air or of light ; sometimes, the 
 well-known kind of sensations which these bodies, particles, and 
 vibrations, excite in us. But the distinction is easily made ; 
 for the property appertains to the object and not to us, 
 while the sensation appertains to us and not to the object. 
 Lemon-juice has an acid taste ; this means that it possesses 
 an unknown property of exciting in us a well-known sensation, 
 that of an acid taste. This sheet of paper is white : this means 
 that by virtue of its particular texture, this sheet of paper, 
 when in the light, excites in us the sensation of the color white. 
 Two other distinctions less readily made are no less necessa- 
 ry. When we experience a sensation, we localize it ; we refer, 
 such a pain, such a feeling of heat, such a sensation of contact, 
 to the hand, to the leg, to such-and-such a part of the body, 
 such a sensation of smell to the interior of the nose, such a 
 sensation of taste to the palate, to the tongue, to the back of 
 the mouth. But, as we shall see later on, there is here an ul- 
 terior operation engendered by experience ; a group of images 
 has combined with the sensation to attribute to it this posi- 
 tion ; this group gives it a situation which really it has not, 
 and, in general, places it at the extremity of the nerve whose 
 action excites it. Sometimes again, a second operation re- 
 moves it to a still more distant place ; sounds and colors, which 
 are sensations only, at present appear to us situated, not in our 
 organs, but at a distance, in the air, or on the surface of ex- 
 ternal objects ; the reader will see, when we examine external 
 perception, how the education of the senses produces this ap- 
 parent recoil. Meanwhile, to understand the sensation prop- 
 erly, we must separate it from this accompaniment, must lay 
 aside the appendages which time has attached to it, and con- 
 sider it in its simple primitive state. Finally, we must distin- 
 guish it, at least provisionally, from the state of the nerve and 
 nervous centres by whose action it is produced. It is true 
 that this state is the sufficient and necessary condition of the 
 sensation, but their identity is not clear ; at first sight they 
 differ, and certainly are not known to us to the same extent 
 or in the same way. For the sensation is perceived directly, 
 completely, and at once, but the action of the nervous system 
 is proved indirectly, incompletely, and very slowly; an infinite
 
 CHAP. I.] SENSATIONS OF HEARING, ETC. 
 
 95 
 
 amount of anatomical and physiological research was required 
 to teach us that the sensation depended on it ; even now we 
 are wholly ignorant of what it consists, whether it is a propa- 
 gated vibration, an electric current, a chemical change, or what 
 else it may be. Strict method then requires us, for the pres- 
 ent, to leave it on one side and to study in the first place the 
 sensation apart. So circumscribed, it is that primary inter- 
 nal event, directly known to us, accompanied by images as- 
 sociated with it and localizing it, and excited by a certain 
 state of the nerves and nervous centres, a state unknown to 
 us, and consequent, in general, on the action of external ob- 
 jects. 
 
 II. Here we have a fact of supreme importance; for its 
 diversities and arrangements form the material of all our knowl- 
 edge. When we consider closely any one of our conceptions 
 that of a plant, an animal, a mineral we find that the primi- 
 tive threads of which it is woven are sensations, and sensations 
 only ; we shall see the proof of this later on. But we have it 
 already, if we recollect that our images are only reviving sen- 
 sations, that our ideas are nothing more than images which 
 have become signs, and that thus this elementary tissue sub- 
 sists, in a more or less disguised form, at all stages of our 
 thought. These primitive threads are of different kinds. Sen- 
 sations have long been, more or less happily, distributed, in 
 the ordinary method, into classes and sub-classes ; first, ac- 
 cording to the services they render us ; then, according to the 
 particular circumstances in which they arise, and the parts in 
 which the associated images induce us to place them; and 
 lastly, according to such rough similarities as internal observa- 
 tion can find in them.* A first group has been formed of 
 those which denote different states of the body in health or 
 sickness, and are stimulants to action, rather than elements of 
 knowledge ; these have been called sensations of organic life, 
 and have been divided into genera and species, according to 
 the organs or functions which excite them ; in one class, effort, 
 fatigue, and the different pains occasioned by states of the 
 
 * Gerdy, " Physiologic des Sensations et de 1'Intelligence." Bain, " Senses 
 and Intellect," 87, 250.
 
 96 OF SENSATIONS. [BOOK III. 
 
 muscles, bones, and tendons ; in another, nervous exhaustion 
 and the nervous sufferings occasioned by special states of the 
 nerves ; in another, the sufferings of thirst and hunger occa- 
 sioned by certain states of circulation and nutrition ; in another, 
 suffocation and the peculiar state of uneasiness occasioned by 
 a certain state of the respiration ; in another again, sensations 
 of cold and heat occasioned by a general state of all the organs ; 
 finally, in another, those, as of digestion, occasioned by states 
 of the alimentary canal. By the side of this group a second 
 has been formed, whose earlier classes come in contact with 
 the latter ones of the first group ; it comprises those sensations 
 which do not acquaint us with the healthy or unhealthy states 
 of our bodies, but are elements of knowledge, rather than stim- 
 ulants to action. These we call sensations of intellectual life, 
 and divide them, according to the special organs exciting them, 
 into sensations of smell, of taste, of touch, of hearing, and of 
 sight. In each of these genera there are species. In sensa- 
 tions of taste, distinctions are drawn between relishes* allied 
 to alimentary sensations, and provoking appetite or disgust, 
 according to the state of the stomach, and tastes strictly so 
 called, and themselves divisible into many groups, such as bit- 
 ter, sweet, salt, alkaline, acid, astringent. In sensations of 
 smell, distinctions are similarly drawn between smells connect- 
 ed with the respiratory sensations, compounded or mingled 
 with a sensation of freshness or closeness, and smells strict^ 
 so called, and themselves divisible into perfumed, foetid, pun- 
 gent, ethereal, etc. Similar classifications are adopted in the 
 distribution of the sensations of the other senses ; and slight 
 differences will be found in them, according to different 
 authors.f 
 
 But these differences are of little importance ; all they 
 afford us is a survey of the subject ; we have constructed a 
 convenient repository, with compartments enabling us to lay 
 our hands readily on the sensation we wish to consider ; but 
 this is all. We do not know what the sensation itself consists 
 
 * Relishes distinguished from tastes. Bain, " Senses and Intellect." 
 f See the physiological works of Longet, Mueller, Carpenter, Todd and Bow- 
 man, etc.
 
 CHAP I.] SEA T SATIONS OF HEARING, ETC. 
 
 97 
 
 in ; if we consider some particular one for instance, the smell 
 of a rose we find it comprised in the class of perfumed odors 
 with that of the lily, the violet, musk, and an infinite number 
 more. But while thus distinguishing it from others, we cannot 
 say in what it differs from them ; we vaguely perceive that it 
 is a stronger smell than that of the violet, and not so strong 
 as that of the lily ; our knowledge is reduced to this. We 
 cannot enumerate and state its elements as precisely as if it 
 were a question of two kinds of minerals or vegetables ; we 
 have no elements of comparison, like magnitude, form, posi- 
 tion, number, to sum up and connect together ; mathematical 
 and geometrical qualities, which serve as a foundation for the 
 physical sciences, fail us here. And here, again, the ground 
 from which we started to construct the moral sciences fails us 
 also. We have not here those common elements, images, 
 representations, general ideas, to which different human in- 
 ventions and social combinations -may be reduced. We are 
 at the central point of knowledge, a kind of link placed be- 
 tween the infinite ramifications of the branch and those of the 
 root, enclosing in its narrow band the origin of the fibres which 
 above and below make up, by their multiplication and their 
 arrangement, the entire plant. But it is precisely because 
 our sensations are elements of which all the rest is composed, 
 that we are unable to decompose them like the rest ; we can- 
 not find elements of these elements. We are able to show 
 how with them we form images, representations, and general 
 ideas how with them we form notions of magnitude, position, 
 form, and number ; but as to how they are themselves formed, 
 this we do not know. 
 
 It seems, then, that they escape from science ; and, in fact, 
 when we read works treating of them, we learn little but what 
 we knew before ; when we close the book, we find them well 
 arranged in our mind, and that is all. If we are taught any 
 thing, it is in another department, in physiology and anatomy, 
 by the knowledge of the apparatus, organs, and movements 
 on which they depend. Even with the highest hopes, all the 
 horizon shows us is a more extended knowledge of these ap- 
 paratus, movements, and organs ; perhaps some day, if the 
 microscope becomes more powerful, when the theories of elec- 
 7
 
 ^8 OF SENSATIONS. [BOOK III. 
 
 tricity, organic chemistry, and molecular physics have made 
 some great advance, experimentalists may be able to distin- 
 guish the different primitive fibres in a nerve, may define ex- 
 actly their internal movements, explain the structure of the 
 nervous centres, and state precisely what change of state the 
 action of the nerve excites there. Under the most favorable 
 circumstances, and supposing the science complete, we should 
 arrive at a mathematical formula enabling us to sum up in 
 some one law the different positions and relations of the nerv- 
 ous particles. But these advances, great as we imagine them 
 to be, add nothing to our idea of sensations ; they enlighten 
 us as to their conditions, but not as to them. If you describe 
 to me the molecular movement produced in the glosso-pha- 
 ryngeal nerves, and the other molecular movements conse- 
 quently developed in the nervous centres when a solution of 
 sugar or of colocynth passes over my tongue or throat ; you 
 will not teach me any thing as to the nature of the sensations 
 of sweet and bitter. I shall know the circumstances under 
 which they arise, I shall not know their elements, or even if 
 they have any. The most I shall perhaps find will be some 
 law connecting the intensity of bitterness with some form or 
 other of molecular movement, resembling the law which makes 
 the acuteness of a sound increase with the number of vibra- 
 tions transmitted to the auditory nerve. 
 
 The matter becomes still clearer when we compare two 
 sensations, not of the same, but of different senses, even when 
 both are produced by the same external cause ; for instance, 
 the tickling and the sound produced by the same vibrations 
 of the air, the painful feeling and luminous circle produced by 
 the same compression of the eye, the sensations of dazzling 
 light, of hissing sound, of shock, or tingling, produced by the 
 ' same electricity applied to different senses. Each one of these 
 senses forms a region apart ; neither smell, nor taste, nor color, 
 nor sound, nor sensation of contact, can be reduced to any 
 other ; and, in every sense, there are many regions no less 
 distinct from one another ; bitter, salt, and sweet tastes, like 
 blue, red, and yellow colors, like sensations of heat, pressure, 
 and tickling, seem equally irreducible to one another. The 
 only intrinsic quality which we find to be common to all these
 
 CHAP. I.] SENSATIONS OF HEARING, ETC. gg 
 
 distinct domains, is the degree of intensity ; every sensation 
 is capable of increase or decrease ; it is a stage in a magnitude ; 
 smell, taste, sound, brightness, pressure, may all be more or 
 less strong. So it is with the secondary groups comprised 
 in the principal ones ; every special sensation, that of bitter- 
 ness, of tickling, of blue, has a maximum and a minimum, on 
 passing which, it ceases, or becomes of another kind. But 
 each of them is a kind of simple body which, though capable 
 in itself of increase or diminution, is not convertible into any 
 of the others. In chemistry there are sixty-one such ; there 
 are many more for every sense, for instance, for smell or taste ; 
 for there is scarcely a single volatile odorous matter that does 
 not form a type apart ; we are sometimes able to arrange two, 
 or at most three other sensations, together with the sensation 
 it excites, as the smell of garlic and of the vapor of arsenic 
 with the smell of tin ; thus the species are innumerable, and 
 classes scarcely exist ; as we see on attempting to count the 
 smells of perfumed plants in a garden, or of disagreeable gases 
 in a laboratory. Thus it would seem that at the commence- 
 ment of psychology, we are obliged to set down a very great 
 number of facts as mutually irreducible, just as simple bodies 
 in chemistry, as the species of animals in zoology, or of vege- 
 tables in botany, but with this special disadvantage, that while 
 in chemistry, in botany, and zoology, differences and resem- 
 blances are constituted by homogeneous and precise elements, 
 number, force, and form, in the sensations, no such element 
 can be isolated, and we are driven to the unreasoning affirma- 
 tion of certain rough likenesses and to the dry statement of 
 an indefinite number of undefinable differences. 
 
 III. Sensations, however, have elements, as will appear 
 from various examples. We all know that in a musical chord 
 there are two notes, that an ordinary color is made up of 
 many colors ; we must advance a step, and see if those sensa- 
 tions of sound, color, and the rest, which appear to us sim- 
 ple, are not themselves composed of more simple sensations. 
 Psychology is at present confronted with sensations pro- 
 fessedly simple, just as chemistry was, at its outset, with pro- 
 fessedly simple bodies. In fact, in its early stages, observa- 
 tion, whether internal or external, perceives compounds only ;
 
 100 OF SENSATIONS. [BOOK III. 
 
 its business is to decompose them into their elements, to show 
 the different groupings these elements are capable of, and to 
 construct different compounds with them. The chemist shows 
 that, by the combination of a proportion of nitrogen with one, 
 two, three, four, or five, proportions of oxgen, we form pro- 
 toxide of nitrogen, deutoxide of nitrogen, nitrous acid, hypo- 
 nitric acid, and nitric acid ; fivesubstances which, to ordinary 
 observation, have nothing in common, and which, neverthe- 
 less, differ only in the number of proportions of oxgen com- 
 prised in each of their atoms. The psychologist has to inquire 
 whether, by combining such-and-such an elementary sensation 
 with one, two, three, other elementary sensations, by approx- 
 imating the times of their occurrence, by giving them a longer 
 or shorter duration, by communicating to them a greater or 
 less intensity, he cannot arrive at constructing those masses 
 of sensation to which rude consciousness attains, and which, 
 though irreducible to her, differ only in the duration, prox- 
 imity, magnitude, and number of their elements. 
 
 Now there is a group of sensations in which a complete 
 reduction can be effected namely, those of hearing ; and we 
 may legitimately argue from these to others ; the partial so- 
 lution attained indicates a general solution which may be at- 
 tained. The kinds of sounds are apparently very numerous ; 
 and ordinary observation detects in them many seemingly 
 simple qualities. Two sounds produced by the same instru- 
 ment may be respectively high and low. Two sounds equally 
 high or low have different tones, if produced, one by a violin, 
 and the other by a flute. Two sounds equally high or low, 
 and of the same tone, may be more or less loud or intense. 
 Two sounds may be, the one musical, the other unmusical ; 
 that is to say, the one may be a continuous sensation, all 
 whose parts are mutually alike ; while the other is a discontin- 
 uous sensation, and made up of parts differing from one 
 another. Finally, this last class contains many kinds appar- 
 ently irreducible to one another ; explosions, clangings, grind- 
 ings, hummings, rustlings, which we can only denote by the 
 body and external condition producing them, as the sound of 
 a hammer, of a glass, of a piece of wood, of crumpled paper, 
 etc. In this great collection we distinguish two qualities
 
 CHAP. I.] SENSATIONS OF HEARING, ETC. IOI 
 
 capable of degrees intensity, and acuteness ; in these respects, 
 different sounds form a scale ; in all other respects, they are 
 in juxtaposition, are vaguely related to one another, like smells 
 and tastes, without it being possible to say in what this rela- 
 tionship consists ; tone, for instance, like noise, is a thing un- 
 definable. The same sol played with the same strength 
 on a clarionet, a flute, a violin, a horn, a bassoon, borrows a 
 special character according to the different instruments ; it is 
 more piercing on the violin, more brilliant on the horn, sweeter 
 on the flute, keener on the clarionet, more veiled on the bas- 
 soon. But none of these adjectives define it ; they only indi- 
 cate some distant analogy between our total impression and 
 impressions of another nature ; they are simply literary labels 
 like the names we apply to perfumes, when we call the smell 
 of the heliotrope delicate, that of the lily, full and rich, of 
 musk, penetrating, etc. These epithets tell us something of 
 our sensation, but very little ; in no case do they tell us any 
 thing of the elementary sensations, of which our whole sensa- 
 tion is made up. 
 
 Fortunately, students of physics and physiology have ad- 
 vanced our researches while pursuing their own ; and their 
 discoveries as to undulations and the nerves enable us to find 
 what we are seeking. The sensation of sound is excited by 
 the concussion of the acoustic nerve, occasioned, in most cases, 
 by the vibration of the external air ; we further observe, in 
 fact, that when precisely similar concussions are occasioned, 
 precisely similar sensations of sound are produced. This is 
 the case with the sirens of Cagniard Latour and Helmholtz, 
 and the wheel of Savart. When this wheel is turned at a 
 uniform rate, its teeth, which are at equal distances, strike a 
 bar in passing ; arid this regular succession of similar concus- 
 sions excites a regular succession of similar sensations of sound. 
 Now, while the wheel turns sufficiently slowly, the sensations, 
 being discontinuous, are distinct ; and each of them, being 
 compound, is a sound. But when the wheel is set to turn fast 
 enough, a new sensation arises, that of a musical note. It dis- 
 tinguishes itself from the remains of the noises which still go 
 on and continue distinct, and stands out as a fact of a different 
 kind ; among the different elementary sensations which make
 
 IO 2 OF SENSATIONS. [BOOK III. 
 
 up each sound, there is one which the operation has separated ; 
 and this now ceases to be distinct from the similar elementary 
 sensation following in each of the succeeding sounds. All 
 these similar sensations now combine in one long continuous 
 sensation; their mutual limits are effaced; experience, just as 
 in a chemical analysis, has extracted an elementary sensation 
 from the complex group in which it was included, has joined 
 it to an absolutely similar elementary sensation, and formed a 
 new compound, the sensation of musical sound.* 
 
 But if, among musical sounds, we choose a very deep one, 
 for instance, the lower octave of the organ, we see that the 
 elementary sensations, though still forming a continuous whole 
 which they must do for the sound to be musical neverthe- 
 less remain to a certain extent distinct. " The lower the 
 note, the better does the ear distinguish in it the successive 
 pulsations of the air."f It is then not much removed from a 
 buzzing, that is to say, a simple noise. We distinguish in it 
 elementary sensations ; we recognize that each of them con- 
 sists in a swelling and a dying away, that is to say, in an in 
 crease and a diminution of intensity ; we can observe the 
 limits of each one of them ; these limits are but half effaced. 
 We find, on comparing it with the elementary sensation cor- 
 responding to a more acute note, that it occupies a greater 
 length of time. Again, the length of time is greater between 
 the maximum of height of one of its elementary sensations, 
 and the maximum of height of the succeeding one. The whole 
 sensation is thus composed of larger molecules and more dis- 
 tant maxima. This is why we call it a fuller or heavier sound. 
 Here we perceive the elementary sensation whose different 
 combinations are sufficient to explain all the sensations of 
 sound. 
 
 Let us first consider musical sounds. We know by acous- 
 tics that the condition of a sound being musical is that there 
 be a uniform series of vibrations of the air; that each of these 
 
 * Mueller (tr. Baly), ii. 973 and 1298. The wheel of Savart shows us that a sec- 
 ond elementary sensation is necessary and sufficient to effect this extraction and form 
 the new compound. 
 
 f Helmholtz, " Conferences Scientifiques de Bonn." " Revue des Cours Scien- 
 tifiques," zoth February, 1867, p. 78.
 
 CHAP. I.] SENSATIONS OF HEADING, ETC. JO7 
 
 vibrations is of certain length, and lasts a certain fraction of a 
 second ; that the more it diminishes in length and duration, 
 the more acute becomes the note. All analogies show that 
 there are elementary sensations in this case, .just as in that of 
 the very deep note, and scientific experiment comes in to con- 
 firm these inductions. Take a wheel with two thousand teeth 
 revolving in a second ; it gives two thousand blows in a 
 second, and therefore two blows in the thousandth part of 
 a second ; if all the teeth except two adjoining ones are now 
 removed, the two blows which it will give when set going 
 again will only occupy the thousandth part of a second.* Now 
 these two blows cause a determinate and appreciable sound. 
 The sound, then, given in a second by the wheel when it has 
 all its teeth, comprises a thousand similar successive sounds, 
 each perceptible to consciousness. In other words, the whole 
 sensation which lasts a second, is made up of a continuous 
 series of a thousand similar sensations, each lasting one-thou r 
 sandth part of a second, and each perceptible to consciousness. 
 But as we have just seen, each one of them comprises in it- 
 self at least two successive elementary sensations, which, if 
 isolated, would not come within our consciousness and, to be per- 
 ceptible, must be combined in pairs. Here we have the ele- 
 ments of a sensation lasting a second, and the elements of its 
 elements. 
 
 Now, in the passage from the deep to the acute note, what 
 become of these elementary sensations of which we are con- 
 scious ? It is plain that each of them lasts less and less time 
 and that its maximum sound becomes nearer and nearer to 
 the maximum of the succeeding sound ; hence it will necessa- 
 rily become less and less distinct, and at last we shall cease to 
 perceive any maximum or minimum in it ; this is what hap- 
 pens ; in proportion as the note becomes acute, the number 
 and plurality still apparent, though indistinctly, in the low note, 
 disappear and wholly vanish. Consciousness no longer distin- 
 guishes, even vaguely, the little composing sensations ; the 
 whole sound appears one and united. At the same time, 
 it puts on a new appearance, it seems thinner and more drawn 
 
 * Mueller (tr. Baly), ii. 973 and 1298, Experiments of Savart.
 
 104 OF SENSATIONS. [BOOK III. 
 
 out. This arises from the closer arrangement of the maxima, 
 and from the shorter time occupied by the molecules of the 
 sensation, which, though as numerous as before, are smaller. 
 It follows that, as regards consciousness, our sensations of 
 sound arrange themselves in a pyramid : at the base, are those 
 of very deep sound, composed of longer elementary sensations 
 and more distant maxima ; at the summit, are those of very 
 acute sound, composed of shorter elementary sensations and 
 of more closely ranged maxima ; this is why we say of sounds 
 that some are higher and some lower, and arrange them in a 
 scale. Hence we see that the qualities of deep or acute, of 
 high or low, of full or drawn out, of vibrating or firm, by which 
 we distinguish the different notes of the scale, depend on the 
 degree of brevity of the elementary sensation, and the degree 
 of proximity of its maxima. Here, already, we have reduced 
 quality to quantity. 
 
 IV. It is also thus reducible in other respects. First, as to 
 intensity, the reduction is complete. The different degrees of 
 force or intensity of anyone sensation of sound are the different 
 degrees by which it passes from its minimum to its maximum, 
 and we know that these degrees have as their necessary and 
 sufficient condition different degrees of condensation of the 
 wave of air. Now, mathematics show us that in each element- 
 ary wave, there is a maximum and a minimum of condensation, 
 which explains how it is we find in each elementary sensation a 
 maximum and a minimum of intensity. Mathematics further 
 show that in the two series of waves produced by two notes 
 sounded in unison, the condensations combine and become of 
 double strength ; which explains how it is that in the sensa- 
 tions of sound so produced the intensities combine and be- 
 come doubly as great. Consequently, when we are given the 
 law connecting the elementary sensation with its condition, 
 we are able to follow the elementary sensation under all its 
 aspects and in all its degrees, far above the range of con- 
 sciousness, by following mathematically the changes and de- 
 grees of its condition. 
 
 In the second place, an indirect analysis comes to our aid 
 to explain with the most complete success that undefinable 
 quality which seemed to resist all the efforts of direct analysis,
 
 CHAP. I.] SENSATIONS OF HEARING, ETC. IO 5 
 
 tone.* If the same note is played by various instruments of 
 different tone, it is not a simple sound but a combination of 
 sounds, of which the principal one the same for all the instru- 
 ments is the fundamental note ; and the others, varying 
 with particular instruments, are supplementary notes of less 
 strength, termed superior harmonics, arising from vibrations 
 twice, three, four, five, six, seven, eight, nine, or ten times as 
 quick as those of the fundamental note, Thus, in the piano, 
 we can hear without difficulty the six first harmonics of each 
 note, but not the seventh or ninth. The violin, under the 
 bow, gives the six first harmonics more feebly ; but the higher 
 ones, from the sixth to the tenth, are very distinct. The pipes 
 of covered organs give a hollow sound, arising from the isola- 
 tion of the odd harmonics. The clarionet gives a nasal sound, 
 in which again there are only the odd harmonics ; but of these, 
 the higher ones predominate. Hence it follows that differences 
 of tone arise from the addition of different harmonics to the 
 fundamental note. By following out this principle, and with 
 the aid of an instrument called a resonnateur, it has been 
 proved that this same circumstance explains the different 
 vowel-sounds of the human voice that is to say, the varia- 
 tions which the same note presents, when pronounced in turn 
 u, a, e, i, o, eu, ou. Analogous considerations shows us how 
 sounds become either harsh and rough, or smooth and even. 
 So that these differences of sensation hitherto irreducible, and 
 denoted by idle metaphors, are reduced to the intervention of 
 little subsidiary and complementary sensations of the same 
 kind, which, attaching themselves to the principal sensation, 
 give it a special character and unique appearance, while con- 
 sciousness, which sees the whole and nothing but the whole, 
 is unable to distinguish these feeble auxiliaries, and there- 
 fore to recognize that, though inferior in strength to the prin- 
 cipal sensation, they are, in nature, identical with it, and that, 
 while entirely similar to one another, they differ only, accord- 
 ing to the tone, in number and acuteness. 
 
 This being settled, we are in a position to explain sensa- 
 tions of noise, and their innumerable varieties. The science 
 
 Helmholtz, " Die Lehre von den Tonempfindungen."
 
 106 OF SENSATIONS. [BOOK III. 
 
 of acoustics shows us their general mode of formation, though 
 without entering into the details of each particular one. Like 
 sensations of musical sounds, they are compound. But while 
 the sensation of musical sound corresponds to a series of 
 vibrations, equal in length and duration, that of noise corre- 
 sponds to a series of vibrations, unequal in duration and length ; 
 and hence we conclude that in the first instance the elementary 
 sensations are similar, and in the second dissimilar ; and this 
 explains the infinite number of sensations of noise and the im- 
 possibility of grouping them Ifke those of musical sound in a 
 single series ; there are no limits to the combinations of dis- 
 similar sounds ; having no fixed relations between themselves, 
 they can only produce a chaos. 
 
 We see now in what all the differences and peculiarities of 
 sounds consist. Given two continuous elementary sensations, 
 the one preceding and the other following, the two united 
 form, as far as consciousness is concerned, a single whole sen- 
 sation, which we term a sensation of sound. If the two are 
 similar, the sound is musical ; if they are dissimilar, it is a 
 noise. If, in the couple so formed, the elements are of longer 
 duration, the sound is deeper ; if of shorter duration, the sound 
 is more acute. In every elementary sensation, there is a 
 maximum ; and according as the time between two maxima 
 diminishes, the sound becomes more even. If the maxima of 
 one couple are greater than those of another, the whole sound 
 of the first couple is more intense than the whole sound of the 
 second. If to the whole sound be added complementary 
 sounds, less intense, and twice, three, four, or several times 
 as acute, the tone varies with the variations of the comple- 
 mentaries. If we conceive two given elements, on the one 
 hand, the elementary sensation, on the other, the quantity 
 we call time ; we have in them the materials necessary to con- 
 struct sensations of sound. Two elementary sensations are 
 discontinuous, or continuous, that is to say, are separated by 
 an appreciable or unappreciable portion of this quantity ; and 
 the sound is accordingly null or appreciable. They occupy 
 equal or unequal portions of this quantity ; and the sound is 
 accordingly musical or not musical. The portions so occu- 
 pied are larger or smaller ; and the sound accordingly becomes
 
 CHAP. I.] SENSATIONS OF HEARING, ETC. IO7 
 
 deeper or higher. If we now conceive the magnitude or in- 
 tensity of the elementary sensation itself, with this new ele- 
 ment, the construction is accomplished. The elementary sen- 
 sation having a maximum of intensity, the maxima of two 
 elementary sensations may be discontinuous or continuous, 
 that is to say, separated by an appreciable portion of time 
 or not ; and the sensation is accordingly composed of ap- 
 preciable portions, or uniform. The maxima of two elemen- 
 tary sensations are greater or less than the maxima of two 
 others ; and the sound is accordingly more or less intense. 
 There are added to a sound different groups of sounds of less 
 intensity, but of an acuteness the multiple of its own ; and 
 the sound has such-and-such a tone accordingly. So that all 
 differences of sound, though apparently irreducible, are re- 
 duced to differences of magnitude introduced into the same 
 elementary sensation, these differences being furnished some- 
 times by the magnitude or intensity of the sensation itself, 
 sometimes by that particular magnitude we denominate time. 
 Let us now consider the elementary sensation itself. In 
 the noise which precedes the musical note,* it is united with 
 other elementary sensations of unequal duration, and forms 
 with them a heterogeneous compound. In the musical note 
 which is formed by accelerated and approximating noises, it 
 is united with other elementary sensations, of duration equal 
 to its own, and forms with them a homogeneous compound. 
 But for it to reach our consciousness there must always be 
 one or other of these combinations ; it must be enlarged in 
 order to be distinguished. When isolated, the inner sense 
 does not perceive it ; but it still exists, for in the very deep 
 musical note we perceive it incessantly repeated and making 
 up the note ; and again, there can clearly be no compound 
 without components. On the other hand, we have seen that 
 in the high as in the low note, the elementary sensation has a 
 maximum ; we discover this maximum in the very low note, 
 we do not discover it in the high note ; still it exists in the 
 one as in the other ; but, in the very low note, the greater 
 interval between the two maxima enables us to distinguish 
 
 * See the Wheel of Savart, and the Sirens.
 
 I0 g OF SENSATIONS. [BOOK III. 
 
 them, while, in the high note, their proximity prevents our 
 doing so. Further than this, every elementary sensation, in 
 order to pass from its minimum to its maximum, passes in 
 its short duration through an infinite number of degrees ; 
 much more therefore are these degrees insensible to con- 
 sciousness; so that, in a high note, the indistinct elementary 
 sensation comprehends not only two indistinct extreme states, 
 but an infinite number of indistinct intermediate states. 
 
 We get a glance here at the obscure and infinite world 
 extending beneath our distinct sensations. These are com- 
 pounds and wholes. For their elements to be perceptible to 
 consciousness, it is necessary for them to be added together, 
 and so to acquire a certain bulk, and to occupy a certain time ; 
 if their group does not attain this bulk and does not last this 
 time, we observe no change in our state. Nevertheless, though 
 it escapes us, there is one ; our internal sight has limits ; outside 
 these limits, internal events, though real, are for us as though 
 they did not exist. They gain accessions, they undergo dim- 
 inutions, they combine, they are decomposed, without our 
 being conscious of it.* They may even, as we have just seen 
 in the case of sensations of sound, have different degrees of 
 composition, and consequently different degrees of recoil, be- 
 yond the grasp of consciousness. The elementary sensations 
 directly making up our ordinary sensations are themselves 
 compounded of sensations of less intensity and duration, and 
 so on. Thus, there is going on within us a subterranean pro- 
 cess of infinite extent, its products alone are known to us and are 
 only known to us in the mass. As to elements and their ele- 
 ments, consciousness does not attain to them, reasoning con- 
 
 * Leibnitz, " Des Perceptions Insensibles," p 65, " Nouveaux Essais sur 
 1'Entendement, " Ed. Jacques. 
 
 "To hear the sound of the sea, from the shore, we must necessarily hear the parts 
 which make up the whole, that is to say, the noise of each wave, though each of 
 these little noises only makes itself known to us in the confused assemblage of the 
 whole, and wonld not be observed if the wave causing it were alone by itself. For 
 we must be affected a little by the movement of this wave, and must have some 
 perception of its sound, however slight ; otherwise we should have none of the 
 sound of a hundred thousand such, since a hundred thousand nothings cannot 
 make up any thing." Cf. Hamilton, Lectures, etc., i. 349-351, cited Mervoyer, 
 " De 1'Association des Idees," p. 337.
 
 CHAP. I.J SENSATIONS OF HEARING, ETC. IO Q 
 
 eludes that they exist ; they are to sensations what secondary 
 molecules and primitive atoms are to bodies ; we have but an 
 abstract conception of them, and what represents them to us 
 is not an image, but a notation.
 
 HO OF SENSATIONS. [BOOK III 
 
 CHAPTER II. 
 
 SENSATIONS OF SIGHT, OF SMELL, OF TASTE, OF TOUCH, AND 
 THEIR ELEMENTS. 
 
 I. A SIMILAR, though somewhat less complete, reduction 
 may be effected with sensations of sight.* We all know that 
 a ray of white light may be divided with a prism into several 
 rays of different colors. It spreads out into a spectrum, in 
 which the colors form a continuous scale. At the commence- 
 ment of the scale is red ; then come orange and the different 
 yellows, then green, the different blues, indigo, and lastly vio- 
 let,f and each of these tints passes by intermediate stages into 
 the one preceding it and the one following it. Here are an 
 infinite number of distinct sensations connected by inter- 
 mediate stages. Let us examine their external conditions. 
 The science of optics shows us that the spectrum is formed 
 by the different rays which make up the white ray being in- 
 flected, some more and some less, in passing through the 
 prism ; this inflection increases with the shortness and rapidity 
 of the waves ; therefore, if we follow, from red to violet, the 
 series of rays which form the spectrum, we find that the short- 
 ening and acceleration of the waves go on increasing. Thus, 
 from red to violet, each sensation corresponds to waves quicker 
 and shorter than those of the preceding sensation, slower and 
 longer than those of the succeeding sensation. An increase 
 of speed and diminution of length in the waves are sufficient 
 r to determine the variations which our sensation of color un- 
 goes in passing from red to violet. 
 
 Having premised this, let us consider the red ; as we go 
 
 * Helmholtz, " Physiologische Optik," part ii. 
 
 f M. Helmholtz distinguishes the following successive colors : red, orange, 
 golden yellow, pure yellow, greenish-yellow, pure green, bluish-green, blue of wa- 
 ter, cyanic blue, indigo, violet and ultra-violet.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. ni 
 
 down the spectrum, the sensation of red diminishes, it passes 
 from its maximum to its minimum. There is then an elemen- 
 tary sensation, which decreases in proportion as the waves be- 
 come "shorter and more rapid. But there is more than one 
 such ; for if there were only one, we should find that as we 
 passed towards violet, it would simply grow feebler with the 
 shortening and acceleration of the waves, and the entire spec- 
 trum would only present degrees of intensity of red, while in 
 fact, we find at what appears to be the minimum of red, a second 
 distinct sensation arising, that of yellow. There are then, 
 at least two elementary sensations of color. Are there but 
 two? If there were only two, for instance, that of red and 
 that of yellow, the red, having its maximum at the commence- 
 ment of the spectrum, and the yellow having its maximum at 
 the centre of yellow, the first decreasing with the time and 
 length of the waves, the second decreasing whenever the time 
 and length of the waves are less or greater than the degree 
 of time and length corresponding to the centre of yellow, we 
 should see, on passing down the spectrum below this centre, 
 yellow become indefinitely feebler till the end of the spectrum, 
 without undergoing any other change. This is not so ; for 
 at the lower minimum of yellow we find a new distinct sensa- 
 tion appear, that of green. There are then, at least three 
 elementary sensations, and on studying the composition of 
 the spectrum we find it is sufficient to admit three, one analo- 
 gous to that of red, another to that of violet, and the last to 
 that of green. 
 
 All the three are excited by every ray of the spectrum ; 
 but each of the three is differently excited by the same ray. 
 The first is at its maximum at about the central point of 
 red ; in proportion as we descend towards the violet and the 
 waves become shorter and more rapid, its intensity diminishes 
 and approaches its minimum. The second is at its maximum 
 at about the centre of the violet ; and as we go back towards 
 the red, and its waves become longer and slower, its intensity 
 diminishes and approaches its minimum. The third is at its 
 maximum at about the central point of the green ; in pro- 
 portion as we return towards the red, or descend towards the 
 violet, that is to say, as the waves become either longer and
 
 112 OF SENSATIONS. [BOOK III. 
 
 slower, or shorter and more rapid, its intensity diminishes and 
 approaches a minimum. So that, as we pass from red to 
 violet through all the degrees of the spectrum, the three com- 
 ponent sensations vary from degree to degree, but each one 
 in a special manner, the first passing insensibly from maxi- 
 mum to minimum, the second from minimum to maximum, 
 the third passing first from a minimum to its maximum, and 
 then from its maximum to a minimum, which explains at the 
 same time the insensible passage by which every compound 
 sensation in the spectrum is connected with the succeeding 
 one, and the diversities of the ten or twelve principal com- 
 pound sensations.* 
 
 We can readily see the object of this disposition of our be- 
 ing. If a simple ray excised in us one sensation of color only, 
 it \vould have a maximum, a minimum, and intermediate 
 stages, nothing more ; and for want of being able to contrast 
 it with another, we should not observe it ;f we should have 
 no notion of color; the luminous waves, in increasing or de- 
 crdasing in speed and length, would only render the sensation 
 more intense or more feeble ; objects would differ only in high- 
 er or fainter color ; they would resemble the various parts of 
 a drawing in which all the differences are those of white, gray, 
 and black. If, on the other hand, every simple ray excited 
 two sensations of color only, we should still have the notion 
 
 * Helmholtz, ib., 191. The substance of this explanation is due to Young. 
 He supposes that every nervous fibre of the retina is made up of three elementary 
 fibres, differently excitable by the same ray. As Helmholtz observes, we may sup- 
 pose that every nervous fibre of the retina possesses three different kinds of activity, 
 excitable by the same ray, and this is very probable. But we may dispense with 
 all suppositions by admitting, instead of three nervous fibres or three nervous activ- 
 ities, three elementary sensations. In the anatomical or physiological hypothesis, 
 the assumed fact is uncertain ; for it is not certain that there are three different 
 fibres in every nerve, or that one fibre has three kinds of action. In the psycho- 
 logical explanation, the admitted fact is positive ; for it is certain that the three 
 sensations, red, green, and violet, exist. I have therefore made the necessary 
 changes in the explanation of Helmholtz. " This hypothesis of Young's," he says, 
 gives a complete view and extraordinarily clear and simple explanation of all the 
 phenomena connected with the physiological science of colors." 
 
 f " Persons affected with achromatopsy can only distinguish degrees of light 
 and dark, they see all objects as they are represented in photography." Wecker, 
 " Maladies des Yeux," ii. 432.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. ll ^ 
 
 of color ; we should still distinguish two principal colors, their 
 maxima, minima, intermediates and compounds ; but very 
 many of our sensations of color would be wanting, and their 
 whole arrangement would be reversed. This we observe in 
 studying various cases of illness or congenital infirmity, and 
 the theory reducing our elementary sensations of color to the 
 three sensations of red, violet, and green, receives here a most 
 striking confirmation from experience.' 55 ' The sensation of red 
 is wanting in some persons ; in others, that of green ; after 
 taking santonine, the sensation of violet is lost for some hours. 
 In all these cases, not only is a principal sensation missing, 
 but many others are altered, and both losses and alterations 
 are precisely those which, according to theory, would result 
 from the absence of the elementary sensation. Finally, we 
 obtain a more delicate and definitive verification.-)- Accord- 
 ing to the theory, the red and violet of the spectrum are, even 
 at the points at which they seem most intense, compound sen- 
 sations ; for, to the elementary sensation which is then at its 
 maximum, are joined two others which are then at a minimum ; 
 the first then is mingled and weakened ; it is neither absolute- 
 ly pure nor of the greatest possible strength. It will, then, 
 be purer and stronger if we can remove these causes of impu- 
 rity and weakness. Now there is a case in which we are able 
 to do this ; that is, when we have blunted the sensibility of 
 the eye to the other colors. In this case we ought to see a red 
 or violet more intense than those of the spectrum ; and this 
 is what happens. In this instance, which is unique, we are 
 able to isolate one of our elementary sensations of color. By 
 a lucky hit in psychological chemistry, we extract it from the 
 ternary compound in which it is usually combined, and in which 
 theory alone had detected it. 
 
 * Helmholtz, 294, 848, 293, and Wecker, ibid. "The ingestion of santonine 
 brings on a particular variety of Daltonism by making the retina insensible to vi- 
 olet rays. . . ." Some persons " have no perception of blue ; this state always 
 coincides with insensibility of the retina to red rays. ' Others while distinguishing 
 white, gray, and black from all other colors, do not distinguish other colors, 
 from one another. In others, the retina is insensible to violet, while other colors 
 are perceived, if strongly marked and in a bright light" 
 
 f Helmholtz, ib., 369, 370. 
 
 8
 
 OF SENSA TIONS. [BOOK III. 
 
 II. With the three elementary sensations of color we are 
 able to construct the rest. And first, if we represent by a 
 curve the increase and decrease which each of them undergoes 
 as it passes down the spectrum, we shall see the three differ- 
 ent variations of their respective intensities produce the differ- 
 ent colors of the spectrum.* The longest and slowest waves, 
 placed at the summit of the spectrum, excite the elementary 
 sensation of red strongly, and the two others feebly ; the re- 
 sult is the sensation of spectral red. Lower down, at the 
 point denoted by yellow, the waves, already not so long and 
 slow, excite the elementary sensations of red and green with 
 moderate intensity; and that of violet feebly; and then we 
 have the sensation of spectral yellow. Towards the middle 
 of the spectrum, the waves, which then have a medium length 
 and speed, excite the elementary sensation of green strongly, 
 and the others much more feebly ; our entire sensation is that 
 of spectral green. Lower down, when the waves begin to 
 grow short and quick, the elementary sensations of violet and 
 green are excited with moderate force, and that of red more 
 feebly ; then we see spectral blue. Towards the lowest part, 
 when the acceleration and shortening of the waves has fur- 
 ther increased, the elementary sensation of violet is strong, and 
 those of red and green are very weak ; and the compound sen- 
 sation we call violet is produced. 
 
 On the other hand, when the three elementary sensations 
 are of about equal force and no one predominates over the 
 others, we have the sensation of white, or of whitish colors. 
 This happens in many cases ; first, when all the rays of the 
 spectrum, collected again by another prism, strike the retina 
 at the same point, and thus produce the maximum, minimum, 
 and all the degrees of each elementary sensation ; again 
 when, two rays being selected from the spectrum, the inequal- 
 ity of the three elementary sensations excited by the first is 
 compensated by the inverse inequality of the three elementa- 
 ry sensations excited by the second. In this case, the two 
 spectral colors produced by the two rays are said to be com- 
 plementary to one another, and they form a distinct couple. 
 
 * Helmholtz, 291.
 
 CHAP II.] SENSATIONS OF SIGHT, ETC. jje 
 
 Among such couples we reckon four principal ones, red and 
 bluish-green, orange and cyanic blue, yellow and indigo, 
 greenish-yellow and violet ; combined in their respective pairs, 
 these colors give us the sensation of white, and we find a fix- 
 ed distance between such pairs on the spectrum. If, on the 
 contrary, we take the two colors at the furthest distance from 
 one another on the spectrum, red and violet, their mixture 
 produces a sensation of distinct color, that of purple. These 
 two observations afford us the law governing all mixtures of 
 spectral colors. Two colors being given for mixture, their 
 distance on the spectrum, compared with the fixed distance 
 between complementary colors, differs from it by a greater or 
 less quantity. The smaller this quantity is, the nearer to 
 white or whitish will be the color produced by the mixture ; 
 and on the contrary, the greater this quantity is, the freer 
 from white, or more " saturated," will the color formed by the 
 mixture be. On the other hand, this distance may exceed 
 or be less than the fixed distance. The more it exceeds the 
 fixed distance and the nearer it approaches to the extreme 
 possible distance, the nearer will the color formed by the mix- 
 ture approximate to purple, which is produced when the sep- 
 aration is most complete ; on the contrary, the further it is 
 below the fixed distance and the smaller the separation be- 
 comes, the more does the color produced approximate to the 
 intermediate color, in which the separation of the two compo- 
 nent spectral colors disappears.* All these conclusions are 
 confirmed by experience. 
 
 A last color remains, black, which is not a sensation, but 
 the absence of all sensation at a particular place and moment, 
 when this place and moment are compared with others in which 
 the sensation is present. But consciousness is so ill-acquaint- 
 ed with our internal events that she places in the same rank, 
 as colors, our sensations and our wants of sensation ; what 
 strike her are differences between our states, and, on account 
 of this, she sets together as similar facts the passage from re- 
 pose to action, and that from action to repose, observing them 
 as contrary, but without distinguishing that one is negative, 
 
 * Helmholtz, 279.
 
 IT 6 OF SENSATIONS. [BOOK III. 
 
 the other positive. The different degrees of black or of want 
 of sensation come in then to complicate the colors already 
 constructed. " Prismatic analysis proves that gray becomes 
 identical with white, brown with yellow, reddish brown with 
 red, olive green with green, when the white, yellow, red, and 
 green are feebly luminous." 
 
 These data being given, we have all the elements neces- 
 sary to explain all sensations of color, and we see the elements 
 of the sensation form compounds, which combining together 
 form more complex compounds, and so on, just as we see 
 physical atoms form chemical molecules, these form chemical 
 compounds, and these again, the ordinary minerals found in 
 nature. By our utmost analysis we arrive at three elementa- 
 ry colors, all simultaneously excited, though each one differ- 
 ently, by a simple ray of the prism. Their union forms a 
 spectral color. Many spectral colors united form, in accord- 
 ance with a fixed law, white, purple, and an infinite number 
 of compound colors ; and the addition of black, that is to say, 
 the enfeebling the whole sensation, introduces an infinity of 
 shades in all these products. These products themselves 
 form, by their combinations, the ordinary colors we observe 
 in the world surrounding us. 
 
 Positive science stops here ; experience does not enable 
 us to mount higher than the three elementary sensations of 
 color. We are dealing with an instrument far more compli- 
 cated than the sensation of hearing. In fact, for every undu- 
 lation we have three sensations instead of one. With sound 
 again, the vibrations sometimes succeed one another slowly 
 enough to enable us to distinguish the elementary sensation 
 corresponding to each of them ; there are only sixteen and a 
 half per second in the ut of an organ-pipe thirty-two feet long ; 
 and so we are able to observe that our whole sensation is made 
 up of successive small sensations having each a maximum and 
 minimum; we distinguish almost precisely these component 
 sensations. With sight, on the contrary, at the extremity of 
 red, the part of the spectrum where the vibrations succeed most 
 slowly,* there are 451 billions of them in a second ; it is plain 
 
 * Mueller (tr. Baly), ii. 1109, and Helmholtz, p. 32. 451 billions for the 
 slowest, 789 billions in the quickest.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. nj 
 
 that, were we able to isolate the sensation of red from the 
 two other elementary sensations, we could never distinguish 
 from one another component sensations so prodigiously nu- 
 merous and of so prodigiously short duration. All we can 
 admit with confidence is that the elementary sensation of red, 
 like that of the lowest note of ut, is composed of successive 
 sensations. For Wheatstone's experiments show that such 
 a light as that of the electric spark is enough to produce a 
 sensation on the retina ; that this light is, so to speak, instan- 
 taneous ; that it lasts less than the millionth of a second ; and 
 that thus a sensation of light lasting a second is made up of 
 at least a million successive sensations. The number of these 
 cannot be determined ; it is probably much greater ; perhaps 
 with the ethereal undulation, as with the undulation of air, 
 two successive vibrations are sufficient to produce a sensation 
 still perceptible to consciousness ; if so, the shortest sensation 
 of light perceptible to consciousness would as is the case 
 with the shortest sensation of hearing perceptible to con- 
 sciousness be compounded of two elementary sensations 
 imperceptible to consciousness, and having each a maximum 
 or minimum and intermediate stages. Without pushing the 
 induction to this extent, the case of the electric spark shows 
 that the sensation of light, like that of a very acute sound, is 
 composed of a continuous succession of very numerous, suc- 
 cessive, and similar sensations, forming, as far as we are con- 
 cerned, a simple undecomposable mass. A new proof of the 
 unnoticed work going on in the depth of our being, beyond 
 the range of our consciousness, and a new example of the 
 latent, complex, and innumerable combinations, of which we 
 only perceive the totals or the effects. 
 
 III. We must not expect to find such complete reductions 
 in the cases of taste and smell. With air, or ether, we know 
 the mode of action, which is an undulation of calculable length 
 and speed, and thus we are able to draw conclusions from it 
 to the corresponding sensations. Besides, this mode of action 
 is uniform, and the nerve, moreover, is specially constructed 
 to receive it ; we find proof of this in the designed structure of 
 the organism of which the nerve forms part, and in the simil- 
 itude of the sensations produced through the nerve by a blow
 
 Ug OF SENSATIONS. [BooK III. 
 
 or an electric current applied to the eye or ear. The nerve 
 itself, then, is capable of uniform action ; and so it is natural 
 that sensations excited by its action should be readily referable 
 to a simple type, as happens with those of sound, or to types 
 few in number, as with those of color. With the other groups 
 of sensations all this is reversed. We are ignorant of the mode 
 of action of volatile substances on the olfactory nerves and of 
 liquefied substances on the gustatory nerves ; it is recognized 
 to be chemical, but here our knowledge stops ; we do not know 
 whether it is an undulation or what other movement ; we have 
 not the least idea of its elements, and are unable to avail our- 
 selves of such an idea to form conclusions as to the corre- 
 sponding sensations. And yet, from the single fact that it is 
 chemical, we may conclude something as to the composition 
 of the sensations it exites in us through the medium of the 
 nerve. 
 
 Before commencing this inquiry, we must distinguish sen- 
 sations of smell and taste, strictly so called, from accompanying 
 sensations. For, what we term a smell or taste is, in general, 
 a very complex sensation ; the olfactory or gustatory nerves 
 only contribute a part of it ; another very considerable part 
 referable to nerves of touch, similar to those spread over the 
 rest of the body, and from which we receive sensations of 
 contact, of muscular contraction, heat, cold, local pains, and 
 all their kinds. To begin with smell.* Numbers of what are 
 termed sensations of smell comprise other sensations. And 
 first, sensations of pungent smell are divisible in two parts; 
 they all comprise sensations of touch and, perhaps, are nothing 
 more ; such is the smell of ammonia, which is principally a 
 stinging, as it is transmitted by other nerves than the special 
 ones; the vapor of ammonia produces on the conjunctiva an 
 effect precisely similar to its smell. This stinging may subsist 
 even after the strict sensation of smell has been lost ; some 
 great snuff-takers become insensible to smells, pleasant or 
 otherwise, but continue to take snuff, as they still feel the 
 tingling it produces. Appetizing and nauseating smells are 
 also thus divisible. The strict sensation of smell is here 
 
 * Bain, " Senses and Intellect," 173.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 
 
 combined with another, which, according to the state of the 
 stomach, ceases, is augmented, or reversed ; the same smell, 
 that of a plate of hot meat, is agreeable when we are hungry, 
 and disagreeable when we are suffering from indigestion ; it is 
 probable that, in this case, ceitain deep-seated nerves of the 
 alimentary canal are called into action, and that the whole 
 sensation is made up of a sensation of the olfactory nerves and 
 several accompanying sensations. Finally, we may also divide 
 refreshing and suffocating smells, comprising, on the one hand 
 those of the volatile salts of eau-de-Cologne, of tar, of tan ; 
 and, on the other hand, that of a close room, of a pastry-cook's 
 shop, of a cotton factory, of a cloth warehouse ; here we plain- 
 ly have, in addition to the strict sensation of smell, a sensation 
 of comfort or uneasiness, arising from the air-passages, and 
 conducted by the nerves of touch and pain. I think, too, that 
 in many cases, if, for instance, we inhale alcohol, a feeble sensa- 
 tion of heat comes in to complicate the strict sensation of 
 smell. Pure sensations of smell remain, agreeable or disagree- 
 able in themselves ; those, for instance, of the violet and of 
 assafcetida ; there are an infinite number of them, of which 
 we can only say, that they are agreeable or disagreeable ; in 
 themselves, they resist all analysis, and in order to denote them 
 we have to name the bodies producing them. 
 
 As to taste, what we generally term a flavor, comprises, 
 besides the strict sensation of taste, a number of sensations 
 of other kinds. In the first place, as the back of the mouth 
 and nose communicate, the olfactory nerve is in operation at 
 the same time as the gustatory.* " If you close your eyes 
 and nostrils, and have different kinds of sweetmeats, for in- 
 stance, placed on your tongue, then aromatic creams, of 
 vanilla, of coffee, etc., in every case you will only perceive a 
 sweet, sugared taste, and will not be able to distinguish the 
 different substances employed." In the same way it can be 
 proved that " the urinous taste we attribute to fixed alkaline 
 bases, does not belong to these substances, but to the ammo- 
 nia set free by the reaction of the fixed alkaline bases on the 
 ammoniacal salts contained in the saliva." Here, again, a 
 
 * Longet, " Traite de Physiologic," ii. 171. Bain, " Senses and Intellect," 157.
 
 I2 Q OF SENSATIONS. [BOOK III. 
 
 sensation of smell, or rather of nasal touch, is included in the 
 sensation of taste. Secondly, strict sensations of taste are 
 frequently combined with a different sensation, sometimes 
 agreeable and attractive, sometimes disagreeable and repulsive, 
 belonging to other nerves of the alimentary canal. This ac- 
 companying sensation varies, while the others remain constant ; 
 the same good plate of meat is agreeable or disagreeable, ac- 
 cordingly as the stomach is empty or loaded. Besides this, 
 it arises in other ways ; it has no need, like the other, of 
 chemical action as an excitant ; mere contact is enough ; a 
 finger or a feather in the throat will produce a sensation of 
 disgust. Thirdly,* " Many impressions referred to taste are 
 simply tactile ;" such, for instance, are acrid, irritant, astrin- 
 gent flavors, which are sensations of touch, not of taste. 
 Fourthly, certain flavors are combined with sensations of heat 
 and cold ; the sensation of heat accompanying strong drinks 
 is well known, and also the cool sensation we find as an ele- 
 ment in the flavor of certain sweetmeats. Lastly, different 
 sensations are excited by the same body in different parts of 
 the mouth, and not only different accompanying sensations, 
 but different sensations of pure taste.f " Numbers of bodies, 
 and particularly the salts, exhibit the remarkable peculiarity 
 of exciting, when applied to the back of the tongue, an entire- 
 ly different sensation from what they excite when applied to 
 the anterior part. Thus, the solid acetate of potash, of a 
 burning acidity in the anterior part of the mouth, becomes in- 
 sipid, bitter, and nauseating at the back, and loses entirely its 
 acid pungent taste. Hydrochlorate of potash, simply salt and 
 fresh in the anterior part, becomes sweetish at the back. 
 Nitrate of potash, fresh and pungent in front, is insipid and 
 slightly bitter at the back. Alum is fresh, acid, and astringent 
 when crushed in the front of the mouth, while behind it gives 
 a sweetish taste without the least acidity. Sulphate of soda 
 is distinctly salt in front, and distinctly bitter behind." Ace- 
 tate of lead, fresh, piquant, and astringent in front, becomes 
 
 * Vernier, cited by Longet, " Traite d'Anatomie et de Physiologic du Systeme 
 Nerveux," ii. 170. Bain, ibid. 
 
 f Longet, " Traite de Physiologic," ii. 167. " Experiments of Guyot and 
 Admyrault."
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 12 \ 
 
 sweet at the back. Hence it follows that an ordinary sensa- 
 tion of taste may have several distinct elements in itself, in 
 addition to the four kinds of elements furnished by accom- 
 panying sensations. For, in addition to the non-gustatory 
 nerves, there are different gustatory nerves which intervene 
 to produce it. The mouth, then, is not a simple organ, but 
 a succession of organs, and a taste, even one strictly so called, 
 may be a succession of tastes. 
 
 Let us simplify the matter ; let us lay aside all that part 
 of the sensation which may be referred to touch, such as 
 acidity, astringency, irritation, heat, coolness, the spontaneous 
 muscular sensation radiating towards the alimentary canal, 
 and consider simply the sensations of the gustatory nerves 
 themselves, and put them on the same footing, whether they 
 arise in the anterior part, or at the back of the mouth ; their 
 principal types are the sensations of bitter and sweet, with 
 their innumerable varieties ; when we have thus named them, 
 we are at the end of our knowledge, as happened just now 
 when we called sensations of smell fetid or perfumed. Still, 
 let us see what we can learn in either case by availing our- 
 selves of previous reductions, and by studying the circumstan- 
 ces in which these sensations arise. They have, like the rest, 
 as direct stimulus, an action of the nerve transmitted to the 
 nervous centres. Now it is admitted, in accordance with all 
 known facts, that two different sensations indicate two different 
 states of the nervous centres, and, if the same nerve is con- 
 cerned, two different actions of that nerve. It remains, then, 
 to be known in what way the olfactory or gustatory nerves 
 act ; and, to arrive at this, we must determine the external 
 event in immediate sequence to which its action commences. 
 Nothing is easier than to know the antecedents of this 
 event ; but it is difficult to determine accurately the event it- 
 self. We see, at first sight and by ordinary experience, that 
 such a body excites in us such a sensation of taste or smell, 
 that another excites in us the sensation of red, or blue ; but 
 neither one nor the other excite these sensations otherwise 
 than through media ; the science of optics was required to tell 
 us that undulations of an ether of certain length and speed are 
 the media of action of the second : and it would be necessary
 
 122 OF SENSATIONS. [BOOK III. 
 
 to have recourse to a science already constructed to determine 
 the media of action of the first. Let us inquire, however, 
 into this last immediate event in direct sequence to which the 
 olfactory or gustatory nerves begin to act. A body has no 
 taste unless in solution; the taste is increased when it is 
 moved about and pressed to the gustatory membrane ;* this 
 membrane, again, must not be dry, or rendered insensible by 
 cold. Again, the gustatory nerves are probably protected 
 by a colloid membrane, permeable, as are all such, to non-col- 
 loid substances, but nearly impermeable to colloid substances, 
 which accounts for the taste of non-colloid substances, and the 
 want of taste in colloid ones. All these facts lead us to the 
 conclusion that the dissolved molecules of the body which is 
 tasted penetrate the tissues of the tongue, and come in con- 
 tact with the nervous papillae ; and there, under the influence 
 of the animal heat, form with the liquid secretions a chemi- 
 cal combination varying with the variations of these secre- 
 tions.f Similarly, a body has no smell, except in a gaseous 
 state; and the pituitary membrane must not be dry; it is 
 also proved that, to be odorous, a gas must combine with oxy- 
 gen at the surface of the pituitary membrane. All these 
 facts lead to one and the same conclusion, that the molecules 
 of gas become absorbed in the moisture of the pituitary mem- 
 brane in contact with the olfactory fibres, and there form a 
 chemical combination with the oxygen of the air. Thus the 
 action of the olfactory nerve, like that of the gustatory nerves, 
 appears to have a chemical combination as its immediate ante- 
 cedent. 
 
 Now what is a chemical combination? Chemists reply 
 that a homogeneous body is made up of molecules precisely 
 similar to one another, and extraordinarily small ; that each 
 of them, if the body is not simple, is itself composed of several 
 different atoms much smaller still, and so situated, with re- 
 
 * Bain, "Senses and Intellect," 156, 168. 
 
 * Longet, ii. 164. " The most delicate kinds of food are tasteless, earthy or 
 bitter when the stomach is out of order. . . . The brain and sensorial nerves re- 
 main as they were, but the tongue is covered with a mucous or bilious coating, and 
 every thing produces a dull nauseous impression." Mueller (tr. Baly), ii. 1323. 
 " After chewing the root of the sweet-flag, milk and coffee taste acid to me."
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 12 ^ 
 
 spect to each other, as to remain in equilibrium ; that a chemi- 
 cal combination takes place when a molecule, receiving an 
 atom of another kind, passes into another state of equilibrium; 
 that the atoms then leave their respective positions to take 
 up new ones; that these displacements of atoms, acting at 
 extremely small distances, are themselves extremely small ; 
 that, as these atoms are wonderfully small, we must, to explain 
 their active force, attribute to them, on displacement, veloci- 
 ties of enormous magnitude ; and that, therefore, every dis- 
 tinct chemical combination is made up of a distinct system of 
 prodigiously small and rapid displacements, of which we can- 
 not yet indicate the elements or explain precisely the type.* 
 Here we have the immediate antecedent of the action of each 
 olfactory or gustatory fibre ; and we cannot help observing 
 how closely it resembles the immediate antecedent of the 
 action of the optic nerve, but with this difference, that in the 
 second case the, type and elements of the antecedent are 
 known. In fact, in the vibration of either, the active particles 
 are also of extraordinary minuteness ; their displacements are 
 also wonderfully small and rapid ; they form, also, a number of 
 distinct systems. Only we know that these systems are all 
 made up of waves, and we can measure the speed and length of 
 each wave ; and thus we are able to define exactly the element- 
 ary displacement by whose repetition each system is formed, 
 to show that, in different systems, the elementary displace- 
 ments differ in respect of quantity only, to reduce them all to a 
 single type, to denote the corresponding elementary action of 
 the optic nerve and brain, and to conclude the existence of an 
 elementary optical sensation, by whose prodigiously rapid and 
 multiplied repetitions our total sensations of color are made up. 
 Unfortunately, chemistry is not so far advanced as optics : 
 it can only prove the existence of systems of displacements, 
 while the other science defines and measures them ; it must 
 wait till, like its rival, it can represent these infinitely small 
 events, of which it only knows the final effect. But it is plain 
 
 * " Chemistry has as yet been constructed with reference to masses only ; its 
 construction with reference to velocities remains to be accomplished." Saigey, 
 " De 1'Unite des Forces Physiques," p. 184.
 
 124 OF SENSATIONS. [BOOK III. 
 
 that in the two cases the problem and solution are of similar 
 nature. In each, movements are dealt with, the minuteness, 
 speed, and number of which are wholly disproportioned to the 
 ordinary magnitudes we are capable of estimating in time and 
 space. We may compare, then, the wave of either to a sys- 
 tem of atomic movements, and a succession of similar waves 
 of either to a succession of similar systems of atomic move- 
 ments. Consequently, thanks to the first case, we can, to 
 some extent, represent to ourselves the second. 
 
 A molecule comes in contact with an olfactory fibre or a 
 gustatory papilla ; a system of atomic movements takes place 
 in the molecule, and a corresponding action follows in the 
 fibre ; a second similar molecule arrives at the same point ; a 
 second similar system of atomic movements takes place, and 
 a second exactly similar corresponding action follows in the 
 same fibre. The two similar nervous actions have aroused two 
 similar cerebral actions, and two similar elementary sensa- 
 tions. But the number of such sensations, actions, and systems 
 of movements succeeding in a second is enormous, and the 
 whole sensation of smell or taste, like the whole sensation of 
 color, is but the sum of all the successive elementary sensa- 
 tions, the series of which occupies a certain time.* 
 
 We can now form an idea of. the four special senses. The 
 distinctive character of their sensations is that each, even the 
 simplest, of those we are conscious of, is made up of a succes- 
 sion of very numerous elementary sensations of extremely 
 small duration, whose rhythm corresponds to the special 
 rhythm of an external event, to an undulation of air or ether, 
 to a system of atomic movements, forming the external nat- 
 ural antecedent with regard to which the sense was construct- 
 ed, and by the presence of which it ordinarily acts. What 
 
 * Certain points of agreement show us the connection of our sensations of 
 smell and taste with the atomic constitution, and therefore with the change of 
 atomic constitution of the molecules (Bain, 152, 165). Three atoms of oxygen with 
 two atoms of a metal form a compound of sweet or sugary taste. All organic al- 
 alkies are very bitter. Almost all acids have an acid taste. Almost all salts of iron 
 have an inky taste, etc. Substances with a perfumed smell are carburets of hy- 
 drogen. Substances of fetid smell have, nearly all of them, arsenic or sulphur in 
 their bases, etc.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. I2 e 
 
 constitutes a special nerve is its capacity to arouse such ele- 
 mentary sensations. Those excited by the acoustic nerve 
 correspond to undulations of the air comprised between two 
 limits. Those of the optic nerve correspond to undulations 
 of ether also comprised between two limits. Those to which 
 the gustatory and olfactory nerves give rise, correspond to 
 molecular movements of determinate form. 
 
 Compare, for instance, the two sensations which the same 
 undulations of the air excite through the nerves of touch, and 
 the nerves of hearing ; that is to say, on the one hand a more 
 or less pronounced quivering and tickling, and on the other 
 hand a sound more or less intense and acute. The external 
 antecedent is the same in the two cases ; but the elementary 
 sensations excited through the medium of the acoustic nerve 
 correspond to the elements of the undulation of the air, and 
 this is not the case with the elementary sensations excited by 
 the medium of the nerves of touch. For, in fact, all details 
 and variations of the undulation of the air are represented in 
 the whole sensation of hearing, and are not represented in the 
 whole sensation of touch. In the sensation of hearing, the 
 greater or less speed of the waves is represented by the great- 
 er or less acuteness of the sound ; the tone, by a supplemen- 
 tary group of more feeble sensations ; each wave, by an ele- 
 mentary sensation ; the depth of the wave, by the intensity 
 of the sound ; the degrees of condensation of each wave, by 
 the degrees of intensity of the sound. With the sensation 
 of touch, on the contrary, the representation is imperfect ; all 
 we experience is that the quivering becomes stronger, and de- 
 generates into a tickling, when the undulation becomes quick- 
 er and the condensations of the waves become stronger. And 
 so again another external event, the undulation of an ether, 
 represents itself to us in two ways, by the tactile sensation 
 of heat or cold, and the visual sensation of color and light. In 
 the second case, all the degrees of speed and length which the 
 wave of ether assumes are precisely represented, but only 
 when their speed and length attain that of the limit of red, 
 and do not exceed that of the limit of violet. On the contra- 
 ry, the first translation represents, not only waves comprised 
 between the limits of red and violet, but many other waves
 
 126 OF SENSATIONS. [BooK III. 
 
 situated outside those limits ; but none of the waves are spe- 
 cially represented, and the sensation of heat or cold does but 
 roughly represent the difference of intensity separating two 
 systems of successive undulations. 
 
 Thus the four special senses are four special languages, 
 each appropriate to a different subject, each admirably adapt- 
 ed to express one order of facts, and that order alone. Touch, 
 on the other hand, is a general language applicable to all sub- 
 jects, but not well fitted to express the shades of meaning in 
 the different subjects. In general, a sense is a system of spon- 
 taneous writing and of automatic notation, resembling the in- 
 struments of measurement of which we avail ourselves in phys- 
 ics and chemistry. Sometimes these are delicate and special, as 
 the multiplying calorimeter, or the instrument invented for 
 the self-registration of the movements of the heart ; sometimes 
 they are less delicate and of general use, as the balance which 
 only serves to denote the final augmentation or diminution of 
 weight in an experiment. Sometimes the elementary sensa- 
 tion corresponds, feature for feature, with the element by 
 whose repetition the external event is made up ; in this case 
 the elementary sensation copies, one by one, the variations 
 of this element, with their order and magnitude ; but, if we ap- 
 ply it to elements of another kind, it is of no effect, or con- 
 fused, or extreme, and unfit to represent them. Sometimes 
 the elementary sensation does not thus correspond, feature 
 for feature, to the element whose repetition constitutes the 
 external event, and does not copy the several variations of 
 this element ; but, in this case, the external event, whatever 
 it be, excites a body of elementary sensations, the whole of 
 which represent it as a whole, though unprecisely and in the 
 rough. 
 
 IV. This is the character of touch, and we see that it 
 differs from the other senses, and that its elementary sensations 
 do not correspond to any elementary external event, and so 
 cannot be referred to any known type. Here, then, we are 
 confronted with a new difficulty. There is no special event here, 
 as in former instances, to serve as a guide in discovering ele- 
 mentary sensations. We have to seek out a new path ; be- 
 fore attempting it, let us see whether among the sensations of
 
 CHAP. II.] SENSATIOA T S OF SIGHT, ETC. 
 
 127 
 
 touch we cannot find some to which others may be reduced ; 
 we must clear the ground before attempting to cultivate it. 
 
 In studying cases of partial paralysis, physiologists have 
 first distinguished two groups of primitive sensations, one com- 
 prising sensations of the muscles, and the other sensations of 
 the skin, the first having as origin the excitement of the nerv- 
 ous extremities found in the muscles, the second having as or- 
 igin the excitement of the nervous papillae found in the derma. 
 Each of these two groups may be missing, without the other 
 being affected. 
 
 When the first is wanting, we see that all the sensations 
 of muscular contraction and expansion are absent, with all their 
 several degrees of painful effort, fatigue, and cramp, besides 
 the various sensations of cold, heat, contact, pain, electric shock, 
 produced by the application of stimuli to the muscles in their 
 normal state.* " As soon as the patients take their eyes off 
 their limbs, they have no more consciousness of their position, 
 or even of their existence. When in bed, they lose them, as 
 it were, and are obliged to look for them, not knowing where 
 they are. Sometimes they try to stretch out or bend some 
 limb already stretched out or bent. On moving, they are 
 ignorant of the extent of their movement, and frequently do 
 not know whether they have moved or not. If they intend 
 to move, but are prevented, they are unaware of it, and think 
 they have moved, from having willed to do so. Passive move- 
 ments may be occasioned in them by means of an electric ap- 
 paratus, without their suspecting it. Their limbs seem to 
 them deprived of weight. If their hands are plunged in water, 
 they know by the cutaneous impression that it is a liquid, but 
 on moving the hand about, they do not experience that soft 
 resistance which gives the notion of the fluidity of water, and 
 do not know whether their hand is moving in the air or in the 
 water. If the muscles be pressed, pinched, or kneaded, no 
 distinct sensation takes place. They do not perceive the pas- 
 sage of an intense electric shock. A sharp instrument may 
 be stuck in their flesh without their perceiving it ; that is, un- 
 less they discover it through the persisting sensibility of the 
 
 * Axenfeld, " Des Nevroses," 339.
 
 128 OF SENSATIONS. [BOOK III. 
 
 skin." Therefore, though they have retained all their muscu- 
 lar vigor, and are besides insensible to fatigue, they walk with 
 great difficulty in the dark, or when they cease to watch their 
 movements with their eyes ; the sensations of sight must be 
 constantly present to supply the place of the absent muscular 
 sensations. If both sensations fail them, " they can hardly 
 keep themselves upright without stumbling or running the 
 risk of a fall ; their movements are either too extensive or 
 not extensive enough ; they readily let things slip from be- 
 tween their fingers, or sometimes crush them by too forcible 
 a contraction." No other sensation is missing ; they may still 
 feel all the cutaneous sensations of tickling, contact, passive 
 pressure, of superficial heat and pain. In other words, such 
 patients can no longer estimate the state of their muscles, but 
 are still perfectly capable of estimating the state of their skin. 
 
 There are patients, on the other hand, unable to estimate 
 the state of their skin, but who can still estimate the state of 
 their muscles.* A workman, mentioned by Landry, had his 
 fingers and hands insensible to all impressions of contact, 
 pain, and heat ; but his muscular sensations were unaffected. 
 If his eyes were closed, and a somewhat bulky object were 
 placed in his hand, he was surprised at not being able to close 
 it; he had a sensation of resistance, but nothing more; he 
 could not say what the object was, what was its form, size, 
 kind, if it was cold or hot, rough or smooth, or even if there 
 was any object there at all. A weight of a kilogramme was 
 tied to his fist with a string without telling him what it was, 
 and he thought some one was pulling his arm. 
 
 Here, then, we have two groups of sensations and two 
 groups of nerves as distinct as those of the arm and leg,f and, 
 
 * Landry, " Traite des Paralysies," i. 195, 182, 199. 
 
 f Brown-Sequard, "Journal de Physiologic," vi. pp. 124-615. According to 
 Brown-Sequard, " sensitive impressions of pain and touch are transmitted in a 
 cross direction to the spinal marrow, that is to say, the transmission to the brain 
 of impressions arising in one half the body acts in the lateral half of the spinal 
 marrow on the opposite side. On the contrary, impressions of muscular sensation 
 pass without crossing to the anterior part of the spinal marrow." Consequently 
 " the conductors of muscular sensation differ fundamentally from the conductors of 
 other sensitive impressions." And the author adds, " not only do these conductors
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 
 
 129 
 
 we may. add, as similar. For the nerves of the muscles, like 
 those of the skin, may give rise to sensations of contact, of 
 cold and heat, of pleasure and pain.* " Persons wounded by 
 a sword-thrust, or the cut of a bistoury, frequently feel, in 
 addition to the pain of the wound, the chill of the blade and 
 its presence in the depth of the tissues, and, with many para- 
 lytics, although the skin may be quite insensible to all kinds of 
 stimulation, a pressure, a shock, the pick of a pin-thrust into 
 the soft parts, are felt as deep-seated impressions of contact, 
 shock, and pain." Besides, these same nerves give us pain 
 when electricity is passed through them, or when they are 
 excited by a very strong muscular contraction ; and when ex- 
 cited by the expansion consequent on fatigue and shampoo- 
 ing they give pleasure. In all these respects, their action is 
 the same as that of the nerves of the skin, from which they 
 only differ by terminating in the muscles, and being excited 
 by the stretching out or shortening of the muscles. But here, 
 there is no difference of action, the difference is the excitant ; 
 in the strict muscular sensation there is nothing more than a 
 sort of wrenching, similar to the other sensations, and capable, 
 like them, of passing into pain if pushed too far. 
 
 Thus we arrive at distinguishing in the nerves of the 
 muscles, as in those of the skin, three, and only three kinds of 
 sensations: those of contact, those of heat and cold, those 
 of pleasure and pain. And further, we find all three kinds 
 more or less vaguely present wherever there are tactile nerves. 
 
 not cross in their passage to the spinal marrow, but further, they spring from this 
 organ principally if not entirely by the anterior spinal roots." 
 
 There are very strong proofs of this theory in observations made in cases of 
 wounds and lateral alterations of the spinal marrow. We see patients lose on 
 one side, the right for instance, the power of experiencing sensations of touch, of 
 pain, of cold, of heat, of tickling, and preserve on this same side, not only the 
 power of moving their limbs, but also that of directing them exactly, and esti- 
 mating all the degrees of muscular contraction ; the inverse is the case on the left 
 side. (See particularly the cases cited, pp. 238, 582). In accordance with this 
 theory, the nerves and conductors of muscular sensations are not only distinct 
 from the nerves and conductors of tactile sensations, but, more than this, their 
 anatomical course is different, and we can discover this course in the spinal mar- 
 row. 
 
 * Landry, " Traite des Paralysies," i. 201.
 
 OF SENSATIONS. [BOOK III 
 
 " The internal surface of the walls of the abdomen feels 
 clearly the motion of the intestines After a cold in- 
 jection, a very plain sensation of cold is felt passing in the direc- 
 tion of the ascending and transverse colon."* The pharynx, 
 oesophagus, and even the stomach, feel with some degree of 
 exactitude the passage, warmth, and presence of food. And, 
 in general, let us review successively the innumerable internal 
 sensations, agreeable, painful, or indifferent, of organic life, 
 those constituting hunger, thirst, and repletion, those accom- 
 panying digestion, respiration, circulation, copulation, or 
 speech, those produced by wine, medicines, and various sub- 
 stances introduced into the circulation, besides all the spon- 
 taneous sensations, tinglings, itchings, shiverings, all the vari- 
 ous hardly definable pains which serve as symptoms of differ- 
 ent illnesses, all the special and very delicate sensations of 
 touch we meet with in the conjunctiva, the tongue, and the 
 interior of the nostrils, all the general and blunted sensations 
 of touch such as we find on the surface of the wound after a 
 recent amputation : we shall see that they are sensations of 
 contact, of cold or heat, of pleasure or pain, more or less ob- 
 scure, more or less ill-defined, more or less spread about, the 
 same in substance, but diversified by their situation, the order 
 of their phases, and the degree of their intensity.f We shall 
 
 * Landry, " Traite des Paralysies, " i. 201. Longet, " Traite de Physiologic," 
 ii. 179- 
 
 f Numbers of sensations which seem to have a special type and to be sui gene- 
 ris, are composed of elementary sensations of contact. " If," says M. Landry, 
 " we cover a polished surface with a thin layer of talc and get a person who is not 
 aware of this to pass the tip of his finger over it, he will imagine he is touching a 
 greasy or oily body. . . ." Again, if we sprinkle some drops of water on a marble 
 table, and then, with our eyes shut, place the tip of a finger alternately on the dry 
 and the wet spots, we shall not be able to distinguish one from the other. There 
 is no special sensation, then, of damp or stickiness, but a compound sensation of 
 touch. " This sensation," says M. Gratiolet, " is developed when the skin detaches 
 itself from something sticking to it, as, for example, a surface covered with diachy- 
 lon. It is most clear and distinct at the moment the adhesion comes to an end, 
 and the skin which had been drawn by the surface suddenly returns to its proper 
 state. From this sensation, when it is strong, comes the idea of viscidity ; when 
 slight, that of humidity. The contrary notion of dryness is derived from an abso- 
 lute want of adherence. This is so far the case that when the hand is plunged in 
 water we do not feel this humidity, nor when it is plunged in oil do we feel its oili- 
 ness. In fact, bodies which an intermediate layer of water cause to adhere to vis,
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. J ^ l 
 
 find no other element in them, and, by this first reduction, 
 we bring tactile sensations under three types, and three only. 
 These types are not only distinct, but separable ; each of 
 them, as far at least as sensations of the skin are concerned, 
 may severally be lost, while the other two are retained.* 
 In some cases the sensation of pain only is lost. Patients still 
 perceive the other cutaneous sensations, such as heat, contact, 
 tickling, and can recognize the touch of a finger, the brushing 
 of a quill, the contact of a pin ; but if, in the same spot, we prick 
 them with the pin, it occasions no pain. "I can feel," said 
 one of them, " that you prick and pinch me, but you do not 
 hurt me." This is carried so far that sometimes the applica- 
 tion of a white-hot cauterizing iron gives no pain. A girl, 
 suffering from hysteria, at the Hopital Saint-Antoine, upset 
 boiling water over her hands, and did not find it out till she 
 saw large blisters rising. In other cases, sensations of heat 
 and cold are alone wanting. The patient then says : " I feel 
 the form and consistency of the body touching me, but cannot 
 tell whether it is hot or cold." Finally, in other cases, the 
 sensation of touch only is wanting. Here, for instance, the 
 patient does not feel small objects placed between the tips of 
 his fingers ; but" if pricked there, even superficially, it is plain- 
 ly felt." On the other hand, each type of sensation may sub- 
 sist alone, the other two being lost. Some patients who no 
 longer feel sensations of pain or heat, still feel contact at the 
 same point. Others more numerous, no longer feel sensations 
 of pain and contact, but those of temperature only. Others 
 finally, who can still feel pain, cannot feel heat or contact. 
 It is plain that each of these three types of sensation has its 
 
 no longer adhere when plunged in water, and so with bodies plunged in oil. . . . 
 The skin i > i apable of receiving impressions on two layers the one superficial, 
 the other deep-seated. When the sensibility of the deep-seated layer is brought 
 into play, the sensation of pressure arises." Gratiolet, " Anatomic Comparee du 
 Systeme Nerveux," ii. 409. Landry, " Paralysies," 159, 179. 
 
 * Beau, "Archives Generates de Medecine," Janvier, 1848. Delacour, these, 
 Janvier, 1850. Landry, " Recherches sur les Sensations Tactiles." " Traite des 
 Paralysies." Axenfeld, " Des Nevroses," 332. 
 
 This separation has not been observed in the muscular sensations ; when any 
 of them disappear, the others disappear as well.
 
 !32 OF SENSATIONS. [BOOK III. 
 
 special conditions, and when these conditions alone are abol- 
 ished, or alone preserved, the isolated abolition or preservation 
 of the type ensues. Experience has discovered some among 
 these conditions. If a limb is chilled up to a certain fixed 
 point, it retains the sensation of contact, but ceases to expe- 
 rience that of pain ; for instance, " if we apply to the knee 
 a mixture of pounded ice and sea-salt in the proportion of 
 two parts of ice to one of salt, the skin becomes bloodless, and 
 we may cauterize the limb without the patient feeling any 
 other sensation than that of the pressure of the iron." Thus, 
 the sensation of pain is subject to a special condition ; to 
 produce it, the circulation of the blood, and therefore the mo- 
 lecular wastings and repairs of the nerve, must go on with a 
 certain degree of speed. With a less degree the nerve is no 
 longer capable of the special type of action which arouses the 
 sensation of pain, though it may still be capable of the special 
 type of action which arouses the sensation of pressure and of 
 contact. We see that the sensation of pain requires for its 
 production a condition, additional to those required by the 
 sensation of contact ; hence it follows that it may readily be 
 abolished without inducing the abolition of the sensation of 
 contact, and that the reverse is not the case ; this is in con- 
 formity with experience. Persons who have lost all sensations 
 of pain frequently retain sensations of contact ; but very sel- 
 dom do persons who have lost sensations of contact retain 
 those of pain.* 
 
 This instance puts us in the track of the needed expla- 
 nation. In fact, we have no need to suppose, with many 
 physiologists, that there are three kinds of nerves intended 
 to transmit impressions of contact, of heat and cold, and of 
 pain respectively ; each of the three classes being capable of 
 being paralyzed singly, and of thus cutting away from us one 
 kind of sensation without the other kinds being thereby abol- 
 ished. The only thing which the facts attest is, that the three 
 kinds of sensations have special conditions, and that these con- 
 
 * Axenfeld, ibid., 332. " The inverse case is rarely seen ; when the sense of 
 touch is lost, that of pain is lost at the same time, or, in other words, the existence 
 of anaesthesia, strictly so called, almost invariably implies that of analgesia."
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 
 
 133 
 
 ditions may be singly destroyed. What are these conditions ? 
 We may conceive many kinds. They may be anatomical ; this 
 is the answer of the physiologists, of Landry, Brown-Sequard, 
 and Lhuys. In fact, it is sufficient for the explanation of 
 these isolated abolitions that there be three kinds of nerves ; this 
 solution is a manifest one, we are tempted to adopt it. But 
 there are others, for the presence of a special nerve does not 
 necessarily follow from the fact of a special condition. There 
 are two other possible explanations. First, the condition may 
 be a special state of the same nerve, which would appear to be 
 the case from the experiment in which the frozen knee becomes 
 bloodless. Secondly, the condition may be a special state of 
 the parts surrounding the nerve, and through which the ex- 
 ternal stimulus acts on the nerve ; in this case, the same nerve, 
 under the influence of the same external stimulus, would trans- 
 mit different sensations, according as the parts between it and 
 the stimulus were in different states. These last solutions are 
 more abstract, but they agree better with the facts. 
 
 Weber's experiments appear to me conclusive as to this.* 
 If we dip into cold water a large nervous trunk, for instance, 
 the cubital nerve, where it springs from between the two bones 
 at the elbow, we find, in accordance with a well-known law, a 
 sensation in the arm and two last fingers of the hand, occa- 
 sioned by the nervous action going on at the elbow ; now this 
 sensation is not of cold, but simply of pain. Consequently, 
 when we have a sensation of cold, it is not owing to the im- 
 mediate action of cold on the nerve ; for it was not felt just 
 now, when the cold was acting immediately on the cubital 
 nerve. In order to feel it, the cold must act indirectly; that 
 is to say, through certain parts adjacent to the nerve, certain 
 
 * Article Tastsinn, 498, in " Handbuch der Physiologic," by Rudolf Wagner. 
 
 Cf. Fick, " Anatomie und Physiologic der Sinnes Organe," 28, 30, 42, 43. 
 From the anatomical structure of the organs of touch, he shows, by approximation 
 and hypothesis, the different types of action which excite in the same nerve dif- 
 ferent sensations, that of heat or cold, that of pressure or contact. " It is probable 
 that the stimulation of the nerves, in the sensation of heat or cold at the sensible 
 periphery of the skin, is not immediately developed by a change of temperature 
 of the nervous substance itself, but by the simultaneous changes supervening in the 
 mechanical relations of the terminal corpuscles."
 
 1 34 OF SENSA TIONS. [BooK III. 
 
 organs disposed for this purpose ; these act directly on the 
 nerve ; the cold modifies them, and their modification impress- 
 es on the nerve a special type of action, which excites in us 
 the special sensation of cold. If, on the contrary, without 
 paralyzing the nerve, we simply destroy in these adjacent 
 parts the property they have of impressing this rhythm of ac- 
 tion on the nerve, we shall cease to have the special sensation 
 of cold ; when the cold begins to act on the nerve, it will no 
 longer excite the special sensation of cold, and will only ex- 
 cite, as we found just now in the case of the cubital nerve, 
 the sensation of pain. This is what happens in certain illness- 
 es. M. Axenfeld writes as to this " With ataxic persons, 
 whose cases are among those in which want of sensibility is 
 most complete, I have often observed that cold was disagree- 
 able without its being recognized as cold. When we ques- 
 tion them as to the nature of their perception, all we can get 
 from them is, ' It hurts me.' " We are led to the same con- 
 clusion by studying the sensations of persons whose bodies 
 present large cicatrices, consequent on amputations or other 
 wounds. " The parts of the skin," says Weber, " in which 
 the tactile organs have been destroyed, and are not complete- 
 ly reproduced, cannot distinguish heat and cold." Similar 
 experiments point out the presence of similar media in the 
 case of the sensation of. pressure. If the cubital nerve be- 
 tween the two bones of the elbow be pressed with the finger, 
 the sensation in the fingers and forearm is not of pressure, 
 but solely of dull pain. " Therefore," says Weber, " the sen- 
 sation of pressure, and the power of distinguishing its numer- 
 ous and different degrees, are only possible when the pressure 
 acts on the organs of touch, and, through them, on the extrem- 
 ities of the tactile nerves ; this sensation does not arise when 
 the tactile nerves are directly compressed." Consequently, 
 the sensation of pressure has for its special condition, not the 
 pressure of the nerve, but a certain modification of certain 
 organs or parts surrounding the nerve. If these organs be 
 alone destroyed, or their capacity for undergoing this modifi- 
 cation he alone suppressed, the sensation of pressure will alone 
 be abolished. 
 
 Thus, in all cases, what is excited in us is a special type
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. iy 
 
 of action in the nerve, and what excites this special type of 
 action in the nerve is a special modification of its appendages 
 and dependent parts. Consequently, to explain the three 
 kinds of tactile sensations, and to comprehend how they may 
 be singly abolished, there is no necessity of supposing them f 
 excited in us by distinct nerves of three different kinds : this 
 is a gratuitous hypothesis which no vivisection or microscopic 
 observation comes in to confirm. It is enough to admit that 
 the same nerve or group of nerves is capable of many differ- 
 ent types or rhythms of action, and that each of these rhythms 
 is directly excited by the special modification which the ex- 
 ternal agents impress on the parts surrounding the nerve, 
 whether on the tubes containing it, or on the blood washing 
 it, or on some other of its internal accompaniments. 
 
 It is not impossible to form a notion of the differences of 
 these rhythms. " Each tactile nervous fibre," says Fick, " can 
 only transmit one and the same sensation which is capable 
 
 only of degrees But ordinary external stimuli do not 
 
 arrive at these isolated elementary fibres ; they come in con- 
 tact with a group of fibres taken together. We may suppose 
 that heat reaches these fibres in a different order from pres- 
 sure." " In fact, the nearer we draw to the true elementary 
 sensation, the more does the difference between the sensation 
 of heat and that of a mechanical stimulus seem to vanish. 
 For instance, we can hardly distinguish a prick with a very 
 fine needle from the touch of a spark of fire." There is a 
 further analogy ; we know that the sensations of heat and 
 cold, like those of pressure, become, when carried beyond a 
 certain point, pure pain. " Lastly, place on the skin some 
 imperfectly conducting body ; for instance, a piece of paper, 
 pierced with a hole of from 2 to 5 millimetres in diameter ; 
 through this hole apply to the skin, first, a mechanical stimu- 
 lus, a pointed piece of wood, a pencil or a flock of wool ; then, 
 a heated stimulus, such as the radiation from a piece of hot 
 metal." The two sensations, when thus limited to a minimum 
 of nervous elements, are so similar that the subject of the ex- 
 periment frequently mistakes the sensation of heat for one of 
 contact, and that of contact for one of heat, On the contrary, 
 when the nervous elements are numerous, as when a large
 
 OF SENSATIONS. [BOOK III. 
 
 surface of the skin is subjected to the same experiments, there 
 is not this confusion. Plainly, then, here as before, the ordi- 
 nary sensation is a whole ; and, here as before, two whole sen- 
 sations may be apparently irreducible to one another, though 
 their elements may be the same ; for this it is enough if the 
 little composing sensations differ in number, magnitude, order 
 and duration ; their wholes form masses indivisible by con- 
 sciousness, and seem simple facts, differing in essence and op- 
 posed in quality. 
 
 It is very probable that the sensation of pain is no more 
 than a maximum ; for all the others, pressure, tickling, cold, 
 heat, change into pain when carried beyond a certain limit. 
 It is very probable that the sensation of pressure only differs 
 from contact because in pressure " the terminal corpuscles of 
 the deep-seated system are also engaged, while in contact they 
 are not so." 41 The sensation of tickling is most probably 
 nothing more than a high degree of the sensation of touch ; 
 for, writes M. Axenfeld, " I have always found it disappear 
 with the sensation of touch." And, in fact, the contact pro- 
 ducing it, though apparently feeble, is actually excessive ; the 
 feather of the quill, or the piece of string which, when drawn 
 slowly along the cheek or across the nose, grazes imperceptibly 
 the extremity of a nervous papilla, evidently excites consid- 
 erable activity in the terminal molecule of the papilla, for the 
 sensation is a most vivid one and lasts for some seconds after 
 the touch. The alteration of equilibrium in the nerve indica- 
 ted by it is greater and slower in disappearing than when a 
 pressure drives back uniformly a whole group of papillae; if 
 the whole displacement of flesh is then much greater, the 
 relative displacement of the nervous molecules is much less. 
 This is why the final sensation, if of less extent, is far more 
 vivid. 
 
 To sum up ; all that observation shows us in the nerves 
 of touch, are different systems of transmissible molecular dis- 
 
 * See Fick and Gratiolet at the places mentioned. Cicatrices have no sensa- 
 tion of heat, and only a dull sensation of pain, but they retain the sensation of 
 pressure. This arises from the terminal epithelial corpuscles being lost, while the 
 deep-seated corpuscles of Pacini are still there.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. i^j 
 
 placements. Composed of similar elements, they constitute 
 dissimilar types or rhythms ; undefinable by us in the present 
 state of science, they are, like all displacements, definable in 
 themselves, by the speed, magnitude, and order of their ele- 
 ments; and we may admit that, according to the order of 
 their elements, they arouse in us sensations, sometimes of 
 temperature, sometimes of contact or pressure ; that at their 
 minimum of speed and magnitude, they arouse feeble sensa- 
 tions of pressure, contact, and temperature ; at their maxi- 
 mum of speed and magnitude, they excite in us the sensation 
 of pain. 
 
 V. Let us attempt to cast a general glance over all these 
 facts. A sensation of which we are conscious is a compound 
 of more simple sensations, which are themselves composed of 
 others still simpler, and so on. Thus the sensation produced 
 by a harmony of thirds, ut mi, is made up of two simultaneous 
 sensations of sound, ut and mi. Again, the sensation of ut, 
 like that of mi, is made up of a comparatively strong sensation, 
 that of ut, with the addition of other comparatively feeble 
 simultaneous sensations, those of the superior harmonics. As 
 to this comparatively strong sensation and these compara- 
 tively weak ones, each is made up of shorter successive sensa- 
 tions, which, when isolated, are still perceptible by conscious- 
 ness, and whose number is equal to that of the vibrations of 
 the air divided by two. Each of these little sensations is, in 
 its turn, composed of two successive elementary sensations, 
 which, taken si igly, are not perceptible to consciousness. Fi- 
 nally, each of these elementary sensations is itself an infinite 
 series of successive sensations, equally imperceptible to con- 
 sciousness, infinitely short, and increasing from a minimum to 
 a maximum through an infinite number of intermediate stages. 
 The whole results in the sensation of the chord ut mi, a com- 
 pound of the fifth degree, just as a nroduct in organic chem- 
 istry. So, again, the sensation of white is composed in the 
 first place of as many partial and simultaneous sensations of 
 white as there are nervous fibres excited in the retina. Sec- 
 ondly, every partial sensation of white is constituted by simul- 
 taneous sensations of two, or more than two, complementary 
 colors, for instance, yellow and indigo. Thirdly, the sensation
 
 I3 8 OF SENSATIONS. [BOOK III. 
 
 of yellow, like that of indigo, is made up of three element- 
 ary and simultaneous sensations of color, red, violet, and green, 
 each having a particular degree of intensity. Fourthly, each 
 of these three elementary sensations is composed of successive 
 and continuous sensations of the same color, sensations still 
 perceptible to consciousness, and so numerous that there are 
 at least a million of them in a second. Fifthly, each of these 
 successive sensations, so prodigiously short, is, according to 
 all analogies, composed like those of sound, of still shorter 
 successive sensations, imperceptible to consciousness, like the 
 primitive sensations of sound. Finally, if we follow out our 
 analogies to the end, we are led to conceive the sensation ex- 
 cited by each elementary wave of ether on the model of the 
 sensation excited by each elementary wave of air, that is to 
 say, as an infinite series of successive sensations infinitely short 
 and increasing from a minimum to a maximum through an 
 infinite number of degrees. Such is the sensation of white, 
 a compound of the fifth or sixth degree. 
 
 This analysis brings three important principles to light. 
 The first is that two successive sensations which, singly, 
 are insensible to consciouness, may, when combined, form 
 a total sensation which consciousness perceives. The second is 
 that a sensation indecomposable by consciousness, and appar- 
 ently simple, is a compound of successive simultaneous sen- 
 sations which are themselves highly complex. The third is 
 that two sensations of the same kind and differing only in the 
 magnitude, order, and number of their elements, appear to 
 consciousness as irreducible to one another, and as possessed 
 of special qualities absolutely different. Armed with these 
 three principles, we can conceive the nature and diversity of 
 the sensations of the other senses. In accordance with the 
 second and third, smells, which like the color white, appear 
 simple sensations, are, like white, compound sensations, and 
 the different smells, which like different tones, seem irreducible 
 to one another, are, like these different tones, wholes, which, 
 composed of the same elements, differ only in the magnitude, 
 order, and number of these elements. We may form the 
 same conclusion with respect to tastes, and the sensations of 
 touch. But here a difference appears. With smells and
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. 
 
 tastes an advance may be made which cannot be made with 
 sensations of touch. An idea may be formed of the elemen- 
 tary sensations of which sensations of smell and taste are con- 
 stituted, but not of those of which tactile sensations are con- 
 stituted. We prove that the special and immediate antece- 
 dent which sets the olfactory nerves and gustatory nerves in 
 action is a system of molecular displacements ; we conceive 
 his system of displacements to be represented in the nerves 
 by a corresponding system of nervous actions, and to repre- 
 sent itself to us by a corresponding system of elementary sen- 
 sations of taste and smell; we define, to a certain exteat, 
 these unknown elementary sensations by saying that they 
 correspond to molecular movements of chemical action, as the 
 known elementary sensations of hearing or sight correspond 
 to waves of the undulations of air or ether. There is nothing 
 similar in the case of touch ; we have no means of determining 
 or conjecturing the rhythm of action impressed on the tactile 
 nerves and transmitted by them to the nervous centres. The 
 elementary nervous action, and consequently the elementary 
 tactile sensation, remain beyond our grasp. All we know is 
 that there is such an action, and therefore such a sensation ; 
 for whatever be the stimulus, the tactile nerve and the cen- 
 tres it is connected with always act alike and in a way peculiar 
 to them : their rhythm of action is special and unalterable ; 
 this is proved by the rhythm invariably exciting in us the 
 same kind of sensation, and from this kind of sensation being 
 excited by it alone. 
 
 Here are great gaps ; they will only be filled when phys- 
 iology is sufficiently advanced to determine the form and speed 
 of the molecular movement, whose repetition constitutes ner- 
 vous acting. Meanwhile the theory of sensation is like a build- 
 ing in part completed, and in part planned out. Still this 
 incomplete construction is sufficient to give us an idea of the 
 whole. We see that the innumerable sensations which we 
 refer to one sense may be reduced in each case to an elemen- 
 tary sensation whose different groupings make up the different 
 sensations of that sense. We conceive, in accordance with 
 the three principles laid down, that the elementary sensations 
 of the five senses may themselves be wholes, composed of the
 
 140 OF SENSATIONS. [BOOK III. 
 
 same elements, without other difference than that of the num- 
 ber, order, and magnitude of these elements, and therefore, like 
 the distinct sensations of hearing or sight, they may be reduced 
 to a single type. If so, there would be but one elementary 
 sensation capable of various rhythms, as there is but one ner- 
 vous texture capable of various types.* And in fact, what- 
 ever may be the structure of the nerves and nervous centres 
 whose action excites a sensation, however various this struc- 
 ture may be supposed, that which is transmitted from one end of 
 the nerve to the other up to the ultimate nervous centre, is 
 n,ever more than a molecular displacement, more or less rapid, 
 extensive, and complex. A particle had a certain situation 
 with respect to others ; this situation changes, that is all ; at 
 the limit of all the sciences relating to bodies we invariably 
 find mechanics. So that the different nervous actions which 
 excite different sensations, can only be conceived as sys- 
 tems of movements. Thus all these actions, though dif- 
 fering in quantity, are the same in quality. Now since, by 
 the known correspondence between the sensation and the 
 nervous action, sensations different in quantity are the same 
 in quality, we arrive, by deduction, at the result foreshad- 
 owed by analogy. At the foundation of all bodily events 
 we find an infinitesimal event, imperceptible to the senses, 
 movement, whose degrees and complications constitute the 
 rest, whether the phenomena be physical, chemical, or phys- 
 iological. At the foundation of all moral events, we guess 
 the presence of on infinitesimal event, imperceptible to con- 
 ciousness, whose degrees and complications make up all 
 
 * Fick, " Lehrbuch der Anatomic und Physiologic der Sinnesorgane," 5. Der 
 Erregungsvorgang, welche Form er auch immer haben mag, ist in alien nervo'sen 
 Elementen gleicher Art, also ins besondere, in alien Nervenfasern, derselbe, sei 
 dieser Faser im Hirn, im Ruckenmark, oder in einem peripherischen Nervenstamm. 
 . . . Indessen ist doch sehr \varhscheinlich, dass der Erregungsvorgang in den 
 nervo'sen Elementen in gewissen Drehungen oder Umgruppirungen electromoto- 
 rischen molecule besteht. 
 
 See also Dr. Onimus, " De la Vibration Nerveuse et de 1'action reflexe dans 
 les Phfinomenes Intellectuels." 
 
 Many physiologists admit that this displacement of the nervous molecules may 
 be compared to a vibration or to the swing of a pendulum. At all events, there 
 is an order of positions, which is altered, and then re-established.
 
 CHAP. II.] SENSATIONS OF SIGHT, ETC. I4 ! 
 
 the rest, sensations, images, and ideas. What is this sec- 
 ond event, and can we reduce one of these events to the 
 other? 
 
 Meanwhile we have reached the foundations of human 
 knowledge, and are capable of estimating their solidity. We 
 have seen that our senses are idioms, of which four are special 
 and the last general. A sensation is a mental representative, 
 the internal sign of the external fact exciting it. The 
 special sensations of sight, hearing, smell, and taste are deli- 
 cate and limited representatives, each of which severally trans- 
 lates accurately, by its characteristics, a special order of ex- 
 ternal facts. The general sensations of touch are coarse uni- 
 versal representatives translating, by their characteristics, 
 nearly all the orders of external facts. Thus, every normal 
 sensation corresponds to some external fact which it trans- 
 cribes with greater or less approximation, and whose internal 
 substitute it is. By this correspondence, internal events agree 
 with external, and sensations, which are the elements of our 
 ideas, find themselves naturally and beforehand adjusted to 
 things, which adjustment will, further on, enable our ideas to 
 be in conformity with things, and consequently true. On the 
 other hand, we have seen that images are substitutes for sen- 
 sations, past, future, or possible, that individual names are 
 substitutes for images and sensations momentarily absent, that 
 the more simple general names are substitutes for images and 
 impossible sensations, that the more complex general names 
 are substitutes for other names, and so on. It seems then 
 that nature has undertaken to provide in us representatives 
 of her events, and has effected her purpose in the most econom- 
 ical way. She has provided, first, the sensation which trans- 
 lates the fact with more or less precision and delicacy ; then, 
 the surviving sensation capable of indefinite revival, that is to 
 say, the image, which repeats the sensation, and consequently 
 translates the fact itself; then, the name, a sensation or image 
 of a particular kind, which, by virtue of its acquired properties, 
 represents the general character of many similar facts, and re- 
 places the impossible images and sensations which would be 
 necessary to translate this isolated character. By means of 
 this correspondence, of this repetition, and this replacement,
 
 I4 2 OF SENSATIONS. [BOOK III. 
 
 external facts, present, past, future, special, general, simple, 
 or complex, have their internal representatives, and this men- 
 tal representative is always the same internal event, more or 
 less compounded, repeated, and disguised.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. 
 
 BOOK IV. 
 
 OF THE PHYSICAL CONDITIONS OF MENTAL EVENTS. 
 
 CHAPTER I. 
 
 OF THE FUNCTIONS OF THE NERVOUS CENTRES. 
 
 I. WE must stop here and change our route ; we have 
 come to the end of psychological analysis ; let us see how far 
 physiological analysis will carry us. 
 
 We have explored, as geologists, a great country, from its 
 highest peaks to its seaboard, and, through all the accidents 
 of surface, have recognized one and the same stratum sup- 
 porting all the different varieties of soil. From our most ab- 
 stract ideas to our crudest sensations, we have constantly 
 found the same fundamental layer ; ideas are sensations or 
 images of a certain kind ; images themselves are sensations 
 capable of spontaneous revival. At the foundation of all these, 
 we invariably find the sensation. But, when we come to the 
 sensation, we are at the limits of the mental world ; between 
 it and the physical world there is a gulf, and, as it were, a 
 deep sea ; we can no longer make our accustomed borings ; 
 the water prevents us from examining whether the layer we 
 have traced from end to end of the land goes on beneath 
 it to rejoin the other continent. In five places, on the ter- 
 ritory of the five senses, we have attempted to step over the 
 ordinary bounds ; with respect to the sensations of sight and 
 hearing, we have pushed on to a considerable distance ; with 
 those of taste and smell, some advance has been made ; and 
 we see that, later on, a similar one may be accomplished with 
 sensations of touch. From all these indications, we have con- 
 cluded that the sensations of each sense, and probably those of 
 the different senses, though apparently differing inequality, dif-
 
 OF MENTAL EVENTS. [BOOK IV. 
 
 fer in quantity only, that the same elementary sensations may, 
 by their differences of number, intensity, and proximity, make 
 up whole sensations which consciousness pronounces irreduci 
 ble to one another, and which therefore, different as they may 
 apparently be, probably comprise one and the same fact, a 
 kind of primitive rock whose different aspects are owing to 
 the different depths of the water covering it. We have further 
 proved that this rock, though invisible at a certain depth of 
 water, still subsists there and is indefinitely prolonged, since 
 at a certain degree of brevity or weakness, the sensation, though 
 imperceptible to consciousness, is nevertheless real, and is 
 found to be made up of infinitesimal elements. Beyond, then, 
 the psychological world observable by consciousness, there 
 extends to infinity a pyschological world to which conscious- 
 ness does not attain. Here then we part from consciousness, 
 which can teach us nothing further, and pass to the other con- 
 tinent, to see if anatomy and physiology will not, on their side, 
 indicate to us some projecting rock, connecting itself with ours, 
 beneath the obscure sea which appears forever to separate the 
 countries. 
 
 II. Let us look then for the physical facts on which our 
 mental events depend, and first, for the conditions of sensa- 
 tion. These are direct or indirect, and make up a chain 
 whose earlier links act only when the last one is affected. 
 
 Let us trace this chain. In the first place, there is the 
 physical external event, the undulation of air or ether, the 
 chemical action of the liquid or volatile body, the mechanical 
 pressure, the change of temperature, which by dilatation or 
 contraction of the parts arrives at affecting the nerve. This 
 condition is plainly but an accessory and distant one. Though 
 the nerve be so constructed as to translate more specially ex- 
 ternal movements of a certain type, it has its own type of 
 action ; it is a spring which, however it be set going, works in 
 one way.* The optic nerve when excited gives no other 
 sensations than those of light; its various stimuli result in 
 the same effect. An undulation of ether strikes it, and we 
 have sensations of color. It is excited by compressing the 
 
 * Mueller, " Physiology " (tr. Baly), ii. 1069.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. 145 
 
 eyeball, and we see brilliant circles, which are termed phos- 
 phenes. It is divided in a surgical operation, and at the mo- 
 ment of its section, the patient sees sudden large bodies of 
 light. An electric current is applied to it, and we see vivid 
 flashes of light. Digitalis is absorbed into the blood, and the 
 blood so altered excites in it sensations of flickering light. So 
 again the acoustic nerve gives no other sensations than those 
 of sound,* whatever be the external event which sets it in op- 
 eration, whether an undulation of air, electricity, irritation 
 of the blood, or a narcotic absorbed into the blood. So it is 
 with the other senses, and notably with that of touch. The 
 tactile nerves serve better than any others to prove this ; for 
 they are excited by a number of different external events, 
 mechanical contact or pressure, the chemical action of caustics, 
 of the air, and blood, change of temperature, undulations of 
 air or ether, section with the bistoury ; their action invariably 
 results in a sensation of contact, or pressure, of temperature, 
 or of pure pain. 
 
 Not only has each kind of nerve its special action, but the 
 action of each kind is different. The external event may be 
 the same, but, if it sets in motion nerves of different kinds, 
 the sensations excited will be different. The same electric 
 action arouses, according to the nerve it sets in action, here a 
 sensation of light, there of sound, elsewhere again one of 
 shock or of pricking. The same violent blow arouses a sensa- 
 tion of pressure and pain through the tactile nerves, of light 
 through the medium of the optic nerve, of sound through the 
 medium of the acoustic nerve. The same narcotic, intro- 
 duced into the blood, arouses flashings when acting on the 
 optic nerve, ringings when acting on the acoustic nerve, for- 
 mication when acting on the tactile nerves. Thus each dis- 
 tinct kind of nerve has its individual and distinct mode of 
 action. 
 
 Hence it follows that all external excitants may be absent ; 
 if the nerve enters into action of itself, we should have the 
 
 * That is, in the Limacean branch. See Flourens's experiments. On the 
 other hand, it is sensible to pain in the vestibular branch ; this then belongs to the 
 group of tactile nerves. 
 IO
 
 146 OF MENTAL EVENTS. [BOOK IV. 
 
 same sensation in their absence as in their presence. And, in 
 fact, this is what happens : we experience without their con- 
 currence a number of sensations which we term subjective or 
 consecutive. They are especially numerous in the case of 
 sight ; the excitation of the optic nerve, and the consequent 
 sensation of colors or of light, lasts after the undulation of 
 ether has ceased to impress the retina ; in such a case we con- 
 tinue to see, with closed eyelids, or with the eye turned in a 
 different direction, the object we were first looking at ; accord- 
 ing to the circumstances, the object is uncolored or colored, 
 of persistent or of changing color ; and these illusions are 
 subject to known laws by which a multitude of singular facts 
 are explicable.* The same kinds of spontaneous sensations 
 are found in the sense of hearing. " Such are the ringings 
 and buzzings in the ears heard by persons of delicate nerves 
 and patients with disease of the auditory nerve ; such, too, is 
 the noise heard in the ears for some time after a long journey 
 in a noisy vehicle."f Subjective sensations of taste and smell 
 are not so easy to detect. If some patients are continually 
 complaining of smelling fetid odors, it is not certain that the 
 origin of their sensation is in the nerve itself; it may possibly 
 be found in the nervous centres. But there is nothing more 
 common than spontaneous action of the nerves of touch ; it 
 is enough to mention neuralgia, strictly so called ; the simple 
 action of the nerve, in the absence of all appreciable excitants, 
 arouses, maintains, and then revives the keenest and most 
 various sensations of pain. 
 
 This is why, if the state of the nerve changes, though the 
 excitant continue the same, the sensation changes in de- 
 gree, or even in quality. For instance, if the nerve has be- 
 come unduly excitable, the least stimulus develops an ex- 
 treme action, and the sensation is of terrible intensity ; this 
 is the case with the unfortunate patients who suffer from hy- 
 peraesthesia of the optic, acoustic, or tactile nerves. If, on the 
 other hand, the nerve has become less excitable, or has ceased 
 to be excitable at all, the strongest stimuli will only arouse in 
 
 * Helmholtz, " Handbuch der Physiologischen Optik." 2me partie, 22-25 
 f Mueller (tr. Baly), ii. 1072, 1210, 1310.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. i^j 
 
 it weak or imperceptible sensations ; this happens when the 
 nerve is divided, tied, benumbed with cold, or paralyzed by 
 illness. Finally, if the nerve has become excitable in a differ- 
 ent way, its action, though induced by the same stimulus, is 
 different, and the sensation is no longer the same ; in indiges- 
 tion or fever, all kinds of food have an earthy or bitter taste. 
 In short, the direct condition of the sensation is the action 
 or molecular motion of the nerve ; neither external events nor 
 the other internal events of the living body matter much ; they 
 only act by means of the movement they excite ; in them- 
 selves, they do nothing ; they may be dispensed with. If the 
 action of the nerve were always spontaneous, as it sometimes 
 is ; if this action were still produced according to the ordinary 
 order and degree, the external world, and all within us ex- 
 cepting the nervous system, might be annihilated ; we should 
 still have the same sensations, and consequently the same 
 images and the same ideas. Let us look, then, more closely 
 into this nervous action, since there is no sensation without 
 it, and since it is sufficient of itself to excite sensation. 
 
 III. When a sensitive nerve commences to act, a molecular 
 movement is propagated through its whole course till it reach- 
 es the nervous centres.* The nerve is a conductor, just as 
 the air which transmits the oscillations of a vibrating string, 
 or the iron wire which transmits electric action. Two exper- 
 iments prove this. If it is compressed, tied or cut at any point 
 between the nervous centres and the spot excited, there is no 
 longer any sensation ; in this case the nervous centres are in 
 tact, the terminal extremity of the nerve acts as before ; the 
 central part of the nerve, then, is what has ceased to act ; there- 
 fore, it was previously acting; therefore when, in consequence 
 of a terminal excitation, a sensation is produced, the nerve 
 has acted in all its segments and through all its course. On 
 the other hand, in all parts of its course, this action results in 
 the same effect.f At whatever point it may be irritated, the 
 
 * This movement is produced in the central filament of the nerve, termed the 
 axis-cylinder. It is the only essential part of the nerve. Vulpian, " Lemons sur la 
 Physiologic du Systeme Nerveux.," p. 55. 
 
 \ Mueller, " Physiology" (tr. Baly), i. 636. Of the laws of action of sensitive 
 nerves.
 
 I4 8 OF MENTAL EVENTS. [BOOK IV. 
 
 final sensation is the same. This extends so far that some- 
 times our associated images localize the sensation in parts 
 which are insensible or absent. " There are kinds of paralysis 
 in which the limbs are absolutely insensible to external irrita- 
 tions, though the severest pains are felt there." The fact is, 
 the nerves which supply these limbs, though insensible at their 
 extremities, are still irritable and irritated in the higher parts 
 of their course. For the same reason, any section, compres- 
 sion or irritation of a nervous trunk exites a sensation which ap- 
 pears to be situated in the parts to which the branches and 
 terminal fibres of the trunk lead. If the arm be compressed 
 with a tourniquet till it is insensible to excitations from with- 
 out, and if the nervous trunk between the two bones of the 
 elbow be then pressed, a keen sensation will be felt similar to 
 that of an electric shock, and this sensation appears to be situ- 
 ated in the part whose nerves are benumbed. Every one has 
 heard of the illusions of persons who have lost limbs. " These 
 illusions persist and retain the same intensity through the 
 whole of life ; we may convince ourselves of this by question- 
 ing persons who have suffered an amputation a long time after 
 they have undergone the operation. They are most vivid at 
 the time of the inflammation of the stump and nervous trunks ; 
 the patients then complain of very severe pains throughout 
 the limb which they have lost. After the cure there frequent- 
 ly remains for life a feeling of formication, or even of pain, seat- 
 ed apparently in the non-existent external parts. These sen- 
 sations are not vague, for the patient feels pains or pricking in 
 some particular spot, the heel, the sole, or the back of the foot, 
 the skin, etc. They end by becoming accustomed to it, and 
 finally cease to perceive it ; still, if attention be called to it, 
 the sensation reappears, and is often felt very distinctly in 
 the heel, the fingers, the sole of the foot, the hand," etc. In 
 many cases, after seven, twelve, or even twenty years, the sen- 
 sation is as plain as on the first day. We see that for the 
 purpose of exciting the sensation, the action of nerve is itself 
 accessory only ; it is only a medium ; if the molecular move- 
 ment which is propagated along its course is effective, it is 
 simply because it excites another molecular movement in the 
 nervous centres ; just as the electric action that runs along
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. i^g 
 
 the telegraph wire has no importance till it arrives at its des- 
 tination and moves the needle of the dial-plate. 
 
 What is this molecular movement which is propagated 
 throughout the conducting nerve ? We cannot tell ; all we 
 know are some of its characteristics.* We prove that in the 
 sensitive nerves, though its usual course is in the direction of 
 the centres, it may also be directed towards the extremities. 
 If we engraft the end of a rat's tail into the skin of its back, 
 and then, when the grafting process is completed, cut the bas- 
 ilary portion of the tail about a centimetre from the root ; 
 after some months, if the grafted tail be pinched, the animal 
 feels it, and turns round to bite ; the irritation of the nerve, 
 which, before the operation, acted in a centripetal direction, 
 now acts in a centrifugal one. We can further prove that the 
 molecular movement is the same in a motor nerve and in a 
 nerve of sensation. For if we unite end to end the fibres of 
 a motor nerve, as the hypoglossal, with those of a sensitive 
 nerve, like the lingual, on the one hand, the irritation of the 
 sensitive nerve is visibly propagated along the motor nerve, 
 and produces muscular contractions ; while, on the other hand, 
 it is very probable that the irritation of the motor nerve is 
 propagated along the sensitive nerve, and excites pain. We 
 finally establish that " every excitation applied to any part of 
 the length of a nervous fibre is immediately and simultaneously 
 transmitted in two directions, centripetal and centrifugal,' 
 and we have some indications as to the velocity of this trans- 
 mission. f The conclusion from all this is, that " the intimate 
 phenomena caused by an excitation of the nervous fibres are 
 certainly identical, whether those fibres are motor, sensitive, 
 or sympathetic." If the final effect be different, it arises from 
 the different ramifications of the nervous fibres, some being in 
 connection with muscles, and others, with particular parts of 
 the nervous centres ; just as similar wires, which are the thea- 
 tre of similar electrical phenomena, produce according to the 
 
 * Vulpian, op. cit., 102, Experiments of Helmholtz, ib., 283 ; of Bert, ib., 287 ; 
 of Philipeaux and Vulpian, ib., 290. 
 
 \ According to the most recent experiments, it is twenty-nine metres a second 
 in the nerves of the human body. It varies with the surrounding temperature, 
 and is not uniform throughout the length of the nerve.
 
 jijO OF MENTAL EVENTS. [BOOK IV. 
 
 apparatus they are connected with, sometimes the ring of a 
 bell, sometimes the displacement of a needle, sometimes the 
 impact of a handle. 
 
 Hence it follows that the immediate condition of the sen- 
 sations found in the nervous centres; where there is pro- 
 duced a molecular movement of unknown nature, without 
 which the sensation cannot arise, and which is of itself sufficient 
 to give rise to it. And this, in fact, is what happens in very 
 many cases. Many sensations arise in us without the inter- 
 vention of the nerves, and by the simple excitation of the 
 nervous centres. Such are hallucinations, strictly so called, of 
 which we have seen numerous examples,* and, in which cases, 
 we can, on most occasions, neither prove nor conjecture the 
 existence of any irritation of the extremity or any portion of 
 the course of the nerve. I have described the visions which 
 precede sleep, and which any one may observe in himself; in 
 such a case, we close our eyes, we discard all excitation from 
 without, we pacify all the nerves, and, as might be expected, 
 in the universal stillness of all the conductors which usually 
 set the brain in action, our vague and feeble images become 
 intense and clear ; they are turned into sensations ; we dream, 
 we see absent objects. Excepting in the absence of objects 
 and the inaction of the nerves, our state is the same then as 
 in the cases of ordinary sensation ; the brain is then acting 
 as in the case of ordinary sensation ; and it alone is acting, 
 owing to the absence of objects and the inactivity of the nerves. 
 When it is excited directly and alone, hallucinations are 
 produced, that is to say, spontaneous sensations with their as- 
 sociated images ; and this is what happens when the brain is 
 inflamed, or irritated by haschich. Besides, medical observ- 
 ers have recorded many instances of patients some of whose 
 nerves have been more or less completely destroyed, though 
 the hallucinations corresponding to these nerves have been 
 perfect.f Esquirol mentions among other cases that of " a 
 Jewess, thirty-eight years old, blind and insane, who never- 
 
 * Book ii. chap. i. 
 
 f See Griesinger, " Traite des Maladies Mentales," 101-5, for numerous exam- 
 ples.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. i$i 
 
 theless saw the most extraordinary objects. She died sudden- 
 ly ; I found the optic nerves atrophied from their point of inter- 
 section to the points where they enter the eyeballs ; in this 
 case the transmission of impressions was clearly impossible." 
 " Two persons had each of them lost an eye by phthisis of ' 
 the eyeball, and in their cases hallucinations were produced 
 as readily on the side on which the eye was lost as on that 
 of the sound eye." " We have at present in the Salpetriere," 
 says Esquirol, " two women who are absolutely deaf, and who 
 have no other delusion than that of hearing the voices of dif- 
 ferent persons, with whom they dispute night and day," 
 Strictly it might be objected that in these instances the cen- 
 tral and as yet intact portion of the nerve is the starting-point 
 of the irritation ; but this is not probable ; the hallucination 
 is too systematic ; if it proceeded from the nerve, it would be 
 requisite that its different fibres should enter into action in 
 the complex order and with the exact degree which an exter- 
 nal excitant could alone impose on them. " A direct irrita- 
 tion," says Griesinger, " may certainly occasion luminous patch- 
 es, globes of flame, and colored figures in the retina, but not 
 complex forms, such as houses, men, trees ; it may determine 
 buzzings and noises, loud or otherwise, in the ear, but not 
 actual words or tunes." The distinction is still more clearly 
 marked in the hallucinations following the use of the micro- 
 scope ; the details of which I give from a letter written me by 
 one of our most distinguished micrographists, M. Robin. " I 
 have remarked," says he, " that after having looked through 
 a microscope for some time, and especially when I have been 
 aided by a strong light, the figures of the objects observed 
 persist when I close my eyes. They still persist whether I 
 direct my eyes on the mahogany table holding my instruments, 
 or on my drawing-board, which is of a grayish-blue, or on my 
 drawing-paper. They persist for about two or three minutes, 
 oscillating about in a narrow circle ; after diminishing in size 
 and then disappearing they reappear, though paler; after 
 two or three reappearances, more and more faint, they cease 
 to reappear. They disappear more readily when I rest my 
 eyes on a white paper than when I turn or rest them on my 
 table, which is of dark mahogany. I see them of a grayish
 
 !$2 OF MENTAL EVENTS. [BOOK IV. 
 
 color, just as the images of objects seen under the microscope. 
 These images are the shadow of the objects, projecting itself 
 on the retina, which is brightly lighted up around them in the 
 circular field of the microscope, just like the Chines? sliadows 
 of the magic lantern" In my opinion, adds M. Robin, it is not 
 the retina which, continues and recommences to act in the ab- 
 sence of the object ; " it is the cerebral centre of visual percep- 
 tion," which having once acted, recommences two or three times 
 to act of its own accord. " I do not think the external ex- 
 tremities of nerves of sensibility, or organs of impression, are 
 capable of such spontaneous action as to transmit the form, 
 color, etc., of an object to the perceptive centre ; but, on the 
 other hand, the centre of perception itself may return spon- 
 taneously to a preceding state of activity, under the influence 
 of some temporary congestion of its vessels, such as is pro- 
 duced by the prolonged use of the microscope, or the ingestion 
 of the alkaloids of opium, or of belladonna, absinthe," etc. In 
 fact, diseases of the eye with congestion of the retina, but un- 
 accompanied by meningitis, do not recall to the scene images 
 of this kind, but entirely different ones ; to arouse these, there 
 must be meningitis, the intoxication of opium or absinthe, 
 that is to say, irritation of the nervous centres. To sum up, 
 irritation of the nerves and that of the nervous centres are 
 recognizable by symptoms of marked difference. " The first, 
 which we may term pseudassthesia of the peripheral extrem- 
 ities, is characterized by luminous sparks and flashes, by 
 noises, ticklings," and other isolated sensations, not forming 
 a system and not corresponding to any possible combination 
 of external characters. " The second, which we may term 
 pseudaesthesia of the perceptive centres," is characterized by 
 the persistence or revival of complete images, like those of 
 the microscope that is to say, by hallucinations or spontan- 
 eous and organized sensations of color and relief, of harmonized 
 and articulate sounds, corresponding to a possible combina- 
 tion of external characters. 
 
 IV. We have then finally settled that the necessary 
 and sufficient condition of the sensation and therefore of 
 images, is a certain action or molecular movement of the ner- 
 vous centres, that is to say, of the encephalon ; in fact, all
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. j^ 
 
 nerves of sensation terminate there, either directly, as is the 
 case with the cranial nerves, or indirectly, as the rachidian 
 nerves, through the medium of the conducting parts of the spi- 
 nal marrow.* We must now inquire, what among the different 
 parts of the encephalon are those whose action is the neces- 
 sary and sufficient condition of sensation and of images? For 
 this purpose physiologists employ vivisections, and their exper- 
 iments are very decisive in the matter. Let us first consider 
 the pure sensation. 
 
 If the reader will examine a preparation of the encepha- 
 lon, or at all events the figures of some large anatomi- 
 cal atlas, he will find that the spinal marrow at its upper 
 extremity swells out into a bulb termed Medulla Oblongata 
 or rachidian bulb, with which the encephalon commences. 
 We may cut away from an animal the whole encephalon 
 excepting this bulb ; the animal will still execute a number 
 of systematic and automatic movements, which are termed 
 reflex, and which are produced by the different segments 
 of the marrow without the intervention of the encephalon.f 
 For instance, it swallows food, the muscles of its face still 
 contract in an expressive manner, it articulates vocal sounds, 
 and goes through all the movements of respiration ; but it can 
 no longer experience sensations strictly so called. It utters 
 cries, but mechanically only ; it no longer suffers pain. Let 
 a transverse section be made above the bulb. " The bulb 
 and marrow are then isolated from the encephalic centre, just 
 as if the brain and annular protuberance were removed ; this 
 is what I do to this rat. I now pinch its paw ; you hear a 
 short slight cry. I do so again; another similar cry. I 
 now wound deeply the rachidian bulb ; I again pinch a hind 
 limb ; there are reflex movements, but there is no longer any 
 
 cry Observe the character of the cries you have just 
 
 heard, they are re flex cries, and very different from cries indica- 
 ting pain." There is in the bulb, as in the different segments 
 of the marrow, a mechanism capable of acting, either directly 
 by the irritation of the sensitive nerves it receives, or indi- 
 
 * Brown-Sequard, " Journal de Physiologic ;" and see ante book iii. chapter 
 2, p. 136. | Vulpian, op. cit., 496, 510.
 
 154 OF MENTAL EVENTS. [BOOK IV. 
 
 rectly by the effect of the sensations aroused in the other parts 
 of the encephalon. When the other parts are cut away, the 
 bulb continues to act, and the cry is produced, without any 
 sensation having been excited. Let us next preserve, not 
 only the rachidian bulb, but also the part of the encephalon 
 adjoining it the Pom Varolii or annular protuberance through 
 which the fascia of the bulb pass, and remove the remain- 
 ing parts, that is to say, the cerebral lobes, the corpora 
 striata, the optic thalami, and the corpora quadrigemina. 
 " When this is effected on dogs and rabbits, they manifest by 
 violent agitation and plaintive cries, the pain they feel when 
 the trigeminal nerve is pinched, or when they are subjected 
 to keen external stimuli. If the protuberance be then deeply 
 wounded, there are no more cries or agitation, even under 
 violent pinchings ; and yet the circulation, respiration, and 
 other functions continue to be accomplished for some time. 
 .... I have repeated M. Longet's experiments, and have 
 obtained precisely the same results as his. This young rab- 
 bit has, strictly speaking, no brain, neither corpora striata, 
 nor optic thalami ; all there is left in its skull are the annular 
 protuberance, the rachidian bulb, the cerebellum, and the 
 corpora quadrigemina.* I pinch its tail sharply ; you see it 
 is at once violently agitated. I pinch its ear, its lip ; similar 
 agitation, and similar cries. Can these cries be considered 
 as reflex phenomena?" By no means. "You have seen 
 animals from which the whole encephalon, excepting the ra- 
 chidian bulb, has been removed; these animals continued to 
 cry when pinched ; but what a difference between their cries 
 and those we hear when we have left the protuberance intact ! 
 In the first case, each excitation of a still sensible part excited 
 a short cry, single for each separate excitation, always the same, 
 and something like the sounds given out by children's toys 
 when pressed in a certain way in a word, deprived of all 
 kind of signification. There we have the reflex cry. But 
 
 * Other experiments show that the cerebellum does not intervene in sensation ; 
 the functions of the corpora quadrigemina will be presently explained. Mean- 
 while this experiment may be considered as conclusive as if the cerebellum and 
 corpora quadrigemina had also been removed.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. 155 
 
 here, with this rabbit, what a difference we find ! When a 
 sensible part is irritated the cry is not a short but a prolonged 
 one, unmistakably plaintive, and, after a single excitation, 
 the animal gives several successive cries, precisely similar to 
 the cries of pain which another uninjured rabbit gives when 
 it is subjected to sharp irritation."* Hence action of the 
 protuberance is the necessary and sufficient condition of tac- 
 tile sensations. It is also the necessary and sufficient con- 
 dition of sensations of hearing. " A certain call made with 
 the lips, of rough purring noise like that of an angry cat, will 
 always startle ah uninjured rat. Now here is a rat from 
 which the brain, strictly so called, the corpora striata, and 
 the optic thalami have been removed. You see him he is 
 very quiet ; I make the noise I have just described, and the 
 animal at once gives a sudden jump. Every time I make a 
 similar noise you see a similar jump. Those of you who have 
 noticed the effects of being so startled upon an uninjured 
 rat will recognize that they are of precisely the same charac- 
 ter as we see here."f Finally, the action of the protuber- 
 ance is also the necessary and sufficient conditions of sensations 
 of taste. " I have removed the cerebral lobes from kittens 
 and puppies; and on pouring down their throats a concentra- 
 ted decoction of colocynth, I have seen them go through 
 abrupt motions of mastication, and contort their lips, as if to 
 rid themselves of a disagreeable sensation. The same move- 
 ments were observed in an uninjured animal of the same 
 species, when forced to swallow the same bitter decoction. ": 
 There is, then, a special centre, the protuberance, whose ac- 
 tion is the necessary and sufficient condition of many kinds 
 of sensations. There are other similar centres which perform 
 the same office with respect to other sensations. For the sen- 
 sations of sight, they are the corpora quadrigemina or bigem- 
 ina. " Here is a pigeon whose cerebral lobes are entirely re- 
 moved, but whose corpora bigemina remain ; when I sud- 
 denly put my hand near it, it makes a slight movement of the 
 head to avoid the threatened danger. The sight then is re- 
 
 * Vulpian, op. cit v 541. Experiments of Longet. \ Vulpin, op. cit, 548. 
 \ Longet, " Traite de Physiologic," ii. 243. Vulpian, 548.
 
 156 OF MENTAL EVENTS. [BOOK IV. 
 
 tained. We have here a phenomenon analogous to that which 
 we noticed in the case of the rat deprived of its cerebral lobes, 
 when we induced a sudden jump by means of certain sudden 
 noises. Here again we have an example of sensations with- 
 out the intervention of the brain strictly so called."* If, on 
 the other hand, we leave intact the cerebral lobes, and injure 
 or destroy the corpora quadrigemina, the animal becomes 
 blind, preserving, nevertheless, all its ideas, its instincts, and 
 its other sensations. The corpora quadrigemina, then, furnish 
 by their action the sufficient and necessary condition of visual 
 sensations, and of visual sensations only. As to sensations 
 of smell, experiments have not yet been made to determine 
 the portion of encephalon whose action is their necessary and 
 sufficient condition ; but all anatomical and physiological anal- 
 ogies lead us to the belief that, for them, as for the other four 
 kinds of sensations, there is a centre, distinct from the cere- 
 bral lobes themselves. When excited by the action of the 
 sensitive nerves, the cells of these centres perform their func- 
 tions in an unknown manner, and this special molecular move- 
 ment, without which there is no sensation, is in itself sufficient 
 to arouse the sensation. 
 
 V. It must be observed that we have here been dealing 
 with pure sensations, or with what physiologists call crude 
 unelaborated sensations, that is to say, with sensations un- 
 provided with the faculty of spontaneous revival, and there- 
 fore with the faculties of being associated, of forming fixed 
 groups, and of furnishing means for the higher operations of 
 intelligence. We must now look to another class of experi- 
 ments, and here again the concordance of physiology with 
 psychology is as complete as unforeseen. Psychological an- 
 alysis had already separated the functions ; physiological an- 
 alysis separates the organs. The first placed on one side pure 
 sensations, on the other images or reviving sensations ; the 
 second puts on one side the corpora quadrigemina, the pro- 
 tuberance, and perhaps another ganglion, whose activity 
 arouses pure sensations, and on the other side the cerebral 
 
 Vulpian, 557. Experiments of Flourens and Longet.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. \^>j 
 
 lobes, whose action arouses images, that is to say, reverber- 
 ates, prolongs, and associates sensations. 
 
 If the reader will look again at a prepared encephalon, he 
 will see that, from the anterior angles of the annular protu- 
 berance, spring two large white columns, called cerebral pe- 
 duncles or crura cerebri, whose fibres terminate in the swell- 
 ings called optic thalami and corpora striata, which are inter- 
 mediate organs to the cerebral lobes and the protuberance. 
 In fact, other fibres start from these organs and terminate in 
 the cerebral lobes.* As to the cerebral lobes themselves, 
 they constitute, particularly in the superior animals, the great- 
 est part of the encephalon. In man they are enormous, and 
 occupy by far the largest part of the cranium. Comparative 
 anatomy has already foreshadowed their use by showing us 
 that in the animal series their volume increases at the same 
 rate as intelligence ; we shall, moreover, find that their most 
 important part is the outer layer, composed of a gray sub- 
 stance ; and it is a no less significant circumstance that, as we 
 ascend the zoological scale, this surface increases much more 
 quickly than the volume owing to the very numerous swellings 
 and anfractuosities which bend it into folds and are called 
 circumvolutions.f In man himself, atrophy of the cerebral 
 lobes and absence of circumvolutions are always accompanied 
 with idiocy ; " when a brain is below a certain volume and 
 certain weight, it must necessarily have belonged to a,person 
 affected with imbecility . . . ; " and, in general, if we compare 
 different races of men, " the volume of the encephalon is in 
 proportion to the degree of intelligence." All these presump- 
 tions are confirmed by our operations on living animals ; it is 
 sufficient to resume the preceding experiments \\ when we 
 have removed th-e cerebral lobes, the rest of the encephalon 
 being intact, pure sensations still, as we have seen, subsist ; 
 but they alone subsist. The animal still experiences crude 
 sensations of light by means of the corpora quadrigemina, crude 
 
 * Vulpian, 652, following Koelliker. 
 
 f Broca, " Sur le Volume et la Forme du Cerveau, suivant les individus et sui- 
 vant les Races." Paris, 1861. 
 
 \ Vulpian, 690. Flourens, 2me edition, " Recherches Experimentales sur les 
 Proprietes et les Fonctions du Systeme Nerveux," 24.
 
 j^S OF MENTAL EVENTS. [BOOK IV 
 
 sensations of pain, contact, sound, and taste, by means of the 
 protuberance. But these are bare sensations ; they are not, 
 as in the normal state, accompanied and clothed with associa- 
 ted images, which add to the sensation of light notions of the 
 relief, distance, and other characters of the luminous object ; 
 to the sensation of contact, notions of situation, resistance, 
 and form ; to the sensation of sound or taste, the representa- 
 tion of a sonorous or savory body. Much less then, can these 
 isolated sensations arouse the associated. images constituting 
 memory and prevision, and through them judgments, and all 
 the assemblage of emotions, desires, fears, and determinations 
 developed by the notion of approaching danger or of future 
 pleasure. 
 
 Another consequence is the absence of instincts ; for in- 
 stincts are constituted by groups of images whose association 
 is innate. A beaver shut up in an enclosure in the Jardin 
 des Plantes, who collects pieces of wood and mortar to make 
 a dam of which he has no need in Paris, and of which he has 
 need in America, is an animal in whom are developed a spon- 
 taneous system of images ; so, again, is a bird who builds his 
 nest in the spring ; at the sight of straw, hair, and wool, the 
 notions of their combination and usage arise in him without 
 preliminary experience, without tentative effort, in a fully 
 constructed order, by an unacquired wisdom. It matters 
 little whether this order be, as with man, the effect of a per- 
 sonal apprenticeship, or, as with the brutes, the play of an 
 hereditary mechanism ; it is invariably an order of represen- 
 tations that is to say, of grouped images ; and therefore, if 
 the images are destroyed, it is destroyed. 
 
 This is what happens when the cerebral lobes are cut 
 away. "The animal loses all its intelligence." Though, with 
 the corpora quadrigemina and protuberance, it may have re- 
 tained crude sensations, it no longer has the images which 
 by their association with crude sensations give it the notion of 
 objects. " These objects continue to paint themselves on the 
 retina ; the iris remains contractile, the optic nerve excitable ; 
 the retina remains sensible to light ; for the iris contracts or 
 expands accordingly as the light is more or less vivid ; so the 
 eye is sensible. And still the animal no longer sees "
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. i^g 
 
 A pigeon thus operated on "kept itself well upright ; it flew 
 when thrown in the air; it walked when pushed on from 
 behind ; the iris of its eyes was very contractile ; nevertheless, 
 it did not see or hear, it never moved spontaneously, it put 
 on all the attitudes of a sleeping or drowsy animal, and when 
 roused from this sort of lethargy, assumed the attitude of an 
 
 animal waking up When I let it alone, it remained 
 
 calm and as it were absorbed ; in no one case did it give signs 
 of will. In short, picture to yourself an animal condemned 
 to perpetual sleep, and deprived of the faculty of dreaming in 
 this sleep" In fact, all the images whose irregular concat- 
 enation forms dreams, and whose regular concatenation forms 
 the waking state, were absent ; all that remained were some 
 few intermittent sensations aroused by the experimenter, 
 and, accompanying them, the dull tendencies and involuntary 
 movements consecutive to them-. A hen lived ten months 
 after a mutilation of this kind, and after the fifth month, was 
 fat, strong, and healthy ; but instincts, memory, prevision, and 
 judgment were gone. " I left her fasting on many occasions 
 for three whole days at a time, and then have put food to 
 her n-ostrils, have dipped her beak in grain, have placed grain 
 in the anterior part of her beak, plunged her beak in water, 
 placed her on a heap of corn. She did not smell, or swallow, 
 or drink, she remained motionless on the heap of corn, and 
 would assuredly have died there of starvation if I had not taken 
 on me to make her eat. I have twenty times put pebbles instead 
 of grain in her beak ; she swallowed the pebbles as she had 
 swallowed the grain.* Finally, when she met with an obsta- 
 cle in her way, she ran against it, and the shock stopped her 
 or shook her. But to run against an object is not to feel it ; 
 
 she never groped about or hesitated in her progress 
 
 She never took shelter, however inclement might be the 
 weather ; she never defended herself against the other fowls ; 
 she no longer knew how to fight or to run away; the ca- 
 resses of the male bird were indifferent or unperceived by her 
 .... She ceased to peck with her bill. 
 
 * By a reflex movement.
 
 OF MENTAL EVENTS. [BOOK IV. 
 
 The same thing happens with other animals.* Frogs 
 have no longer any notion of eating a fly held to their mouths. 
 " The mole ceases to dig, the cat remains quiet even if teased." 
 All images, then, fail, and consequently, those which serve as 
 signs, and by which we have abstract ideas, also perish. Thus 
 all the operations which pass beyond pure sensation not only 
 those which are common to animals with man, but also those 
 which are special to man have, for sufficient and necessary 
 condition, an action of the cerebral lobes. They are, then, 
 
 * Vulpian, 690. Landry, " Paralysies," 82. 
 
 If we take two frogs, one uninjured and the other deprived for some days of 
 its cerebral tubercles. 
 
 " Let them both be put on the floor, the first runs off at once and tries to hide 
 himself. The second, after a leap or two, becomes motionless and remains so. 
 When a noise is made near them, the first will sometimes turn round to see where 
 it comes from and sometimes run away, the second will give a slight start, but 
 will not move. If their paws are pinched they will both jump away, and struggle if 
 they are retained. 
 
 Let them both be put in a large basin of water. 
 
 The uninjured frog goes through several movements of swimming and tries to 
 hide himself at the bottom of the basin. Meanwhile, the movements of respiration 
 have entirely ceased. After a time, it regains the surface of the water in order to 
 breathe, and tries to remain there, but having no hold exhausts itself in its efforts 
 to keep there. When pushed down to the bottom, it soon conies up again, and 
 if prevented from doing so, will attempt to come up at another part of the basin. 
 The frog deprived of its brain behaves very differently. The moment it is 
 placed in the basin it sinks to the bottom like an inert mass without attempting 
 to swim. Still, when stirred with a stick, it goes through the movements of swim- 
 ming but at hazard and without object, and then becomes motionless and sinks to 
 the bottom. In its case the respiratory movements continue to be gone through as 
 in the air, with the single difference that the little membranous lid of the nostrils 
 is completely closed. The animal remains quietly at the bottom of the basin with- 
 out attempting to gain the surface to breathe, and without showing the least un- 
 easiness. The respiratory movements " become abrupt and few, and the frog dies 
 suffocated without having made any attempt to breathe, and without appearing to 
 have suffered. 
 
 " Thus the brainless frog does not know how to suspend respiration, and 
 would inspire water if the lid of the nostrils did not close automatically at the 
 contact of the liquid ; it does not suffer from asphyxia, is not aware of it, and 
 does not attempt to avoid it. Nothing, it seems to me, can better show than this 
 experiment both the real absence of perception, the absence of every intellectual 
 phenomenon, and the absence of will. 
 
 " I admit with M. Flourens that the brain properly so called is the seat of per- 
 ception, volition, and all intellectual phenomena."
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. jgj 
 
 attached to this action ; they rise, perish, are altered, acceler- 
 ated and transformed with it, and pathology here is in accord- 
 ance with vivisection. 
 
 " All the organs," says Mueller, " with the exception 
 of the brain, may either pass slowly out of the circle of 
 the animal economy or perish, without the faculties of the 
 mind undergoing any alteration. It is different with the 
 brain ; any cause which disturbs its action slowly or sud- 
 denly, affects at the same time the mind Inflammation 
 
 of the brain is never unattended with delirium, and at a later 
 period with stupor ; pressure on the cerebrum, whether pro- 
 duced by depressed bones, serum, blood or pus, always gives 
 rise to delirium or stupor, according as there is or is not 
 irritation with the pressure. The same causes, according to 
 the seat of their action, frequently abolish the power of vol- 
 untary motion, or memory ; and when the pressure is removed, 
 the memory frequently returns, and it has been observed 
 that the chain of thought was immediately resumed at the 
 point where it was interrupted by the injury."* After cerebral 
 commotion " there is sometimes complete loss of intelligence. 
 In other cases the patient answers questions put to him, but 
 soon falls again into a drowsy state, his memory is sometimes 
 entirely, sometimes partially gone. Total forgetfulness of a 
 foreign language is one of the most usual effects of this com- 
 motion Patients never recollect how their accident has 
 
 occurred ; if they have fallen from horseback, they recollect 
 perfectly having mounted and got off, but never recollect the 
 circumstances of their fall. The effects of a lesion of the brain 
 are in some ways analogous to those brought on by old age ; the 
 patient preserves the recollection of recent impressions only, 
 and forgets those of earlier date. . . . With some patients, 
 memory remains ever after imperfect. ... In some particu- 
 lar cases patients are unable to avail themselves of the right 
 word to express their ideas, the judgment is often impaired. "f 
 Other injuries indirectly affecting the brain produce similar 
 effects ; we know that people faint when they have lost much 
 blood, that drunkenness disorders the ideas, that narcotics 
 
 * Mueller, op. cit. (tr. Baly), i. 817. 
 f Viclal, " Pathologic Externe," 750 citing Cooper. 
 II
 
 !62 OF MENTAL EVENTS, [BOOK IV. 
 
 produce stupefaction, haschich brings on hallucinations, coffee 
 develops a liveliness of mind, chloroform and ether produce 
 insensibility." * To sum up, alteration of the cerebral lobes 
 has, as a consequence, a proportionate alteration of our images. 
 If the lobes become unfitted for some particular system of ac- 
 tions, some particular system of images, and therefore some 
 group of ideas or of cognitions, is found wanting. If their ac- 
 tion becomes excessive, images of a more intense kind escape 
 from the repression ordinarily imposed on them by sensations, 
 and turn into hallucinations. If, in addition to this their ac- 
 tion becomes disconcerted, images lose their ordinary associ- 
 ations, and delirium is pronounced. If their action be annul- 
 led, all images, and therefore all ideas and cognitions, are an- 
 nulled ; the patient falls into the state of torpidity and deep 
 stupor which we find caused in animals by cutting away these 
 lobes. 
 
 VI. We must now determine on what part of the cere- 
 bral lobes images depend. These lobes are made up of a 
 white substance and gray cortical matter; and all inductions 
 concur in attributing images to the action of the gray cortical 
 matter. In fact, the extent of this cortical matter is augment- 
 ed by that of the convolutions, and comparative anatomy 
 shows us that, in the animal kingdom, intelligence increases 
 with the extent of the convolutions. Physiology again proves 
 that in other parts of the nervous system the white substance 
 is simply conductive. f According to all indications, that of 
 the brain has no other function. " It is evident that here, as 
 in all other parts of the nervous system, the special activity 
 belongs to the gray substance. Pathological observations are 
 
 equally conclusive Whilst lesions of the cerebellum, 
 
 of the optic thalami, of the corpora striata, in fact of the white 
 
 * Longet, ii. 36. The above theory may be verified by the process of ether- 
 ization. This process has two stages. In the first, the animal etherized (dog or 
 rabbit), loses its intelligence, its will, its instincts, and all its faculties with the 
 exception of its crude sensations. In this stage there is etherization of the cere- 
 bral lobes and other parts of the encephalon, but not of the protuberance and 
 bulb. In the following stage the animal also loses its sensations. There is then 
 etherization of the annular protuberance. 
 f Vulpian, 646, 669.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. ^3 
 
 medullary masses of the cerebral lobes, do not ordinarily occa- 
 sion any permanent or clearly marked disturbance of the intel- 
 lectual functions, extensive alterations of the gray substance 
 of the convolutions, or morbid excitation of this substance, 
 necessarily occasion weakening or exaltation of these functions 
 according to the nature of the alteration and the stage at 
 which it has arrived. Thus we can explain the effects of 
 diffused meningo-cephalitis and of simple meningitis. The 
 centre of cerebral activity being thus clearly ascertained, it 
 is not permissible to doubt that we have here the true starting- 
 point of dementia and mania." 
 
 This gray cortical matter is composed of several layers, 
 which are alternately gray and white. * " We see in them 
 nuclei, and very many multipolar nervous cells of small dimen- 
 sions ; " a quantity of fibres connect together different regions 
 of the gray layer of the same lobe, and those of one lobe with 
 the other ; other fibres connect the whole surface of the gray 
 matter with the corpora striata and optic thalami. When trans- 
 mitted by the fibres of the optic thalami and corpora striata, 
 the action, which in the corpora quadrigemina and annular 
 protuberance had aroused a crude sensation, passes on by the 
 fibres of the white substance to the cells of the cortical matter 
 of the cerebrum, and propagates itself, by the intermediary 
 fibres, from one point to another of the gray substance ; this 
 action of the cortical cells is the necessary and sufficient con- 
 dition of images, and consequently of all cognitions or ideas. 
 The scalpel, the microscope, and physiological observation 
 can go no further than this without falling into hypotheses ; 
 we can neither define this action nor explain this propagation, 
 and all we know is that there is a molecular movement in the 
 case. But vivisections and the history of wounds of the head 
 here afford new evidence, which, combined with the former, 
 enables us to gain a general view of the functions of the brain. 
 It is a repeating and mutiplying organ, in which all the differ- 
 ent departments of the gray cortical matter fulfil the same 
 functions. 
 
 In the first place, " it is easy to prove by instances that 
 
 According to M. Baillarger Vulpian, 644.
 
 164 OF MENTAL EVENTS. [BOOK IV. 
 
 with an absence we may term complete of one cerebral hem- 
 isphere, a man may still enjoy all his intellectual faculties and 
 
 even all his external senses This was the case with 
 
 one Vacquerie, in 1821. He was hemiplegic on the left side, 
 but his intellectual functions were intact. At the autopsy, a 
 quantity of serum was found filling the place of the right hem- 
 isphere; the cerebral substance on that side had disap- 
 peared."* Not only does one hemisphere supply the place 
 of the other, but any one region of the brain, if sufficiently 
 large, may supply the place of another ; the proof of this lies 
 in the fact that any portion may be wanting without any of 
 the mental faculties being missed.f The disorganized or de- 
 stroyed portion may belong to the anterior or to the posteri- 
 or lobes of the brain ; it is of little consequence. " Berard 
 reports a case in which the two anterior lobes were crushed, 
 while reason, sensibility, and voluntary movements were re- 
 tained." " An officer had received a ball that had entered 
 one temple and passed out at the other ; the wounded man, 
 who died very suddenly three months afterwards, was observed 
 till then, and, during all that time, not only did he enjoy his 
 full intelligence, but showed unusual cheerfulness and sereni- 
 ty in the intercourse of life." \ After the battle of Landre- 
 cies, " twelve men had received wounds at the top of their 
 heads, as large as the palm of the hand, with loss of substance 
 of integument, bone, dura mater, and brain. These wounds 
 were occasioned by horizontal sabre-cuts. They had all trav- 
 elled more than thirty leagues before their wounds were 
 dressed, sometimes on foot, sometimes in wretched cars, and 
 went on favorably till the seventeenth day. They preserved 
 their appetite, their strength, and even their martial appear- 
 
 * Longet, " Anatomic and Physiologic du Systeme Nerveux," 666, 669. And 
 see Vulpian, 707. The same result is observed in pigeons when one hemisphere 
 has been removed. They preserve or regain all their faculties. 
 
 \ Longet, ibid. Vulpian, 711. 
 
 \ See " Bulletin de 1' Academic de Medecine," x. 6, for an analogous case of a 
 child four years and a half old, through both of whose temples a ball had passed, 
 and who nevertheless lived twenty-six days, enjoying the whole of its intellectual 
 faculties, with complete memory, sound judgment, and with its character unaf- 
 fected by the injury.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. 165 
 
 ance." * .... Such, again, is the case of the dragoon men- 
 tioned by Lamotte, who " had lost by a sabre-cut a piece of 
 the right parietal bone two inches long, and three or four inches 
 of the left parietal bone, down nearly to the ear. This wound, 
 which comprised not only the membranes of the brain but the 
 longitudinal sinus and the brain itself, was followed by syncope, 
 consequent on the loss of blood, but gave rise to no serious 
 ill effects,! and was cured in two months and a half. Lamotte 
 is not the only one who has observed cases of this kind, for 
 they are not very uncommon." All the mutilations practised 
 on animals lead to the same conclusion. " We may remove 
 a considerable portion of the cerebral lobes, either in front or 
 behind, above or below, without their functions being lost. 
 A very small portion, then, of these lobes is sufficient for the 
 exercise of their functions. In proportion as the removal goes 
 on, all the functions are weakened and gradually become ex- 
 tinct, and, when certain limits are passed, they become actu- 
 ally extinct Whenever one perception is lost, all are 
 
 lost; whenever one faculty disappears, they all disappear 
 
 Provided the loss of substance occasioned to the 
 
 cerebral lobes does not exceed certain limits, these lobes re- 
 gain after a time the exercise of their functions ; when these 
 first limits are passed, the functions are but imperfectly re- 
 covered, and, when the new limits are also passed, the func- 
 tions are not recovered at all. In short, as soon as one per- 
 ception returns, they all return, and as soon as one faculty 
 
 * Nelaton, " Pathologic Externe," iii. 572. Vidal, " Pathologic Externe," 
 ii. 744. 
 
 f Cf. Karl Vogt, " Lecons sur 1'Homme," 127. 
 
 " If we gradually, layer by layer, remove the cerebral lobes in an animal, the 
 different phenomena of increasing stupidity become more and more evident, with- 
 out our being able to determine a special action in any one direction. The re- 
 moval of half the brain seems to have no appreciable influence, which shows that, 
 for some time at least, the other entire half is able to supply the place of the miss- 
 ing half. Still, we observe that the functions exhaust themselves more quickly 
 than when the brain is entire, which shows that the operation influences the quan- 
 tity, not the quality, of the manifestation 3 of the organ. Several observations have 
 been collected of men who, after deep lateral wounds of the head, followed by loss 
 of cerebral substance, have experienced no diminution of their faculties, but -were 
 speedily exhausted, and compelled, after short intellectual labor, to stop and abandon 
 themselves to complete repose or even to sleep"
 
 OF MENTAL EVENTS. [BOOK IV. 
 
 reappears, they all reappear." * A frog, which had only a 
 fragment left of its posterior lobes, amounting to about an 
 eighth of the whole brain, had preserved the appearance of a 
 healthy frog. " Five weeks afterwards, a large fly, with one 
 wing removed, was put into its basin, as soon as the fly was 
 in the basin, the frog changed its attitude, and seemed to 
 watch the inject, and, as soon as it came near, made a 
 short jump and tried to catch it with its tongue ; but it 
 did not succeed the first time, and was obliged to recom- 
 mence the movement of projecting its tongue ; this time 
 it succeeded. On the following days, other flies were given 
 it, and it seized them at the first attempt. . . . The only 
 alteration observed in its movements was, that it was a little 
 less lively ; and again, it did not attempt, like other frogs, 
 
 to escape from the hand put out to catch it On the 
 
 contrary, when the brain is completely removed, there is not 
 the least attempt on the part of the frogs to take flies which 
 are given them ; and they do not even swallow the flies till 
 placed at the back of their mouths." We see that in the case 
 of the first frog the eighth part of its brain supplied the place 
 of the rest ; a larger portion would be required in the case of 
 a superior animal, and, when we come to the summit of the 
 animal kingdom, the mutual dependence of the different parts 
 of the brain is much greater. But the conclusion is still the 
 same. The brain is a kind of polypus, whose elements have 
 the same functions. We cannot say with precision how many 
 cells and fibres are required to form one of these elements ; 
 but each of these elements is capable, by its action, of giving 
 rise to all normal images and all their associations, and con- 
 sequently to all the operations of the mind. 
 
 Having settled this, we can, by aid of psychology, take a 
 step in advance. We know that all ideas, all cognitions, all 
 the operations of the mind, are composed of associated images, 
 that all these associations depend on the property of images 
 to revive, and that images themselves are sensations reviving 
 spontaneously. All this agrees with the teaching of physiolo- 
 
 * Flourens, " Recherches Experimentales," etc., 99. Vulpian, 709 (Experi- 
 ments on Fowls and Pigeons).
 
 CHAP. I.J FUNCTIONS OF THE NERVOUS CENTRES. \~ 
 
 gy. An action is produced in the sensitive centres strictly so 
 called, protuberance, or corpora quadrigemina ; it there ex- 
 cites a primary or crude sensation. An exactly similar action 
 is consequently developed in a cortical element of the cerebral 
 lobes, and there excites a secondary sensation or image. The i 
 first action is incapable, and the second is capable of reviving 
 spontaneously; consequently the crude sensation is incapable, 
 and the image is capable of reviving spontaneously. The 
 more extensive is the cortical matter of the brain, the more 
 elements has it capable of setting one another in action ; the 
 more elements it has capable of setting one another in action, 
 the more delicate an instrument of repetition it is. The brain, 
 then, is the repeater of the sensitive centres ; such is its office ; 
 and it will the better fulfil this office the more numerous the 
 repeaters of which it is itself composed. 
 
 Here we perceive the mechanism which renders possible 
 the fundamental property of images I mean, their aptitude 
 for endurance and revival. As the brain is made up of similar 
 mutually-excitable elements, the action of the protuberance, 
 of the corpora quadrigemina, and in general of the centres of 
 sensation, once repeated by one of its elements, is transmitted 
 in turn to the rest, and may thus revive indefinitely. Imagine 
 a series of vibrating strings disposed in such a way that the 
 movement of the first is communicated from string to string 
 up to the last, and reverts from this last to the first ; the illus- 
 tration is homely but clear. Such is the action which runs 
 through the similar elements of the brain ; and thus, in the 
 absence of all external excitation, it lasts on, being effaced, 
 reviving, and so persisting indefinitely through a series of ex- 
 tinctions and revivals. Such too is the image, and we have 
 but to refer back to its* history to see it endure, become ef- 
 faced, and reappear in precisely the same manner. Assuming 
 now that, by a new excitation of the centres of sensation, a 
 different action is produced in one of the cerebral elements ; 
 according to the law of communication, it must pass in turn 
 to the other elements, and we shall have a different image 
 which will persist like the first, while becoming weaker and 
 stronger by turns. But the same cerebral element cannot be 
 in two different states at the same time, and consequently
 
 j6S OF MENTAL EVENTS, [BOOK IV. 
 
 cannot produce two different actions at the same time. The 
 cerebral elements, then, will be drawn in two different direc- 
 tions, and, as the two actions are incompatible, one alone will 
 be propagated. 
 
 Which of them will be propagated ? There are conditions 
 which incline the balance to the one side or the other. Of the 
 two tendencies, one or the other will prevail. * We have seen 
 the laws which confer ascendancy on images and deprive them 
 of it, and these are precisely the ones which determine the 
 propagation of such or such a particular action. Images strive 
 together for predominance, and so cerebral actions strive to- 
 gether for propagation. At any given moment some one ac- 
 tion will be propagated, and will give the ascendancy to some 
 image, and will then make way for another action, which, 
 propagated in its turn, brings on the scene another image. 
 Thus images succeed one another, and become preponderant 
 in proportion as the action producing them is propagated 
 through a greater number of elements. 
 
 It must be observed that this presence of an image is 
 nothing more than its preponderance ; it is considerably 
 stronger than the others, that is all ; but it does not exclude 
 the others ; on the contrary, they still persist in a rudimentary 
 and latent state ; and this obscure persistence may be observed 
 at any moment. You have sung over, some fifteen or twenty 
 times in succession, a new air which has impressed you a great 
 deal ; you are interrupted for some little household occupa- 
 tion, or by some tiresome visit ; on this, another series of sen- 
 sations, images, and ideas unrolls itself perforce within you ; 
 but the first, though it has yielded its place, has not been de- 
 stroyed. It is pushed back, reduced ; it permits the others 
 to occupy the foremost place and to obtrude themselves on 
 the attention ; but though retired and driven back into the 
 distance and shade, it still exists. You will find it there as 
 soon as you revert to it ; it will spring again to the light of 
 its own accord as soon as the intruders have gone. The evi- 
 dence of its secret persistence lies in the disturbance, the un- 
 
 * See ante, Book II. chap. ii. " Laws of the Revival and Obliteration of Im- 
 ages."
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. ifo 
 
 easiness, the dull tendencies which you have felt all the time 
 and which its obscure presence excites in you. So again, 
 you hear news, good or bad, and after an hour you have ceased 
 to think of it ; but nevertheless, after the hour and perhaps 
 for the whole day, you still feel an ill-defined pleasure or in- 
 quietude which you cannot explain at first sight, and which 
 you do not understand till you reflect, and the recollection of 
 the news returns. Among latent images or ideas, we must also 
 reckon those of all the actions we carry out while our minds 
 are occupied by some other preponderant image or idea. For 
 example, we follow out a thought as we walk along ; we follow 
 the tune of the piece we are playing, all the while we are play- 
 ing it ; we follow the argument of an author while we are read- 
 ing him aloud. In these different cases, the images of the 
 muscular movements we wish to accomplish must be present 
 to our minds, since the muscular movements are accomplished ; 
 but their series is not observed because another series is pre- 
 ponderant. This is the constant state of our minds, a domi- 
 nant image, in the full light, and extended around it, a con- 
 stellation of fading images, growing more and more imper- 
 ceptible ; beyond these, a milky way of images wholly invisi- 
 ble, of which we have no other consciousness than by the effect 
 of their mass, that is to say, by our general feelings of gayety 
 or sadness. Every image may pass through all the different 
 states of light and dimness ; at a certain limit, it escapes from 
 consciousness, but it is not therefore extinguished, and we do 
 not know to what degree of obliteration it may possibly de- 
 scend. The scale of these degrees descends to a marvellous 
 depth ; it is enough, to convince one's self of this, to observe 
 the revivals of images* taking place after twenty, thirty, and 
 fifty years' interruption, and the abnormal reproductions of 
 transient experiences which seemed to have left no trace be- 
 hind them. We find here the* same law as in the case of 
 sensations proper ; the image of which we are conscious is 
 but a ivliole whose elements may be infinitesimal. 
 
 Having determined this, we conceive the corresponding 
 
 * " Laws of the Revival and Obliteration of Images." See for different in- 
 stances ante, Book II. chap. ii. pp. 76, 77.
 
 170 OF MENTAL EVENTS. [BOOK IV. 
 
 cerebral process, and further, by this comparison, we under- 
 stand how there may be images within us of which we have 
 no consciousness. When an image is preponderant, the 
 action corresponding to it is propagated through the greater 
 part of the similar cerebral elements ; but through the great- 
 er part only. Without this vortex are other elements, in 
 which a different action may be propagated at the same mo- 
 ment, whose whole intensity is less, since the number of its 
 factors is smaller ; to this action of less intensity corresponds 
 the accessory image, of less intensity, all but invisible to con- 
 sciousness, and which we can only perceive indirectly, in the 
 background. Let the number of factors again diminish, the 
 intensity of the action, and, therefore the intensity of the 
 image will diminish proportionately; a moment will arrive 
 at which the image will be wholly without the range of con- 
 sciousijess, and nevertheless still capable of as many degrees 
 of progressive weakening as the number of its factors is capa- 
 ble of reductions. The series of these degrees and of these 
 reductions may be enormous, and we can conceive that, in 
 addition to secondary and tertiary images, whose presence 
 we may still distinguish or divine, there are images again still 
 more enfeebled, below these, others still more so, and so on, 
 till we come to those aroused by the action of a single cer- 
 ebral element. Similarly we can conceive that the same im- 
 age, having been for a moment preponderant, may be effaced 
 by degrees, may subsist for a long time without our having 
 had consciousness of it, then, of a sudden, to our great sur- 
 prise, may reappear in full light, according to the more or 
 less extended ascendancy of the corresponding action, which, 
 propagated at first through the majority of the cerebral ele- 
 ments, becomes more and more limited, is contracted and 
 grows thinner, then, later on, reassumes the ascendancy by 
 the sudden appearance of some unforeseen sensation which re- 
 news one of its fragments. 
 
 VII. We now know exactly the physical conditions of our 
 mental events ; the condition of our crude sensations* is a 
 
 * Vulpian, 681. "It is a notion of extreme importance in physiology and 
 philosophy, that in every complete sensation there are two wholly distinct phe-
 
 CHAP. I.J FUNCTIONS OF THE NERVOUS CENTRES. iji 
 
 certain action or molecular movement of the protuberance 
 of the corpora quadrigemina, and, in general, of some prima- 
 ry centre of the encephalon ; the condition of our images, 
 ideas, and the rest, is the same molecular movement repeated 
 and propagated in the elements of the gray cortical matter 
 of the brain. On this molecular movement depend the 
 events which we refer to our personality ; if the movement 
 exist, they exist ; if it is missing, they are missing. There is 
 no exception to this rule ; the loftiest thought, the most ab- 
 stract conception, is subject to it, through the words or signs 
 which serve as its foundation. Every idea, voluntary or not, 
 clear or obscure, complex or simple, fugitive or persistent, 
 implies a determinate molecular movement in the cerebral 
 cells. But, besides the mental events perceptible to con- 
 sciousness, the molecular movements of the nervous centres 
 also arouse mental events imperceptible to consciousness. 
 These are far more numerous than the others, and of the 
 world which makes up our being, we only perceive the highest 
 points, the lighted-up peaks of a continent whose lower levels 
 remain in the shade. Beneath ordinary sensations are their 
 components, that is to say, the elementary sensations which 
 must be combined into groups to reach our consciousness. 
 By the side of ordinary images and ideas, are their collaterals, 
 I mean the latent images and ideas, which must take their 
 turn of preponderance and ascendancy in order to reach con- 
 sciousness. 
 
 Having settled this, we see the moral world extending 
 far beyond the limits assigned to it. We are accustomed 
 to limit it to events of which we have consciousness ; but 
 it is now plain that the capacity of appearing to conscious- 
 ness belongs only to certain of these events; the majority of 
 them do not possess it. Outside a little luminous circle, lies 
 a large ring of twilight, and beyond this an indefinite night ; 
 but the events of this twilight, and this night are as real 
 
 nomena, so distinct that they are seated in two different parts of the nervous sys- 
 tem. The one is the sensation strictly so called, and has as its seat the isthmus 
 of the encephalon, and in part, the annular protuberance. The other is the in- 
 tellectual elaboration of the sensation, and takes place in the brain properly so 
 called."
 
 Ij2 OF MENTAL EVENTS. [BOOK IV. 
 
 as those within the luminous circle. Hence it follows, that if 
 we find elsewhere a nervous structure, excitations, reactions, 
 in short all the accompaniments and the physical indications 
 we meet with in the mental events of which we have con- 
 sciousness, we shall have a right here also to conclude the 
 presence of moral events to which consciousness does not 
 attain. 
 
 This is the case with reflex phenomena, one ol the most 
 instructive instances physiology presents. There is in a 
 living body another centre besides the encephalon ; that is 
 the spinal marrow ; this marrow, like the encephalon, com- 
 prises a gray substance, which, like that of the encephalon, 
 is a terminus of transmitted excitations, and a starting-point 
 for reflected excitations. There is produced in it, as in the 
 encephalon, an unknown molecular movement, which is 
 excited by the action of the sensitive nerves, and excites 
 the action of the motor nerves, and which, according to all 
 analogies, arouses, like the molecular movement of the brain, 
 an event of the mental order. In fact, the action it gives rise 
 to in the motor nerves is not irregular ;* " it is appropriate 
 and adapted ;" it seems " intentional." In every case, it tends 
 to an object, " even when the animal is deprived of its en- 
 cephalon," and this so perfectly, that many physiologists 
 have admitted a soul, or at least, " a perceptive and physical 
 centre," in the segment of marrow thus cut off. " Here 
 is a Triton, whose head, with the anterior part of the body 
 and the two corresponding limbs, have been removed by a 
 transverse section. I pinch the skin of the lateral parts of 
 the body ; there is, as you see, a movement of lateral curva- 
 ture of the body, producing a concavity of the irritated side, 
 and it is plain that the result of the movement is to remove 
 the irritated part away from the object irritating it. Now, 
 this is the precise movement which we see in unmutilated 
 
 Tritons when subjected to a similar irritation If 
 
 they do not succeed by this means, they attempt to rid 
 themselves of the irritating object by another plan which 
 this mutilated Triton will also put into execution. You see, 
 
 Vulpian 414, et seq.
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. j^ 
 
 in fact, a movement takes place of the hind limb on the 
 irritated side." The movements alter according to the 
 point irritated, and the new combination of muscular move- 
 ments is always one adapted to avoid the new cause of 
 irritation. "All these movements are so well adapted and 
 natural, that if the wound caused by the decapitation were 
 not apparent, you would think the animal had undergone 
 no mutilation, and the common character of these move- 
 ments is that their effect is defence against attacks from with- 
 out." 
 
 So too, frogs when beheaded, can still leap and swim. 
 Further, " if we put a drop of acetic acid on the upper part 
 of the thigh of a decapitated frog, the hind limb bends in 
 such a way that the foot rubs against the irritated part." 
 The foot is amputated and the experiment repeated. " The 
 animal begins new movements to rub the irritated part ; but 
 he cannot reach it, and after some movements of agitation, 
 as if he were seeking a new mode of accomplishing his 
 design, he bends the other limb, and thus succeeds in doing 
 so." These are the most salient experiments, and it will be 
 comprehended that, to obtain such striking facts, we must 
 operate on the lower animals, whose life is more tenacious, 
 and whose parts are less strictly connected with one another. 
 But similar ones are met with among the mammalia and 
 even in man.* Cases have been seen " of anencephalous 
 fcetuses, who cried and sucked a finger placed to their 
 lips. Beyer, being compelled once to open the head of 
 a foetus to accomplish a delivery, and having completely 
 emptied the skull, saw the foetus, some minutes after birth, 
 give a cry, breathe, and move its hands and feet." With 
 the higher animals, if we suppress the whole of the enceph- 
 alon that is to say, all the nervous centres with which 
 sensations and images, strictly so-called, are connected 
 the spinal marrow and bulb, which alone remain, are still 
 capable, under the stimulus of the sensitive nerves, of ex- 
 citing and combining movements with some object in view, 
 as happens with the posterior limbs of a frog or Triton. 
 
 * Vulpian, 396.
 
 OF MENTAL EVENTS. [BOOK IV. 
 
 The animal still cries, though without pain, when its paw is 
 pinched ; it swallows food when placed at the end of its 
 gullet ; it goes through all the movements of respiration. 
 In our own cases, sneezing, coughing, vomiting, are so 
 many systematically complex and useful movements, excited 
 without exercise of will on our parts, through the medium 
 of the bulb.* In general, given in an animal a segment of 
 spinal marrow, with the sensitive nerves terminating in it, 
 and the motor nerves springing from it, when the sensitive 
 nerves are excited, the segment, commencing to act, will 
 set to work the motor nerves, and we shall see muscular 
 contractions. This may be readily observed in eels, sala- 
 manders, and serpents. Landryf observed it in sucking 
 pigs, whose spinal marrow he divided into several segments, 
 while leaving the rest of the body intact. Animals thus 
 treated may live a long time, and while the circulation 
 subsists, " the reflex excitability of a separated portion of 
 the marrow may persist almost indefinitely;" it has been 
 seen to last three months, and even for more than a year. 
 
 . Every segment then is a sort of complete animal, capable 
 in itself of being excited and of reacting, capable even of liv- 
 ing in an isolated state, if, as is the case with the inferior an- 
 imals, and notably with the annelidae, the mutual dependence 
 of the segments is not too great.;}: We should never come 
 
 * Vulpian, 423. 
 
 f " Des Paralysies," 47. Experiments, 6, 7, 8. Vulpian, 432. 
 
 \ Landry, " Paralysies," 47. The spinal marrow may be divided perpendicu- 
 larly to its axis in two, three, four, or more segments, without inducing any modi- 
 fication of the phenomena in which it takes part. Each one of these parts, anatomi- 
 cally constituted like the whole organ, possesses separately the same faculties. I 
 have shown by experiments 9, 7, and 8, that a simple transversal section of the mar- 
 row, though it interrupts its continuity, leaves the reflex power, the excitability of 
 the nerves, the contractility and nutrition of the muscles, still subsisting, in all the 
 
 parts whose sensibility and movement are paralyzed Every segment of 
 
 the marrow then is a real centre of innervation Thus we may consider the 
 
 medullary cord as made up of a series of nervous centres with identical properties, 
 but affected nevertheless with different functions according to the different organs 
 
 with which the nerves springing from it are connected This would be in 
 
 accordance with comparative anatomy, which shows that the marrow becomes grad- 
 ually segmentary as we descend from the mammalia to fish, and from these to an- 
 imals still lower in the scale, to the Crustacea for instance. . . . ."
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. ^ 
 
 to an end if we attempted to enumerate all the cases of reflex 
 action. The majority of the muscular movements of animal 
 and of organic life, whether intermittent or continuous, are ac- 
 complished by it alone, so that we are obliged to consider all 
 the central parts of the nervous system, encephalon, bulb, spi- 
 nal marrow, as constantly set in action by the play of sensi- 
 tive nerves, in such a way as to excite the play of motor 
 nerves, with an accompaniment of sensations of which we are 
 or are not conscious. Whatever be the portion of the nerv- 
 ous system observed, we never see in it any other than reflex 
 actions ; they may be more or less complex, but are always 
 of the same kind. A white conducting cord conveys an ex- 
 citation to a central nucleus of gray substance ; a molecular 
 movement then arises in this substance, and thereupon an 
 excitation is carried on to the muscles by another white con- 
 ducting cord. These three movements so connected con- 
 stitute reflex action ; the gray substance, wherever it be, 
 in spinal marrow protuberance, or cerebral lobes, always acts 
 in the same way. 
 
 Now, in the protuberance and the cerebral lobes, its action 
 arouses mental events, all of the same kind ; temporary sen- 
 sations or reviving sensations. We must, then, admit that 
 its action excites everywhere mental events of an allied kind ; 
 and inasmuch as, even in the protuberance and lobes, the 
 greatest part of these events are imperceptible to conscious- 
 ness, there is nothing to prevent its action from arousing, in 
 the marrow, mental events analogous to sensation, but now 
 situated, by nature not by accident, beyond the reach of con- 
 sciousness. We should thus have three degrees in sensation. 
 In the highest degree, in the cerebral lobes, the sensation be- 
 comes capable of revival, and is termed an image. In the 
 next degree, in the protuberance, the sensation, incapable of 
 revival, remains simply crude. In the lowest degree, in the 
 marrow, it is in a still more incomplete state, and we cannot 
 now define it exactly from our having no consciousness of it, 
 but we recognize it correctly by this incapacity to appear, 
 and it probably resembles those elementary sensations which, 
 when separate, amount to nothing as far as consciousness is 
 concerned, and only make up an ordinary sensation by com-
 
 176 OF MENTAL EVENTS. [BOOK IV. 
 
 biningwith others to constitute a whole. So too there would 
 be three degrees of complication in the action of the nervous 
 centres. At the lowest degree, in the marrow would arise 
 fragmentary actions analogous perhaps to those which excite 
 elementary sensations, imperceptible to consciousness. In 
 the next degree, in the protuberance, these same actions com- 
 bine, when transmitted, into a total action exciting the ordi- 
 nary total sensation. In the highest degree, in the lobes, this 
 total action, transmitted a second time, is repeated indefinite- 
 ly by a series of mutually excitable cerebral elements, and 
 then excites those secondary and reviving sensations we term 
 images. We thus conceive, for the action of the nervous cen- 
 tres as for mental events, three stages of successive transmis- 
 sion and elaboration, and we can thus include in a general 
 view the reciprocal dependence and the development of the 
 two streams. 
 
 They form two long series, the one of which is the neces- 
 sary and sufficient condition of the other, and which corre- 
 pond as precisely as the convexity and concavity of the same 
 curve. On the one side are the molecular movements of the 
 nervous centres ; on the other are mental events, all more or 
 less analogous to sensation. The first invariably excite the 
 second, and the degree of complication found in the one series 
 always corresponds to an equal degree of complication in the 
 other. At a certain degree, the second series may be known 
 by a special inward process we term consciousness ; but, even 
 when at this degree, it generally happens that the events of 
 this series are not thus known.- Beneath those which con- 
 sciousness attains, there are many others to which it cannot at- 
 tain and which we are compelled to conceive on the type of 
 those we know, but on a reduced and fragmentary type, and 
 becoming more reduced and fragmentary as the nervous action 
 exciting them becomes more simple. Thus we see that, be- 
 neath the ordinary sensations which we know by conscious- 
 ness, there descends an indefinite series of analogous mental 
 events, more and more imperfect more and more removed from 
 consciousness, without our being able to put a limit to this se- 
 ries of increasing degradations ; and this successive lowering 
 which has its counterpart in the attenuation of the nervous
 
 CHAP. I.] FUNCTIONS OF THE NERVOUS CENTRES. ^7 
 
 system, leads us to the foot of the zoological scale, while con- 
 necting together, by a continuous sequence of intermediate 
 links, the most rudimentary outlines and highest combinations 
 of the nervous system and the mental world. 
 12
 
 OF MENTAL EVENTS. [BOOK IV. 
 
 CHAPTER II. 
 
 RELATION OF THE FUNCTIONS OF THE NERVOUS CENTRES 
 AND MENTAL EVENTS. 
 
 I. HERE we have the great question of the physical and 
 the moral world, two worlds which the most obvious expe- 
 rience shows to be inseparably connected together, and which 
 their representations show us as absolutely irreducible to 
 one another. On the one hand, we prove that the second 
 depends on the first ; on the other hand, we are unable to 
 conceive that it so depends. Physiologists, on the one hand, 
 willingly lose sight of the second fact, and tell us that " men- 
 tal events are a function of the nervous centres, just as mus- 
 cular contraction is a function of the muscles, and the se- 
 cretion of bile, a function of the liver." Philosophers, on the 
 other hand, willingly lose sight of the first fact, and tells us 
 that " mental events have nothing in common with the mo- 
 lecular movements of the nervous centres, and appertain to 
 a being of different nature." On this, cautious lookers-on 
 interpose and conclude that : " It is true that mental events 
 and the molecular movements of the nervous centres are in- 
 separably connected together ; it is true that as far as our 
 mind and powers of conception are concerned they are ab- 
 solutely irreducible to one another. We stop at this difficulty, 
 and will not even attempt to surmount it ; let us content 
 ourselves with ignorance." For our own parts, if we attempt 
 to make an advance into this obscurity, it is because we have 
 already made several advances. On the one hand, we have 
 seen that our most abstract ideas, being signs, are reduced 
 to images, that our images themselves are reviving sensations, 
 that consequently our whole entire thought is reduced to sen- 
 sations. The difficulty then is simplified, and it is now a 
 question only of comprehending the connection between a
 
 CHAP. II.] THE NERVOUS CENTRES AND THOUGHT. 
 
 179 
 
 molecular movement and a sensation. On the other hand, 
 we have seen that sensations, though apparently simple, are 
 wholes ; that these wholes, though apparently irreducible to 
 one another, may be composed of similar elements ; that at a 
 certain degree of simplicity these elements are no longer per- 
 ceived by consciousness ; that the sensation is then a com- 
 pound of rudimentary events, capable of indefinite degrada- 
 tions, incapable of coming within the grasp of consciousness, 
 but whose presence, and further, whose effectiveness is proved 
 by reflex actions. The difficulty is thus simplified a second 
 time ; it is now a question only of comprehending the con- 
 nection between these events and a molecular movement. 
 The obscurity still remains very great ; for we can never 
 conceive these events otherwise than after the type of ordi- 
 nary sensations, and between this conception and that of a 
 movement is still a gulf. But we know that ordinary sensation 
 is a compound, that it differs from its elements, that these ele- 
 ments escape our consciousness, that they are none the less 
 real and active, and, in this deep lower twilight whence the 
 sensation arises, we shall perhaps discover the link between 
 the physical and the moral world. 
 
 II. Let us begin by stating the difficulty in all its force. 
 Since mental events are nothing more than sensations more 
 or less twisted and transformed, let us compare a sensation 
 with a molecular movement of the nervous centres. Let us 
 take the sensation of golden yellow, that of a musical note 
 like lit, that given by the emanations of a lily, by the taste of 
 sugar, by the pain of a cut, by tickling, by heat or cold. The 
 necessary and sufficient condition of such a sensation, is an 
 internal movement in the gray substance of the protuberance 
 of the corpora quadrigemina, in short, of a centre of sensation ; 
 this movement may be unknown, it matters little ; whatever 
 it may be, it consists of a more or less complex and extensive 
 displacement of molecules, and is nothing more. Now, what 
 relationship can we imagine between this displacement and a 
 sensation ? Cells, constituted of a membrane and one or 
 more nuclei, are strewed in a granulated substance, a kind of 
 flabby pulp or grayish jelly, made up of nuclei and of innume- 
 rable fibres ; these cells ramify into slender prolongations,
 
 l8o OF MENTAL EVENTS. [BOOK IV. 
 
 which probably connect themselves with the nervous fibres, 
 and it is supposed that they thereby communicate with one 
 another, and with the white conductive parts. Study as 
 closely as you will the anatomical preparations and micro- 
 graphic plates which show us this apparatus ; suppose the 
 power of the microscope indefinitely increased, and the en- 
 largement carried to a million or a thousand million diameters. 
 Suppose physiology at maturity, and the theory of cellular 
 movements as far advanced as the physical theory of undula- 
 tions ; suppose we knew the mechanism of the movement 
 produced in the gray substance during a sensation, its circuit 
 from cell to cell, its differences according as it excites a sen- 
 sation of sound or of smell, the link connecting it with move- 
 ments of heat or electricity, and further, the mechanical for- 
 mula which respects the mass, velocity, and position of all 
 the elements of the fibres and the cells at any time of their 
 movement. We should even then have movement only, 
 and movement, of whatever kind it be, rotatory, undulatory, 
 or what else, has no resemblance at all to a sensation of bit- 
 ter, of yellow, of cold, or of pain. We cannot convert either 
 of these two conceptions into the other, and consequently 
 the two events seem to be of absolutely different quality ; so 
 that analysis, instead of filling up the interval between them, 
 seems to enlarge it to an infinite extent.* 
 
 * Cf. the following extract from Professor Tyndall's Address to the British 
 Association for the Advancement of Science, on " The Physical Forces and 
 Thought." 
 
 " I can hardly imagine that any profound scientific thinker, who has reflected 
 upon the subject, exists who would not admit the extreme probability of the hy- 
 pothesis, that for every fact of consciousness, whether in the domain of sense, of 
 thought, or of emotion, a certain definite molecular condition is set up in the 
 brain ; that this relation of physics to consciousness is invariable, so that, given 
 the state of the brain, the corresponding thought or feeling might be inferred ; or 
 given the thought or feeling, the corresponding state of the brain might be inferred. 
 But how inferred ? It is at bottom not a case of logical inference at all, but of 
 empirical association. You may reply that many of the inferences of science are of 
 this character ; the inference, for example, that an electric current of a given di- 
 rection will deflect a magnetic needle in a definite way ; but the cases differ in 
 this, that the passage from the current to the needle, if not demonstrable, is think- 
 able, and that we entertain no doubt as to the final mechanical solution of the 
 problem ; but the passage from the physics of the brain to the corresponding facts
 
 . II.] THE NERVOUS CENTRES AND THOUGHTS. jgi 
 
 III. Repulsed in this direction, we must turn to another. 
 It is true that we cannot conceive the two events otherwise 
 than as irreducible to one another ; but that may depend on 
 the way in which we conceive them and not on their actual 
 qualities ; their incompatibility is perhaps rather apparent 
 than real ; it arises on our side and not on theirs. There 
 would be nothing extraordinary in such an illusion as this. 
 As a general rule it is sufficient for a fact to be known to us 
 in two different ways, for us to conceive, in its, place, two dif- 
 ferent facts. 
 
 Such is the case with the objects we know by the senses. 
 A person born blind* who has just been couched, remains for 
 a considerable time unable to reconcile his perceptions of 
 touch with those of sight. Before the operation, he represented 
 to himself a china cup as cold, polished, and capable of af- 
 fording to the hand certain sensations of resistance, weight, 
 and form ; when he sees it for the first time, and it gives him 
 the sensation of a white patch, he conceives the white lus- 
 trous object as something different from the resisting, heavy, 
 cold, polished object. He would stop at this, if he did not 
 acquire new experiences ; the two things would always be dif 
 ferent in quality ; they would form two worlds, between which 
 there would be no communication. And so, if your eyes are 
 
 of consciousness is unthinkable. Granted that a definite thought, and a definite 
 molecular action in the brain occur simultaneously ; we do not possess the intel- 
 lectual organ, nor apparently any rudiment of the organ, which would enable us 
 to pass by a process of reasoning from the one phenomenon to the other. They 
 appear together, but we do not know why. Were our minds and senses so ex- 
 panded, strengthened, and illuminated as to enable us to see and feel the very 
 molecules of the brain ; were we capable of following all their motions, all their 
 all their electric discharges, if such there be ; and were we intimately acquainted 
 with the corresponding states of thought and feeling, we should be as far as ever 
 from the solution of the problem, ' How are these physical processes connected 
 with the facts of consciousness ? The chasm between the two classes of phenomena 
 would still remain intellectually impassable. Let the consciousness of love, for 
 example, be associated with a right-handed spiral motion of the molecules of the 
 brain, and the consciousness of hate with a left -handed spiral motion. We should 
 then know when love that the motion is in one direction, and when we hate that 
 the motion is in the other; but the 'WHY?' would still remain unanswered." 
 See Report xxxviii. for the year 1868. Transactions of the Sections, p. 5. 
 * See post, Part II. book ii. chap. ii.
 
 1 82 OF MENTAL EVENTS. [BooK IV. 
 
 shut and you are not aware of what is going to happen, and 
 you see a flash, then hear a sound, and then feel as if hit on 
 the arm with a stick (the experiment may be tried on a child 
 or an ignorant person), you will imagine that you have been 
 struck, that some one has whistled, and that a bright light 
 has shone into the room ; and yet the three different facts 
 are but one, the passage of a current of electricity. The 
 science of acoustics had to be constructed to show that the 
 event which arouses in us, through the tactile nerves, sensa- 
 tions of vibration and tickling, is the same as that which, through 
 the acoustic nerves, gives rise to sensations of sound. Till 
 very recently " phenomena of heat,* electricity, light, ill-de- 
 fined enough in themselves, were thought to be produced by 
 so many peculiar agents, fluids possessed of special activities. 
 A closer examination has enabled us to recognize that this 
 conception of different specific heterogeneous elements has 
 for foundation one single reason namely, that the percep- 
 tion of these different orders of phenomena takes effect in 
 general through different organs, and by thus attaching 
 themselves more specially to some one of our senses, they 
 necessarily excite special sensations. The apparent heter- 
 ogeneity then would be not so much in the nature of the 
 physical agent as in the functions of the physiological instru- 
 ment by which the sensations are effected ; so that by trans- 
 ferring, by an erroneous attribution, these differences of ap- 
 pearance from the effect to the cause, we should in reality 
 have classified the intermediate phenomena by which we 
 have cognizance of the modifications of matter, rather than by 
 the very essence of these modifications All physical phe- 
 nomena, whatever be their nature, seem to be at foundation 
 nothing more than the manifestations of one and the same 
 primordial agent." Thus, the conception we form bears in- 
 variably a deep imprint of the process forming it. We are 
 compelled then to take count of this imprint ; and therefore, 
 when we find within us two ideas which have entered by 
 different routes, we ought to mistrust the tendency which in- 
 
 * M. de Senarmont. From a Lecture at the Ecole Polytechnique, cited by 
 Saigey. " La Physique Moderne," p, 216.
 
 CHAP. II.] THE NERVOUS CENTRES AND THOUGHTS. i^ 
 
 duces us to assert a difference, and above all an absolute dif- 
 ference, between their objects. 
 
 Now when we examine closely the idea of a sensation 
 and the idea of a molecular movement of the nervous centres, 
 we find that they enter by routes not merely different, but 
 contrary. The first comes from within, without any inter- 
 mediate ; the second comes from without, through several 
 intermediates. To represent to one's self a sensation is to 
 have present an image of that sensation, that is to say, the 
 sensation itself directly repeated and spontaneously reviving. 
 To represent a molecular movement of the nervous centres is 
 to have present images of the tactile, visual, and other sensa- 
 tions, which it would excite in us if it were acting on our 
 senses from without, that is to say, to imagine sensations of 
 white, of gray, of flabby consistency, of cellular or fibrous 
 form, of small quivering points, that is, in fact, if we go furth- 
 er, to combine internally the names of movement, velocity, 
 and mass, which denote collections and extracts of muscular 
 and tactile sensations. On the whole, the first representa- 
 tion is equivalent to its object, the second to the group of 
 sensations which its object would excite in us. Now we 
 cannot conceive more dissimilar processes of formation. In 
 the case, just now, of different senses, the two representations 
 reached us by two different roads, but both were external, 
 so that there was nothing to prevent their having some 
 common starting-point. Here, the two representations 
 reach us by two opposite roads, one from within, the other 
 from without, in such a way that these roads are perpetually 
 divergent, and that we are unable to conceive their having 
 the same starting-point. Thus the fundamental opposition 
 of the two processes of formation is sufficient to explain the 
 mutual irreducibility of the two representations. One and 
 the same single event known in these two ways will appear 
 double, and, whatever be the link which experience establishes 
 between its two manifestations, we shall never be able to con- 
 vert one of them into the other. According as its represen- 
 tation comes from without or within, it will invariably appear 
 as a thing without, or within, and we shall never be able to 
 reduce that which is without to that which is within, or that 
 which is within to that which is without.
 
 184 OF MENTAL EVENTS. [BooK IV 
 
 IV. It is possible then that the sensation and the internal 
 movement of the nervous centres may be at bottom one and 
 the same unique event, condemned, by the two ways in which 
 it is known, always and irremediably to appear double. 
 Another line of reasoning leads to a similar conclusion. In 
 fact, we have seen that our sensations are but wholes, com- 
 posed of elementary sensations, that these are similarly com- 
 posed, and so on ; that at each of these degrees of composi- 
 tion the compound presents itself to us with qualities wholly 
 different from those of its elements, that consequently, the 
 more simple the elements, and the more removed from the 
 grasp of consciousness, the more must they differ, as far as 
 we are concerned, from the whole which is accessible to con- 
 sciousness, in such a way that the aspect of the infinitesimal 
 elements at the foot of the scale, and that of the whole sensa- 
 tion at the summit of the scale, must be wholly and entirely 
 different. Now such is the aspect of the molecular move- 
 ments when compared with that of the entire sensation. Con- 
 sequently, there is nothing to prevent the molecular move- 
 ments from being the infinitesimal elements of the whole sen- 
 sation. Thus, the fundamental objection is removed.* If our 
 conceptions of the mental and of the cerebral event are irre- 
 ducible to one another, it may doubtless depend on the two 
 events being, in fact, irreducible to one another ; but it may 
 also depend, first, on the event which is single, being known 
 to us in two directly contrary ways, and, next, on the mental 
 event and its ultimate elements being forcedly presented to 
 us under absolutely opposite aspects. 
 
 There is room then, and equal room, for the two hypo- 
 theses, for that of two heterogeneous events, and for that of 
 one and the same event known under two different aspects. 
 Which must we choose? If we adopt the first we are con- 
 fronted with a link, not only unexplained, but inexplicable. 
 For, the two events being by nature irreducible to one anoth- 
 er, form two worlds, apart and isolated ; we exclude by hy- 
 pothesis any more general event of which they might be but 
 distinct forms and particular cases ; we declare beforehand 
 that their nature furnishes nothing on which their reciprocal 
 dependence may be founded. We are compelled, then, in
 
 CHAP. II.] THE NERVOUS CENTRES AND THOUGHTS. X g5 
 
 order to explain this dependence, to seek for it in something 
 above their nature, and therefore above all nature, for they, 
 between them, make up all nature, consequently, then, in the 
 supernatural. So that we must call in aid a miracle, the in- 
 tervention of a superior being. The philosophers of the sev- 
 enteenth century, Leibnitz and Malebranche at their head, 
 clearly saw this consequence, and boldly decided that there 
 was a pre-established harmony, the artificial agreement of 
 two independent clocks, an extrinsic adjustment descending 
 from on high, a special decree of God. Nothing could be less 
 conformable to the methods of scientific induction : which ex- 
 clude all hypotheses by which is nothing explained. We are 
 driven back then to the second supposition. And, first, it is 
 in itself as plausible as the other. Again, it has analogies 
 and numerous precedents in its favor ; for, like so many other 
 physical and psychological theories, it takes into consideration 
 the influence of the percipient and sentient subject, the struct- 
 ure of the observing instrument, the effects of optics. Besides 
 this, it calls in no third cause, no imaginary or unknown prop- 
 erty ; it is as little hypothetical as possible. Finally, it shows 
 not only that the two events may be connected with one anoth- 
 er, but that they must always and necessarily be so connected, 
 For, from the moment they are reduced to one single fact, 
 possessed of two aspects, they evidently become like the front 
 and reverse side of a surface, so that the presence or absence 
 of the one will infallibly result in the presence or absence of 
 the other. We are entitled then to admit that the cerebral 
 event and the mental event are, at foundation, but one and 
 the same event under two aspects, one moral, the other phys- 
 ical, one accessible to consciousness, the other accessible to 
 the senses. 
 
 Now of the two ways in which we attain to this event, 
 the one, consciousness, is direct ; to know a sensation by con- 
 sciousness, is to have present its image, which is the same 
 sensation revived. The other way, on the contrary, that is 
 external perception, is indirect ; it teaches us nothing as to 
 the special characters of its object ; it simply informs us of a 
 certain class of its effects. The object is not directly mani- 
 fested to us it is denoted indirectly by the group of sensations
 
 1 86 OF MENTAL EVENTS. [BOOK IV. 
 
 it arouses, or would arouse in us.* In itself, excepting as to 
 character we shall examine later on, this physical and sensible 
 object remains wholly unknown to us ; all we know respecting 
 it, is the group of sensations it excites in us. All we know of 
 the cerebral molecules, are the sensations of grayish color, of 
 flabby consistance, of form, volume, and other analogous ones, 
 which these molecules excite in us, directly or through the 
 microscope, in a crude state or after preparation that is to 
 say, their constant effects upon us, the fixed accompaniments, 
 their signs, nothing but their signs, signs and indications of 
 unknown things. There is, then, a great difference between 
 the two aspects. By consciousness, I attain the fact itself; 
 by the senses, I attain a sign only. A sign of what ? What 
 is it that is constantly accompanied, denoted, signified by the 
 internal movement of the nervous centres ? We have shewn 
 this previously when explaining the conditions of sensations 
 and images ; it is the sensation, the image, the internal men- 
 tal event. All is then.in accordance. This mental event, which 
 consciousness attains directly, can only be attained indirectly 
 by the senses ; the senses know nothing of it but its effect on 
 them; that is why they cause us to conceive it as a cerebral 
 movement of gray cells ; as it acts on them from without only, 
 it cannot appear to them otherwise than as external and 
 physical. Here is a direct and remarkable confirmation of 
 the admitted hypothesis, and we now understand how it is 
 the mental event being single, necessarily appears double ; 
 the sign and the event signified are two things which can no 
 more be confounded than separated, and their distinction is 
 as necessary as their connection. But, in this connection and 
 in this distinction, all the advantage is on the side of the 
 mental event ; it alone exists ; the physical event is but the 
 way in which it affects or is capable of affecting our senses. 
 The physical world, then is reduced to a system of signs, and 
 all that remains to enable us to construct and conceive it are 
 the materials of the moral world. 
 
 * See post Part ii. book 5i. chaps, i and 2. See too, the admirable chapters on 
 the Theory of the Belief in an External World and on the Primary Qualities of 
 of Matter, in Mill's " Examination of Sir W. Hamilton's Philosophy. "
 
 CHAP. II.] THE NERVOUS CENTRES AND THOUGHTS. jg/ 
 
 What are these materials ? We have seen that the sen- 
 sation, strictly so called, is a compound of successive and simul- 
 taneous events of the same quality, themselves composed in 
 the same way ; that at the extremity of our analysis, indirect 
 experience and analogies still show successive and simultaneous 
 events of the same quality, all remote from consciousness 
 and becoming at last infinitesimal ; that reflex actions indicate 
 analogous rudimentary events, and that these may be traced 
 even at the lowest point of the animal scale, even in animals 
 like the fresh-water polypus in which no trace of a nervous 
 system has been found.* But they may be traced still further 
 than this ; for, in many plants like the sensitive plant and the 
 oscillating clover of Bengal, in the antherozoides, of cryp- 
 togamia and the zoospores of the algae, reflex actions are 
 met with wholly similar to those produced by the trunk of a 
 decapitated frog. " There is no radical difference between 
 animals and vegetables," when looked at in this light. No 
 more again is there when looked at in the light of internal 
 structure, or of chemical composition. The two kingdoms 
 are so confounded together in their lower branches, that many 
 groups, among others the Vibriae, have sometimes been class- 
 ified in the one, sometimes in the other. In fact, " the nervous 
 system is but a perfectioned apparatus," and the mental event 
 of which it is the condition, and of which its action is the sign 
 is a complex and organized group whose elements and rudi- 
 ments may also be met with elsewhere. By pursuing analogies 
 then, we may descend still lower in the scale of beings. Be- 
 neath the organic world extends tbe inorganic, and the first 
 is but a case of the second. It is constructed with the same 
 chemical substances, subject to the same physical forces, gov- 
 erned by the same mechanical laws, and all the indications of 
 science concur in representing it as differing in degree but 
 identical in nature ;f what we term life is a more delicate 
 chemical action of more complex chemical elements. In 
 pursuing our analysis, from the highest operations of the 
 
 * Vulpian, 43, 3?, 31. 
 
 \ Bertholet, " Chimie Organique. " ii. conclusion Berard. " Elements de 
 Physiologic," ii. 65. Saigey, " De 1'Unite des Phenomenes Physiques," passim.
 
 1 88 OF MENTAL EVENTS. [BOOK IV. 
 
 cerebral lobes to the most elementary phenomena of physics, 
 we find nothing but mechanical movements of atoms, trans- 
 missible without loss from one system to another, and so much 
 the more complicated as the systems become more complex. 
 By correspondence, the same degradation and the same redac- 
 tion occur in mental events ; at the highest degree of compli- 
 cation, they constitute images, sensations, strictly so called, 
 and those rudimentary sensations which reflex action denotes ; 
 in the next degrees, they are still events of the same kind, but 
 less compound, and so on, their complication diminishing 
 with that of the molecular movement, till at last, to the most 
 simple degree of the physical event, corresponds the most 
 simple degree of the mental event. 
 
 V. Nature, then, has two faces, and the successive and 
 simultaneous events of which she is made up may be conceived 
 and known in two ways, internally and in themselves, exter- 
 nally and by the impression they make on our senses. The 
 two faces are parallel, and every line cutting the one cuts the 
 other at the same level. When seen from the one side, na- 
 ture has, as elements, events of which we can know nothing 
 except when in a state of extreme complication, and which, in 
 this state, we term sensations. Seen from the other side, she 
 has, as elements, events which we can only conceive clearly 
 when in a state of extreme simplicity, and which, in this state, 
 we term molecular movements. From the first point, she is 
 a scale of successive and simultaneous mental events,' whose 
 complication goes on decreasing, if we start from the summit 
 of which we are conscious, to descend to the base of which 
 we are unconscious. From the second point, she is a scale 
 of successive and simultaneous physical events, whose compli- 
 cation goes on increasing, if we start from the base which we 
 clearly conceive, to ascend to the summit of which we have 
 no precise idea. Every degree of complication on one side 
 of the scale indicates an equal degree of complication on the 
 other. On both sides, at the base of the scale the events are 
 infinitesimal ; we have seen in the case of those sensations 
 which we have been able to a certain extent to analyze, those 
 of hearing and sight, that the mental event, as the physical 
 event, passes in a very short time through a strictly infinite
 
 CHAP. II.] THE NERVOUS CENTRES AND THOUGHTS. 
 
 series of degrees. From base to summit, the correspondence 
 on either side is perfect. Phrase for phrase, word for word, 
 the physical event, as we represent it to ourselves, translates 
 the mental event. 
 
 Let the reader follow out the comparison to the end ; it 
 will express the matter with all its details. Suppose a book 
 written in an original tongue and furnished with an interlinear 
 translation ; the book is nature, the original language is the 
 mental event, the interlinear translation is the physical event, 
 and the order of the chapters is the order of beings. At the 
 beginning of the book, the translations is printed in clear and 
 legible characters. But these become less so, as we go on, 
 and here and there, from chapter to chapter, new characters 
 creep in, which we have difficulty in connecting with the 
 earlier ones. At last, and above all in the final chapter, the 
 impression can no longer be deciphered ; but we have abun- 
 dance of evidence that it is still the same book and the same 
 language. It is just the reverse with the original text. It is 
 very legible at the last chapter ; in the one before it the ink 
 is pale ; in earlier chapters we can still discover that there is 
 printing, but can read nothing of it ; before that again, all 
 trace of ink has disappeared. 
 
 Such is the book philosophers attempt to understand ; 
 before the final unintelligibility of the first writing, and before 
 the enormous gaps of the second, they stop embarrassed 
 and each one decides, not from the facts in evidence but 
 from the habits of his mind and the wants of his heart. 
 Scientific men properly so called, physicists and physiologists 
 who have begun the book at the beginning, say that it con- 
 tains but one language, that of the interlinear translation, 
 and that the other is reducible to it ; an enormous supposi- 
 tion, since the two languages are wholly different. Moralists, 
 psychologists, and religious minds who have commenced the 
 book at the end, and are nevertheless forced to confess that 
 the bulk of the work is written in another idiom, find an in- 
 explicable mystery in this assemblage of two languages, and 
 usually declare that there are two books put in juxtaposition 
 and beside one another. In short, materialists disallow the 
 text, and spiritualists declare the connection of text and
 
 I OX) OF MENTAL EVENTS. [BOOK IV. 
 
 translation to be inexplicable. We have not proceeded 
 in this way, and our minute analysis has led us to a new 
 solution. We have first studied for a long time the orig- 
 inal idiom, and have shown that the pages of the last chap- 
 ter, which appear to be written in various kinds of characters, 
 are all written in the same character. Profiting by this re- 
 duction, we have then deciphered many half-obliterated lines 
 of the chapter preceeding it ; then, from the vague traces 
 left on the earlier pages, we have conjectured that the text 
 is continued much further back, even on those pages on 
 which no trace of it is visible. We then prove the interlinear 
 writing to be a translation, and the other to be an original 
 text ; and have concluded, from their dependence, that the 
 first is the translation of the second. On this evidence we 
 have admitted that the text, though invisible to our eyes, 
 must be continued on the earlier pages, and that, on the final 
 pages, the interlinear writing, though it cannot be deciphered 
 is still a translation. In this way, the unity of the book has 
 been proved, and the two idioms are completed or explained 
 by one another. We now know which of them is the origin- 
 al testimony and deserves our confidence, and to what ex- 
 tent and with what assurance we may consult the other. 
 Thanks to their mutual dependence and to the continual 
 presence of one or other of them, each of them may supply 
 the place of the other. When one of them is effaced or in- 
 capable of being deciphered, we are entitled to draw conclu- 
 sions, from the one we can read, to the other which has be- 
 come unreadable.* 
 
 * To complete this theory, seefost, note at the end of sect, vii, ihap. i,book 
 ii. part ii.
 
 CuAP. III.] SELF AND THE ORGANIZED BODY. 
 
 CHAPTER III. 
 
 THE HUMAN PERSON AND THE PHYSIOLOGICAL INDIVIDUAL. 
 
 I. HITHERTO we have considered our events, without oc- 
 cupying ourselves with the being they appertain to, and which 
 each of us calls himself. We must now examine this being. 
 Philosophers usually give, it the principle place, and a place, 
 wholly distinct. " I experience sensation, say they, I have 
 recollections, I combine images and ideas, I perceive and 
 conceive external objects. This Ego or self, unique, per- 
 sistent, and always the same, is something different from 
 my sensations, recollections, images, ideas, perceptions, and 
 conceptions, which are various and transient. Besides this, 
 it is capable of experiencing some of these and of produc- 
 ing the rest ; and thus it possesses powers or faculties. 
 Now these faculties reside in it in a stable manner ; by them 
 it feels, recollects, perceives, conceives, combines images and 
 ideas ; it is, then, an efficient and productive cause." Thus 
 they arrive at considering the Ego as a subject or substance, 
 having for its distinctive qualities certain faculties, and they 
 suppose that, beneath our mental events, there are two kinds 
 of explicative entities, first the powers or faculties experienc- 
 ing or producing them, then the subject, substance, or soul 
 possessing these faculties.* 
 
 Now these are metaphysical entities, pure phantoms, be- 
 gotten of words, and vanishing as soon as we examine rigor- 
 ously the meanings of the words. What is a power ? A des- 
 potic sovereign has absolute power ; this means that, as soon 
 as he commands a thing to be done, whatever it may be, the 
 confiscation of property, the death of a man, it will be done. 
 A constitutional king has limited power only ; this means 
 
 * Gamier, " Traite des facultes de Tame," vol. i. books i. and ii. See Jouffiroy 
 and Maine de Biran for the theory of these scholastic entities.
 
 I 02 OF MENTAL EVENTS. [BOOK IV. 
 
 that if he commands certain things, the dismissal of a minis- 
 ter, the promulgation of a law, they will be done ; but that, 
 if he orders other things, such things, for instance, as we men- 
 tioned just now, they will not be done; this is all that is 
 meant. All that the word power here denotes is a constant 
 connection between one fact, the order of a prince, and cer- 
 tain other facts following it. And so again we say that a 
 healthy man has power to walk and a paralytic man has not ; 
 this simply means to say that, in the healthy man, the resolu- 
 tion to walk is certainly followed by the movement of his legs, 
 and this resolution is never so followed in the case of the par- 
 alytic ; here again power is but the perpetual connection be- 
 tween one fact which is antecedent and another which is 
 consequent. 
 
 So again with force. A particular horse has force enough 
 to draw a cart weighing five thousand kilogrammes, and has 
 not force enough to draw the same cart when more heavily 
 loaded. A particular stream of water has force enough to 
 move a wheel, and has not force enough to move a heavier 
 wheel. This means that, when the horse's muscles are con- 
 tracted, the cart of five thousand kilogrammes will be moved, 
 and the other cart will not be moved : that when the stream 
 falls on the boards of the wheels, the first one will turn and 
 the second one will not. Here we have connections only, 
 one between the muscular contractions of the horse and the 
 movement of the cart ; the other between the stream of water 
 and the wheel turning round. A particular force exists when 
 a particular connection exists ; it ceases when this connection 
 ceases. When two events are connected, and the second of 
 them has a particular magnitude when compared to others 
 similar to it, we say that the force has a particular magnitude. 
 When the magnitude of the second event is double, the mag- 
 nitude of the force is double. The force of the muscular con- 
 traction is double, if the cart moved weighs ten thousand 
 kilogrammes instead of five thousand ; the force of the stream 
 of water is double, if the wheel set turning is twice as heavy 
 as the first wheel. In general, if we are given two facts, 
 one antecedent and the other consequent, connected by a 
 constant link, we term the particularity of the antecedent to
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. JQ-I 
 
 be always followed by the consequent, force, and we measure 
 this force by the magnitude of the consequent. 
 
 The names power and force, then, do not denote any mys- 
 terious being, any occult essence. When I say that I have 
 power or force to move my arm, I merely wish to say that 
 my resolution to move my arm is constantly followed by the 
 movement of my arm. In fact, if, with the aid of physiology, 
 I examine this operation somewhat more closely, I find in it 
 a number of intermediate steps a molecular movement in 
 cerebral lobes, another molecular movement in the cerebellum, 
 another molecular movement propagated along the marrow, 
 and thence into the motor nerves of the arm, a contraction 
 of the muscles of the arm, a displacement of their points of 
 attachment. I have power to move my arm in the same sense 
 that a person working the telegraph at Marseilles has power 
 to move the telegraph needles at Paris. Between my resolu- 
 tion and the displacement of my arm, there are all the inter- 
 mediate steps enumerated ; between the operator at Marseilles 
 and the needles at Paris, there are a thousand kilometres of 
 telegraph wire. It is a constant particularity that the signals 
 of the worker are followed a thousand kilometres off by the 
 play of the indicating needles ; it is a constant particularity 
 that my resolution is followed, through ten indispensable in- 
 termediate links, by the movement of my arm. There is 
 nothing more than this. Unfortunately, of this particularity, 
 which is a relation, we construct, by a mental fiction, a sub- 
 stance ; we describe it by a substantive name, force or power ; 
 we attribute qualites to it ; we say that it is greater or less ; 
 we employ it in language as a subject ; we forget that its ex- 
 istence is wholly verbal, that it derives it from ourselves, that 
 it has received it by way of loan, provisionally, for conveni- 
 ence of discourse, and that, being simply a relation, it is noth- 
 ing in itself. Led away by language and custom, we suppose 
 there is something real in it, and reasoning from false premis- 
 es, increase our error at every step. In the first place, as the 
 being in question is a pure nonentity, we can find nothing in 
 it but emptiness ; this is why, by an illusion of which we have 
 already seen instances,* we make of it a pure essence, unex- 
 
 13 * See ante, book i. chap. 3, p. 33.
 
 104 OF MENTAL EVENTS. [BOOK IV. 
 
 tended, incorporeal, in short, spiritual.* In the second place, 
 as the event only arises through this force, the event is want- 
 ing if the force is wanting ; the force is the cause of the event. 
 Besides this, it precedes and survives the event ; it is per- 
 manent while the event is transient ; the event may be repeat- 
 ed or changed, the force is always one and the same ; it may 
 be compared to an inexhaustible stream, of which the event 
 is a wave. Hence we come to consider it as an essence of a 
 higher order, placed above the facts, stable, monadic, creative. 
 From its model, philosophers go on to people the universe 
 with similar entities. And yet, it is in itself nothing more 
 than a character, a property, a particularity of a fact, the par- 
 ticularity of being always followed by another fact, a particu- 
 larity detached from the fact by abstraction, set apart by fiction, 
 kept in a distinct state by means of a distinct substantive 
 name, till the mind, forgetting its origin, believes it to be in- 
 dependent, and becomes the dupe of an illusion of its own ef- 
 fecting. 
 
 II. The fall of this illusion causes the fall of another. 
 " Power," say the spiritualists, " identifies itself with the being 
 
 possessing it That something by which we can ought 
 
 not to be considered as distinct from the soul."f The facul- 
 ties and forces of the Ego, then, are Ego itself, or at least a 
 portion of the Ego ; many spiritualists go so far as to admit, 
 with Leibnitz, that the Ego, is nothing more than a force, 
 and that in general the notions of force and substance are 
 equivalent. Now we have just seen that powers and forces 
 are but verbal entities and metaphysical phantoms. So far, 
 therefore, as it is made up of forces and powers, the Ego it- 
 self ?s but a verbal entity and a metaphysical phantom. That 
 inner something of which the faculties were different aspects, 
 disappeared with them ; the one permanent substance, dis- 
 
 * " Causes are not material ; their activities are necessarily immaterial. Forces 
 seize on matter, conform it to themselves and manifest themselves by their effects 
 on its surface, they are signified and interpreted by the qualities they impose on 
 
 matter The real cause which sets in motion the heart, the stomach, and 
 
 other organs, is external and superior to those organs." Jouffroy, " Esthetique," 
 132, 145 ; " Nonveaux Melanges," 233 to 273. 
 
 f Gamier," Traite des faculties de Tame," i. 44.
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. ^ 
 
 tinct from events, is seen to vanish and re-enter the region 
 of words. All that remains of us are our events, sensations, 
 images, recollections, ideas, resolutions : these are what con- 
 stitute our being ; and the analysis of our most elementary 
 judgments shows, in fact, that our Self has no other ele- 
 ments. 
 
 Take a sensation of taste, then a pain in the leg, then the 
 recollection of a concert. I taste, I suffer, I recollect. In all 
 these words we find the verb to be, and all these judgments 
 contain the subject / connected by the verb to be, with a par- 
 ticiple denoting an attribute. Now, in every judgment, the 
 verb is expresses that the attribute is an element, a fragment, 
 an extract of the subject, included in it, as a portion in a 
 whole; this is the whole sense and office of the verb to be; 
 and it is the same with it here as in other cases. Here, then, 
 the verb expresses that the sensation of taste, the pain, the 
 recollection of the concert, are elements, fragments, extracts, 
 of the Ego. Our successive events then are successive com- 
 ponents of ourselves. The Ego is in turn each of these 
 events. At one moment, as was clearly seen by Condillac, it 
 is nothing more than the sensation of taste, at the second, 
 moment, nothing more than suffering, at the third, nothing 
 more than the recollection of the concert. Not that it is a 
 simple whole ; for the verb is, which connects the subject to 
 the attribute, expresses, not only that the attribute is included 
 in the subject as a portion in a whole, but further, that the 
 existence of the whole precedes its division. Whatever be 
 the origin of a judgment, the attribute is always, in relation 
 to the subject, an artificial fragment in relation to a natural 
 whole. The mind extracts the fragment, but, at the same 
 moment, recognizes that this extraction or abstraction is 
 purely fictitious, and that, if the fragment exists apart, it is 
 from the mind's having set it apart. In fact, it is simply for 
 the convenience of studying them that we separate our events 
 from one another ; they actually form a continuous web in 
 which our inspection sets boundaries by arbitrary severings.* 
 The operation we perform resembles that of a man who the 
 
 * " Les Philosophes Francais du xixme Siecle," par H. Taine, 3rd ed. p. 250.
 
 jgg OF MENTAL EVENTS. fBoOK IV. 
 
 better to know a long plank divides it into triangles, rhom- 
 boids, and squares, all marked out with chalk. The plank 
 remains one and continuous; we cannot say that it is simply 
 the series of its portions placed end to end, since it is only 
 divided to the eye ; but still it is equivalent to the series of 
 these portions ; if they were taken away, nothing would re- 
 main ; they constitute it. In the same way the Ego remains 
 one and continuous ; we cannot say that it is the series of its 
 events placed in succession, since it is not divided into events 
 except to observation ; but still it is equivalent to the series 
 of these events ; if they were taken away, nothing would re- 
 main ; they constitute it. When we separate them from it, 
 we do as a man would who should say, after going over the 
 several divisions of the plank, " This plank is a square here, 
 just now it was a rhomboid, presently it will be a triangle; 
 through all my advancing, retreating, recalling the past, foresee- 
 ing the future, I always find an invariable, identical single 
 plank, though its divisions vary ; it then is different from them, 
 it is a distinct subsisting being, that is to say, an independent 
 substance of which the rhomboids, triangles, and squares are 
 but successive states." By an optical illusion, such a man 
 would create an empty substance the plank in itself. By a 
 similar illusion, we create an empty substance the Ego in 
 itself. Just as the plank is nothing more than the continuous 
 series of its successive divisions, so, the Ego is nothing more 
 than the continuous web of its successive events. If we con- 
 sider it at a given moment, it is nothing more than a portion 
 severed from the web, that is to say, a group of simultaneous 
 events, about to be made up and then undone, some salient 
 sensation among other less salient ones, some preponderant 
 image among others about to fade away. At any other mo- 
 ment, the portion severed is analogous ; it is no other and no 
 more than this. 
 
 If now we classify these various events, sensations, 
 images, ideas, resolutions; if we impose a name on each 
 class, sensibility, imagination, understanding, will ; if we at- 
 tribute to the Ego various powers, that of feeling, that of 
 imagining, that of willing ; this is permissible and useful. 
 But we must never forget what underlies these words ; we
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. ^7 
 
 mean simply to say that this being feels, imagines, thinks, 
 wills, and that, if things remain the same, it will feel, imagine, 
 think, and will. When we outstep this vague proposition, 
 we mean to say that, certain conditions being given, this be- 
 ing will have a certain sensation, image, idea, or resolution, 
 in other words, that in the web constituting it there is a con- 
 stant connection with some event internal or external. I 
 have the power of recalling a picture, the Marriage at Cana 
 by Veronese ; this means that my present time of life, and 
 with my present memory, the resolution to recall the picture 
 is constantly followed, after the lapse of a certain time, by 
 the internal revival, more or less clear and complete, of the 
 figures and architecture of which the picture is composed. I 
 have the faculty of perceiving an external object, this table, 
 for instance ; this means that in my present state of health, 
 without amaurosis, or tactile muscular paralysis, if the table 
 be in the light, if it be within the range of my hand and my 
 eyes, if I turn my eyes towards it, or stretch out my hand 
 upon it, these two actions will be constantly followed by the 
 perception of the table. The forces, faculties, or powers 
 appertaining to this web are nothing more, then, than the 
 property which any particular event of the web has of being 
 constantly followed, under various conditions, external or in- 
 ternal, by some particular internal or external event. There 
 is nothing in the web, then, but its events, and the more or 
 less distant connections which they have with one another or 
 with external events ; and the Ego, that is the web, contains 
 nothing beyond its events and their connections. 
 
 The destruction of this metaphysical phantom lays low 
 one of the principle survivors of that army of verbal entities 
 which formerly invaded all the provinces of nature, and 
 which during the last three hundred years, the progress of 
 the sciences has one by one upset. There are two only left 
 at present, the Ego and matter ; but at that time, during the 
 avowed or dissembled empire of the scholastic philosophy, 
 men imagined that, underlying events, were a number of 
 chimerical beings the vital principle, the vegetable soul, sub- 
 stantial forms, occult qualities, plastic forces, specific virtues, 
 affinities, appetites, energies, archaea, in short, a population
 
 198 
 
 OF MENTAL EVENTS. 
 
 of mysterious agents, distinct from matter, connected with 
 matter, and believed to be indispensable to explain its trans- 
 formations. They have gradually vanished at the contact 
 of experience. Nowadays, when scientific men speak of 
 forces, physiological, chemical, physical, or mechanical, they 
 see that these names are names only. Their efforts are 
 limited to the proof of constant connections ; when they ex- 
 plain a fact, it is by means of another fact. At the highest 
 point of their theories* they establish couples of very gen- 
 eral events, the first antecedents, the second consequents, the 
 second following the first without exception or condition ; 
 from these couples they deduce other things. If they use 
 the word force it is to denote the constant connection between 
 the second and the first. If they admit different forces, it is 
 because, in the present state of our knowledge, the couples 
 to which certain groups of events are reduced cannot be 
 reduced to one another or to other couples. In short, verbal 
 entities no longer subsist except at the two extremities of 
 science in psychology, by the notion of self and its faculties ; 
 in the preliminary parts of physics by the notion of matter 
 and of its primitive forces. Hitherto, and in France especi- 
 ally, this illusion has obstructed psychology ; men have ap- 
 plied themselves to observing the pure Ego ; they have at- 
 tempted to see in the faculties " the causes which produce 
 the phenomena of the soul ; "f they have studied the reason 
 the faculty which produces ideas of the infinite, and dis- 
 covers necessary truths ; the will the faculty which pro- 
 duces free resolutions. They have thus constructed a science 
 of words alone. " From a pictured hook," says an English 
 philosopher, " we can hang only a pictured chain." Let us 
 lay aside words, let us study events, which alone are real, 
 their conditions, their dependencies, and it is certain, that by 
 following the path struck out by Condillac, and cleared by 
 James Mill and his English successors, we shall gradually 
 arrive at the construction of a science of things and of facts. 
 III. Having upset this entity at the summit of nature, 
 
 * See Mill's " Logic," and especially the theory of Induction, 
 f Gamier, " Traite des Facultes de 1'Ame," i. 33.
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. IQ Q 
 
 there remains, at the foot of nature, another entity, matter, 
 which falls by the same blow. Hitherto, the most faithful 
 followers of experience have admitted, at the foundation of 
 all corporeal events, a primitive substance, matter possessed 
 of force. Positivists themselves underwent this illusion ; in 
 spite of their reducing all knowledge to the discovery of facts 
 and their laws. Beyond the accessible region of facts and 
 laws, they placed an inaccessible region, that of substances, 
 real things, the knowledge of which would certainly be most 
 precious, but in whose direction research ought not to stray, 
 since experience attests the futility of all inquiry respecting 
 them. Now the analysis which reduces substance and force 
 to verbal entities is applicable to matter as well as to mind. 
 In the physical as in the moral world, force is that particulari- 
 ty which a fact has of being constantly followed by another 
 fact. Isolated by abstraction, and denoted by a substantive 
 name, it becomes a permanent subsisting being, that is to say, 
 a substance. But it becomes so for the convenience of dis- 
 course only, and the attempt to make anything more of it, is 
 founded on a metaphysical illusion like that which sets apart 
 the Ego and its faculties. Scientific men themselves come 
 involuntarily to this conclusion when, provided with mathe- 
 matical formulse and with the whole of the facts of physics, 
 they attempt to conceive the ultimate particles of matter.* 
 For they arrive at picturing atoms, not according to the coarse 
 imagination of the crowd, as little solid masses, but as pure 
 geometric centres, with relation to which, first, attractions, 
 then repulsions increase with increasing proximity. In all 
 this there are but movements, present, future, or possible, 
 connected with certain conditions, variable in magnitude and 
 direction according to a certain law, and determined with re- 
 lation to certain points. 
 
 Thus, in the physical as in the moral world, nothing re- 
 mains of what is commonly understood by substance and 
 force ; all left subsisting are events, their conditions and de- 
 pendences, some of them moral or conceived on the type of 
 
 * Renouvier, " Essais de Critique Generale," 2 me essai, 25 Exposition of the 
 Ideas of Boscovich, Ampere, Poisson, and Cauchy.
 
 200 OF MENTAL EVENTS. [BOOK IV. 
 
 sensation, others physical or conceived on the type of motion. 
 The notion of fact or event alone corresponds to real things. 
 In this way, the Ego is a being as much as the chemical body 
 or material atom ; only it is a more compound being, and con- 
 sequently subject to more numerous conditions of origin 
 and conservation. Chemical body, material atom, self that 
 which we term a being, is always a distinct series of events ; 
 what constitutes the forces of a being is the property of certain 
 events of its series to be constantly followed by some particu- 
 lar event of its own or of another series ; what constitutes the 
 substance of a being is the permanence of this and other ana- 
 logous properties. This is why, if we cast a general glance 
 over nature, and drive out of our minds the phantoms we have 
 set up betwaen her and our thought, we perceive in the world 
 nothing more than simultaneous series of successive events, 
 each event being the condition of another and having another 
 as its condition. 
 
 IV. This being settled, we have no difficulty in compre- 
 hending the connection between the human personality and 
 the physiological individual. For it is now no longer a ques- 
 tion of knowing how an unextended substance, termed soul, 
 can dwell in an extended substance, termed body, or how two 
 beings of nature so different can hold intercourse with one 
 another; these scholastic questions fall to the ground with 
 the scholastic entities which suggested them. All we have 
 now before our eyes is a series of events termed self, connect- 
 ed with other events forming its condition. Henceforward, 
 there is nothing strange in the dependences we have proved. 
 The web of facts which makes up our being is a distinct dis- 
 trict m the aggregate constituted by the nervous functions, 
 this aggregate itself being a distinct province in the entire liv- 
 ing animal. As we have shown, this web may be considered 
 under two aspects, directly, in itself and by consciousness, or in- 
 directly, by external perception and from the impressions it 
 produces on the senses. Next to ideas, images, and sensa- 
 tions, events of a very compound nature, of which we are 
 conscious, and which are thus distinguished from other analo- 
 gous events, are other rudimentary and elementary events of 
 the same 1-ind, of which we are not conscious, and whose ex-
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. 2OI 
 
 tences is denoted by the reflex action : such is the first aspect. 
 Next to the very compound molecular movements which 
 take place in the gray substance of the cerebral lobes and of the 
 centres termed sensory, and other analogous but less compound 
 molecular movements which take place in the gray substance 
 of the marrow and the ganglia of the sympathetic nerve ;* this 
 is the second aspect. The first is the psyschological aspect ; 
 the second is the physiological aspect. According to the 
 second, there are in the animal many centres of nervous ac- 
 tion, the ganglia of the great sympathetic nerve, the different 
 segments of the marrow, the different departments . of the 
 encephalon, more or less subordinate or predominant, more 
 or less simple or complex, but all distinct, mutually excitable, 
 and possessed of the same fundimental properties. According 
 to the first, there are in the animal many groups of mental 
 events, ideas, images, sensations strictly so called, rudimen- 
 tary and elementary sensations, all more or less subordinate 
 or predominat, more or less simple or complex, but distinct, 
 mutually excitable, and more or less analogous to sensation. 
 By somewhat straining language, we might consider the 
 marrow as a string of rudimentary encephala, and the ganglia 
 of the sympathetic nerve as a network of still more rudiment- 
 ary encephala.f Consequently, we should see, in the groups 
 of rudimentary sensations of which we are not conscious, 
 rudimentary souls ; and just as the nervous apparatus is a 
 system of organs in different states of complication, so the 
 psychological individual would be a system of souls in differ- 
 ent degrees of development. 
 
 We must not take these metaphors for more than they are 
 worth, that is to say, for phrases translating into ordinary 
 language the positive facts we have proved. But, as we des- 
 cend the animal kingdom we constantly find them becoming 
 more and more exact; the mutual dependence of the nervous 
 centres becomes less strict ; each centre is less affected by 
 being cut off from the rest ; and when isolated, performs its 
 
 * Experiments of Claude Bernard on the reflex power of the submaxillary 
 ganglion. 
 
 f See Landry, " Des Paralysies," 47, cited ante, p. 184.
 
 202 OF MENTAL EVENTS. [BooK IV. 
 
 functions less incompletely and for a longer time. We have 
 seen that, in a triton or a frog, the hindquarters go through 
 complex movements when separated from the rest of the body, 
 movements adapted to a purpose, and capable, under altered 
 circumstances, of adapting themselves to another purpose. 
 These co-odinated movements which seem to denote an inten- 
 tion, are still more visible in the severed portions of insects.* 
 This extends so far that many observers have seen in such 
 movements a true intention, and consequently true represen- 
 tations, just as those of which the cerebral lobes are the 
 organs. " I remove rapidly with scissors," says Duges, " the 
 anterior segment of the thorax of the Mantis religiosa. The 
 posterior part of the body still remains balanced upon the 
 four legs which belong to it, resisting and attempt to over- 
 throw it, recovering its position when disturbed and perform- 
 ing the same agitated movements of the wings and elytra, as 
 when the unmutilated insect is irritated The experi- 
 ment may be pursued in a more striking manner. The anter- 
 ior part of the thorax contains a bilobed ganglion, sending 
 out nerves to the arms or fore-limbs, which are armed with 
 powerful claws. If the head be removed, the detached por- 
 tion will then live for nearly an hour with its solitary ganglion ; 
 it will set in motion its long arms, aud knows how to turn 
 them against the fingers of the experimenter who holds it, 
 and to insert its hooks in them." 
 
 If we descend a step lower, the fundamentary plurality of 
 the animal will become more evident. " With the Annelids, 
 each ganglion corresponds to a segment of the body, often 
 formed of many rings, as for instance, with leeches, all whose 
 parts are repeated with every five rings. Every segment thus 
 possesses, besides this ganglion, a similar portion of the prin- 
 cipal apparatus, sometimes even of the apparatus of the 
 senses. This is the case with the Polyophthalmus, in which 
 each segment is provided with two rudimentary eyes, each 
 receiving a nervous thread from the corresponding ganglion, 
 a real optic nerve." Each of these segments is a complete 
 
 * Vulpian, op. cit. 790. Experiments of Duges, Dujardin, Walkenaer, etc. 
 Duges, " Physiologic Comparee," i. 337.
 
 CHAP. III.] SELF AND THE ORGANIZED BODY. 203 
 
 animal, and the whole animal is formed " of several element- 
 ary animals placed one after another." Thus it is that, when 
 separated, each is still an independent centre of co-ordinated 
 reflex actions adapted to an end. Now the only difference 
 between a nervous system so constituted, and the nervous 
 system of a mammal, is that the segments of the first are 
 more complete and independent than those of the second. 
 In fact, anatomy shows that a vertebral column, like, an annelid, 
 is composed of distinct segments, medullary and protecting, 
 that the skull itself is made up of flattened and consolidated 
 vertebrae, and that the brain is nothing more than a prolon- 
 gation and development of the spinal marrow. In short, the 
 republic of nervous centres, all equal and almost independant, 
 which we meet with among the inferior animals, is gradually 
 changed as we ascend to the superior animals, into a monarchy 
 of unequally developed and intimately connected centres 
 subject to one principal centre. But this advanced organ- 
 ization and centralization do not suppress the original plurality 
 of the being so constituted. In proportion as it rises in the 
 scale, it departs from the state in which it was a total, and 
 approaches the state in which it will be an individual ; that is 
 all. Even when in the state of an individual, we can push it 
 back into the state of a total ; by affecting transverse segments 
 in the marrow of a young mammal, it is possible, if circulation 
 and respiration go on, to maintain in it, for several weeks, in- 
 dependent segments, each capable of reflex action, and incapa- 
 ble of receiving from or transmitting to others any excitation 
 whatever.* Lastly, at the lowest point of the animal scale, 
 with zoophytes for instance, in which no nervous system is ap- 
 parent, and in which nervous matter probably exists in a dif- 
 fused state only, the pluralityand division are much greater still; 
 for a polypus may be cut in every direction, and even chopped 
 up ; each fragment becomes complete, and furnishes an animal 
 having all the faculties and instincts of the primitive animal. 
 
 The reader sees now how the web of events, which is our- 
 selves, and of which we have consciousnesss, is connected 
 with the rest. This series which, according to the aspect in 
 
 * See ante p, 184.
 
 204 OF MENTAL EVENTS. [BOOK IV. 
 
 which we consider it, is sometimes, to our senses, a series of 
 molecular movements, sometimes, to our consciousness, a 
 series of sensations, more or less transformed is nothing 
 more than the most complex and most predominant in a group 
 of other analogous series. In proportion as we descend the 
 animal scale, we see it lose its domination and complexity, 
 and become reduced to the level of the others, while these in 
 turn loosen their mutual connections, and become insensibly 
 degraded. To external perception, they have all for condi- 
 tion of existence, the integrity and renewal of the nervous sys- 
 tem whose special activity they are, and the beings, more or 
 less strictly bound together, which they constitute, whatever 
 they may be to consciousness, with whatever names metaphy- 
 sical or literary illusion may clothe them, are subject to the 
 same condition.
 
 CHAP. I.] OF ILLUSION. 20$ 
 
 PART THE SECOND. 
 
 THE DIFFERENT KINDS OF KNOWLEDGE. 
 
 BOOK I. 
 OF THE GENERAL MECHANISM OF KNOWLEDGE. 
 
 CHAPTER I. 
 
 OF ILLUSION. 
 
 I. The reader has now followed, under all its forms, the 
 internal event which constitutes our knowledge. Our ideas 
 are signs, that is to say, sensations or images of a certain 
 kind. Our images are repeated surviving and spontaneously 
 reviving sensations, that is to say, sensations of a certain kind. 
 Our sensations strictly so called are whole sensations, made 
 up of more simple sensations, these of still simpler ones, and 
 so on. We may, then, for want of a better name, say, with 
 Condillac, that the internal primordial event which constitutes 
 our knowledge is sensation. But it must be observed that 
 this name simply denotes its most remarkable state, that in 
 this state it is but a total or group of elementary sensations, 
 themselves composed of more elementary sensations, that by 
 the side of these are other rudimentary ones, equally inacces- 
 sible to consciousness, and whose presence is indicated by re- 
 flex actions, and that thus the internal primordial event is 
 progressively simplified and degraded to an infinite extent be- 
 yond our range and grasp. We must further observe, to un- 
 derstand it properly, that in another aspect, that is, seen 
 from without and by means of external perception, it is a mo- 
 lecular movement of the nervous centres, and so comes with-
 
 206 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I 
 
 in the category of physical phenomena. We must finally ob- 
 serve that the names of force and substance, of self and mat- 
 ter, denote metaphysical entities only, that there is nothing 
 real in nature but connected webs of inter-connected events, 
 that these are all we find in ourselves or in other things. 
 
 o 
 
 This is why, in order to form a first notion of mind, we must 
 represent to ourselves one of these webs, and postulate that, 
 being known by two different processes, external perception 
 and consciousness, it mnst perforce appear under two irreduc- 
 ible aspects of unequal importance, that is to say, moral on 
 the face and physical on the reverse. The primordial event 
 being thus disengaged and determined, we have now with its 
 combinations to construct the rest. 
 
 We are conscious of our states of mind, we recollect them, 
 we forsee many of them. We perceive external objects, we 
 recollect their changes, we forsee many of them. Besides these 
 operations, which are common to us with animals, there are 
 others, special to ourselves. We form abstractions and gen- 
 eralizations, we conclude, we reason, we construct ideal ob- 
 jects. These are the principal groups of acts which make 
 up our cognitions. How can such a being as we have describ- 
 ed accomplish these ? How can they be constructed out of 
 such internal events as we have described ? This is the ques- 
 tion, and it is not solved by saying, as many psychologists do, 
 that we have such and such faculties, consciousness, memory, 
 imagination, or reason. These are verbal explanations, inher- 
 ited from the school-men. To explain one of these acts is to 
 distinguish its elements, to show their order, to determine 
 the conditions of their origin and combination. Now the 
 events we have been studying, signs, images, sensations, are 
 the elements of all knowledge. By their association or 
 their conflict, they become transformed. On the one hand, 
 they appear other than they are. On the other hand, by a 
 more or less complete correction, they are stripped of this 
 false appearance. Two principal processes are employed by 
 nature to produce the operations we term cognitions: the 
 one consisting in the creation, of illusions within us ; the other 
 consisting in their rectification. It is by this double operation 
 that the mental edifice is raised and completed ; hitherto we
 
 CHAP. I.] OF ILLUSION. 2O/ 
 
 have been observing the materials ; now, we must study its 
 structure. Let us commence at once with examples ; we 
 shall better understand the meaning of the words by first see- 
 ing the particulars of the facts. 
 
 II. A woman makes violent gestures, wipes her eyes with 
 her handkerchief, and sobs, hiding her face in her hands. She 
 cries in a plaintive voice : " Good God ! how wretched I am ! " 
 Her face is contracted, her chest heaves, she is panting, and 
 her stifled cries are incessantly renewed. She is acting grief; 
 but if I happen not to know this, it seems to me that she is in 
 great grief; which means that her gestures, her features, cries, 
 and words are the same, and arouse in me the same ideas as 
 if she were in great grief. Between her grief and my idea, is 
 a series of intermediaries, the. first of which is her expressive 
 attitude. This attitude is usually preceded by grief, but usu- 
 ally only. If the woman is a skilful actress, the grief may be 
 wanting though the attitude is there, and I shall form the 
 same conclusion as if the grief were there. 
 
 So again, a stick is plunged half-way into water ; it seems 
 bent, though it is straight. But between the presence of the 
 stick and my preception there are several intermediaries, the 
 first of which is a pencil of luminous rays. In the most com- 
 mon case, that is, when the stick is wholly in the air or whol- 
 ly in the water, if the rays from one-half are inflected with ref- 
 erence to the rays from the other half, the stick is actually 
 curved ; but this Is only the most common case. When by 
 exception the straight stick is plunged into two unequally^ 
 refracting media, although it is straight, the rays from one- 
 half will be inflected with reference to the rays from the 
 other half, and I shall have the same perception as if the stick 
 were bent. 
 
 Lastly, take the case of a person who has lost a leg and 
 complains of tinglings in the heel. He actually experiences 
 tinglings ; but not in the heel he no longer possesses ; only 
 the feeling seems to be there. Here again, between the nerv- 
 ous disturbance in the heel and the judgment which situates 
 the sensation in that spot, there are many intermediaries 
 the principal one being the sensation itself. Usually, when 
 the sensation arises, it is preceded by peripheral disturbance,
 
 2o8 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 but usually only. When by exception the central extremity 
 existing after amputation enters into activity, the sensation 
 will arise though the heel is destroyed, and the patient will 
 form the same conclusion as when he still had his leg. These 
 examples show us very clearly in what the appearance con- 
 sists. There are three terms forming the three links of a 
 chain ; an antecedent, the asserted fact, an intermediary, 
 which is usually preceded by the antecedent, an idea, belief, 
 judgment, or perception, which always follows the intermediary, 
 and refers to the antecedent. For the affirmative judgment 
 to be produced it is sufficient for the intermediary to be pro- 
 duced; it matters little whether the antecedent exists or not. 
 To push this further. The antecedent has been hitherto 
 simply a property of the object, sometimes absent, sometimes 
 present ; in fact, what we have been considering has been 
 the situation of a tingling, the curvature of a stick, the troub- 
 le of a woman. Let us now look for a case in which the an- 
 tecedent is the object itself; this is what happens in halluci- 
 nations. A man sees, with eyes closed or open, the perfectly 
 distinct head of a corpse three paces in front of him, though 
 no such head is there. This means, just as in the previous 
 instances, that between the actual presence of a corpse's head 
 and the affirmative perception, are a group of intermediaries, 
 the last of which is a particular visual sensation of the nerv- 
 ous centres. Usually, this sensation has as its antecedents a 
 certain molecular motion of the optic nerves, a certain im- 
 pingement of luminous rays, lastly, the presence of the real 
 head of a corpse. But it is usually only that these three ante- 
 cedents precede'the sensation. If the sensation is produced in 
 their absence, the affirmative perception will arise in their ab- 
 sence, and the man will see a corpse's head which is not ac- 
 tually there. Here again, the presence of the last intermediary 
 is sufficient to cause the perception to arise ; it matters little 
 whether the antecedents exist or not. We see by all these 
 examples that an object or property which do not exist seems 
 to us to exist, when the final effect which they usually pro- 
 duce in us by an intermediary, is produced in us without their 
 existence. Their intermediary replaces them ; it is equival- 
 ent to them.
 
 CHAP. I.] OF ILLUSION. 
 
 209 
 
 Now it is readily seen that in all these instances the final 
 intermediary which immediately precedes the affirmative idea, 
 belief, perception, or judgment, is a sensation. The others 
 act only by and through it. Remove all but it; suppress 
 the thing itself, as is done in instruments for producing optical 
 delusions ; suppress the luminous rays, which is what happens 
 in the cases of the subjective images we see with our eyes 
 closed ; suppress the disturbance of the peripheral extremity 
 of the nerve, which happens in the illusions of persons who 
 have lost limbs ; suppress all action of the nerve, which is 
 what happens in hallucination strictly so called ; leave noth- 
 ing subsisting but the sensation or activity of the centres of 
 sensation, there is hallucination, and consequently affirmative 
 judgment. On the contrary, suppress this sensation or 
 activity of the centres of sensation, while preserving the 
 other intermediaries and the object itself; let there be an 
 object present, and in the light, let the extremity of the 
 nerve be in action, let this action be propagated through the 
 whole course of the nerve ; if the nervous centres are be- 
 numbed by chloroform, or if, as happens in hypnotism and 
 in impassioned attention, an anterior dominant sensation 
 closes the access to supervening sensations, a drum may be 
 beaten in the room, or the patient may be pinched, pricked, 
 and wounded without his ever surmising it ; as he does not 
 experience the sensation of sound, or the pain of the wound, 
 he will perceive neither drum nor cutting instrument. In 
 short, in the absence of any ulterior obstacle, it is necessary 
 and sufficient for the production of the perception or affirma- 
 tive judgment that the sensation or action of the nervous 
 centres be produced. In this respect mental operations re- 
 semble vital operations. If we remove the tail from a tad- 
 pole and throw it into water, it will become organized and 
 developed up to the tenth day, just as if it had remained in 
 its first place.* If we cut off the paw of a young rat, and, 
 having skinned it, place it under the skin of the side of an- 
 other rat, it becomes grafted on, is nourished, and grows 
 
 * Vulpian, 296. See the whole thesis of Paul Bert, " Sur la Vitalite Propre 
 des Tissus Animaux." 
 
 i4
 
 2IO GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 there and acquires its full development, all its connections, 
 all its ordinary structure, just as if it had remained attached 
 to its former owner. Such is the vital process ; in the ab- 
 sence of ulterior obstacles, that is to say, if the medium be 
 a fitting one, it goes on blindly, whether its result be useful, 
 useless, or even harmful. So is it again with the mental pro- 
 cess ; in the absence of paralysis or other hindrance in the 
 cerebral lobes, as soon as the sensation is given, the affirma- 
 tive perception or judgment follows, whether false or true, 
 salutary or pernicious, matters little, even should the hallu- 
 cination which sometimes constitutes its lead on to suicide, 
 and destroy the customary harmony adjusting our activity to 
 the coarse of the universe. 
 
 III. Thence follows a consequence of capital importance: 
 it is that external perception is a true hallucination. Let 
 us fully understand this truth in the guise of a paradox. A 
 person laboring under hallucination who sees a corpse's head 
 three paces in front of him, experiences at that moment an 
 internal visual sensation precisely similar to what he would 
 experience if his open eyes were then to receive the lumin- 
 ous rays coming from the head of a real corpse. There is 
 no real corpse's head in front of him ; there are no gray and 
 yellowish rays coming from it ; there is no impression made 
 by such rays on his retina, or transmitted by his optic nerves 
 to the centres of sensation. What is really three paces in 
 front of him is a red arm-chair ; the rays coming from it are 
 red ; the impression made on his retina and propagated thence 
 to the centres of sensation is one of red rays. But never- 
 theless, the action of the centres of sensation is that which 
 would in their normal state, be excited in them, by gray and 
 yellowish rays, such as an actual corpse's head would emit. 
 This action of the centres of sensation, in other words, this 
 spontaneous visual sensation, is sufficient to call up in him 
 an apparent corpse's head, apparently situated three paces 
 off, apparently possessed of relief and solidity, an internal 
 phantom, but so closely resembling an external and real ob- 
 ject that the patient gives a cry of horror. Such is the effi- 
 cacy of the visual sensation strictly so called ; and it extends 
 so far that the sensation possesses it even when the normal
 
 CHAP. I.] OF ILLUSION. 211 
 
 antecedents are absent. It extends then to the cases in which 
 the normal antecedents are present ; therefore when the 
 corpse's head is real and present, when a pencil of gray and 
 yellowish rays starts from it to strike the retina, when this 
 impression of the retina is propogated along the optic nerves, 
 when the action of the centres of sensation corresponds to 
 it, the visual sensation so excited will give rise to the same 
 internal phantom, and the semblance of the corpse's head, 
 which is produced in us during hallucination, properly so 
 called, will also be produced in us during external perception, 
 with this difference only, that, in the first case, the hand or 
 other sense, the bystander to whom we appeal to attest our 
 affirmative judgment, will pronounce it false, whilst, in the 
 second case, the hand or other sense, the bystander to whom 
 we appeal to test our affirmative judgment, will confirm it ; 
 and this we express by saying, in the first case, that the ob- 
 ject is apparent only, and, in the second case, that it is real. 
 It is readily seen that this analysis is applicable not only to 
 visual sensations, but to all others, since all the others admit 
 of hallucinations. Therefore, when we walk in the street, 
 watching and listening to what passes around us, we have 
 within us the various phantoms which would be experienced 
 by a sufferer from hallucinations shut up in his room, and in 
 whose case the visual, auditory, and tactile sensations which 
 are produced in our case by the action of the nerves would 
 all be produced in the same order but without the medium 
 of the nerves. These various phantoms are in our case, as in 
 his, houses, roads, carriages, pavements, and passers-by. Only, 
 in our case, there are objects and external events, indepen- 
 dent of ourselves and real, proved by the ulterior experience 
 of the other senses, and by the concurring testimony of other 
 observers, which correspond to our phantoms ; while, in his 
 case, there is no such correspondence. Thus, external per- 
 ception is an internal dream which proves to be in harmony 
 with external things ; and instead of calling hallucination a 
 false external perception, we must call external perception a 
 true hallucination. Illness separates the internal event and 
 shows it us as it is, in the state of a colored, intense, precise, 
 and localized semblance. In this state, it is no longer con-
 
 212 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 fused with things ; we can distinguish it from them, and im- 
 mediately on this we may, with fair reason, conclude its 
 presence when health and reason are perfect ; hence it fol- 
 lows that, while health and reason are perfect, it is this in- 
 ternal event, this semblance which we take for a subsisting 
 thing other than ourselves and placed without us. 
 
 By the same stroke we comprehend and correct the error 
 into which consciousness naturally falls with respect to exter- 
 nal perception. When we examine our perception of things 
 without, we are tempted to mistake it for a simple naked act 
 of mind, destitute of any sensible character, and indeed of any 
 character other than its relation with the thing which is its 
 object. Take the case of a table, I see it, touch it, perceive 
 it. In addition to my tactile and visual sensations, I find 
 nothing in me but an act of pure attention, a spiritual act, 
 unique in kind, incomparable to any other. There is nothing 
 strange in this conclusion ; if the act is pure and spiritual, it is 
 because it is empty ; we have emptied it ourselves by taking 
 from it all its characters, to set them apart and form from 
 them an object. The external perception of an arm-chair is 
 nothing more than the phantom of the arm-chair ; when, in 
 accordance with habit, we consider this phantom as a real and 
 external object, we cut away from perception all that consti- 
 tutes it, and, from a full act, we form a void or abstract act. 
 We have already seen many instances of this illusion ; we 
 shall see many more such ; thus arise the beings and spiritual 
 activities with which metaphysics and psychology are still 
 crowded. Many philosophers, and all those who content them- 
 selves with words, are subject to this error. Usually they 
 picture to themselves our cognitions, external perceptions, 
 recollections, acts of consciousness or of reason, as acts of a 
 special and simple nature, of which we are unable to say any 
 thing more than that they are each an activity and a relation, 
 the activity of a simple being, which by their means enters into 
 relation with extended beings other than itself, with itself, 
 with past events, with laws or higher truths. Science, in this 
 acceptation of it, is soon constructed ; there is nothing to seek 
 or to find in an activity like this, since it is simple ; when once 
 we have given it a name we have come to an end. The truth
 
 CHAP. I.] OF ILLUSION. 213 
 
 is we have found names, which is somewhat unimportant. 
 The truth again is that, if we have come to an end it is be- 
 cause we have ourselves barred the way. Neither external 
 perception nor the other acquisitions of consciousness are sim- 
 ple activities applying to and ending in objects differing from 
 themselves. They are symbols, phantoms, or semblances* 
 of these objects, hallucinations, usually true, and arranged, by 
 an artifice of nature, in such a way as to correspond to objects, 
 and all are more or less advanced, retarded, and altered in 
 their development. We shall see the detail and the arrange- 
 ment in the following pages. Meanwhile let us keep in mind 
 this principle, that sensation, whether in the absence or pres- 
 ence of impulsions from without and of nervous action, produces 
 hallucinations, and produces them by itself alone. It is the 
 motive spring of all the mechanism, and so much so that, for 
 the purpose of renewing and perpetuating our knowledge, 
 nature has given it a substitute. 
 
 IV. This substitute is the image ; by the side of sensations 
 strictly so called, which are, by nature, temporary, connected 
 with the vibration of the nerves, almost always incapable of 
 reviving spontaneously, and situated in the centres of sensa- 
 tion, there is another series within us of absolutely analogous 
 events, which are, by nature, durable, which survive the vibra- 
 tion of the nerve, are capable of reviving spontaneously, and 
 are situated in the cerebral lobes or hemispheres. These are 
 what we have termed images. Here are a second group of 
 sensations, so similar to the first that we may call them reviv- 
 ing sensations, and repeating the first, as a copy repeats an 
 original, or as an echo repeats a sound. In this way they 
 have the properties of the first, they replace the first when 
 absent, and, as they perform the same function, must give rise 
 to the same mental process. 
 
 This is what experience has already shown us. The more 
 complete, that is to say the more intense and precise do they 
 
 * All the terms by which men have denoted the phenomenon result etymologi- 
 cally in the same meaning. Conception (cum-capere, the thing becomes internal). 
 Representation (rursus prsesens, the thing present anew though actually absent). 
 Idea (Eidos, the figure, the image, the semblance, the appearance of the thing 
 instead of the thing itself). So in German, Begriff, Vorstellung, &c.
 
 214 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 become, the more does the operation they give rise to border 
 on hallucination. Represent to yourself some particular ob 
 ject you are well acquainted with, for instance, some little 
 brook running among poplars and willows. If you have a 
 clear imagination, and permit yourself to become absorbed in 
 the reverie as you sit by the fire, you will soon see the glis 
 tening waves on its surface, the yellowish or ash-colored leaves 
 floating down its stream, the little eddies agitating the water 
 cresses, the cold shade of the lines of trees ; you will almost 
 hear the ceaseless whispering of the branches and the vague 
 rustling of the water striking against its banks. Fragments 
 of your former sensations have revived in you ; you have seen 
 again, with closed eyes, patches of green, of blue, of dark glit- 
 ter ; scraps of sound have come back ; and these surviving 
 wrecks of the primitive sensation have had, on a small scale 
 and incompletely, but with all their proportions preserved, 
 the same effect as the primitive sensation ; the hallucinatory 
 process has been half effected. 
 
 Let us get rid of the obstacles which hinder its completion. 
 Let us take the case of the images which present themselves 
 at the moment the waking state draws to a close, and sleep 
 begins.* We have seen that they become brightened and 
 precise, in proportion as our present sensations become more 
 and more vague and feeble ; after some seconds we seem to 
 hear real sounds, to see real forms, to actually smell, taste, 
 and touch. By a necessary consequence, affirmative judg- 
 ments follow these images ; according to their kind we think 
 we have before us such and such an object, " an open book, 
 printed in very small text which we read with difficulty^ an 
 hermaphrodite, a stew with mustard in it, giving out a very 
 sharp smell, some picture of Michael Angelo, a lion, a green 
 rhomboidal figure," numbers of persons, landscapes. When 
 sleep has actually come on, the hallucination, then at its 
 height, makes up what we term our dreams. When the sleep, 
 instead of being natural, is artificial, the hallucinatory process 
 becomes plainer still. Such are the cases of hypnotism and 
 
 * Cf. Maury, " Le Sommeil," &c., p. 33. 
 f Maury, ibid. p. 51, Observations made on himself.
 
 CHAP. I.] OF ILLUSION. 
 
 somnambulism. In this state, which may be excited at will 
 in many persons, the patient believes, without resistance or 
 reserve, in all notions suggested ^ to him, and these may be 
 suggested to him in two ways. 
 
 The first means of suggestion is to give the patient an at- 
 titude which would correspond with some particular feeling, 
 or which would be assumed in commencing some particular 
 action, or which would indicate the presence of some object ; 
 he will, of his own accord, complete the attitude, and immedi- 
 ately experiences the feeling, goes through the action, and 
 believes in the presence of the object. If the head be thrown 
 slightly back, and the spine straightened, " his countenance 
 then assumes an expression of the most lofty pride, and his 
 whole mind is obviously possessed by the feeling." At this 
 moment, " let the head be bent forward, and the body and 
 limbs gently flexed-; and the most profound humility then takes 
 its place." If the corners of the mouth be gently separated, 
 he becomes lively at once ; and, when the eyebrows are drawn 
 towards each other, and downwards, he becomes morose ; 
 sometimes on waking he is still conscious of the insurmounta- 
 ble emotions into which he has been thrown and fixed by the 
 ascendancy of the attitude. " So, again," says Carpenter, 
 " not merely emotional states, but definite ideas are thus ex- 
 citable. Thus, if the hand be raised above the head, and the 
 fingers are flexed upon the palm, the idea of climbing, swim- 
 ming, or pulling at a rope is called up ; if, on the other h^nd, 
 the fingers are flexed while the arm is hanging down at the 
 side, the idea excited is that of lifting a weight ; and if the 
 same be done when the arm is advanced forwards in the posi- 
 tion of striking a blow, the idea of fighting is at once aroused." 
 The somnambulist proceeds to complete the action, that is 
 to say, he begins to box, to draw up his arm with difficulty, 
 to move his limbs as if to climb, to swim, or to pull a rope. 
 
 \ Braid, " Neurhypnology." Carpenter, article " Sleep" in Todd's " Cyclopce- 
 dia." Dr. Hack Tuke, " De la Folie Artificielle," " Annales Medico-Psychologi- 
 ques," 4"ie Serie, vi. 429, and vii. Maury, " Le Sommeil," &c. ; the whole of chap. 
 II and p. 424. Azam, "Annales de Medecine et de Chirurgie," Jan., 1840 ; and 
 " Annales Medico-Psychologiques," 3^10 Serie, vi. 430. Dr. Philips, " Cours de 
 Braidisme, theorique et pratique."
 
 2i6 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 The second means of suggestion consists in words, and 
 this process sometimes succeeds in ordinary somnambulism. 
 " We knew," says Carpenter, " a young lady at school, who 
 frequently began to talk after having been asleep an hour or 
 two ; her ideas almost always ran upon the events of the pre- 
 vious day ; and if encouraged by leading questions addressed 
 to her, she would give a very distinct and coherent account 
 of them ; frequently disclosing her own peccadilloes knd those 
 of her school-fellows, and expressing great penitence for the 
 former, whilst she seemed to hesitate about making known 
 the latter. To all ordinary sounds, however, she seemed per- 
 fectly insensible, .... and, if the interlocutor addressed to 
 her any questions or observations that did not fall in with 
 
 her train of thought, they were completely disregarded 
 
 The well-known case of the officer, narrated by Dr. James 
 Gregory, is one of the same intermediate class ; rather allied, 
 in our apprehension, to somnambulism than to ordinary dream- 
 ing. This gentleman, who served in the expedition to Louis- 
 burgh in 1^58, was in the habit of acting his dreams; and 
 their course could be completely directed by whispering into 
 his ear, especially if this was done by a friend with whose 
 voice he was familiar ; so that his companions in the transport 
 were in the constant habit of amusing themselves at his ex- 
 pense. At one time they conducted him through the whole 
 progress of a quarrel, which ended in a duel ; and when the 
 parties were supposed to be met, a pistol was put into his 
 hand, which he fired, and was awakened by the report. On 
 another occasion they found him on top of a locker, or bunker, 
 in the cabin, when they made him believe he had fallen over- 
 board, and exhorted him to save himself by swimming. He 
 immediately imitated all the motions of swimming. They 
 then told him that a shark was pursuing him, and entreated 
 him to dive for his life. He instantly did so, with such force 
 as to throw himself entirely from the locker upon the cabin 
 floor, by which he was much bruised, and awakened of course. 
 After the landing of the army at Louisburgh, his friends 
 found him one day asleep in his tent, and evidently much an- 
 noyed by the cannonading. They then made him believe that 
 he was engaged, when he expressed great fear, and showed
 
 CHAP. I.] OF ILLUSION. 2I/ 
 
 an evident disposition to run away. Against this they re- 
 monstrated ; but, at the same time, increased his fears, by imi- 
 tating the groans of the wounded and the dying ; and when 
 he asked, as he often did, who was down, they named his par- 
 ticular friends. At last they told him that the man next him- 
 self in the line had fallen, when he instantly sprung from his 
 bed, rushed out of the tent, and was roused from his danger 
 and his dream together by falling over the tent-ropes. After 
 these experiments he had no distinct recollection of his 
 dreams, but only a confused feeling of oppression and fatigue ; 
 and used to tell his friends that he was sure they had been 
 playing some trick upon him." 
 
 Artificial or induced somnambulism puts the mind into a 
 similar state. " If you tell a somnambulist that you are a 
 lion, and assume something of its attitude by going on all 
 fours and imitating its roar, the magnetized person at once 
 exhibits violent fear, which appears in all his features, and 
 shows all the signs of positive conviction."* When a person 
 is hypnotized, says Dr. Tuke,f he may often " be made be- 
 lieve by suggestion that he sees an absent person. ... So 
 it is possible to make him imagine that he hears a particular 
 air played on an instrument, while really there is no sound 
 produced." Words excite in the patient the images of cer- 
 tain auditory or visual sensations, and the mental process 
 which ensues is precisely the same as if the sensations them- 
 selves had been aroused through the medium of the nerves. 
 
 The same process ensues whatever be the kind of the im- 
 ages. U C. D., when hypnotized, was asked to feel the oper- 
 ator's fingers. He answered that he felt nothing. The oper- 
 ator then placed his finger and thumb, joined together, under 
 the patient's nose, and told him to draw in his breath, so as 
 to take a pinch of snuff. The suggestion took effect at once. 
 The patient drew in his breath, and then showed all the symp- 
 toms consequent on taking a sternutatory powder." And 
 so, " tell a person properly prepared by hypnotism that he is 
 
 * Maury, 333. I have myself watched analogous experiments at the house of 
 Dr. Fuel. A somnambulist was told that she was in a garden ; she went through 
 the motion of plucking flowers and smelling them with great pleasure. 
 
 f " Annales Medico-Psychologiques," 4e Serie, vi. 427 : and vii. 261.
 
 2i8 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 eating rhubarb, that he is chewing tobacco, or some other sub- 
 stance of unpleasant taste, .... and the effect will follow 
 the words. Thus, one W. H. was hypnotized, and a glass of 
 pure water placed before him, which he was induced to take 
 as brandy. He praised it as excellent the water had, in fact, 
 for him the taste of brandy and drank it eagerly, asking for 
 another. In the second instance, J. K., when in the same 
 abnormal state was asked to drink a little fresh water, and, 
 while he did so, the operator drank a little of it himself, and 
 spat it out at once with an expression of horror and disgust. 
 This action suggested at once to the patient that the water 
 .was impure or perhaps poisoned, so much so that in this per- 
 suasion he spat it out with disgust." The same illu- 
 sion occurs when the image suggested is that of a sensation 
 of touch. " C. D. was hypnotized, and induced to believe 
 that he was covered with bees. He gave credence to the 
 suggestion at once, and acted precisely as a person would do 
 when stung. He gave all the signs of pain, shook his hair, 
 rubbed his face with his hands in a frantic manner, and then 
 tore off his coat to rid himself of his imaginary assailants. 
 He was evidently laboring under an hallucination of general 
 sensibility. The same thing may be said of another person, 
 E. F., who, under the same conditions of somnambulism, was 
 led by suggestion to believe that she suffered from a violent 
 toothache, the operator increasing the effect of his words by 
 placing his finger on the patient's cheek, when she buried her 
 face in her hands, and moved from side to side, writhing with 
 pain." 
 
 In all these instances, the physical and moral conditions 
 which usually repress the hallucinatory process are absent. 
 In fact, the nerves and centres of sensation are benumbed ; 
 all that portion of the nervous system by which we commu- 
 nicate with the outer world becomes inactive, or compara- 
 tively so. When this happens, we have, in fact, no sensations 
 strictly so called, or at all events those which we have are sin- 
 gularly blunted, and are of no effect as far as we are concern- 
 ed. They all cease in the case of the ordinary sleeper; with 
 the dreamer those only subsist which harmonize with his 
 dreams ; the somnambulist and hypnotized person preserve a
 
 CHAP. I.] OF ILLUSION. 2 19 
 
 series of them only, those termed muscular or those of the 
 sounds put before him by the operator. Sensations thus lose 
 wholly or in part the control they exercise in the normal 
 state. In physiological language the equilibrium subsisting 
 in the waking state between the nerves and nervous centres 
 on the one side, and the hemispheres on the other, is upset 
 in favor of the hemispheres ; they perform their functions 
 alone, and in a preponderating manner. In psychological lan- 
 guage the equilibrium subsisting in the waking state between 
 sensations and images is upset in favor of the images ; they 
 acquire their full development and all their consequences ; they 
 become intense and precise, result in affirmative judgments, 
 produce the same mental process as sensations themselves, 
 and give rise to hallucinations. ' 
 
 V. An important consequence follows from this. We 
 have seen that in every representation, conception, or idea, 
 there is an image or a group of images. When I think of 
 any particular object, the Louvre for instance, there is some 
 image in my mind of the visual sensation I should have in its 
 presence. When I think of a general object, the tree or the 
 animal, there is some fragment, more or less vague, in my 
 mind of an analogous image, and, in every case, the image of 
 its name, that is to say, the visual, auditory, muscular sensa- 
 tions, which the name would excite in me if I read, pro- 
 nounced, or heard it. Consequently, in all the higher opera- 
 tions we effect by means of abstract names judgment, rea- 
 soning, abstraction, generalization, combination of ideas 
 there are images more or less effaced or more or less distinct. 
 On the other hand it is evident that all recollections and all 
 previsions contain images. When I recollect that the sun 
 rose yesterday at a particular point of the horizon, and when 
 I predict that it will rise to-morrow at some other particular 
 point, I have internally the image, vague or distinct, of the 
 visual sensation which I had yesterday, and the visual sensa- 
 tion I shall have to-morrow. And so again, all the associated 
 perceptions which recollection and prevision add to the crude 
 sensation to constitute ordinary external perception, all the 
 judgments, beliefs, and conjectures which a simple sensation 
 excites as to the distance, form, kind, and properties of objects,
 
 220 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 contain images. This arm-chair, three paces from me, gives 
 my eyes the sensation only of a green patch, differently shaded, 
 according to its different parts ; still, from this simple visual 
 indication, I conclude that it is solid, soft, with a certain mag- 
 nitude and form, and that I may seat myself in it ; in other 
 words, I imagine the certainty of a series of muscular and 
 tactile sensations which my hands and body would have, if I 
 were to make the experiment. Lastly, in consciousness itself, 
 for instance, in the consciousness of our present sensations, 
 there are images ; for, when we are conscious of a pain, a 
 taste, a muscular effort, a sensation of cold or heat, we situ- 
 ate it at some spot or other of our organs or limbs ; in other 
 words, my sensation arouses the image of the tactile, visual, 
 and muscular sensations of which I should avail myself to rec- 
 ognize the spot at which the nervous disturbance is produced. 
 
 Thence it follows that all these operations comprise an 
 hallucination, at all events in an incipient state. The image, 
 a spontaneous repetition of the sensation, tends like it to 
 excite an hallucination. No doubt it does not fully excite 
 it ; the mental process which has commenced is checked by 
 surrounding repressions ; the image must be alone and left 
 to itself, as in sleep and hypnotism, to attain its full develop- 
 ment and produce its whole effect ; it does this in part only ; 
 when it does so completely the man is mad. But whether 
 the hallucinatory process be commenced or completed mat- 
 ters little, and the state of our mind when we are awake and 
 in health may be defined as a series of hallucinations which 
 do not become developed. 
 
 Let us, in fact, consider our usual representations and the 
 habitual tenantry of our brain : let us picture to ourselves 
 some house, some street, some study, some drawing-room, 
 certain human figures, certain sounds, smells, tastes, feelings 
 of contact, muscular efforts, and, above all, certain words ; 
 these last read, heard, or pronounced mentally, form most 
 numerous inmates of a thinking brain. All are phantoms of 
 external objects, semblances, of action and sensation, recog- 
 nized on the spot as simple appearances, and, moreover, fugi- 
 tive, effaced, incomplete, but, on the whole, identical in nature 
 with the phantom of the house or of the corpse's head arising
 
 CHAP. I.] OF ILLUSION. 221 
 
 in a person suffering from hallucination, with the semblance 
 of cutaneous stings or of nasal tingling arising in the hypnotized 
 person or somnambulist. Between the idea and the halluci- 
 nation there is no other difference than that between the 
 germ and the full-grown vegetable or animal. 
 
 We have but to look at cases of mental disease to see the 
 germ develop itself, and obtain the proportions denied it in 
 the normal state. Let us examine in turn the words and 
 images which make up our ordinary thoughts. In the normal 
 state we think by words mentally heard, read, or pronounced, 
 and what passes through our minds are images of certain 
 sounds, certain letters, or certain muscular and tactile sensa- 
 tions of the throat, the tongue, and the lips. Now it is suffi- 
 cient for these images, and especially for the first of them, to be- 
 come exaggerated for the patient to have hallucinations of 
 hearing, and to believe that he hears voices. " In the midst of 
 my fever," says Mme. C.,* " I perceived a spider hanging 
 from the ceiling over my bed. A mysterious voice told me 
 to catch the spider. As I was afraid of the insect, I caught 
 it with the corner of the sheet. After many efforts I rose, 
 and received an order to burn the spider and the sheet to de- 
 liver myself from sorcery, so I set fire to the sheet. My room 
 then became filled with a thick smoke. A mysterious voice 
 
 told me to leave it as quickly as I could Having walked 
 
 about the streets for three or four hours, I heard the mysterious 
 voice, as I passed a pastrycook's, telling me to buy a cake, and I 
 did so. Further on, near a drinking fountain, / was ordered to 
 drink. I bought a glass and drank." Some hours afterwards 
 she found herself near the Baths in the Rue Vendome ; the 
 mysterious voice commanded her to take a bath ; but this same 
 voice proceeded with so much force from the bath that Mme. 
 C. was frightened, and left without venturing into the 
 water. " M. N. was prefet of a large town in Germany 
 which rose in 1812 against the rearguard of the French army, 
 then in retreat." His mind was upset by this ; he imagined 
 himself accused of treachery and dishonored ; in short, he cut 
 his throat with a razor. " As soon as he regained his senses he 
 
 * Baillarger, " Des Hallucinations," p. 14-24, &c.
 
 222 GENERAL MECHANISM OF KNOWLEDGE. [BoOK I. 
 
 heard voices accusing him ; when cured of his wound he heard 
 
 the same voices These voices repeated to him night and 
 
 day that he had betrayed his trust, that he was dishonored, 
 that the best thing he could do was to kill himself. They 
 availed themselves in turn of all the languages of Europe 
 which the patient knew ; only, one of these voices was heard 
 less distinctly than the rest, as it employed the Russian 
 language, which M. N. spoke less readily than the others. 
 M. N. frequently retired alone, the better to hear and listen ; 
 he asked questions, he replied, he became convinced that his 
 enemies by some means or other could guess his inmost thoughts. 
 .... On other matters he reasoned perfectly correctly, all 
 his intellectual faculties were unimpaired, he followed conver- 
 sations on various subjects with the same spirit, knowledge, 
 
 and readiness as before his illness Having returned 
 
 home, M. N. passed the summer of 1812 in a country house, 
 where he received a great deal of company. When conver- 
 sation became interesting he heard no voices ; if it slackened 
 he heard them imperfectly; if he left the company and retired 
 alone the better to hear what these perfidious voices said, he 
 became disquieted and anxious." These hallucinations per- 
 sisted some time after his reason had returned, but they were 
 no longer continuous, and usually occurred in the morning 
 only, soon after rising. " My patient," says Esquirol, " had his 
 attention distracted from them by a very short conversation 
 or reading ; but now he knew as I did what these symptoms 
 were ; he looked on them as a nervous phenomenon, and 
 expressed his surprise at having been their dupe so long." 
 " Nothing is more common," adds M. Baillarger, " than 
 to hear patients complain that- their invisible interlocutors 
 
 tell them a host of things about their own affairs To 
 
 employ the expression of a patient, ' How can they read in 
 one's life as in a book ? ' ' 
 
 Not only may the image of articulate sound, that is to 
 say, of words, but every image of sound may be developed 
 so as to become an internal sensation.* "In 1831, during an 
 outbreak, the wife of a workman, then eight months preg- 
 
 * Baillarger, " Des Hallucinations," p. 9.
 
 CHAP. I.] OF ILLUSION. 223 
 
 nant, saw, as she was attempting to reach her home, her hus- 
 band fall mortally wounded by a bullet ; she was delivered of 
 a child : ten days afterwards delirium set in ; she heard the 
 noise of cannon, the fire of musketry, the whistling of bullets, 
 and fled into the country. She was brought to the Salpfitri- 
 ere, and recovered in about a month." In the next ten years 
 six similar attacks occurred, and in each case the same hallu- 
 cinations were renewed from the outset of the delirium. 
 " The patient on each occasion escaped into the country to 
 avoid the noise of cannon and musketry, and the crashing of 
 windows broken by the shot." In a healthy brain the image 
 of the sounds heard in the outbreak would have been exact- 
 ly reproduced, but very faintly. It might have been driven 
 away and recalled at will. By these two characters it would 
 have been recognized as purely internal, and would have been 
 distinguished from sensation. Here it was reproduced with 
 an intensity equal to that of the sensation and unexpectedly, 
 without act of will, even against the resistance of the will ; 
 thus it no longer differed from the sensation, as we are ac- 
 quainted with it by consciousness. Therefore, it had the same 
 effects and same consequences, and renewed the trouble and 
 terror which the woman, then sound in mind, had experienced 
 during the fighting. 
 
 The same observation is to be made as to other images, 
 and especially as to those of sight. A lady was in great trou- 
 ble at the loss of her husband, and, being a believer in the im- 
 mortality of the soul, constantly thought of him as of a per- 
 son still in existence. " One evening, just as she was going 
 to bed, there being a faint light in the room, she saw her hus- 
 band cautiously approaching her, heard him pronounce some 
 words in a low tone, and felt her hand pressed by that of the 
 departed." Full of doubt and surprise she held her breath, 
 the phantom disappeared, and she found she had been the 
 dupe of an hallucination. " Two persons," says Griesinger, 
 " shortly before an outbreak of madness, had been much given 
 to hunting. In their cases, the delirium turned principally 
 on the adventures of the chase. Another had been read- 
 ing, shortly before falling ill, an account of travels in the Him- 
 alayas, and it was on this subject that his delirium chiefly
 
 224 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 turned." The most obliterated circumstances* of our early 
 years, the least observed and most insignificant incidents of 
 our life, occasionally revive with this monstrous hypertrophy. 
 " I passed my early life at Meaux," says M. Maury, "and of- 
 ten went to a neighboring village called Trilport, situated on 
 the Marne, where my father was building a bridge. One 
 night, in a dream, I found myself carried back to the days of 
 childhood, and playing in this village of Trilport. I saw a 
 man dressed in a kind of uniform, and spoke to him and asked 
 his name. He told me he was called C., and that he was 
 coast-guard there, then disappeared to give place to other 
 persons. I woke up with a start, having the name C. in my 
 head. Was this a pure imagination, or was there really at 
 Trilport a coast-guard named C. ? I did not know, having 
 no recollection of such a name. Some time afterwards, I 
 questioned an old servant who formerly lived with my father, 
 and who had often taken me to Trilport. I asked her if she 
 recollected a person of the name of C., and she told me at 
 once that he had been a coast-guard of the Marne, when my 
 father was building the bridge. Most certainly I had known 
 this, as she did, but the recollection had become effaced. The 
 dream in calling it up had as it were revealed to me what I 
 did not know." So again, Theophile Gautier tells me that 
 once passing before the Vaudeville he read upon the placard, 
 
 " the polka will be danced by M ." This phrase fastened 
 
 itself to him, and he thought of it incessantly, and in spite of 
 himself, by an automatic repetition. After some time it was 
 no longer a single mental phrase, but a phrase composed of 
 articulate sounds, and with an external tone and appearance. 
 This lasted several weeks, and he began to get uneasy, when 
 suddenly the besetting disappeared. There is no normal im- 
 age, even the most ancient, the most enfeebled, the most la- 
 tent, which may not vegetate and develop in this manner, 
 just as there is no grain of poppy-seed, the most insignifi- 
 cant, the most abandoned to hazard, which may not become 
 a poppy. 
 
 * A number of instances are collected by M. Maury. " Le Sommeil," &c., pp. 
 70, 120, 128. See other remarks as to images which, on reviving, become halluci- 
 nations, in De Quincey, " Confessions, &c.," p. 258.
 
 CHAP. I.] OF ILLUSION. 2 2$ 
 
 For this reason, if we wish to understand the mental pro- 
 cess excited by the image in its reduced and abortive state, 
 we must examine the mental process excited by it in its state 
 of fulness and freedom. We must imitate the zoologists, 
 who, to explain the structure of some useless bony excres- 
 cence, prove by the comparison of neighboring species that it 
 is a rudimentary limb ; or the botanists, who, by increasing 
 the nourishment of a plant, change its stamens into petals, 
 and so prove that the ordinary stamen is an altered and abor- 
 tive petal. By similar comparisons, and from analogous hy- 
 pertrophies, we discover that the image, like the sensation it 
 repeats, is, in its nature, hallucinatory . Thus the hallucina- 
 tion, which seems a monstrosity, is the very fabric of our men- 
 tal life. Considered in relation to things, sometimes it cor- 
 responds with them, and then constitutes normal external 
 perception ; sometimes it does not so correspond, and then, 
 as for instance, in dreams, somnambulism, hypnotism, and dis- 
 ease, it constitutes false external perception, or hallucination 
 strictly so called. Considered in itself, sometimes it is com- 
 plete and perfectly developed, as happens in the two prece- 
 ding cases ; sometimes it is repressed, and remains in a rudi- 
 mentary state ; as happens in the cases of ideas, conceptions, 
 representations, recollections, previsions, imaginations, and all 
 the rest of the operations of the mind. 
 15
 
 226 GENERAL MECHANISM OF KNOWLEDGE. [CHAP. II. 
 
 CHAPTER II. 
 
 OF RECTIFICATION. 
 
 I. IT now remains for us to study this abortion and its 
 different stages. The reader must here revert to the theory 
 before explained of antagonist reductives.* When alone, and 
 in silence, reclining in a chair, I abandon myself to reverie, 
 and when, by the obliteration of ordinary sensations, the in- 
 ternal phantasmagoria becomes intense, if sleep draws on, my 
 precise images end by exciting actual hallucinations. At this 
 moment a slight touch arouses me, the images become un- 
 done ; the imaginary sounds lose their tone and sharpness ; 
 the colors fade ; the outlines become vague, and the hallu- 
 cinatory process is proportionately checked ; the landscapes, 
 houses, and figures I dreamed of are only seen imperfectly 
 and through a mist ; they seem to lose their solidity and con- 
 sistence. So far, there is nothing remarkable. We knew 
 that the two great departments of the nervous system, that 
 in which sensations take effect, and that producing images, 
 are antagonistic in other words, that sensations become fee- 
 ble as images become strong, and vice versd, ; from which it 
 follows that the waking state, as it draws to a close, confers 
 the ascendancy on images by taking it from sensations, and 
 that the close of sleep deprives images of their ascendancy by 
 restoring it to sensations. But here a new phenomena is dis- 
 closed : not only does the phantom grow pale, but it ceases 
 to appear a real object. It was pronounced external, it is 
 pronounced internal. While we preserve our mental health, 
 we recognize the figure for what it is that is to say, for a 
 simple phantom, a pure semblance, a representation, an idea. 
 And this recognition is made, even when it remains precise, 
 
 * Part I. hook ii. chap. i. pp. 53 et seq.
 
 CHAP. II.] OF RECTIFICA TION. 
 
 colored, possessed of relief, founded on intact images. In 
 fact, those painters who have the clearest imagination, those 
 who paint a whole portrait from memory* Horace Vernet, 
 who painted elaborate uniforms from his head are not sub- 
 ject to hallucinations ; they do not confound their mental rep- 
 resentations with external objects ; with exceptions, they all 
 declare that, as far as they are concerned, these representa- 
 tions are invariably mental. Here, in fact, comes into play a 
 mechanism of universal application in our intelligence. A 
 general law governs all our representations, from the most ab- 
 stract to the most sensible. We cannot conceive a figure as 
 having three sides and at the same time as having four. We 
 cannot imagine a surface as blue and at the same time as red. 
 We cannot perceive our right hand as hot and at the same time 
 as cold. When two contradictory representations come in con- 
 tact, the first is altered by the second, and this alteration con- 
 stitutes what we call in ordinary language a partial negation. 
 The two together thus form a complex representation, with 
 two periods: in this compound the second negatives the first, 
 on one point or another; and the alteration so produced va- 
 ries in magnitude and differs in nature, according to the kind 
 of the two representations thus united and in conflict. 
 
 Observe the simplicity of the mechanism. It consists 
 solely in the attachment of a contradictory representation. 
 By this attachment, the first become affected by a negation 
 in other words, contradicted in some particular respect, some- 
 times as an external and real object, sometimes as an actual 
 or present object, and this operation causes it to appear, some- 
 times as an internal and imaginary object that is to say, as 
 a simple representation and pure phantom sometimes as a 
 past or future event that is to say, as a recollection or 
 prevision. 
 
 II. To convince ourselves of this, let us consider some ex- 
 amples, those which served to explain the appearance will also 
 serve to explain the rectification. Take the case of a clever 
 actress imitating grief; in her presence we almost attain il- 
 lusion ; an unaccustomed or impassioned spectator actually 
 
 * The testimony of Horace Vernet himself.
 
 228 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 attains it ; as, for instance, the American soldier on guard at 
 the theatre when Othello was played, who cried out, " It shall 
 never be said that a wretched negro killed a white woman 
 while I stood by ; " on which he levelled his piece at the ac- 
 tor, and put a ball through his arm. We are not carried away 
 to this extent, but when a play is very good, in close imita- 
 tion of modern life, and, especially, at a first representation, 
 suppressed exclamations, involuntary laughter, a hundred 
 little gestures, show the emotion of the audience. The rea- 
 der may observe this in himself when he sees for the first time 
 some new comedy of Dumas the younger ; twenty times in 
 an act we have a minute or two of complete illusion ; some 
 true, unexpected phrase, supported by the appropriate ges- 
 ture, accent, and surroundings, leads us up to it. We are 
 distressed or enlivened ; we are on the point of rising from 
 our seats ; then, of a sudden, the sight of the footlights, of 
 the audience at the side, some other incident, recollection, or 
 sensation, stops us and keeps us in our place. Such is the 
 illusion of the theatre, incessantly upset and reviving; in this 
 the pleasure of the spectator consists. His emotions of pity 
 and aversion would be too powerful, if they lasted ; their 
 sharpened point is blunted by incessant rectification.* At 
 one moment he believes, then he ceases to believe ; then 
 again begins to believe, then again ceases to believe ; each 
 of these acts of belief ends in a denial, and each of these bursts 
 of sympathy culminates in an abortion ; thus, a series is made 
 up of checked beliefs and weakened emotions; we say, in turn, 
 " Poor woman, how unfortunate she is ! " and almost immedi- 
 ately, " But she is only acting, how well she plays her part ! 
 In other words, we imagine her as heartbroken, and a mo- 
 ment after as calm ; the two representations contradict one 
 another, and, as the second is fortified with more supports, 
 more closely connected with the aggregate of our former ex- 
 perience, and backed up by the body of all our general judg- 
 ments, the first is negatived, altered and repressed till the 
 moment when the incidents and recollections which support 
 
 * Stendhal, " Racine and Shakspeare."
 
 CHAP. II.] OF RECTIFICATION. 229 
 
 its rival disappear with its rival, and permit it again to assume 
 a momentary ascendancy. 
 
 Let us now take the second and less familiar instance. 
 We plunge halfway into water a straight hard stick, and it 
 appears to be crooked. It is impossible for it not to appear 
 so to us ; the laws of optics and vision compel us so to see it. 
 But we recollect that the water is soft and could not bend 
 the wood, and that in twenty other instances, other sticks 
 plunged halfway into water have undergone the same altera- 
 tion of appearance. We conclude that in this instance also 
 the curvature is but apparent ; we assure ourselves of this 
 by drawing out the stick and rinding it still straight. Here 
 is a rectification ; in what does it consist ? Even after our 
 correction, if the stick be again plunged halfway into water, 
 we shall still see it crooked. In other words, to our visual 
 sensation is joined'an associated perception that of distance 
 and form. In other words, again, we imagine the special 
 tactile sensation which corresponds in general to this visual 
 sensation, and which would be given us by a really crooked 
 stick. In this respect our associated perception is mislead- 
 ing. But, by means of former experiments we have made, 
 and of the general laws we are acquainted with, we pro- 
 nounce it misleading, and represent the stick as straight ; 
 in other words, we imagine a different tactile sensation, that 
 which would be given us by a stick 'really straight. In this 
 way we couple to the first image a second contradictory 
 image, and the first is at once negatived.' 
 
 So is it with the person who refers feelings of tingling 
 to a leg he has lost, and so, again, with the person subject 
 to hallucination but sane, who, like Nicolai, or the patient 
 mentioned by Bonnet, sees figures of persons passing through 
 his room. Such a patient has proved, by the test of the 
 other senses, that these figures correspond to nothing solid. 
 He bases his rectification on the testimony of all persons 
 present, and on the accordance of all natural probabilities. 
 He knows that in the place where he sees a human figure 
 there is nothing more than a wall hung with green paper. 
 In other words, the image of the wall so hung with green 
 paper comes in conflict with the sensation of a human figure
 
 230 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 in apparently the same place ; and the image, by simply 
 coupling itself with the sensation, negatives the sensation. 
 This is why the sick man preserves his reason, why he re- 
 frains from addressing the phantoms, why he seats himself 
 on the chair in which they appear seated, in short, why he 
 knows that he is ill, just as the person who has lost a limb 
 .knows he has lost it, and does not attempt to rub the absent 
 foot in which he appears to feel the tingling. Such is the 
 power of the contradictory image ; it forms a couple with the 
 contradicted sensation, and, while this coupling lasts, the 
 persisting contradiction checks the hallucination, if not at 
 its first stage, at all events at its second. 
 
 III. Here a distinction must be drawn : for the contra- 
 dicted representation may have several degrees, from ex- 
 treme dulness and feebleness up to complete energy and 
 precision, and, further still, up to the abnormal exaggeration 
 which transforms it into sensation. In the normal state, 
 while we are awake, our images remain more or less vague 
 and colorless ; even in intense reverie, the figures we imagine, 
 the tunes we hum mentally, have not the clearness of the 
 figures we see with our open eyes, or of the tunes which reach 
 our ears from a musical instrument ; the image of a visual 01 
 auditory sensation is but the feeble echo of that sensation. 
 But in illness the image becomes exaggerated till it trans- 
 forms itself into a complete sensation. All the hallucinations 
 termed* psycho-sensorial are of this kind ; the evidence of 
 sane persons suffering from hallucinations, and the actions of 
 insane persons so suffering, agree as to this. To the same class 
 belong the hallucinations which precede sleep and of which 
 dreams are composed ; any one of us may observe in his 
 own case the spontaneous transformation by which, as sleep 
 gains upon us confused and dull images become vivid and 
 precise, and acquire all the energy, relief, and detail of sen- 
 sations. The numerous examples cited above, have, I think, 
 put this truth out of reach of doubt, and the transformation 
 has been seen to effect itself in two ways, sometimes by a 
 slow progress of which several phases may be followed as is 
 
 * Baillarger, op. cit. ; Maury, op. cit.
 
 CHAP. II.] OF RECTIFICATION. 231 
 
 the case with the reverie resulting in sleep ; sometimes sud- 
 denly, after an obscure incubation, traces of which may fre- 
 quently be discerned as usually happens in cases of hallu- 
 cination.* 
 
 After what has been said of the centres of sensation and 
 the cerebral lobes, the physiological theory of this meta- 
 morphosis is self-apparent. In whatever way the sensation 
 arises, it has as its condition the action of the centres of 
 sensation. In ordinary cases this action is produced by 
 the disturbance of the nerves. But, if otherwise produced, 
 it will arise without the medium of the nerves, and we shall 
 have a true sensation, that of a green table, that of the tones 
 of a violin, without any table or any violin having acted on 
 our eyes or ears. Now, setting aside the medium of the 
 nerves, we find two cases in which the centres of sensation 
 come into play. Sometimes, when they have been set in 
 action by the nerve they spontaneously persist in this action, 
 and repeat it of themselves several times after the nerve has 
 ceased to act ; this being notably the case with the halluci- 
 nations following the prolonged use of the microscope, when 
 the micrographist, resting his eyes on his table or paper, sees 
 a few inches in front of him small gray figures which persist, 
 become effaced and revive again, some four or five times, 
 continually growing paler and feebler. Sometimes the cen- 
 tres of sensation come into play by a reflected shock when 
 images, strictly so called, excite them to action. Usually, it 
 is the sensation which excites the image, and it is the trans- 
 mitted action of the centres of sensation which is repeated 
 in the cerebral lobes or hemispheres: here, on the contrary, 
 it is the transmitted action of the hemispheres which is re- 
 peated in the centres of sensation, and the image which ex- 
 cites the sensation. This is probably the case in hypnogogic 
 and psycho-sensorial hallucinations. 
 
 If I may be permitted a homely illustration let us con- 
 ceive a bell-rope, the nerve, a simple conductor, attached * :/ 
 a large bell, the centre of sensation ; when the rope is pulled 
 
 * See Part I. book ii. chap. I. Especially the story of the gendarme S., p. 67, 
 ante.
 
 232 GENERAL MECHANISM OF KNOWLEDGE. [BooK I. 
 
 it causes the bell to toll ; here we have the sensation. This 
 bell, thanks to an imperfectly understood mechanism,* com- 
 municates by different threads, the fibres of the optic thalami 
 and the corpora striata, with a system of little bells which 
 make up the hemispheres, and whose mutually excitable ring- 
 ings exactly repeat its sounds with their pitch and tone ; these 
 ringings are images. When the bell tolls it sets in motion 
 the ringings, and when the tolling is over the ringings con- 
 
 - O O * O O O 
 
 tinue, grow weaker, and are obliterated, but are capable of 
 resuming and regaining all their primitive, energy, when a 
 favorable circumstance permits the persisting sound of one 
 or two of the little bells to cause all the rest to ring in unison. 
 Usually, the large bell is set in motion by the rope. But 
 sometimes, when the rope has ceased to pull, the bell contin- 
 ues to toll. Sometimes again it recommences to toll of its 
 own accord. Lastly, sometimes, the little bells, which, as a 
 general rule, receive their motion from it, transmit their mo- 
 tion to it ; and we know the principal conditions of these' 
 singular effects. In hallucinations of the microscope the large 
 bell has been so powerfully and constantly set vibrating in 
 one direction, that its mechanism continues to act even when 
 the cord is motionless. In dreams and hypnogogic halluci- 
 nations, the string is relaxed ; it no longer communicates ; 
 the long employment of the waking hours has rendered it 
 unfit for use ; external objects may pull, but it no longer 
 causes the bell to toll ; on the other hand, at this moment, 
 the little bells whose vibrations have been constantly repress- 
 ed while we were awake, and whose pullings have been an- 
 nulled by the more powerful pulling of the bell-rope, regain 
 all their power, they ring more strongly and pull effectu- 
 ally; their disturbance excites a corresponding disturbance 
 in the large bell, and the life of man is thus found to be di- 
 vided- into two portions, the waking state, in which the large 
 bell rings by means of the cord, and sleep, in which it rings 
 by means of Jthe little bells. In abnormal hallucination 
 the cord still pulls, but its effort is overcome by the greater 
 
 * The anatomical difficulties are too great. See, however, the great work of 
 Lhuys, " Recherches sur le Systeme Nerveux," with plates.
 
 CHAP. II.] OF RECTIFICATION. 233 
 
 power of the little bells; and various causes a flow of 
 blood, inflammation of the brain, haschich all the circum- 
 stances capable of rendering the hemispheres more active 
 produce this mischance ; the vibrations of the little bells, which 
 in the normal state are more feeble than the action of the 
 cord, have become stronger, and the ordinary equilibrium of 
 the functions is upset, from one of them having assumed an 
 ascendancy to which it is not entitled. 
 
 IV. Having settled this, we see what may be the effect 
 of the contradictory image and sensation on images so ex- 
 aggerated. In order that the contradictory sensation may 
 arise and negative them, it is necessary for the images to lose 
 their exaggeration, to cease to excite sensations, and to return 
 to the state of simple images ; in other words, the little bells 
 must cease to set the great bell tolling. Such is the case 
 when we wake up ; just now, in a dream, I imagined myself 
 to be in a burning atmosphere ; I wake up and have the sen- 
 sation of ordinary temperate warmth ; this sensation of com- 
 parative cold contradicted the image of the sensation of heat, 
 and, by means of this coupling, the image appeared in its 
 actual state, that is, as a simple image. But if, through any 
 derangement, the little bells continue to set the great bell 
 tolling, which is what happens with the sufferer from hallu- 
 cination who perceives an absent person, if the great bell 
 repeats its tolling of its own accord, which is what happens in 
 the hallucinations following the prolonged use of the micros- 
 cope, the result is different. The patient may know the phys- 
 iological cause of the error, may base his reasoning on the 
 evidence of surrounding persons, may prove by the aid of the 
 other senses that the phantom is but a phantom, still he con- 
 tinues to see it. In Nicolai's case the figures continued 
 to pass through his room, and the little gray specks persist 
 in appearing on the blank paper placed before the micrograph- 
 ist. In fact, the contradictory sensation is no longer pro- 
 duced. The paper ceases to give the sensation of white at 
 the place in which it appears to be covered with gray patches, 
 and the green or brown wall of the room ceases to give the 
 sensation of green or brown in the places at which the figures 
 come in the way. The optic nerve is impressed by the white
 
 234 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 rays of the paper or the green and brown rays of the wall, 
 but ineffectually so ; its action is no longer communicated to 
 the centre of sensation. The place is occupied ; another ac- 
 tion is set up and persists there, resisting all the solicitations 
 of the nerve. 
 
 There remains, then, a single corrective, the image strictly 
 so called, the image of the green or brown wall which Nicolai 
 attempted to picture to himself in the place of the phantoms, 
 the image of the plain white paper which the micrographist 
 represents to himself in the place of his paper spotted with 
 gray outlines. But this image remains a simple image; it 
 does not become exaggerated to the extent of setting in mo- 
 tion the centre of sensation and transforming itself into a sen- 
 sation. Nicolai observed a very marked difference between 
 the figure of a person as it appeared to him, and the same 
 figure as he pictured it a moment after by an effort of atten- 
 tion and memory. The first invariably seemed an external 
 thing, the second an internal, a simple mental representation ; 
 in fact, in the first case, the centre of sensation was operating, 
 and, in the second, it did not operate. Hence it follows that 
 the correction afforded by the contradictory image is limited. 
 The person under hallucination, even when sane, continues 
 to see his phantoms as external ; in fact, in his case, the cen- 
 tres of sensation operate precisely as if he had before his eyes 
 real persons. Although the bell-rope does not pull, the large 
 bell tolls as usual ; the little bells of the hemispheres are pow- 
 erless ; the contradictory image can do nothing against the 
 sensation itself. It has no effect except upon the consequence 
 of the hallucinations so produced. If it were wanting, these 
 consequences would be madness ; the patient would imagine 
 and reason about his phantoms, as he imagines and reasons 
 about external objects : the micrographist would try to rub 
 out the gray patches on his paper, Nicolai would have spoken 
 to the imaginary friends who came to visit him, and have 
 asked them how they were. Here it is that the contradictory 
 image, supported by the whole troop of general convictions, 
 intervenes with success. Against sensations, that is to say 
 against a state of the sensory centres on which it has no hold, 
 it was powerless. Against ideas, representations, and reason-
 
 CHAP. II.] OF RECTIFICATION. 23$ 
 
 ings, all founded on images resembling it, and situated like it 
 in the hemispheres, it is effective. Rectification, of no effect 
 in the first stage, becomes sufficient in the second. 
 
 V. Let us now study the contradicted image, as it remains 
 in the normal state of wakefulness, that is to say when it does 
 not set in motion the centres of sensation, and does not be- 
 come exaggerated to the extent of being transformed into a 
 sensation. In this state it constitutes, in the first placeman 
 event of capital importance which we term recollection. 
 
 Let the reader recall some recollection of his own, and 
 abandon himself to it, especially if it be recent, vivid, and 
 prolonged ; he will thus obtain a better insight into its nature. 
 A month ago I spent three hours on the pier at Ostend, en- 
 gaged in watching the sun which was setting in a clear sky, and 
 at this present moment I recall without difficulty the level 
 street, the dyke paved with reddish bricks, the vast extent of 
 glittering water, all the incidents of my walk, the sailor, and 
 the two loungers I spoke to, my long reverie at the pier-head, 
 from whence I watched the declining day, and the variations 
 of the moving sea, the luminous twinkling of the waves, their 
 bluish hollows striped with russet tints, all the splendor of the 
 vast watery carpet, undulating and displaying itself with its 
 changing colors, like a silk of Jordaens. These are images, 
 that is to say spontaneous revivals of anterior sensations, and, 
 like all images, they admit of an illusion when they become 
 intense and clear. In fact, there are moments when we be- 
 lieve for a half-second that we see real objects ; I experienced 
 this just now, and artists, writers, all who have precise and 
 lucid memories, are well aware of this; a nervous person who 
 has undergone a surgical operation, or met with some serious 
 accident, bears the same testimony ;* the keenness of the rec- 
 ollection is so great that he will sometimes grow pale and utter 
 a cry. In this state we forget ourselves, we lose conscious- 
 ness of the present ; we feel, before the internal phantasmago- 
 ria, as we do at the theatre when a good piece is being played. 
 We become for the moment dupes of the half-dream, then 
 cease to be so, then again become so, then again cease to be 
 
 * See Part I. book ii. chap, i, p. 42.
 
 236 GENERAL MECHANISM OF KNOWLEDGE. [KooK I. 
 
 so : thus an incessantly interrupted series is formed of beliefs 
 incessantly denied, and of illusions incessantly set right. But 
 here the denial and the correction result in a new and mar- 
 vellous effect, whose mechanism is so simple that we neglect 
 to observe it, one of infinite extent, and which, by its adjust- 
 ment to things, constitutes memory. At present, by virtue of 
 this correction, the present image appears tome as a past sen- 
 sation ; this, strictly speaking, is recollection. No doubt, a 
 moment afterwards, on reflection, I shall know that all there 
 is in my mind is a present image, that this vivid internal half- 
 sight of blue waves spangled with gold and set in a semicircle 
 of white sand, is entirely present and internal. But this will 
 be an ulterior and supplementary correction, a rectification 
 upon a rectification, a second and last stage in the series of 
 reductions through which the image passes in order finally to 
 appear as it actually is. At the first stage, at the moment at 
 which we are, it still appears as a sensation, not as a present 
 sensation, as happens in hallucination proper and dreams, but 
 as a past sensation situated at a greater or less distance from 
 the present moment, as the sensation of certain glittering 
 blue and certain dead white, placed in between my present 
 sensations and other still more distant ones. And in fact, 
 when a lengthy series of well-connected sensations arises 
 within us, when we mentally live over the incidents of a day's 
 travel, we believe ourselves to be confronted with real, though 
 distant facts. The images of sounds, colors, pains, pleasures, 
 which are nothing more than present images, but which cor- 
 respond to anterior sensations, seem, as they pass in review 
 before us, our anterior sensations themselves. All there is 
 within us is the present echo of a distant impression ; never- 
 theless, what we affirm is not the echo, it is the distant im- 
 pression, and by an admirable correspondence we affirm it 
 truthfully. 
 
 Such is the crude fact, and we see that recollection, like 
 external perception, is a true hallucination, that is to say, 
 an illusion which results in a cognition. It is an illusion, since 
 the present image which constitutes it is taken, not for a 
 present image, but for a past sensation, thus appearing other 
 than it really is. It is a cognition, since in the past, and
 
 CHAP. II.] OF RECTIFICA TION. 237 
 
 precisely at the proper place there, a sensation is met with 
 exactly similar to the affirmed sensation, and our judgment, 
 which is, in itself and directly, false, is thus found, indirectly 
 and by coincidence, to be true. Here again nature deceives 
 to instruct us. Just as in external perception we have seen 
 simple internal phantoms taken for external objects, but by 
 an admirable adaptation corresponding to the presence of 
 real external objects, so in memory we see simple present 
 images taken for past sensations, but corresponding, by as 
 beautiful a mechanism, to the anterior presence of real sen- 
 sations. Thus, the first repression which the image under- 
 goes, and which checks the complete hallucination in which 
 the image would naturally have resulted, opens to us a new 
 world, that of time and space. In this intermediate state, 
 partially abortive and partially complete, half rectified and 
 half hallucinatory, the image resembles some organ* checked 
 in the midst of its development, a special product, utilised 
 for special functions, and sometimes for functions of the 
 highest order. This is the case here, since here we owe to it 
 our knowledge of the past, and, consequently, our previsions 
 of the future. 
 
 Here again we seize in the act an illusion of conscious- 
 ness. When a psychologist observes an act of memory, he 
 begins by remarking that it is a cognition, and postulating 
 that every cognition implies two terms, a subject knowing, 
 and an object known, he says that there are two terms in- 
 volved in recollection, the past sensation and the knowledge 
 we have of it. If he then goes on to examine this knowledge 
 he is tempted to take it for a simple naked act of the mind, 
 deprived of all sensible character, and indeed of all character, 
 except its connection with the past sensation which is its 
 object. He is consequently disposed to regard this cognition 
 as a pure act of attention, an act unique in kind, incapable 
 of comparison with any other, whose essence, purely spiritual, 
 consists solely in putting us in communication with our past 
 life. But if this act appears to be pure and spiritual, it is 
 
 * As, for instance, the stamens and other parts of a flower, which are petals 
 checked in the course of their development.
 
 238 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 because it is empty; he has himself emptied it by taking 
 from it all its characters, to set them apart and form from 
 them the object. In fact, that which constitutes recollection 
 or act of memory is the present image which a past sensa- 
 tion has left in us, an image which we find affected with an 
 apparent recoil, and which seems to us the sensation itself, 
 By cutting away from the image all that constitutes it, and 
 all the positive properties by which it resembles the sensa- 
 tion, and referring them to the sensation itself, we turn recol- 
 lection from a full act into an abstract one ; as this act no 
 longer comprises any thing, nothing can be said about it ; we 
 name it, and there is science completed. Here, as with ex- 
 ternal perception, we have made the mistake of splitting in 
 two our internal act, and here, as with external perception, 
 we are led to do this from its having two aspects. On the 
 one hand, as it passes within us, and at the present moment, 
 it is our present act ; on the other hand, as it is hallucinatory, 
 it seems to us, in external perception, an object other than 
 ourselves, and, in recollection, a sensation not actually present. 
 It was necessary to recognize its hallucinatory nature to un- 
 derstand that it is single, and that while in reality internal and 
 present, it is in appearance only that it is an external thing, 
 or past event. Until this remark is made, we divide it into 
 an internal act and known object. In this operation the act 
 loses all that the object gains ; a transfusion of characters is 
 effected to the detriment of the first and to the advantage of 
 the second. Thereupon consciousness, self-deceived, declares 
 that in recollection, as in external perception, the mind per- 
 forms an act sui generis, simple, irreducible to any other, 
 mysterious, marvellous, ineffable ; and thus a new thread is 
 added to the constantly broken and constantly repaired cob- 
 web, in which the moral sciences have been entangling them- 
 selves for so many ages. 
 
 VI. Let us now examine more closely the apparent recoil 
 which the image undergoes. I am quietly stretched in the 
 shade of a hedge, listening to the chirpings of the birds, and 
 the prolonged buzzing of the insects flitting about in the 
 summer air ; suddenly a distant rolling is heard ; it increases, 
 and comes on me with a furious grinding and growling noise
 
 CHAP. II.] OF RECTIFICA TION. 239 
 
 like a peal of thunder ; I jump up, a railway train is passing ; 
 I had been, without knowing it, within ten paces of the line. 
 The hoarse roll grows weaker and becomes effaced ; listen as 
 I may, I hear nothing but the indistinct murmur of the 
 country and the monotonous rustling of leaves shaken by 
 the wind. But in this silence the image of the resounding 
 noise persists, disappears, and reappears, till some other pre- 
 occupation or some other vivid emotion drives it from the 
 stage to make way for a new actor. Now, at each of its re- 
 entries, the image finds itself in conflict with the then present 
 group of sensations. If, in conformity to its natural ten- 
 dency, it appeared as a sensation, there would be a contra- 
 diction between it and this group. In fact, I cannot repre- 
 sent myself as at the same time tranquil, reclining, listening 
 to the vague little sounds, and as startled, springing up, 
 deafened by a violent noise ; the first representation is in- 
 compatible with the second ; in ordinary language, the one 
 negatives the other. But this negation is on one point only ; 
 the one negatives the other only as being its contemporary. 
 The ordinary hallucinatory process is checked in this point 
 only, since a negation on this point only is sufficient to enable 
 both to subsist : there is a minimum of repression propor- 
 tioned to a minimum of antagonism. Consequently, in other 
 respects, the hallucinatory process takes effect ; the image, 
 not being negatived as a sensation, but as a present sensa- 
 tion, appears as a sensation which is not present, and the only 
 result of the negation it undergoes is to reject it, as far as 
 appearance goes, out of the present. 
 
 Why is this rejection a recoil? And why does the appar- 
 ent sensation seem to take a backward rather than a forward 
 direction ? It must be observed that every image, much 
 more, then, every series of images, has a certain duration ; for 
 every image repeats a sensation, and we have seen that the 
 shortest sensations, even those we consider instantaneous, are 
 series of elementary sensations, themselves composed of still 
 more elementary ones. Hence it follows that every image 
 occupies a portion of time, and has two extremities an ante- 
 rior one joining on to preceding events, and a posterior one 
 joining on to subsequent events: the first one attached to
 
 240 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 the past, the second attached to the future. And thus, a 
 simple sound, a color perceived by a momentary glance, a 
 brief sensation of heat, smell, or contact, whose successive 
 parts we do not distinguish, is similar in nature to a drive or 
 walk whose successive parts we do distinguish, and every sen- 
 sation, consequently every image, possesses, like every series 
 of sensations or imag-es, its beginning and its end. Thus, 
 when hearing a note on the piano I recall the preceding note, 
 the case is similar to that in which, when thinking over the 
 events of the day, I recall the events of yesterday. When the 
 present sensation and the image of the preceding sensation 
 come into conflict they have each two extremities ; neither 
 one nor the other are instantaneous and simple ; they are 
 two wholes composed of successive elements. This is why 
 the repulsion by which the first acts on the second is itself 
 an aggregate of repulsions repulsions which are unequal, 
 and which, by their distribution, determine the direction in 
 which the apparent rejection takes place. 
 
 Let us first consider the two extremities of the sensation, 
 or of the present, in their relation with the posterior extrem- 
 ity of the image, or of the past. The posterior extremity of 
 the past coincides with the anterior extremity of the present ; 
 here then the contradiction, and consequently the repulsion, 
 has no effect. But it is at the greatest possible distance from 
 the posterior extremity of the present ; here then the -con- 
 tradiction, and consequently the repulsion, is at its maximum. 
 Hence we see that the rejection must take place in a 
 backward direction, so that under the pressure of the 
 present sensation the posterior extremity of the image 
 seems to coincide with the anterior extremity of the present 
 sensation, and to separate itself as far as it can from the pos- 
 terior extremity of the present sensation. Let us now con- 
 sider the two extremities of the past in their relation with 
 the anterior extremity of the present. The anterior extrem- 
 ity of the present coincides with the posterior extremity of 
 the past ; here then the contradiction, and consequently the 
 repulsion, is of no effect. But it is at the greatest possible 
 distance from the anterior extremity of the past ; here then 
 the contradiction, and consequently the repulsion, is at its
 
 CHAP. II.] OF RECTIFICA TION. 241 
 
 maximum. Hence we see that, in the whole rejection into the 
 past, the anterior extremity of the sensation must apparently 
 coincide with the posterior extremity of the image, and ap- 
 pear at the greatest possible distance from the anterior ex- 
 tremity of the image. In cases of prevision, the inverse takes 
 place. According as the relation of the extremities of the 
 image with the extremities of the actual sensation is different, 
 the balance inclines in one direction or the other, and we may 
 at any moment witness in our own cases these remarkable 
 changes of place. 
 
 I meet casually in the street a person whose appearance I 
 am acquainted with, and say to myself at once that I have 
 seen him before. Instantly the figure recedes into the past, 
 and there wavers about vaguely without at once fixing itself 
 in any spot. It persists in me for some time, and surrounds 
 itself with new details. " When I saw him he was bare-headed, 
 with a-working jacket on, painting in a studio ; he is so-and-so, 
 of such-and-such a street. But when was it ? It was not 
 yesterday, nor this week, nor recently. I have it ; he told me 
 that he was waiting for the first leaves to come out to go into 
 the country. It was before the spring. But at what exact 
 date ? I saw, the same day, people carrying branches in the 
 streets and omnibuses : it was Palm Sunday ! " Observe the 
 travels of the internal figure, its various shiftings to front and 
 rear along the line of the past ; each of these mental senten- 
 ces has been a swing of the balance. When confronted with 
 the present sensation, and with the latent swarm of indistinct 
 images which repeat our recent life, the figure has first re- 
 coiled suddenly to an indeterminate distance. Then, completed 
 by precise details, and confronted with all the shortened images 
 by which we sum up the proceedings of a day or a week, it has 
 again receded beyond the present day, beyond yesterday, the 
 day before, the week, still further, beyond the ill-defined mass 
 constituted by our recent recollections. Then something said 
 by the painter was recalled, and it at once receded again be- 
 yond an almost precise limit, which is marked by the image of 
 the green leaves and denoted by the word spring. A mo- 
 ment afterwards, thanks to a new detail, the recollection of 
 the branches, it has shifted again, but forward this time, not 
 16
 
 242 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 backward ; and, by a reference to the calendar, is situated at 
 a precise point, a week further back than Easter, and five 
 weeks nearer than the Carnival, by the double effect of the 
 contrary impulsions, pushing it, one forward and one back- 
 ward, and which are, at a particular moment, annulled by one 
 another. Now let us place this image in an inverse situation, 
 that is to say in such a manner that its anterior, and no longer 
 its posterior, extremity may join on to the posterior ex- 
 tremity of present sensations. At once, instead of sliding to- 
 wards the past, it slides towards the future. This is what hap- 
 pens if I calculate when I shall see my friend again. The 
 more this shifting is repeated at the successive contact of the 
 previsions which the figure meets with in its way, the more 
 does it seem to fly forward and to become distant. Finally, 
 it becomes placed ; but its precise place is attained only by its- 
 projection being stopped. A new detail must intervene to 
 give it, after successive movements in advance, a movement 
 backwards, which will fix and intercalate it between two fu- 
 ture periods. " I shall see my friend, not to-day, not to-mor- 
 row, but the day after to-morrow, not the day after to-mor- 
 row in the morning, but in the afternoon, when I leave the 
 library, before I go home to dinner." In this perpetual play, 
 which has ceased to attract our attention because we live in 
 it, the shifting image is actually contemporary with the sen- 
 sation or image which causes it to shift, but nevertheless seems 
 to be situated before or after it. In fact, one over-rides the 
 other ; in appearance, they are placed end to end ; and this 
 marvellous illusion which, out of two really simultaneous 
 events, forms two events apparently posterior or anterior to 
 one another, is the mechanism by which our sight extends 
 out of the present to attain the past and the future. 
 
 VII. The last state of the image now remains to be con- 
 sidered, that state in which it ceases to appear, not only as an 
 actual sensation, but as a past or future sensation. In this 
 case we pronounce it to be a simple image, and the rectifica- 
 tion is complete. Of this kind are all the internal events we 
 term pure conceptions, pure imaginations, and generally pure 
 ideas. This is what happens when we read or hear a sentence, 
 when we dream or form projects. We then picture to our-
 
 CHAP. II.] OF RECTIFICA TION. 243 
 
 selves, more or less clearly and with more or less minuteness 
 of detail, some room, some landscape, certain persons or inci- 
 dents, and, as they pass before our mental vision, we know 
 that they are imaginary, supposititious, and entirely of our 
 own fabrication. In fact, if we expect our perceptions of ex- 
 ternal objects, our recollections and our previsions, the whole 
 web of our thought, during our waking hours, is made up of 
 pure images. When I think of an old time-piece in an ad- 
 joining room, when, by aid of mental words, I follow out a 
 long train of reasoning, when I reflect on what will probably 
 happen if I take certain steps, not only have I in my mind 
 the image of the time-piece, the image of the sounds and vocal 
 movements which my arguments would require, if uttered 
 aloud, the image of the gestures, emotions, and events which 
 my conduct would excite in myself and others, but I am aware 
 too that all these images are simple present images. This 
 time the hallucination is wholly checked ; the internal phan- 
 tasmagoria, repressed the moment it arises, appears only as 
 phantasmagoria, and here the mechanism of the repression is 
 easily detected. 
 
 Two extreme cases present themselves and sum up all the 
 rest. In the first, the image is a reduced and impoverished 
 recollection. We all know that it is in its primitive state 
 a recollection, and a full and circumstantial one. I have 
 seen the time-piece I picture to myself a hundred times ; I 
 have heard or read a thousand or ten thousand times the 
 mental words which pass through my mind ; I have observed 
 thirty or forty times the astonished gesture, the pleased 
 smile or angry accent I imagine ; the proof is that they re- 
 vert to me ; if I know them, it is because I recollect them. 
 But certainly, when I first observed them, I was struck by 
 their accompaniments, and shortly afterwards I could have 
 described their surroundings from memory, the fire-place in 
 the country, where the old time-piece stood when I was a 
 child, the name of the person who made the gesture, the 
 title of the book in which I saw the word. Take, for in- 
 stance, a Latin word, securis. No doubt on the day I learnt 
 this word, I could recall the grammar or dictionary in which 
 I read it, the exact place, the line and page of the dog's-
 
 244 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 eared, blotted school-book. But since then, these circum- 
 stances have disappeared ; repetition and distance have ef- 
 faced them ;* the image which I then situated at a particular 
 spot of my past life, has lost the details which situated it. 
 Now do what I will in shifting it over the whole line of my 
 anterior experience, it does not attach itself to any of the 
 successive links. It is too much worn and blunted ; it has 
 no longer re-entering and salient angles, special and peculiar 
 extremities, fixing it before or after some other distinct recol- 
 lection. I no longer find in it an anterior or posterior ex- 
 tremity which may blend and coincide with the posterior or an- 
 terior extremity of another determinate event. Thus it moves 
 about, in a colorless way ; if I detect its place in the vague dis- 
 tance of childhood, it is by conjecture and reasoning; of itself, 
 it no longer finds a place ; it has no longer antecedent or con- 
 sequent, it is deprived of situation. And, if we look to the 
 future, its position is the same, since its future existence ap- 
 pears subject to certain conditions, among others to my 
 changing will, and since, in the realm of the future, it is still 
 colorless, and capable of intercalating itself as well at one 
 moment as at another of my future experience. On both 
 sides its situation fails it ; it is essentially unstable ; I cannot 
 fix it or affirm it ; thus, it is opposed to preceding affirma- 
 tive judgments, to previsions, and recollections. This is 
 how it happens that when, like them, it undergoes the 
 repression of contradictory sensations it is contradicted, 
 not partially as they are, but absolutely, and cannot appear 
 other than as a sensation without situation, that is, as 
 a sensation simply apparent and destitute of real exist- 
 ence. 
 
 Such is the first case ; let us examine the second, which 
 is just the inverse. Here we have the precise, intense, col- 
 ored representations attained by the imaginations of great 
 artists Balzac, Dickens, Flaubert, Henri Heine, Edgar Poe ; 
 and some of which I have already cited. These artists attain 
 moments of hallucination : but it is for the moment only. 
 M. Flaubert writes to me as to this : " Do not assimilate the 
 
 * See part i. book ii. chap. 2, " Laws of the Obliteration of Images."
 
 CHAP. II.] OF RECTIFICA TION. 24$ 
 
 mental vision of the artist with the state of the man laboring 
 under hallucination. I know both states perfectly ; there is 
 a chasm between them. In strict hallucination there is al- 
 ways fear ; you feel your personality escaping you ; you think 
 you are about to die. In poetic vision, on the contrary, there 
 is pleasure ; it is something which enters into you. It is none 
 the less true that one loses consciousness of where he is." 
 He adds, further on, "This vision frequently completes itself 
 slowly, piece by piece, like the different parts of a decoration 
 are put together , " but frequently, also, it is sudden and " fu- 
 gitive, like the hallucinations preceding sleep. Something 
 passes before your eyes ; you must seize it on the spot, greed- 
 ily." My own experience is in accordance with these re- 
 marks. When the landscape, the moving figure, the gesture 
 and voice of the person begin to rise and become precise, we 
 wait, and hold the breath ; sometimes, then all appears sud- 
 denly ; at other times, slowly, with barren intervals. But, in 
 both cases, what appears is watched for, desired, or at least 
 comprised in the circle of watched-for and desired images, 
 then immediately employed, and put to use by the hand 
 which marks and notes it, consequently followed at once by 
 repressive sensations, in all cases stamped at its origin with a 
 particular character the property of springing up by a per- 
 sonal effort, in a foreseen direction, after a preliminary search, 
 as an internal effect and not as an external impression ; so 
 that after such a burst and dazzling, the habitual sensations, 
 tactile, muscular, or visual have no difficulty in resuming their 
 normal ascendancy, and, combined with the rank of positive 
 recollections, drive back the enfeebled phantom into the in- 
 aginary world. A sequence of very short hallucinations, 
 which, being voluntary, may be and are actually broken and 
 negatived at any moment by the more or less vague percep- 
 tion of the real world, such is the picturesque or poetic vision, 
 very different, as M. Baillarger observes, from strict hallucin- 
 ation, which rises unexpectedly, and without the concurrence 
 of the will, which persists in spite of ourselves, which is devel- 
 oped of its own accord, irregularly, and which seems to us the 
 work of some extrinsic power. In themselves, the two events 
 are similar. But they are contrasted in their antecedents and
 
 246 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 consequents ; the first is the harmonious product of all the 
 united tendencies of the human being ; the second, the 
 exaggerated enlargement of a discordant element, which, 
 like an organ become hypertrophied and subtracted from 
 general life, is developed separately and abnormally to the 
 detriment of the others with whose concordant action it 
 interferes. 
 
 We see now how it is that our ordinary conceptions and 
 imaginations appear to us as such, and do not create illusion ; 
 they are all comprised between two extreme states, and each 
 of these two states includes a peculiarity repressing the illu- 
 sion. Either, as in the ordinary case, they are vague and strip- 
 ped of precise details, in such a way that, cast out of the pres- 
 ent by the contradiction of present sensations, they are want- 
 ing in angles which may fix them in the past and future ; 
 whence it follows that, being deprived of all situation in time, 
 they appear excluded from time, that is to say from real life, 
 and are pronounced apparent, false, and purely imaginary sen- 
 sations. Or, after a series of repeated solicitations, they at- 
 tain the detail and precision of the real sensation, by suspend- 
 ing contemporary sensations and ordinary recollections, but 
 for the moment only, by a fugitive ecstasy, interrupted an in- 
 stant after by a return to the normal state, and then pro- 
 nounced illusory or internal, because the effort of internal will 
 of which it is the result re-arises with it in the memory of the 
 observer. Suppress these repressive peculiarities and the rec- 
 tification which ensues from them ; suspend for some hours 
 or minutes ordinary sensations, and the cohesion of connected 
 recollections, as happens in sleep, whether incipient or com- 
 plete ; let, as then happens, the uncolored and vague image 
 become complete, circumstantial and colored ; that which, in 
 the waking state, would have been pronounced a simple idea, 
 becomes first an hypnagogic hallucination, then an intense 
 dream. On the other hand, prolong this momentary ecstacy ; 
 let it, by an organic accident, be repeated of itself, suddenly, 
 without being watched for or desired, in spite of the will ; you 
 will have hallucinations like those of Nicolai, and, if the pa- 
 tient has not a very strong mind, you will have the visions of 
 a madman, like those shut up in asylums, or of a mystic, like
 
 CHAP. II.] OF RECTIFICA TION. 247 
 
 those of India or of the Middle Ages.* Thus the history of 
 sleep and of madness gives us the key to the history of rea- 
 son, and of the waking state. 
 
 VIII. Here, again, is an illusion of mental optics, which 
 perishes at the touch of analysis. With respect to those con- 
 ceptions and imaginations which we pronounce internal, we 
 have just seen by what repressive mechanism they appear to 
 us as such. Thanks to this repression, they appear to us as 
 they are, that is to say, no longer as external objects or as 
 future and past events, but as events wrongly provided with 
 this false appearance, actually internal and present. I think 
 of a line of poplars, and, as I follow, with closed eyes, the 
 green curtain of waving leaves, pierced here and there by the 
 sky, I know very well that it is internal and present. This 
 knowledge or cognition is called consciousness, since its object 
 is internal and present ; it is thus opposed to cognitions whose 
 object is not present or is not internal ; on this account, we 
 separate it from external perception and from memory, and 
 make of it a distinct department, presided over by a distinct 
 faculty. All this is permissible, and even convenient. But 
 here the error creeps in ; we are duped by the same words 
 and in the same fashion, as with respect to memory and ex- 
 ternal perception ; as a cognition is in question, we wish abso- 
 lutely to find an act of knowledge and an object known ; we 
 picture consciousness as the glance of an internal eye, directed 
 to a present internal event, just as we picture memory as the 
 glance of an internal eye directed to a past event. Meta- 
 phors lend their aid ; in fact, psychologists continually speak 
 of consciousness as of a spectator or internal witness which ob- 
 serves, compares, takes notes on the various conceptions, 
 imaginations, and representations passing in review before it. 
 The truth is that in such a case there are not two events in 
 my mind, my conception on the one hand, and, on the other, 
 an act by which I am acquainted with it, but one single event, 
 my conception itself. We split it in two because it has two 
 phases, the first, in which it appears an external object or past 
 
 * See, among other records, Bunyan's " Autobiography," the " Vita Nuova " of 
 Dante, and the works of Saint Theresa (Tr. Arnauld d' And illy).
 
 248 GENERAL MECHANISM OF KNOWLEDGE. [BOOK I. 
 
 event, curtain of poplar leaves or anterior visual sensation, the 
 second, in which, being rectified, it appears an internal and 
 present event, an optical phantom, then included in ourselves. 
 In this splitting, when we have laid on the one side the phan- 
 tom with all its distinctive characters, we have nothing left to 
 constitute, on the other hand, the act of cognition. This act 
 is empty ; thence it happens that we consider it pure, simple, 
 and spiritual : the mistake is precisely that which we fell into 
 just now respecting external perception and memory. In 
 fact, here as before, the internal event is reduced to the in- 
 ternal conception, representation, or present phantom ; the 
 knowledge that it is such, that is to say present, internal, and 
 visionary, is nothing more than the rectification or negation 
 by which it is excluded from the outer world, from the future, 
 and from the past. 
 
 We can now seize, with a general glance, on the process 
 employed by Nature to create in us our first and principal 
 sources of knowledge. In two words, she creates illusions 
 and rectifications of illusion, hallucinations and repressions of 
 hallucination. On the one hand, with sensations and images 
 combined in clusters according to laws we shall presently see, 
 she constructs within us phantoms which we take for exter- 
 nal objects, in most cases without being misled, since there 
 are, in fact, external objects corresponding to them, some- 
 times, by mistake, since sometimes the corresponding exter- 
 nal objects are not there ; in this way she produces external 
 perceptions which are true hallucinations, and hallucinations, 
 strictly so called, which are false external perceptions. On 
 the other hand, by attaching to an hallucination stronger con- 
 tradictory hallucination, she alters the appearance of the first 
 by a more or less radical negation or rectification ; by this 
 adjunction she constructs repressed hallucinations which, ac- 
 cording to the kind and degree of their miscarriage, sometimes 
 constitute recollections, sometimes previsions, sometimes con- 
 ceptions and imaginations, strictly so called, all of which, when 
 the repression ceases, become transformed, by a spontaneous 
 development, into complete hallucinations. To form com- 
 plete hallucinations and repressed hallucinations, but in such a 
 way that, when awake and in the normal state, these phan-
 
 CHAP. II.] OF RECTIFICA TION. 
 
 toms usually correspond to real things and events, and thus 
 constitute cognitions, this is the problem. We shall see how 
 images and sensations furnish the materials, and how the 
 laws of their origin, revival, and association construct the edi- 
 fice.
 
 250 THE KNOWLEDGE OF BODIES, [BOOK II. 
 
 BOOK II. 
 
 THE KNOWLEDGE OF BODIES. 
 
 CHAPTER I. 
 
 EXTERNAL PERCEPTION AND THE IDEA OF WHICH THE IDEA 
 OF BODY IS COMPOSED. 
 
 I. To begin with the knowledge of bodies. What is there 
 within us when we take cognizance by our sensations of an 
 external body when, for instance, experiencing tactile and 
 muscular sensations of cold, of considerable resistance, of 
 smooth and uniform contact in my hand, I conclude that it 
 is resting on marble ; when, casting my eyes in a certain di- 
 rection and having through the retina a sensation of reddish 
 brown, I conclude that there is a round mahogany table three 
 paces from my eyes ? A phantom or hallucinatory semblance. 
 The reader has already seen the main proof of this.* But 
 the paradox is so great that it will be well to present it anew, 
 adding to it the complementary proofs. 
 
 In order to establish that external perception, even when 
 accurate, is an hallucination ; it is sufficient to observe that its 
 first phase is a sensation. In fact, a sensation, and notably 
 a tactile or visual sensation, engenders, by its presence alone, 
 an internal phantom which appears an external object. 
 Dreams, hypnotism, hallucinations strictly so called, all sub- 
 jective sensations are in evidence as to this. It matters little 
 whether the sensation be purely cerebral and arise sponta- 
 neously, without preliminary excitation of the peripheral ex- 
 tremity of the nerve, in the absence of the objects which 
 usually produce this excitation. As soon as ever the sensa- 
 tion is present, the rest follows; the prologue entails the 
 
 * Part ii. book i. chap, i, p. 221.
 
 CHAP. I.] EXTERNAL PERCEPTION. 
 
 drama. The patient imagines that he feels in his mouth the 
 melting pulp of an absent orange, or the cold pressure on 
 his shoulder of a hand which is not there, that he sees a num- 
 ber of passers-by in an empty street, or hears clearly articu- 
 lated sounds in his silent chamber. When, therefore, the sen- 
 sation arises in consequence of its usual antecedents, that is 
 to say after the excitation of the nerve and through the ef- 
 fect of an external object, it begets the same internal phantom, 
 and necessarily, this phantom appears an external object. 
 Consequently, if there are actually persons about in the street, 
 the sensation I shall experience in looking at them will excite 
 in me, as before, phantoms of persons about in the street, and 
 necessarily, as before, these purely internal phantoms will ap- 
 pear to me external objects, that is to say real and true per- 
 sons. Hence we see that the objects we touch, see, or per- 
 ceive by any one of our senses, are nothing more than sem- 
 blances or phantoms precisely similar to those which arise in 
 the mind of a hypnotized person, a dreamer, a person labor- 
 ing under hallucinations, or afflicted by subjective sensations. 
 The sensation being given, the phantom is produced : it is 
 produced, then, whether the sensation be normal or abnormal ; 
 it is produced, then, in perception where there is nothing to 
 distinguish it from the real object, just as in sickness where 
 every thing distinguishes it from the real object. 
 
 If its existence be established by its antecedents, it is 
 confirmed by its consequents. In fact, external perception 
 leaves a semblance behind it ; when we have seen some in- 
 teresting object, heard some fine music, felt a body of pecu- 
 liar texture, not only does the image of our sensation sur- 
 vive the sensation, but more than this, it is accompanied by 
 a more or less energetic and clear conception, representation, 
 or phantom of the object perceived. Suppose this represen- 
 tation very intense, it borders on hallucination ; if sleep is 
 drawing on, it becomes a complete hallucination ; in fact, this 
 is its natural ending ; we have seen that, when checked, it is by 
 means of a supervening repression or rectification which, at the 
 first moment, was absent. Therefore, at the first moment, that 
 is to say during external perception, it was not checked ; there 
 was, then, a complete hallucination, of which the preserved
 
 252 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 conception, the floating representation, the posthumous phan- 
 tom, is the remnant. In this state and at this second moment 
 we distinguish the phantom, which at the first moment we had 
 confounded with the real object. 
 
 There are other cases, again, in which we can contrive, di- 
 rectly, to separate them ; such are the various errors of exter- 
 nal perception, above all, those of the touch and of sight. I 
 am not speaking of those alone which proceed from purely 
 subjective sensations ; it is abundantly clear that in such 
 cases the apparent object is distinct from any real object, since 
 no real object exists. I am speaking of those proceeding 
 from ill-interpreted sensations ; in which cases there is a real 
 object, though it differs from the apparent object. For in- 
 stance, when we close our eyes and touch a marble with the 
 forefinger and ring-finger crossing one another, we imagine 
 ourselves to be touching two marbles ; this is one of the fal- 
 lacies of touch. Those of sight are innumerable ; we fall into 
 them daily in ordinary life, and may fabricate them at will by 
 optical instruments ; by means of the stereoscope we give to 
 two plane surfaces the appearance of a single body possessed 
 of relief, and there are a hundred analogous illusions. Take 
 the simplest of all, that produced by a figure reflected in a 
 looking-glass ; if the glass is without any flaw and fills up the 
 whole side of a room, if the light is well arranged, and we do 
 not know the circumstances, we shall imagine that we see a 
 figure before our eyes at a spot where there is nothing but a 
 wall. Now, in this and in all similar instances, what we take 
 for the real object differs from the real object ; the thing af- 
 firmed is nothing more than something apparent, there is noth- 
 ing corresponding to it at the spot and with the characters 
 assigned ; in other words, it is nothing more than a simple, 
 internal, ephemeral semblance which forms part of ourselves, 
 and which, nevertheless, appears to us an external thing, other 
 than ourselves, and permanent. But when our perception 
 was free from error, the operation was precisely the same ; 
 consequently, when our perception was free from error, we 
 produced and projected, in a similar way, to the indicated 
 spot, an apparent object, an internal and transient semblance 
 forming part of ourselves, and which, nevertheless, seemed to
 
 CHAP. I.] EXTERNAL PERCEPTION. 253 
 
 be a body external to us, independent and stable. The only 
 difference is that, in the first case, there was an independent 
 body, external and stable, which actually and rigorously cor- 
 responded to our semblance, and that now, this actual and 
 rigorous correspondence no longer takes place. Consequent- 
 ly, in the first case, we could not distinguish the semblance and 
 the body, and now we are able to do so. 
 
 Thus, there are three marks which indicate to us the 
 presence of the semblance, even in accurate external percep- 
 tion. In the first place, its exciting and sufficient condition, 
 the sensation, is found there ; it, then, must necessarily be 
 there. In the second place, we find it surviving an instant 
 afterwards, and repressed by an added rectification ; it was 
 there, then, an instant before, and was not repressed, that is 
 to say, was fully hallucinatory. In the third place we dis- 
 tinguish it in many instances, and, to effect this, it is suffi- 
 cient if the characters of the real object do not all perfectly 
 coincide with those of the semblance ; consequently we are 
 forced to admit its existence, even when the perfect coinci- 
 dence of all its characters with all those of the real object 
 prevents our establishing, by subsequent experience, any 
 difference between it and the real object. What is this real 
 object? Is there one? And, if we recognize one, on what 
 can we found our recognition ? We shall presently look for 
 answers to all these questions. Meanwhile, let us simply 
 postulate that when we perceive an object by the senses, 
 when we see a tree ten paces from us, when we take a marble 
 in our hand, our perception consists in the rising up of an 
 internal phantom of the tree or marble, and this phantom 
 appears to us an external, independent, durable thing, sit- 
 uated,- in the one case, at ten paces from us, in the other 
 case, in our hand. 
 
 II. In what does this internal phantom consist ? It is 
 plain that, among other elements, it comprises an affirmative 
 conception. When I see the tree or touch the marble, my 
 sensation suggests to me a judgment, that is to say a con- 
 ception and an affirmation. I conceive and I affirm, that at 
 ten paces from me is a being possessed of certain properties, 
 that in my hand is another such being, and the sufferer from
 
 254 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 hallucination, who has the sensation of an absent tree or of 
 an absent marble, comes to the same conclusion. Here we 
 have an essential element of the internal semblance ; there 
 is no external perception or hallucination which does not 
 contain an affirmative conception, the affirmative conception 
 of a being, thing, or substance possessed of properties. Let 
 us analyze this conception, and attempt to mark, one by one, 
 the distinct and connected conceptions of which it is the ag- 
 gregate. 
 
 Take the case of a mahogany table to which I direct my 
 eyes ; when I perceive it, I have, with regard to rhy retinal 
 sensation, an affirmative conception, which is that of some- 
 thing extended, resisting, hard, polished, feebly sonorous, 
 of a reddish brown color, of certain size and shape, in short, of 
 a being or substance possessed of the above-mentioned quali- 
 ties or properties. Let the reader consider for a moment : 
 here, as in every proposition, the substance is equivalent to 
 the indefinite series of its known or unknown properties. 
 Take away all the properties, without a single exception, ex- 
 tension, resistance, weight, hardness, polish, sonorousness, 
 figure, and lastly, the most general of all, existence itself; it 
 is plain that there will be nothing left of the substance ; it is 
 the aggregate of which the properties are the details ; it is 
 the whole of which the properties are the extracts ; take 
 away all the details, there will be nothing left of the aggre- 
 gate ; take away all the extracts, there will be nothing left 
 of the whole. The rule is general that in every proposi- 
 tion the attributes form the analysis of the subject, and 
 the subject is the sum of the attributes. Consequently, my 
 conception of substance is nothing more than a summary ; it 
 is equivalent to the sum of the conceptions composing it, just 
 as a number is equivalent to the sum of the units composing 
 it, or an abbreviatory sign to the things it abbreviates and 
 signifies. Consequ ntly, what I apply and attribute to the 
 substance is applicable and attributable to its equivalent. 
 When, then, I say that it is a being, a substance, or in other 
 words that it is, and that it subsists, this means that its prop- 
 erties are, and subsist. To conceive, then, and affirm a sub- 
 stance, is to conceive and affirm a group of properties as per-
 
 CHAP. I] EXTERNAL PERCEPTION. 255 
 
 manent and stable ; I say a group : for the properties which 
 constitute a body are not an arbitrary collection, a t^ap 
 piled up at will, like a number of units, which I collect as I 
 please and denote by a cipher ; they are not merely an added 
 sum, but more than this, they form a cluster. Any one of them 
 involves the rest : the squared form, the reddish color, the 
 feeble sonorousness, the polish, the hardness, combine to- 
 gether in the table ; the perfumed smell, the rosy color, the 
 semi-globular form, the softness, combine together in the 
 rose. In fact, whenever I experience them they are all com- 
 bined, and it is enough for me to ascertain the existence of 
 one of them by one of my senses, smell by the sense of smell, 
 color by the sight, to have the right to affirm the simultaneous 
 presence of the others whose existence I have not ascertained. 
 It is this cluster which forms the body. 
 
 III. Let us follow out successively the different threads. 
 In what do the properties of a body consist ? With the ma- 
 jority of them, the answer is easy. They are relative, relative 
 to my sensations, and to the sensations of every other being 
 analogous to myself: they are nothing more than a power, 
 the power of the body in question to excite certain particu- 
 lar sensations. The rose has a certain smell, differing from 
 that of the lily and from that of the violet ; this means that 
 it is capable of exciting in me, and in every other being con- 
 structed as I am, a certain agreeable sensation distinct from 
 other sensations of smell, and which we term the smell of the 
 rose. Sugar has a certain taste ; this again means that it is 
 capable of exciting in me and in every other being similar to 
 me, a certain special sensation of taste which we term a sug- 
 ary taste. And so it evidently is with colors and sounds. A 
 certain vibrating cord gives a sound of a particular acuteness, 
 a particular tone, and a particular intensity. A certain body 
 when illuminated gives a color of certain tint and certain 
 brightness. This means that the vibrating cord is capable 
 of exciting a certain particular sensation of sound, that the 
 illuminated body is capable of exciting a particular determi- 
 nate sensation of color. No doubt, in the present day we 
 know more than this ; optics and acoustics have taught us 
 that to a particular sound there correspond a particular num-
 
 256 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 her of vibrations of air, and to a particula color, a particular 
 number of vibrations of ether. But this is not the primi- 
 tive or ordinary judgment ; it is necessary to become scienti- 
 fic before we can form it ; the explanation is subsequent and 
 superadded. Besides, the difficulty is only shifted : when 
 provided with the theory, we say that the molecules of air or 
 ether have the power of exciting in us, by their oscillations, sen- 
 ' sations of sound or color. This power which the spontaneous 
 judgment ascribed to the illuminated body, and to the vibra- 
 ting cord, is now referred to the interposed molecules of air 
 or ether ; thus the color and sound still remain relative prop- 
 erties ; whether we attribute them to the vibrating cord and 
 the illuminated body, or to the particles of air and ether, they 
 are nothing more than the power of exciting in us certain 
 particular sensations. 
 
 Finally, if we pass from the four special senses to the 
 last and most general of all, that is to say to touch, 
 our conclusions are similar. In the first place, it is clear 
 that heat and cold are nothing more than the power of 
 exciting sensations of that name. So is it with solidity or 
 resistance, which is nothing more than the power of exciting 
 the muscular sensation of resistance. "When we contract 
 the muscles of our arm, either by an exertion of will, or 
 by an involuntary discharge of our spontaneous nervous 
 activity, the contraction is accompanied by a state of sensa- 
 tion, which is different according as the locomotion conse- 
 quent on the muscular contraction continues freely, or meets 
 with an impediment. In the former case, the sensation is 
 that of motion through empty space. After having had (let 
 us suppose) this experience several times repeated, we sud- 
 denly have a different experience : the series of sensations ac- 
 companying the motion of our arm is brought, without inten- 
 tion or expectation on our part, to an abrupt close. This 
 interruption would not, of itself, necessarily suggest the be- 
 lief in an external obstacle. The hindrance might be in our 
 organs ; it might arise from paralysis, or simple loss of power 
 through fatigue. But in either of these cases, the muscles 
 would not have been contracted, and we should not have had 
 the sensation which accompanies their contraction. We may
 
 CHAP. I.] EXTERNAL PERCEPTION. 257 
 
 have had the will to exert our muscular force, but the exer- 
 tion has not taken place. If it does take place, and is accom- 
 panied by the usual muscular sensation, but the expected sen- 
 sation of locomotion does not follow, we have what is called 
 the feeling of Resistance, or in other words, of muscular mo- 
 tion impeded."* Later on, when we have acquired the idea 
 of our limbs, we shall translate such an uninterrupted series 
 of muscular sensations by the idea of an unimpeded move- 
 ment of our arm, and we shall translate the same series of 
 sensations, when interrupted, by the idea of the hindered 
 movement of our arm. In fact, the one is capable of replac- 
 ing the other ; when once our senses are instructed, we dis- 
 cover that a particular series of muscular sensations evidenced 
 by consciousness is equivalent to a particular movement of 
 our hand evidenced by our eyes or touch ; we substitute the 
 second fact for the first, as being more convenient to imagine 
 and more generally applicable to nature, and henceforth, we 
 define resistance as the power of arresting the movement of 
 our arm, and in general of any body whatever. But this is 
 an ulterior conception. Primitively, resistance is nothing 
 more to us than the power to arrest a commenced series of 
 muscular sensations, and the other tactile qualities are reduci- 
 ble like resistance, to the power of exciting some tactile or mus- 
 cular sensation more or less simple or compound, some mode 
 or modification of a muscular and tactile sensation, or of a 
 series of such sensations. A body is smooth or rough ; which 
 means that it is capable of exciting a uniform and soft sensa- 
 tion of contact, or an irregular and harsh sensation of contact. 
 Heavy, light, sharp, level, hard, soft, sticky, damp,f all these 
 terms denote nothing more than the power of exciting more 
 or less complex, intense, and varied sensations of contact, of 
 pressure, of temperature, of muscular contraction, and of 
 pain. 
 
 IV. There remain a group of properties which seem at 
 first sight intrinsic and personal to bodies, and not merely 
 relative to sensations ; such are extension, form, mobility, 
 
 * J. S. Mill, " Examination of Sir W. Hamilton's Philosophy," 219. 
 \ Experiments of Landry, Gratiolet, Fick, and Bain. See part i. book iii. 
 chap. 2, ante, p. 138. 
 
 17
 
 258 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 situation, and all geometrical properties. And, in fact, it is 
 by means of such as these that we explain the different pow- 
 ers we have just described ; we conceive and suppose little 
 bodies with extension and shape which we term molecules ; 
 we assume that they move in a certain direction and with 
 certain velocities ; that two given molecules continue to ap- 
 proach or to separate from each other with more or less speed 
 according to their reciprocal distance ; that a collection of 
 molecules, whose movements are mutually annulled or com- 
 pensated, form a stable body, whose equilibrium becomes al- 
 tered by the approach of another similarly constituted body. 
 Such is our idea of body, a fully reduced and abstract idea ; 
 this is to us the essential and indispensable part of a body; 
 in what do these properties consist ? 
 
 We must first observe that they are reducible to a princi- 
 pal property, extension, and to one of the powers enumerated 
 above, resistance. A body is a solid or resisting extension ; 
 that is to say, an extension capable of exciting, in all its con- 
 tinuous and successively explored portions, the sensation of 
 resistance ; if not in us, at all events in a being with acuter 
 senses than ours. By this, solid extension is distinguished 
 from empty extension ; that is to say from the place it occu- 
 pies. By this, again, we define mobility, which is nothing 
 more than the power of changing place. Finally, by this, we 
 define its limits. It has a surface, that is to say, a limit ; the 
 surface is the limit of solid extension, as the line is the limit 
 of the surface, and the point the limit of the line. Now, limit 
 means cessation ; the surface, the line, the point, and the fig- 
 ures derived from them, are nothing more than aspects of 
 solidity, various modes of considering its cessation and its 
 absence ; that is to say, the absence and the cessation of the 
 sensation of resistance. Extension itself remains. We may 
 consider it in three aspects, according to three dimensions, in 
 length, breadth, and height. Take the case of a cube ; its ex- 
 tension in length, breadth and height, is the distance separa- 
 ting a point taken at one of its angles from three points taken 
 at three other angles. Distance in three senses or directions 
 is the foundation of our idea of extension. Here we need
 
 CHAP. I.] EXTERNAL PERCEPTION. 
 
 only reproduce the admirable analysis of the latest English 
 philosophers.* 
 
 When I contract one of my muscles, I experience one 
 of those sensations we term muscular, and I may consider 
 this from two points of view. In the first place, my sensa- 
 tion is more or less powerful ; it is extreme, if the effort ap- 
 proaches a strain of the muscle ; its limit is the pain termed 
 cramp ; its character is of greater or less intensity, and I can 
 compare my sensation in this respect with other more or less 
 intense sensations of the same muscle. Thus regarded, it 
 enables me to estimate the resistance which other bodies 
 oppose to me; but as yet, teaches me nothing respecting 
 their extension, distance, and position. But there is a second 
 point of view, and to this we owe our idea of extension. For 
 muscular sensations vary not only in greater or less intensity, 
 but also in greater or less duration. " When a muscle begins 
 to contract," says Mr. Bain, " or a limb to bend, we have a 
 distinct sense of how far the contraction and the bending are 
 carried ; there is something in the special sensibility that 
 makes one mode of feeling for half contraction, another mode 
 for three-fourths, and another for total contraction." Thus we 
 distinguish in the sensation, not only an increase of intensity, 
 but also an increase of duration. " Suppose a weight raised by 
 the flexing of the arm, first four inches, and then eight inches." 
 We shall obviously distinguish the second sensation from the 
 first, and, in the first place, clearly, because, other things being 
 equal, the second lasts twice as long as the first, and then, 
 probably, because in the second period of effort, other muscles 
 coming into play, produce new muscular sensations, which 
 add themselves on to the continuation of the first sensations, 
 not only by prolonging, but also by diversifying the operation. 
 By these two distinct sensations, we distinguish the greater 
 or less amplitude of our two movements ; and we see how we 
 can in a general manner distinguish the amplitude of one of 
 our movements compared with another. It is by means of 
 this muscular discernment that we arrive at a knowledge of 
 
 * Bain, " Senses and Intellect," 99 and 199. Herbert Spencer, " Principles of 
 Psychology," 1st Edition, 304. J. S. Mill, " Examination," etc., 222.
 
 2 6o THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 extension and space. For, "in the first place it gives the 
 feeling of linear extension, inasmuch as this is measured by the 
 sweep of a limb, or other organ moved by muscles. The 
 difference between six inches and eighteen inches is express- 
 ed to us by the different contraction of some one group oi mus- 
 cles ; those for example that flex the arm, or, in walking, those 
 that flex or extend the lower limb. The inward impression 
 corresponding to the outward fact of six inches in length, is 
 an impression arising from the continued shortening of a mus- 
 cle, a true muscular sensibility. It is the impression of a mus- 
 cular effort having a certain continuance ; a greater length 
 produces a greater continuance " Now, " the discrim- 
 ination of length in any one direction includes extension in 
 any direction. Whether it be length, breadth, or height, the 
 perception has precisely the same character. Hence super- 
 ficial and solid dimensions, the size or magnitude of a solid 
 
 object, come to be felt in a similar manner It will be 
 
 obvious that what is called situation or locality must come under 
 the same head, as these are measured by distance taken along 
 with direction ; direction being itself estimated by distance, 
 both in common* observation and in mathematical theory. In 
 like manner form or shape is ascertained through the same 
 primitive sensibility to extension or range.* By the muscular 
 sensiblity thus associated with prolonged contraction we can 
 therefore compare different degrees of the attribute of space, 
 in other words, difference of length, surface, situation, and 
 form. When comparing two different lengths we can feel 
 which is the greater, just as in comparing two different weights 
 or resistances. We can also, as in the case of weight, acquire 
 some absolute standard of comparison, through the permanency 
 of impressions sufficiently often repeated. We can engrain 
 the feeling of contraction of the muscles of the lower limb 
 due to a pace of thirty inches, and can say that some one 
 given pace is less or more than this amount. According to 
 
 * We see that the idea of form is reduced to that of position, which is reduced 
 to that of distance. Analytical geometry is entirely founded on this observation ; 
 it translates form by the relations of two or three co-ordinates representing dis- 
 tances.
 
 CHAP. I.] EXTERNAL PERCEPTION. 2 6l 
 
 the delicacy of the muscular tissue we can, by shorter or 
 longer practice, acquire distinct impressions for every stand- 
 ard dimension, and can decide at once whether a given length 
 is four inches or four and a half, nine or ten, twenty or twenty- 
 one. This sensibility to size, enabling us to dispense with 
 the use of measures of length, is an acquirement suited to 
 many mechanical operations. In drawing, painting, and en- 
 graving, and in the plastic arts, the engrained discrimination 
 of the most delicate differences is an indispensable qualifi- 
 cation." 
 
 A third aspect remains ; for there are not merely different 
 degrees of intensity and duration, but different degrees of ve- 
 locity in our muscular movements, and the same contraction 
 of the same muscles excites in us two different muscular 
 sensations according as it is rapid or slow. We learn by ex- 
 perience that in many cases these two distinct sensations are 
 signs of the same movement; in this they are equivalent. 
 "A slow motion for a long time is the same as a quicker mo- 
 tion with less duration." We easily convince ourselves of 
 this " by seeing that they both produce the same effect in 
 exhausting the full range of a limb. If we experiment upon 
 the different ways of'accomplishing a total sweep of the arm, 
 we shall find that the slow movements long continued are 
 equal to quick motions of short continuance, and we are thus 
 able by either course to acquire to ourselves a measure of 
 range and linear extension." " Suppose," says Mill, " two 
 small bodies, A and B, sufficiently near together to admit of 
 their being touched simultaneously, one with the right hand, 
 the other with the left. Here are two tactual sensations 
 which are simultaneous, just as a sensation of color and one 
 of odor might be ; and this makes us cognize the two objects 
 of touch as both existing at once. The question then is, 
 what have we in our minds, when we represent to ourselves 
 the relation between these two objects, already known to be 
 simultaneous, in the form of Extension or intervening Space 
 a relation which we do not suppose to exist between the 
 color and the odor." Our answer to this is " that whatever 
 the notion of Extension may be, we acquire it by passing our 
 hand or some other organ of touch, in a longitudinal direction
 
 2 62 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 from A to B : that this process, as far as we are conscious of 
 
 it, consists of a series of varied muscular sensations 
 
 When we say that there is a space between A and B, we 
 mean that some amount of these muscular sensations must in- 
 tervene ; and when we say that the space is greater or less, 
 we mean that the series of sensations (amount of muscular 
 effort being given) is longer or shorter. If another object, C, 
 is farther off in the same line, we judge its distance to be 
 greater, because, to reach it, the series of muscular sensations 
 must be further prolonged, or else there must be the increase 
 of effort which corresponds to augmented velocity. Now 
 this, which is unquestionably the mode in which we became 
 aware of extension, is considered by the psychologists in ques- 
 tion to be extension. The idea of Extended Body they con- 
 sider to be that of a variety of resisting points, existing simul- 
 taneously, but which can be perceived by the same tactile 
 organ only successively, at the end of a series of muscular 
 sensations which constitutes their distance ; and are said to 
 be at different distances from one another because the series 
 of intervening muscular sensations is longer in some cases 
 than in others An intervening series of muscular sen- 
 sations before the one object can be reached from the other, 
 is the only peculiarity which (according to this theory) distin- 
 guishes simultaneity in space from the simultaneity which 
 may exist between a taste and a color, or a taste and a smell : 
 and we have no reason for believing that Space or Extension 
 in itself, is any thing different from that which we recognize 
 it by."* 
 
 Thus, in our cases, time is the parent of space, and we 
 conceive simultaneous magnitude by means only of success- 
 ive magnitude. When our arm moves, it traverses a space ; 
 but we do not estimate the magnitude of what is traversed 
 except by the two factors measuring it, on the one hand by 
 the amount of our muscular exertion, on the other hand by 
 the duration of our successive muscular sensations. In tran- 
 sit through space there are three terms the magnitude of 
 the motive force, the length of time employed, the extent of 
 
 * Mill, " Examination," etc., pp. 228-30.
 
 CHAP. I.] EXTERNAL PERCEPTION. 263 
 
 space traversed and each of these is determined by the oth- 
 er two. Now, the two first we find in ourselves, and they 
 are together equivalent to the third, since the third is com- 
 pletely determined by them. It is by the first two, then, 
 that the space traversed is translated into our minds, and 
 such space is in itself nothing more to us than the power of 
 exciting them. Thus, greater or less space is nothing more 
 than the power of exciting in us, with an equal amount of 
 muscular effort, a longer or shorter series of successive mus- 
 cular sensations. Add to this solidity, that is to say the 
 power of exciting the sensation of resistance, and we have 
 body. In fact, its three dimensions are the three distinct as- 
 pects to which all the sensations measuring its extension are 
 reduced. Its continuity is the power of exciting the sensa- 
 tion of resistance, throughout the whole duration of these 
 sensations. Its limit is the moment at which the sensation 
 of resistance ceases. Its figure is the aggregate of these lim- 
 its. We conceive it as composed of parts, because the sen- 
 sation, whose duration measures it, is itself composed of parts. 
 So too it is infinitely divisible, because this duration is itself 
 infinitely divisible. Though the elements of our sensation 
 be successive, the elements of the body appear to us as simul- 
 taneous ; in fact, they are, as the body itself, permanent pow- 
 ers, whose permanence, like that of the body itself, is attest- 
 ed to us by the regular return of the sensations they excite ; 
 being permanent, they are contemporaneous ; though we per- 
 ceive them successively they exist together, and the succes- 
 sion disjoining their effects is not applicable to their existence. 
 I pass my hand several times heavily along the side of the 
 table, from left to right, then from right to left, and always 
 with the same speed ; that is to say with the same amount 
 of motive effort. Now, in all these experiences, the sensation 
 given me by my contracted arm is the same in duration, and 
 has, as accompaniment, at every moment, the uniform sen- 
 sation of resistance. Whether I begin at the right or left, it 
 does not matter ; the double muscular sensation remains the 
 same in the two cases. It forms, then, a severed group among 
 my recollections and previsions,; it is distinguished from the 
 others by the precise degree of intensity of the first compo-
 
 264 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 nent muscular sensation, by the precise degree of duration 
 of the second component muscular sensation, and further, by 
 the particular shade of the conjoined sensation of touch ; the 
 power of exciting this group is what we term the resistance 
 and extension of the table. Hence, we see that all the sen- 
 sible properties of bodies, including extension, and conse- 
 quently form, situation, and other tangible qualities, are, in 
 final analysis, nothing more than the power of exciting sen- 
 sations. 
 
 V. This leads us to a new notion of the nature of bodies ; 
 a body is a collection of such powers as we have just described. 
 But what are these powers. ? This rose has power to excite a 
 certain sensation of smell ; which means that, when within 
 reach of it, this sensation of smell will be aroused. This table 
 has power to excite a certain strong sensation of resistance ; 
 which means that, if it is pressed with the hand, a strong 
 sensation of resistance will be aroused. A power, then, is 
 nothing intrinsic and personal to the object to which we at- 
 tribute it. We simply mean by the word that certain effects 
 are possible, future, proximate, necessary under certain con- 
 ditions. We simply mean, in this instance, that certain sen- 
 sations are possible, future, proximate, necessary under cer- 
 tain conditions. Consequently, a collection of powers is noth- 
 ing ; consequently a body, that is to say a collection of 
 powers, is also nothing. At the foundation of the affirmative 
 conception, by which, having passed and pressed my hand 
 over this table, I conceive arid affirm an independent and 
 permanent body, there is nothing more than the affirmative 
 conception of analogous muscular and tactile sensations, these 
 sensations being conceived and affirmed as possible for any 
 being similar to myself, who might come within their range, 
 as future, proximate, certain, and necessary, for any being sim- 
 ilar to myself, who might pass and press his hand or other 
 organ in the same manner. All I conceive and affirm is 
 their possibility under certain conditions, and their necessity 
 under fuller conditions. They are possible when all these 
 conditions, but one, are given. They become necessary when 
 all these conditions, and in addition the missing condition, 
 are given ; and here the possibility becomes necessity, by the
 
 CHAP. I.] EXTERNAL PERCEPTION. 2 6$ 
 
 addition of the last condition. This is what constitutes for us 
 the object. When, with closed eyes, I experience a sensa- 
 tion of the smell of a rose, and thereupon conceive and affirm' 
 the presence of a rose, I simply conceive and affirm the pos- 
 sibility for myself, and for every other being similar to myself, 
 of a certain muscular and tactile sensation of soft resistance, 
 of a certain visual sensation of colored form ; a possibility 
 would become a necessity, if, to the existence and presence 
 of the sentient person indicated, were added a final condition, 
 a certain movement of his exploring hand, a certain direction 
 of his open eyes. Certain possibilities and certain necessities of 
 sensations, to these are reducible the powers, consequently 
 the properties, consequently the very substance of bodies. 
 
 This conclusion seems paradoxical. How can we admit 
 that bodies, that is to say permanent substances independent 
 of us, and which we conceive as causes of our sensations, 
 are, at bottom, and in themselves, nothing more than possi- 
 bilities and necessities of sensation ? To remove this diffi- 
 culty, let us consider successively the principal characters of 
 these possibilities and necessities, and we shall see that they 
 possess all the characters of substance. They are permanent ; 
 in fact, the proposition by which I affirm the possibility and 
 necessity of a certain sensation under certain conditions is 
 general, and holds good for all moments of time. Whatever 
 be the moment of duration I am considering, this possibility 
 and this necessity are found there ; they are, then, persistent 
 and stable. On the other hand, they are independent of me, 
 and of all sentient individuals who are living, have lived, or will 
 live. For the proposition by which I affirm the possibility 
 and necessity of certain sensations under certain conditions 
 is abstract, and holds good, not only in my case and in that 
 of every actual person, but for all possible persons. Even 
 were there not in fact any sentient individual in the world, 
 they would exist ; they exist, then, apart and by themselves. 
 For these two reasons, they are opposed, first, to sensa- 
 tions which are transient and not, like them, permanent ; then, 
 to sentient individuals themselves who are other than they. 
 These are the essential characters of substance ; consequently, 
 there is nothing astonishing in' our terming these possibilities
 
 266 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 substances, and in their playing a predominant part in our 
 mind. 
 
 Let us see how it is they assume this part. " I see a 
 piece of white paper on a table. I go into another room, 
 and though have I ceased to see it, I am persuaded that the 
 paper is still there. I no longer have the sensations which 
 it gave me ; but I believe that when I again place myself in 
 the circumstances in which I had those sensations, that is, 
 when I go again into the room, I shall again have them ; and 
 further, that there has been no intervening moment at which 
 this would not have been the case." This is a specimen of 
 the ordinary operations of our mind, and it is plain that the 
 analysis would be the same, in the case of any other percep- 
 tion of sight, or of another sense. Now, in accordance with 
 this analysis, it appears " that my conception of the world at 
 any given instant consists, in only a small proportion, of 
 present sensations. Of these I may at the time have none 
 at all, and they are in any case a most insignificant portion 
 of the whole which I apprehend. The conception I form of 
 the world existing at any moment, comprises, along .with the 
 sensations I am feeling, a countless variety of possibilities 
 of sensation ; namely, the whole of those which past obser- 
 vation tells me that I could, under any supposable circum- 
 stances, experience at this moment, together with an indefi- 
 nite and illimitable multitude of others which though I do 
 not know that I could, yet it is possible that I might ex- 
 perience in circumstances not known to me. These various 
 possibilities are the important thing to me in the world. My 
 present sensations are generally of little importance, and are 
 moreover fugitive : the possibilities, on the contrary are per- 
 manent, which is the character that mainly distinguishes our 
 idea of Substance or Matter from our notion of sensation. 
 These possibilities, which are conditional certainties, need a 
 special name to distinguish them from mere vague possibilities, 
 which experience gives no warrant for reckoning upon. Now, 
 as soon as a distinguishing name is given, though it be only 
 to the same thing regarded in a different aspect, one of the 
 most familiar experiences of our mental nature teaches us, 
 that the different name comes to be considered as the name 
 of a different thing.
 
 CHAP. I.] EXTERNAL PERCEPTION. 2 6/ 
 
 " There is another important peculiarity of these certified 
 or guaranteed possibilities of sensation ; namely, that they 
 have reference, not to single sensations, but to sensations 
 joined together in groups. When we think of any thing as 
 a material substance, or body, we either have had, or we 
 think that on some given supposition we should have, not 
 some one sensation, but a great and even an indefinite num- 
 ber and variety of sensations, generally belonging to different 
 senses, but so linked together that the presence of one an- 
 nounces the possible presence at the very same instant of 
 any or all of the rest. In our mind, therefore, not only is 
 this particular Possibility of sensation invested with the 
 quality of permanence, when we are not actually feeling any of 
 the sensations at all ; but when we are feeling some of them, 
 the remaining sensations of the group are conceived by us in 
 the form of Present Possibilities, which might be realized at 
 the very moment. And as this happens in turn to all of 
 them, the group as a whole presents itself to the mind as 
 permanent, in contrast not solely with the temporariness of 
 my bodily presence, but also with the temporary character 
 of each of the sensations composing the group ; in other 
 words, as a kind of permanent substratum, under a set of 
 passing experiences or manifestations : which is another lead- 
 ing character of our idea of substance or matter, as distin- 
 guished from sensation. 
 
 " Let us now take into consideration another of the gen- 
 eral characters of our experience, namely, that in addition to 
 fixed groups, we also recognize a fixed Order in our sensa- 
 tions; an Order of succession, which, when ascertained by 
 observation, gives rise to the ideas of Cause and Effect .... 
 Now, of what nature is this fixed order among our sensa- 
 tions? It is a constancy of antecedence and sequence. But 
 the constant antecedence and sequence do not generally exist 
 between one actual sensation and another. Very few such 
 sequences are presented to us by experience. In almost all the 
 constant sequences which occur in Nature, the antecedence and 
 consequence do not obtain between sensations, but between the 
 groups we have been speaking about, of which a very small por- 
 tion is actual sensation, the greater part being permanent pos-
 
 2 68 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 sibilities of sensation, evidenced to us by a small and variable 
 number of sensations actually present. Hence, our ideas of 
 causation, power, activity, do not become connected in thought 
 with our sensations as actual at all, save in the few physio- 
 logical cases where these figure by themselves as the ante- 
 cedents in some uniform sequence. Those ideas become con- 
 nected, not with sensations, but with groups of possibilities 
 of sensation. The sensations conceived do not, to our ha- 
 bitual thoughts, present themselves as sensations actually ex- 
 perienced, inasmuch as not only any one or any number of 
 them may be supposed absent, but none of them need be 
 present. We find that the modifications which are taking 
 place more or less regularly in our possibilities of sensation, 
 are mostly quite independent of our consciousness, and of 
 our presence or absence. Whether we are asleep or awake 
 the fire goes out, and puts an end to one particular possi- 
 bility of warmth and light. Whether we are present or ab- 
 sent the corn ripens, and brings a new possibility of food. 
 Hence we speedily learn to think of Nature as made up 
 solely of these groups of possibilities, and the active force 
 in Nature as manifested in the modification of some of these 
 by others. The sensations, though the original foundation 
 of the whole, come to be looked upon as a sort of accident 
 depending on us, and the possibilities as much more real 
 than the actual sensations, nay, as the very realities of which 
 these are only the representations, appearances, or effects. 
 When this state of mind has been arrived at, then, and from 
 that time forward, we are never conscious of a present sen- 
 sation without instantaneously referring it to some one of 
 the groups of possibilities into which a sensation of that par- 
 ticular description enters ; and if we do not yet know to 
 what group to refer it, we at least feel an irresistible convic- 
 tion that it must belong to some group or other ; i. e. that its 
 presence proves the existence, here and now, of a great num- 
 ber and variety of possibilities of sensation, without which it 
 would not have been. The whole set of sensations as pos- 
 sible, form a permanent background to any one or more of 
 them that are, at a given moment, actual ; and the possi- 
 bilities are conceived as standing to the actual sensations in
 
 CHAP. I.] EXTERNAL PERCEPTION. 269 
 
 the relation of a cause to its effects, or of canvas to the fig- 
 ures painted on it, or of a root to the trunk, leaves, and 
 flowers or of a substratum to that which is spread over it, or, 
 in transcendental language of Matter to Form. 
 
 " When this point has been reached, the Permanent Pos- 
 sibilities in question have assumed such unlikeness of aspect, 
 and such difference of apparent relation to us, from any sen- 
 sations, that it would be contrary to all we know of the con- 
 stitution of human nature that they should not be conceived 
 as, and believed to be, at least as different from sensations as 
 sensations are from one another. Their groundwork in sen- 
 sation is forgotten, and they are supposed to be something 
 intrinsically distinct from it. We can withdraw ourselves from 
 any of our (external) sensations, or we can be withdrawn from 
 them by some other agency. But though the sensations cease, 
 the possibilities remain in existence : they are independent 
 of our will, our presence, and every thing which belongs to 
 us. We find, too, that they belong as much to other human 
 or sentient beings as to ourselves. We find other people 
 grounding their expectations and conduct upon the same per- 
 manent possibilities on which we ground ours. But we do 
 not find them experiencing the same actual sensations. Other 
 people do not have our sensations exactly when and as we 
 have them: but they have our possibilities of sensation ; what- 
 ever indicates a present possibility of sensations to ourselves, 
 indicates a present possibility of sensations to them, except 
 so far as their organs of sensation may vary from the type of 
 ours. This puts the final seal to our conception of the groups 
 of possibilities as the fundamental reality in Nature. The 
 permanent possibilities are common to us and to our fellow- 
 creatures ; the actual sensations are not. That which other 
 people become aware of when, and on the same grounds as 
 I do, seems more real to me than that which they do not know 
 of unless I tell them. The world of Possible Sensations suc- 
 ceeding one another, according to laws, is as much in other 
 beings as it is in me ; it has therefore an existence outside 
 me ; it is an External World. 
 
 " Matter, then, may be defined, a Permanent Possibility 
 of Sensation We believe that we perceive a something
 
 270 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 closely related to all our sensations, but different from those 
 which we are feeling at any particular minute ; and distin- 
 guished from sensations altogether, by being permanent and 
 always the same, while these are fugitive, variable, and alter- 
 nately displace one another. But these attributes of the ob- 
 ject of perception are properties belonging to all the possibili- 
 ties of sensation, which experience guarantees. The belief 
 in such permanent possibilities seems to me to include all that 
 is essential or characteristic in the belief in substance. I be- 
 lieve that Calcutta exists, though I do not perceive it, and 
 that it would still exist if every percipient inhabitant in it 
 were suddenly to leave the place, or be struck dead. But 
 when I analyze the belief, all I find in it is, that were those 
 events to take place, the Permanent Possibility of Sensation 
 which I call Calcutta would still remain ; that if I were sud- 
 denly transported to the banks of the Hooghly, I should still 
 have the sensations which, if now present, would lead me to 
 affirm that Calcutta exists here and now.* We may infer, 
 therefore, that both philosophers and the world at large, when 
 they think of matter, conceive it really as a Permanent Possi- 
 bility of Sensation. But the majority of philosophers fancy 
 that it is something more ; and the world at large, though 
 they have really, as I conceive, nothing in their minds but a 
 Permanent Possibility of Sensation, would, if asked the ques- 
 tion, undoubtedly agree with the philosophers ; and though 
 this is sufficiently explained by the tendency of the human 
 mind to infer difference of things from difference of names I 
 acknowledge the obligation of showing how it can be possible 
 to believe in an existence transcending all possibilities of sen- 
 sation, unless on the hypothesis that such an existence act- 
 ually is, and that we actually perceive it. 
 
 "The explanation, however, is not difficult. It is an ad- 
 mitted fact that we are capable of all conceptions which can 
 be formed by generalizing from the observed laws of our sen- 
 sations. Whatever relation we find to exist between any one 
 
 * For analysis to be wholly exact, it should read, I think : " If any being 
 whatever, analogous to myself, were transported to the banks of the Hooghly, he 
 would have, etc." The permanent possibility is absolutely general.
 
 CHAP. I.] EXTERNAL PERCEPTION. 2/1 
 
 of our sensations and something different from it, that same 
 relation we have no difficulty in conceiving to exist between 
 the sum of all our sensations and something different from 
 them. The differences which our consciousness recognizes be- 
 tween one sensation and another give us the general notion 
 of difference, and inseparably associate with every sensation 
 we have, the feeling of its being different from other things : 
 and when once this association has been formed, we can no 
 longer conceive anything, without being able, and even being 
 compelled, to form also the conception of something differ- 
 ent from it. This familiarity with the idea of something dif- 
 ferent from each thing we know makes it natural and easy to 
 form the notion of something different from #// things that we 
 know, collectively as well as individually. It is true we can 
 form no conception of what such a thing can be ; our notion 
 of it is merely negative; but the idea of a substance, apart 
 from its relation to the impressions which we conceive it as 
 making on our senses, is a merely negative one. There is 
 thus no psychological obstacle to our forming the notion of 
 a something which is neither a sensation nor a possibility of 
 sensation, even if our consciousness does not testify to it ; and 
 nothing is more likely than that the Permanent Possibilities 
 of sensation, to which our consciousness does testify, should 
 be confounded in our minds with this imaginary conception. 
 All experience attests the strength of the tendency to mistake 
 mental abstractions, even negative ones, for substantive reali- 
 ties ; and the Permanent Possibilities of sensation which ex- 
 perience guarantees are so extremely unlike in many of their 
 properties to actual sensations, that since we are capable of 
 imagining something which transcends sensations, there is a 
 great natural probability that we should suppose these to be 
 it. 
 
 " But this natural possibilty is converted into certainty, 
 when we take into consideration that universal law of our 
 experience which is termed the law of Causation, and which 
 makes us mentally connect with the beginning of every thing 
 some antecedent condition or Cause. The case of Causation 
 is one of the most marked of all the cases in which we extend 
 to the sum total of our consciousness, a notion derived from
 
 272 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 its parts. It is a striking example of our power to conceive, 
 and our tendency to believe, that a relation which subsists 
 between every individual item of our experience and some 
 other item, subsists also between our experience as a whole, 
 and something not within the sphere of experience. By this 
 extension to the sum of all our experiences, of the internal 
 relations obtaining between its several parts, we are led to 
 conceive sensation itself the aggregate whole of our sensa- 
 tions as deriving its origin from antecedent existences trans- 
 cending sensation. That we should do this, is a consequence 
 of the particular character of the uniform sequences, which 
 experience discloses to us among our sensations. As already 
 remarked, the constant antecedent of a sensation is seldom 
 another sensation, or set of sensations, actually felt. It is 
 much oftener the existence of a group of possibilities, not nec- 
 essarily including any actual sensations, except such as are re- 
 quired to show that the possibilities are really present. Nor 
 are actual sensations indispensable even for this purpose ; for 
 the presence of the object (which is nothing more than the 
 immediate presence of the possibilities) may be made known 
 to us by the very sensations we refer to it as its effect. Thus, 
 the real antecedent of an effect the only antecedent which, 
 being invariable and unconditional, we consider to be the 
 cause may be, not any sensation really felt, but solely the 
 presence at that or the immediately preceding moment of a 
 group of possibilities of sensation. Hence it is not with sen- 
 sations as actually experienced, but with their Permanent 
 Possibilities, that the idea of Cause comes to be identified : 
 and we, by one and the same process, acquire the habit of re- 
 garding Sensation in general, like all our individual sensations, 
 as an Effect, and also that of conceiving as the causes of most 
 of our individual sensations, not other sensations, but general 
 
 possibilities of sensation It may perhaps be said that 
 
 the preceding theory gives, indeed, some account of the idea 
 of Permanent Existence which forms part of our conception 
 of matter, but gives no explanation of our believing these per- 
 manent objects to be external, or out of ourselves. I appre- 
 hend, on the contrary, that the very idea of anything out of 
 ourselves is derived solely from the knowledge experience
 
 CHAP. I.] EXTERNAL PERCEPTION. 273 
 
 gives us of the Permanent Possibilities. Our sensations we 
 carry with us wherever we go, and they never exist where we 
 are not ; but when we change our place we do not carry away 
 with us the Permanent Possibilities of Sensation : they re- 
 main until we return, or arise and cease under conditions with 
 which our presence has in general nothing to do. And more 
 than all they are, and will be after we have ceased to feel, 
 Permanent Possibilities of Sensation to other beings than our- 
 selves. Thus, our actual sensations, and the permanent pos- 
 sibilities of sensation, stand out in obtrusive contrast to one 
 another: and when the idea of Cause has been acquired, and 
 extended by generalization from the parts of our experience 
 to its aggregate whole, nothing can be more natural than that 
 the Permanent Possibilities should be classed by us as exist- 
 ences generically distinct from our sensations, but of which 
 our sensations are the effect If all these considera- 
 tions put together do not completely explain and account 
 for our conceiving these Possibilities as a class of independ- 
 ent and substantive entities, I know not what psychological 
 analysis can be conclusive."* 
 
 In my opinion, this is so, save in a point we have already 
 indicated. These possibilities of sensation constituted by the 
 presence of all the conditions of the sensation, but one, are 
 transfofmed into necessities, when this last absent condition 
 becomes added to the rest. I see a table ; which means that, 
 having a particular visual sensation, I conceive and affirm the 
 possibility of certain sensations of muscular movement, resist- 
 ance, and feeble sound in every sentient being ; but it also 
 means that if to the existence of a sentient being we add a 
 further condition, some movement which will put his hand in 
 contact with the table, there will be, in his case, no longer a 
 simple possibility, but further than this, the necessity of these 
 sensations. These necessities, set apart and considered sep- 
 arately, are what we call forces.f Force or necessity, these 
 two terms are equivalent ; they indicate that the event in 
 question must become accomplished ; both one and the other 
 
 * Mill, " Examination,'* etc. pp. 192-205. 
 f Part i. book iv. ch. iii. p. 2O2. 
 18
 
 274 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 are particularities, modes of being extracted from the event 
 and isolated by a mental fiction. But as the law predicting 
 the event under certain conditions is general, and therefore 
 permanent, both one and the other appear as permanent, and 
 are found to be erected into substances, which puts them in 
 opposition to transient events and classes them apart. At 
 present, under the name of forces, permanent possibilities are 
 reducible without difficulty to what we term matter and body ; 
 we have no hesitation in admitting that the world in which 
 we are placed is a system of forces ; at all events, this is the 
 conception of the most profound physicists. Various forces, 
 which, under various conditions, excite in us various sensa- 
 tions : in this we have bodies in their relation to ourselves, 
 and to all beings analogous to us. 
 
 VI. What a body is with relation to another remains to 
 be investigated. We must first observe that the majority of 
 bodies which we perceive change, at least in many respects, 
 and that daily experience has no difficulty in ascertaining 
 these changes. They change, which means that, in the group 
 of permanent possibilities constituting them, some particular 
 possibility perishes ; in other words again, among the possi- 
 ble sensations which denote a body, some particular sensa- 
 tion ceases to be possible. The top of this stove was cold a 
 short time ago ; now the fire has been lighted, it is hot. This 
 ball of wax is spherical, hard, odorous, capable of rendering a 
 slight sound ; when placed on the hot stove it becomes soft, 
 loses its sonorousness and smell, and becomes a thick liquid. 
 This green leaf has no longer any color in the dark. I left 
 this book on my table, and find it on one of the shelves of 
 the bookcase. In all these cases, one or more of the possi- 
 bilities of sensation constituting the object have disappeared, 
 but are replaced or not by others of the same kind. All these 
 changes of bodies are, at bottom, conceived and conceivable 
 only with relation to sensations, since they are all reduced, 
 in final analysis, to the extinction or arising of a possibility of 
 sensation. But, from another point of view, though bodies 
 are but possibilities of sensation, these changes are none the 
 less changes of bodies, and it is from this point of view that 
 we usually consider them. When we no longer find a sensa-
 
 CHAP. I.] EXTERNAL PERCEPTION. 
 
 tion on which we were accustomed to reckon, we do not 
 ascribe the change to ourselves, but to the body ; we say that 
 it has changed its position, figure, size, temperature, color, 
 taste, smell, and though its history may be only definable by 
 us through ours, we confront its history with ours, as a series 
 of events opposed to another series of events. 
 
 On this two new series of properties become added to it, 
 and perfect its being. On the one hand we observe that it 
 is capable of certain precise changes under certain precise 
 conditions ; it may change place, figure, magnitude, consist- 
 ence, color, smell ; may be divided, may become solid, liquid, 
 gaseous, be heated, cooled, etc. We conceive it with relation 
 to its possible events as we conceived it with relation to our 
 possible sensations, and, to the first group of possibilities and 
 permanent necessities by which we constituted it, we associ- 
 ate a second. On the other hand we observe that certain of 
 its events excite certain changes in other bodies. The mar- 
 ble in motion displaces another marble. An acid solution 
 reddens litmus paper. The heated stove evaporates water 
 placed on it. A scrap of heated iron brought near a ther- 
 mometer dilates the alcohol. By these various observations 
 we prove that certain bodies are capable, under certain precise 
 conditions, of exciting certain changes in other bodies, and 
 we no longer define them by reference to our events, nor by 
 reference to their own events, but by reference to the events 
 of the other bodies. In this respect, too, a body is still a group 
 of permanent possibilities and necessities, and, with these 
 three relationships, we have completely constituted it. It 
 can, and under certain conditions it must, excite in us certain 
 muscular and tactile sensations of resistance, extension, figure, 
 and situation, certain sensations of temperature, color, sound, 
 taste, and smell: these are its sensible properties. It can, and 
 under certain conditions it must, go through certain changes 
 of consistence, extension, figure, position, temperature, taste, 
 color, sound, and smell : these are what we may call its in- 
 trinsic properties. It can, and under certain circumstances 
 it must, excite in some other body some change of consistence 
 or extension, or figure, or position, or temperature, or of taste, 
 smell, color, and sound : these are its properties with relation to
 
 276 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 other bodies. All these properties exist only with relation to 
 events; to state them is to predict some event of ourselves, 
 of the body in question, of another body, to enunciate it as 
 possible under certain conditions, as necessary under the 
 same conditions with a complementary one added to them, 
 in short, to state a general law ; and all these events, our 
 own, those of the body in question, those of the other bodies, 
 are defined in final analysis by our events. 
 
 The case is altered, when, from among this enormous multi- 
 tude of properties, we attempt to set aside fundamental proper- 
 ties. Sentient beings are but a rank in the prodigious army of 
 distinct beings which we observe or divine in nature, and our 
 events are but a trifling quantity in the enormous mass of 
 events. The Ego is a single reagent among a hundred mil- 
 lion others, one of the most perishable, one of the most easily 
 deranged, one of the most inaccurate, one of the most insuffi- 
 cient. In the place of its notations we substitute other equiv- 
 alent notations, and we define the properties of bodies, not 
 by our events, but by certain of their events. Instead of our 
 feeling of temperature we take as guide the elevation or low- 
 ering of the alcohol in the thermometer. Instead of the mus- 
 cular sensation we experience in raising a weight, we take as 
 guide the elevation or lowering of the scale of the balance. 
 Among these indicating events, there is one which is very sim- 
 ple and more universally spread through nature than any other 
 motion, or passage from place to place, with its different 
 degrees of velocity. We first observe it in ourselves ; the 
 primitive notion we have of it is that of the more or less en- 
 ergetic muscular sensations, whose longer or shorter series ac- 
 companies the bending or extension of our limbs. Just as, by 
 analogy and induction, we attribute to organized bodies, sen- 
 sations, perceptions, emotions, and other events similar to our 
 own, so we attribute to all bodies motion similar to our own. 
 But, as by verification and rectification, we gradually limit the 
 too close resemblance we at first imagined between the in- 
 ferior animals and ourselves, so we gradually limit the too 
 great resemblance which we at first imagined between the 
 motion of inanimate bodies and our own. The child believed, 
 and has ceased to believe, that its hoop jumped and ran away,
 
 CHAP. I.I EXTERNAL PERCEPTION. 277 
 
 that its ball ran at it and tried to hurt it. Men imagined and 
 have at last ceased to imagine the flight of the projectile as 
 an effort* analogous to their own ; they have recognized the 
 metaphor for a metaphor, and have reduced it so that it may 
 correspond with a body incapable of intention and sensation. 
 Instead of conceiving motion as a series of successive sensa- 
 tions interposed between the moments of departure and ar- 
 rival, he now conceives it as a series of successive states inter- 
 posed between the moments of departure and arrival ; by this 
 retrenchment, the kind and quality of the elements which 
 compose the series are omitted ; nothing remains but their 
 number and order, and the notion is applicable, not merely 
 to sentient bodies, but to all bodies. 
 
 This being settled, he gradually discovers that, in his 
 definitions of bodies and their properties, a mode or par- 
 ticularity of motion so conceived may take the place of his 
 sensations. He called that solid which excited; in him the 
 sensation of resistance ; he now calls solid whatever arrests 
 the progress of any body in motion. He conceived empty 
 space by his muscular sensations of free locomotion ; he now 
 conceives it by the unarrested motion of any body whatever. 
 He represented lines, surfaces, and solids by more and more 
 complex groups of which his sensations of locomotion, con- 
 tact, and resistance formed the elements ; he now defines the 
 line by the motion of a point ; the surface by the motion of 
 a line ; the solid by the motion of a surface. He estimated 
 force by the magnitude of his -sensation of effort; he; now 
 measures it by the velocity of the motion it impresses on a 
 given mass, or by the magnitude of the mass on which it 
 impresses a motion of a given velocity. He thus attains the 
 conception of body as a movable motor, of which velocity and 
 mass are equivalent aspects. Thus, all the events of-physi- 
 cal nature are motions, each of them being defined by the 
 mass and velocity of the body in motion ; and each being a 
 quantity which passes from body to body without ever in- 
 creasing or diminishing. Such is at present the mechanical 
 idea of nature. Among the various classes of events by 
 
 * Nisus.
 
 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 which we can define things, man chooses one, refers to it the 
 majority of the others, and imagines that some day he will 
 be able so to refer the rest. But if we analyze the one he 
 has chosen, we discover that all the original and constituting 
 elements of his definition are, like the definitions of all the 
 rest, nothing more than sensations, or more or less elaborated 
 extracts from sensations. 
 
 VII. Among these extracts from sensation by which, in 
 final analysis, we invariably conceive and define bodies, is 
 there any one which we may legitimately attribute to them ? 
 Or are bodies, indeed, nothing more than a simple collection 
 of permanent powers or possibilities, of which we can affirm 
 nothing except the effects they excite in us? Or, indeed, as 
 Bain and Mill, following Berkeley, think, are they pure non- 
 entity, erected by an illusion of the human mind into sub- 
 stances and external things ? Is there nothing more in nature 
 than series of transient sensations which constitute sentient 
 subjects, and the durable possibilities of these same sensa- 
 tions ? Is there nothing intrinsic in this stone ? Do we 
 only discover in it relative properties, for instance, the pos- 
 sibility of certain tactile sensations for a sentient subject, the 
 necessity of these same tactile sensations for the sentient 
 subject who will give himself a certain series of muscular sen- 
 sations, that is to say the series of muscular sensations in 
 consequence of which his hand will arrive at touching the 
 stone ? We have already seen that what constitutes a dis- 
 tinct being, is a distinct series of facts or events. Consequently, 
 in order that this stone maybe, not the simple permanent pos- 
 sibility of certain sensations of a sentient subject, a vain and in- 
 effectual possibility in case all sentient subjects were sup- 
 pressed, it is necessary that it should be, in addition, a distinct 
 series of facts, or of real or possible events events which would 
 still be produced in the absence of all sentient beings. May 
 we by induction and analogy attribute to it such a series? All 
 followers of Berkeley are agreed that we may legitimately do 
 so by induction and analogy, when, instead of a stone, we are 
 dealing with a sentient subject, man or animal, other than 
 ourselves. In this case not only do we conceive the object 
 perceived by our senses as a collection of permanent possi-
 
 CHAP. I.] EXTERNAL PERCEPTION. 279 
 
 bilities, but more than this, we rightly attribute to It a series 
 of sensations, images, and ideas, more or less analogous to 
 our own, and we legitimately transfer to it events which pass 
 in us. By this transfer, instead of the simple possibility 
 which it was, it becomes an actual thing in the same way as 
 ourselves, and we recognize in it a distinct existence, inde- 
 pendent of ours, since the events which constitute it, though 
 proved by us, have no need of our events for their production 
 and succession. 
 
 Is there any series of internal events which we may, still 
 by induction and analogy, transfer from ourselves to the stone, 
 in order to confer on the stone the independent and distinct 
 existence which we have conferred on the being similar to 
 ourselves or on the animal? Yes, certainly, at least in my 
 opinion, and by means of preliminary eliminations. As we 
 have seen just now, from the series of muscular sensations 
 by which we conceive motion, we cut away all the characters 
 which can distinguish it from another series. After this 
 great suppression, it is nothing more for us than an abstract 
 series of successive states, interposed between a certain initial 
 moment and a certain final moment. Each of these com- 
 ponent states has been stripped of all qualities, and is defined 
 only by it position, in the series, as being nearer or more dis- 
 tant from the initial or the final moment. It is this series 
 more or less short, of successive states comprised between 
 an initial moment and a final moment, and defined only by 
 their reciprocal order, that we term pure motion. Now, we 
 have all the reasons in the world to attribute this to the r~ 
 known things we term bodies, to be certain that i 4 " 
 from one to another of them, and to lay down tl 
 such communication. In fact, if all sentient being 
 pressed, our stone would still subsist ; and this does 
 mean that the possibility of certain visual, tactile, aim orner 
 sensations would still subsist ; it also means that the unknown 
 things we term molecules, and which make up the stone, 
 would still subsist ; in other words that the movable motive 
 powers of which the stone is the aggregate would continue 
 to weigh on the ground proportionately to their mass, and 
 would go through the same internal oscillations as they do at
 
 2 8o THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 present. Whatever be the being, animate or inanimate, we 
 may consider it in two aspects, with relation to others, and 
 in itself. In relation to others, it is a condition of events for 
 the others, and, especially with relation to us, it is a condition 
 of sensations for us ; in this respect it is determined, but solely 
 with relation to us, and we can say nothing more of it than 
 that it is the permanent possibility of certain sensations for 
 us. On the other hand, in itself, it is a series of events which, 
 in certain conditions, tend to be accomplished ; in this respect 
 it is determinate in itself, and we may say of it that it is this 
 series conjoined to the tendencies by which it is accomplished. 
 This man is, first, the permanent possibility of tactual, vis- 
 ual, and other sensations, which I experience in his neighbor- 
 hood ; and further, he is a distinct series of sensations, images, 
 ideas, and volitions, conjoined to the tendencies by which 
 this series is accomplished. So, too, this stone is, first, the 
 permanent possibility of visual, tactile, and other sensations, 
 which I experience in its neighborhood ; and further, it is a 
 distinct group of tendencies to motion, and of distinct motions 
 in way of being accomplished. 
 
 No doubt, we know nothing of animate or inanimate beings 
 except from the sensations they give us. No doubt, too, the 
 various materials with which we internally construct their idea 
 are our sensations, or more or less elaborated extracts from 
 our sensations. But we may, upon authentic evidence, refer 
 to things external, some of these more or less transformed 
 and reduced materials, and attribute to such things a distinct 
 "xistence without us, analogous to that which they have within 
 v e are naturally inclined by imagination and sympathy 
 Deration. At the sight of a rocket fired off, just as 
 .t of a flying bird, we involuntarily put ourselves 
 j of the object ; we mentally repeat its flight ; we 
 mutate it by our attitude and gestures. Infant nations, in 
 whom this aptitude is intact, carry it out to far greater ex- 
 tents than we do. The primitive man, Aryan or Greek, bes- 
 towed his soul upon fountains, rivers, mountains, clouds, the 
 air, upon all the aspects of the heavens and the day ; he saw 
 in inanimate things, living beings similar to himself. Gradu- 
 ally, by means of experiences and verifications, we have re-
 
 CHAP. I.] EXTERNAL PERCEPTION. 2 8l 
 
 strained this too complete transference of ourselves to exter- 
 nal things. At present, we have reduced it to a minimum ; 
 we have suppressed even the last vestiges of the primitive 
 error ; we no longer attribute to inanimate things, attrac- 
 tions, repulsions and efforts, conceived on the model of our 
 mental states denoted by these words ; when we use such 
 language, we know that it is merely by approximation and 
 metaphor. If we attribute motion to bodies, it is after strip- 
 ping its elements of all human qualities, after taking from 
 them all the characters by which they were at first sensations, 
 by carefully leaving nothing of them but their relative order, 
 their position in relation to the inital and final moment, their 
 more or less speedy succession in the same interval of time. 
 In this state of extreme attenuation and curtailment, the con- 
 tinuous series of successive events constituting the motion of 
 a stone we throw, is nothing more than a very slight extract, 
 the slightest possible extract, of that continuous series of 
 successive muscular sensations first constituting to us the 
 motion of our hand. But we may justly attribute such a series 
 to the stone, and in this respect, it is to us a being as real, 
 as complete, as distinct from us, as any particular man or 
 horse.* 
 
 * By this addition to the theory of Bain and Mill, we restore to bodies an actual 
 existence, independent of our sensations. But the theory, with the aid of this ad- 
 dition, leads us much further, and enables us to complete the views we have al- 
 ready presented upon the relations of physical and mental events. (See part i. 
 book iv. ch. ii. p. 200.) 
 
 It follows, from the analysis of motion, that it is not absolutely heterogeneous 
 to sensation : for our idea of it is formed from the materials supplied by our mus- 
 cular sensations of locomotion. In the series of successive muscular sensations 
 which make up a whole sensation of locomotion, strip the component sensations 
 of all intrinsic quality and difference ; consider them abstractedly, as pure succes- 
 sive events, determined solely by their relative order in the series, and by the whole 
 time they take to succeed one another in this order from the initial to the final 
 moment ; it is this abstract series which constitutes to us the movements of our 
 arm, and which we attribute by induction and analogy to the stone our hand carries 
 with it. Now, the elements of this abstract series being thus brought down to the 
 maximum degree of possible simplicity, maybe considered as elementary sensation at 
 their maximum of possible simplicity. In such a case the most simple motion, 
 such as we attribute to a movable point, would be precisely the most simple series 
 of those elementary mental events, whose degraded forms we have seen extending, 
 while becoming still more degraded, under the compound mental events, sensations,
 
 282 THE KNOWLEDGE OF BODIES. [Boux II. 
 
 VIII. We now know the materials by whose assemblage 
 the conception of a body is formed. All these materials are 
 images of sensations, possible under certain conditions, and 
 necessary, under the same conditions, with a complementary 
 one added. When nothing contradicts this conception, and 
 when, instead of being repressed and negative, it is excited and 
 sustained by the actual sensation, it is affirmative and becomes 
 a judgment. Therefore, we now see the part it plays in an 
 external perception. I lay my hand in the dark on this mar- 
 ble table, and I have an actual sensation of contact, of resist- 
 ance, and of cold. Upon this sensation, images arise of many 
 distinct and interconnected sensations, that of the precisely 
 similar sensations of contact, resistance, and cold, which I 
 should experience if I repeated the trial, that of the nearly 
 similar sensations of contact, resistance, and cold, which I 
 should experience if I placed my hand beyond the spot I 
 touched, that of the muscular sensations of locomotion, dur- 
 
 and images, of which we are conscious. Sensations and images would thus be 
 but more complex cases of motion. By this reduction, the two idioms, of con- 
 sciousness and of sense, by which we read the great book of Nature, would be re- 
 duced to a single one ; the mutilated text and the mutilated interlinear translation 
 which mutually supply one another would be one and the same tongue, written in 
 different characters, with more complex characters in the supposed text, with more 
 simple characters in the supposed translation, and the link connecting the trans- 
 lation and the text would be found in the relation discovered between our idea of 
 motion and the muscular sensation of locomotion which supplies the elements of 
 this idea. 
 
 If this be admitted, we are enabled to include nature in a general glance. 
 The simultaneous series of successive events composing it would be all homogene- 
 ous. Their type would be furnished us by the sensation as we observe it in our- 
 selves, and in the elementary sensations, more and more degraded and simplified, 
 of which this whole sensation is made up. At tlie extreme limit of simplicity all 
 would be reduced to motions, which would themselves be nothing more than con- 
 tinuous series of infinitesimal sensations, stripped of all quality, and definable only 
 in respect of quantity, that is to say by the duration employed in their accomplish- 
 ment, and by the magnitude of the succeeding effect. In this respect, all the facts 
 and events of nature might be reduced to motions, and our sciences, all of which 
 have for their object the discovery of simple elements, might all be reduced, as in- 
 deed all tend to be reduced, to mechanics. But this would be so, from the analyt- 
 ical aspect only. Motion itself would be conceivable only by the series of muscu- 
 lar sensations of which it is the most slender extract, and, directly, the type of ex- 
 istence would be the mental event, sensation, or image, just as consciousness pre- 
 sents it to us.
 
 CHAP. I.] EXTERNAL PERCEPTION. 283 
 
 ing which these tactile sensations would be received, and at 
 whose expiration they would be no longer received, that of 
 the visual sensations of color and form, which would arise in 
 me if there were light and my eyes were open, etc. I further 
 believe that, by placing myself under the required conditions, 
 not only might I experience the sensations in question at 
 any moment of the future, but, moreover, that I might have 
 experienced them at any moment of the past, and that the 
 same would happen at any moment of the present, past, 
 or future, with every being analogous to myself. 
 
 In this group of images called up by the sensation, two 
 things must be distinguished, the images themselves, and the 
 reflection by which I remark the permanent possibility, at all 
 times and for every sensibile being, of the sensations which 
 they represent. The first of these two things is animal, the 
 second is human. In fact, animal experience is sufficient to 
 attach the group of images to the sensation ; we have seen 
 the laws of revival and association which form and arouse it. 
 When a dog touches the table, all the images we have enu- 
 merated arise in him as in us ; consequently he can foresee, 
 as we do, that if he runs against the table he will be bruised, 
 that if he lies down on it he will feel cold, that if he opens 
 his eyes to look at it he will have a certain visual sensation. 
 This is sufficient to enable him to avoid danger, to provide 
 for his wants, to direct his proceedings. If he sees, smells, or 
 touches a piece of meat, he has, by revival and association, 
 the image of a sensation of pleasant taste, and this image in- 
 duces him to snap it up. When he sees a lifted stick or hears 
 the crack of a whip, he has, by revival and association, the 
 image of a painful sensation of touch, and this image induces 
 him to run away. In his case there is nothing more ; he is 
 not possessed of language, he has not the means of discerning 
 and isolating the characters of his image. We have these 
 means, and avail ourselves of them. The child learns the 
 words table, stick, meat, stone, tree, and others ; they gradual- 
 ly become equivalent for him to the group of animal images 
 which first constituted his whole perception. He incessantly 
 avails himself of them ; when grown up, he enquires into 
 their meanings and couples them. The man then observes
 
 284 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 that the sensation of which he has the image was possible 
 just before, that same morning, the day before, that it will 
 be possible presently, this evening, to-morrow, and at every 
 intervening moment, and not only for him, but for evey be- 
 ing analogous to himself. He notes this possibility; he dis- 
 engages it from the sensations in which it is included ; he is 
 struck by the singularity of its independence and permanence 
 in the midst of the continuous flow and manifest dependence 
 of the sensations. He denotes it by the words property, 
 power, force. As it is independent and permanent, it seems 
 to him alone worthy of attention, and henceforth, to fill the. 
 scene of being, he puts it into the first rank with other simi- 
 lar Possibilities. He correspondingly discards or lays aside 
 as of small importance fugitive sensations, and, owing to their 
 omission, forgets that properties, powers and forces are but 
 extracts from them. He attempts to consider, apart and in 
 itself, this permanent and independent thing which he has only 
 isolated by an oversight. Thus, he creates an empty sub- 
 stance ; metaphysics sets to work and builds her card-castles 
 upon this entity ; in order to upset them the most rigorous 
 analysis is hardly sufficient. There remains, then, to consti- 
 tute the perception of a body, first, an actual sensation and 
 an associated group of images, next, the conception, that is 
 to say the extraction and notation by means of a sign, of a 
 character common to all the sensations represented by these 
 images, a permanent character which, when interpreted by 
 metaphysical illusion, becomes isolated and appears a separate 
 being. Sensations and images, these form the crude and 
 primitive materials ; gradual and superadded abstraction com- 
 pletes the edifice. Here we have the first foundation of the 
 hallucinatory semblance which arises in us, when, upon a sen- 
 sation, we conceive and affirm an extended, resisting, mova- 
 ble substance, localized, and possessed of other sensible prop- 
 erties. The operation which completes it and opposes it to 
 ourselves, by casting it into the distance and situating it with- 
 out us, remains to be described.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 285 
 
 CHAPTER II. 
 
 EXTERNAL PERCEPTION AND THE EDUCATION OF THE SENSES. 
 
 I. ALONG with the great mental process of which we have 
 been speaking, another is accomplished, as involuntary, as si- 
 lent, and as fruitful in illusions and cognitions. Every special 
 sensation becomes transformed, and acquires an apparent posi- 
 tion. We never now experience a sensation without assign- 
 ing it a place. As soon as we have an impression of cold, of 
 heat, of pain, of contact, of muscular contraction, of taste, of 
 smell, we can point out more or less precisely the spot at which 
 we feel it, as in the hand, the cheek, the middle of the arm, 
 the nose, the tongue. There is no appreciable interval be- 
 tween this judgment and the sensation itself; we are even 
 tempted to believe that the two events are one, and that we 
 observe, at the same moment, the twitch of pain and its lo- 
 cality. There is, though, an interval between these two ob- 
 servations, and the delicate processes employed by physiolo- 
 gists have recently succeeded in measuring it ;* the fact is 
 that the operation by which we localize our sensation in a 
 particular spot of one of our limbs is a subsequent and more 
 or less complex addition, whose more or less numerous mo- 
 ments require for their succession a longer or shorter time.f 
 
 * Experiments of Helmholtz, Marey, De Bezold, Hirsch, Van Deen, Donders, 
 De Jaager, Wolf. Collected and summed up by M. Radau, in the " Revue des 
 Deux Mondes," I Aug. 1867, p. 794. 
 
 f M. de Jaager told the person on whom he was experimenting to touch the 
 key of the electric machine with his left hand, when he received the shock on his 
 right side, and with his right hand when he received the shock on his left side. 
 Thus, two cases were presented. Sometimes the person was told beforehand that 
 the shock would be received on a particular side, the right, for instance ; in this 
 case, the interval between the shock he received and the consecutive signal he gave 
 amounted to '2 of a second. Sometimes he was not told on what side he would
 
 2 86 THE KNOWLEDGE OF BODIES. [BooK II. 
 
 By this localizing operation our sensation receives a false 
 appearance, arid this appearance begets others, which are, in 
 themselves, illusions, but which, by their correspondence with 
 things, constitute the perfectionment or education of the 
 senses. When once the sensation has arrived at this state, 
 the bodies it reveals to us correspondingly receive new char- 
 acters ; the hallucinatory semblance which constitutes exter- 
 nal perception is completed ; and the object, which appeared 
 only as something permanent and fixed, now appears as some- 
 thing beyond us and without us. 
 
 II. I put my foot to the ground ; I experience a sensation 
 of pressure, and determine that it is situated in my left foot, 
 that it is strong in the middle of the foot, light at the heel, 
 scarcely perceptible at the toes. Let us consider this conclu- 
 sion ; taken in itself, it is false ; the sensation is not in my 
 foot. In this case, physiologists long ago detected the error 
 and established the theory. The truth is that a disturbance 
 is produced in the\ nerves of the foot, of greater extent in the 
 
 receive the shock, and the shock came, for instance, from the right ; in this case 
 the interval between the shock he received and the consecutive signal he gave 
 amounted to "2.1 of a second. The difference, then, between the two cases amount- 
 ed to '07 of a second. It is clear that in each case the crude sensation was produ- 
 ced at the same instant ; but, in the first case the image of the shock on the right 
 was fully prepared to enter on the scene, and was not counterbalanced, as in the 
 second case, by the equal readiness of the image of the shock on the left. To up- 
 set this equilibrium, and to permit the image of the shock on the right to attach 
 itself by selection to the supervening sensation, required a certain time, and by the 
 experiment the time required is '07 of a second. In general, between a sensation 
 and a consecutive signal there elapses two-tenths of a second, and, if the sensation, 
 that of a momentary sound, of an electric shock, of a spark, requires to call up an 
 auxiliary image, it employs, when this image is not in readiness or is counterbal- 
 anced by another, one-tenth of a second longer than when this auxiliary image is 
 in readiness, or has no antagonist. Images, then, require an interval of time to 
 connect themselves to the sensation, and this interval is increased when their call- 
 ing up is less prepared or more disputed. 
 
 MM. Bonders and De Jaager made the experiment in a slightly different man- 
 ner. One of them pronounced a syllable, the other repeated it as soon as he heard 
 it ; the vibrations of the word were registered by a phonautograph ; when the re- 
 peated syllable had been agreed on beforehand, the difference observed was two- 
 tenths of a second ; in the other case, it was three-tenths. Analogous results were 
 obtained by an observer noting the appearance of a white or red light, and being, 
 in turn, informed and not informed which would be shown.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 2 8/ 
 
 sole, and of less at the toes and heel, that this disturbance is 
 communicated throughout the whole course of the nerves to 
 the sensory centres of the encephalon, and that the sensation 
 really takes place in the encephalon. We are mistaken in 
 situating it in the periphery of the nervous system, it is at 
 the centre ; what is produced in the foot is not the sensation, 
 but the commencement of the nervous disturbance of which 
 the sensation is the final result. 
 
 There are superabundant proofs of this. They may be 
 all summed up by saying that, in many instances, the sensa- 
 tion appears situated in a place where it certainly is not. By 
 means of these instances we prove a general law : that, in our 
 present state, as soon as a sensation arises, it is accompanied 
 by a judgment in which we pronounce it to be situated in 
 some particular spot. It may be that, in such a case, there 
 actually is a nervous disturbance at this spot, or, it may be, 
 that there is no such disturbance there. It matters little ; 
 the judgment takes place in the second case as well as in the 
 first, the sensation, by itself, is sufficient to give rise to the 
 judgment, and acquires through the judgment an apparent 
 situation. The situation, then, was acquired in the first case, 
 when nervous disturbance was existing at the indicated spot, 
 just as in the second case, in which no nervous disturbance 
 was existing there. When once it is established, in accord- 
 ance with the second case, that a certain position attributed 
 to a certain sensation is apparent only, it invincibly follows 
 that, in the first case, the same position attributed to the same 
 sensation is also apparent only. If, then, in the first case, 
 we find anything at all at the indicated spot, it is not the sen- 
 sation, but one of its antecedents or consequents, an event 
 connected with it, and which it denotes, a real event, no doubt, 
 but other than the sensation, and which, by a happy correspon- 
 dence, usually accompanies the sensation in the normal state. 
 
 Let us now consider the cases by which we are undeceived. 
 There is, first, a class already mentioned, that of persons who 
 have lost limbs. " It is a fact," says Mueller, " known to all 
 surgeons, and subject to no exception, that when a limb has 
 been removed by amputation, the remaining portion of the 
 nerve which ramified in it may still be the seat of sensations,
 
 288 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 which are referred to the lost part. It is usually said that 
 the illusion continues for some time, namely, as long as the 
 patient is under the care of the surgeon ; but the truth is, 
 that in most cases it persists throughout life : of this it is easy 
 to convince oneself by questioning a person whose limb has 
 been amputated, at any period after the operation. The sen- 
 sations are most vivid while the surface of the stump and the 
 divided nerves are the seat of inflammation, and the patient 
 then complains of severe pain felt as if in the whole limb which 
 has been removed. When the stump is healed, the sensa- 
 tions which we are accustomed to have in a sound limb, are 
 still felt ; and frequently throughout life there is a tingling, 
 and often pain, felt, which are referred to the parts that are 
 lost. These sensations are not of an undefined character ; 
 the pain and tingling are distinctly referred to single toes, to 
 the sole of the foot, to the dorsum of the foot, to the skin, 
 
 &c I have convinced myself of the constancy of 
 
 these sensations of their continuance throughout life al- 
 though patients become so accustomed to them as to 
 
 cease to remark them A man whose thigh had been 
 
 amputated, still had, after the expiration of twelve years, 
 feelings which seemed to be in the toes and sole of the lost 
 
 foot, and occasionally severe pains referable to the sole 
 
 I applied a tourniquet to the stump, so as to press upon the is- 
 chiatic nerve ; and he immediately said that he felt his leg asleep, 
 
 and a very distinct tingling in the toes Another, who 
 
 had his arm amputated above the elbow, thirteen years ago, 
 has never ceased to have sensations as if in the fingers. He 
 imagines that he feels the hand in a bent position. He feels 
 a pricking in the fingers, particularly when he lies upon the 
 stump, so as to press the brachial nerves. I applied pressure 
 to the nerves in the stump ; and he immediately felt the whole 
 
 arm, even the fingers, as if asleep Another, whose 
 
 right arm had been shattered by a cannon-ball in battle, 
 above the elbow, twenty years ago, and afterwards amputa- 
 ted, had still, at changes of the weather, distinct rheumatic 
 pains, which seemed to him to exist in the whole arm ; and 
 though removed so long ago, the lost part was, at those times, 
 felt as if sensible to draughts of air. This man also com-
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 289 
 
 pletely confirmed our statement, that the sense of the integ- 
 rity of the limb is never lost." * These illusions are strongest 
 at night ; the patients are sometimes then compelled to put 
 their hands to the spot where their limb ought to be, to con- 
 vince themselves of its absence. When the subsisting por- 
 tions of the nerves become painful, they have still more diffi- 
 culty in rectifying their error ; one man, after eight months 
 had elapsed, could only undeceive himself by feeling at night 
 and looking by day at the empty place left by the amputation 
 of his left arm. It is plain that in all these cases the sensa- 
 tion of twinging, of the limb being asleep, of tingling, of pain, 
 is not situated in the absent limb, therefore the same sen'sa- 
 tion is not situated in the limb, when the limb is there ; thus, 
 in the two cases, in the normal and the abnormal state, the 
 sensation has not the situation we attribute to it ; it is else- 
 where ; it is not the sensation, but a nervous disturbance 
 which, in the normal state, occupies the place at which the 
 sensation seems to be. The nerve is a simple conductor; 
 from whatever point its disturbance may start on its way to 
 arouse the action of the sensory centres, the same sensation 
 is produced, and involves the play of the same internal mech- 
 anism, that is to say, the attribution of the sensation to some 
 spot other than the sensory centre. 
 
 Numbers of facts are explicable by this observation : a 
 violent blow on the cubital nerve excites a pain which ap- 
 pears to be situated through all the ulterior course of the 
 nerve, especially at the back and palm of the hand, in the 
 fourth and fifth fingers. The same thing happens, if the 
 elbow be plunged into a mixture of water and pounded 
 ice. Again, when the cubital or sciatic nerve is compressed, 
 the feeling of pricking or of being asleep seems to be ex- 
 perienced by the internal parts of the limb. " In .an ampu- 
 tation," says Mueller,! " at the moment of the division of 
 the nerves, the most violent pains are felt, as if in the part 
 which is being amputated, and to which the divided nerves 
 are distributed. The experienced surgeon of the Hamburg 
 
 * Mueller, " Physiology " (tr. Baly), i. 694, 695, . 
 f Mueller, op. cit. (tr. Baly), i. 691. 
 19
 
 290 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 hospital, Dr. Fricke, assures me that this is a constant phe- 
 nomenon." For the same reason, disease of the nervous 
 trunk, or of the marrow, excites pains or tinglings which 
 the patient believes to be situated in the healthy extremities 
 of his limbs. So, too, certain paralyzed persons, whose exter- 
 nal parts are wholly insensible to pricking and burning, still 
 feel in them pains and twitchings. Lastly, take the cases in 
 which the peripheral parts of the nerve are not paralyzed, 
 but displaced, as happens in the transposition of portions of 
 skin. The sensation, being the same as before the transpo- 
 sition, will be accompanied by the same localizing operation, 
 and will appear situated in the original spot. In fact, " when, 
 in the restoration of the nose, a flap of skin is turned down 
 from the forehead and made to unite with the stump of the 
 nose, the new nose thus formed has, as long as the isthmus 
 of skin by which it maintains its original connections remains 
 undivided, the same sensations as if it were still on the fore- 
 head ; in other words, when the nose is touched the patient 
 feels the impression on the forehead."* We may confidently 
 decide, then, that the sensation, though really situated in 
 the sensory centres, has the property, at least in our present 
 state, of invariably appearing to be situated elsewhere. 
 
 Let us follow out the examination ; our assurance will be 
 further strengthened, and we shall begin, at the same time, 
 to distinguish the law which regulates the localizing opera- 
 tion. In all the foregoing cases it localized our sensation 
 at the periphery of the nerve, from which the nervous dis- 
 turbance resulting in the sensation usually starts. But this is 
 not always so. There are parts of our bodies, like the teeth 
 and hair, which are not provided with nerves, and which are, 
 in themselves, wholly insensible ; but still we situate many 
 of our sensations at the external extremities of these parts, 
 where no nervous disturbance can possibly be produced.f 
 " If some part of the beard," says Weber, " for instance, at 
 the side of the cheek, be lightly touched, where do we imagine 
 that we feel this pressure exercised on the hairs of our skin ? 
 
 * Mueller, op. cit. (tr. Baly), i. 697. 
 
 f Weber, Article Tastsinn in the " Handworterbuch " of Rudolph Wagner, 
 iii, part ii. p. 488 et seq.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 201 
 
 Not in the sensible parts, to which it is propagated through 
 the horny cylinders, and at which it acts on our nerves, but 
 
 at some distance from the skin If we put a little 
 
 piece of wood between our teeth, and press it with them, 
 we imagine the resistance it offers to be situated at the sur- 
 face of the teeth, where, however, there are no nerves, 
 and where, consequently, we can feel nothing. On the 
 other hand, we have no feeling whatever of the pressure ex- 
 ercised on the internal surface of the root of the tooth in the 
 alveolus in which it is hidden ; though this is where the pro- 
 pagated pressure is actually exercised upon the highly ner- 
 vous membrane surrounding the root of the tooth, and is the 
 only spot at which it acts on our nerves." Further than this : 
 " not only do we wrongly situate pressure acting on the sur- 
 face of the insensible substances growing from our skin, but 
 we also make the same error when we place a little stick be- 
 tween our fingers and feel with it a resisting body, as for in- 
 stance, the 'table." In this case, two sensations are simultane- 
 ously produced, one which appears to be situated at the ex- 
 tremity of our fingers, the other at the extremity of the stick. 
 If the stick be fixed to the extremity of our fingers and mov- 
 able at the other end, the first sensation is effaced and the 
 second predominates. If the stick is movable at the extrem- 
 ity of our fingers and fixed at the other extremity, the inverse 
 is the case. By this experiment we determine the law of the 
 operation ; evidently, the localizing judgment situates each 
 of our sensations in the spot in which we are accustomed to 
 meet with the cause or condition which is accustomed to ex- 
 cite it.* If, from birth, the stick had been attached to one 
 of our hands, like the long sensitive exploring whiskers of a 
 
 * Vulpian. " Lemons sur la Physiologic du Systeme Nerveux," 287. Experi- 
 ment of Paul Bert. 
 
 The tail of a rat is cut raw with a bistoury and implanted in the animal's back, 
 where it becomes grafted. The tail is then divided at about a centimetre from its 
 root. The rat will then have it growing backwards, out of its back. For the first 
 three months, there are feeble signs of sensibility when the tail is pinched. " After 
 six or nine months, the sensibility is much increased, but the animal does not yet 
 recognize the spot in which he is pinched. After a year, he is perfectly aware of 
 the spot, and will turn round to bite the pincers." We see here the proof that ex- 
 perience must intervene to enable the animal to localize its sensations.
 
 292 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 cat are attached to its cheeks and lips, like the stag's horn is 
 attached to its brow, and our beard and teeth are attached to 
 our membranes, we should situate things we came into con- 
 tact with at the end of the stick, as the cat probably situates 
 what it touches at the end of its whiskers, and the stag at the 
 end of its horns, as it is very certain we situate our contacts 
 at the extremities of our beard and teeth. 
 
 III. The consequence is that when a sensation has for its 
 usual condition the presence of an object more or less distant 
 from our bodies, and experience has once made us acquainted 
 with this distance, we shall situate our sensation at this dis- 
 tance. This, in fact, is the case with sensations of hearing 
 and sight. The peripheral extremity of the acoustic nerve 
 is in the deep-seated chamber of the ear. That of the optic 
 nerve is in the most inner recess of the eye. But still, in our 
 present state, we never situate our sensations of sound or 
 color in these places, but without us, and often at a consid- 
 erable distance from us. The ringing of a great bell seems 
 to vibrate high in the air and very far off; a railway whistle 
 seems to pierce the air at some fifty paces to the left. The 
 position, even when distant, is clearer still in the case of visual 
 sensations. This extends so far that our. sensations of color 
 seem detached from us ; we no longer observe that they ap- 
 pertain to us ; they seem to form a part of the objects ; we 
 believe that the green color which seems extended three paces 
 from us on the surface of this arm-chair is one of its properties ; 
 we forget that it only exists in our retina, or rather in the 
 sensory centres which the disturbance of the retina disturbs. 
 If we look there for it, we shall not find it there ; physiologists 
 may prove indeed that the nervous disturbance which results 
 in a sensation of color commences in the retina, just as the 
 nervous disturbance which results in a sensation of contact 
 commences in the nervous extremities of the hand or foot ; 
 they may prove that the vibrating ether strikes the extremity 
 of the optic nerve, as a vibrating tuning-fork strikes the sur- 
 face of the hand : " we have not the least consciousness of 
 this impression on the retina, even when we direct the whole 
 force of our attention to the spot. * -All our sensations of 
 
 * Weber, ibid. 482.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 293 
 
 color are thus projected out of our body, and clothe more or 
 less distant objects furniture, walls, houses, trees, the sky, 
 and the rest. This is why, when we afterwards reflect on 
 them, we cease to attribute them to ourselves; they are 
 alienated and detached from us, so far as to appear different 
 from us. Projected from the nervous surface in which we 
 localize the majority of the others, the tie which connected 
 them to the others and to ourselves is undone, and it is un- 
 done in accordance with a well-known mechanism, by the ob- 
 literation of the imaginative operation which situates the sen- 
 sation in some particular spot. 
 
 In fact, as far as we are concerned, this operation is but 
 a means: we pay no attention to it ; the color and the object 
 denoted by the color are what alone interest us. Conse- 
 quently, we forget or omit to observe the intermediate steps 
 by which we localize our sensation ; they are to us as though 
 they did not exist ; and we thereupon consider that we di- 
 rectly perceive the color and colored object as situated at a 
 certain distance off. In consequence of this, a contrast is 
 established between this sensation and others. The others 
 seem to be situated in a body belonging to us and specially 
 connected with us, which we move at will, which accom- 
 panies us in all our changes of place, which answers to all 
 our touchings by a sensation of contact, in which we situate 
 ourselves in such a way that it extends over, encloses, and 
 circumscribes our personality. Our sensations of color seem, 
 on the contrary, situated beyond this, on the surface of bodies 
 foreign to ours, beyond the limited constant circle in which 
 we are enclosed. There is nothing strange, then, if we cease 
 to consider them as belonging to us, and end by considering 
 them as something foreign to us. If they are fugitive as a 
 flash of lightning, the ring of fire described by whirling round 
 a burning coal, or an impalpable meteor, they seem to us a 
 simple event with position and shape. If, as usually happens, 
 they are stable like the color of a stone, of a flower, of a tan- 
 gible object, they seem to us a more or less permanent and fixed 
 quality of that object. 
 
 The reason of this is evident. As long as we rest our eyes 
 on the gilded frame of this mirror, the long yellow stripe per-
 
 294 THE KNOWLEDGE OF BODIES. fBooK II. 
 
 sists unchanged ; the uniform, incessant, prodigiously rapid 
 renewal of the vibrations of ether maintains it without alter- 
 ation or discontinuity ; it does not disappear unless, by a 
 voluntary and foreseen movement of which I have sensation 
 and recollection, I turn away my eyes and head. More- 
 over, whenever I look again for this yellow stripe, I invariably 
 find it in the same relative position, to the right of the dark 
 glittering surface presented by the mirror, to the left of 
 the striped gray presented by the paper of the wall. Further 
 still, the little bright or dark bands formed by the reliefs and 
 hollows of the chasing always preserve the same relative pos- 
 itions in the whole yellow stripe. Consequently, this yellow 
 is not a transitory momentary thing like a flash of lightning ; 
 it does not cease of its own accord. Experience shows me 
 that I am sure of finding it again whenever I please ; from 
 finding it present, whenever I have turned my eyes towards 
 it in the light, I conclude by induction that it is constantly 
 present, all circumstances remaining the same, at whatever 
 moment of time I have turned or may turn my eyes towards 
 it, in any moment whatever of the past or the future ; there- 
 fore it occupies them all. Its existence past and future is thus 
 prolonged indefinitely, and it is the same in all these dis- 
 tinct instants. It seems, then, a permanent quality in that 
 group of permanent possibilities we term body. 
 
 The truth, however, is that all the colors with which the 
 surrounding world seems decked are within us, and are sen- 
 sations of our optic centres ; the consideration of the sensa- 
 tions of sight we term subjective is sufficient to convince us of 
 this. These sensations undeceive and instruct us with respect 
 to sight, just as the illusions of persons who have suffered 
 amputations do with respect to touch. Color is not in the 
 object, nor in the luminous rays which spring from it ; for, in 
 many instances, we see it when the object is absent, and when 
 the luminous rays are wanting. The presence of the object 
 and of the luminous rays contribute indirectly only to 
 cause it to rise ; its direct necessary and sufficient condition 
 is the excitation of the retina, or which is more important of 
 the optic centres of the encephalon. It matters little whether 
 this excitation be produced by an impingement of luminous
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 295 
 
 ,rays, or otherwise. It matters little whether it be spontaneous 
 or not. Whatever be its cause, as soon as it arises, the color 
 arises, and, at the same moment, that which we term the 
 visible figure. Consequently, the color and visible figure are 
 but internal events, which appear external. The whole of 
 physiological optics rests on this principle, and, to convince our- 
 selves of its soundness, we have but to look at a few, among 
 the hundreds of cases in which apparent color and figure arise 
 of themselves, without any external object or pencil of lumin- 
 ous rays directly or indirectly setting the nerve in action. 
 When we have been looking steadfastly at a luminous or 
 strongly illuminated object the excitation of the retina per- 
 sists after we have ceased to look.* Hence arise the singu- 
 lar phenomena termed consecutive images. These, in fact, are 
 complete visual sensations which survive and are prolonged 
 in the absence of their object. According to circumstances, 
 in some cases the brighter portions of the consecutive image 
 correspond to the brighter portions of the object, and the 
 darker portions of the image to the darker portions of the 
 object, and in some cases the inverse. In the second case, 
 the colors of the consecutive image are the complementaries 
 of the colors of the object ; that is to say, where the object is 
 red, the image is of a greenish blue; where the object is yel- 
 low, the image is blue ; where the object is green, the image 
 is rose-colored, and vice versa. A number of analogous phe- 
 nomena have been observed, arid are explained by the persist- 
 ing excitation and diminished excitability of the retina after 
 undergoing the action of light. But there are other phenom- 
 ena of the same kind, which are produced without there be- 
 ing any need for the intervention of light. It is enough in 
 these cases if the retina be set in action by some other cause. f 
 If the eye be compressed with the finger we see luminous fig- 
 ures " sometimes annular, sometimes radiated, sometimes di- 
 vided regularly into squares. If in a room otherwise dark, a 
 lighted candle be moved to and fro, or in a circle, about six 
 inches from the eyes, we soon see a dark arborescent figure 
 
 * Helmholtz," Physiologische Optik," 356 ; Mueller, " Physiology" (tr. Baly). 
 ii. 1394- 
 
 f Helmholtz, ib. 418 ; Mueller, op. cit. (tr. Baly), ii. 1163.
 
 296 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 whose branches extend over the whole field of vision, and 
 which is nothing more than the expansion of the central ves- 
 sels of the retina, or that of the parts of the retina covered by 
 those vessels." Sometimes, after compressing the eye, this 
 arborescent figure appears luminous. " Luminous moving 
 points appear in the field of vision when we look fixedly at a 
 surface uniformly illuminated, as, for instance, the sky, or a 
 field of snow, and especially during a brisk walk or some other 
 movement of the body." In cases of plethora or congestion, 
 " when we have been lying down and suddenly rise up, we 
 see a number of little black bodies with tails to them jump- 
 ing and moving in all kinds of directions." Different narcot- 
 ics, digitalis especially, excite flashings in the eyes. And so, 
 when disease inflames or irritates the retina, flashes and 
 sparks are perceived, and, in surgical operations, which neces- 
 sitate the section of the optic nerve, the patient sees great 
 masses of light at the moment the instrument cuts the nerve. 
 But the retina and the whole optic nerve are themselves 
 but intermediate conductors ; they serve to excite the optic 
 centres of the encephalon, that is all. Suppose the centres 
 are excited and the conductors inactive ; the colored figure 
 will arise and appear internal. This is the case with hallucin- 
 ations of sight strictly so called, in which a reflected excita- 
 tion propagates the images of the hemispheres to the visual 
 centres of the encephalon. This is the case with the appear- 
 ance following the prolonged use of the microscope, when the 
 visual centres of the encephalon re-enter several times spon- 
 taneously into the state in which the action of the retina has 
 set them too often and retained them too long. These cases 
 all resemble that in which a spontaneous disturbance of the 
 acoustic nerve causes us to hear and localize at a particular 
 distance, and in a particular direction, a sound which there 
 is no vibration of the external air to produce. 
 
 Now it is plain that the color, like the sound, is then with- 
 in us, and cannot be elsewhere ; and still we project it with- 
 out us, and situate it at a spot where it cannot be. We may 
 know, indeed, by reasoning that this situation is illusory ; the 
 appearance is too strong for us ; we perceive the luminous 
 bluish circle excited by a pressure at the inner corner of the
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 
 
 297 
 
 eye, as if it were situated a little above the outer corner, not 
 in the retina, but without the pupils. Thus when we are 
 given a visual sensation to which no external object corres- 
 ponds, it excites the play of an internal mechanism which 
 transports it without us, and which, according to its kind, and 
 as it is provided with certain particular accompaniments, sit- 
 uates it in one spot or another, always at the place in which, 
 under ordinary circumstances, its ordinary cause or condition 
 usually is : the law is a general one, and explains all the illu- 
 sions of optics. Consequently, even under ordinary circum- 
 stances, when the ordinary cause or condition, that is to say 
 the object, is present, and occupies the spot denoted, when a 
 red arm-chair or a green tree is really six paces from me, the 
 internal mechanism acts just as in the exceptional case in 
 which I have a consecutive impression on the retina, or in the 
 exceptional case in which I have an hallucination proper in 
 the cerebral centres. Consequently, too, the red color with 
 which the arm-chair is clothed, the green color which seams 
 to me incorporated with the tree, is nothing more than my 
 sensation of red or of green, detached from myself and car- 
 ried, in appearance, to a distance of six paces from my eyes. 
 
 Thus, all our sensations are wrongly situated, and the red 
 color is no more extended on the arm-chair than the sensa- 
 tion of tingling is situated at my fingers' ends. They are all 
 situated in the sensory centres of the encephalon ; all appear 
 situated elsewhere, and a common law allots to each of them 
 its apparent situation. The law is that a sensation ap- 
 pears to us to be situated at the spot in which we are accus- 
 tomed to meet with its usual cause or condition, and this 
 spot is the one at which the explorations of touch are capa- 
 ble, by acting there, of checking or modifying the commenced 
 sensation. The singularities, errors, and diversities of the 
 localizing judgment are all explained by this law. 
 
 In the first place, we see that this judgment must invaria- 
 bly be false ; for the touch can never arrive at the sensory 
 centres, to check or modify the commenced sensation ; the 
 sensory centres are in the box of the cranium in a place our 
 hands cannot reach. Secondly, we see that in most cases the 
 localizing judgment must situate the sensation somewhere
 
 2^8 THE KNOWLEDGE OF BCDIES. [Boon II. 
 
 near the peripheral extremity of the nerves ; for, though the 
 excitation of the whole course of the nerve is the normal an- 
 tecedent of sensation, our touch can only attain the parts ad- 
 joining the peripheral extremity. It is, then, at this point 
 and no other of the nervous cord, that the localizing judg- 
 ment must situate the sensation. And this is true for all sen- 
 sations, even for sensations of sight, at least in the first stage 
 of their localization ; in fact, we shall presently show that per- 
 sons born blind, at the moment a surgical operation restores 
 their sight, situate colors near the periphery of the optic 
 nerve ; it is later on, after a further apprenticeship, that they 
 refer them beyond this, to the place where the objects are 
 situated. Thirdly, we see that the localizing judgment can- 
 not situate sensations at the exact spot of the periphery of 
 the nerve in action, but in its neighborhood, and in general a 
 little beyond it ; for the touch cannot reach the exact spot. The 
 finger cannot reach the retina at the back of the eye, nor the 
 pituitary membrane at the inner part of the nose, nor the 
 acoustic nerve in the labyrinth of the ear, nor, in general, any 
 nervous periphery. What it reaches, are the envelopes and 
 appendages of the nerve, the eyeball, the vestibule of the ear, 
 the anterior chamber of the nose, the surface of the skin. 
 There it is that it checks and modifies the commenced sensa- 
 tion, or associates with it a sensation of contact. There, 
 then, it is that we must situate the sensation, and it is the 
 same with sensations of sight as with all the rest ; persons 
 born blind, who have lately been operated on, situate their 
 new sensations at the surface of the eyeball, and not at the back 
 of the orbit. Fourthly, we see that in many cases the localiz- 
 ing judgment must be vague ; for there are places which 
 touch cannot reach, for instance, the internal parts of the 
 limbs and trunk ; consequently, we situate approximately and 
 vaguely all the sensations whose starting point is in the belly, 
 the chest, the stomach, just as we do the partial sensations of 
 which a total muscular sensation is composed. Numbers of 
 strange appearances are explained in the same way. If the 
 exploration of touch is brought to a stop by a fixed eminence 
 like the teeth, the sensation will appear to be situated at the 
 surface of the eminence, though the nervous disturbance is
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 299 
 
 much lower down. If the exploration of touch cannot verify 
 the positions of the two nervous disturbances, one of which 
 is situated above, the other below, as happens with impres- 
 sions of the retina, and if, at the same time, it finds the two 
 external conditions of these two impressions situated in an 
 inverse order with relation to each other, as happens with vis- 
 ible objects, we shall situate in the inverse order the two sen- 
 sations derived from them. In fact, images of objects are re- 
 versed upon the retina ; the feet of a figure are above and the 
 head below, and nevertheless, we situate the head above and 
 the feet below. The apparent position of our two sensations 
 is thus found to be the inverse of the real position of the two 
 disturbances. 
 
 It remains to be shown how, in accordance with the same 
 law, the localizing judgment situates certain kinds of sensations 
 beyond our nervous superfices. The fact is, there are two 
 stages, and the judgment, according to the nature of the sen- 
 sation, stops at the first or goes on to the second. Two kinds 
 of sensations, the visual and auditory, can alone pass through 
 b6th stages ; they alone are clearly projected from their first 
 position to some particular spot or other of the outside 
 world. The fact is, they alone furnish materials for an ulte- 
 rior localization. Take, for instance, two visual sensations. 
 Not only have they a common organic condition, the modifi- 
 cation of the open eye, but besides they have each of them a 
 special external condition, the presence in a particular spot of 
 the outer world of an illuminated body, a condition to which 
 there corresponds in them some precise and notable character, 
 according as the body is in one place or another. When by 
 feeling with the hand or by closing the eyelids, we have 
 proved their common organic condition, we prove, by other 
 feelings, and by changing our position, their different external 
 conditions. We have interrupted all our visual sensations, by 
 the same act by closing our eyelids ; we interrupt our differ- 
 ent visual sensations in different manners, by extending our 
 arm more or less, by increasing our change of position, by 
 covering with our hand the illuminated surface of the body 
 which emits the rays. Now, these are the only differences 
 which can interest us ; for these are the only indications which
 
 300 THE ^ vo WLEDGE OF BODIES. [BOOK II. 
 
 direct our action ; they alone suggest to us the number of 
 steps and the extent of the movement, by which, through 
 reaching the object, we reproduce in ourselves some anterior 
 state which was agreeable or useful to us, or, by which, in re- 
 moving ourselves from the object, we avoid some anterior 
 state which was displeasing or hurtful. Our attention, then, 
 is directed solely to these ; the general association which had 
 first joined our different visual sensations to the idea of the 
 movement by which our hand reaches our eye, is effaced as 
 useless ; the education of the eye is accomplished ; useful as- 
 sociations become established and alone subsist. Each dis- 
 tinct visual sensation is combined with the idea of a distinct 
 movement of more or less length, effected in one or another 
 direction ; it takes this idea as its associate ; henceforward, it 
 is inseparable from it. By this combination, it becomes situ- 
 ated at a greater or less distance, in one place or another, but 
 always in the outer world. 
 
 The same reasoning applies to the place of auditory sen- 
 sations. Now, if these two sorts of sensations have this sin- 
 gular peculiarity, it is because, by a special peculiarity, there 
 corresponds to each variation in the situation of their distant 
 cause, a precise variation in the sensations themselves. We 
 shall see later on how the precise variations of the sensation 
 of sight are effected by the adjustment of the crystalline lens, 
 the greater or less convergence of the two eyes, the contrac- 
 tion of the motor muscles of the eye. With respect to hear- 
 ing, whose localizations are less exact, variations less precise, 
 but still precise, are furnished by the greater or less intensity 
 of the whole sensation entering both ears, and by the greater 
 intensity of one of the two component sensations. It is not 
 the same with the other senses. Their sensations indicate 
 nothing, or next to nothing, as to position. For, first, a sen- 
 sation of contact, of pressure, of taste, is only produced when 
 the external cause touches the skin, the mouth, or the palate ; 
 at a distance, this cause does not operate : this is how the 
 sensation which it excites does not vary according to dis- 
 tance ; the localization remains checked at its first stage, and 
 we situate the sensation at or near the place, in which the ex- 
 plorations of touch meet with its organic condition. As to
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 3OI 
 
 sensations of smell and heat, in certain cases, and up to a cer- 
 tain point, we are capable of appreciating vaguely, by the 
 force or feebleness of the sensation, whether its origin is near 
 or distant ; sometimes we can even distinguish whether it is 
 on our left hand or right ; but it is nearly always necessary to 
 make a new examination. When our eyes are shut, we dis- 
 cover by smelling about, by turning the head in different di- 
 rections, that the smell comes from a bouquet placed on a par- 
 ticular side of us, that the cold comes from a particular chink. 
 But we do not know this with precision and at once ; the 
 idea of a certain movement of measurement does not present 
 itself immediately, by virtue of an ancient and fixed connec- 
 tion, and attach itself to the sensation so as to localize it in 
 one spot rather than another of the outer world. Conse- 
 quently, we remain in suspense ; we are tempted to consider 
 our sensation, sometimes as a sensation, sometimes as an un- 
 known thing which starts from without and enters us. The 
 words smell, cold, heat, remain ambiguous, and denote, in or- 
 dinary language, sometimes the one, sometimes the other; 
 this is because the second stage of localization has commenced 
 and broken down. It would not break down if the nostrils 
 were placed like the ears, on the two opposite sides of the 
 head, and could thus discern in a whole sensation of smell, two 
 sensations, one stronger than the other, or if there were two 
 symmetrical, distinct and opposed portions of the body charged 
 to receive sensations of heat. We see that the sajfte^aw-ws*^,, 
 plains both the definite and the indefinite ' sitw^utffl^V'e- attri- 
 bute to our sensations, sometimes in the neighborhood of the 
 peripheral extremities of the nerves, sometimes elsewhere and 
 at a greater distance. ^ 
 
 To sum up, in our present state, the situafWi we attribute 
 to our sensations is always false ; that which is sre^U^d-at .the, v 
 spot in which we place them is their usual cause or condition, 
 sometimes, the organ in which the primary nervous distur- 
 bance of which they are the result is effected, sometimes, the 
 external object which excites the nervous disturbance. This 
 cause or condition may be absent, as its presence is usual 
 only ; in any case, whether present or absent, the localizing 
 judgment is an illusion, since we invariably situate the sen-
 
 302 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 sation where it is not. Usually, this judgment is practically 
 effective, through the provisions it suggests and which direct 
 our conduct ; in itself it is nothing more than an illusion, 
 which is generally useful, a fundamental error which nature 
 and experience have constructed within us and established in 
 us perpetually, to act as a preservative of our life, and an or- 
 gan for our action. 
 
 IV. The localizing judgment remains itself to be studied. 
 To see of what elements it is composed, let us revert to our 
 first example. I have just put my foot to the ground, I feel 
 a sensation of pressure, and at the same time determine the 
 place of the sensation ; it is in my left foot, strong in the mid- 
 dle of the foot, slight towards the heel, almost imperceptible 
 at the toes. In what do these last observations consist ? 
 Each one of us may observe in his own case that, in order to 
 make them, we imagine with more or less clearness the foot 
 in question, and imagine it visually, that is to say by images 
 of the optical sensation it would excite in us, if we were then 
 looking at it with our eyes open. We picture to ourselves 
 the foot at a certain distance from our eyes, the curvature of 
 the sole, the form of the heel, the row of toes. We even, if 
 we persist, see mentally the color of the flesh, browner to- 
 wards the heel, whiter at the sole, and redder beneath the 
 toes. In fact, we have within us a visual chart of our body. 
 We represent it to ourselves just as we should any other ob- 
 ject of which we have ocular experience. To each distinct 
 sensation there is in the chart a distinct corresponding point, 
 which has been associated with the sensation by experience. 
 When the sensation arises, this point revives, and their junc- 
 tion situates the sensation in some particular one of the dif- 
 ferent points of the field which actual, or simply mental sight 
 is accustomed to traverse. 
 
 But it is evident that a chart like this is an ulterior and 
 special acquisition. It is wanting to persons born blind, and 
 still they are perfectly able to denote the position of their 
 sensations. They have then another chart which fulfils the 
 same office, and, as we have all their sensations, in addition 
 to the sight which they do not possess, it follows that we pos- 
 sess a second and wholly different chart, which is common to
 
 CHAP. II. j THE EDUCATION OF THE SENSES. 303 
 
 us with them, in addition to the visual chart, which is special 
 to ourselves. This second chart has as its elements muscular 
 and tactile sensations. It is composed of the images of these 
 sensations, and, in many instances, we prove their existence 
 in ourselves, as, for example, with respect to portions of our 
 body which we cannot observe with our eyes, and as to which 
 the visual chart is consequently not clear. Such, for instance, 
 is the inside of the mouth, which we can only see by the aid 
 of a glass, the back of the head, of the neck, of the trunk, of 
 the thighs, which we can only see by the aid of two glasses. 
 In fact, for all these spots, we form, from others, a sort of ap- 
 proximate chart of ourselves. But this plate of our visual 
 atlas is vague, and we seldom have recourse to it. I experi- 
 ence an itching at a point of my back, and I know the spot ; 
 but I do not know it, or only know it imperfectly, by the vis- 
 ual representation ; I do not picture clearly to myself the ver- 
 tebra or the rib, the swelling of the muscle or spinal hollow, 
 near which the feeling is ; it is not associated, as in the hand, 
 the foot, the arm, or the face, with some precise point of an 
 outline pictured by the mental eye. It is by means of another 
 atlas, the tactile and muscular atlas, that I am enabled to situ- 
 ate it precisely. 
 
 In fact I give it a situation by means of the special, longer 
 or shorter muscular sensation of the hand and arm, which 
 move towards it and reach it. Its position is denoted by the 
 nature and duration of this sensation. If at a greater dis- 
 tance, a greater movement would be required to reach it, con- 
 sequently a longer muscular sensation ; if at a less distance, a 
 less movement, consequently a shorter muscular sensation ; 
 if at the same distance, but in a different direction, a move- 
 ment equal in extent, but different, consequently a muscular 
 sensation of equal duration, but different. By means of these 
 repeated and diversified experiments, when a sensation, 
 whether of tingling or any other, is aroused in any part of my 
 body, even in a point with respect to which the visual atlas, 
 fails, it calls up its inseparable associate, the image of a spe- 
 cial muscular sensation, a sensation of a precise duration, 
 longer than some other similar one, shorter than some other 
 similar one, different from some other one of equal length.
 
 304 TIIE KNO WLEDGE OF BODIES. [BOOK II 
 
 By this attachment and consolidation, my sensation of ting- 
 ling finds itself denoted by a distinctive sign. This sign, hav- 
 ing a certain duration, is a continuous magnitude ; therefore 
 it is, like a line, capable of comparison with any other magni- 
 tude of the same kind, it differs only from such other magni- 
 tude in being more or less, suggests the idea of its double or 
 of its fraction, and is capable of measurement ; here we have 
 the conditions of a representative chart. This is but an in- 
 stance of a general operation, which has already been de- 
 scribed. We localize our sensations as we do objects, by the 
 associated image of certain muscular sensations of greater or 
 less length. The sensation, by means of the associated im- 
 age, is arrested in an order, arid, so to speak, in a rank ; there 
 it is situated, that is to say denoted by a precise quantity, 
 less than this, greater than that, by a muscular reminiscence 
 which intercalates it between two series of muscular sensa- 
 tions, one of longer sensations, the other of shorter ones. If 
 we add the reminiscence of the tactile sensations experienced 
 upon contact with the point which the exploring organ has 
 just touched, the associated image becomes precise while com- 
 pleting itself; we situate our sensation, not only at a particu- 
 lar distance from some other, but at such a rib, at such a hol- 
 low of the arm, at such a joint of the finger. Such is the 
 tactile and muscular atlas, the first of all ; the instinctive and 
 unregulated movements of the new-born child, its feelings 
 about, the incessant experience it acquires of its touch and 
 muscles, commence at once to construct this atlas ; the visual 
 atlas is derived from it, and is not formed till afterwards. 
 
 Thus the localizing judgment consists in the adjunction to 
 the sensation of certain images, sometimes visual, sometimes 
 tactile and muscular. This coupling may be innate ; the 
 chicken will pick up food immediately it comes out of the 
 shell ; the new-born foal springs on his legs almost immedi- 
 ately and goes to suck its dam. But in man it is acquired, and 
 the internal mechanism, which in other animals is fabricated 
 at the moment of birth, is in his case fabricated gradually. 
 At all events, it is for the most part a work of experience. 
 " There is ground," says Weber,* " for admitting that primi- 
 
 * Article " Tastsinn," ibid. 486.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 305 
 
 tively, by pure sensation, we know nothing of the place in which 
 the nerves which communicate the sensation to us are disturb- 
 ed. Primitively, all sensations are simple states of excitation 
 perceptible to consciousness ; these may differ in quality and 
 degree, but do not directly furnish to consciousness any notion 
 of place. They only furnish this indirectly, by exciting the 
 activity of our mind, through the means of which we repre- 
 sent our sensations as comprised in a whole, and possessed of 
 mutual relations." There is then an ulterior and superadded 
 process, the adjunction of a series of muscular images, whose 
 duration measures the distance, the adjunction of a group of 
 tactile and muscular images which denote the consistence, 
 shape, and magnitude of the organ to which the sensation is 
 referred, the adjunction of a group of visual images which de- 
 note this organ from the other organs and other objects de- 
 noted in the same manner. All this is the work of experience, 
 and experience, pushed further, is capable of associating with 
 the sensation representations of greater exactness. An anat- 
 omist who bends his hand imagines the contraction of each 
 of the muscles which concur in effecting it, the longer and 
 shorter palmar muscles, the anterior cubital, and the rest. If 
 he is pricked, he pictures to himself the form, color, and dis- 
 tribution of the little whitish flabby threads termed nerves, 
 which the puncture has touched. He represents his sensation 
 of contraction as being situated in the nerves of the contrac- 
 ted muscles, and his sensation of pain as being situated in 
 the punctured extremity of the little whitish threads. This 
 association, less fixed than ours, is identical with ours, and is 
 like a second stage of less solidity based on a first indestruct- 
 ible stage. But they are both of them added constructions, 
 and did not exist on the primitive soil. 
 
 V. If we now compare the two atlases, we shall find them 
 very different. That the first, the tactile and muscular atlas, 
 is effective for the purpose of localizing our sensations in 
 some particular part of our bodies is explainable without 
 difficulty ; for we have seen that we conceive extent, dis- 
 tance, and position by a series of muscular sensations inter- 
 posed between a point and another point between a sen- 
 sation and a sensation. I have many times experienced a 
 
 20
 
 306 THE KNOWLEDGE OF BODIES. [Book 114 
 
 feeling of touch in my neck or cheek ; I have determined 
 its position by the series of muscular sensations which my 
 hand must go through to reach it, and have characterized its 
 seat by the group of tactile sensations of my hand afforded 
 by my neck, when it is pressed, felt, and traversed. A stable 
 association is thus formed between the sensations, whose 
 starting-point is in the nerves of the neck, and this series 
 of muscular images joined to this group of tactile images. 
 Consequently, whenever a similar sensation is produced, I 
 shall imagine its position and seat. This is not the case 
 with the visual atlas, and we must examine how it is that 
 sensations of the eye, which, taken alone, seem fit only to 
 instruct us as to colors, are capable of further instructing 
 us, as to distance, extension and position. This arises 
 from their being themselves transformed, and turned into 
 equivalents of tactile and muscular sensations, by the asso- 
 ciation they have acquired with tactile and muscular sen- 
 sations. Primitively, and in itself, the retina, when im- 
 pressed, arouses sensations only of light, of obscurity, of 
 successive and simultaneous colors. It is by an ulterior 
 process the adjunction of auxiliary images that this pure 
 visual sensation receives an apparent situation, and that we 
 see objects at a certain distance, in a particular direction, 
 with particular form and dimensions. 
 
 The accounts of persons born blind, who have been 
 restored to sight by operations, is decisive as to this. From 
 the moment they recover their sight, they experience the 
 same visual sensations as we do. But their eyes have not 
 been educated like ours ; consequently, what is then want- 
 ing to their eyes is what ours have acquired ; the missing 
 parts of their perception afford a measure of the additions 
 which have gone to complete our perception. Still, for the 
 purpose of explaining the different results of experience, it 
 is necessary first to determine whether the education of 
 their eyes has been absolutely nothing or only amounting 
 to nothing.* In most cases, the crystalline lens, though 
 
 * See the cases recorded by Cheselden, " Philosophical Transactions " for the 
 year 1728. Ware, ib. 1801. Home ib. 1807. Wardrop, ib. 1826.
 
 CHAP. II] THE EDUCATION OF THE SENSES. 307 
 
 opaque, still permitted the passage of a small portion of 
 light ; Cheselden's patient could distinguish three colors, 
 black, white, and scarlet ; Ware's patient could distinguish 
 strongly-marked colors when held close to his eye. Con- 
 sequently, some of them had learned to direct their looks 
 towards an object, and could judge to a certain extent of 
 distance by the colors growing feebler. This explains 
 how, in certain cases, the patient was able immediately 
 after the operation to take hold of the surgeon's hand and 
 to say, by sight only, whether it was brought nearer to or 
 carried further from him. But this is unusual, and when 
 the patient has not learned to interpret the meaning of the 
 color growing feebler, he has no idea of the position of 
 visible objects. Usually, at the moment he first sees 
 clearly, he imagines " that all the objects he sees touch his 
 eyes, just as the objects he feels touch his skin."f So said 
 the patients of Cheselden and Home; they situated their 
 new sensation in acordance with their accustomed sen- 
 sations of touch, and applied their former experience to 
 the new instance.:}: Besides this, Home's patient had 
 always done so ; before the operation, when he looked at 
 the sun through his opaque crystalline lenses, he said it 
 appeared to touch his eye. The operation performed, the 
 same localizing judgment remained ; when asked, soon after, 
 what he had seen, he said : " Your head, which seemed to 
 touch my eye," but he could not tell its shape. It was not 
 till three months afterwards, and a month after the lowering 
 of the second cataract, that objects did not seem as before to 
 touch his eyes, but appeared to be at a short distance from 
 him. Not one of the blind persons so operated on was able 
 
 \ In a case reported by Mr. Nunnely, " the young patient said that the objects 
 touched his eyes, and walked about cautiously, keeping his hands raised before 
 his eyes, to prevent these objects from touching and hurting them." J. S. Mill, 
 " Exam, etc." Third edition, p. 285, 
 
 \ Before the operation the blind person has opened and shut his eyelids, and 
 has certainly known their situation as that of other parts of his body. Usually, 
 when the operation is performed, the light is too keen for his eyes and compels 
 him to close them, and to contract the pupil. Here are two muscular sensations 
 whose situation he knows, and which no doubt contribute to make him situate his 
 new visual sensation against his eyeball.
 
 308 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 at first to interpret his new sensations, to decide on the situ- 
 ation, form, and magnitude of objects, or to recognize them. 
 It was requisite for the touch, slowly and gradually, to in- 
 struct the eye. Home's second patient was asked, ten min- 
 utes after the operation, the shape of a round piece of card, 
 and said, " Let me touch it, and I will tell you." He was not 
 allowed to do so, and, after thinking for some time, said it 
 was round. But a moment afterwards, he said the same 
 thing of a little square piece of card, and again of a triangu- 
 lar piece. The experiment was repeated some hours after- 
 wards. At first the boy called the different cards round ; but 
 upon being shown a square, and asked if he could find any 
 corners to it, he was very desirous of touching it. This be- 
 ing refused, he examined it for some time, and said at last 
 that he had found a corner, and then readily counted the four 
 corners of the square. Thus commenced the first education 
 of the eye. All the patients resembled Cheselden's, who 
 " knew not the shape of anything, nor any one thing from an- 
 other, however different in shape, or magnitude ; but upon 
 being told what things were, whose form he before knew from 
 feeling, he would carefully observe, that he might know them 
 again ; but having too many objects to learn at once, he for- 
 got many of them ; and (as he said) at first he learned to know, 
 
 and again forgot a thousand things in a day Having 
 
 often forgot which was the cat, and which the dog, he was 
 ashamed to ask ; but catching the cat (which he knew by 
 feeling), he was observed to look at her steadfastly, and then 
 setting her down, said, ' So, puss ! I shall know you another 
 time.' " Later on, when he had learned to know his parents 
 by sight, " being shown his father's picture in a locket at his 
 mother's watch, and told what it was, he acknowledged a 
 likeness, but was vastly surprised ; asking how it could be that 
 a large face could be expressed in so little room, saying, ' It 
 should have seemed as impossible to him, as to put a bushel 
 of anything into a pint.' " * 
 
 * " Caspar Hauser, in a detailed account of his own experience in this respect 
 states, that upon his first liberation from confinement, whenever he looked through 
 the window upon external objects, such as the street, garden, etc., it appeared to
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 309 
 
 They require time to reconcile the different visual sensa- 
 tions which the same object presents according to its different 
 distances, and to reconcile all these with the muscular and 
 tactile sensations with which the object has already furnished 
 them. The most instructive case in this respect is that of 
 the lady operated on by Wardrop. Her blindness was more 
 complete than that of the others ; for not only was she born 
 with cataracts in each eye, but, when six months old, an un- 
 skilful surgeon had destroyed the right eye and closed up the 
 pupil of the left. She could not recognize any color, she was 
 able merely to distinguish a very light from a very dark room, 
 but without having the power to perceive even the situation 
 of the window, through which the light entered ; though in 
 sunshine or in bright moonlight she knew the direction from 
 whence the light emanated. When placed under Wardrop's 
 care she had reached her forty-sixth year. He opened the 
 iris, she was able to see, and " returned home in a carriage, 
 with her eye covered only with a loose piece of silk. The 
 first thing she noticed was a hackney- coach passing, when she 
 exclaimed, ' What is that large thing that has passed by us ? ' 
 In the course of the evening, she requested her brother to 
 show her his watch .... and looked at it for a considerable 
 time, holding it close to her eye. She was asked what she 
 saw; and she said there was a dark and a bright side." In 
 
 him as if there were a shutter quite close to his eye, and covered with confused 
 colors of all kinds, in which he could recognize or distinguish nothing singly. 
 He says farther, that he did not convince himself till after some time during his 
 walks out of doors, that what had at first appeared to him as a shutter of various 
 colors, as well as many other objects, were in reality very different things ; and 
 that at length the shutter disappeared, and he saw and recognized all things in 
 their just proportions." Franz, " On the eye," p. 34-6. Dr. Franz adds : Since 
 ideas are gained by reflection upon sensation, it is further necessary in all cases in 
 order that an accurate idea of objects may be formed from the sense of sight, that 
 the powers of the mind should be unimpaired and undisturbed in their exercise. 
 A proof of this is afforded in the instance related by Haslam (' Observations on 
 Madness and Melancholy,' Second edition, p. 192), of a boy who had no defect 
 of sight, but was weak in understanding, and who in his seventh year was unable 
 to estimate the distance of objects, especially as to height ; he would extend his 
 hand frequently to a nail on the ceiling, or towards the moon, to catch it. It is, 
 therefore, the judgment which corrects and makes clear this idea, or perception of 
 visible objects."
 
 310 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 fact, these two sensations of brightness and darkness alone 
 corresponded to her former sensations, since till then she 
 had never been able to do more than distinguish light and 
 darkness. She was seen hourly to observe first one point, 
 then another, then again others in the numbers of sensations 
 of color which besieged her. But she was bewildered by 
 them ; " I feel stupid," she said. She voluntarily remained 
 silent, not being able to make out the chaos of impressions 
 which were as yet destitute of meaning to her inexperienced 
 eye. A fortnight later, she still said, " I see a great deal if I 
 could only tell what I do see ; but surely I am very stupid." 
 Nevertheless, she learned by degrees the names of colors, and 
 was soon able to distinguish them ; but as to the perception 
 of figures, that is to say for the transcription into the new 
 visual atlas of the old tactile and muscular atlas, the appren- 
 ticeship was very long. On the seventh day she was exam- 
 ining the teacups and saucers, and was asked, " What are they 
 like ? " "I don't know," she replied ; " they look very queer 
 to me, but I can tell what they are in a minute when I touch 
 them." "She distinguished an orange on the chimney-piece 
 but could form no notion of what it was till she touched it." 
 On the eighteenth day the experiment was made " of giving 
 her a silver pencil-case and a large key to examine with her 
 hands ; she discriminated and knew each distinctly ; but 
 when they were placed on the table side by side, though she 
 distinguished each with her eye, yet she could not tell which 
 was the pencil-case, and which the key." On the twenty-fifth 
 day, being in a carriage in the Regent's Park, she inquired 
 continually as to the meanings of her visual sensations, such 
 as " ' What is that ? ' ' It is a soldier,' she was answered. 
 ' Who is that, that has passed us just now ? ' It was a person 
 on horseback. ' But what is that on the pavement, red ? ' It 
 was some ladies who wore red shawls." It was constantly 
 necessary to translate for her into the language of touch, 
 which she understood, the unknown language of the eye. 
 As, before the operation, she knew from what direction the 
 light proceeded, she was probably already capable of approx- 
 imately directing her head and eyes to the side at which the 
 illuminated objects appeared ; but even this art was entirely
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 311 
 
 rudimentary. On the eighteenth day, " she seemed to have 
 the greatest difficulty in finding out the distance of any ob- 
 ject ; for when an object was he.ld close to her eye, she would 
 search for it by stretching her hand far beyond its position, 
 while, on other occasions, she groped close to her own face 
 for a thing far removed from her . . . ." When at the end 
 of six weeks she left London, she had acquired a pretty ac- 
 curate knowledge of colors and their different shades and 
 names, and also of many objects, but " had not yet acquired 
 anything like an accurate knowledge of distance or of forms, 
 and up to this period she continued to be very much confused 
 with every object at which she looked. Neither was she able, 
 without considerable difficulty and numerous fruitless trials, 
 to direct her eye to an object ; so that when she attempted 
 to look at anything, she turned her head in various directions, 
 until her eye caught the object of which it was in search." 
 In fact the least movement of the head changes all our visual 
 sensations for other ones ; a precise movement is required, 
 neither too great, nor too small ; to attain a preconceived 
 visual sensation, we must direct our glance correctly. Just 
 as an infant does not distinguish or retain, till after many 
 trials, the precise nature and exact amount of the effort re- 
 quired to throw a stone ten paces and not nine or eleven ; so 
 was this lady unable to distinguish and fix in her memory, 
 until after many incessantly corrected attempts, the particular 
 nature, the degree of intensity, and the precise duration of 
 the muscular sensation which her neck must experience in 
 order for the inclination to right or left ; the raising or lower- 
 ing of her head, and so of her eye, to be three degrees and 
 not two, four, or five. 
 
 All these particulars result in one conclusion our pure 
 visual sensations are nothing more than signs. Experience 
 alone acquaints us with their meanings ; in other words, ex- 
 perience alone associates with each of them the image of the 
 tactile and muscular sensation corresponding to it. At the 
 present day, the analysis of physiologists and physicists has 
 noted, by a multitude of proofs and counter-proofs, the vari- 
 ous stages of this association.* The sensations which the re- 
 
 * Hclmholtz, " Physiologische Optik," 797.
 
 312 THE KNOWLEDGE OF BODIES. [BOOK II 
 
 tina procures us are those of different colors, and of different 
 degrees of light and shade ; and further, as it is a sheaf of dis- 
 tinct nervous fibres, each of its fibres, in accordance with the 
 general law of the nervous system, excites, when impressed, 
 a distinct sensation. In these three respects, and in these 
 three respects alone, can we distinguish a pure visual sensa- 
 tion from others similar in kind, and this is the first layer on 
 which will be established later on the whole fabric of our vis- 
 ual perceptions. In this state, which is that of the person 
 born blind immediately after the operation, the eye has the 
 sensation only of variously colored patches more or less clear 
 or obscure; and, in a whole patch, it can observe some dis- 
 tinct portion, but simply, as a partial patch.f Wardrop's pa- 
 tient, looking at a watch, on the evening of the operation, ob- 
 served the figure 12, the figure 6, and the hands, but simply 
 as patches upon a patch, without knowing what they were. 
 So again, on the third day, looking at her brother's face, she 
 distinguished in this round flesh-colored patch, a special patch 
 produced by the prominence of the nose, and guessed, in fact, 
 that it was the nose. Painters in color are well aware of this 
 
 s 
 
 state ; they revert to it ; their art consists in seeing their 
 model as a patch, the only element of which is the more or 
 less diversified, deadened, vivid, and mingled color. At this 
 stage, there is no idea of the distance or position of objects, 
 
 f With respect to this, it is curious to observe very young children. I have 
 lately been able to apply and verify the theory in the case of a little girl whom I 
 saw every day from her birth. It is certain to my mind that, during tne first two 
 months, the surrounding world was composed for her of sounds and patches of 
 color, which she did not know how to situate. At two months and a half, she evi- 
 dently recognized the direction of certain sounds ; for instance, hearing her grand- 
 mother's voice, she turned her head towards her. At three months she knew, in 
 some cases, how to direct her looks by turning her head and eyes towards the ob- 
 ject she wished to see, and among others, to my face. But she could not do this 
 with every object. Plainly, what she first distinguished, noted in her memory, and 
 recognized, were sounds and faces. In fact, among the hundreds of sounds and 
 colored forms which impressed her senses were the tones of five or six voices, and 
 the colored forms of five or six faces, and these, being the most frequently repeated, 
 intruded, by their frequency and identity, on the rest. At about three months old, 
 she commenced to feel about with her hands, to move her arms to reach objects, 
 consequently, to associate with the colored patches tactile and muscular impres- 
 sions of distance and form.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 3^ 
 
 except that an induction derived from touch places them in 
 contact with the eye. No doubt, at this stage, an object may 
 be recognized by the color, vividness, and characters of its 
 patch, as Wardrop's patient was able to distinguish the grass 
 from the water, but nothing is known as to its situation. The 
 second layer of the edifice is not constructed ; it is now nec- 
 essary to add, little by little, to pure retinal sensations, auxil- 
 iary and additional ones. 
 
 The sensations so added are those of the muscles of the 
 eye ; for the form and position of the eye are susceptible of 
 changes, and these changes are the effect of its muscular ap- 
 pendages. In the first place, we adjust the eye to the dis- 
 tance of the object, by disposing it in such a way that the lu- 
 minous image falls precisely on the retina, and not before or 
 behind it ; otherwise, the vision is not distinct ; to effect this, 
 we alter the curvature of the crystalline lens, probably by con- 
 tracting the ciliary muscle, and the muscular fibres of the iris. 
 Besides this, when we look at an object with both eyes, our 
 two eyes converge more or less, according as the object is at a 
 greater or less distance. Now this greater or less convergence 
 is produced by the greater or less contraction of the muscles 
 which move the eye. Consequently, according to the greater 
 or less distance of the object, we have a particular muscular 
 sensation of the eye. On the other hand, according as the ob- 
 ject is in one or the other direction, with reference to our 
 eye, one or other of the muscles which move the eye is more 
 or less contracted, in order to turn it upwards or downwards, 
 to the right or left ; in such a way that when the distance re- 
 mains the same, a distinct muscular sensation corresponds to 
 every change of direction. We learn to observe and engrave 
 on our memory these innumerable distinct muscular sensa- 
 tions of our eyes. At the same time, and by means of touch, 
 we associate some one of them with a certain movement of 
 our hand, another with the semi-extension of our forearm, 
 others with two, three, six, ten, twenty strides of our legs. 
 Henceforward, when a pure visual sensation follows some par- 
 ticular voluntary muscular sensation of the eye, this compound 
 calls up the idea of some particular movement of the hand, 
 the forearm, or the arm, of some particular number of steps, in
 
 314 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 short, of some portion of the tactile and muscular atlas which 
 the experience of our limbs has constructed within us, and 
 by which the person born blind estimates distance and deter- 
 mines positions. At the end of three weeks, the lady opera- 
 ted on by Wardrop was able to recognize a grass-plot by the 
 large and beautiful green patch it formed in her field of vis- 
 ion. But she had not yet distinguished and observed what 
 muscular sensation of her eye had resulted in the apparition 
 of this green patch, and above all, had not ascertained, from 
 the nature of the muscular sensation, the number and direc- 
 tion of the steps which would be required to lead her up to 
 the grass-plot ; so that, though she saw it, she did not know 
 where it was, and perhaps extended her foot to find out wheth- 
 er it was not close to her. To us who have noted the various 
 muscular sensations of our eyes, and have associated them to 
 the recollection of the movements of our limbs " the feeling 
 that we have when the eyes are parallel and vision distinct, is 
 associated with a great and prolonged effort of walking, in 
 
 other words, with a long distance The change 
 
 from an inclination of the eyes of 30 to an inclination of 10 
 is associated with a given sweep of the arm, carrying the hand 
 forward over eight inches and a half."* In this way, muscu- 
 lar sensations of the eye become in our cases signs, each of 
 which has power, when produced, to call up with it the image 
 of some particular muscular movement of the limbs, in other 
 words, the precise idea of a certain distance measured in a 
 certain direction. 
 
 To these auxiliaries add the rest I mean the muscular 
 sensations of the neck and body in turning, bending, and draw- 
 ing back, so as to enable the retina to receive a distinct lumi- 
 nous image ; these are so many complementary signs which, 
 in connection with the first, effect the determination of the 
 direction of the object by the association they have contracted 
 with the image of some special movement of the limbs carried 
 out in some particular direction. The reader now sees how 
 the eye is capable of perceiving the figure of a body. The 
 visible figure of a body is nothing more than a double series 
 
 * Bain, " Senses and Intellect," 2nd edition, 374.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 3! 5 
 
 of optical sensations, a retinal series and a muscular series, 
 both of which are parallel and continuous, and are experi- 
 enced whenever the eye follows the outline and runs over 
 the illuminated surface of a body. Experience associates to 
 this double series of sensations a series of images, that 
 is to say, images of the tactile and muscular sensations 
 which the hand would experience in following the outline, 
 and feeling the surface of the bodies. Other experiences 
 teach us that, according to the distance, this double opti- 
 cal series undergoes regular alteration, without the other se- 
 ries being altered ; and we express this by saying that the 
 same tangible object passes regularly, according to distance, 
 through an infinite series of visible appearances ; and it fol- 
 lows from this, that when we see it at a particular distance, 
 the row of its other visible appearances is ready to revive in 
 us, and to take up a position in the mental background. I 
 leave further explanation to treatises on optics and physiolo- 
 gy,* in which will be found the enumeration and explanation 
 of all optical judgments and errors. They are the subject- 
 matter of a whole science, but are all reduced to one princi- 
 ple. " By experience," says Helmholtz,f " we can evidently 
 learn what other sensations of the sight or other senses, an 
 object we see will excite in us, if we advance our eyes or body, 
 if we look at the object from different directions, if we feel it, 
 etc. The concept of all these possible sensations combined 
 in a whole is our representation of the body ; and, when it is 
 sustained by our actual sensations, it is what we term the per- 
 ception of the body It includes all the distinct possible 
 
 groups of sensations which the body when looked at, touched, 
 experimented on in various ways, can excite in us ; these are 
 its real effective contents ; it has no others, and these con- 
 tents may undoubtedly be acquired by experience. The only 
 physical activity required for this purpose is the constant 
 and reviving association of the two representations, which were 
 already connected together, an association which becomes 
 the more solid and more constrained in proportion to the 
 
 * See the admirable work of Helmholtz ; above all the third part, " Die Lehre 
 von den Gesichts-Wahrnehmungen." \ Ibid., p. 798.
 
 316 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 number of times the two representations have reappeared 
 together." 
 
 From this, we understand in what our visual atlas consists. 
 There is a square mahogany table three paces from me, to 
 the right. I turn my eyes, and have, through the retina, a 
 sensation of a certain somewhat glistening brown patch ; and 
 I have at the same time, by means of the accommodation of 
 the crystalline lens and the contraction of the muscles which 
 move the eye, a certain muscular sensation which, by an ac- 
 quired correspondence, calls up in me the image of three 
 paces, taken to the right. My eyes follow the outline of the 
 table, in other words, my retina experiences in succession a 
 continuous series of impressions in proportion as the lumin- 
 ous rays starting from the sides of the table successively im- 
 pinge on its yellow centre ; now, in the meantime, the accom- 
 modation and contraction of the muscles of the eye give me 
 a parallel and continuous series of muscular sensations, which, 
 by an acquired correspondence, call up in me the images of 
 the tactile and muscular sensations which my hand would 
 experience in passing over its side from corner to corner. 
 Let us remark the character of these re-excited images. If 
 my glance has been a rapid one, they are not express ; they 
 remain in the nascent state ; I am compelled to prolong my 
 glance to call them up precisely and completely, to imagine 
 the muscular sensations of my three steps, the muscular and 
 tactile sensations of my hand, passed along the edge of the 
 table. I only get at this by dwelling on it, by silently in- 
 quiring of myself what it is I mean by this distance and this 
 form. Even when dwelling on it, I commence by imagining 
 the first step I should take, the sensation which my hand 
 would receive from the first corner ; these two images serve 
 as type for the rest. In fact, my operation is the same as 
 when in a written sentence I read the word tree ; if I read it 
 rapidly, I simply understand it ; it does not call up express 
 images in my mind ; it is necessary to weigh it, to reflect, in 
 order to cause the image of a beech, an apple, or other tree 
 to appear ; even then, it will be vague and mutilated ; at the 
 most, I shall get a view of some lineaments of a colored form, 
 the obliterated sketch of a green dome or pyramid ; it will
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 317 
 
 only be by dwelling strongly on it for some time that I shall 
 cause images of trees to spring up sufficiently clear and 
 numerous to be equivalent to the generic word which sums 
 up and denotes them all. Thus our optical sensations are, 
 like our words, signs. Every retinal and muscular sensation 
 has, like every word, its group of associated images ; it rep- 
 resents this group ; it replaces and denotes it ; in other 
 words, it is always associated with it, and never otherwise 
 associated, so that in use and practice it is equivalent to it. 
 In fact, when the sensation arises, the group is at hand, ready 
 to revive. Give it a little time, and it will partially revive. 
 Give it enough time, and it will wholly revive. It forms part 
 of the train of the sensation ; but, as the operations are rapid, 
 it most usually remains in the background ; the sensation 
 alone occupies the stage. As the sensation is there for an 
 instant only, and the train requires time to pass in proces- 
 sion, the train remains behind the scenes. We know some- 
 thing of this world behind the scenes.* The reader had a 
 view of it when we pointed out the silent persistence of 
 images, their latent existence, their rudimentary state, the 
 obliteration they undergo, and the life they preserve, often 
 for whole years, until the indistinct vibration, which was per- 
 petuated in some only of the cells of the hemispheres, 
 receives from some unforeseen circumstance a universal as- 
 cendancy, and becomes suddenly propagated through the 
 majority of the chords of the cerebral instrument. 
 
 The better to comprehend their obliteration and the part 
 they still play, though in this latent state, let us consider 
 greater distances, and generally, the process by which d istances 
 are estimated. In a geographical map we look at the myria- 
 metre traced at the foot, and applying compasses to this 
 myriametre, we pass about the map, measuring in this man- 
 ner if Paris is farther from Bourges than from Tours or Dun- 
 kirk. At the outset of the operation we estimated the 
 myriametre in muscular sensations, and found it equivalent 
 to some walk we have been accustomed to take, to 12,000 
 paces, to two hours' walking. But, soon after, we forgot the 
 
 * See part i. book iv. chap i. pp. 178-80.
 
 318 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 muscular signification we attached to this expansion of the 
 compasses ; we left it behind us, in reserve ; all we kept in 
 mind was degree of expansion and its multiples ; we di- 
 rectly compared a series of expansions to a series of expan- 
 sions, a series of greater ones to a series of less. We follow 
 the same process in all our estimations of quantities, and the 
 spontaneous operations of our eye do but precede the artifi- 
 cial operations of our instruments. In the first stages of our 
 observation, as at the limit of our science, we prove a constant 
 relation between two quantities, just now between our more 
 or less numerous steps and the greater or less expansions of 
 the compasses, at present between the more or less long and 
 repeated muscular sensations of our limbs, and the muscular 
 sensations which we receive from the greater or less conver- 
 gence of our eyes, the greater or less flattening of the crystal- 
 line lens, the greater or less contraction of some one of the 
 muscles which move the eyes, the greater or less movement 
 of our body and head in some particular direction. The sec- 
 ond quantity increases or decreases with the first, according 
 to a fixed law. This being settled, we take a standard of the 
 second, just now a certain expansion of the compasses, for in- 
 stance the expansion which measures the myriametre, now a 
 certain muscular sensation of our optical apparatus, for in- 
 stance, the muscular sensation which the eye must experience 
 in order to have the retinal sensation of an object situated at 
 thirty centimetres distance. At this moment, too, the stand- 
 ard and its signification, that is to say the expansion of the 
 compasses and the recollection of our walk, that is to say 
 again, the muscular sensation of the eye and the image of the 
 muscular sensation of the arm carried thirty centimetres for- 
 ward, are together in our mind. But a moment afterwards 
 the standard alone remains ; the image or the recollection to 
 which it is equivalent becomes thin, and fades away ; we sim- 
 ply observe that a certain expansion is greater than another, 
 that a certain muscular sensation of the eye is stronger and 
 more prolonged than another; we no longer perceive the sig- 
 nified quantities but only the significant ones. This is enough ; 
 for, by means of the indicated association, the signified quan- 
 tities remain within call, and their proximity is as good as
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 
 
 their presence. At any moment we can recall them, can ob- 
 serve that a certain expansion of the compasses, that is to 
 say one of three times the extent of the first, would require 
 of us three times as many steps, or six hours' walking, that a 
 smaller muscular sensation of the eye would require a double 
 extension of our arm. We know how a map serves us on a 
 walking tour ; by applying to it compasses we foresee the 
 length of our walks, and the amount of muscular effort we 
 shall be compelled to expend. Our visual atlas is of the same 
 use ; by translating certain of its indications into the corre- 
 sponding indications of the tactile and muscular atlas, we 
 foresee the distance, the magnitude and duration of the mus- 
 cular effort by which our limbs will reach some particular ob- 
 ject. 
 
 VI. We see now how it is that a visual sensation, so short 
 as to appear instantaneous, can give us the idea of very di- 
 versified and very great extension. This arises from its being 
 equivalent to the very diversified and very long tactile and 
 muscular sensations by which we should perceive this exten- 
 sion. It sums them up, and so becomes their substitute, and 
 signifies them while replacing them. 
 
 But, even were we incapable of having this sensation, we 
 should still contrive to represent to ourselves in combination, 
 and as simultaneous, a great number of the parts of space. I 
 have questioned many blind persons as to this,* their answer 
 is unanimous, wholly precise and decided. No doubt the 
 perception of a new object requires more time in their cases 
 than in ours, since they are compelled to explore it in detail 
 by touch. But, having done so, they think of the object, 
 whatever it be, a sphere, a circle, or even a considerable space, 
 for instance, a street, all at once, and represent it to themselves 
 in mass. "All there is wanting to us," they say, "is what 
 you call the idea of color ; the object is to us just what an un- 
 shaded drawing or photograph is to you, speaking more pre- 
 cisely, a combination of lines. We conceive a whole group of 
 diverging or intercrossing lines simultaneously, and that is to 
 
 * At the Institut des Jeunes-Aveugles at Paris, thanks to the kindness of the 
 Professors and Director of the establishment.
 
 320 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 us figure." Above all, they expressly deny that in order to 
 imagine a line or a surface, they require to represent to them- 
 selves the successive sensations of their hand passed in some 
 particular direction. " That would be too long, and we have 
 no need whatever to think of our hand : it is but an instru- 
 ment of perception of which, after perception, we cease to 
 think." 
 
 In fact, if, at the origin of the idea of distance, we find a 
 longer or shorter series of muscular sensations of the arm or leg, 
 it is at the origin only. It matters little whether these sensa- 
 tions appertain to one limb or the other, whether they are 
 muscular or not ; this is but a detail and an accessory ; it is 
 obliterated, we cease to attend to it. We leave aside, as the 
 blind say, all the circumstances and intrinsic qualities of our 
 sensations ; we preserve only the essential part, and the essen- 
 tial part here, is that they form a series interposed between 
 the two points whose distance we are estimating. Taken 
 thus abstractedly, these sensations become, as it were, uncol- 
 ored and neutral ; they are any sensations whatever ; we con- 
 sider them not as to their quality but as to their quantity ; what 
 we observe in them is the greater or less duration of their series : 
 nothing more. Henceforward, we are able to imagine them 
 with great promptitude, and to compare series to series. Such 
 is the process employed by a person born blind ; he may, like 
 Saunderson, become a geometrician, may conceive longer or 
 shorter series, diverging according to such and such an angle ; 
 these are lines, and, by a combination of such lines, he con- 
 ceives geometrical bodies. For our own parts, we avail our- 
 selves of this process when we define lines by the motion of 
 a point, the surface by the motion of a line, the solid by the 
 motion of a surface, and when we estimate a line, a surface, 
 or a solid by the greater or less prolongation of the muscular 
 operation, which engenders its perception. Now we can im- 
 agine these movements with extreme rapidity ; we may, then, 
 thus, by these means alone conceive many lines, therefore a 
 surface, and even an entire solid, almost in an instant. 
 
 But, fortunately, we have a second aid, the visual atlas, 
 which is added in our cases to the tactile and muscular atlas. 
 Thanks to it, we have at our disposal new series which may
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 321 
 
 be compared together, and whose elements succeed in us with 
 prodigious velocity. These are the little muscular sensations 
 of the eye, which are extremely short, and able, therefore, 
 to denote, in an imperceptible portion of time, very great 
 distances, and positions as numerous as various. They take 
 the place of the muscular and tactile images corresponding to 
 them, and, as they pass in a moment, it seems as if the much 
 longer series of tactile and muscular sensations has also taken 
 effect in a moment. Their muscular and tactile signification 
 springs up with them, and we imagine that we perceive at once 
 a number of distant and co-existing points. The reader has 
 already met with many operations of this kind ; it is what 
 happens with all abbreviatory substitutes. The muscular 
 sensations of the eye serve us in sight as words do in abstract 
 reasoning.* When I contemplate the different views of an 
 extensive landscape, these sensations alone are in my mind, 
 just as, when I read a chapter on political economy or moral 
 philosophy, there are words alone in my mind, and yet, in the 
 first case, I believe that I directly perceive magnitudes and 
 distances, as, in the second case, I believe that I directly per- 
 ceive pure qualities and general relations. To employ the 
 expressions of Mr. Herbert Spencer, these little simultaneous 
 or nearly simultaneous muscular sensations are to us " symbols 
 of other tactile and muscular sensations, which were slowly 
 successive. This symbolic relation, being far briefer, is habit- 
 ually thought of in place of that it symbolizes : and by the 
 continued use of such symbols and the union of them with 
 more complex ones, are generated our ideas of visible exten- 
 sion ideas which, like those of the algebraist working out an 
 equation are wholly unlike the ideas symbolized ; and which 
 yet, like his, occupy the mind to the entire exclusion of the 
 ideas symbolized. "f Hence it follows that, in our present 
 state, during the working of the optical substitutes, the image 
 of the long muscular and tactile sensations they replace must 
 be absent. Consequently, we do not now find it within us, 
 even if we look for it ; our perception of visible extension will 
 no longer comprise any of the muscular and tactile sensations 
 
 * See part i. book i. chap. ii. 
 f " Principles of Psychology," first edition, p. 224. 
 
 ai
 
 322 
 
 THE KNOWLEDGE OF BODIES. \EooK II. 
 
 of the limbs and hand. Such is, in fact, the conception we 
 now have of visible extension ; in this state, we no longer find 
 any thing in it to recall its origin. In truth, what is now with- 
 in us is not the image of the original successive sensations of 
 the hand and limbs, but their optical sign. The visual atlas, 
 constructed by means of the muscular and tactile atlas, is 
 wholly different, from it ; it is not a copy, but a reproduction on 
 another scale, with other notations, far more convenient for 
 use, comprising in one chart what is dispersed in the other atlas 
 over twenty several maps, and presenting, at one glance, a 
 group so vast that, in the other atlas, we should be obliged to 
 arrive at it, discursively and slowly, over twenty different leaves. 
 This visual atlas has such great advantages over the other 
 that we constantly, and almost exclusively, employ it. In 
 the first place it is, as we have seen, extremely abbreviatory 
 for all distances of any magnitude. In an instant, by a sim- 
 ple diminution of the convergence of the eyes, we pronounce 
 that one object is twenty paces further from us than another. 
 In an instant, by a simple continuous movement of the eye, 
 we pronounce that a particular surface is square or triangular. 
 This frees us from the necessity of imagining in detail the 
 long muscular sensation of twenty steps, the long tactile mus- 
 cular sensation of the hand passed over the whole outline of 
 the surface. Thanks to this rapidity of optical operations, we 
 can seize in a very short time, and by. a perception which ap- 
 pears instantaneous, a whole entire object, a chair, a table, a 
 person, and more, if the object be distant, a whole meadow, 
 a group of trees, a building, the facade of a street. You are 
 placed at a window, you open your eyes, and at once, by 
 means of a very small movement of the eyes and an imper- 
 ceptible movement of the head, the whole landscape appears 
 to you, with its different levels, meadows, woods, sky, clouds, 
 with their innumerable details of form, relief, and shade. Your 
 eye is at the converging point of the luminous rays which 
 start from the objects that is to say at the angle of the com- 
 passes formed by two divergent rays, as they reach the retina. 
 Now, a very trifling distance, measured near the angle of the 
 compasses, corresponds to an immense, and sometimes enor- 
 mous distance measured at their points. This is how we es-
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 323 
 
 timate, at a glance, hundreds of metres, and sometimes of 
 leagues ; it seems to us at the time that all the sensations 
 we had during this glance are simultaneous, and in this man- 
 ner, all the external objects they reveal to us are perceived, 
 so to speak, together ; which renders far easier for us the task 
 of recalling and comparing them; in short, of practising on 
 them the various ulterior operations of which we have need. 
 
 On the other hand, very small distances and very minute 
 objects are also within the province of sight. In this respect 
 the skin, compared with the retina, is a coarse instr-ument, 
 even at the places in which its sensibility is most delicate. 
 At the dorsal vertebrae, at the middle of the arm, of the thigh, 
 of the neck, when two adjacent points are touched, we do 
 not distinguish them as being two, unless they are from six- 
 teen to twenty-four lines apart ; at the palmar surface of the 
 last joints of the fingers, it is sufficient for the points to be 
 seven-tenths of a line apart ; at the point of the tongue, where 
 the power of discrimination is most perfect, a little less than 
 half a line is a sufficient distance.* On the contrary, accord- 
 ing to Weber and Volkmann, on the yellow spot, which is 
 the most sensitive point of the retina, two brilliant specks 
 may be distinguished when separated only by an interval of 
 from .002 to .001 of a line. In this way, the retina is a 
 thousand or two thousand times as sensitive as the most 
 sensitive organ of touch. Add to this advantage the indica- 
 tions afforded by color. A level surface for instance, a printed 
 or written page, affords one uniform sensation only to touch, 
 and the same surface affords to the sight as many distinct 
 sensations as there are black letters written or printed on the 
 white ground. So the tactile and muscular atlas does not 
 comprise images corresponding to very minute objects, to the 
 form and proximity of two threads in a piece of fine muslin, 
 nor images corresponding to the diversity of colored surfaces, 
 to the presence, form, and movement of the various objects 
 placed beyond the reach of our hand, like the clouds, the 
 sky, and the stars ; primitively, at least, these images were 
 all absent from the tactile and muscular atlas ; if they have 
 
 *See the complete Table, Mueller, "Physiology" (tr. Baly), i. 701.
 
 324 THE KNOWLEDGE OF BODIES. [Boon II 
 
 found an entrance, it has been but subsequently and approx- 
 imately, by means of the reciprocal translation which we are 
 able to establish between the two atlases. 
 
 We need not be surprised, then, at the enormous part 
 played by the visual atlas in ordinary life. For our parts, to 
 recollect, to imagine, to think, is to see internally ; and to call 
 up the more or less enfeebled and transformed visual image 
 of things. So, too, the word image is borrowed from the 
 history of vision ; strictly, it only denotes the cerebral revival of 
 the optical sensation ; it is by extension that we have applied 
 the same name to the cerebral revival of muscular and tactile 
 sensations, of sensations of sound, taste, and smell. By the 
 same encroachment the visual atlas, being infinitely more 
 extended and much more readily dealt with than the other, 
 becomes our general resort ; all our sensations are transcribed 
 into it, and find a place in it, the muscular and tactile ones 
 with the rest. In fact, I have internally the visual represen- 
 tation of my body, and even of the parts, like the back, which 
 I have not seen ; and when I contract a muscle, or undergo 
 a contact, I localize the contraction and contact, not only by 
 imagining the longer or shorter sensation, which would con- 
 duct my hand as far as the spot of contraction and contact, 
 but, further, and above all, by imagining the visual form and 
 color of the part affected. " It is on the right side, at the 
 crown of the head, on the knee, between the bones of the 
 left elbow." When we mentally pronounce a judgment like 
 this, we mentally see the colored form of the parts. This 
 extends so far that, usually, in order to represent to ourselves 
 the movement of the arm which would be required to meas- 
 ure a distance, we make use, not of muscular images, but of 
 visual images, and represent to ourselves, not the prolonged 
 contraction of our arm, but the colored form of our arm 
 passed through the air from one visible point to another. 
 And so, to estimate the distance of a sound, AVC represent to 
 ourselves by visual images the space which surrounds us, and 
 situate the sonorous trembling at a particular height, in a 
 particular direction, at a particular point of distance or prox- 
 imity, in the huge field surrounding our body and traversed 
 by the glance of the external or the internal eye.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 325 
 
 As to sensations of taste and smell, the two atlases come 
 at once into play, in order to situate them ; we have the vis- 
 ual representation, as well as the tactile and muscular repre- 
 sentation of our nose and mouth. In fact, as to the inside of 
 the mouth, it is the second representation which is of most 
 service, since the tongue plays the part of the hand ; for in- 
 stance, we discern and imagine by tactile and muscular sen- 
 sations only the movements which we must make to emit the 
 various sounds and articulations of language. Here, sight 
 and visual sensations do not intervene ; it is later on, by the 
 aid of physiology, that our eye takes account of the tongue, 
 and other appendages which modify the sound proceeding 
 from our larynx,* it is then only that we can visually imagine 
 the pronunciation of a guttural or dental. And so, too, the 
 tactile and muscular atlas is solely, or almost solely, employed 
 to note the short movements of the trunk on its base, and 
 sometimes all the movements of walking ; for instance, when 
 we mount, in the dark, a staircase with which we are not ac- 
 quainted, all that we imagine is the regular recurrence of the 
 same tactile and muscular sensations ; the visual atlas of the 
 staircase is wholly wanting, and the visual atlas of our legs 
 and body is almost absent. These are remnants or revivals 
 of its primitive predominance ; in such cases, we situate our 
 sensations somewhat in the fashion of persons born blind ; but 
 here we have fragments only. 
 
 In fact, not only is the visual atlas almost entirely substi- 
 tuted for its rival, but, further than this, it has hindered its 
 rival from acquiring all the perfection of which it is capable. 
 Evidently, at present, as to muscular and tactile sensations, 
 we have rough discrimination only ; we can hardly distin- 
 guish their shades of difference, for want of being compelled 
 to do so. Platner observed that the blind man, whose case 
 he described, was far more skilful than we are in this respect, 
 and this is true of all blind persons ; with some of them the 
 perfection of the sense of touch surpasses all imagination. 
 " Saunderson, the blind mathematician," says Abercrombie,f 
 
 * This accounts for M. Jourdain's astonishment when he learned that, to say 
 U, it was requisite to make a face, 
 f "Inquiry," etc. p. 51.
 
 326 THE KNOWLEDGE OF BODIES. [BOOK II 
 
 " could distinguish, by his hand, in a series of Roman medals, 
 the true from the counterfeit." " Mention is made," says 
 Bayle,f " of a blind organist who was very skilful in his pro- 
 fession, and who could readily distinguish all kinds of money 
 and colors. He even played at cards, and was very fortunate, 
 especially when it was his turn to deal, since he could recog- 
 nise by touch the cards he gave each player.:}: Aldrovandus 
 says that a certain Jean Ganibasius, of Volterra, an able sculp- 
 tor, having lost his sight at the age of twenty, determined ten 
 years after to attempt what he could in the way of his pro- 
 fession. He felt over very carefully a marble statue of Cosmo 
 I., Grand Duke of Tuscany, and modelled from it a plaster 
 one, which resembled Cosmo so much as to astonish every- 
 body. The Grand Duke Ferdinand sent him to Rome, where 
 he made a plaster statue resembling perfectly Urban VIII." 
 Joseph Kleinhaus, who died at Nauders (Tyrol) on the 
 loth July, 1853, had become blind with small-pox at five 
 years old. He at first amused himself by carving wood to 
 pass the time, then obtained lessons and models from Prugg ; 
 at twelve years old he carved a crucifix the size of life, and 
 became a pupil of the sculptor Nissl, improved greatly and 
 became celebrated. He is computed to have carved four hun- 
 dred crucifixes, and a bust of the Emperor Francis Joseph. 
 It is enough to see blind men read with their fingers books 
 printed in relief almost as rapidly as we read books printed in 
 black and white, to comprehend all the power of discrimina- 
 tion which our touch might have, but has not, acquired.* 
 
 f Bayle, cited by Gamier, " Traite des Facultes de 1'ame," i. 354. 
 
 \ If this be true, it must be owing to the painting on cards having differences 
 of grain and relief corresponding to the different colors. 
 
 Schopenhauer, " Les quatre racines du principe du raison suffisante," p. 61. 
 
 * " An analogous fact is observed in the habit acquired by the deaf and dumb, 
 of understanding what is said to them by watching the motion of the lips of the 
 speaker." Abercrombie, " Inquiry," etc. 53. 
 
 I can myself mention a young man who became deaf when about four years old, 
 and who, having very good eyesight, saia a conversation at a distance, which was 
 inconvenient enough for persons who were whispering privately in a corner at the 
 other end of the room. He could thus understand German and French, by the 
 movement of the lips. Only it was necessary that the conversation should not con- 
 tain many proper names which he was not acquainted with ; for the visible .move- 
 ment of the lips showed him the consonants, and not the vowels.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 327 
 
 Thus, in our cases, the tactile and muscular atlas has re- 
 mained in a rudimentary state. This is why when we at pres- 
 ent situate one of our sensations of touch, of sound, of smell, 
 of taste, it is almost always through the visual atlas .alone, or 
 with its supplementary concurrence ; in other words, the im- 
 age of an optical sensation is now incorporated with sensations 
 which do not reach us by the eyes, and it is this agglutination 
 which situates them in the places in which they appear to us. 
 VII. Here, then, are all our sensations situated, that is to 
 say provided with an apparent position and seat, all, primi- 
 tively, by the adjunction of a series of muscular images, de- 
 termining the position, and, by the adjunction of a series of 
 tactile images characterizing the seat, almost all, finally, by 
 the adjunction of visual images, which have become equiva- 
 lents of this series and signs of this group. We are now able 
 to explain our present conception of extension. Suppose a 
 great number of these localized sensations to be simultane- 
 ously produced, and the points to which we refer them to 
 
 The hearing and other senses are capable of acquiring an equal delicacy. 
 " Dr. Rush relates of two blind young men, brothers, of the city of Philadelphia, 
 that they knew when they approached a post in walking across a street, by a pecu- 
 liar sound which the ground under their feet emitted in the neighborhood of the 
 post ; and that they could tell the names of a number of tame pigeons, with which 
 they amused themselves in a little garden, by only hearing them fly over their 
 heads." Abercrombie, ibid. 
 
 When we add to these facts the cases of hypereesthesia so common in somnam- 
 bulism and hypnotism, we see that it is impossible to put a limit to the innate or 
 acquired acuteness of our senses. As to this, see Braid, " Neurhypnology," p. 62. 
 " A patient who could not hear the tick of a watch beyond three feet when avrake, 
 could do so when hypnotized at the distance of thirty-five feet, and walk to it in a 
 direct line, without difficulty or hesitation .... Some will feel a breath of air 
 from the lips, or the blast from a pair of bellows, at the distance of fifty or even 
 ninety feet, and bend from it, and, by making a back current, as by waving the 
 hand or a fan, will move in the opposite direction." These experiments have been 
 repeated and varied by Dr. Azam of Bordeaux, " and the hearing," he says, " at- 
 tains such acuteness that a conversation may be heard on the floor below. The 
 ticking of a watch is heard at twenty five feet distance." So with the smell, taste, sen- 
 sations of heat, and the rest. " I have seen a person write correctly with a book 
 placed between him and the paper ; I have seen a fine needle threaded in the 
 same position ; have seen a person walk about a room with his eyes entirely closed 
 and bandaged, and all this without any other real guide than the resistance of the 
 air, and the perfect precision of the movements guided by the muscular sensations 
 in their hypersesthetic state." " Annalcs Medico-psychologiques," 36 serie, vi. 434.
 
 328 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 seem to us at once distant and continuous ; then, the whole 
 sensation, composed of partial, coexistent, distinct, and con- 
 tinuous sensations, that is to say of such that between the 
 position of one and that of another, we could not imagine any 
 intermediate, will appear to us extended. Let the reader be 
 good enough to observe his own case ; he will see that this is 
 so with the sensations of heat and cold, which seem to us to 
 occupy a whole limb, with the sensation of contact and pres- 
 sure which we experience in laying our hand flat on a table, 
 with the sensation of color which we experience when we 
 keep the eye steadily fixed on a green leaf placed at six feet 
 distance. In all these cases, the sensation seems extended. 
 This arises from its consisting in a number of simultaneous 
 sensations, which the education of the touch causes to appear 
 as situated in distinct and continuous points. Here there is 
 a double error, first, because, as we have seen, sensations are 
 situated in the sensory centres, and not in the nervous per- 
 ipheries, next, because, as physiologists show, the nervous 
 axes or cylinders, whose disturbance excites our sensations, 
 form, at their terminations, discontinuous lines and surfaces. 
 The extension of our sensation is thus, in two senses, an illu- 
 sion. 
 
 From this illusion there springs another. With reference 
 to sensations localized in points of our body, we conceive and 
 affirm the existence of objects situated beyond our body, that 
 is to say external, and we determine their situation by the 
 situation of the sensation which reveals them to us. For in- 
 stance, a sensation of smell reaches me, and I at once con- 
 ceive and affirm a rose to be situated in the neighborhood of 
 my nose. I experience a sensation of heat which I refer to 
 my left leg ; and I at once conceive and affirm some heated 
 object, a current of hot air, a stove, a fire-place, as situated 
 near my left leg. The more determinate and precise the 
 locality of my sensation, the more precisely do I determine 
 the locality of the object. This is what happens with sen- 
 sations of contact, and especially at the surface of the skin, 
 and more particularly at the lips, the point of the tongue, the 
 hand, the fingers, the tips of the fingers ;* at these parts 
 
 * See Weber's Measurements, Mueller, " Physiology " (tr. Baly), i. 701.
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 
 
 329 
 
 the power of discrimination is very delicate, and two points 
 separated by a line, or even half a line, give two distinct 
 sensations. By means of such sensations, we are able 
 to situate an object very exactly ; their position is very 
 precise ; consequently, the position of the object is no 
 less precise. This position is still more precise in the case 
 of sensations of color ; consequently, in this case, the posi- 
 tion of the object is still more precise. If, now, we con- 
 sider a sharply circumscribed portion of these very sensi- 
 tive surfaces, and admit that, when all the nervous points 
 capable of affording us a distinct sensation are disturbed at 
 once, we may have a sensation apparently extended and con- 
 tinuous ; we shall conceive and affirm the external object as 
 extended and continuous. This is at present our usual pro- 
 ceeding. This is why, by means of a total sensation, com- 
 posed of partial and simultaneous sensations, we perceive as 
 extended and continuous the ground on which our foot is 
 resting, the portion of the table on which our hand is ex- 
 tended, the distant object which our sensation of color de- 
 notes. We start from the extension and continuity of our 
 sensation, to ascribe to the object a similar extension and 
 continuity ; now, the continuity and extension of the sensa- 
 tion being apparent only, that of the object can only be ap- 
 parent. Consequently, the extension and continuity of 
 bodies are illusions only ; and, in fact, physicists arrive at 
 conceiving atoms, if they exist, as separated by enormous 
 intervals, in such a way that in a surface which appears to us 
 continuous, the vacant part is far more extensive than the 
 occupied part ; going deeper still, they define bodies as a 
 system of mathematical points, with relation to which effects 
 increase or decrease according to distance. At all events, 
 there is nothing to prove that bodies are really extended and 
 continuous ; in this respect, our assertion is entirely gratui- 
 tous. Thus, the extension which we ascribe to bodies is, in 
 fact, an apparent property of our sensation, a property which, 
 by a natural illusion, we transfer to bodies. But this trans- 
 fer is not, as Kant teaches, the effect of the innate and inex- 
 plicable structure of the mind ; it is the effect of an acquired 
 disposition, instituted in us by experience, and we have been
 
 330 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 able successively to show the various steps of this acquisi- 
 tion. 
 
 Other consequences follow. By the position and exten- 
 sion we attribute to our sensations, our being itself seems to 
 us situated, extended, circumscribed in a precinct. This pre- 
 cinct is attached to the personality, and henceforward, the 
 idea I have of myself is inseparable from the idea I have of 
 my body. In fact, this body is the only thing that accom- 
 panies me everywhere. It is the only thing which answers 
 to my touch by a sensation of contact. It is the only thing 
 which my will sets directly into motion. It is the only thing 
 in which I place the sensations I attribute to myself. In all 
 these respects it appears to me so tied up and confounded with 
 myself, that, when I refer a sensation to any point whatever 
 of the nervous surface, my being and my personality seem to 
 me for the moment situated at the spot in question. Such 
 is the present state. Hence it follows that when I now touch 
 a table, the object touched must appear to me not only as 
 other than myself, but, further, as without me and without 
 my sentient surface. It is thus opposed, not only to myself, 
 but also to the enclosed space in which I situate my person- 
 ality, and in this way, for the first time, it is really external. 
 
 In fact, it is this character which strikes us when we now 
 perceive a body. We conceive it as a thing beyond us ; to 
 this first characteristic, the others attach themselves. On 
 moving my hand about in the dark, it meets with an unknown 
 obstacle in a table ; upon this sensation, I conceive and affirm 
 beyond my hand a thing beyond it, which excites in me a con- 
 tinuous and extended sensation of resistance, and which, be- 
 ing capable, as I suppose, of exciting it again, presently and 
 still later on, in others as well as in myself, thus possesses 
 the permanent and general property of being resisting and 
 extended. At the same time, the shades of my sensation 
 and the accompanying sensations of uniform contact, cold 
 and sound, add to my conception the idea of a conical form, 
 of a metallic and sonorous substance, that is, of a bell. Thus 
 determined and qualified by the group of sensations it ex- 
 cites, this thing beyond me is opposed to me as a thing without, 
 to a thing within. The separation is still more readily effected
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 33! 
 
 when the perception comes through the eyes ; and ob/erve 
 that, at present, this is the most usual process. We have 
 shown how, in sight, the sensation of the retina finds itself 
 projected in appearance beyond our sentient surface, to be- 
 come incorporated with the object which excites it, in such a 
 way that color, which is an event of our being, seems to us 
 a quality of the object. When I perceive this silver bell at 
 three paces from me, the white shining patch in its centre, 
 which appears to me to be three paces off, is a sensation of 
 the retina transported from its seat by the education of the 
 eye. In this case, our sensation itself appears to us as a thing 
 beyond us ; consequently the object to which we attribute 
 it, and which, under the name of color, it seems to clothe, is 
 opposed to our self and its precinct as a thing external and 
 more or less distant. Sensations apparently projected be- 
 yond the nervous surface in which we situate our personality, 
 lodged in a determinate point of this outer region, detached 
 from us by this projection, constituted apart as events foreign 
 to us, erected into permanent qualities by the continuity and 
 uniformity of their repetition, erected into qualities of a solid 
 body by the presumed possibility of a sensation of contact 
 and resistance at the spot in which we situate them : such 
 are the visual, and really internal, phantoms which, when we 
 open our eyes, seem to us external objects, and we now com- 
 prehend without difficulty how it is that, being compounds 
 of the kind, they appear to us, not only as other than our- 
 selves, but as situated without us. 
 
 VIII. Here we have the appearances, and it is time to 
 inquire if there be any thing real corresponding to so many 
 illusions. We have found that the objects we call bodies are 
 but internal phantoms, that is to say fragments of the Ego, 
 detached from it in appearance and opposed to it, though 
 fundamentally they are the Ego under another aspect ; that, 
 strictly speaking, this sky, these stars, these trees, all this 
 sensible universe which each of us perceives, is the work of 
 each of us, or rather his emanation, or rather his creation, an 
 involuntary creation, effected by him spontaneously without 
 his consciousness of it, and extended to infinity around him 
 like the shade of a little body whose outline goes on increas-
 
 332 THE KNOWLEDGE OF BODIES, [BOOK II. 
 
 ing in proportion as it becomes distant, and ends by covering 
 the whole horizon with its immensity. We have then found 
 that no one of our sensations is situated in that part of the 
 body in which we place it, that many of them, though belong- 
 ing to us, appear as foreign to us, that among these some 
 appear as permanent qualities of a being other than ourselves, 
 while they are in fact transient moments of our being. Thus, 
 illusion shows itself in all our judgments, whether they refer 
 to the external or the internal world, and we are no longer as- 
 tonished at finding the Buddhist Philosopher reduce the Real to 
 momentary events of his Ego. But analysis, after destroy- 
 ing, is able to reconstruct, and in observing the manner in 
 which our illusions are formed, we have already discovered 
 how they lead us on to truths. 
 
 Let us first take the sensations which we still attribute 
 to ourselves, but which we project from their cerebral seat to 
 situate them in the organs, and in general, at some point of 
 our nervous periphery namely, those of taste, smell, con- 
 tact, pressure, muscular contraction, pain, heat, and cold. 
 No doubt, these sensations are not at the spot in which they 
 seem to us situated ; but there is usually found at this spot 
 the commencement of the nervous disturbance which excites 
 them. For, as a general rule, each variation in this distur- 
 bance and in its real position is represented by a proportion- 
 ate variation in the sensation and its apparent position, so 
 that, as a general rule, our false judgment results in the 
 same conclusion as a true judgment. It serves us as well ; 
 it suggests to us the same provisions. If the nervous dis- 
 turbance which excites the sensation of pressure increases 
 in strength, the sensation of pressure increases in strength. 
 If the nervous disturbance which excites pain actually changes 
 place, the pain seems to change place. The differences of posi- 
 tion which our ordinary judgment incorrectly supposes to ex- 
 ist between two sensations, are precisely the differences of posi- 
 tion which physiological experiment correctly establishes be- 
 tween the starting points of the two corresponding nervous dis- 
 turbances. Thus our mind hits the mark, though its aim is 
 bad, and what we erroneously allege of our sensations applies 
 with an almost absolute and almost constant exactitude to
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 333 
 
 the nervous disturbance connected with them. Except in 
 those rare cases in which the nervous trunks and centres 
 enter spontaneously into action, this application is always 
 correct. This is from its being the effect, not of a coinci- 
 dence, but of a harmony. In fact, the sensation is almost 
 always connected with the disturbance of the extremity of 
 the nerve ; and this almost constant connection was necessary 
 to establish in me the constant association of images by 
 which I now situate the sensation in the neighborhood of the 
 nervous extremity. Consequently if, on the one hand, this 
 connection invariably leads me astray by making me invariably 
 situate my sensation in a wrong spot, on the other hand it 
 almost invariably retrieves the error, by almost invariably 
 determining a disturbance of the nervous extremity. It has 
 two consequences, the one unfailing and indirect, my mental 
 illusion, the other direct and almost unfailing, the disturbance 
 of the extremity of the nerve ; they are two streams starting 
 from the same source ; that is why they correspond. If to 
 the mental illusion there almost invariably corresponds the 
 disturbance of the nervous extremity, it is from their both 
 arising by virtue of the same law. 
 
 The same observation applies to sensations which we 
 project beyond our sensible precinct, and which we consider 
 to be events foreign to us, as for instance sounds, or qualities 
 of objects foreign to us, as for instance colors. No doubt 
 it is erroneously that a particular sound, which is a sensation 
 of my acoustic centres, appears to me to float in the air, at 
 twenty paces to the right ; but to its regular or irregular 
 sound corresponds, element for element, a vibration of the 
 air which is propagated from this point, at this height, this 
 distance, and in this direction. No doubt, again, it is erro- 
 neously that the white and blue rays, which are a sensation 
 of my optic centres, seem to me extended on the paper with 
 which my room is hung ; but to these rays of color corres- 
 pond, element for element, differences of structure in the 
 surface of the paper, and consequently differences of aptitude 
 to absorb or reflect the different luminous rays. Except in 
 the rare cases in which the ear and eye have subjective sen- 
 sations, the correspondence is perfect. So, here again, our
 
 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 judgment, invariably false in itself, is almost invariably true 
 by correspondence and coincidence. What we erroneously 
 affirm of our sensations is found true of something else ; the 
 variations and differences of the object coincide with the 
 variations and differences of our sensations. The fact is, that 
 our sensations are adjusted to things, and the internal order 
 to the external. Here, as before, the illusion of the sense 
 proceeds from its education, and its education frdm the laws 
 which connect the origin of a particular sensation to the 
 almost constant presence of a particular external condition ; 
 so that, at present, when the illusion is produced, the external 
 condition is almost invariably present. The law which has 
 resulted in exciting the illusion within us usually occasions 
 the condition without us. Admirable mechanism, which de- 
 ceives to instruct us, and leads us through error to truth. 
 
 The disturbance of the extremity of a little whitish fibre, 
 the vibration of the particles of a gas, the special structure of 
 an illuminated surface these are the real equivalents met 
 with under the illusion which displaces and disfigures our 
 sensations. But these equivalents themselves are bodies con- 
 sidered in the aspect of a movement they undergo, or of a 
 quality they possess. There remains then for us to distin- 
 guish the sense and value of a deeper illusion that which 
 constitutes external perception, and by which we affirm the 
 existence of bodies. Is there anything real corresponding to 
 this phantom which sensation excites in us, and which we 
 term a body ? We have said that external perception is an ac- 
 curate hallucination. In what does it differ from hallucination 
 strictly so called, which is deceptive ? Analysis has already 
 replied. To this internal and transient phantom which ap- 
 peared as a permanent and independent thing there usually 
 corresponds, characteristic for characteristic, a permanent and 
 independent Possibility and Necessity, the possibility of cer- 
 tain sensations under certain conditions, the necessity of the 
 same sensations under the same conditions with the addition 
 of a complementary one. What I am legitimately and truly 
 entitled to assert when I touch this ivory ball, is a group of 
 relations between certain conditions and certain sensations ; 
 by virtue of these relations, ever}' sentient being, who at
 
 CHAK II.] THE EDUCATION OF THE SENSES. 335 
 
 any moment of time shall place himself under the conditions 
 in which I am, will have the sensation I have, and the other 
 sensations I imagine. The law is a general one, independent 
 of my presence, of my absence, of my existence. Its perma- 
 nence causes me to imagine a metaphysical entity substance. 
 Its efficacy causes me to imagine a metaphysical entity force. 
 These are convenient symbols, but we must retain them in 
 the state of symbols. Taken in this sense, we may say that 
 to our phantom corresponds a substance, independent of us, 
 permanent, possessed of effective force, capable of exciting 
 in every sentient being a certain group of sensations, more 
 generally still, capable of exciting and undergoing an event 
 which we have recognized as the equivalent of our most 
 important sensations, that is to say motion, or change of 
 place. 
 
 But while availing ourselves of these phrases, we carefully 
 preserve the recollection of their inner meaning. We remind 
 ourselves that our external perception, reduced to what truth 
 it contains, is but a general assertion, the enunciation of a law, 
 a kind of prediction, valid for the past as for the future, the 
 prediction of certain events, sensations, or equivalents of sen- 
 sations, as possible under certain conditions, as necessary 
 under the same conditions, with the addition of a complemen- 
 tary one. We announce that every sentient being, who shall 
 touch or shall have touched the ball, will have or will have 
 had the group of muscular, tactile, visual sensations which we 
 ourselves had ; that 'everybody which shall come or shall have 
 come into collision with the ball, will lose or will have lost a 
 portion of its motion. There is hallucination proper, when 
 the thing announced is not accomplished, when the white 
 spherical form, which appears situated three paces from me, 
 does not excite in me or in others the muscular and tactile 
 sensations on which I reckoned, when a body which passes 
 through the spot at which it appears to me situated, does not, 
 in spite of my expectation, undergo any diminution of its mo- 
 tion. But this case is very rare, and the agreement between 
 the preliminary announcement and the subsequent effect is 
 almost constant. This means that there is, in fact, an almost 
 constant connection between the visual sensation of this
 
 336 THE KNOWLEDGE OF BODIES. [BOOK II. 
 
 whitish spherical body on the one hand, and a certain group 
 of muscular and tactile sensations on the other ; the first is 
 the indication of the second ; when the sensation is given, 
 the group is almost invariably possible ; when the first is 
 given, in almost every case, if there be added the comple- 
 mentary condition the transport of the hand to the proper 
 place the second becomes necessary. Now my constant 
 prediction is in my case the fruit of this almost constant con- 
 nection. Consequently, the infallible springing up of the pre- 
 diction supposes the almost infallible presence of the group, 
 and the course of events, which, by its regularity, has created 
 my attempt, finds, in this very regularity, cause to justify -it. 
 All this mechanism is admirable, and the reader now sees 
 the length of the elaboration, the perfection of the adjust- 
 ment, which permit us to form, effectually and successfully, 
 an act so usual, so short, so easy, as external perception. 
 The operation resembles digestion or walking; apparently, 
 there is nothing more simple ; in reality, there is nothing more 
 complex. There is, in front of me, three paces off, a book 
 bound in brown leather, and my eyes are open. A certain 
 sensation of brown color rises in my optic centres ; in other, 
 centres rise muscular sensations excited by the adjustment 
 of my eye to the distance, by the convergence of the two eyes, 
 by the direction of the convergent eyes ; these sensations vary 
 with the sensation of brown color, in proportion as the eye, 
 in its movements, follows the outline and variously illumin- 
 ated portions of the book. There are two series of sensations, 
 whose position is in the box of the skull : these are the crude 
 materials. All the ulterior process consists in a coupling of 
 images. Thanks to the associated image of the muscular sen- 
 
 o o 
 
 sations which would conduct the exploration of touch up to 
 and along the book, the sensation of color, which belongs to 
 us, ceases apparently to belong to us, and appears an extend- 
 ed patch situated three paces from our eyes. Thanks to the 
 associated image of the sensations of contact and resistance 
 which our exploring touch would then experience, the patch 
 seems to us a solid extension. Thanks to the associated im- 
 age of the sensations which would be experienced at any time 
 by any being similar to ourselves, it seems to us that there
 
 CHAP. II.] THE EDUCATION OF THE SENSES. 
 
 is at that spot, something permanent, independent, and capa- 
 ble of exciting sensations, and which we term matter. Thus 
 arises the internal semblance, composed of an alienated and 
 wrongly situated sensation, of associated images, and, more- 
 over, in the man who reflects, of an interpretation and a name 
 which isolate and set apart a permanent character included in 
 the group. This semblance changes at every moment with 
 the sensations which form its support. On each new support 
 the associated images construct a new semblance, and the 
 mind is filled with innumerable inmates, a transient popula- 
 tion to which corresponds, each to each, the fixed population 
 of the outer world. 
 
 22
 
 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 BOOK III. 
 
 THE KNOWLEDGE OF MIND. 
 
 CHAPTER I. 
 
 THE KNOWLEDGE OF MIND. 
 
 I. HERE, then, we have reached the unextended centre, 
 a species of mathematical point, by relation to which we de- 
 fine all the rest, and which each of us calls / or me. We re- 
 vert to it at every instant of our life ; a very intense contem- 
 plation, almost amounting to ecstasy, is requisite to detach 
 us wholly from it, and to cause us to forget it for some min- 
 utes ; even then, by a sort of rebound, we re-enter upon our- 
 selves with greater energy ; we mentally review all the fore- 
 going scene, and say, mentally, twenty times in a minute; 
 " Just now I was in such a place, I looked in such a direction, 
 then in another, I had such an emotion, I made such a gest- 
 ure, and now I am here." Besides this, the idea of ourselves 
 is comprised in all our recollections, in almost all our previ- 
 sions, in all our pure conceptions or imaginations. Moreover 
 it is called up by all our sensations in any way strange or vivid, 
 especially those of pleasure or pain, and we often forget the 
 external world almost completely and for a considerable length 
 of time, to recall some agreeable or interesting passage of our 
 life, to imagine or desire some great good fortune, to observe 
 in the distance, either past or future, some series of our emo- 
 tions. But this ourselves, to which, by a perpetual recurrence, 
 we attach each of our successive events, is far more extensive 
 than any one of them. It is drawn out before our eyes with 
 certainty, like a continuous thread, backwards, over twenty, 
 thirty, forty years, up to the most distant of our recollections, 
 and further still, up to the beginning of our life, and it is 
 drawn out too, by conjecture, forwards, into other indetermi-
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 339 
 
 nate and obscure distances. For each new link we add to it 
 we review a longer or shorter fragment, a minute, an hour, a 
 day, a whole year, many years, sometimes an enormous por- 
 tion in the twinkling of an eye, and as if in a flash of light- 
 ning. This is why, when compared to our transient events, 
 this Ego assumes a sovereign importance in our eyes. We 
 must now examine what idea we have of it, of what elements 
 this idea is composed, how it is formed within us, why it is 
 called up by each of our events, what thing corresponds to it, 
 and by what adjustment this correspondence of the thing and 
 idea is effected. 
 
 II. What do we understand by an Ego, in other words by 
 a person, a soul, a spirit ? When we conceive some living 
 man, Peter, Paul, or ourselves, what idea is there within us, 
 and of what elements is this idea composed ? What we af 
 firm is, in the first place, a something, a being ; I purposely 
 employ the vaguest language, so as not to prejudice the mat- 
 ter. But, in pronouncing these words, we affirm nothing of 
 this thing, except that it is ; we say nothing of what it is, 
 that question we reserve. What we affirm is, secondly, that 
 it is a permanent being ; there is something in it which lasts 
 and remains the same. I exist to-day, but I existed yesterday 
 and the day before; and so with Peter and Paul. If both 
 they and I have changed in some respects, in other respects 
 they and I have not changed, and I conceive, in them as in 
 myself, something which has remained fixed. But, in saying 
 this, I do but affirm the permanence of something in them 
 and me ; I do not say what this something is ; I state its dura- 
 bility, not its quality ; that question we also reserve. What 
 we affirm is, thirdly, that this something is connected with a 
 particular organized body ; I have mine, Peter and Paul have 
 each their own, and we mean thereby to say that, as a general 
 rule, certain alterations of my body excite in me directly 
 some particular sensations, and that certain events in me 
 emotions or volitions excite directly in my body certain al- 
 terations ; the same being the case with Peter, Paul, and their 
 respective bodies. But this rule only states a constant rela- 
 tion between certain changes of a particular body and cer- 
 tain states of the unknown something ; what that relation is,
 
 340 THE KNOWLEDGE OF MIND. [Boou III. 
 
 still remains to be examined ; that question we again reserve. 
 After having stated its existence, its permanence, and its 
 principal relation, we must now inquire into the qualities 
 which determine it. 
 
 These qualities are its capacities and faculties. I am capa- 
 ble of feeling, of perceiving external objects, of recollecting, 
 of imagining, of desiring, of willing, of contracting my mus- 
 cles, and in this respect, Peter, Paul, and other men are similar 
 to myself. Moreover, in addition to these capacities common 
 to all men, I have others special to myself ; for instance, I am 
 able to understand a Latin book ; this porter can carry a 
 weight of 300 pounds ; here are precise capacities which de- 
 termine the unknown something. Let us reunite in one 
 group and one bundle all these capacities and faculties, com- 
 mon or special, which are met with in any one, and we shall 
 know what he is, in knowing what he contains. The vague 
 and empty sketch, which we had of the Ego or of the person, 
 becomes limited and is filled out. 
 
 III. Here, then, we are led to inquire into what we mean 
 by capacities and faculties. I have the capacity or faculty of 
 feeling ; this means that I am capable of having sensations; 
 sensations of various kinds, of smell, taste, cold, heat, and, 
 for instance, of sound. In other words, sensations of sound 
 which, if they arise, will be mine, are possible. They are pos- 
 sible because their condition is given, that is, a certain state 
 of my acoustic apparatus and of my sensory centres ; if this 
 condition ceased to be given, they would cease to be possible ; 
 I should no longer be able to hear sounds ; I should be deaf. 
 And so, a man has the faculty or power of perceiving exter- 
 nal bodies, especially by sight ; this means that sensations of 
 sight, which, if they arise, will be his, are possible. They are 
 possible upon two conditions ; his optical and cerebral appar- 
 atus must be in the proper state, and the education of the 
 sight must have associated in him with optical sensations the 
 image of certain muscular sensations ; as these two conditions 
 are given, his perceptions are possible ; if one or the other 
 were suppressed, his perceptions would cease to be possible ; 
 he would lose or would incompletely possess the faculty of 
 sight. So it is in all other cases, whether we consider a facul-
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 341 
 
 ty common to all men or a faculty special to an individual. I 
 have the power or faculty of moving my limbs, and of retain- 
 ing my ideas persistently. This means that this movement 
 of my limbs and this persistence of my ideas is possible ; the 
 movement is possible because its condition a certain state 
 of my muscular and nervous system is given ; this persist- 
 ence is possible because its condition a certain equilibrium 
 of my images is given. I have the faculty of understanding 
 a Latin book, and my neighbor the porter has the faculty of 
 carrying a load weighing 300 pounds ; this means that if I 
 read a Latin book, I shall understand it ; that if the porter 
 has a load of 300 pounds weight on his back, he will carry it. 
 The first act is possible to me, because its condition the 
 knowledge of the Latin words is given ; the second is possi- 
 ble to the porter, because its conditions the development of 
 his muscles and the habitude of bodily exercise are given. 
 Suppress one of these conditions ; the possibility disappears, 
 and the faculty perishes, until the missing condition is re-es- 
 tablished. Soften and waste away the porter's muscles by a 
 month's low diet ; he will no longer be able to lift his load. 
 If paralysis benumbs the nerves of my arm, I shall no longer 
 be able to lift that arm. If an hallucination prevents my sen- 
 sory centres from receiving the impression produced on my 
 retina by the rays emanating from the table ; as long as the 
 hallucination lasts, I shall be unable to perceive the table by 
 sight. On the other hand, cure the hallucination and the par- 
 alysis, and strengthen the weakened muscles ; the possibili- 
 ties, and with them the suspended faculties, will re-arise as 
 they were before. 
 
 Thus, faculty and capacity are wholly relative terms ; and 
 here we fall again into a similar analysis to that which we 
 effected with the properties .of bodies. All these words are 
 equivalent to that of power ; and, whatever be the power, 
 that of a dog which can run, that of a mathematician who can 
 solve an equation, that of an absolute king who can cause 
 heads to be cut off, the word never does more than state that 
 the conditions of an event or of a class of events are present. 
 There is nothing more useful than the knowledge of such 
 conditions ; it permits us to foresee events, those of others as
 
 342 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 well as our own. Consequently, we attach a great importance 
 to these powers ; they are to us the principal and essential 
 part of things ; we are tempted to form of them distinct en- 
 tities, to consider them as a primitive foundation, a stable 
 groundwork, an independent and productive source from 
 which events flow. The truth, however, is that a power is 
 nothing in itself, except an aspect, an extract, a particularity 
 of certain events, the particularity they have of being possi- 
 ble because their conditions are given. If these events are 
 mine or a consequence of mine, the power appertains to me. 
 In saying that I have such a power, I do but announce as 
 possible such an event, sensation, perception, emotion, voli- 
 tion, which will, perhaps, form part of my being, and some 
 other event, muscular contraction, carriage of a load, execu- 
 tion of an order, which will follow, sooner or later, a possible 
 state of my being. But these events and states are supposed, 
 not given ; they do but form part of my possible being, they 
 do not form part of my real being. One only of them will 
 arise at any particular moment ; the others, in unlimited 
 number, will not arise. The others will remain on the thresh- 
 old, or outside ; this single privileged one will enter alone> 
 and will alone form part of myself. I find, then, by way of 
 real elements and positive materials, to constitute my being, 
 nothing but my events and states, future, present, and past. 
 What there is actually in me is their series or web. I am, 
 then, a series of successive events and states, sensations, im- 
 ages, ideas, perceptions, recollections, previsions, emotions, 
 desires, volitions, connected together, excited by certain 
 changes of my body and of other bodies, and exciting certain 
 changes of my body and of other bodies. And, as it is plain 
 that my events, past, future, or possible, are all more or less 
 analogous to the daily events which I can seize at the mo- 
 ment, or almost at the moment, at which they are produced, 
 these last, the clearest and most near to us of all, are what I 
 proceed to study to know what constitutes the Ego. 
 
 IV. Let us, then, consider one of these events, or groups 
 of present events, some sensation of pain or pleasure, of con- 
 tact, of temperature, of taste or smell, some tactile and mus- 
 cular sensation, some preponderant image, some preponder-
 
 CHAP. I.] THE EDUCATION OF THE SENSES. 243 
 
 ant mental word, some emotion, desire, or volition. At the 
 present moment I suffer from headache, or I taste a fine 
 fruit, or enjoy myself by warming my limbs in the chimney- 
 corner ; I imagine or recollect, I am vexed or enlivened by 
 an idea, I decide on taking some step. These are the events 
 I find within me ; active or passive, voluntary or involuntary, 
 whatever be their shades, it is of no importance ; they con- 
 stitute my present being, and I attribute them to myself. 
 Now, all the events I attribute to myself have a common 
 character ; they appear to me as internal. 
 
 Let us begin with the most frequent of all, that is to say 
 the representations, ideas, and conceptions which we have of 
 objects, and especially of external bodies : for instance, I repre- 
 sent to my myself an old time-piece in the adjoining room. 
 Furniture, interiors of rooms, human or animal figures, trees, 
 houses, streets, landscapes it is representations of this class 
 whose series composes the ordinary current of our thought. 
 By a mechanism we have described, their hallucinatory ten- 
 dency is checked : they are affected by a contradiction which 
 negatives them as external objects ; they are thus opposed 
 to external objects ; in other words, they appear internal. 
 So it is with every idea, sensible or abstract, simple or com- 
 pound. For an idea is always the idea of some thing, and 
 consequently comprises two phases, the first an illusory one, 
 in which it seems the thing itself; the second a rectified one, 
 in which it appears a simple idea. This transformation it un- 
 dergoes opposes to each other the two phases which consti- 
 tute it ; we express this passage by saying that we re-enter 
 upon ourselves, and that, from the object, we revert to the 
 subject ; it is, then, the same event or group of events which, 
 according to its successive states, constitutes, first, the ap- 
 parent object, then the actual subject. Thus the rectifying 
 operation, by which an idea appears as an idea, is also the re- 
 flection by which this idea appears as something internal ; 
 and the contradiction which negatives it as a fragment of the 
 outer world gives it at the same time a position as a frag- 
 ment of the inner world. 
 
 We must now observe that every idea, conception, and 
 representation has a double face. On the one hand, it is a
 
 344 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 cognition ; on the other hand, it is an emotion. It is agreea- 
 ble, painful, surprising, startling, tender, consoling. Its en- 
 ergy, its weakenings, its intermittences, are precisely the en- 
 ergy, the weakening, the intermittences of the emotion. 
 There is but one and the same fact with two aspects, one in- 
 tellectual, the other affective and impulsive. You are told 
 that some one whom you left yesterday in good health has 
 suddenly died, and this idea upsets you. You are told that 
 a near relation is seriously ill, and this idea afflicts you. It 
 excites a general shock, or kind of sharp pain, which contin- 
 ues, though growing feebler, and thus causes a lasting disor- 
 der. There is nothing strange in this long trouble, which 
 starts from an idea and lasts over a series of ideas, seeming 
 to us, like the ideas, internal; in the desires and volitions 
 which spring from it being similarly referred to within ; in the 
 sequences and characters of the ideas being opposed, like the 
 ideas, to the outer world, and incapable of finding a place 
 there. 
 
 There remains for inquiry, why the sensations which we 
 localize in our bodies also appear to us as internal, and are 
 referred by us to ourselves. To find the reason of this, it is 
 sufficient to compare them with those equally belonging to 
 us, and which nevertheless we do not attribute to ourselves, 
 those of color and sound. We have seen the mechanism 
 which projects these in appearance beyond our body ; if they 
 are alienated from us, it is because they are projected out of 
 our precinct. It is, then, because the others, those of con- 
 tact, of pressure, of heat, of muscular effort, of local pain, of 
 taste, and smell, are not projected beyond our body, that they 
 are not alienated from us ; their position is the cause of their 
 attribution ; we refer them to ourselves because our body, 
 compared with others, has singular and special characters. 
 In fact, it is by its medium that we perceive other bodies and 
 act upon them. Whether the action comes from us or them, 
 it is always between them and us. In order for us to know 
 other bodies, it is first necessary for one of the organs of cm- 
 body to be disturbed ; in order for us to impress motion on 
 other bodies, it is first necessary for one of the muscles of our 
 body to be contracted. It is our first movable thing, and
 
 CHAP. I.] THE KNOWLEDGE OF THE SENSES 345 
 
 first motive power ; with relation to other things, it is always 
 inside ; with relation to it, other things are always outside. 
 It is our immediate precinct, in such a way that, if we com- 
 pare it to other things, it is a within and they are a without* 
 This is why the sensations of which we have been speaking, 
 though placed by us in our organs, appear as internal, and 
 are referred to self. Such is our conception of the actual 
 subject ; these are the present and real facts it comprises. 
 That which I actually am, that which constitutes my real be- 
 ing, is a certain present real group of sensations, ideas, emo- 
 tions, desires, volitions ; my conception of my actual being 
 comprises these events only, and all these events, on analysis, 
 present this common character, that they are pronounced in- 
 ternal, whether because, as ideas and sequences of ideas, they 
 are opposed to objects and deprived of situation, or because 
 their apparent position is met with in our body. 
 
 V. Now, at the preceding moment, the subject being 
 wholly similar, contained events only of the same class ; the 
 same observation is to be made for each of the anterior mo- 
 ments. And, in fact, when we consider any of these moments 
 by recollection, we find they are all similar to the present mo- 
 ment ; just now, when in the other room, I felt cold, and 
 walked, I looked at the clock, I foresaw, I desired, I willed, as 
 at this moment. Consequently, my past, as my present events, 
 have all this character of appearing internal. In this way 
 they form a chain, whose links, all composed of the same 
 metal, appear at once united and distinct. For, according to 
 the mechanism we have described and explained, on the one 
 hand the image which constitutes a recollection seems pro- 
 jected backwards, and recedes beyond the repressive images 
 or sensations, which separates it from them ; and, on the 
 other hand, the same image, becoming precisely situated, 
 seems to be joined by its posterior extremity to the anterior 
 extremity of the repressive images or sensations, and is thus 
 joined to them ; so that our events appear to us as a continuous 
 line of contiguous elements. We pass without difficulty from 
 one link to another ; according to the well-known law which 
 governs the revival of images, the images of two successive 
 sensations mutually tend to call each other up ; when, there-
 
 346 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 fore, the image of some one of our anterior moments revives 
 in us, the image of the preceding and that of the succeeding 
 moment tend to revive by association and correspondence. 
 
 Not only do we pass by these means from one of our mo- 
 ments to an adjacent one ; but, by means of abbreviations 
 which collect in one image a long series of moments, we pass 
 from one period to another of our life. In fact, if, in order to 
 recollect one of our somewhat distant events, it were neces- 
 sary to call up the images of all our intermediate sensations, 
 the operation would be of prodigious length ; strictly speak- 
 ing, it would require as much time as elapsed between that 
 event and the present moment. For the whole detail and du- 
 ration of the intermediate sensations are reproduced in the 
 images which conduct us backwards to that event ; it would 
 thus require twenty-four hours to recall a sensation of yester- 
 day. For this Nature has supplied a remedy in the oblitera- 
 tion which images undergo,* and in the property possessed 
 by certain prominent images of being the abbreviatory sub- 
 stitutes of the group in which they are included. For in- 
 stance, this morning I went into such a street, and such a 
 house ; at present, if I recall my walk, numbers of details are 
 missing ; many of my sensations do not revive. I do not see 
 again the different figures of the houses, carriages, and pass- 
 ers-by, which I then saw ; nine out of ten of them are oblit- 
 erated definitively and for ever ; of all these impressions there 
 is but a remnant capable of reviving. Again, it almost always 
 happens that, in ordinary life, I do not give it time to rise ; it 
 would be necessary for me to dwell on it, to search in my 
 memory. It is only when I search that I see again certain 
 precise details, some shop, some interesting countenance, 
 some striking part of the street. If I do not dwell on it, if I 
 do not drive away supervening impressions and distractions, 
 if I do not give my recollections time to become precise and 
 complete, they almost all remain in the latent state ; that 
 which survives and emerges is one fragment out of ten 
 thousand, the vague representation of my progress at some 
 moment in the street, of my arrival in the house, or of the at- 
 
 * Part i. book ii, chapter ii.
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 347 
 
 titude of the friend I went to see. But this is enough ; the 
 shred which is preserved supplies the place of the rest ; I 
 know by experience that by concentrating my attention upon 
 it, I should revive several similar ones of the same series ; it 
 is to me in future the summary representation of the whole. 
 So is it with the breakfast I had previously eaten, with the 
 reading which occupied the first hours of the morning ; so 
 that, with three abbreviatory substitutes, I remount in a mo- 
 ment to my getting up, that is to say to an incident separated 
 by ten hours from the present moment. 
 
 The more distant the event, the greater is the obliteration 
 of the images ; and the greater the obliteration, the more 
 things does the abbreviatory substitute comprise. My doings 
 of yesterday or the previous day subsist in me only through 
 some striking event, some visit I received, some domestic oc- 
 currence for which it was necessary to provide. If I recede 
 still further, I perceive only, in the shipwreck an irremediable 
 swallowing up of my innumerable anterior sensations, a few 
 surviving images, my arrival at the country house I am stay- 
 ing in, the first green leaves of spring, a winter's evening at a 
 particular house, the appearance of a strange town I visited a 
 year ago. I may thus go back very far and very fast, and by 
 springing from peak to peak, may reach in an instant things 
 ten or twenty years distant. Add to this the calendar, cal- 
 culations, all the different means which we possess, and which 
 children and savages do not possess, of measuring this distance. 
 Thanks to an association of images, we place our events in the 
 series of days and months with which the almanac furnishes 
 us, in the series of years furnished by chronology. When 
 this is effected, we render precise, by these auxiliary charts, 
 the position which our various events occupy in duration with 
 reference to one another, and are able, not only to review in 
 a second our most distant events, but also to estimate the in- 
 terval separating them from the present. 
 
 By this operation, more or less perfected, we embrace very 
 long fragments of our being in an instant, and, so to speak, 
 in a single glance. The distinct events whose succession has, 
 during this interval, constituted our being, cease to be dis- 
 tinct ; they are obliterated by the abbreviations and the
 
 348 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 speed ; nothing of the series survives, except a character com- 
 mon to all the elements traversed, the particularity they have 
 of being internal. There remains, then, the idea of an internal 
 something, of a ^vithin, which is, in this respect, opposed to 
 all the without, which is always met with the same at all mo- 
 ments of the series, which, consequently, lasts and subsists, 
 which, for this reason, appears to us of superior importance, 
 and which attaches to itself, as accessories, the various tran- 
 sient events. This stable within is what each of us calls / or 
 me.* Compared to its events, which pass away while it sub- 
 sists, it is a substance ; it is denoted by a substantive or a pro- 
 noun, and it incessantly reverts to the most prominent place 
 in oral or mental discourse. Henceforward, when we reflect 
 on it, we permit ourselves to be duped by language ; we for- 
 get that its permanence is apparent, that, if it appears fixed, 
 it is because it is incessantly repeated, that it is in itself noth- 
 ing more than an extract from internal events, that it derives 
 from them all its being, that this borrowed being, detached 
 by fiction, isolated by the oblivion of its connections, is noth- 
 ing in itself and apart. If we do not undeceive ourselves by 
 a rigid analysis, we fall into metaphysical illusion ; we are dis- 
 posed to conceive it as a distinct thing, stable and independent 
 of its modes of being, and even capable of subsisting after the 
 series from which it is derived has disappeared. 
 
 Another metaphysical illusion comes in to complete its 
 being and effect its isolation. We have classed its events 
 and the facts which its events excite according to their re- 
 semblances and differences, and we have placed each group 
 in a distinct compartment and under a common name here 
 sensations, there external perceptions, there, again, recol- 
 lections, volitions, voluntary movements, and so on. Con- 
 sidering our present state, we know or suppose that the 
 conditions of these events are present in other words, that 
 these events are possible ; we express this by saying that 
 we have the power, capacity, or faculty of feeling, perceiving, 
 
 * According to some, the word I ( je, ich, ego, aham) comes from the root ah, 
 to breathe, and denotes the inner breath ; according to others, it comes from the 
 root gha, ha, which signifies this one, and by which a person speaking denotes him 
 self to his listener. Max Mueller, " The Science of Language."
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 249 
 
 recollecting, willing, contracting our muscles. Besides these 
 powers common to all men, each of us discovers in himself, 
 by a similar experience, special powers peculiar to himself. 
 Now, when we consider these powers, we find them all more 
 or less permanent. They precede events, and, in general, 
 survive events. They last intact during long years, some 
 during our whole life. They thus form a contrast with tran- 
 sitory events, and seem the essential part of man. In this 
 way their notion is attached to the notion of the persistent 
 Ego ; thereupon this Ego ceases to appear to us as a simple 
 within; it becomes furnished, is qualified, and determined; 
 we define it by the group of its powers, and, if we allow 
 ourselves to slip into metaphysical error, we set it apart as 
 something complete and independent, invariably the same 
 under the flow of its events. 
 
 VI. Such is the notion of the Ego. Illusory in the meta- 
 physical sense, it is not so in the ordinary sense ; we cannot 
 pronounce it void ; there is something corresponding to it, 
 something very analogous to that which, according to our 
 analysis, constitutes the substance of bodies. This some- 
 thing is the permanent possibility of certain events under 
 certain conditions, and the permanent necessity of the same 
 events under the same conditions, with the addition of a 
 complementary one, all these events having a common and 
 distinctive character, that of appearing as internal. Thus 
 we are entitled to say, while preserving exactly the mean- 
 ings of our words, that the Ego is a force as bodies are a 
 force which, with relation to them, is a within, as they, with 
 relation to it, are a without. These three words, force 
 within, without, express relations only ; nothing more ; at 
 all the moments of my life, I am a within, capable of 
 certain events under certain conditions, and whose events 
 under certain conditions are capable of exciting other events 
 in itself or others. This is what endures in me, and this 
 will be invariably the same at all the instants of my ex- 
 istence. It is manifest that we have not here a primitive 
 notion. It has precedents, elements, and a history, and we 
 may reckon all the steps of the involuntary operation which 
 results in forming; it.
 
 THE .KNOWLEDGE OF MIND. [BOOK. III. 
 
 It is necessary, first, that we should have recollections 
 and exact recollections. It is further necessary that, by the 
 fixing of our recollections, our events should appear to us 
 as a continuous thread. It is then necessary that, thanks 
 to the abbreviations of memory, the particularities of our 
 events should be obliterated, that a character common to 
 all the elements of the thread should predominate, be disen- 
 gaged, be isolated, and erected, by a substantive name, into 
 a substance. It is further necessary that we should acquire 
 the idea of the powers, capacities, or faculties of this sub- 
 stance, therefore, that we should classify our events accord- 
 ing to their various kinds, that, by a more or less prolonged 
 experience, we should discover their external and internal 
 conditions, that, stating or presuming the presence of con- 
 ditions, we should conceive these events as possible, and 
 finally, that isolating this possibility, we should attribute it 
 to ourselves, under the name of power, capacity, or faculty. 
 The idea, then, of the Ego, is a product ; many variously elabo- 
 rated materials concur in its formation. Like every mental 
 or organic compound, it has its normal form ; but, in ordpr 
 that it may attain this form, certain materials and a certain 
 elaboration are required ; with a very slight change in the 
 elements and derangement of the process, the form is de- 
 viated from and the final result is monstrous. Consequently 
 the idea of self may deviate and become monstrous ; and, 
 nearly as we are situated to ourselves, we may deceive our- 
 selves in many ways respecting our self. 
 
 In the first place, certain foreign elements may introduce 
 themselves into the idea we have of it. There are circum- 
 stances in which a series of imaginary events inserts itself in 
 the series of real events ; we then attribute to ourselves what 
 we have not experienced and have not done. In the waking 
 state, this ocurrence is rare; and seldom happens except with 
 men whose imagination is over-excited. I have mentioned 
 the story of Balzac, who described one day, at the house of 
 Madame de Girardin, a white horse he intended to present to 
 his friend Sandeau, and who, a few days afterwards, in the 
 persuasion that he had actually given it, inquired of Sandeau 
 about it. It is plain that the starting-point of an illusion like
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 25 1 
 
 this is a voluntary fiction ; the author of it is at first aware 
 that it is fictitious, but finally forgets it. With barbarous 
 people, in uncultivated and childish minds, many false recol- 
 lections thus take root. Men have seen a very simple fact ; 
 gradually, when it is distant, in thinking of it, they interpret 
 it, amplify it, provide it with details, and these imaginary de- 
 tails, becoming incorporated with the recollection, end by 
 themselves seeming to be recollections. The majority of 
 legends, and religious legends especially, are formed in this 
 way. A peasant, whose sister had died abroad, assured me 
 that he had seen her soul the very evening of her death ; on 
 inquiry being made, this soul was a phosphorescence produced 
 in a corner on an old chest of drawers, where there was a bot- 
 tle of spirits of wine standing. The guide of a friend of mine 
 at Smyrna declared that he had seen a young girl carried 
 through the air in full daylight by enchantment ; the whole 
 town had witnessed the miracle ; after fifteen hours skilful 
 questioning, it became evident that all the guide recollected 
 was having seen on that day a small cloud in the sky. In 
 fact, what constitutes recollection is the spontaneous recoil 
 of a representation which becomes precisely fixed between 
 certain links in the series of events which form our life. When 
 this recoil and this fixing have become involuntary, when we 
 no longer remember that they were at first purely voluntary, 
 when finally no other representation is projected to the same 
 spot and rises there to form an obstacle, the false recollection 
 is taken for true. 
 
 All these conditions are met with in dreams ; this is why we 
 have, when dreaming, not only false external perceptions, but 
 also false recollections.* I have noted many such in my own 
 case ; only lately, I imagined myself to be in a d^aving-room 
 turning over an album of landscapes. The first of these pic- 
 tures represented the Polar Sea, a great expanse of blue wa- 
 ter, surrounded with icebergs. At this moment, I perceived 
 
 * September 28, 1868. M. Maury cites many false recollections which he 
 has had in dreams. "Le Sommeil," etc., p. 211, and p. 70. See ante, p. 65 (part 
 i. book ii. chap, i.), the story of the old man who attributed to himself the travels 
 he had read, as well as those he had actually made.
 
 352 THE KNOWLEDGE OF MIND. [BooKlII. 
 
 the artist standing before me, and felt myself compelled to 
 praise aloud the beauty of the work ; I turned over the pages, 
 and the pictures seemed to me to grow more and more 
 wretched, and suddenly I recollected that, a year ago, I had 
 had this album in hand, that I had even noticed it in a newspa- 
 per that my article, by no means a laudatory one, was of about 
 thirty or forty lines on the third column of the second page. 
 On this recollection, I felt so confused that I woke up. Now, 
 observe that the whole dream was a fiction ; but the recoil 
 and fixing took place spontaneously without meeting a contra- 
 dictory representation, in such a way that the imaginary 
 article found itself affirmed. 
 
 So, again, there is nothing more common than false recol- 
 lections in cases of insanity, and especially with monomaniacs. 
 Such persons form a romance in accordance with their ruling 
 passion, and this romance inserted in their life ends by com- 
 posing in their eyes all their past life. A woman whom I 
 have seen at Salpetriere, told, with perfect precision and con- 
 viction, a story according to which she was noble and wealthy. 
 Her real name was Virginie Silly, and she called herself 
 Eugenie de Sully. To believe her, her parents had purposely 
 lost her seven or eight times, and her mother had finally sold 
 her to a mountebank, with whom she remained two years. 
 Before 1848, she had interviews with Louis Philippe and 
 made reports to him on the Casino, the Chaumiere, the 
 Ranelagh, and the hospitals. " I was," she said, " commis- 
 sary-reporter to his Majesty, and the King gave me large 
 sums." Later on, when she was living in the Rue Poisson- 
 niere, the Emperor came to listen to her conversation from 
 behind a screen, and caused her to be locked up. One of her 
 uncles, a slave dealer in Chili, left her six millions ; she has 
 still a quarter of a million in the Bank. But she has been 
 robbed of her papers and parchments, and in their stead has 
 been left a false register of birth, according to which she is 
 poor and of humble origin.* Another woman, in the service 
 of M. Metivier, and the daughter of a porter in a public office, 
 
 * From a note of a Lecture by M. Baillarger, at the Salpetriere, in 1856. The 
 Professor questioned the patients in the presence of his class.
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 353 
 
 being young and pretty, imagined that the minister frequently 
 noticed her, and alleged that he had communicated with her 
 through a procuress. On this, her lover, who was a clerk in* 
 the office, broke off the engagement. She married a work- 
 man, became pregnant, was confined, and, in the meantime, 
 the minister died ; she then announced that he had left her 
 by will two hundred thousand francs. Her false recollections 
 were so clear that her lover abandoned her, and her husband 
 almost believed her.* In somnambulism and hypnotism, the 
 patient who has become extremely sensible to suggestion, is 
 subject to similar illusions of memory; he is told that he has 
 committed such and such a crime, and his figure at once ex- 
 presses horror and dismay. Ordinary recollections no longer 
 present themselves, or are too feeble to exercise their ordinary 
 power of repression ; in the absence of the normal counter- 
 poise, the simple conception becomes an affirmative concep- 
 tion, and the patient recollects murders which he has not 
 committed. 
 
 Other cases present the inverse illusion. We then no 
 longer deceive ourselves by addition, but by exclusion ; in- 
 stead of inserting in our series events which do not belong 
 to us, we cast out of our series events which are really ours. 
 This is the error into which we fall respecting colors and 
 sounds ; its mechanism has been described. These, in them- 
 selves, are sensations, like those of heat or taste ; but as they 
 are repulsed from our nervous surface, they appear detached 
 from us ; by this alienation, sound appears as an external 
 event, and color as a quality of a body other than ourselves. 
 This error is normal, and we have shown in what way it is 
 useful. But there are others which are abnormal, and brirfg 
 disturbance into all our conduct ; these are the hallucinations 
 termed psychical ; f in such cases, the patient alienates and 
 refers to others thoughts which are his own ; he understands 
 by thought, he hears " secret internal voices ; " they speak to 
 him " silently; " he sees " invisibly." The wife of an English 
 officer at Charenton spoke of a sixth sense by which' she 
 
 * See Leuret, " Fragments Psycho! ogiques," for an analogous case of a mad- 
 nan called Benoit (p 64). 
 
 f Baillarger, " Des Hallucinations," part i. 
 
 23
 
 354 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 heard voices ; it was " the sense of thought." When we 
 question such patients, they reply that the word voice of 
 which they avail themselves is very inappropriate, and that 
 they use it by way of metaphor, for want of a better word ; 
 the voice has no tone, it does not seem to come from the 
 outer world as in ordinary cases ; mystics have already made 
 this distinction, and oppose "intellectual speech and voices" 
 which their soul seizes without the intervention of the organs 
 of sense, to bodily voices which they perceive in the same 
 way as in ordinary life. Blake, the poet and engraver, who 
 called up the illustrious dead, conversed with them " soul to 
 soul," and, as he said, " by intuition and magnetism." It is 
 easy to recognize that the ideas which such persons attribute 
 to others belong to themselves. A person talking with Blake 
 begged him to ask Richard III. if he professed to justify the 
 murders he had committed during his life. " Your question," 
 said Blake, "has already reached him. . . . We have no need 
 of words. This is his answer, only it is somewhat longer 
 than he gave it me, for you would not understand the lan- 
 guage of spirits. He says that what you call murder and 
 carnage is all nothing ; that in slaughtering fifteen or twenty 
 thousand men you do no wrong, for what is immortal of them 
 is not only preserved but passes into a better world, and the 
 man who reproaches his assassin is guilty of ingratitude, for 
 it is by his means that he enters into a happier and more 
 perfect state of existence. But do not interrupt me, he is 
 now in a very good position, and if you say anything more 
 he will go." It is evident that Blake imputed his own 
 theories and dreams to Richard III. ; the person he imagined 
 was an echo which sent him back his own thought. A mad- 
 woman played incessantly at even or odd with an absent per- 
 son whom she believed to be the prefect of police ; before 
 playing, she looked at the coins she had in her hand, and 
 thus knew their number ; the prefect, therefore, always 
 guessed wrong, and never failed to lose ; later on, she neg- 
 lected her preliminary examination; and then, the prefect 
 sometimes lost, and sometimes won. It is evident that, at 
 first, she herself fabricated, without suspecting it, the error 
 s'.ie attributed to the prefect.
 
 C:IAP. I.] THE KNOWLEDGE OF MIND. 355 
 
 The starting point of these illusions is not hard to distin- 
 guish ; we find it in the process of mind of the dramatic au- 
 thor, the novelist, of every person of lively imagination ; in 
 the midst of a mental monologue, there springs up an address, 
 an answer, a kind of internal person rises and addresses us in 
 the second person : " Rentre en toi-meme, Octave, et cesse 
 de te plaindre." Now suppose that these addresses, these 
 answers, while remaining mental, are wholly unforeseen and 
 involuntary a thing which often happens. Suppose they 
 comprise strange and sometimes terrible ideas, that the 
 patient cannot excite them at will, that he undergoes them, 
 that he is beset by them.* Suppose, in a word, that these 
 discourses are well connected, indicate an intention, impel 
 the patient in one or another direction, towards devotion or 
 towards vice. He will be tempted to attribute them to an 
 invisible speaker, especially if the religious atmosphere in 
 which he lives, and his own special creed, authorize his fabri- 
 cating such a speaker. The whole series which constitutes 
 the Ego is thus cut into two parts, because the two partial 
 series which compose it present distinct or even opposite 
 characters. Sometimes, when the second has nothing extra- 
 ordinary about it, the patient still attributes it to himself, and 
 believes himself to be double. " I am led to believe," says a 
 sufferer from hallucinations, " that I have always had within 
 me a double thought, one of which controls the actions of 
 the other." " There is," says another patient, " as it were a 
 second myself who inspects all my actions and words, like an 
 echo which repeats everything." A third, recovering from a 
 fever, " believed himself formed of two individuals, one of 
 which was in bed, while the other walked about ; although 
 he felt no appetite, he ate largely, having, as he said, two 
 bodies to support. "f At other times, the second series is 
 referred to another person, especially when the ideas it con- 
 tains are out of proportion to those which make up the first 
 
 * See the whole autobiography of Bunyan, the author of the " Pilgrim's Pro- 
 gress." Also the eloquent and sublime conversations of Tasso with his familiar 
 genius, recorded by Manso. So again, the warnings given to Socrates by an 
 internal voice. 
 
 f Griesinger, p. 93, and Baillarger, op. cit. passim.
 
 356 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 series. Thus were formed the demon of Socrates, and the 
 familiar genius of Tasso. Usually, after a time, sensorial 
 hallucination comes in to complete psychical hallucination. 
 The internal mental voices become physical and external. 
 " At first, according to patients, it was something ideal and 
 like a spirit speaking in them ; now, they actually hear 
 speech ; " the voices are clear or indistinct, deep or high, 
 melodious or screeching. I have already mentioned the 
 case of Theophile Gautier, and how, passing once before the 
 Vaudeville, a phrase printed on the notice-board fastened it- 
 self upon his recollection, how, in spite of himself, he inces- 
 santly repeated it, how after some time it ceased to be 
 simply mental, and seemed to proceed from a bodily throat, 
 with distinct tone and accent ; it revisited him thus, at in- 
 tervals and unexpectedly, and this lasted several weeks. 
 Suppose a mind preoccupied, beset with fears, assume that 
 the voice pronounces, not only a single monotonous phrase, 
 but a series of threatening and appropriate speeches, and we 
 have the case of Luther at the Wartburg, when he disputed 
 with the devil. The mental words have excited in the sen- 
 sory centres of the encephalon corresponding sensations of 
 hearing, and henceforth, detached in this double sense from 
 the Ego, they are imputed to an interlocutor. 
 
 These illusions are partial only ; there are total illusions, 
 in which the series of our events is replaced by a strange 
 series. Peter imagines himself Paul, and acts on the belief. 
 Here again, the starting point of the error is in a well-known 
 process of the mind, that of the novelist or author who puts 
 himself in the place of his characters, adopts their passion, 
 and experiences their emotions. This operation is nowhere 
 so clearly seen as in hypnotism ; the attention of the patient 
 is then limited and concentrated, and rests only on one series 
 of ideas ; this alone is developed ; all others are benumbed, 
 and, for the time, incapable of reviving ; consequently ordin- 
 ary recollections are missing and no longer exercise their re- 
 pression ; the illusion which, in the author and novelist, is 
 upset at every moment, is now no longer checked and follows 
 its course.* " A. B. was asked his name, he answered rightly, 
 
 * " Annales Medico-psychologiques," 4 "" Serie, vi. 428. Dr. Hack Tuke, 
 " De la Foiie Artificielle."
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 357 
 
 without hesitation. When hypnotized and in the state of 
 coma (being capable of holding himself upright and in appear- 
 ance wide awake, though with a strange wandering air as in 
 somnambulism) it was strongly suggested to him that he was 
 Richard Cobden. A few seconds afterwards he was asked 
 his name. He answered at once, and without hesitation, 
 ' Richard Cobden.' ' Are you perfectly sure of it? ' ' Yes,' 
 he answered. Similar experiments tried with different 
 names, on various other occasions, had always the same re- 
 sults. During the state of normal wakefulness, the subjects 
 experimented on gave their proper names as soon as they 
 were asked. On the contrary, if during the fitting period of 
 hypnotic sleep the name of a king was suggested to them, 
 not only were they impelled to say that it was their name, 
 but they felt and acted in a way which manifested their convic- 
 tion that they were kings" 
 
 This state, instead of being transient, may become fixed ; 
 this is frequent in the asylums, and is often met with in 
 periods of religious exaltation. A quartermaster in Crom- 
 well's army, James Naylor, believed himself God the Father, 
 and was worshipped by many enthusiastic women. He was 
 tried by Parliament, and sentenced to the pillory. We find, 
 in asylums, lunatics who believe themselves Napoleon, the 
 Virgin Mary, the Messiah, or some other person. One of 
 them named Dupre, a patient of Leuret, believed and said 
 that he was at once Napoleon, Delavigne, Picard, Andrieux, 
 Destouches, and Bernardin de Saint-Pierre. A woman called 
 Catherine, mentioned by Leuret, is no longer herself; she 
 does not call herself Catherine ; there is a rupture be- 
 tween her past and present ; she only speaks of herself in the 
 third person, saying " the person of myself." Others are 
 transformed into animals. " There was a man of Padua," 
 says Wier, " in 1541, who believed himself to be changed into 
 a wolf, and ran about the country attacking and killing all 
 he met. After many difficulties, they contrived to seize 
 him. He said boldly to those who arrested him : ' I am 
 really a wolf, and if my skin does not look like a wolfs skin, 
 it is because it is turned and the hair is inside.' In order to 
 assure themselves of the fact, they wounded the wretched
 
 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 man in different parts of his body, and tore off his arms and 
 legs." If the patient experiences false sensations, through 
 hypnotism or illness, he may come to form the most eccentric 
 ideas of his body, and therefore of his personality. " Among 
 a number of hypnotized women," says Dr. Elliotson, " one 
 imagined that she was made of glass, and was afraid that she 
 might become broken ; another that she was no bigger than 
 a grain of wheat ; another that she was dead." And so, some 
 insane persons are convinced that their body is made, of wax, 
 of butter, of wood, and act accordingly. Leuret mentions 
 men who believe themselves changed into women, and wo- 
 men who believe themselves men. A soldier whose skin had 
 become insensible, believed himself to have been dead since 
 the battle of Austerlitz, where he received a wound. " When 
 he was asked as to his health, he said ' You want to know 
 how Father Lambert is ? But there is no Father Lambert ; 
 a cannon-ball killed him at Austerlitz ; what you see here is 
 not him ; it is a wretched machine made to look like him ; 
 you ought to ask them to make a better one.' " In speak- 
 ing of himself he never said me, but always it* 
 
 In short, the conception which I have of myself at any 
 given moment is an abbreviatory and substitutive name, 
 sometimes my name, sometimes the word / or me, both of 
 them mentally pronounced. If I dwell on this name, it will, 
 in the normal state, call up in me, by association, its equiva- 
 lent, that is to say the series of my actual and interior events, 
 joined with the numerous series of possible events of which I 
 am actually capable. But this principal association, being 
 an acquired one, may be lost ; and so it is with the secondary 
 associations which solder together in my mind the various 
 fragments of the whole series. If an extrinsic fragment or an 
 extrinsic series then comes to intercalate itself in the empty 
 place, the patient will be mistaken about himself. We have 
 just seen the principal conditions of this transposition. 
 
 * Analogous illusions occur in dreams. M. Charma dreamed once that he 
 was aide-de-camp to Henry IV. ; another time that he was Voltaire. Dr. Mac- 
 nish dreamed that he was a pillar of stone, and saw all that passed around him. 
 De Quincey, the opium-eater, dreamed that he was the idol in a Brahminical 
 temple, etc.
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 359 
 
 Sometimes the energy of the normal associations is weakened, 
 as in sleep and hypnotism ; the link which binds my name to 
 the word / is weakened ; consequently, a persistent sugges- 
 tion is capable of substituting for my name that of another ; 
 henceforward this name with the whole series of events of 
 which it is the equivalent is called up m me as soon as the 
 word / reverts mentally, and henceforward I am, in my own 
 eyes, some other person Richard Cobden, or Prince Albert. 
 Sometimes the energy of the normal associations is con- 
 quered by a greater force. The pure conception which, 
 repressed by the series of recollections, was at first checked 
 in its evolution, now accomplishes its development in accor- 
 dance with its hallucinatory tendency. Incessantly repeated, 
 with daily increased vividness, maintained by a ruling passion, 
 by vanity, love, or religious scruples, sustained by false sen- 
 sations ill interpreted, confirmed by a group of suitable 
 explanations, it assumes a definite ascendancy, annuls con- 
 tradictory recollections ; being no longer negatived, it is 
 pronounced affirmative ; and the fiction, which was at first 
 declared a fiction, seems a true story. Thus, our idea of 
 our person is a group of co-ordinated elements whose mutual 
 associations, ceaselessly attacked and ceaselessly victorious, 
 are maintained during our waking hours and reason, as the 
 composition of an organ is maintained during health and 
 life. But madness is always hovering near the mind, as 
 illness is always hovering near the body; for the normal 
 combination is a victory only ; it results from and is renewed 
 by the continual defeat of the contrary forces. Now, these 
 last are always present ; an accident may give them the 
 preponderance ; there is but little required to enable them to 
 assume it ; a slight alteration in the proportion of the ele- 
 mentary affinities and in the direction of the constructing 
 process would bring on a degeneracy. Morally or physically, 
 the form we term regular may indeed be the most frequent, 
 but it is through an infinite number of possible deformations 
 that it is produced. We may compare the silent elaboration 
 of which consciousness is the ordinary result to the progress 
 of the slave, who, after the games of the circus, crossed the 
 length of the arena, among wearied lions and glutted tigers,
 
 360 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 bearing in his hand an egg ; if he arrived safely, he received 
 his freedom. So passes the mind through the confusion of 
 monstrous deliria and yelling madness, almost always with 
 impunity, to settle itself in accurate consciousness and exact 
 recollection. 
 
 VII. How does it happen that the slave arrives so fre- 
 quently at his destination ? Whence comes it that our present 
 recollections almost invariably correspond to past sensations ; 
 that the place we assign to these sensations is almost invaria- 
 bly that which they actually occupied ; that it scarcely ever 
 happens that the chain of our events lets slip one of its own 
 links or receives a link that does not belong to it ; that the 
 group o'f past, present, and possible events, of which we com- 
 pose our personality is, almost always, really the group of 
 events which have happened to us, are passing within us, and 
 which may occur to us? By what adjustment is the almost 
 invariable accordance of our thought and our being set up ? 
 It must be understood that we do not here undertake to dem- 
 onstrate the veracity of memory ; the thing is impossible. In 
 fact, such a proof would be reasoning in a circle ; for, if mem- 
 ory be accurate, it is through certain laws which accommodate 
 the recollection to its object ; now these laws can only be ob- 
 tained by us from the facts we observe and which we remem- 
 ber for the purpose of comparing them ; so that, in order to 
 prove the fidelity of memory, it would first be necessary to 
 admit the fidelity of memory. We do admit it and without 
 much hesitation, if not upon a direct demonstration, at least 
 after a host of innumerable confirmations, and as an hypoth- 
 esis justifying the whole of the experience, verifications, and 
 previsions of mankind. This, when settled, is enough to ex- 
 plain it, and we have but to regard the described mechanism 
 to comprehend the almost infallible accuracy of its working. 
 
 In the first place, what constitutes recollection is a present 
 image which appears a past sensation, and which, by the re- 
 pressive contradiction of present sensations, finds itself con- 
 strained to an apparent recoil. Now, we have seen fhat the 
 sensation, after it has ceased, has the property of reviving by 
 its image ; as a general rule, almost every clear and circum- 
 stantial image supposes an antecedent sensation ; so that, if
 
 CHAP. I.] THE KNOWLEDGE OF MIND 36 r 
 
 our judgment is invariably false in itself, it is almost invaria- 
 bly true by correspondence. We invariably deceive ourselves 
 by taking the present image for a distant sensation ; but, as a 
 rule, the distant sensation was produced. If the image by its 
 presence excites a constant illusion which forms recollection, 
 on the other hand, it compensates this illusion by its origin, 
 which is almost invariably an anterior sensation ; if I may 
 venture to say so, it rectifies, on the one hand, the error into 
 which it leads us on the other. 
 
 Secondly, what situates the repulsed image before some 
 particular sensation is the presence of that sensation or the 
 recall of that sensation by its image. Now, as we saw in 
 proving the laws which govern the revival of images, my pres- 
 ent sensation tends to call up the image of the preceding sen- 
 sation contiguous to it ; and, in general, images of sensations 
 which have been contiguous, tend to call each other up ; 
 whence it follows that the image of a past sensation tends to 
 call up the images of the anterior and posterior sensations 
 which were contiguous to it. Consequently, the abbreviatory 
 image of a long series of sensations, operations, and actions, 
 that is to say of a considerable fragment of my life, tends to 
 call up abbreviatory images of the anterior and posterior frag- 
 ments. But we have shown that the posterior sensation, 
 whether by itself or by its image, exerts on the image of the 
 preceding sensation a contradiction which comes to an end 
 when its commencement meets with the end of its antago- 
 nist, whence it happens that the repulsed image appears fast- 
 ened by its end to the commencement of the image or sensa- 
 tion repulsing it. Consequently, when the image of a past 
 sensation calls up the image of the posterior sensation and 
 the image of the anterior one, it is repulsed by the first, it re- 
 pulses the second, it connects itself by its end with the com- 
 mencement of the first, by its commencement with the end 
 of the second, and thus becomes fixed between the two. 
 Whenever the three images come in to override on another, 
 the two repulsions act in the manner indicated, the mechan- 
 ism which situates them acts so as to arrange them in a line, 
 as soon as the law of mutual evocation arouses them togeth- 
 er. They thus contract, with relation to one another, an ap-
 
 362 THE KNOWLEDGE OF MIND. [Boox III. 
 
 parent order which corresponds to the real order of the sen- 
 sations of which they are the remains. The contiguity of two 
 sensations, one preceding, the other following, the reciprocal 
 calling up of the image of the one by the image of the other, 
 the apparent joining of the two images, a joining such that, 
 while both appear as sensations, the first appears anterior to 
 the second : these are all the steps of the operation ; hence 
 we see that the real date of a sensation determines the appa- 
 rent date of its image. Here again, the agreement is estab- 
 lished by a correspondence. 
 
 As a general rule, not only does every precise and detailed 
 image presume an antecedent sensation, but every precise and 
 detailed image, which is joined, in appearance, to another pos- 
 terior one, presumes that the sensation whence it was derived 
 was joined in the same manner, but in reality, to the sensa- 
 tion which the other repeats. If its attachment, then, inva- 
 riably excites an illusion by compelling the other to appear 
 anterior, almost invariably does its origin the sensation pos- 
 terior to the sensation of which the other is the echo repair 
 this error. 
 
 Thus, the thread of our events is formed in our memory ; 
 at every moment we look back on a portion ; a day never 
 passes without our having frequently reverted back, and 
 sometimes far back in the chain, sometimes, by means of 
 abbreviatory processes, to events separated from the present 
 moment by many months and many years. Associations so 
 repeated are continually becoming more tenacious ; our past 
 is a line which we never weary of tracing over and refreshing 
 with ink. Classes become established among these events ; 
 they group themselves spontaneously according to their 
 resemblances and differences ; the most frequent, the acts of 
 walking, grasping with the hand, lifting a weight, feeling, 
 touching, smelling, tasting, seeing, hearing, recollecting, fore- 
 seeing, willing, are collected each under a name ; we conceive 
 them as possible to us, and these possibilities, incessantly 
 verified and limited by experience, constitute our powers or 
 faculties. There is no one of them whose presence, range, 
 and limits may not at any hour be manifested to us, so that 
 our idea is associated with the idea of self by links which are
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 363 
 
 hourly re-forged and strengthened. Add to the recollection 
 of my events and to the idea of my powers a last idea 
 similarly renewed and strengthened at every moment by 
 experience, that of the body which I call mine, and which 
 is distinguished by sharply divided characteristics from all 
 others, being the only one which answers to my touch by a 
 sensation of contact, the only one whose changes excite 
 sensations in me without an intermediate, the only one in 
 which my will is capable of exciting changes without an 
 intermediate, the only one in which the sensations I ascribe 
 to myself appear to be situated. All this group of true ideas 
 and exact recollections form a singularly solid network. It 
 requires, then, a great accumulation of forces to tear from it 
 any portion really belonging to it, or to insert in it any por 
 tion extrinsic to it. In fact, these transpositions are rare ; 
 they are principally met with when an organic change, like 
 sleep or hypnotism, loosens the meshes of the network, when 
 an inveterate, predominant passion, fortified by psychical or 
 sensorial hallucinations, at last wears away some thread of 
 the tissue, substitutes another thread, and, gaining step by 
 step, sets a fictitious web in the place of the natural web. 
 But, as woven under ordinary conditions, the web is good, 
 and its threads correspond, by their presence, by their di- 
 versities, by their apparent dates, by their connections, to 
 the presence, the diversities, the real dates, the connections 
 of the real facts ; this is because the real facts themselves 
 have woven it. The mind resembles a loom ; every event is 
 an impulse which sets it in action, and the fabric which issues 
 from it, transcribes by its structure the order and kind of 
 the impulses which the machine has received. 
 
 VIII. When, by the experiences of touch, of the educated 
 sight, and the other senses, we have acquired a sufficiently 
 precise and complete idea of our body, and there is associated 
 to this idea that of a within or subject, capable of sensations, 
 recollections, perceptions, volitions, and the rest, we make a 
 further step. Among the innumerable bodies surrounding us, 
 there are many which more or less resemble our own. In 
 other words, if we explore them, they excite in us sensations 
 of contact, resistance, temperature, color, and of tactile and
 
 364 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 visual shape and size, nearly analogous to those which we ex- 
 perience when we take cognizance by the eye and hand of 
 our own body. Thus the group of images by which we pic- 
 ture to ourselves these bodies is very similar to the group of 
 images by which we represent to ourselves our own. Conse- 
 quently, in accordance with the law of the association of im- 
 ages, when the first group rises in us, it must, like the other, 
 call up the idea of a subject or within, capable of sensations, 
 perceptions, volitions, and other similar operations. This is 
 the spontaneous suggestion or induction ; it is gradually con- 
 firmed and rendered precise by numerous verifications. In 
 the first place, we observe that this body moves, not always 
 in the same manner, in correspondence to a mechanical im- 
 pulse, but variously, without external impulsion, towards an 
 end, seemingly directed by a purpose, just as our own body 
 is moved and directed, which leads us to conjecture that in its 
 case there are intentions, preferences, motive ideas, a will, as 
 with us.* Secondly, and especially if it be an animal of a 
 higher species, we see it perform a number of actions analo- 
 gous to what we find in ourselves, such as crying, walking, 
 running, sleeping, drinking, eating, all of which leads us to im- 
 pute to it perceptions, ideas, recollections, emotions, desires, 
 similar to those of which these actions are in our cases the ef- 
 fects. Lastly, we put our conjectures to the proof. Having 
 recognized in our own cases the antecedents and consequents 
 of fear, pain, joy, and, in general, of some particular internal 
 state, we reproduce for it these antecedents, or prove in it 
 these consequents, and conclude that the internal and inter- 
 mediate state, which, visible in our cases, is invisible in its 
 case, must have been produced in its case as in our own. We 
 know that, in our cases, a blow with a stick is the antecedent of 
 a pain, and that a cry is the consequent of the pain. We 
 strike a dog, and at once hear it give a cry ; between this con- 
 
 * The child is angry with a balloon or tuft of down which floats about capri- 
 ciously, and will not allow him to seize it. In primitive times, men considered 
 the sun, the rivers, as animated beings. The savage takes a watch which ticks and 
 whose hands move, for a little round tortoise. A movement which appears spon- 
 taneous, invariably suggests the idea of a will, and especially if it appears to have 
 an object
 
 CHAP. I.] THE KNOWLEDGE OF MIND. 365 
 
 dition of pain and this sign of pain, both of which we clearly 
 perceive, we insert, by conjecture, a pain similar to what we 
 should ourselves have felt in such a case. Thanks to these 
 suggestions and these continual verifications, the outer world 
 which so far has been peopled with bodies only, is also peo- 
 pled with souls, and the solitary Ego conceives and affirms 
 around it a multitude of beings more or less similar to itself. 
 IX. All these cognitions are composed of the same ele- 
 ments joined together according to the same law. Whether it 
 be a question of a body, of ourselves, of another animated being, 
 whether the operation be termed external perception, act of 
 consciousness, recollection, induction, pure conception, our op- 
 eration is invariably a mass of which the molecules are sensa- 
 tions and images joined to images agglutinated into partial 
 groups which mutually call each other up. A couple is formed 
 by the aggregation of two molecules ; to this is attached 
 another couple, to these combined, others combined, and so 
 on, till at last the vast compound we term the idea of an indi- 
 vidual, the idea of this tree, of myself, of this dog, of Peter, or 
 of Paul, is established. Take an ivory billiard ball at two 
 paces distance. It excites in us a certain crude sensation of 
 the retina and the muscles of the eye, which calls up the im- 
 age of the muscular sensations of locomotion which would lead 
 our hand two. paces off, according to a certain outline ; the 
 compound is a patch of color with a certain shape, and situ- 
 ated in appearance two paces from us. We reach forward our 
 hand and feel the ball ; it produces in us a certain crude sen- 
 sation of cold, of even contact, of resistance, which calls up the 
 image of the tactile and visual sensations which we should 
 have if we were to look at or touch our right hand ; the com- 
 pound is a sensation of even contact, resistance, and cold, ap- 
 parently situated in our right hand. Now, whenever we have 
 repeated the experiment, each one of these two compounds has 
 always accompanied the other. Consequently, in any interval 
 of time, however long and however divided it may be, we can- 
 not imagine a moment in which, where one of the two com- 
 pounds is given, the other cannot and must not also be 
 given, so that the possibility and necessity of both last without 
 discontinuity, during all the moments of the interval ; this is
 
 366 THE KNOWLEDGE OF MIND. [BOOK III. 
 
 what we express by saying that there is in it something sta- 
 ble which is permanently tangible, resisting, and clothed with 
 color. To this compound so constructed are added the im- 
 ages of the distinct visual sensations, which the ball would ex- 
 cite in us, according to the differences of light and distance ; 
 from all these connected appearances, is formed the internal 
 semblance which now springs up in us in the presence of the 
 ball. Add two other compounds, the image of the sensations 
 by which we ascertain the changes which on certain condi- 
 tions the ball undergoes, and the image of the sensations by 
 which we ascertain the changes which the ball on certain con- 
 ditions excites in any other body. Such is the vast collection 
 of intellectual atoms joined one by one and group to group, 
 of which all the groups spring up, or are ready to spring up 
 within us, when the crude visual sensation of the white form 
 or the crude tactile sensation of smooth contact, cold, and re- 
 sistance, is produced in us. 
 
 Now let us suppose the sensation to cease, and all that 
 subsists of it to be the image with its appurtenances, that is 
 to say a representation of the ball, and let us assume that a 
 different sensation may rise at the same moment with its 
 special train. By this attachment of a contradictory sensa- 
 tion, the representation of the ball appears something internal, 
 a past event ; and, in this manner, it arouses other analogous 
 representations, in the midst of which it fixes itself in such a 
 way as to constitute with them a line of internal events ; this 
 line is opposed to other groups, because all its elements 
 present a constant character, which, being continually repeated, 
 seems persistent, that is to say, the particularity of being a 
 within, in opposition to the without ; and this, later on, will 
 offer to reflection and language the temptation to isolate it 
 under the name of subject and Ego. In this immense chain, 
 each class of internal events, sensations, perceptions, emotions, 
 each species of perceptions, of sensations, and emotions has 
 its image associated with that of its conditions and of its 
 internal and external effects ; and this forms an infinite 
 number of new couples, the two links of which draw one 
 another into the light ; so that we cannot imagine any pain 
 without imagining its condition a particular nervous lesion
 
 CHAP. I.J THE KNOWLEDGE OF MIND. 367 
 
 and without imagining its effect a contraction or a com- 
 plaint. Now, by a necessary suggestion, when an external 
 body presents the conditions and effects of our own, the 
 group of sensations which represent it calls up in us a group 
 of images analogous to those by which we represent to our- 
 selves our own events ; and this forms a last compound, the 
 most extensive of all, since it comprises a body and a soul, 
 with all their mutual connections and all the connections 
 which join their events to the events of others. Thus, in 
 our mind, every compound is a couple; the couple of a sen- 
 sation and an image; the couple of a sensation and of a 
 group, or many groups of images ; more complex couples, in 
 which a sensation, combined with its train of images, contra- 
 dicts a representation or group of images ; couples, still more 
 vast, in which a sensation, present with its train of images, 
 repulses into the past the abbreviatory images of a consider- 
 able fragment of our life ; couples, the most comprehensive 
 of all, in which, by still more summary abbreviations, the 
 sensation and images which represent to us all the properties 
 of a body call up the group of images which represent to us 
 all the properties of a soul. Each couple, if properly con- 
 structed, corresponds in our mind to a couple among events, 
 and each, when its first term is precisely repeated by the 
 present sensation, has, as its second term, a prevision. 
 
 What is the mechanism of this final operation, the most 
 closely allied to practice, and the most important of all, since 
 by its means we are enabled to act ? We foresee that the 
 sun will rise to-morrow, that it will describe a certain curve 
 in the sky, that it will set at such a spot, at such an hour, 
 and even, with the aid of science, that in so many years it 
 will undergo, at a particular moment, an eclipse of certain 
 extent. Here, as in recollection, an image appears projected 
 from the present ; only, instead of being projected backwards 
 on the line of time, it is projected forwards. When, this 
 evening, I foresee that the sun will rise to-morrow, what I 
 actually have in my mind is the more or less express repre- 
 sentation of the sun at daybreak, of a golden disc rising in 
 the eastern sky, of nearly horizontal rays which first illumin- 
 ate the tops of the hills, all this summed up in a word, in a
 
 368 THE KNOWLEDGE OF MIND. [BooK III. 
 
 reviving shred of visual sensation, in other words, in a present 
 image. This image appears as a future sensation, and fixes 
 itself by its anterior extremity on to the posterior extremity 
 of the sensation of obscurity which I have at present, which sit- 
 uates it in a determinate point of the line of the future. Here is 
 the crude fact ; to explain it, it is enough to refer to the opera- 
 tions of memory. There are two sensations which have never 
 failed to succeed one another in us ; on the one hand, the sensa- 
 tion of an obscurity of several hours ; on the other, that of a lu- 
 minous globe rising in the eastern boundary of the sky. How- 
 ever far we may reascend into the past, the first has never 
 been present to us without having been followed by the 
 second, nor the second without having been preceded by the 
 first. At whatever point of our past we may consider them, 
 we always find them joined to one another in this same order. 
 The constant repetition has created the tenacious habit which 
 has produced the energetic tendency, and henceforward, 
 when we represent to ourselves the couple, the first term 
 perforce appears to us as anterior to the second, and the 
 second as posterior to the first. Now, at this moment, the 
 first is a present sensation ; the second, then, must appear as 
 posterior to the present sensation, that is to say, as future. 
 In this manner, our prevision is the child of our memory. 
 When given a couple of recollections in which the second 
 term appears as posterior to the first, if the first is found to 
 be repeated by the present sensation, the second cannot fail 
 to appear as posterior to the present sensation, and to situate 
 itself by so much the more in advance and more distant with 
 relation to it, as there is a greater interval between the two 
 terms of the primitive couple. 
 
 All our previsions, and consequently all our conjectures, 
 are constructed in this manner. I wish to move my arm, 
 and I foresee that it will move ; I shake a bell, and foresee 
 that it will give a ringing sound ; I light a fire under the 
 boiler of a locomotive, and foresee that the steam disengaged 
 will move the piston ; I read and re-read attentively a piece 
 of poetry, and foresee that I shall presently be able to repeat 
 it by heart ; I address a question to my neighbor, and foresee 
 that he will answer me. In all these cases, two successive
 
 CHAP. I.] THE KNOWLEDGE OF MIA T D. 369 
 
 links, of the past, are, while preserving their reciprocal situa- 
 tion, transported out of their primitive position to -be placed, 
 the first in the present, the second at some point of the future, 
 because we have ascertained, or believe that we have ascer- 
 tained, a perfect resemblance between the first and our pres- 
 ent state. 
 
 Now, in fact, the majority of these previsions agree with 
 the events which are foreseen, and, in ordinary life, our ex- 
 pectation is scarcely ever mistaken. We do not perform an 
 act without reckoning beforehand on its effect, and this effect 
 scarcely ever fails to be produced. I have foreseen, before 
 performing them, all the movements I perform with my body 
 and limbs, and, a. hundred thousand times to one, they are 
 such as 1 have foreseen. I have foreseen, before experien- 
 cing them, the sensations of resistance, form, position, temper- 
 ature, \vhich will be given me by the somewhat familiar and 
 not too distant objects which I perceive by sight, and, a hun- 
 dred thousand times to one, they give me the sensation I have 
 foreseen. I foresee, before ascertaining them, the changes 
 which a particular modification of a certain ordinary body will 
 excite in some other ordinary body, and, a hundred thousand 
 times to one, these changes will take place exactly as I have 
 foreseen them. Drinking, eating, sleeping, walking, reading, 
 writing, speaking, singing, the carriage of the body, the exer- 
 cise of an art, a profession, a trade, no one of these common 
 actions is accomplished without the intervention of an innu- 
 merable multitude of necessarily correct expectations. The 
 intelligent being, animal or man, supplies its wants, preserves 
 its life, improves its condition, only by the exact accordance 
 of its present prevision and the near or even distant future. 
 If this harmony sometimes fails, it is on account of the ob- 
 jects or circumstances in question being such that anterior 
 observation has not furnished sufficient indications respecting 
 them. But, as to common objects, this disagreement is infre- 
 quent, and, if the preliminary experience has been sufficient- 
 ly extensive, it disappears entirely. There are, then, a prodi- 
 gious multitude of cases in which the event justifies the pre- 
 vision, and, in all these cases, the couple formed by our 
 thoughts is the exact counterpart of the couple formed by the 
 24
 
 TIIE KNOWLEDGE OF MIND. [BOOK III 
 
 facts. Consequently, the mental law which connects our two 
 thoughts is as general as the physical or moral law which con- 
 nects the two facts. 
 
 But it is not from the outset that we recognize it as gen- 
 eral ; primitively, it acts within us without our distinguishing 
 its character or measuring its range. The child and the ani- 
 mal foresee that this water will quench their thirst, that this 
 fire will burn them ; it is enough for this purpose that experi- 
 ence and custom have coupled in their minds a particular sen- 
 sation and a particular representation ; in their present cases, 
 the sight of water invariably excites the image of quenched 
 thirst, and the sight of fire invariably excites the image of 
 burning. There is nothing more than this ; what fills their 
 whole mind at the moment is a certain visual perception joined 
 to the image of a certain future sensation. So is it with the ma- 
 jority of our ordinary previsions ; the adult and reflecting man 
 is child and animal with respect to all his habitual and mechan- 
 ical actions, and this is sufficient for his conduct and practice. 
 But he is capable of outstepping this state, and, in fact, by 
 gradual degrees, he does outstep it. Not only is the mental 
 law within him, but he observes that it is within him. Not 
 only does he obey it, in the present case, but he ascertains 
 that it holds good for all cases, present, past, and future. By 
 means of signs, he extracts, denotes, and connects the two ab- 
 stract terms of water and of extinguished thirst, the two ab- 
 stract terms of fire and of burning. When this is effected, he 
 considers, by aid of a formula, their couple in itself, exclud- 
 ing all the particular cases in which they are met with. When 
 subjected to this operation, the couples which make up our 
 animal thought assume a new aspect, and, beneath the flow 
 of transient and complex events, we perceive the world of 
 fixed and simple laws.
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 
 
 BOOK IV. 
 
 THE KNOWLEDGE OF GENERAL THINGS. 
 
 CHAPTER I. 
 
 GENERAL CHARACTERS AND GENERAL IDEAS. 
 
 HITHERTO we have only considered particular things 1 , and 
 the knowledge we gain of them ; we have now to consider 
 general things, and the ideas we have of them. For there 
 are general things I mean thereby things common to many 
 instances or individuals ; these are characters or groups of 
 characters. Observe, for example, what is meant by the word 
 water, or the word drink ; water denotes a group of characters 
 which is met with alike in a number of liquids, in that of wells, 
 of rivers, of springs, of the sea ; drink denotes a group of char- 
 acters which is met with alike in a number of actions, in all 
 those by which a man or an animal causes a liquid to flow into 
 his mouth and stomach. So is it with the other words of 
 the dictionary ; each of them denotes a character or group of 
 characters which is or may be present in many natural cases or 
 individuals. Here we have a new object of knowledge. Just 
 as there are in our minds thoughts corresponding to particular 
 instances and individuals, so are there thoughts corresponding 
 to general characters. These we call general ideas. They 
 form in our minds couples, series, aggregates of various kinds, in 
 short a vast complex edifice. We shall now examine of what 
 elements this mental edifice is composed, how it is constructed, 
 how its equilibrium is maintained, and under what conditions 
 it corresponds to the real and natural edifice of things.
 
 372 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 I. GENERAL IDEAS WHICH ARE COPIES. 
 
 I. General characters play a great part in nature. In the 
 first place, strange as the paradox may appear, a general char- 
 acter is requisite to constitute an individual, a particular last- 
 ing thing. Whether it be a body or a mind, this stone or this 
 man, there is a character connecting its various successive 
 moments, a common character which we find alike in all of 
 them. In the case of the stone it is, at every moment and 
 during the whole duration of its existence, the possibility of 
 exciting in us the same sensations of contact, resistance, and 
 form, and of undergoing the same changes of position or struc- 
 ture under the same circumstances ; in short, the incessantly 
 renewed presence of the same sensible and physical characters. 
 In the case of the man, it is the constant possession of the 
 same aptitudes and the same inclinations, or, if the expression 
 is preferred, the continuous action of the same brain. This 
 we have already seen ; what lies at the foundation of the idea 
 of self is the idea of a within in opposition to a without, all 
 our events having this common character of appearing to us 
 as internal, in opposition to others which appear to us as ex- 
 ternal. So again, what lies at the foundation of the idea of 
 a particular body is the idea of certain invariably identical sen- 
 sations, which may under certain conditions be obtained at 
 any moment. In short, without pushing the analysis very 
 far, we perceive that existence is in its nature fragmentary, 
 perpetually repeated, made up of an indefinite number of 
 successive portions, just like the flame of a candle, which is 
 a series of ethereal vibrations, or the course of a stream, 
 which is a flow of continually renewed waters. In this im- 
 mense flow of events the world series which are sharply 
 divided from surrounding series, and whose elements are very- 
 similar to each other, form what we term particular and indi- 
 vidual beings. Each of these beings is a kind of distinct vor- 
 tex ; its continuous repetition resembles permanence : in fact 
 there is nothing permanent in it except its form, that is to say 
 the group of characters common to all its moments. But, from 
 the vanishing and the incessant diversity of all its constituent 
 events, the group of its fixed characters acquires a capital im-
 
 CHAP. I] GENERAL CHARACTERS AND GENERAL IDEAS. 373 
 
 portance, and we legitimately consider it as the essential por- 
 tion of the individual. 
 
 Let us now compare with one another a great number of 
 individuals. It is a remarkable fact that, in spite of the 
 separations of time and space, we find in an indefinite num- 
 ber of individuals, certain characters which are always the 
 same. Six thousand years ago, the plants and animals of 
 Egypt were similar to those of the present day ; there are 
 many kinds of plants and animals which have not varied 
 throughout the enormous intervals of geological periods; 
 from one end of the world to the other, at the present 
 time and in epochs separated from the present by myriads 
 of ages, the little mollusk whose shell forms chalk has 
 had the same structure and same existence. Nay more, 
 many of our chemical bodies, hydrogen, iron, sodium, and 
 others, are met with in the sun, thirty-five millions of 
 leagues from our earth, and beyond that again in stars so 
 remote that it takes several years for their light to reach us, 
 and that their distance escapes all our measurements. At 
 this prodigious distance the stars are, like the earth, subject 
 to gravitation : this is proved by the movements of double 
 stars. Their light is subject to the same conditions as that 
 of the bodies we burn ; this is proved by studying the rays 
 of the spectrum. Lastly, no scientific man has any doubt 
 that, in accordance with the laws of the conservation of 
 force, movement must have always existed and must exist 
 for ever. And so, just as there are common characters 
 whose continuous presence connects together the various 
 moments of the individual, so are there common characters 
 whose multiplied and repeated presence connects together 
 the various individuals of the class. These characters are 
 the uniform and fixed portion of dispersed and successive 
 existence, and this alone would suffice to show us the 
 interest we have in separating and seizing them. 
 
 But their importance appears still more clearly from 
 another characteristic. We do not arrange them merely 
 for the convenience of thought ; they are not simple means 
 of classification, instruments of technical memory. Not 
 only do they exist in fact, without us, and often far beyond
 
 374 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV- 
 
 the short range of our senses and our conjectures, but 
 more than this, they are effective. Each of them, by itself 
 and by itself alone, draws on with it another which is its 
 companion, its antecedent or its consequent, and so forms 
 a couple which we term a Law. Thus, in any animal 
 whatever, the presence of mammae implies that of vertebrae. 
 In every plant with two cotyledons, the arborescent bark is 
 formed of concentric layers. In all the layers of the 
 atmosphere which become chilled below a certain point, the 
 included vapor is precipitated as dew. Whenever two heavy 
 bodies are in the presence of one another, they attract each 
 other in the direct ratio of their mass and the inverse ratio 
 of the square of their distance. If the vapor of sodium be 
 burnt, its luminous spectrum presents a yellow ray at a de- 
 termined point. All these examples show us that general 
 characters are not only the most widely distributed inmates, 
 but also the most important agents of nature ; not only have 
 they the largest place, but the principal part and most decis- 
 ive activity in the field of being. 
 
 We must now observe that they are not all equally gen- 
 eral. Some are more so, others less ; each of them is by so 
 much the more general as it is less complex, and so much the 
 less complex as it is the more general. In fact, let us begin 
 by considering the group of characters which persists in a 
 particular being, in some man, through the successive mo- 
 ments of his life. This group is a very extensive one ; we 
 see this by the multitude of details we are compelled to give 
 when we attempt to describe a human person or soul. But 
 on the other hand, this group only corresponds with this 
 man, and lasts, like him, for a short interval of time only. 
 Pass now from the individual to the race ; the inverse hap- 
 pens ; here, no doubt, common characters are much more ex- 
 tended in space, and last much longer in time, since they are 
 met with in an indefinite number of contemporary individuals, 
 and are repeated through an indefinite number of successive 
 generations. But, on the other hand, they are themselves 
 less in number, since necessarily the whole of the characteris- 
 tics which distinguish each individual from the rest have been 
 left on one side, and since the general type obtained by this
 
 CHAI-. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 375 
 
 retrenchment is a remnant only. The same observation is 
 made on passing from the race or variety, that is to say from 
 the Negro or the Indo-European, to the species, that is to say to 
 Man. Continue and follow out the classifications of Natural 
 History, from the species to the genus, then to the family, 
 to the order, to the sub-kingdom, and to the kingdom. At 
 each step of the ladder, the type, impoverished on the one 
 hand, enriched on the other, loses some of its preceding 
 characters, and acquires new representatives; its elements 
 are more restrained, but its province is more extensive ; 
 its contents decrease, while its extension increases. For 
 instance, the species is less durable than the genus. A 
 particular species of animal, that of the megalosaurians, has 
 perished, after having existed during a geological period, and 
 the genus to which it belonged still subsists in other species 
 which have since arisen, or which have survived ; but the 
 characters of the genus are but a fragment of those of the 
 species, and the genus which survives in the modern saurians 
 presents a portion only of the characters of the species which 
 has disappeared. The rule is everywhere the same. If we 
 pass from organized and living matter to mineral and dead 
 matter, then to mechanical matter, we see the group of char- 
 acters common to various bodies reduce themselves, on the 
 one hand, till they consist of one or two qualities almost ab- 
 solutely simple, and become applicable, on the other, till they 
 include all bodies real or imaginable. Thus general charac- 
 ters arrange themselves in stages, one above the other, and in 
 proportion as their presence becomes more universal, their 
 contents decrease. At the lowest point is the momentary 
 fact, absolutely singular and distinct, which forms the element 
 of the rest ; every moment, action, state, or fact, is thus a 
 prodigiously complex datum, differing from every other, and 
 having its special shade of character. This shade of charac- 
 ter subtracted, there remains a cluster of characters common 
 to a whole series of facts, and whose persistence forms the in- 
 dividual. If from this cluster we omit all personal character- 
 istics, the remainder forms the race, that is to say a charac- 
 ter present in the individual and in many others. An extract 
 from this remainder is the genus, that is to say a character
 
 3 ?6 THE KNOWLEDGE OF GENEKAL THINGS. [BOOK IV. 
 
 present in many species ; and so on. By this series of sup- 
 pressions we pass, from a curtailed remainder, to a remainder 
 still more curtailed, and, at the same time, from a general 
 datum to a still more general datum. At all these stages, the 
 general character is an abstract character, and the more ab- 
 stract as it becomes more general, and the more general as it 
 becomes more abstract. 
 
 II. To these extracts or remnants, present at several points 
 of time and space, correspond within us thoughts of a dis- 
 tinct kind which we term general and abstract ideas. We 
 have already shown in what these ideas consist.* A general 
 and abstract idea is a name, nothing but a name, the signifi- 
 cant and comprehended name of a series of similar facts, or of 
 a class of similar individuals, usually accompanied by the sen- 
 sible, though vague, representation of some one of these facts 
 or individuals. The analysis is one of great delicacy, and we 
 have already performed it ; but in such a matter we cannot 
 accumulate too many examples, and I beg the reader will re- 
 peat the examination in his own case, choosing some very 
 striking idea which he has recently acquired. Here is one of 
 my own, whose commencement I clearly recall. Some years 
 ago I saw in England, in Kew Gardens, for the first time, 
 araucarias, and I walked along the beds looking at these strange 
 plants, with their rigid bark, and compact, short, scaly leaves, 
 of a sombre green, whose abrupt, rough, bristling form cut 
 in upon the fine softly lighted turf of the fresh grass-plat. If 
 I now inquire what this experience has left in me, I find, first, 
 the sensible representation of an araucaria; in fact, I have 
 been able to describe almost exactly the form and color of the 
 plant. But there is a difference between this representation 
 and the former sensations, of which it is the present echo. 
 The internal semblance, from which I have just made my de- 
 scription, is vague, and my past sensations were precise. For, 
 assuredly, each of the araucarias I saw, then excited in me a 
 distinct visual sensation ; there are no two absolutely similar 
 plants in nature ; I observed perhaps twenty or thirty arau- 
 carias ; without a doubt each one of them differed from the 
 
 * Part i. book i. ch. ii.
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 
 
 others in size, in girth, by the more or less obtuse angles of 
 its branches, by the more or less abrupt jutting out of its 
 scales, by the style of its texture ; consequently, my twenty 
 or thirty visual sensations were different. But no one of 
 these sensations has completely survived in its echo ; the 
 twenty or thirty revivals have blunted one another ; thus up- 
 set and agglutinated by their resemblance they are confound- 
 ed together, and my present representation is their residue 
 only. This is the product, or rather the fragment, which is 
 deposited in us, when we have gone through a series of simi- 
 lar facts or individuals. Of our numerous experiences there 
 remain on the following day four or five more or less distinct 
 recollections, which, obliterated themselves, leave behind in 
 us a simple colorless, vague representation, into which enter 
 as components various reviving sensations, in an utterly fee- 
 ble, incomplete, and abortive state. But this representation 
 is not the general and abstract idea. It is but its accompani- 
 ment, and, if I may say so, the ore from which it is extracted. 
 For the representation, though badly sketched, is a sketch, 
 the sensible sketch of a distinct individual ; in fact, if 
 I make it persist and dwell upon it, it repeats some special 
 visual sensation ; I see mentally some outline which corres- 
 ponds only to some particular araucaria, and therefore can- 
 not correspond to the whole class ; now my abstract idea 
 corresponds to the whole class ; it differs, then, from the 
 representation of an individual. Moreover, my abstract idea 
 is perfectly clear and determinate ; now that I possess it, I 
 never fail to recognize an araucaria among the various plants 
 I may be shown ; it differs, then, from the confused and float- 
 ing representation I have of some particular araucaria. 
 
 What is there, then, within me so clear and determinate 
 corresponding to the abstract character common to all arau- 
 carias, and corresponding to it alone ? A class-name, the 
 name araucaria, pronounced or mentally understood, that is 
 to say a Significant sound, which is comprehended, and is, in 
 this way, possessed of two properties. On the one hand, as 
 soon as it is perceived or imagined, it awakes in me the sen- 
 sible representation, more or less express, of an individual of 
 the class ; this attachment is exclusive ; it does not arouse in
 
 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 me the representation of an individual of another class. On 
 the other hand, as soon as I perceive or imagine an individ- 
 ual of the class, I imagine this sound itself, and am tempted 
 to pronounce it ; this attachment again is exclusive ; the real 
 or mental presence of an individual of another class does not 
 rouse it in my mind, and does not call it to my lips. By this 
 double attachment it becomes incorporated with all the per- 
 ceptions and sensible representations I have of the individuals 
 of the class, and is incorporated with them alone. But it is 
 not specially attached to any one of them ; it calls up all in- 
 differently ; it is called up indifferently by all. Therefore, if 
 they call it up, it is owing to what all have in common, and 
 not owing to what each has specially ; therefore, again, it is 
 attached to what all have in common and to that alone. Now 
 this something is precisely the abstract character, the same 
 for all the individuals of the class. It is, then, to this charac- 
 ter, and to this character alone, that the name, mentally heard 
 or pronounced, corresponds ; which we express by saying 
 that the name signifies and denotes the character. In this 
 way the name is equivalent to the sight, experience, or sen- 
 sible representation which we do not and cannot possess of 
 the abstract character present in all the similar individuals. 
 It replaces this character, and performs the same functions. 
 Thus we conceive the abstract characters of things by 
 means of abstract names which are our abstract ideas, and 
 the formation of our ideas is nothing more than the forma- 
 tion of names, which are substitutes. 
 
 How does a general and abstract name arise, and by what 
 mechanism does it contract this double exclusive attachment 
 to our sensible representations and special perceptions which 
 gives it its signification and value ? There is here, as we 
 have shown above, a single association of a certain class. We 
 point out a dog to a very little child, and tell him, in the lan- 
 guage of the nursery, imitating more or less happily the 
 barking of the animal, " That is a bow-wow" His eye follows 
 the indicating gesture ; he sees the dog, hears the sound, and, 
 after the apprenticeship of some repetitions, the two images, 
 that of the dog and that of the sound, are, in accordance with 
 the law of the association of images, permanently associated
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 379 
 
 in his mind. In other words, when he next sees the dog, he 
 imagines the sound, and even, by imitative instinct, makes 
 the sound, after some attempts. If the dog barks, he laughs 
 and is delighted, he has a double inducement to utter the 
 new and very striking animal noise of which he has as yet 
 heard a human imitation only. So far there is nothing orig- 
 inal or superior ; the brain of every mammal is capable of 
 similar associations ; a fox, when he seizes a rabbit certainly 
 imagines beforehand the sharp quick cry of the rabbit ; a 
 sporting dog, who hears the cry of a partridge, certainly im- 
 agines the visual form of the partridge in the air, and, as to the 
 instinctive reproduction of a sound when heard, there are the 
 well-known cases of parrots and other kinds of imitative an- 
 imals. 
 
 But there is this peculiar to man, the sound which has 
 become associated in his case with the perception of some 
 particular individual is called up again, not only at the sight 
 of absolutely similar individuals, but also by the presence 
 of individuals strikingly different, though in some respects 
 comprised in the same class. In other words, analogies which 
 do not strike animals, strike men. The child says bow-wow, 
 first to the house-dog, then, after a little, he says bow-wow 
 to the terriers, mastiffs, and Newfoundlands he sees in the 
 street. A little later, and he does what an animal never does, 
 says bow-wow to a pasteboard dog which barks when squeezed 
 then to a pasteboard dog which does not bark, but which 
 runs on wheels, then to the silent and motionless bronze dog 
 which ornaments the drawing-room, then to his little cousin 
 who runs about the room on all fours, then, at last, to a pic- 
 ture representing a dog. Under these last circumstances, I 
 saw a little boy two years old repeat the word bow-wow, some 
 forty or fifty consecutive times, with extraordinary wonder, 
 animation, and delight. He was held up to look at a shade 
 placed over a light, and ornamented with black figures of 
 dogs which were strongly illuminated. As the shade was 
 turned round, and each new figure appeared, he cried bow- 
 wow with an air of triumph ; it was the enthusiasm of dis- 
 covery ; and every day it was necessary to repeat it. I de- 
 termined to count his exclamations ; one evening, in less
 
 3 So THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 than three-quarters of an hour, he cried bow-wow fifty-three 
 times in succession, and his curiosity was never wearied. It 
 with the aid of philologists we observe the primitive mean- 
 ings of words in Latin, Greek, and German, and especially, 
 in Hebrew and Sanscrit, we find at their origin a wholly sim- 
 ilar operation :* a very loose analogy, that is to say a very 
 trifling resemblance between two facts, is sufficient for the 
 name given to the first to be applied to the second. At the 
 present day, too, our most important discoveries are made in 
 a similar manner. When Oken, coming across the skeleton 
 of a sheep, conceived the skull to be a compound of flattened 
 and consolidated vertebras ; when Goethe, observing petal- 
 loid stamens, conceived all the organs of a plant to be trans- 
 formed leaves ; when Newton, seeing an apple fall, conceived 
 the moon to be a heavy body also tending to fall to the earth, 
 they repeated the mental operation and experienced the de- 
 light of the little boy who saw the dogs on the lamp-shade 
 and cried out bow-wow. Between a vertebra and the skull, 
 between the green leaf and a pistil or stamen, between the 
 falling apple and the moon travelling through the sky, be- 
 tween the living barking dog*and the little figure on the lamp- 
 shade, the difference of appearance is enormous ; it seems 
 that the two representations differ all in all. And yet they 
 have a common characteristic ; thanks to this common pos- 
 session, the name called up by the first has also been called 
 up by the second, and henceforward corresponds to a very 
 general and very abstract character. All that distinguishes 
 man from the animal, intelligent races from those of limited 
 capacity, comprehensive and delicate from ordinary minds, is 
 reduced to this faculty of seizing more delicate analogies, to 
 this contagion, by which the name of an individual attaches 
 to a more different individual, to the property of more dis- 
 similar representations or perceptions to excite the same 
 name. For, the more rare are the points of resemblance, the 
 more individuals does the class contain ; the more individuals 
 does it contain, the more general and abstract is the charac- 
 
 * Renan, " De 1'Origine du Langage," pp. 125, 136. Max Muller, " The 
 Science of Language."
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 381 
 
 ter to which the idea, that is to say the name, corresponds ; 
 the more general and abstract is this character, the more 
 place does it occupy in nature and the more individuals does 
 it connect. The discovery of relations between very remote 
 objects, the detection of very delicate analogies, the extrac- 
 tion of common characteristics from very dissimilar objects, 
 the formation of very general ideas, the isolation of very ab- 
 stract qualities these expressions are all equivalent, and all 
 these operations are reduced to the calling up the same name 
 by perceptions or representations whose resemblances are 
 very slight, to the excitement of the sign by an almost imper- 
 ceptible stimulus, to the mental appearance of the word upon 
 a summons of the slightest nature, 
 
 By means of this aptitude, the child of fifteen months old 
 learns, in two or three years, the principal words of ordinary 
 familiar language. Observe the profound difference separa- 
 ting this acquisition and the parallel acquisition which a par- 
 rot might make. The infant invents and discovers incessantly, 
 and of its own accord ; there is no period of life in which his 
 intelligence is so creative. The names suggested to him by 
 his parents and the persons about him, are but starting points 
 for his innumerable efforts ; hence his joy and trouble. When 
 once a name he receives is associated in his mind with the 
 perception of an individual object, his mind acts as in the pre- 
 vious example ; he applies the name to the more or less simi- 
 lar objects which he recognizes as alike. This wholly sponta- 
 neous recognition appertains entirely to the child ; a parrot 
 does not apply the name which is taught him ; in a bird's 
 brain, it remains isolated ; in a child's brain, it becomes asso- 
 ciated to the presence of a general character, which hence- 
 forth has only to appear in order to call it up. This is what 
 the child does with words transmitted from significant words. 
 There is not even need on all occasions for the words to be 
 transmitted, with deliberate intention and by a human mouth ; 
 sometimes the child seizes them in the involuntary sounds he 
 utters, or in the accidental sounds he catches. "A member 
 of my own family," says Mr. Lieber,* " showed, in early in- 
 
 * " Smithsonian Contributions to Knowledge," vol. ii. p. 15.
 
 382 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 fancy, a peculiar tendency to form new words, partly from 
 sounds which the child caught, as to woh for to stop, from the 
 interjection woh, used by waggoners when they wish to stop 
 their horses ; partly from symphenomenal emissions of sounds. 
 Thus, when the boy was a little above a year old he had made 
 and established in the nursery the word nim for everything fit 
 to eat. I had watched the growth of this word. First, he 
 expressed his satisfaction at seeing his meal, when hungry, by 
 the natural humming sound, which we might express thus, 
 hm. Gradually, as his organs of speech became more skilful, 
 and repetition made the sound more familiar and clearer, 
 it changed into the more articulate um and im. Finally, an 
 n was placed before it, nim being much easier to pronounce 
 than im, when the mouth has been closed. But soon the 
 growing mind began to generalize, and nim came to signify 
 everything edible ; so that the boy would add the words good 
 or bad, which he had learned in the meantime. He now 
 would say good nim, bad nim, his nurse adopting the word 
 with him. On one occasion he said, fie nim, for bad, repulsive 
 to eat. There is no doubt but that a verb to nim, for to eat, 
 would have developed itself, had not the ripening mind 
 adopted the vernacular language, which was offered to it ready 
 made." The initiative of the infant is further shown by the 
 incorrect use it makes of our words by giving them a meaning 
 which they have not for us, and which it invents. The same 
 child had learned the words Good Boy, which he always pro- 
 nounced together, and which formed one word for him. " One 
 day, wishing to express the idea Good Cow, he said Goodboy 
 
 Cow Similarly a little girl said to a man, Doctor 
 
 naughty girl, because he had teased her." We may sum up 
 the whole apprenticeship of a child by saying that it receives 
 words, but creates their meanings, and that a series of contin- 
 uous rectifications are required in order that the meaning it 
 attributes to them may coincide with the meaning we attrib- 
 ute to them. 
 
 III. Suppose this process accomplished, and the infant ar- 
 rived at the threshold of adult life. Here begins a new se- 
 ries of re-arrangements, additions and corrections, an indefinite 
 series, carried on from generation to generation, and from
 
 CHAP. I.J GENERAL CHARACTERS AND GENERAL IDEAS. 383 
 
 people to people I mean scientific research. It is here a 
 question of making our general ideas correspond, no longer 
 with the general ideas of other people, but with the general 
 characters of things. As soon as we are seized with this de- 
 sire, a primary need declares itself ; there are blanks in our 
 ideas ; it is necessary to fill these blanks. For instance, the 
 notion an ordinary person has of the human body is very 
 meagre and incomplete ; he only knows it in the rough ; to 
 him it is a head, a trunk, a neck, four limbs, of certain color 
 and certain form that suffices him for practical purposes. 
 But it is clear that the characters special to the human body 
 are infinitely more numerous ; such a notion represents some 
 five or six only of the most obvious ones ; we must add to it 
 all those which prolonged and varied observation can discover. 
 The anatomist comes with the desire to see the details and 
 the interior; he dissects, notes, describes, and draws. The 
 text-book for beginners contains a thousand pages, and I can- 
 not tell how many charts and volumes would be required to 
 hold the figures and enumeration of all the parts which the 
 naked eye discovers. When the eye is aided by the micro- 
 scope, this number is multiplied a hundredfold. Lyonnet 
 did not find twenty years too much to describe the caterpil- 
 lar found in willow trees. Beyond our microscope, more pow- 
 erful instruments would further increase our knowledge ; it is 
 evident that in this direction there is no limit to the research. 
 So, again, take an inorganic body, water ; my idea of it is 
 that of an inodorous, colorless, transparent liquid, fit to drink, 
 which may become ice or steam ; nothing more ; this is all I 
 know of the enormous group of physical and chemical char- 
 acters or properties which accompany and constitute water. 
 Physicists and chemists come with their balances, their ther- 
 mometers, their electrical machines, their optical instruments, 
 their retorts, their reagents, and, in their hands the five or 
 six meshes which make up my idea become multiplied till 
 they form a vast net. But this net, however we may imag- 
 ine it enlarged, will never have as many meshes as there are 
 characters in the object to which it corresponds ; for the dis- 
 covery of a new body will always be sufficient to add a new 
 character to the object. At the beginning of the century, the
 
 384 THE KNOWLEDGE OF GENERAL THINGS, [BOOK IV. 
 
 discovery of potassium and sodium showed that, in contact 
 with certain metals, water was decomposed at the ordinary 
 temperature; here was a new character. If we had here the 
 unknown simple bodies which the rays of the spectrum now 
 indicate to us among the stars, and if we could submit water 
 to their action, it would most undoubtedly exhibit unknown 
 properties, which would have to be added to the list. Mean- 
 while, with every object, this list, fruitlessly lengthened, re- 
 mains still open ; and the idea we have of a species, a genus, 
 in short, of any list of general characters, never comprises, and 
 can never comprise, more than a limited fragment of their 
 unlimited chain. 
 
 Nevertheless, this addition of* new links is enough to in- 
 troduce considerable changes into our ideas. As furnished by 
 common experience, they were most frequently too wide or 
 too narrow ; scientific experience comes in to contract or ex- 
 tend them, to adjust their corrected dimensions to the real 
 dimensions of objects. Whilst the examination is made 
 roughly and only bears on the outer aspects of things, we 
 unite, under a single name and idea, fishes strictly so called 
 and the unicorn fish, the dolphin, the cachalot, the whale. 
 After a more minute and penetrating examination, we find 
 that this idea is too wide; there is no type corresponding to 
 it in nature ; the organs of circulation and respiration, the 
 skeleton and limbs, are not the same in fishes strictly so called 
 and in the unicorn fish, cachalot, dolphin, and whale ; these 
 last are mammals ; they must be taken from the class and 
 set apart ; when this operation is accomplished, my idea, re- 
 duced to proper limits, agrees with a natural group of charac- 
 ters actually connected and always met with in conjunction, 
 those of the fish. My idea of the mammal is correspondingly 
 enlarged ; it was too narrow as it only comprised terrestrial 
 animals with four legs, and giving suck ; I have added to it 
 the cetacea, which swim, and the cheiroptera, which fly ; 
 henceforward, being enlarged and proportioned to the exten- 
 sion of the type, it is applicable to all the species which pre- 
 sent the same group of characters, whatever be their differ- 
 ence of external appearance and habitation. 
 
 So it is in all the provinces of nature. As soon as pro-
 
 CHAP. I.] GENERAL CHARA CTERS AND GENERAL IDEAS. 385 
 
 found and prolonged analysis ascertains an ignored and im- 
 portant character in a species of objects, this species tends to 
 leave its compartment and to enter another. It was neces- 
 sary to burn the diamond to know that it was composed of 
 carbon : and it is merely within the last hundred years that 
 the formation of chemistry has enabled the classification of 
 inanimate bodies. Thanks to these processes, we have been 
 enabled, in each department of nature, to place beings in 
 more and more nearly natural classes, to arrange as in an 
 army, under companies, battalions, regiments, and divisions, 
 the enormous multitude of individuals, all animal forms, all 
 vegetable forms, the hundred and twenty thousand species 
 of plants, two hundred and sixty thousand species of animals, 
 and, in the majority of cases, to determine the real and con- 
 stant type which constitutes each species, each genus, each 
 family-, each order, each sub-kingdom. We have not invari- 
 ably succeeded in this ; many of our divisions remain artifi- 
 cial, and are convenient only ; others, provisional ones, await 
 further researches to become definitive.* In mineralogy, 
 especially, there is as yet no real classification. But for the 
 majority of the species and genera of animals and plants, for 
 the vegetable families of Jussieu, for the orders and three 
 higher sub-kingdoms of Cuvier, the acquired general idea 
 corresponds with an actually general thing, that is to say 
 with a group of characters which involve or tend to involve 
 one other, whatever be the individuals and circumstances 
 under which one of them is given. 
 
 IV. At present, in addition to these general characters, 
 there are others still more general, which appertain to the 
 elements of the classified individuals, and which, spread uni- 
 versally under various disguisements, are, through their as- 
 cendancy, the regulators of the rest. Hence it follows that 
 of all general ideas, those corresponding to such characters 
 are by far the most valuable. We attain these characters, 
 like the rest, by taking a general type already known, and by 
 gradually removing from it a number of accessory characters 
 
 * For instance, the sub-kingdom of zoophytes, the class of infusoria and that 
 of entozoa. 
 
 25
 
 386 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 so as to preserve only the most stable and most universal. The 
 idea of the leaf in botany is of this kind.* It is now known 
 that the various organs of a plant are nothing more than 
 transformed leaves. Developed in spirals on the stem, they 
 are drawn together at the summit in superposed horizontal 
 verticils, whose various stages are the various parts of the 
 flower. The impoverishment of the final vegetation has 
 drawn them together, and other circumstances have consoli- 
 dated and deformed them. Sometimes, one among them has 
 become abortive ; sometimes, two or more of them have be- 
 come monstrous. But the original type is manifested by fixed 
 relations, by sudden reversions, by a thousand incontestible 
 characteristics ; and the idea of the leaf, disengaged from all 
 sensible impressions, purified, drawn by energetic abstraction 
 far away from common experience, is nothing more than the 
 almost geometrical idea of a cycle of vegetable elements, 
 which preserve their primordial order under all imaginable 
 forms and in all imaginable functions. And so, in animals, 
 through all the diversities of structure and function, we find 
 throughout the whole class of mammalia the same type of 
 skeleton, throughout the whole class of Crustacea, as through- 
 out the whole class of insects, the same type of segments, 
 of mouth, and limbs ; and this type is so tenacious that, in 
 many species, we find, to evidence its presence, the subsist- 
 ence or appearance of useless parts or dispositions ; a suture, 
 a set of teeth, a nail, a bony excrescence, transient or rudi- 
 mentary organs render it visible by presenting its transitory 
 memorial or surviving remnant. 
 
 Other still more general characters or groups of charac- 
 ters are met with under the name of chemical and physical 
 properties of bodies, not only in the living, but also in the 
 inorganic world. Here again, the process which forms the 
 corresponding idea is the same. Vulgar experience has dis- 
 covered some property of a body for instance, the power of 
 amber to attract to it small and very light objects. Multi- 
 plied and precise experience multiplies and renders precise 
 the circumstances and instances of this attraction. By de- 
 
 * Auguste Saint-Hilaire, " Morphologic vegetale," pp. 10, et seq.
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 38? 
 
 grees, we let slip these variable characters to seize only on 
 its fixed characters. We thus isolate a universal mode of 
 action, that is, electric action, one determinate, purified, ex- 
 tended idea coincides with a force which operates or may 
 operate in all bodies. And so again, before the researches 
 of the scientific men of the Renaissance, our idea of a heavy 
 body was that of a body tending downwards, and impressing 
 on us, when lifted, a sensation of muscular effort. In propor- 
 tion to our discoveries this idea becomes more abstract. In 
 the first place, it is not necessary that such bodies should 
 afford a sensation of resistance to the hand lifting them ; for 
 the air which sustains the mercury in the barometer is heavy. 
 Further, it is not only in a downward direction that bodies 
 fall ; for, the earth being round, they fall at the antipodes in 
 a different direction from what they do with us. Thus, all 
 within our atmosphere falls, and falls toward the centre of 
 our planet. But, for a body to fall, it is not necessary that 
 it should be comprised in our atmosphere ; of the two move- 
 ments which make up the whole movement of the moon, one 
 is a fall towards us. With two further steps, the purifica- 
 tion of our idea is accomplished. It is not only bodies 
 disposed about the earth which tend to fall to it : all the 
 bodies of our solar system tend to fall towards one another. 
 It is not only the huge heavenly masses which attract each 
 other mutually ; all their molecules, the most distant and the 
 most nearly approaching, attract each other mutually accord- 
 ing to the same law, in the direct ratio of their mass and the 
 inverse ratio of the square of their distance. Gravity, thus 
 defined, is a character so persistent as to appear indestructi- 
 ble ; each body preserves its own, always equal and intact, 
 through all the changes of state we can make it undergo, and 
 in all the chemical combinations into which it can possibly 
 enter. 
 
 Such is the progress by which our general ideas are formed 
 and adjusted to general things. These ideas pass through two 
 states. First the idea rises with the sign ; then it is gradu- 
 ally rectified. In fact, as we find it in current language, and 
 as vulgar experience furnishes it, it corresponds imperfectly to 
 its object. On the one hand, it is incomplete and vague ; in
 
 388 THE KNOWLEDGE OF GENERAL THINGS. [Boon IV. 
 
 other words, the general characters which it denotes are 
 neither precise enough nor numerous enough. By more at- 
 tentive observation and more varied experience, we determine 
 the ascertained characters, and add on to them a row of new 
 characters. On the other hand it is not sufficiently purified 
 and abstract ; in other words, among the characters it de- 
 notes, there are accessory and accidental ones amalgamated 
 with those which are important and fixed. By extended ex- 
 perience and multiplied comparison, we expel the parasitical 
 and transient characters, so as to preserve those only which 
 are intrinsic and stable. Our idea has become adapted to its 
 object, first by addition, then by subtraction. 
 
 II. GENERAL IDEAS WHICH ARE MODELS. 
 
 I. Another class of general ideas presents other character- 
 istics and is formed by another process. These are the ideas 
 which compose arithmetic, geometry, mechanics, and in gen- 
 eral, all sciences treating, like mathematics, of the possible 
 and not of the real. We form these ideas without examining 
 whether there are in nature objects which correspond to them, 
 and for this we construct them. 
 
 Let us follow the detail of this- construction, and see with 
 what elements we fabricate these new ideas. The most sim- 
 ple of all are those of arithmetic, which have numbers for their 
 objects. Now we all know that every number is formed by 
 unity added to itself; it is the notion of unity, then, which 
 we shall first examine. It comprises nothing mysterious, and 
 its origin has nothing strange in it. We are not dealing here 
 with the absolute and metaphysical unity which consists in 
 the property of being indivisible, or rather, without parts, and 
 which would be possessed, for example, by one of Leibnitz's 
 monads. We deal simply with an office which any object 
 whatever may fulfil, with the function it performs, with the 
 part it plays, in contributing with others like it to form a col- 
 lection. It is in this aspect alone that we consider it ; there- 
 fore, twenty heaps of stones by a roadside are, in this sense, 
 twenty units as much as twenty monads. The unity of each 
 heap is nothing more than its aptitude for entering as a factor
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 389 
 
 into the total of twenty heaps, and into any other analogous 
 total, greater or smaller. Consequently it is, like every ap- 
 titude, property, and capacity, nothing more than a general 
 character of the object, and this character may be disengaged, 
 extracted, and set apart by ordinary processes, that is to say 
 by means of a name, and, in general, by means of a sign. 
 Moreover, there is no character more easy to set apart ; for 
 all objects and all events present it, since every object and 
 every event contributes with other similar ones to form a col- 
 lection which is its class. The materials, then, from which the 
 notion of unity may be extracted exists in superabundance, 
 and the first step of arithmetic may be made in all regions. 
 Let us, then, observe a series of objects or events, taking 
 care to consider in each of them its capacity only to enter as 
 a component in a collection. For this, let us purposely omit 
 all its other characters ; after this retrenchment, a row of 
 poplars, a series of sounds, any other series or row, ceases to 
 be a row of poplars, a series of sounds, a series or row of de- 
 terminate objects or events ; it is nothing more than a se- 
 quence, row or series of ones or units. Now in this point of 
 view, all ones are the same one, and all series of ones are the 
 same series ; for the characters which distinguish individuals 
 from one another, and series from one another, having been 
 excluded, the individuals can no longer be distinguished from 
 one another, and the series can no longer be distinguished from 
 one another. Here, then, we have an abstract series com- 
 posed of abstract units. To observe this series more conve- 
 niently, men have substituted for it a sensible series of very 
 manageable objects, sometimes of little pebbles, sometimes 
 the ten fingers of the two hands.* Nothing is easier than to 
 raise, successively, one by one, the fingers of the closed hand, 
 or to lower, successively, one by one, the fingers of the open 
 hand. Nothing is easier than to add pebbles, one by one, in 
 such a way as to make a heap, or to take away pebbles, one 
 ty one, in such a way as to unmake the heap. And as, by 
 
 * Calculation is derived from calculus, a little pebble. The Roman numerals 
 I, II, III, V, X, are rude drawings representing one or many fingers, one or both 
 hands. Our system of numeration by tens was originated by the fact of our hav- 
 ing ten fingers.
 
 3QO THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 taking away or adding one or more pebbles, by raising or 
 lowering one or more fingers, we can visibly alter the total of 
 the collected pebbles or of the lifted fingers, it is easy, not 
 only to fabricate in this way various visible totals, but also to 
 observe with our eyes how these totals are made and unmade.* 
 We make them progressively, as to pebbles, by adding a peb- 
 ble to the first pebble and so on, as to the fingers by raising a 
 finger in addition to the first finger, and so on. We unmake 
 them progressively, as to pebbles, by removing a first pebble 
 and so on, as to the fingers by lowering a first finger and so 
 on. These are the primitive substitutes ; each finger or 
 pebble visibly replaces an abstract unit : the different groups 
 of visible fingers or pebbles replace the different groups of 
 abstract units, and, in proportion as a visible finger or pebble 
 is added to the group of visible fingers or pebbles, a pure unit 
 is added to the group of pure units. 
 
 At present, in the place of these already convenient sub- 
 stitutes, we substitute other still more manageable ones, the 
 various sounds which constitute our names of number. For 
 a lifted finger, we say one, for two fingers lifted, two, for 
 three fingers lifted, three, and so on up to ten. In this way, 
 the name one replaces a lifted finger, and therefore an abstract 
 unit. So, again, each one of the following names replaces a 
 group of lifted fingers, and therefore a group of abstract units. 
 So, finally, when we pass from a name of number to the fol- 
 lowing name, a finger is lifted to add to the preceding group 
 of lifted fingers, an abstract unit is added to the preceding 
 group of abstract units, and the name of number expressed 
 replaces the group of units which replaced the preceding one, 
 together with an additional unit. In other words, each name 
 of number is equivalent to the group denoted by the preced- 
 ing one, with the addition of one.f So as not to encumber 
 
 * See the very elegant and very delicate analysis of this mental process in 
 Condillac's " Langue des Calculs." 
 
 f A to the primitive meaning of our nouns of number see Bopp, " Compara- 
 tive Grammar" (tr. Breal) ii. 221. Tri (three) means " exceeding" i. e., the two 
 i, f :nor numr>?r. . our probably means, three plus one ; five, four plus one ; ten, 
 twice five. A hundred certainly means, ten times ten. A thousand probably 
 means, many, a great number.
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 39! 
 
 our memory, we reduce these names to what is strictly neces- 
 sary. When we get beyond ten, we say eleven, twelve,* 
 thirteen,! and so on, till we get to nineteen. After nineteen, 
 as the following number is equivalent to twice ten, well-con- 
 structed languages revert to the word two, modifying it suit- 
 ably, and similarly modifying the names of the following num- 
 bers, so as to make them express three times ten, four times 
 ten, and the sequence of decades up to ten times ten. The 
 decades thus form units of a second order, capable, like sim- 
 ple units, of being counted up to ten. Arrived here, we give 
 their total the name of hundred, and this new total forms a 
 unit of the third order, capable in its turn of being repeated 
 up to ten hundred, or a thousand, a unit of the fourth order. 
 The previous operation, repeated on this new unit, leads us 
 up to ten thousand, thence to a hundred thousand, thence to 
 a million, and so on, so that with eleven names, arranged in a 
 certain order, we can represent precisely an enormous group, 
 such for instance as the collection of two million, three hundred 
 and twenty-seven thousand, six hundred and forty-eight units. 
 An expression like this is a very abbreviatory substitute ; 
 for it may be pronounced in less than a second ; nothing 
 shorter has been found in the matter of sounds. But, when 
 written for the eyes, it occupies a line and a half, and requires 
 sixty-seven characters ; this is a great deal, and, in this re- 
 spect, it may be improved. For written names, we substitute 
 more simple characters, which, instead of replacing nouns of 
 number directly, and numbers themselves indirectly, replace 
 numbers directly. These characters are called ciphers ; it is 
 arranged that a cipher placed to the left of another denotes 
 units of an immediately higher order, that is to say, ten times 
 as great ; we compose a list of nine distinct ciphers to rep- 
 resent the nine first numbers ; we add to this list a zero to 
 represent the absence of unity or number, and then, instead 
 of sixty-seven characters, we need employ seven only to rep- 
 resent a collection of 2,327,648 units. 
 
 * In Latin, undecim, duodecim. 
 
 f In Latin, tredecim. In German, zwo'lf, dreizehn, derived from zwei, drei. 
 p In German, Zwanzig. In Latin, triginta, quadraginta, quinquaginta, etc. 
 In old French, septante, octante, nonante.
 
 3Q2 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Thanks to these abbreviatory notations, we construct a 
 prodigious quantity of compounds which are numbers. For 
 this, it is enough to arrange the ciphers or to utter the 
 names, recollecting the meanings which our convention has 
 imposed on them. Let us now observe the characters of 
 the idea so constructed. When we read and understand one 
 of these groups of signs, for instance, 2,327,648, we do not 
 consider whether nature furnishes an object corresponding 
 to our idea. Is there anywhere a group of real units to 
 which this collection of mental units is, feature for feature, 
 adapted ? This is a question we set aside ; we pay no heed 
 to it ; our idea has been constructed for its own sake. And 
 yet there is a possibility of this mental construction coinciding 
 with some real construction. For to the elements of which 
 my idea is constructed, there correspond elements included 
 in things. In fact, what I call unity, is the aptitude to enter 
 into a collection. Now there is no natural individual or actual 
 event which may not so enter; whether it be a body or a 
 mind, an external or internal modification, as soon as we 
 perceive a fact or thing, we put it in its class, that is to 'say 
 with others similar to it ; moreover, as soon as the object is 
 conceived by us, it spontaneously calls up in us, without our 
 desiring it, and solely by the law of association of ideas, other 
 more or less similar objects. Together they form a group of 
 more or less similar data, each of them having the character 
 of being a distinct datum among many other analogous ones. 
 In this manner, and in this narrow sense, it is a unit among 
 many other units. There are, then, collections of units in 
 nature, as there are collections of units in the mind. In fact, 
 there are a certain number of planets about the sun. There 
 are, at this moment, a certain number of men, animals, and 
 plants, living on the earth. During this year, the earth or 
 any other planet, has advanced a certain number of kilometres 
 in its orbit. During this year, a certain number of persons 
 have died in France. Whilst my mind performs its additions 
 and subtractions, nature performs hers. I fabricate in ad- 
 vance a long series of distinct moulds, arranged according to 
 their increasing dimensions ; nature fabricates, or has fabrica- 
 ted with her various clays all that is required to fill them ;
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS, 393 
 
 and the thing contained is adjusted to what contains it, 
 first, because the mental elements of the one were fashioned 
 upon the real elements of the other, next, because the arti- 
 ficial structure of the containing thing happens to correspond 
 with the natural structure of the thing contained. 
 
 II. This is the character common to all the ideas we 
 construct; they are preliminary outlines; when we form one 
 of them, we have no real thing in view to which we attempt 
 to make our thought conform ; and nevertheless, our thought 
 is found to conform to one or more real things as yet unknown, 
 which, when known, will manifest this conformity. 
 
 Not that the adaptation is always exact ; there are cases 
 in which it is approximate only. Of this kind are geometrical 
 ideas. Let us first search for the elements with which we 
 construct them ; we all know that they are few in number, 
 and we readily see from what experiences we extract them. 
 Take any body observed by the senses, this stone, this 
 piece of wood. It has, as limit, one or more outer parts 
 enclosing its inner part ; and these outer parts by which it 
 terminates are its surfaces. But each of these surfaces is 
 itself terminated by one or more limits which are called lines, 
 and each of these lines is itself terminated by two limits which 
 are called points. So far there is no difficulty ; each of these 
 limits, surface, line, or point is a character of the body, a 
 character isolated by abstraction, considered apart, and, more- 
 over, general, that is to say common to many bodies, or 
 rather, universal, that is to say common to all bodies. We 
 detach this character and denote it by means of symbols, 
 which are sometimes the names of surface, line, and point, 
 sometimes a class of sensible objects, very manageable, and 
 selected to take the place of all the rest, the real surface of a 
 black board or white paper, the slender trace left on the 
 paper or board by a stroke of ink or chalk, the little dot left by 
 the momentary touch of the pen or chalk. The dot being very 
 small we are disposed to pay no attention to its length and 
 breadth, though real ; by this omission we involuntarily make 
 abstraction of them, and have no difficulty in treating the 
 dot as a point. The trace being very thin, we are not dis- 
 posed to trouble ourselves about its breadth, though real ;
 
 394 
 
 THE KNOWLEDGE OF GENERAL THINGS. BOOK IV. 
 
 by this omission we cut it away, and come, without difficulty, 
 to consider the stroke as a line. The board and the paper 
 being very flat, and level to the eye and hand, we experience 
 no sensation to remind us of their thickness ; by this omission 
 we suppress it, and are led to consider the board and paper 
 as true surfaces. In this way the board, the narrow stroke, 
 the little spot of chalk, become convenient substitutes. They 
 are sensible and special things, but they replace wholly 
 abstract and general limits, in the same way as, just now, in 
 arithmetic, pebbles and fingers replaced pure units. 
 
 To these elements so represented, add another movement ; 
 it is also met with in the majority of bodies we perceive ; we 
 are, then, capable of detaching it from them. When once 
 these data are extracted, it is sufficient to combine them in 
 different ways to obtain all geometrical compounds. In ad- 
 dition to this, by a still further reduction, we find that the 
 point and movement are sufficient elements for the reconstruc- 
 tion of the two other kinds of limits which we have termed 
 the line and surface, and further, of the solid body, from 
 which we have drawn, with the ideas of surface and line, those 
 of point and movement. In fact, imagine a point, that is to 
 say the limit of a line, and assume that it moves ; the con- 
 tinuous series of positions it occupies forms a line. Assume 
 this line to move ; the continuous series of the positions it 
 occupies forms a surface. Assume this surface to move ; the 
 continuous series of the positions it occupies forms a solid 
 body, at least, in a geometrical point of view. And the substi- 
 tutes we have adopted for the point, line, and surface, render 
 this construction sensible to us. By prolonging this little dot 
 of chalk, we see a slender trace produced. By causing this 
 whole trace to move in a mass, we see a greater or less surface 
 produced. By mentally causing the surface of the board to 
 recede, we see the whole solid board produced. From this 
 general construction, let us pass to special ones. Let there 
 be two points ; if the first moves towards the second, and 
 towards the second only, the line it describes is straight. If, 
 during an appreciable fragment of its movement, it moves 
 towards the second point, and then, during other equally ap- 
 preciable fractions, towards a third, a fourth, etc., the line it
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 395 
 
 describes is broken, or composed of distinct straight lines. If 
 at each instant of its movement it moves towards a different 
 point, the line it describes is curved. Such are the different 
 species of lines. Next, if two straight lines start from the 
 same point, and move, each towards a different point, they di- 
 verge from one another, and this greater or less divergence is 
 called an angle. If the two angles which the second line 
 makes to left and right with the first are equal, they are called 
 right angles, and we say that the second line is perpendicular 
 to the first. Such are angles. With straight lines cutting 
 each other in pairs, and forming certain angles, we construct 
 all triangles, all quadrilaterals, and generally, all polygons. 
 If we submit a curve to the condition of having all its points 
 at an equal distance from some other anterior point, we have 
 circumference. " The plane surface, or plane, is generated by 
 a straight line perpendicular to another, and turning about it 
 while always passing through some one point in it."* With 
 planes terminated by certain polygons and forming certain 
 angles by their mutual inclination, we construct all poiyhedra. 
 By the revolution of the semicircle about its diameter, of 
 the rectangle about one of its sides, of the right angled tri- 
 angle about one of the sides containing the right angle, we 
 form the sphere, the cylinder, the cone ; by sections of the 
 cone, we form the ellipse, parabola, and hyperbola ; by vari- 
 ous combinations of the primitive elements, and of these first 
 compounds, we form all possible species of lines, surfaces, and 
 solids, sometimes so complex that imagination cannot form 
 them, and that, if nature or art were to furnish instances of 
 them, the most attentive eye could not contrive precisely to 
 distinguish all their characters. 
 
 Are there in nature physical constructions conforming to 
 these mental constructions ? And first, are there in nature 
 surfaces, lines and points ? Yes, certainly, at least as far as 
 our senses are concerned ; for, to our senses, a body has sur- 
 faces which are the limits in which it appears to be contained, 
 a surface has its lines which are the limits by which it seems 
 circumscribed, a line has its points which are the limits by 
 
 * Duhamel, " De la Methode dans les sciences de raisonnement," 2iue partie, 12.
 
 396 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 which it seems to be terminated, or by which we may inter- 
 rupt it. Are there in nature surfaces, lines, and points which 
 move ? Yes, since bodies move and their limits accompany 
 them in their movement. Next, are there in nature points, 
 lines, and surfaces, which, in their motions and combinations, 
 rigorously conform to the conditions enunciated in our con- 
 structions ? In other words, are there perfect straight lines, 
 right angles, squares, circles, planes, polyhedra, round bodies ? 
 As far as we can judge, nature does not furnish us with 
 such. When we arm our eye with a powerful microscope, we 
 find inflections in what seem the straightest lines, roughness 
 in the smoothest planes, irregularities 'in the most regular 
 forms. A cannon-ball appears to advance in a straight line ; 
 theory shows us that it begins to fall the moment it leaves the 
 cannon. The planets seem to describe an ellipse ; observa- 
 tion and the calculations of their perturbations prove that this 
 ellipse is not exact. In short, when we compare the work of 
 nature and the work of the mind, we prove that their conform- 
 ity is not entire ; the first approximates to the second ; that 
 is all. Usually, this coincidence is remote enough, but, even 
 in the most favorable instances, it fails in some point ; we 
 might say that the real substance attempts to mould itself on 
 the mental form, but that the imperfection of its material hin- 
 ders it from copying rigorously the prescribed shape. 
 
 There is a reason for this impotence ; and, if we take 
 cases whose theory is constructed, we are able to explain it. 
 The cannon-ball would advance continuously in a straight 
 line, if gravity did not cause it to descend towards the ground. 
 The planet would describe a perfect ellipse, if the variable 
 proximity of the other planetary bodies did not intervene to 
 alter the regularity of its curve. If the ball deviates from its 
 straight line and the planet from its ellipse, it is through 
 other perturbing directions being added to the simple direc- 
 tion followed by the ball, to the two simple directions accord- 
 ing to which the planet travels. Consequently, if the real con- 
 struction is but approximately adjusted to the mental con- 
 struction, it is owing to the first being more complex and the 
 second simpler. Disencumbered of its accessory elements, 
 and reduced to its principal elements, the first would pre-
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 30,7 
 
 cisely copy the second ; and in fact, it does approximate to 
 it in proportion as its ulterior or accessory elements become 
 feeble, and leave greater ascendancy to its primitive or prin- 
 cipal element. Thus, in geometry, as just now in arithmetic, 
 our preliminary outlines have a function and a value. Though 
 constructed on their own accounts, they have a relation with 
 things. In a certain sense they are exact, and, with a com- 
 plementary operation, they may become so. The divergence 
 we observe between them and the facts may disappear, and 
 does in fact disappear in two ways. We have seen it disap- 
 pear by an abstraction, that is to say by the mental omission 
 of certain elements of the facts ; in this way, the reduced 
 facts are adjusted to the outlines. It may also disappear by 
 an inverse process, that is to say by the introduction into the 
 outlines of the elements omitted in their preliminary con- 
 struction ; to the consideration of the principal or primitive 
 directions, we add those of the perturbing directions, whether 
 ulterior or accessory, and, in this way, the completed outlines 
 will be adjusted to the facts. 
 
 III. Other elements, fashioned like the preceding ones on 
 the general characters of natural objects, combine with the 
 preceding ones to form new outlines. We may consider 
 movement, not only as having the effect of describing a line, 
 but in itself. Daily, beneath our eyes, a prodigious quantity 
 of bodies are at rest or in motion, so that in this point of 
 view experience furnishes us with all the materials necessary 
 to enable us to isolate the two elementary ideas of rest and 
 motion. 
 
 Take a body in motion ; it passes from one point to an- 
 other while describing a line ; we have many occasions of ob- 
 serving that, according to circumstances, this same line is de- 
 scribed in more or less time, and we thence draw a new ele- 
 mentary idea, that of velocity. Take a body passing from 
 rest to motion ; in the majority of cases, we discover that 
 something has been altered in it or in its surroundings, and 
 after a certain number of experiences we ascertain, or believe 
 that we ascertain, that this internal or external alteration is 
 always followed by the movement of the body. Whatever 
 be this condition of motion, the import of another body, the
 
 398 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 attraction of a magnet, electric repulsion, whether it appear 
 to reside in the moved body or in another, is of no impor- 
 tance ; we call it force, without forming any previous conclu- 
 sion as to its nature, and we mean nothing more by this name 
 than a condition whose presence is sufficient to excite the 
 motion, a condition which is met with in an infinite number 
 of various circumstances, and which, when detached and iso- 
 lated by a mental fiction, thus becomes wholly general and 
 abstract. In this state of purity, it is defined only by its re- 
 lation with the movement it excites. Therefore, if in the 
 movement it excites we find a character susceptible of magni- 
 tude, the force will be susceptible of magnitude ; now, we 
 have just seen that this character is velocity. In this man- 
 ner, we speak of a force as double or triple another ; and we 
 thereby mean nothing more than a condition whose pres- 
 ence is enough to excite in the same body, surrounded by 
 the same circumstances, a movement, twice, thrice, four, etc., 
 times as rapid as the first. 
 
 When this is settled, we can take a step in advance. 
 Among the bodies we examine, there are some which appear 
 to us homogeneous, that is to say composed of particles all 
 of which are perfectly similar, except in the difference of their 
 position in the body ; such, for instance, is a measure of pure 
 water, a piece of refined gold. From this indication of ex- 
 perience, we have no difficulty in conceiving an absolutely 
 homogeneous movable body, analogous to a pure geometrical 
 solid, divisible therefore into two halves, each composed of 
 the same number of exactly similar particles. Now, take a 
 force which impresses a certain velocity on the block formed 
 by the half of these particles ; as, by definition, these two 
 halves are absolutely similar and may be substituted without 
 inconvenience for one another, it will require a force abso- 
 lutely similar and capable of being substituted without incon- 
 venience for the other, that is to say, in short, an equal force, 
 to impress the same velocity on the block formed by the 
 other half, consequently two forces, each equal to the first, 
 that is to say a double force, to impress the same velocity 
 on the block formed by the two halves. Thus arises our last 
 elementary notion, that of mass, which is found to be a quan-
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 30,9 
 
 tity like velocity, and henceforward, we measure force in two 
 ways, either by the magnitude of the mass on which it im- 
 presses a certain velocity, or by the velocity which it im- 
 presses on a certain mass. With these elements, denoted by 
 means of lines, ciphers, and words, we are able to construct 
 an infinite number of different mental compounds, to conceive, 
 first, a movable body at rest, or to which no force is applied, 
 then, a movable body at rest to which a force is applied, then, 
 by a further complication, to imagine a movable body to 
 which are applied two or more equal or unequal forces, which 
 impel it in the same line, in the same or in contrary direc- 
 tions, or which impel it in different lines, etc. By this opera- 
 tion, the science of mechanics acquires similar outlines to 
 those of geometry, and the facts conform to the outlines in 
 the first case in the same manner and in the same degree as 
 in the second. 
 
 One of the most simple of these intellectual combina- 
 tions is that of a movable body at rest and remaining at rest 
 for an indefinite period ; for, in this case, there is no idea of 
 a new state introduced. Another, which is fellow to it, and 
 almost equally simple, is that of a body in motion which 
 moves on in a straight line with uniform velocity, and that in- 
 definitely; for, to form this conception, requires a minimum 
 of mental elements. In the first place, there is no simpler 
 line than the straight line, since, when the starting point is 
 given, all required to determine it is a single second point, 
 whilst for every other line, broken or curved, many or an in- 
 finite number of such points are required. Secondly, it is 
 more simple for velocity once given to subsist invariably with 
 the same magnitude ; for in this way, no new magnitude is 
 introduced. Lastly, it is more simple for the movement, 
 once given,, to subsist indefinitely; for in this way, no new 
 state is introduced. 
 
 Now it is an admirable thing that the bodies of nature, 
 however different they may be, however different may be the 
 real forces by which they are set in motion, or the real circum- 
 stances in which they happen to be at rest, all tend to con- 
 form to this double conception. We assure ourselves of this 
 y experience ; real matter is inert, and indifferent to rest or
 
 400 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 motion. In order for a body at rest to move, the interven- 
 tion of a force is required ; if this intervention is wanting, it 
 remains indefinitely at rest, and its tendency to persist in its 
 state is so thoroughly inherent to all its particles, that, accord- 
 ing to the magnitude of its mass, it requires a force of corres- 
 ponding magnitude to impress on it the same velocity. On 
 the other hand, in order that a body in motion may stop, or 
 change its velocity, or deviate from a straight line, there is 
 also required the intervention of another force. This stone 
 which I cast in the air, this ball driven from the cannon by 
 the explosion of powder, would continue their route indefi- 
 nitely, the one towards the stars, the other along a tangent to 
 the earth, in a straight line, with the initial velocity, if gravity 
 and the resistance of the air did not intervene to bend the 
 straight line, to diminish the velocity, and finally, to arrest 
 the movement. As far as we can judge by observation, there 
 is no particle of matter, at rest or in motion, which, taken by 
 itself and with the abstraction of all perturbing solicitations, 
 does not conform itself to this conception. 
 
 Let us now introduce a new condition, the simplest we 
 can, into our mental compound ; let us suppose the initial 
 force, instead of acting at the first instant only, to continue 
 to act during the whole duration of the movement, and 
 consequently the velocity of the movement to increase uni- 
 formly. By a coincidence almost as beautiful as the preced- 
 ing one, we find that this kind of motion is that of all falling 
 bodies.* Lastly, let us imagine a body, subject to this kind 
 of motion, and to uniform rectilinear motion besides. The 
 coincidence is no less surprising ; to our intellectual construc- 
 tion corresponds a real movement, similarly composed in all 
 
 * " ' When a stone falls,' says Galileo, ' if we consider the matter attentively, 
 we shall find that there is no addition, no increase, of the velocity more simple 
 than that which is always added in the same manner,' that is, when equal addi- 
 tions take place in equal times. From this law, thus assumed, he deduced that 
 the spaces described from the beginning of the motion must be as the squares of 
 the times ; and again, assuming that the laws of descent for balls rolling down in- 
 clined planes, must be the same as for bodies falling freely, he verified this con- 
 clusion by experiment." Whewell's " History of the Inductive Sciences," ii. 30, 
 citing Galileo. ' Dial. Sc.' iv. p. 91.
 
 CHAP. I.] GENERAL CHARACTERS AND GENERAL IDEAS. 401 
 
 respects, with respect to the curve traced, with respect to the 
 alternately increasing and decreasing velocities, that of the 
 planets about the sun. Thus it is that the mathematician 
 prepares beforehand moulds which the physicist will subse- 
 quently proceed to fill. There are three conditions requisite 
 for these moulds to have a chance of agreeing with things. 
 It is first necessary for the mental elements with which they 
 are fabricated to be traced in exact accordance with the ele- 
 ments of real things; for then the elements of our mould 
 will be found in nature. It is then necessary for them to be 
 very general, and, if possible, universal, for the more general 
 they are, the more considerable will be the number of indi- 
 viduals or instances in which they will be found, and if uni- 
 versal, they will be found in all. Lastly, it is necessary for 
 the combinations we give them to be as simple as possible ; 
 for there is the more chance of our finding them in nature, 
 since a minimum of elements and conditions is then sufficient 
 for their production. 
 
 IV. It will be understood that this process may be applied 
 to all classes of objects, since, in all classes of objects, we meet 
 and isolate general characters capable of being combined with 
 one another. In fact, we suppose perfect solids, that is to say 
 bodies absolutely rigid, and such that, all their parts being in- 
 dissolubly connected, one particle cannot be displaced without 
 displacing all the rest, in such a way that the reciprocal posi- 
 tion of their particles is never altered in any way. And so, we 
 assume the existence of perfect or absolutely fluid liquids, 
 such that no one of their particles has the least adherence to 
 the adjacent ones, and that all can move with perfect freedom 
 about one another. So finally, we conceive water or oxygen 
 as absolutely pure, platina or lead as free from all alloy, with- 
 out being sure that nature ever furnishes, or art has ever ob- 
 tained, objects such as we conceive. Among mental types so 
 constructed, there are some which are more particularly inter- 
 esting to us ; they are those to which we desire that things 
 should conform, and in this case the need of conformity be- 
 comes for us a spring of action. We construct the Useful, 
 the Beautiful, and the Good, and we so act as to approximate 
 things, as far as possible, to these constructions. For instance, 
 26
 
 402 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 when we find rough unhewn scattered stones, we imagine them 
 hewn, transported, and piled up, in the spot in which we wish 
 to live, and, in conformity with the idea of the wall so con- 
 structed, we actually construct the real wall which is to shel- 
 ter us from the weather. We survey the men who live around 
 us, we are struck with a certain general form appropriate to 
 them ; we observe, sometimes in one, and sometimes in ano- 
 ther, higher degrees of the external signs of some quality or 
 disposition beneficial to the individual or the race, agility, 
 vigor, health, sagacity, or energy ;* we gradually collect these 
 different signs ; we take pleasure in contemplating a human 
 form in which the characters we consider most important and 
 most valuable are manifested by a deeper and more universal 
 print, and if an artist be found in whom this group of conceived 
 conditions results in an express image, a sensible representa- 
 tion, an internal half-sight, he takes a block of marble and 
 hews out the ideal form which Nature has not been able to 
 display to us. Finally, when we survey the different motives 
 which impel men to wiH, we observe that the individual acts 
 most frequently with a view to his personal benefit, that is to 
 say through interest, often with a view to the benefit of 
 another person whom he loves, that is to say, through sympa- 
 thy, very rarely with a view to the general good, with complete 
 abstraction of his" interests or of his sympathies, with no more 
 regard to himself or his friends than for any other individual, 
 without any other intention than that of being useful to the 
 community present or future, of all sentient and intelligent 
 beings. We separate this last motive, we desire that it should 
 have an ascendancy in all human deliberation, we praise it 
 loudly, we inculcate it on others, we sometimes strive to give 
 it the empire over ourselves. We have thus constructed the 
 idea of a certain moral character, and, in fact, on occasion, at 
 a considerable distance, we adapt our actual character to this 
 model. Thus arise works of industry, art, and virtue, with 
 the object of filling or diminishing the interval which separates 
 our conceptions from things. 
 
 * I have worked out this analysis in detail in " La Philosophic de 1'Art," and 
 in " L'Ideal dans 1'Art."
 
 CHAP. II.] GENERAL JUDGMENTS. 403 
 
 CHAPTER II. 
 
 THE COUPLES OF GENERAL CHARACTERS AND GENERAL 
 PROPOSITIONS. 
 
 I. HITHERTO, in general ideas, we have studied only the 
 general ideas themselves and the manner in which they are 
 formed, sometimes by extraction, sometimes by construction, 
 sometimes when, after detecting a common character in 
 many similar facts or individuals, we have conceived it apart 
 by means of a sign, and have, by a series of additions and 
 rectifications, caused the comprehension and extension of 
 our idea to coincide with the comprehension and extension 
 of the character it denotes ; sometimes when, after distin- 
 guishing and conceiving apart certain very simple general 
 characters, we have combined ideas thus acquired so as to 
 form of them mental compounds, which are preliminary 
 moulds to which the real compounds have a possibility of 
 being found to conform, or preliminary models to which we 
 desire to make the real compounds conform. A second in- 
 vestigation remains to be effected. In nature, general charac- 
 ters are not detached from one another ; whatever be the 
 character we have noted, we never fail to find it connected 
 with some other. In fact, the one involves the other, or at 
 least tends to involve it. Sometimes it is the first which in- 
 volves the second, sometimes the second which involves the 
 first, sometimes each of them involves the other. In all 
 these cases, the two characters form a couple, and this couple 
 is termed a law. To conceive a law, is to connect together 
 two general ideas, in other words, to form a general judg- 
 ment, in other words again, to mentally enounce a general 
 proposition. We shall now examine how it is we arrive at 
 connecting these ideas, at forming these judgments, at men- 
 tally enouncing these propositions. 
 
 II. Let us first consider these couples or laws in them-
 
 404 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 selves. Every piece of iron exposed to damp becomes 
 rusted. Every crystal capable of scratching any other body 
 whatever is a diamond, that is to say a crystal of pure car- 
 bon. All bodies immersed in a liquid lose a portion of their 
 weight equal to the weight of the liquid they displace. In 
 every polygon, the sum of the internal angles together with 
 four right angles is equal to twice as many right angles as 
 the figure has sides. Here are laws ; each of them consists 
 in a couple of general and abstract characters which are con- 
 nected. On the one hand, the property of being iron and of 
 being exposed to damp, on the other, the formation of the 
 chemical compound termed rust ; on the one hand, extreme 
 hardness, and on the other, the property of being a crystal 
 of pure carbon ; on the one hand, the amount of weight lost 
 by the immersed body, and on the other, the equal quantity 
 of the weight of the displaced liquid ; on the one hand, the 
 sum of the internal angles of the polygon together with four 
 right angles, on the other hand, the equal sum of twice as 
 many right angles as the figure has sides : it is evident that 
 all these data are general characters, that is to say characters 
 common to an indefinite number of individuals or cases ; 
 that all these data are abstract characters, that is to say ex- 
 tracts considered apart ; that all these data are connected 
 characters, that is to say such that, the first being given, the 
 second is also given. There is nothing more advantageous 
 to the human mind than this structure of things ; we discern 
 at once that our chief attempt must be to discover connec- 
 tions similar to the foregoing ones ; for there is no better 
 means of extending and increasing our knowledge. When 
 once the law is discovered, the first character becomes the 
 indication of the second ; in future it will be sufficient for us 
 to ascertain the presence of the first ; we may then, blindfold 
 and without inquiry, assert the presence of the second. In 
 fact, at present, it is sufficient for us to know that this piece 
 of metal is iron, and exposed to damp from water, steam, or 
 fog, to foresee that, in some hours or days, it will be covered 
 with rust. It is sufficient for us to collect the water which 
 has run from the full vessel and to weigh it, to know before- 
 hand the weight lost by the immersed body. It is sufficient
 
 CHAP. II.] GENERAL JUDGMENTS. 405 
 
 for us to count the sides of the polygon, to take two from 
 their number, and multiply the remainder by two, to know 
 beforehand the number of right angles contained by the 
 polygon. It is sufficient for us to observe that a given crys- 
 tal scratches the hardest bodies, to enable us to declare that 
 when burnt it will furnish carbonic acid. Owing to these 
 established connections, an anatomist who opens a human 
 body, is able to describe beforehand the color, form, struc- 
 ture, and disposition of the nervous cells and arterial net- 
 work which his microscope will show in a particular part of 
 a particular organ. Owing to these established connections, 
 an astronomer is able to predict the duration, time, and mag- 
 nitude of the eclipse, which, a century hence, will hide the 
 sun from the inhabitants of some particular country. 
 
 These very valuable connections are of many kinds. 
 Sometimes the two connected characters are simultaneous. 
 Two cases then present themselves. Either the first charac- 
 ter may involve by its presence the presence of the second 
 without the presence of the second involving that of the first. 
 Thus, when the sum of the digits of a number is divisible by 
 nine, the number itself is divisible by three, but the converse 
 is not true ; when an animal has mammae, it has vertebrae, 
 but the converse is not true. In this case, the link joining 
 the two characters is unilateral or simple. Or again, the first 
 character may involve by its presence the presence of the sec- 
 ond, and the presence of the second may involve in its turn 
 the presence of the first. Thus, in every polygon, three 
 sides are always accompanied by a number of angles equal to 
 two right angles, and conversely ; in every mammal, incisor 
 teeth invariably accompany a short digestive tube and car- 
 nivorous instincts, and conversely. In this case, the link join- 
 ing the two characters is bilateral and double. Sometimes, 
 of the two connected characters, one termed thfe antecedent 
 precedes, and one termed the consequent follows ; the first is 
 then termed the cause of the second, and the second the effect 
 of the first. Then again two cases present themselves. 
 Either the first character may excite by its presence the ex- 
 istence of the second, and the second, in its turn, may re- 
 quire, for its production, the preliminary presence of the first.
 
 4 o6 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Thus, every movable body to which are applied two diver- 
 gent forces of which one is continuous will describe a curve ; 
 and a movable body in order to describe a curve requires 
 the previous application of two divergent forces of which one 
 is continuous. In this case, the link joining the two charac- 
 ters is bilateral or double. Or again, the first may excite by 
 its presence the existence of the second, without the second 
 requiring for its production the previous presence of the first. 
 Thus, every series of vibrations of certain velocity transmit- 
 ted to the auditory nerve by the surrounding medium excites 
 in us the sensation of sound ; but this sensation may arise 
 spontaneously in our sensory centres, without the previous 
 vibration of an external body or a surrounding medium. In 
 this, which is the most usual case, the link of the two charac- 
 ters is unilateral or simple ; it is the most important case and 
 the one which we shall examine with most attention ; we can 
 reduce the others to it, and we usually express it by saying 
 that the cause produces the effect. 
 
 III. It now remains to be seen in what the connection of 
 the two characters consists. Is there any virtue or secret rea- 
 son which is resident in the one and involves or evokes the 
 other ? This question we reserve ; we shall discuss it later on. 
 At present, the words connection, link, implication, excite- 
 ment, requirement are nothing more than abbreviatory meta- 
 phors. When we say that the antecedent gives rise to the 
 consequent, we are not thinking of the mysterious link by 
 which metaphysicians connect cause and effect, nor of the in- 
 timate and incorporal force which certain philosophers insert 
 between the thing producing and the product. " The only 
 notion," says Mill, " of which induction has need, may be at- 
 tained by experience. We learn by experience that there is 
 in nature an invariable order of succession, and that each fact 
 is always preceded by another fact. We call the invariable 
 antecedent, cause, and the invariable consequent, effect." No 
 other foundation underlies these two words. We wish sim- 
 ply to say that, at every time and place, the application of 
 heat will be followed by the dilatation of bodies, that at every 
 time and place, the vibration of the external body transmitted 
 by the surrounding medium to the healthy auditory nerve
 
 CHAP. II.] GENERAL JUDGMENTS. 407 
 
 will be followed by the sensation of sound. " The real cause 
 is the series of conditions the whole of the antecedents with- 
 out which the effect would not arrive There is no 
 
 scientific foundation for distinguishing between the cause of 
 a phenomenon and the conditions of its happening .... The 
 distinction drawn between the patient and the agent is purely 
 verbal .... The cause is the sum of negative and positive 
 conditions taken together; the whole of the circumstances 
 and contingencies of every kind, which, once given, are inva- 
 riably followed by the consequence." Philosophers are mis- 
 taken when they think that they discover in our will a differ- 
 ent type of causation, and assert that we there see efficient 
 force in act and exercise. Nothing of the sort is to be found 
 there ; but there as elsewhere, we find constant successions 
 only. We do not find fact invariably engendering fact, but 
 fact invariably accompanying fact. To quote Mill again : 
 " Our will produces our bodily actions, as cold produces ice, 
 or as a spark produces an explosion of gunpowder." There, 
 as elsewhere, we find an antecedent the resolution which is 
 a momentary character of our mind, and, there as elsewhere, 
 a consequent the muscular contraction which is a moment- 
 ary character of one or more of our organs ; experience con- 
 nects them and enables us to foresee that the contraction will 
 follow the resolution, just as it enables us to foresee that the 
 explosion of gunpowder will follow the contact of the spark. 
 More precisely still and whatever be the two characters, 
 simultaneous or successive, momentary or permanent, the link 
 by which the first involves, excites, or supposes the second as 
 its contemporary, consequent, or antecedent, is nothing more 
 than a peculiarity of the first considered alone and apart. 
 This means that the one possesses, in itself, the property of 
 being accompanied, followed, or preceded by the other; that 
 is all. In other words, it is sufficient for the one to exist for 
 the other to be its companion, precursor, or successor. As 
 soon as the one is given, no other condition is required ; the 
 circumstances may be of any kind ; it does not matter. 
 Whether it be given in a particular individual with a particu- 
 lar group of other characters, at a particular time or place, is 
 a matter of indifference ; the property it possesses does not
 
 408 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 depend on circumstances, nor on the individual, nor on the 
 surrounding group of other characters, nor on the place, nor 
 on the time ; taken apart and in itself, isolated by abstraction, 
 extracted from the various media in which we meet with it, 
 it possesses this property. This is why, into whatever me- 
 dium we transfer it, it preserves this property. If it possesses 
 this property at every time and place, this is because it pos- 
 sesses the property of itself and by itself alone ; if it possesses 
 this property without exception, this is because it possesses 
 the property without condition. If all triangles enclose angles 
 together equal to two right angles, it is because the abstract 
 triangle has the property of enclosing angles together equal to 
 two right angles. If every piece of iron exposed to damp be- 
 comes rusted, it is because iron taken apart, in itself, and sub- 
 mitted to damp taken apart, and in itself, possesses the prop- 
 erty of becoming rusted. If the law is universal, it is from its 
 being abstract. There is nothing surprising in this constitu- 
 tion of things. It is no more strange to find companions, pre- 
 cursors, and successors in the case of a general character than 
 in that of a particular individual or a momentary event. No 
 doubt in the infinite dispersion and remediless flow of being, 
 these sorts of characters are the only elements which are ev- 
 erywhere the same and which always arise the same : but they 
 do not exist outside individuals and events, as Plato taught, 
 nor in a world other than our own ; for they are the charac- 
 ters of the events and individuals which compose our world. 
 They are, like individuals and events, forms of existence, and 
 differ only from individuals and events by being more stable 
 and more widely spread forms. For this reason, we must ex- 
 pect to discover that they too have accompaniments, prece- 
 dents, sequences, peculiarities, personal properties, and, to 
 succeed in this, we have only to observe them apart. 
 
 It is precisely in this that the difficulty lies. For how are 
 we to observe apart a character which, being an extract, is 
 only met with and can only be met with in a particular case 
 or individual, that is to say in company with other charac- 
 ters? How can we contrive to study in nature iron in itself 
 exposed to damp in general, and to ascertain that, in this 
 state of abstraction, it has rust in general as a consequence ?
 
 CHAP. II.] GENERAL JUDGMENTS. 409 
 
 How can we contrive to detect the abstract triangle which is 
 neither scalene, nor isosceles, nor right angled, to measure 
 its abstract angles which are neither equal nor unequal, and 
 to prove that, in this strange state, their sum is equal to two 
 right angles? From the question thus presented, an answer 
 follows. When once the obstacle is clearly determined, we 
 are usually able, if not to suppress it, at least to evade it. 
 Two artifices of method lead us to our end. We have dis- 
 tinguished two kinds of general characters. The first are 
 real, and the general ideas which correspond to them, for 
 instance, those of iron, of damp, and of rust, being formed by 
 extraction, become by degrees adjusted to them ; they are the 
 object of the experimental sciences; and their connections 
 are discovered by the inductive road. The second are pos- 
 sible only, and the general ideas which correspond to them, for 
 instance, those of the triangle, the angle, parallel lines, being 
 formed by combination, are outlines only, to which certain 
 real things have a possibility of being adjusted ; they are the 
 object of the constructive sciences, and their connections are 
 discovered by the deductive road. Let us follow these roads 
 in turn, and attempt to observe the successive stages of the 
 mind in traversing them. 
 
 I. LAWS CONCERNING REAL THINGS. 
 
 I. Here, in the first road, our starting point is the already 
 explained acquisition of general ideas. In fact, the child of 
 fifteen months old, who already repeats and applies certain 
 general names, has but to associate two of them in order to 
 form a general proposition, and this is what happens when an 
 object which calls up in him a name also arouses in him 
 another name. He then attempts his first lisping, verbless 
 sentences: nice soup, naughty cat, etc. The mechanism of 
 this junction is very simple, and here animal thought leads 
 naturally to human thought. When a dog sees in a trench 
 or pit a flowing inodorous, uncolored, clear liquid, this per- 
 ception, by virtue of anterior experience, excites in him by 
 association the image of a sensation of cold, and the percep- 
 tion joined to the image form in him a couple. In the case
 
 4IQ THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 of the child, owing to the names he learns and understands, 
 the same perception further calls up the word water ; the 
 same image further calls up the word cold, and the two 
 words water, cold, associated by contiguity, form a second 
 superadded couple. 
 
 Now later on, when the child reverts to and dwells on 
 these two words, he finds that the first excites in him an 
 indefinite series of anterior experiences, that of the water- 
 bottle, the well, the spring, the rain, the river, and that in 
 each of these representations the word cold is called up as 
 well as the word water. He then observes that they form 
 a couple through all the procession and all the review ; this 
 he expresses by saying that all waters are cold. Somewhat 
 later on, he omits the differences of the various representa- 
 tions and preserves the couple itself alone ; this he expresses 
 by saying that water is cold. In this manner, he enounces, 
 mentally or aloud, his first general propositions and his first 
 abstract propositions. By degrees, as he grows older, he 
 learns new words ; he applies them to the old couples of 
 representations which former experience has already es- 
 tablished in him, and to the new couples of representations 
 which incessant experience daily establishes in him ; thus, 
 arise new couples of understood words, that is to say, of 
 ideas. It is between eighteen months and five or six years 
 old that the greater part of this process is accomplished ; it 
 is continued, later on and up to adult life, but with fewer 
 acquisitions. The child thus forms a number of judgments 
 on the objects and facts familiar to him. "Sugar is nice. 
 Fire burns. A blow hurts. Cats scratch. Cows eat grass. 
 A person who speaks harshly is angry." At first, when 
 given an individual or event of a certain class, he formed 
 only one of these general judgments respecting it ; soon he 
 forms two, three, four, then ten, twenty, a hundred, and so 
 on. Seeing a bounding form, with which the name cat is 
 associated in his mind, he says, first, that the cat scratches ; 
 later on, he will say that it mews, that it climbs on the 
 roofs, that it catches mice, and so on. It is the same with 
 all other class names ; each of them ends by calling up a 
 considerable number of general judgments, and each is capa-
 
 CHAP. II.] GENERAL JUDGMENTS. 4! i 
 
 ble of calling up an indefinite number of them. Each of 
 them thus, by its more or less ample escort, sums up our 
 more or less ample experience, and being the product of our 
 experience, affords its measure. 
 
 General judgments of this kind and of this origin are 
 sufficient for practice. Children, savages, and uneducated 
 persons form few others, and few others are made use of in 
 ordinary conversation. Many men and many nations never 
 go beyond this. But we are capable of going beyond it, and 
 of passing from ordinary propositions to scientific propo- 
 sitions. Experience at its commencement led us to the first ; 
 prolonged experience leads us to the second. For on apply- 
 ing our primitive judgment to new instances, we find it inexact. 
 The child at first concluded that all waters are cold ; if he 
 puts his hand into a kettle just taken from the fire, he changes 
 his opinion and no longer attributes cold to water, except of 
 a certain temperature. A gardener who has never left his 
 province, considers that all swans are white ; if he is taken to 
 the Zoological Gardens and shown the black Australian swans, 
 he will no longer attribute whiteness except to a certain 
 variety of swans. A student of botany thinks that all plants 
 with an arborescent bark arranged in concentric layers have 
 two cotyledons ; when shown the dodder and two or three 
 other kinds, he sees that the preceding law is almost uni- 
 versal, but not universal. By degrees, owing to such correc- 
 tions, our general judgments become adjusted to things. To 
 the couple of abstract ideas associated in our minds, there 
 corresponds, line for line, a couple of abstract characters 
 associated in nature ; henceforward, in every new instance we 
 observe, our proposition receives a new justification, and the 
 law enounced no longer meets with exceptions. At the 
 expiration of a very long time, after numbers of correspond- 
 ences thus verified, men of certain races and of certain civi- 
 lizations for instance, modern Europeans have ended by 
 believing that this is so in every case, that such is the consti- 
 tution of things, that the whole of nature is governed by 
 laws, that all its course is uniform, that in every time and 
 every place, in the moral as well as in the physical world, 
 when any character is given, there is necessarily another
 
 4 I2 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 which is connected with it. Is this supposition true ? Have 
 we here a wholly universal law? We shall inquire into this 
 later on. Meanwhile, we are able, from the vast number of 
 ascertained laws within us and about us, to admit that it is so 
 for our little universe, or at all events to avail ourselves of it 
 on occasion as an instrument of research, to discover the 
 unknown character which we suppose to be attached to the 
 known character, remembering that we have in every case 
 to verify our success or failure by the conformity or diver- 
 gence of the supposition we have admitted and the subsequent 
 facts. Thus it is we inquire, and our different modes of 
 inquiry in this route are the different processes of scientific 
 Induction. 
 
 II. We begin then with an hypothesis, but with a very 
 probable hypothesis, warranted by a multitude of precedents, 
 and capable, moreover, of being invalidated or confirmed 
 after we have availed ourselves of it, therefore as well selected 
 as possible to put us in the right road, and to warn us off the 
 wrong road if we happen to be led into it ; this hypothesis 
 being that a character, taken apart, has an influence ; by 
 itself and by itself alone, it involves something else, either 
 contemporary, antecedent, or consequent ; it is sufficient for 
 it to be given for one or more other characters to be also 
 given. 
 
 Observe this word it is sufficient. It is the key of the door ; 
 for it puts in our hand a property of the unknown character, 
 a kind of distinctive mark, by means of which we shall recog- 
 nize it ; since the fact of the presence of the other is sufficient 
 to give us this, we shall recognize by this characteristic that it 
 is present in all the cases in which the other is present ; in 
 none of these cases can it fail. This is its special sign, and, 
 so to speak, the ticket which denotes it from all other things. 
 Hence a first method, termed by Mill The Method of Agree- 
 ment. We collect many cases in which the known character 
 is given ; according to what has just been said, the unknown 
 character is met with in them all ; in other words, it is com- 
 mon to them all, and is, therefore, found comprised in the por- 
 tion which is common to them. Here, we choose cases as 
 dissimilar as possible, and take away their differences. The
 
 CHAP. II.] GENERAL JUDGMENTS. 
 
 greater and more numerous their differences, the smaller will 
 be the common remnant left by the elimination ; as this rem- 
 nant is the only common part, it necessarily comprises the 
 character we are in search of, and if after this elimination 
 there remains a single character only, this single character is 
 necessarily the character we are in search of. 
 
 Thus, take all animals with mammae, and especially the 
 most widely different ones, the whale, the bat, the monkey, 
 the horse, the rat, the ornithorynchus, and exclude their dif- 
 ferences. After this enormous elimination, there will only re- 
 main a small number of common characters, double circula- 
 tion, the circumscription of the lungs by a pleura, the property 
 of bringing forth the young alive ; either this entire group or 
 some element of it, among others the last, is evidently the 
 character we are in search of; in fact, the last invariably ac- 
 companies the possession of mammse. Let us collect a num- 
 ber of oils as different as possible, of alkaline substances as 
 different as possible, and combine them ; here is the known 
 antecedent. Now let us seek for the known consequent, and, 
 for this, let us compare together their different products. If 
 we set aside their differences, we shall find one common char- 
 acter only, that of being a soap ; this, then, is the character 
 which is connected as consequent to the presence of the given 
 antecedent. Let us now take a known and well-defined con- 
 sequent, the sensation of sound.* To find its antecedent, we 
 collect many cases in which a healthy ear perceives a sound, 
 the sound produced by a bell, by a string which is pinched or 
 rubbed by a bow, the sound of a beaten drum, of a horn which 
 is blown, the sound of the human voice, the sound heard when 
 the head is under water, or on putting the ear to a beam which 
 is slightly struck, etc. After a long examination, we discover 
 that all these cases agree, as far as we can judge, in one single 
 point, which is the presence of a reciprocating movement, in 
 other words, of a vibration of the sonorous body, comprised 
 between certain limits of slowness and rapidity, and prop- 
 agated through a medium to the auditory organ. This 
 
 * Ordinary Sound, that is to say, excited by an external antecedent, and not 
 the subjective sound excited by a spontaneous state of the auditor)' organ.
 
 414 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 transmitted vibration, then, is the antecedent we are in 
 search of. 
 
 Such is the first method ; by it we exclude the differences 
 of the cases in question, which sets'apart their resemblances. 
 It requires as preliminary, the collection of many cases in 
 which the known character is given. It adopts as a guide, the 
 necessary presence of the unknown character in all cases in 
 which the known character is found. It has for its auxiliary, 
 the greatest possible difference of appearance between the 
 cases. It has for its object, the severance of their agreements. 
 It has, as its effect, the isolation of a remnant, which is, in 
 whole or part, the character we are in search of. 
 
 We have only to invert this method to possess another, 
 termed by Mill The Method of Difference. Let there be a 
 known character, and take two cases ; the first in which it is 
 given, the second in which it is not given. Since, by its pres- 
 ence alone, it introduces an unknown character, when absent 
 it will not introduce this ; this character which it would have 
 introduced, will be wanting, and, therefore, will not be found 
 in the second case. Here is a new property of the unknown 
 character, a second distinctive characteristic, by means of 
 which we shall be able to discover it ; we shall recognize it by 
 the mark, that, being present in the first case, it is absent in 
 the second. Here we choose two cases as similar as possible. 
 Since it is present in the one and absent in the other, it cannot 
 be one of the characters in which they are alike, and must 
 necessarily be one of the characters in which they differ. Let 
 us exclude, then, all the characters in which they are alike ; 
 the remainder is the sum of their differences ; and it is in this 
 remainder that the character we are in search of is necessarily 
 comprised. But this remainder is very small, since we have 
 chosen the two cases as much alike us possible ; if, therefore, 
 this remainder consists in one single'character, this character 
 is necessarily the one we are in search of. 
 
 Thus, take a known character, extreme hardness, or the 
 capacity of scratching all other bodies. We take two bodies 
 as much alike as possible, one in which the character is pres- 
 ent, the other in which it is absent ; one of these bodies is a 
 diamond which is pure carbon ; the other is purified carbon ;
 
 CHAP. II.] GENERAL JUDGMENTS. 
 
 or, better still, let one body be a particular diamond, the 
 other the same diamond burnt and reduced to the state of 
 cinder. Chemical properties, weight, component molecules, 
 many characters, and those the most important of all, are 
 exactly alike in the two cases. We eliminate them, and have 
 as residue a group of characters which are present in the dia- 
 mond and absent in the piece of coke, brilliancy, transpar- 
 ency, octohedric form, crystalline structure. It is this whole 
 group, then, or an element of this group, and especially the 
 last, which is the character we are in search of; in fact, the 
 other elements of the group are nothing more than various 
 aspects of the last, and in carbon, crystalline structure inva- 
 riably accompanies extreme hardness. Again, when given 
 the sensation of sound, let us select two cases, one in which 
 it is produced, the other in which it is not produced, and let 
 us select them so very similar as to differ in a very small 
 number of characters only, and, if possible, in one character 
 alone. For this purpose, let us repeat the same case twice, 
 and introduce or suppress on the second occasion a single 
 well-defined circumstance ; this added or excluded circum- 
 stance, being the only difference separating the two cases, 
 will be the character we are in search of. For instance, in 
 the case of the continuous sound produced by a vibrating 
 tuning-fork, we touch lightly the little blades, this stops their 
 vibration, and the sound at once ceases. In the case of a bell 
 struck by its clapper, we put it under the receiver of an air- 
 pump and exhaust the air, and the sound at once ceases. In 
 the case of the silent tuning-fork, we press it and suddenly 
 let go the blades, which restores their vibrat'on, the sound 
 at once recommences. In the case of the clapper silently 
 striking the bell, we let the air into the receiver, the sound 
 at once recommences. Here the only circumstance in turn 
 introduced or suppressed among the antecedents of the sound 
 is the rapid reciprocating movement in the case of the tuning- 
 fork, and the presence of the elastic medium in the case of 
 the bell. This double circumstance, then, is the only char- 
 acter by which the case in which the sound is present, dif- 
 fers from the case 'in which the sound is wanting, hence it 
 follows that it is the antecedent we are in search of.
 
 41 6 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Such is the second method ; by it we exclude the resem 
 blances of the cases considered, and so set apart their differ- 
 ences. It requires as preliminary the selection of two cases 
 distinguished, one by the presence, the other by the absence, 
 of the known character. It adopts as a guide the necessary 
 absence of the unknown character in all the cases in which 
 the known character is absent. It has, for its auxiliary, the 
 greatest possible resemblance between the two cases. It has, 
 for its object, the severance of differences. It has as its ef- 
 fect the isolation of a remnant, which is, in whole or part, the 
 character we are in search of. 
 
 These two methods suggest a third, termed by Mill, The 
 Method of Concomitant Variations, To the two marks by 
 which we make discovery of the unknown character, it adds a 
 a new one. We have recognized it by the characteristic of 
 its presence whenever the known character is present, and by 
 the characteristic of its absence whenever the known charac- 
 ter is absent ; we can also recognize it by the characteristic 
 that, whenever the known character varies, the unknown char- 
 acter also varies in a corresponding manner. In fact, in one 
 aspect or another,"* the known character may be considered 
 as a sum of degrees, each of which taken apart has its influ- 
 ence ; for if each taken apart had no influence whatever, we 
 might successively suppress them all up to the last, and, 
 therefore, suppress the character itself, without suppressing 
 its influence ; we might also add them all, one after another, 
 up to a certain limit, and, therefore, reconstitute the charac- 
 ter itself as fully as we pleased, without re-constituting its 
 influence. Now these two suppositions are contrary to the 
 notion of the character as we have assumed it. Thus, from 
 
 * For instance, in the corresponding variations which the form of the teeth, 
 the structure of the condyle, the length of the intestines, and the arrangement of 
 the limbs, undergo in different species, the observed organ becomes more or less 
 fitted or unfitted for carnivorous or herbivorous life ; the degree of fitness for car- 
 nivorous life being lowered in proportion as the degree of fitness for herbivorous 
 life increases. In this double sense, an organ may be considered in the aspect of 
 its quantity, and may present a sum of greater or less degrees. Hence, the 
 methods of Cuvier for determining unknown organs from their dependence with 
 relation to known organs.
 
 CHAP. II.] GENERAL JUDGMENTS. 417 
 
 this very notion, we may conclude that every variation of the 
 known character involves a variation of the unknown charac- 
 ter, and on this indication, may seek for the unknown char- 
 acter. 
 
 For instance, take a known character, the progressive re- 
 tardation, and consequent final extinction, of the movement 
 of the pendulum. We cannot construct a pendulum to oscil- 
 late for ever, and consequently cannot find a second case in 
 which the known character is absent. For this impracticable 
 case of absence of retardation, we substitute a number of 
 practical cases of diminished retardation. We diminish more 
 and more the obstacles the pendulum meets with, and find 
 that its retardation is proportionately diminished. When 
 the friction at the point of suspension is reduced as much as 
 possible, and when the surrounding air is exhausted as much 
 as possible, it takes thirty hours, instead of some minutes, for 
 the movement to stop. In proportion as the obstacles ap- 
 proach the degree at which they would vanish, the retarda- 
 tion approaches the degree at which it would vanish. As far 
 as we are able to judge, there is, between the first case in 
 which the pendulum ceases to oscillate after a few minutes, 
 and the other cases in which it continues its oscillation for a 
 longer and longer time, one difference only, which is that, 
 in the first case, the obstacles are greater, and that, in the 
 others, they are less ; the presence, then, of an increase in 
 the obstacles is the antecedent of an increase in the retarda- 
 tion. But this does not as yet prove that, were there no 
 obstacles, there would be no retardation. For it might hap- 
 pen that the diminution of the antecedent and the diminu- 
 tion of the consequent did not proceed at the same rate ;: 
 perhaps, in proportion as the resistance is diminished by one 
 half, the retardation is diminished only by a fourth or other 
 smaller fraction ; this would be the case, if the retardation 
 had two causes, one of which was a property inherent to the 
 motion itself, that is to say a tendency to cease after the 
 lapse of a certain time, the other appertaining to the circum- 
 stances, that is to say to the resistance of the surrounding 
 bodies. In this case, the complete suppression of the ob- 
 stacles would only diminish the retardation, without wholly 
 27
 
 4 i 8 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV 
 
 suppressing it ; the pendulum would oscillate sixty hours 
 and more, but would finally stop. We must prove, then, 
 that the retardation diminishes at the same rate as the re- 
 sistance, and that every degree added to or taken from the 
 resistance corresponds to an equal degree added to or taken 
 from the retardation. This is effected by the two methods 
 already described, though seeking, no longer the antecedent 
 of the retardation, but the antecedents of two of its diminu- 
 tions or augmentations measured beforehand, and through 
 discovering, by the extraction of agreements or differences, 
 that these antecedents are two precisely equal diminutions 
 or augmentations introduced into the sum of the resistances 
 presented by the surrounding obstacles. When this is 
 established it becomes proved that, when the resistance 
 ceases, the retardation ceases. This is a proposition which 
 we were just now unable to establish by experience : but 
 now we have no need to establish it by experience ; the gap 
 is filled up ; we may dispense with observation ; we have its 
 equivalent. Thanks to this equivalent, we know now that 
 the case in which the motion is retarded, and that in which 
 it is not retarded, differ only in one character, namely, the 
 resistance opposed, in the first case, by obstacles ; hence 
 it follows that this resistance is the antecedent we are in 
 search of. Such is the third method which, compounded of 
 the first and second, is a substitute for the second, and which 
 is often of higher value than they are, from its determining, 
 not only the quality, but also the quantity, of the unknown 
 character.* 
 
 All these methods employ the same artifice, that is to 
 say the elimination or exclusion of characters other than 
 the character we are in search of. Let us take a known 
 character; it is accompanied, followed, or preceded by ten 
 others. Which one or more of these ten are so connected 
 with its presence, that its presence is sufficient to give them 
 as its companions, antecedents, or consequents ? All the 
 
 * Mill, after describing this method, indicates a fourth, which he terms the 
 Method of Residues. It is but another case of the Method of Differences, and is 
 but rarely employed. The three which we have explained had their first origin 
 in Bacon's " Tables of Presence, Absence, and Degrees."
 
 CHAP. II.] GENERAL JUDGMENTS. 
 
 difficulty, and the only possible solution, lie here. To resolve 
 the difficulty and effect the solution, elimination is required, 
 that is to say the exclusion, amongst the ten characters, of 
 those which are not thus connected with the presence of the 
 known character. But, as we are not able actually to exclude 
 them, and as, in nature, the character we are in search of is 
 always hidden in a crowd of others, we collect cases which 
 by their diversity entitle the mind to clear away this crowd. 
 We look for indications which may enable us to distinguish 
 between the character we are in search of and superfluous 
 characters. We find three of these indications, and apply 
 them ; for greater security, we apply all three of them suc- 
 cessively in order that they may correct one another. When 
 the expulsion is accomplished, what remains is the character 
 we are in search of. 
 
 In some cases these eliminating processes are ineffectual, 
 namely, in those in which the consequent, though produced 
 by a concurrence of antecedents, cannot be reduced into its 
 elements. Methods of isolation are then impracticable ; and, 
 as we can no longer eliminate, we can no longer perform 
 induction. Now, this grave difficulty presents itself in nearly 
 all cases of motion ; for nearly every motion is the effect of 
 a concurrence of forces, and the respective effects of the 
 different forces are found so mixed up in it that we cannot 
 separate them without destroying it, and it seems impossible 
 to know what part each force has in the production of the 
 movement. Take a body acted on by two forces whose 
 directions form an angle ; it moves along the diagonal ; every 
 part, every moment, every position, every element of its 
 movement is the combined effect of the two impelling forces. 
 The two effects are so intimately combined that we cannot 
 isolate either of them to refer it to its origin. To perceive 
 each effect separately, we should have to consider the mo- 
 tions turned in another direction, that is to say to suppress 
 the given movement and replace it by others. It is the 
 double consequent of a double antecedent, and, as we cannot 
 isolate one or other of its two parts, we cannot isolate one or 
 other of the two parts of its antecedent. Neither the usual 
 method of Agreement or of Difference, nor the subsidiary
 
 420 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 methods of Residues or of Concomitant Variations, all of 
 which are decomposing and eliminative, can serve us in a 
 case which by its nature excludes all elimination and all 
 decomposition. We must therefore evade the obstacle, and 
 here it is that the Method of Deduction the last key to Na- 
 ture comes in. We commence by borrowing a process from 
 the sciences of construction ; we leave the effect, we set to 
 work beside it, we study other simpler cases ; we examine 
 various analogous effects or consequents, we connect each to 
 its cause or antecedent by the processes of ordinary induc- 
 tion ; then, we form a construction. We mentally collect 
 many of these antecedents or causes, and we conclude, from 
 their known consequents or effects, what must be their total 
 consequent or effect. We then verify if the total effect 
 given is exactly similar to the total effect predicted, and, if 
 so, we attribute it to the combination of causes we have fabri- 
 cated. Thus, to discover the causes of the motion of the 
 planets, we establish, by simple inductions, first, the law 
 connecting the motion in direction of the tangent with a 
 force of initial impulsion, then, the law connecting the fall of 
 a body towards another with the accelerating force of gravity. 
 From these two laws obtained by induction, we deduce, by 
 calculation, the various positions and velocities which a body 
 would assume, under the combined influences of an initial 
 impulsion and accelerating gravity, and, after verifying that 
 the observed planetary motions coincide exactly with the 
 foreseen motions, we conclude that the two forces in question 
 are actually the causes of the planetary motions. "To the 
 Deductive Method," says Mill, " the human mind is indebted 
 for its most conspicuous triumphs in the investigation of 
 Nature. To it, we owe all the theories by which vast and 
 complicated phenomena are embraced under a few simple 
 laws." It is only a derivation of the preceding methods; for 
 it starts from a property of the antecedent obtained by those 
 methods. This property is that of being sufficient, that is to 
 say of exciting, by its presence alone, a certain consequent. 
 Therefore, if it be present, the consequent will arise ; and, if 
 another antecedent obtained in the same way is also present, 
 its consequent will similarly arise ; so that the whole conse-
 
 CHAP. II.] GENERAL JUDGMENTS. 421 
 
 quent will be mixed and double. If now the whole conse- 
 quent observed coincides in all its parts with the whole 
 consequent predicted, we shall say with certainty that the 
 double antecedent supposed is sufficient to cause it to arise, 
 and we shall be able to assume that, in the case in question, 
 this double antecedent in fact exists. In truth, this will only 
 be a supposition or hypothesis; but it will be the more 
 probable in proportion as the total consequent, being more 
 complex and more multiplex, further limits the number of 
 hypothesis capable of accounting for it ; and it will be wholly 
 certain when, as is the case with the motion of the planets, 
 we can demonstrate that no other combination of forces 
 could produce ft, that is to say that the double antecedent 
 assumed is not only possible, but alone possible, and there- 
 fore, real. 
 
 These are the rules: an example will make them clearer; 
 there is one in which we shall see all the methods in exercise 
 Dr. Well's theory of Dew. I shall cite the exact words of 
 Mill and Herschel.* They are so clear that we must give 
 ourselves the pleasure of considering them. We must begin 
 by separating dew from rain, and the moisture of fogs, and 
 by defining it as " the spontaneous appearance of moisture 
 on substances exposed in the open air, when no rain or visible 
 wet is falling." What is the cause of the phenomenon we 
 have thus defined, and how was that cause discovered ? 
 
 In the first place, " ' we have analogous phenomena in 
 the moisture which bedews a cold metal or stone when we 
 breathe upon it ; that which appears on a glass of water fresh 
 from the well in hot weather ; that which appears on the in- 
 side of windows when sudden rain or hail chills the external 
 air ; that which runs down our walls when, after a long frost, 
 a warm moist thaw comes on.' Comparing these cases, we 
 find that they all contain the phenomenon which was pro- 
 posed as the subject of investigation. Now, ' all these in- 
 stances agree on one point the coldness of the object dewed, 
 in comparison with the air in contact with it.' Bat there 
 
 * Mill, " Logic," 4th edition, i. 451-8, citing from Sir J. Herschel, "Discourse 
 on the Study of Natural Philosophy."
 
 422 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 still remains the most important case of all, that of noctur- 
 nal dew : does the same circumstance exist in this case ? 
 ' Is it a fact that the object dewed is colder than the air ? 
 Certainly not, one would at first be inclined to say ; for what 
 is to make it so ? But . . . the experiment is easy : we have 
 only to lay a thermometer in contact with the dewed sub- 
 stance, and to hang one at a little distance above it, out of 
 reach of its influence. The experiment has therefore been 
 made; the question has been asked, and the answer has been 
 invariably in the affirmative. Whenever an object contracts 
 dew, it is colder than the air.' 
 
 " Here then is a complete application of the Method of 
 Agreement, establishing the fact of an invariable connection 
 between the deposition of dew on a surface, and the coldness 
 of that surface compared with the external air. But which 
 of these is cause, and which effect ? or are they both effects 
 of something else? On this subject, the Method of Agree- 
 ment can afford us no light : we must call in a more potent 
 method. ' We must collect more facts, or, which comes to 
 the same thing, vary the circumstances ; since every instance 
 in which the circumstances differ is a fresh fact : and es- 
 pecially we must note the contrary or negative cases, i. e., 
 where no dew is produced : ' a comparison between instances 
 of dew, and instances of no dew, being the condition neces- 
 sary to bring the Method of Difference into play. 
 
 " ' Now, first, no dew is produced on the surface of pol- 
 ished metals, but it is very copiously on glass.' Here is an 
 instance in which the effect is produced, and another instance 
 in which it is not produced. . . . But, as the differences be- 
 tween glass and polished metal are manifold, the only thing 
 we can as yet be sure of is, that the cause of dew will be 
 found among the circumstances by which the former sub- 
 stance is distinguished from the latter. . . . To detect this 
 particular circumstance of difference we have but one practi- 
 cable method that of Concomitant Variations. 'In the 
 cases of polished metal and polished glass, the contrast shows 
 evidently that the substance has much to do with the phe- 
 nomenon, therefore let the substance alone be diversified as 
 much as possible, by exposing polished surfaces of various
 
 CHAP. II.] GENERAL JUDGMENTS. 423 
 
 kinds. This done, a scale of ititensity becomes obvious. 
 Those polished substances are found to be most strongly 
 dewed which conduct heat worst ; while those which conduct 
 well, resist dew most effectually.' Hence we conclude that 
 the deposition of dew is in some way connected with the 
 power which the body possesses of resisting the passage of 
 heat. 
 
 " ' But, if we expose rough surfaces instead of polished, 
 we sometimes find this law interfered with. Thus, roughened 
 iron, especially if painted over or blackened, becomes dewed 
 sooner than varnished paper ; the kind of surface, therefore, 
 has a great influence. Expose, then, the same material in 
 very diversified states as to surface,' (that is, employ the 
 Method of Difference to ascertain concomitance of varia- 
 tions,;) ' and another scale of intensity becomes at once ap- 
 parent ; those surfaces which part with their heat most readily 
 by radiation, are found to contract dew most copiously.' 
 Hence we conclude that the deposition of dew is also in some 
 way connected with the power of radiating heat. 
 
 " ' Again, the influence ascertained to exist of substance 
 and surface leads us to consider that of texture : and here, 
 again, we are presented on trial with remarkable differences, 
 and with a third scale of intensity, pointing out substances 
 of a close firm texture, such as stones, metals, etc., as un- 
 favorable, but those of a loose one, as cloth, velvet, wool, 
 eider-down, cotton, etc., as eminently favorable to the con- 
 traction of dew.' Looseness of texture, therefore, or some- 
 thing which is the cause of that quality, is another circum- 
 stance which promotes the deposition of dew ; but this third 
 cause resolves itself into the first, viz., the quality of resist- 
 ing the passage of heat ; for substances of loose texture ' are 
 precisely those which are best adapted for clothing, or for 
 impeding the free passage of heat from the skin into the air, 
 so as to allow their outer surfaces to be very cold, while they 
 remain warm within.' 
 
 " It thus appears that the instances in which much dew 
 is deposited, which are very various, agree in this, and, so 
 far as we are able to observe, in this only, that they either 
 radiate heat rapidly or cond act it slowly : qualities between
 
 424 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 which there is no other circumstance of agreement, than 
 that by virtue of either, the body tends to lose heat from the 
 surface more rapidly than it can be restored from within. 
 The instances on the contrary, in which no dew, or but a 
 small quantity of it, is formed, and which are also extremely 
 various, agree (as far as we can observe) in nothing except in 
 not having this same property." We can now revert to our 
 previous inquiry, as to whether the coldness was the cause of 
 dew, or its effect. " This doubt we are now able to resolve. 
 We have found that, in every such instance, the substance 
 on which dew is deposited is one which, by its own properties 
 or laws, would, if exposed in the night, become colder than 
 the surrounding air. The coldness, therefore, being accounted 
 for independently of the dew, while it is proved that there is 
 a connection between the two, it must be the dew that de- 
 pends on the coldness ; or, in other words, the coldness is the 
 cause of the dew. 
 
 " This law of causation, already so amply established, ad- 
 mits, however, of efficient additional corroboration in no less 
 than three ways. First, by deduction from the known laws 
 of aqueous vapor when diffused through air, or any other gas. 
 ... It is known by direct experiment that only a limited 
 quantity of water can remain suspended in the state of vapor 
 at each degree of temperature, and that this maximum grows 
 less and less as the temperature diminishes. From this it 
 follows, deductively, that if there is already as much vapor 
 suspended as the air will contain at its existing temperature, 
 any lowering of that temperature will cause a portion of the 
 vapor to be condensed, and become water. But, again, we 
 know deductively, from the laws of heat, that the contact of 
 the air with a body colder than itself, will necessarily lower 
 the temperature of the stratum of air immediately applied to 
 its surface ; and will therefore cause it to part with a portion 
 of its water, which accordingly will, by the ordinary laws of 
 gravitation or cohesion, attach itself to the surface of the 
 body, thereby constituting dew. This deductive proof has 
 the advantage that it accounts for the exceptions to the occur- 
 rence of the phenomenon, the cases in which, although the 
 body is colder than the air, yet no dew is deposited ; by show-
 
 CHAP. II.] GENERAL JUDGMENTS. 425 
 
 ing that this will necessarily be the case when the air is so 
 under-supplied with aqueous vapor, comparatively to its 
 temperature, that even when somewhat cooled by the contact 
 of the colder body, it can still continue to hold in suspension 
 all the vapor which was previously suspended in it : thus in 
 a very dry summer there are no dews, in a very dry winter 
 no hoar-frost. 
 
 " The second corroboration of the theory is by direct ex- 
 periment, according to the canon of the Method of Differ- 
 ence. We can, by cooling the surface of any body, find in all 
 cases some temperature at which dew will begin to be de- 
 posited. We can, it is true, accomplish this only on a small 
 scale ; but we have ample reason to conclude that the same 
 operation, if conducted in Nature's great laboratory, would 
 equally produce the effect. 
 
 " And finally, even on that great scale we are able to 
 verify the result. The case is one of those rare cases, as 
 we have shown them to be, in which Nature works the 
 experiment for us in the same manner in which we ourselves 
 perform it ; introducing into the previous state of things a 
 single and perfectly definite new circumstance, and manifest- 
 ing the effect so rapidly that there is not time for any other 
 material change in the pre-existing circumstances. ' It is 
 observed that dew is never copiously deposited in situations 
 much screened from the open sky, and not at all in a 
 cloudy night ; but if the clouds withdraw even for a few min- 
 utes, and leave a clear opening, a deposition of dew presently 
 begins, and goes on increasing.' . . . The proof, therefore, is 
 complete, that the presence or absence of an uninterrupted 
 communication with the sky causes the deposition or non- 
 deposition of dew. Now, since a clear sky is nothing but the 
 absence of clouds, and it is a known property of clouds, as of 
 all other bodies between which and any given object noth- 
 ing intervenes but an elastic fluid, that they tend to raise or 
 keep up the superficial temperature of the object by radia- 
 ting heat to it, we see at once that the disappearance of 
 clouds will cause the surface to cool ; so that Nature, in this 
 case, produces a change in the antecedent by definite and 
 known means, and the consequent follows accordingly : a
 
 426 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 natural experiment which satisfies the requisitions of the 
 Method of Difference." 
 
 II. LAWS CONCERNING .POSSIBLE THINGS. 
 
 I. We see that this process is of considerable length ; for 
 it requires the collection, selection, and comparison of many 
 instances. Further than this, it usually happens that the 
 more general the law, the more time is required to obtain it ; 
 for it requires the preliminary discovery of many partial 
 laws ; Newton, Geoffrey, Saint-Hilaire, Dalton, Faraday are 
 but the successors of many others, and the most extensive 
 inductive law we are acquainted with, that which states the 
 Conservation of Force, is of yesterday's discovery.* Again, 
 however well-established and verified one of these laws may 
 be, if we wish to apply it outside of the little circle of space 
 and short fragment of duration to which our observations are 
 limited, it becomes probable only. It is not absolutely cer- 
 tain that the Law of Gravitation continues to hold good, be- 
 yond the furthest nebulae of Herschel. It is not at all cer- 
 tain that, in the sun, hydrogen and oxygen preserve the 
 chemical affinity which we find they have herewith us. It is 
 possible that the intense temperature in the sun, that some 
 unknown circumstance beyond the furthest nebulas, may in- 
 tervene to alter or annul these laws. Consequently, on con- 
 sidering the proposition enouncing it, we find, on the one 
 hand, that its acquisition is tardy, on the other, that its ap- 
 plication is limited. 
 
 II. Such are the distinctive characteristics of the general 
 proposition whose component ideas, being formed by extrac- 
 tion and gradually adjusted to the general characters of real 
 things, are bound to correspond with their object. Very dif- 
 erent are the distinctive characteristics of the general prop- 
 ositions whose component ideas, being formed by construc- 
 tion, are not subject to a similar obligation. Such are the 
 ideas of arithmetic, of geometry, of pure mechanics, of all 
 
 * See, as to the order of these discoveries, the valuable work of Dr. Whewell. 
 on the " History of the Inductive Sciences."
 
 CHAP. II.] GENERAL JUDGMENTS. 427 
 
 the mathematical sciences, and, more generally, of all the de- 
 ductive sciences. The propositions of these sciences are not 
 merely probable, but certain beyond our little world ; at all 
 events, we believe it to be so, and, moreover, are unable to 
 believe or conceive that it is otherwise. Even beyond the 
 furthest nebulae, two facts or objects added to three facts or 
 objects of the same class make five facts or objects of the 
 same class ; if a triangle be found there, its angles are, as with 
 us, together equal to two right angles ; if a body be impelled 
 by two forces whose directions form an angle, it will move, 
 as with us, along their diagonal. At all events, whatever 
 effort we may make to conceive the contrary, we cannot do 
 so ; the two component ideas of the proposition, once well 
 understood, form in our mind an indissoluble couple whose 
 terms, in themselves, refuse separation. Besides, the most 
 general of these propositions are the ones which are first dis- 
 covered ; for it is by their means that we prove the less gen- 
 eral ones. Looked at geometrically, the idea of a solid is less 
 general than that of a surface, and that of a surface less gen- 
 eral than that of a line, since the solid is constructed with 
 surfaces, and the surface with lines, whence it follows that 
 we find, mentally at least, if not in nature, the surface with- 
 out the solid, and the line without the surface, but never the 
 solid without the surface, or the surface without the line ; so 
 that the surface occurs more frequently than the solid, and 
 the line more frequently than the surface. Now we all know 
 that, to establish propositions relating to solids, we must 
 first establish those relating to surfaces, and that, to establish 
 propositions relating to surfaces, we must first establish those 
 relating to lines. Finally, among the most general of these 
 propositions, there are certain ones, called axioms, which we 
 do not demonstrate, and by which we demonstrate the rest. 
 We fix them at the head of every science, like hooks from 
 which the other propositions may depend. These others are 
 so many links, forming one or more chains ; each link in them 
 is hung from the one preceding it, and sustains the one suc- 
 ceeding it ; but the supports which bear the whole are two, 
 three, or four expressed or implied propositions, placed at 
 the summit. If we do not demonstrate them, it is because
 
 428 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 we pronounce them evident in themselves ; at least, it seems 
 to the attentive reader that he requires no proof to admit 
 them, but that it is enough for him to understand them. As 
 soon as the two component ideas of the proposition are clear 
 to his mind, they become mutually attached there, and form 
 a couple ; this reciprocal consolidation is instantaneous ; every 
 one sees at first sight that, among all the lines drawn from 
 one point to another, the straight line is the shortest. So, 
 too, in every other deductive science, there are certain primi- 
 tive ideas which, once present in the mind, become fitted to 
 one another as speedily, with as invincible a link, with as un- 
 contested authority. Here, indeed, are propositions fashioned 
 in a strange way, and these are what we are now about to 
 examine. 
 
 III. For propositions of this kind, there are two kinds of 
 proof: the one, experimental, inductive, approximative, and 
 slow ; the other analytical, deductive, precise, and short ; it 
 is this last of which we avail ourselves in all the sciences of 
 construction. The better to mark out the characters and con- 
 trasts of these two kinds of proofs, the reader must allow me 
 to make a supposition. Take a proposition closely bordering 
 on an axiom, that truth of elementary geometry that, in every 
 triangle, the sum of the angles is equal to two right angles. Let 
 us imagine a man not a geometrician, and incapable, by the 
 structure of his brain, of becoming one, but very patient, very 
 precise, and very skilful at induction. I put in his hand a semi- 
 circle divided into minutes and degrees so as to measure an- 
 gles ; I trace before him a number of triangles ; I teach him 
 to trace others, and I ask him to investigate whether, in all 
 these triangles, the sum of the angles is not equal to a certain 
 number of right angles. For several days, he applies his semi- 
 circle to the angles of three or four hundred triangles ; in 
 each case, he observes by his semicircle the magnitudes of the 
 three angles, and, by adding their values, invariably finds 
 that their sum amounts to 180, that is, to two right angles. 
 This interests him, and he attempts to discover the partial 
 laws of which this law, obtained by the collection of agree- 
 ments, is the total. He first takes triangles having one right 
 angle ; the sum of the other two angles is then equal to one
 
 CHAP. II.] GENERAL JUDGMENTS. 429 
 
 right angle, and it will be easier to find the circumstance which 
 causes this equality. He goes to work again with his semi- 
 circle, and proves that, as the first of these two angles ap- 
 proaches a right angle in magnitude, the second of them dif- 
 fers from a right angle in magnitude, so that the diminution of 
 the one is compensated by the augmentation of the other, 
 and that, by means of this perpetual compensation, the sum 
 of the two angles is always equal to a right angle. He then 
 takes other triangles having an angle of the same magnitude ; 
 then, measuring this angle, he calculates by subtraction the 
 value which the two other angles must together have to form 
 with it a magnitude equal to two right angles. Then apply- 
 ing once more his semicircle, he proves that, whenever the 
 first of these two angles approaches the required amount, the 
 second proportionately differs from it, in such a way that, the 
 loss being equal to the gain, the sum of the two angles is al- 
 ways equal to the required magnitude. Thus, in all triangles, 
 when one angle is given, the diminutions or augmentations 
 which one of the two remaining angles may undergo are com- 
 pensated by equal augmentations or diminutions of the other 
 remaining angle ; and compensated in such a way that the 
 total magnitude of the two remaining angles is the magnitude 
 requisite to form with the given angle a number of angles 
 equal to two right angles. When this is effected, our in- 
 quirer has found a fixed connection between the values of the 
 second and third angle, another fixed connection between the 
 sum of these values and the value of the first angle, and, by 
 these two connections, he explains the whole value of the 
 three angles. But he has reached his limit, he can go no 
 further. Besides this, after all these measurements, additions, 
 subtractions, and recapitulations, he has grounds of doubt ; 
 he must ask himself whether the triangles he has drawn are 
 absolutely perfect, if the divisions of his semicircle are strictly 
 equal, whether, in applying his semicircle to the angles, he 
 has made the lines of division- coincide exactly with the sides 
 of the angles. Let him use a powerful microscope ; he will 
 find that in very few cases are these conditions fulfilled, and 
 he must suppose that, if the microscope were more powerful, 
 he would not find them fulfilled in any case. Therefore, all
 
 430 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 he can affirm is that, in triangles apparently perfect, the sum 
 of the three angles is apparently equal to two right angles. 
 Now, let the geometrician come in ; he draws one triangle 
 only; in fact, he does not busy himself with this or any other 
 figured triangle ; his object is any triangle whatever ; he ex- 
 pressly tells us this; to him, the apparent figure is but a 
 means of more readily effecting a mental construction ; his 
 eyes follow on the board or paper ideal lines, to which the 
 physical marks do but approximately correspond. He com- 
 pletes his mental construction and his apparent figure, by 
 drawing through the vertex of the triangle and parallel to the 
 base, on the one hand, an ideal line, on the other, a physical 
 mark, so that between this mark and line there is a rough cor- 
 respondence. Having completed his mental construction, he 
 resumes his definitions of the triangle and of parallel lines, he 
 observes their elements, he follows with his finger these ele- 
 ments in the approximating mark, he finds in one or more of 
 them the property he is in search of, and thus proves the the- 
 orem by the analysis of his definitions. 
 
 Axioms are analogous theorems, but we dispense with 
 their proof, either because it is very easy or because it is very 
 difficult. In other words, they are analytical propositions, the 
 subject of which contains the attribute, either, in a very evi- 
 dent manner, which renders the analysis useless, or, in a very 
 hidden manner, which renders the analysis almost impracti- 
 cable. Hence there are two kinds of axioms, which border 
 on one another by transitions. 
 
 At the foot of the scale are some which seem insignifi- 
 cant ; this arises from the required analysis being completely 
 effected ; the terms of the attribute are found before-hand in 
 the terms of the subject ; the reader does not find the propo- 
 sition instructive ; he says that he has been told the. same 
 thing twice over. Such are the celebrated metaphysical 
 axioms of identity and contradiction. The first may be thus 
 expressed : if, in an object, there be a certain datum present, 
 that datum is present. The second may be formulated thus : 
 if, in an object, there is a certain datum present, that datum 
 is not absent ; if, in an object, there is a certain datum absent, 
 that datum is not present. As the words, present and not ab-
 
 CHAP. II.] GENERAL JUDGMENTS. 43 r 
 
 sent, absent and not present are synonymous, it is plain that in 
 the axiom of contradiction as well as in the axiom of identity, 
 the second half of the phrase repeats a portion of the first ; it 
 is a repetition ; we have manoeuvred without gaining ground. 
 Thence we get a third metaphysical axiom, that of the 
 alternative, less empty than the preceding ones ; for a short 
 analysis is required to prove it ; we may enounce it in these 
 terms : in every object, a particular datum is either present 
 or absent. In fact, suppose the contrary, that is to say, that 
 the datum may be neither absent nor present in the object. 
 Not absent, means that it is present ; not present, means that 
 it is absent ; the two together mean, then, that the datum is 
 at once present and absent in the object, which is contrary 
 to the two branches of the axiom of contradiction, to the one 
 which says that, if a particular datum is present in an object, 
 that datum is not absent, and to the other which says that 
 if a particular datum is absent from an object, that datum is 
 not present. Let us now resume the axiom of the alterna- 
 tive, and observe the attitude of the mind which comes 
 across it for the first time. It is implied in a heap of propo- 
 sitions, which we explicitly admit, because we impliedly admit 
 the axiom. For instance, some one tells us that every triangle 
 is equilateral or not ; every vertebrate animal is a quadruped or 
 not. Without examining any triangle or any animal, we nec- 
 essarily recognize that these propositions are true ; the alterna- 
 tive is inevitable and cannot be evaded. And yet, in most 
 cases, we have not the proof at hand. We have not made the 
 foregoing analysis ; we could not show, as has been shown 
 above, the series of links by which the proposition is reduced 
 to the axiom of contradiction. We have not disengaged and 
 followed, as. just now, the very abstract ideas which, by their 
 delicate and continuous network, fasten together the two 
 elements of the proposition. What does this mean, except 
 that, in the absence of a clear view of this consolidation you 
 have a confused sentiment of it, and that the connection exists 
 between the two elements of your thought without your being 
 able to fix precisely on the points of connection? We see 
 daily this effectiveness of latent ideas ; we feel that a certain 
 person could not have acted in a particular way, that certain
 
 432 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 conduct would be inopportune, that a certain action is right 
 or blamable, and most frequently we cannot say why ; never- 
 theless, there is a why, a secret reason ; this reason is an idea, 
 an idea included in the total conception which we have 
 formed of this person, this conduct, this action ; it exists in 
 the total conception like a segment not marked out in a circle, 
 like a grain of lead in a pound of lead ; it is active in the 
 conception just as its associated elements ; together they 
 form a mass which, coming in contact with another mass, 
 shows sometimes an affinity resulting in union, sometimes a 
 repugnance resulting in separation. Later on, by reflection, 
 we disintegrate this mass ; by means of abstract words, we 
 isolate its component ideas ; we find one among them which 
 explains to us the involuntary junction or insurmountable 
 incompatibility of our two conceptions. That there are some 
 demonstrating ideas included in the terms of the preceding 
 axiom, we cannot doubt, since we have just detected them and 
 arranged them in proof. That undetected ideas may and must 
 act in the latent state to unite or sever two conceptions in 
 which they are included, is certain, since we are daily wit- 
 nesses of the fact. We may conclude, then, that the mental 
 consolidations and repulsions proved respecting the preceding 
 axiom, have as their cause the concealed presence of the 
 latent ideas which we just now detected, and we may con- 
 jecture that, in all similar axioms, it is the same cause 
 which produces the same effect. 
 
 IV. It would be too long, and moreover useless, to analyse 
 them all. Let us apply ourselves to those which are the 
 most fruitful, and which serve for the construction of whole 
 sciences. At the head of arithmetic, algebra, and geometry, 
 are inscribed the two following axioms : if equal magnitudes 
 be added to equal magnitudes, the wholes are equal ; if equal 
 magnitudes be taken from equal magnitudes, the remainders 
 are equal. No doubt we may form these two propositions 
 by ordinary induction, and, most probably, it was in this 
 manner that they were first established in our mind. Take 
 two flocks, each of twenty sheep, in separate inclosures ; they 
 may be increased or diminished in number ; they are, then, 
 magnitudes. I drive fifteen sheep into the first inclosure,
 
 CHAP. II.] GENERAL JUDGMENTS, 433 
 
 and fifteen other sheep into the second ; I then count the 
 two flocks so increased, and find that, in each field, there are 
 thirty-five sheep. I then take seventeen sheep from the first 
 inclosure, and seventeen others from the second ; I then count 
 the two flocks so diminished, and find that, in each field, 
 there are eighteen sheep. As often as I have performed 
 similar operations, under similar conditions, upon any number 
 of any kind of animals, or, more generally, upon any collec- 
 tion of any distinct objects or facts, I have verified that the 
 result was similar. The same observation is made when the 
 collection is no longer composed of natural individuals, like a 
 sheep, a pebble, or of facts naturally distinct, like a sound, a 
 blow, a sensation, but of artificial individuals, like a metre, a 
 litre, a gramme, or of facts artificially divided, like the suc- 
 cessive parts of a continuous movement. For instance, here 
 are two vessels in each of which are six litres of water ; I 
 pour three litres of water into the first, and three litres of 
 water into the second ; I then measure the two quantities of 
 water so increased, and find, in each vessel, nine litres of 
 water. I then draw five litres of water from the first vessel, 
 and five litres from the second, and find there is left, in each 
 vessel, four litres of water. Each of these cases is an experi- 
 ment. A child does the same with marbles ; if he has 
 counted two large equal heaps, and adds to them two little 
 heaps which he has also counted and found equal, and finds, 
 on counting, that the whole heaps are equal, this will be a 
 discovery for him, and I imagine that he will be as much 
 delighted at it as a physicist who has observed for the first 
 time some unknown phenomenon. After many similar ex- 
 periments, we are able inductively to conclude, by the method 
 of Agreement, that equal magnitudes added to equal magni- 
 tudes give equal sums, and that equal magnitudes taken from 
 equal magnitudes give equal remainders. For if sometimes, 
 as in the experiment made with vessels of water, the sums or 
 remainders are not rigorously equal, we may legitimately 
 attribute this inequality to the inaccuracy of our preliminary 
 measures or the awkwardness of our subsequent manipulation, 
 since the more accurate our measures and the more skilful 
 our manipulation, the smaller does the inequality become. 
 28
 
 434 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Besides, to strengthen our conclusion, we have at hand 
 another inductive method, that of Difference. As soon as we 
 suppress the equality of the primitive magnitudes or of the 
 added magnitudes, the equality of the obtained wholes disap- 
 pears. As soon as we suppress the equality of the primitive 
 magnitudes, or of the magnitudes taken away, the equality of 
 the subsisting remainders disappears. These two first equali- 
 ties, then, are the antecedent of the third, as the third is the 
 consequent of the two first ; and we have a couple in which 
 the two terms, obtained like cooling and dew, are connected, 
 like cooling and dew, without exception and without con- 
 dition. 
 
 But the two axioms thus formed may also be formed in 
 another manner. In fact, let us lay aside experience, let us 
 close our eyes, and shut ourselves up in the confines of our 
 own mind ; let us examine the terms which make up our pro- 
 positions ; let us attempt to find out what it is we mean by 
 the words magnitude and equality, and let us see what men- 
 tal constructions we form, when we fabricate the idea of a 
 magnitude equal to another. Here we must distinguish be- 
 tween artificial magnitudes in which the units are natural, 
 and natural magnitudes in which the units are artificial. 
 Let us examine them in turn, and first as to natural magni- 
 tudes which we also term collections. 
 
 Take a collection of similar individuals, some flock of 
 sheep, or a collection of abstract units, some mental group of 
 pure units, pictured to the eye by the same sign many times 
 repeated. We call these collections magnitudes ; and, if W2 
 give them this name, it is because, they are capable of becom- 
 ing greater or smaller, while retaining their nature ; we mean 
 to say by this that we may, in fact or by thought, add to the 
 flock one or more sheep, add to the group one or more units, 
 take from the flock one or more sheep, take from the group 
 one or more units. Let us now compare one of these collec- 
 tions with another analogous collection* and make correspond, 
 in thought or otherwise, a first object of the first with a first 
 object of the second, a second with a second, and so on, till 
 
 Duhamel, " De la Methode dans les Sciences de Raisonnement," i. 3.
 
 C: :.-.:. II.] GENERAL JUDGMENTS. 435 
 
 one of the two be exhausted. Two cases present themselves. 
 Either the two collections are exhausted together ; the num- 
 ber of sheep is then the same in the first and in the second 
 flock, the number of units is the same in the first and in the 
 second group ; and in this case we say that the two magni- 
 tudes are equal. Equality, then, means presence of the same 
 number. Or one of the two collections is exhausted before 
 the other; the number of sheep is then different in the first 
 and second flock, the number of units is different in the first 
 and second group ; and in this case we say that the two mag- 
 nitudes are unequal. Inequality, then, means presence of two 
 different numbers. 
 
 Now, for these kinds of magnitudes, we are able to prove 
 the axiom. Let there be two equal magnitudes to which we 
 add equal magnitudes. According to the foregoing analysis, 
 this means that the first collection contains a certain number 
 of individuals or of units, that a certain number of them is 
 added to it, that the second contains the same number of in- 
 dividuals or of units as the first, that the same number of them 
 is added to it as to the first, that, in the two cases, the same 
 number is added to the same number, and that, therefore, the 
 two final collections contain the same number added to the 
 same number, that is to say, the same total number of individ- 
 uals or of units, whence it follows, from the definition, that 
 the two sums or final magnitudes are equal magnitudes. And 
 so again let there be two equal magnitudes, from which we 
 take two equal magnitudes : according to the same analysis, 
 this means that the first collection contains a certain number 
 of individuals or of units, that a certain number of them are 
 taken from it, that the second contains the same number of 
 individuals or of units as the first, that the same number of 
 them are taken from it as from the first, so that in the two 
 cases the same number is diminished by the same number, 
 and that, therefore, the two final collections contain the same 
 number diminished by the same number, that is to say, the 
 same remaining number of individuals or units ; hence it inva- 
 riably follows, from the definition, that the two remainders or 
 final magnitudes are equal magnitudes. 
 
 From artificial magnitudes, let us pass to natural. The
 
 436 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 most important of these are the geometrical, since they serve 
 as measures for all the rest : times, velocities, forces, masses, 
 etc. These geometrical magnitudes are lines, surfaces, solids ; 
 and, if we term them magnitudes, it is because they may be- 
 come greater or less ; we mean to say that, in fact or mental- 
 ly, we may add a line to a line, a surface to a surface, a solid 
 to a solid. Let us now compare a line with a line, or a surface 
 with a surface, and apply, in thought or otherwise, the second 
 to the first, taking care in doing so not to alter the second in 
 any way. Here, as before, two cases present themselves. Ei- 
 ther the second coincides exactly and completely with the first, 
 so as to become absolutely confounded with it ; in this case, 
 the two lines form only one and the same line ; we then say 
 that the two magnitudes are equal. To say, then, that two 
 magnitudes are equal, is to say that after the application, in 
 other words, when omission and abstraction are made of the 
 two distinct positions, the two lines, surfaces, etc., are the 
 same. Or else, the second line does not exactly and completely 
 coincide with the first : in which case the two lines, not being 
 confounded, remain different, we then say that the two magni- 
 tudes are unequal. To say, then, that two magnitudes are 
 unequal, is to say that after the application, in other words, 
 when omission and abstraction is made of their two distinct 
 positions, the two lines, surfaces, etc., are different. 
 
 Now we can also prove the axiom for these kinds of mag- 
 nitudes. Let there be two equal magnitudes added to two 
 equal magnitudes. According to the foregoing analysis, this 
 means that a certain primitive line, surface, etc., is given, that 
 a complementary one is added to it, that a second primitive 
 line, when its distinct position is omitted, is the same as the 
 first line, that to it is added a complementary line, the same, 
 except as to its distinct position, as the other complementary 
 line, that in the two cases, when abstraction is made of the 
 distinct positions, the same line is added to the same line, and 
 that, therefore, the two completed lines are the same line 
 added to the same line, that is to say, the same total line, 
 hence it follows, from the definition, that the two sums or 
 total magnitudes are equal. And so again, let two equal mag- 
 nitudes be taken from two equal magnitudes. According to
 
 CHAP. II.] GENERAL JUDGMENTS. 437 
 
 the same analysis, this means that a certain primitive line, 
 surface, etc., is given, that a portion of it is cut off, that a sec- 
 ond primitive line is, when its position is omitted, the same 
 as the first, that from it is cut off a portion, which, except as 
 to its distinct position, is the same as the other portion cut off, 
 that, in the two cases, when abstraction is made of the dis- 
 tinct positions, the same line is taken from the same line, and 
 that, therefore, the two diminished lines are the same line 
 diminished by the same line, that is to say, the same remaining 
 line, hence, it follows, from the definition, that the two re- 
 mainders or final magnitudes are equal. We might demon- 
 strate in the same way a third axiom, which is true of nat- 
 ural magnitudes as well as of artificial, that is to say, that two 
 magnitudes each of which is equal to a third magnitude are 
 equal to one another. 
 
 Let the reader take the pains to examine the artifice of 
 this proof. By thought, and with the auxiliary confirmation 
 of sensible facts, we make two artificial magnitudes corre- 
 spond, feature for feature, or we make two natural magnitudes 
 coincide, element for element ; if this correspondence or coin 
 cidence are absolute, the idea of equality arises in us. We 
 have watched its birth and distinguish its foundation ; it com- 
 prises a more simple element and is reduced to the idea of 
 sameness ; in fact, in a certain aspect, when what it is neces- 
 sary to omit is omitted, the two magnitudes become the same. 
 Consequently, in the inverse aspect, when what it is necessary 
 to add is added, the same magnitude is transformed into two 
 equal magnitudes. Cut away from the two magnitudes their 
 distinctive characteristics, from the two equal artificial mag- 
 nitudes the property of belonging to two distinct collections, 
 from the two equal natural magnitudes the property of having 
 distinct positions ; they become the same magnitude. Con- 
 versely, take the same magnitude twice and attach it succes- 
 sively to two distinct collections or to two distinct positions ; 
 it will be transformed into two equal magnitudes. Under the 
 word equal dwells the word same ; here we have the essential 
 word ; this is the latent idea included in the idea of equality 
 When severed and followed through several intermediate prop- 
 ositions, it reduces the axiom to an analytical proposition.
 
 438 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 By means of it we connect the attribute to the subject ; we 
 see the idea present in both ; but, before we saw it there, we 
 had a presentiment that it was there ; it was actually there, 
 and evidenced its presence by the constraint it exercised on 
 our affirmation ; though not detected, it performed its office ; 
 We felt indeed that two magnitudes being equal might, by 
 that alone, be substituted for one another, that, therefore, the 
 aukmentation or diminution undergone by the second might 
 be substituted for the corresponding augmentation or diminu- 
 tion undergone by the first. We divined with certainty, but 
 without the power of stating the matter precisely, that in the 
 two data and in the two operations, there was something of 
 the same ; the analysis has only isolated this same thing, and 
 has shown us in a distinct state the virtue it possessed in us 
 in the latent state. 
 
 V. There are twelve axioms of this kind at the commence- 
 ment of Euclid's geometry ; many of them are reduced to 
 preceding ones ; others, comprising the ideas of whole, of 
 part, of greater, of less, are easily demonstrated from the pre- 
 liminary definition of these terms.* The last and more im- 
 portant ones deserve to be studied apart ; they are the ones 
 concerning the straight line and parallel lines. Let us first 
 observe that the usual definition of the straight line is a bad 
 one ; we say that it is the shortest which can be drawn from 
 one point to another. This is not a primitive property, but 
 a derived property ; we do not, in conceiving it, watch the 
 generation of the line ; we do not possess the elements of the 
 mental construction ; we do but hold one of its consequences. 
 Besides, " this definitionf reduces a notion to others which 
 we do not possess and which are much less simple than the 
 first. What in fact do we understand by a line being less 
 short or greater than another ? It is that this line is made 
 up of a part equal to the first and of a remainder of some kind. 
 Now, two equal lines are those which may coincide, and con- 
 
 * Read as to this, Duhamel, op. cit. ii. 3-6. Equal angles are defined by the 
 coincidence of their sides ; the perpendicular by the equality of the two adjacent 
 angles it makes ; the right angle by the perpendiculars, which form its sides. 
 
 f Duhamel, op. cit. p. 7.
 
 CHAP. II.] GENERAL JUDGMENTS. 439 
 
 sequently, equality cannot be conceived between two lines 
 whose figure does not admit of superposition," which is the 
 case with the straight line referred to the other indefinitely 
 numerous broken or curved lines with which it would be nec- 
 essary to compare it in order to verify that it is shorter than 
 any of them. This is not the way in which the acute and sub- 
 tle Greek analysts have defined the straight line ; Euclid does 
 not admit at the outset that it is the shortest line between 
 two points ; he proves it later on, by comparing triangles of 
 which it forms a side, which prove it to be shorter than any 
 broken line, then, by extending the case of the broken line to 
 that of the curve which forms its limit. We must seek then 
 for another definition, and, according to our custom, watch 
 its construction. Now we constructed it by considering two 
 given points, and by observing the line described by the first 
 point when it moves towards the second and towards the sec- 
 ond only, as opposed to the line described, when, before mov- 
 ing towards the second, it moves towards another or several 
 other points, which produces a broken line, or, towards an in- 
 finite series of other points, which produces a curved line. 
 We thus see that, in the straight line drawn from a point, the 
 whole line, that is to say the straight line itself, being solely 
 and completely determined by its relation with one second 
 point alone, all its characters, whatever they may be, known 
 or unknown, are solely and completely derived from the rela- 
 tion it has with this second point alone. 
 
 Hence, two consequences, one relating to the whole line, 
 the other relating to its various parts. If we start from the 
 same first point, and trace another line which also moves to- 
 wards the same second point, and towards this only, this 
 second line does but exactly repeat the first ; for all its char- 
 acters, like all those of the first, are completely and solely 
 derived from the relations which, like the first, it has with 
 this second point alone ; hence we see that the characters of 
 the two lines, whatever they may be, known or unknown, are all 
 absolutely the same, in other words, that these two lines are 
 confounded together and form but one:* this we express in 
 
 * An entirely analogous demonstration shows that two circumferences whose 
 radii are equal become confounded into one single one.
 
 <4O THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 various ways, by saying that between two points we can only 
 draw one straight line, that two points are sufficient to de- 
 termine the interposed straight line, that two straight lines 
 having two points in common coincide in all their interme- 
 diate extent, and from this, we easily deduce that two straight 
 lines which cut one another cannot enclose a space.* So 
 much for the whole line ; let us now consider its various 
 parts. Since the entire line described is completely and 
 solely determined by its relation to the second point and de- 
 rives thence all its characters, each of its constituent portions 
 is solely and completely determined by the same relation and 
 also derives thence all its characters, excepting one, namely 
 the property of being one particular portion and not 
 another, situated at some spot or other of the line, at its 
 commencement, its middle, or its end. Consequently, if we 
 make abstraction of this particularity, all the portions of the 
 line have exactly the same characters, in other words, they 
 are the same. Let us effect this abstraction, and, for this, 
 suppress the particular position of a fragment of the line, by 
 taking it from the spot at which it is, for instance the end, 
 by transferring it elsewhere, for instance to the beginning, 
 and there applying it to the whole line. It will be con- 
 founded with the portion on which it is applied, and the two 
 fragments will make one only. Hence it follows that any 
 portion of the straight line, taken from its position and ap- 
 plied to any other portion of the whole line, will rigorously 
 coincide with the portion to which it is applied.f 
 
 When this is settled, we know the relation of any portion 
 whatever of the straight line to any other portion whatever 
 of this same line, and are consequently able to follow it, be- 
 yond the two points through which we have drawn it, up to 
 an infinite distance. In fact, take a straight line A B, pro- 
 long it to any distance beyond the point 
 
 -^ ' B, put in such a way that it remains 
 
 straight, that is to say in accordance 
 
 * This last proposition is the I2th axiom of Euclid. 
 
 \ An analogous demonstration shows that, in the same circle or in equal cir- 
 cles, any arc transferred from its place, will exactly coincide with the portion of 
 circumference on which it may be placed. This arises from the circumference 
 ei.i -, like the straight lin<* ?> ""iform line.
 
 CHAP. II.] GENERAL JUDGMENTS. 441 
 
 with the preceding condition, in such a way that any one of its 
 portions may coincide with any other of its portions, therefore 
 with all those which are comprised in its prolongation. Now, 
 suppose a second straight line traced from A to B, and also 
 prolonged to any distance ; we have already proved that be- 
 tween A and B it will coincide with the first, but we must 
 further prove that, beyond B, however far we may prolong 
 it, it will coincide with the prolongation of the first line. For, 
 let us assume that at some point or other it ceases so to coin- 
 cide, and that, on leaving the point C, for instance, it diver- 
 ges above or below the first ; then let us take a portion of 
 the line drawn common to the two lines, A B for instance, 
 and apply it to the first line, at the point C, so that it may 
 extend beyond that point in both directions. Since the first 
 line is straight, this portion will coincide on both sides of C with 
 a fragment of the first line to which it has been applied. Since 
 the second line is assumed to be straight, this same portion 
 must also coincide on both sides of C with the fragment of 
 the second line to which it has been applied. But this is 
 contradictory, since beyond C, the second fragment diverges 
 from and ceases to coincide with the first. There is, then, a 
 contradiction in the second line being straight and ceasing to 
 coincide with the first. Its divergence excludes its straight- 
 ness, and its straightness its divergence. If it has ceased to 
 coincide with the first, it is from its having ceased to be 
 straight ; in order for it to remain straight, it must con- 
 tinue to coincide with the first ; in order for it always to re- 
 main straight, it must always continue to coincide with the 
 first. Consequently, two straight lines which have two points 
 in common coincide throughout all their extent, to whatever 
 distance they may be prolonged ; or again, two points are 
 sufficient completely to determine in a straight line, not 
 merely the portion joining them, but also the whole entire 
 line prolonged to any distance in both directions. 
 
 " The definition and properties of the straight line," said 
 D'Alembert,* " are the stumbling-block, and, so to speak, the 
 scandal of elementary geometry." If I am not mistaken, we 
 
 * Melanges. Eclaircissements sur les Elements de Philosophic, v. 207.
 
 442 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV 
 
 have now seen that this scandal may disappear, and that the 
 assumed axioms are theorems capable of proof. According 
 to D'Alembert, parallel lines present an analogous difficulty. 
 It is rash, no doubt, to approach an obstacle which great 
 minds and specialists have pronounced unsurrnountable or un- 
 surmounted ; but here, happily, it is less a question of discov- 
 ering a demonstration than of analyzing a construction ; we are 
 doing the work of psychologists rather than of geometricians ; 
 we are simply searching for the inner secret process by which, 
 beneath the accessory and insufficient testimony of the eyes, 
 we base the unshakable conviction of the mind. How do we 
 form the notion of two parallel lines ? The usual method is, 
 to erect a perpendicular at any point of a straight line lying 
 in a plane, and another perpendicular at another point ; these 
 two perpendiculars are said to be parallel to one another.* 
 Now, what is there primitive in this construction ? Nothing, 
 except that we suppose two straight lines, each of them per- 
 pendicular to a third line, denoting by the name perpendicu- 
 lar the straight line which, standing on another straight line, 
 makes the adjacent angles equal to one another ; it is from 
 this construction that all the properties of parallels must be 
 deduced. Now, what are these properties? We perceive 
 that, in these two perpendiculars compared to one another, 
 there is something the same ; in fact, each of them forms with 
 the base the two same right angles ; and, in consequence, one 
 of the two with its angles, applied to the other, will coincide 
 completely with the other and its angles. They are, then, ex- 
 cept in one circumstance alone their position at two different 
 points of the base the same ; and this partial identity, pro- 
 vided we know how to follow it, must be manifested by pre- 
 cise consequences. Let us conceive the whole portion of the 
 base intercepted by their feet to mount, with uniform motion, 
 remaining rigid and in such a way that one of its elements 
 traces, in rising, a perpendicular to the base. Since it is a 
 straight line, all its elements are similar ; except in their dis- 
 tinct position, they are, as we have seen, the same element : 
 
 * D'Alembert proposes another construction, very analogous, but somewhat 
 less simple. Op. cit., p. 202.
 
 CHAP. II.] GENERAL JUDGMENTS. 443 
 
 hence, it follows that, in their common ascent, they will all of 
 them trace similar straight lines that is to say, the same with 
 the exception of their distinct position ; hence, it finally fol- 
 lows that, as one of these lines is perpendicular, all the rest 
 will be. This is why, if the extremity A traces 
 a perpendicular in its ascent, the extremity B 
 will trace another, and the line A B will, in its 
 ascent, have traced two perpendiculars at A and 
 B. But since it is always the same line A B A B 
 
 which ascends, it will be everywhere the same at all points of 
 its course, and as it is this line which measures the distance 
 of the two perpendiculars, this distance will always be the 
 same at all points of the course. Hence it follows that the 
 distance of the two perpendiculars invariably remains the 
 same, and has as its measure the portion of the base inter- 
 cepted by their feet ; hence it follows, a fortiori, that the two 
 perpendiculars, having a distance invariably between them, 
 will never meet. 
 
 This is, in my opinion, the secret mental operation which 
 sustains and clears up the evidence of our senses, when we 
 prove, or imagine that we prove, by the eye that the two per- 
 pendiculars will always maintain the same distance from one 
 another. We have better reason for admitting this, than the 
 approximately equal durations of the sensations experienced 
 through our ocular muscles. We have no need to apply re- 
 peatedly the same measure to one of the perpendiculars, to 
 note with a pencil the distance indicated by the first measure- 
 ment, to compare it with those indicated by subsequent 
 measurements, and to verify, by recapitulation, that all the 
 measurements agree in indicating equal distances. The 
 mind admits this equality on the spot, but because it has it- 
 self created the equality, it creates the equality by causing 
 the same intact line to ascend, and also to descend ; it is vaguely 
 conscious that, at the commencement and conclusion of its 
 construction, this line is the same ; this is the silent reminis- 
 cence which is added to the suggestion of the eye and antici- 
 pates the verifications of the measure, to render useless the 
 employment of the measure, and to confirm, by stronger evi- 
 dence, the insufficient testimony of the eye.
 
 444 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Such is not the case with the second principal proposition 
 relating to parallel lines, and which is termed Euclid's 
 postulate. It is in fact a postulate, and not an axiom. It 
 
 consists in saying that, if a line 
 M B cuts obliquely the first par- 
 allel D N, it will also meet the 
 second parallel O C. We have no 
 difficulty in seeing the necessary 
 and sufficient condition of this 
 meeting. It is necessary and suf- 
 ficient for the cutting line when 
 N prolonged beyond B to become suf- 
 
 ficiently distant from the first parallel for a perpendicular N O, 
 erected from its meeting to a point N, to be equal to A B the dis- 
 tances of the two parallels. Will the line cutting the first paral- 
 lel become sufficiently distant from it for this ? We have no 
 difficulty in showing that its distance increases in proportion 
 as it is prolonged ; for if, at any moment, this distance were to 
 diminish or to cease to increase, any two subsequent points 
 taken upon the line would be at an equal distance from the first 
 parallel line, and, as two points are sufficient to determine a 
 straight line, the cutting line would be confounded with a third 
 parallel passing through these two points, which is impossible, 
 since, by the previous proposition, two parallels cannot meet, 
 and since, by hypothesis, our oblique line meets the first par- 
 allel. In proportion, then, as the cutting line is prolonged, it 
 becomes more distant from the first parallel, and the perpen- 
 dicular which measures this distance is a continually increas- 
 ing magnitude. But our question still subsists. Will this in- 
 creasing magnitude ever, in fact, increase sufficiently to equal 
 a very great magnitude, and especially, any magnitude of any 
 extent we please, as the distance of the two chosen parallels 
 may be ? Reduced to these precise terms, the proposition 
 leaves us in a certain hesitation ; no doubt, at first sight, see- 
 ing an oblique line sensibly inclined, and two parallels moder- 
 ately distant, we decided that the oblique line, having met 
 the first, would meet the second ; the point of junction was 
 at no great distance ; we could perceive it with our eyes, or 
 note it beforehand by imagination ; on these indications, we
 
 CHAP. II.] GENERAL JUDGMENTS. 445 
 
 have inductively concluded with a show of truth that, how- 
 ever small may be the degree of inclination, and however 
 great the distance, the proposition will invariably be true. But, 
 if we suppose the distance equal to the line which joins a fixed 
 star to the earth, and the inclination simultaneously reduced 
 to the hundred millionth part of a second, our eyes no longer 
 avail us, our imagination fails, and we are disturbed. We be- 
 come still more so, if we recollect that we may further in- 
 crease the distance and diminish the inclination beyond these 
 enormous figures, and so on indefinitely. We become still 
 more unsettled when we observe that certain magnitudes in- 
 crease indefinitely, without ever being able to attain a certain 
 limit, that however enlarged and swollen, they invariably re- 
 main below a given magnitude, that the series l-f-^-f-i+J-f-re 
 etc., always remains less than 2, and that perhaps our perpen- 
 dicular is in the same position. We must employ a more del- 
 icate analysis. Let us attempt it. We have here no diffi- 
 culty in observing that the point N becomes distant from the 
 point B in proportion to the diminution of the angle made the 
 oblique line with the first parallel. We further observe that, 
 the angle remaining the same, the point N becomes distant 
 from the point B in proportion to the increase in the distance 
 of the parallels ; then, combining these observations, we con- 
 clude that B N is a magnitude whose variations depend on the 
 variations of two other magnitudes. It would be necessary 
 to give precision to this double dependence, and for this pur- 
 pose to seek a fixed relation, not between the three magni- 
 tudes, but between their parts, elements, or fractions. In 
 other words, it would be necessary to find in what proportion 
 B N would be increased by halving the angle, and then, in 
 what proportion B N would be increased by doubling the dis- 
 tance of the parallels, and consequently, in what compound 
 proportion the halving the angle and simultaneous doubling 
 the distance would together increase B N. If we could de- 
 termine exactly this relation, not only should we be able to 
 affirm that, the angle being diminished as much as we please, 
 and the distance increased as much as we please, the oblique 
 line would always meet the second parallel ; but more than 
 this, when given the angle and the distance, we should be
 
 446 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV- 
 
 able to say what would be the length of B N, and conse- 
 quently, to mark on the second parallel the precise point at 
 which the oblique line would meet it. Unfortunately, the 
 trigonometrical formulae which lead us to this are themselves 
 founded on the supposition that the oblique line meets the 
 second parallel. We are unable, then, to avail ourselves of 
 them, and Euclid's postulate remains a postulate, that is to 
 say a proposition which we are willing to admit by tolerance, 
 but which we are not forcibly compelled to give our adhe- 
 sion to, and it is the opinion of the greatest authorities among 
 geometricians, that the various demonstrations which have 
 been attempted, though sufficient to induce our assent, have 
 not the analytical rigor appertaining to theorems and to axi- 
 oms strictly so called. 
 
 VI. The reader now sees how axioms are formed. Not 
 only is the experience of the eyes or imagination an indi- 
 cation only, but moreover, this indication may, in certain 
 cases, fail ; just now we were unable, either with the exter- 
 nal or internal eye, to follow the prolongation of the two 
 parallel lines beyond a certain distance ; so again, we may 
 cite a figure such as the regular myriagon, which we have 
 never seen drawn, which we cannot draw in imagination, and 
 as to which we can, nevertheless, form certain definite judg- 
 ments. Beneath the process of the external or internal eye, 
 there is a silent mental process, the repeated or continuous 
 recognition of a circumstance which, supposed in the primi- 
 tive construction, persists or reappears, always the same, at 
 the various successive moments of our operation. When, 
 after having erected my two perpendiculars on a base, I fol- 
 low them indefinitely in imagination without being able to 
 admit that at some point or other of their course they ap- 
 proach one another, it is because, involuntary and unawares, 
 I carry with them the portion of base intercepted by their 
 feet, and because, at every moment of the transit, this base, 
 which is always the same in my mind, makes itself vaguely 
 recognized by my mind as being always the same. But 
 though reason may be the real fabricator of the final convic- 
 tion, the indication furnished by the senses is of great value. 
 For the testimonies of the eye and the imagination antici-
 
 CHAP. II.] GENERAL JUDGMENTS. 447 
 
 pate and confirm the conclusions of the analysis ; we are led 
 to the axiom by a preliminary suggestion, and we are main- 
 tained in it by a subsequent verification. The sensible evi- 
 dence serves as introduction and complement to the logical 
 evidence, and it is by means of this agreement that arithme- 
 tic, geometry, and even algebra, having immediately found 
 their axioms, were of such early growth. This was not the 
 case with mechanics. In this science, the axioms do not 
 concur with the inductions of experience ; at least, they do 
 not concur with the inductions of ordinary experience. For 
 instance, axioms tel'l us that matter is inert, incapable of 
 spontaneously modifying its state, of passing from rest to 
 motion when it is at rest, and from motion to rest when it is 
 in motion. Now, we are daily seeing bodies passing from 
 motion to rest or from rest to motion, and as it seems, spon- 
 taneously, and without the appreciable intervention of a new 
 condition. A projected stone, an oscillating pendulum, finally 
 stop, and we are tempted to believe that they stop of them- 
 selves ; a mixture explodes, an apple falls from the tree, 
 without our senses detecting the new circumstance which has 
 been added to the former state and has thus produced the 
 new. Throughout the whole of antiquity and of the middle 
 ages, philosophers recognized tendencies to rest or motion, 
 various in various bodies, the tendency downwards in the 
 falling stone, the tendency upwards in air and fire which rise, 
 the tendency to perfect circular movement in the revolving 
 stars, the abhorrence of a vacuum, etc. It was at the Ren- 
 aissance only, with Stevinus and Galileo, that mechanics com- 
 menced ; and, most probably, the cause of this long delay 
 was the disagreement of ordinary induction and of pure 
 reason. In place of leading us to the axiom, experience 
 turned us from it ; instead of confirming it, experience denied 
 it. We had no assistance in forming it, and if we could 
 have formed it, observation, as then practised, would have 
 been sufficient to upset it. We have ended by forming it, 
 and experience, better directed, is now found to be in ac- 
 cordance with it. Further than this, it has been so well di- 
 rected, and, in certain cases, as that of Borda's pendulum, is 
 found so conclusive that, according to many authors, indue-
 
 448 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 tion is the only real proof of the axiom ; they look on the 
 principles of mechanics as propositions analogous to the 
 principle of attraction, established like it by pure induction, 
 limited like it by the small circle and small duration of the 
 world our observation can attain, incapable like it of being 
 applied beyond this except by conjecture, and, like it, simply 
 probable, when our rashness wishes to extend their empire 
 over all portions of space, or to all moments of time. 
 
 For ourselves, we are inclined to think, with Leibnitz and 
 D'Alembert, that among the principles of mechanics, are 
 many which are not merely truths of experience, but also 
 analytical propositions. In order to show this, let us closely 
 examine our constructions. Take a movable body moving 
 uniformly in a straight line for as short a time as we please, 
 and traversing as short a space as we please ; this is what we 
 may term its initial, or primitive movement ; will it continue 
 to move, and, if so, what will be its movement ? However 
 short may be the time first elapsed, for instance, the millionth 
 part of a second, and however small may be the space first 
 traversed, for instance, the thousandth part of a millimetre, 
 we can consider successively two halves in this time and two 
 halves in this space. As, according to our supposition, the 
 movement has been rectilinear, the second two-thousandth of 
 a millimetre described will be in a straight line with the first. 
 As, according to our supposition, the movement has been 
 uniform, the space traversed in the second two-millionth part 
 of a second is the same in magnitude with that traversed in 
 the first. Hence two consequences follow. Neither the di- 
 rection nor the velocity of the body have been changed. The 
 direction it had during the first fraction of space has remained 
 the same during the second. The velocity it had during the first 
 fraction of time has remained the same during the second. 
 Whether the fraction be the second or first, matters not ; the 
 character which forms their difference has had no influence on 
 the movement ; as regards the movement, this character has 
 been indifferent and, if I may venture to say so, null. But, 
 among the similar fractions of ulterior space and consecutive 
 duration, we may conceive one immediately following our 
 second fraction, after the second two-thousandth of a milli-
 
 CHAP. II.] GENERAL JUDGMENTS. 449 
 
 metre of traversed space, a third one, after the second two- 
 millionth of a second of time employed, a third one. This 
 third, taken in itself and compared with the second, differs 
 from it only as the second differs from the first ; it comes 
 after the second as the second comes after the first ; nothing 
 more. Hence it follows that, since the character by which 
 the second differs from the first, that is to say the property 
 of corning after it, has had no influence on the movement, 
 the character by which the third differs from the second, 
 that is to say the property of coming after it, will have no 
 influence on the movement ; as regards the movement, this 
 character will also be indifferent and null, and, as during the 
 second moment the body continued its uniform and rectili- 
 near movement, so during the third moment, without the 
 introduction of a new influential character, it will continue 
 its uniform and rectilinear movement. The same reasoning 
 will apply to the fourth, the fifth, and succeeding moments, 
 and so on to infinity. 
 
 Reduced to these terms, the proof is rigorous. It is 
 wholly founded on two observations : one being that two 
 equal and contiguous portions of space, like two equal and 
 successive portions of time, are exactly the same, excepting 
 this difference, that the second is after the first ; the other 
 being that, if this difference has not, in one instance, had any 
 effect upon the movement, this same difference will not, in a 
 second instance, have any effect upon the movement, on 
 condition that, in the second instance, it is absolutely the 
 same, and that no other new and influential difference has 
 intervened. For this we provide, by assuming that the third 
 fraction of time and space repeats the second absolutely and 
 in all respects ; that, no disturbing character being met with 
 in the second, no disturbing character will be met with in 
 the third ; that in the third space and third instant, as in 
 the second space and second instant, no foreign and influen- 
 tial character has been added to arrest, alter, hasten, or re'- 
 tard the movement ; that, the little space first traversed 
 being empty, the infinite space remaining to be traversed is 
 also empty ; that, the short duration first elapsed having 
 presented no modifying event, the infinite duration which 
 29
 
 450 THE KNOWLEDGE OF GENERAL THINGS. [BooK IV. 
 
 remains to elapse will not present one. In short, we con- 
 clude from a place to a different place, and from an instant 
 to a different instant, with authority and certainty, when 
 this difference, having manifested its absolute want of influ- 
 ence, may be considered as null with reference to the move- 
 ment, and when, every other influential difference being ex- 
 cluded by hypothesis, the two places and two instants be- 
 come rigorously the same with reference to the movement. 
 
 The reader sees without difficulty that an analogous and 
 still more simple reasoning applies to the case of a body at 
 rest ; for we have not then to take account of space, but 
 simply of time. Let a body be at rest during a time as short 
 as we please ; as this time is divisible into two halves, we 
 shall demonstrate as before that, the body having remained 
 during the second half in the same state as during the first, 
 the character by which the second half differs from the first, 
 that is to say the property it has of coming after it, has had 
 no influence on this state ; hence it follows that a third equal 
 fragment, cut off from consecutive duration, will not have 
 any influence, unless there be made to intervene some new 
 influential circumstance, some foreign effective event. This 
 is why the primitive rest will be maintained, so long as this 
 exclusion is maintained, and however short may be the initial 
 state, the body at rest, as well as the body impressed with a 
 uniform rectilinear motion, will tend to persevere indefinitely 
 in that state. 
 
 Observe the restricted range of the axiom, when thus de- 
 monstrated and understood. It does not in any way establish 
 that a body impinged on by another will assume a uniform 
 rectilinear movement, nor that a body impressed with a uni- 
 form rectilinear movement may lose it under the force of an 
 impact, and will then remain indefinitely at rest ; these truths 
 are matters of induction and experience. We are elsewhere, 
 in the pure region of abstract truths ; we no longer know 
 whether, in fact, there be any movable bodies at rest or in 
 motion ; we do but extract and follow out the consequences 
 included in an initial supposition or construction. This is why 
 simple analysis has been so far sufficient and will also be suffi- 
 cient to demonstrate two other capital propositions of median-
 
 CHAP. II.] GENERAL JUDGMENTS. 45! 
 
 ics. Take an inflexible straight line A B ; sup- 
 pose it to move altogether and in such a way 
 as always to remain parallel to its first posi- 
 tion ; after a certain time it becomes A' B' par- 
 allel to A B, and we assume this time to be a 
 second. Now suppose that, during this move- 
 ment of the whole line, a movable point, sit- 
 uated at A, is itself directed in a straight line 
 towards the point B, in such a way as to traverse, also in a 
 second, that is to say in the same lapse of time, the straight 
 line A B. We thus assume for A two simultaneous and dif- 
 ferent movements, the one common to it with the other 
 points of the line A B, the other special to itself. Observe 
 that we do not know if things happen thus in nature. There 
 is nothing to prove that our mental combination has, or even 
 can have, its counterpart in real combinations. We might im- 
 agine a state of things in which, from the very fact of a body 
 moving in one direction, it would be impossible for a portion 
 of that body to move at the same time in another direction. 
 But we have not here to trouble ourselves with what the laws 
 of real things permit or deny ; we suppose, in our movable 
 body, the independence of two simultaneous movements 
 taking place in opposite directions, reserving a verification 
 later on by experience as to whether the facts do or do not 
 adjust themselves to this conception. From our two hypoth- 
 eses, what follows? By the first it is admitted that the 
 straight line A B, mounting towards A' B', becomes, at the end 
 of a second, A' B', and that thus, at the end of a second, the 
 point B arrives at the point B'. By the second, it is admitted 
 that the movable point situated at A is transferred from A 
 to B, also in a second, without the ascent of A B interfering 
 in any way with this movement of translation. This ascen- 
 sion, then, is indifferent and mill with respect to the transla- 
 tion, and the movable point travels along A B in motion, as 
 it would along A B at rest. Hence it follows that, at the end 
 of a second, it has arrived at the extremity of A B in motion, 
 just as it would have arrived, at the end of a second, at the 
 extremity of A B at rest. But, at the end of a second, the 
 extremity of A B in motion is B 7 ; therefore, at the end of a
 
 452 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 second, the movable point is at B ; . Hence we see that having 
 started from the angle of the parallelogram it has reached the 
 opposite angle. 
 
 We have now to enquire what line it has described in this 
 transit. Two cases may present themselves, that of uniform 
 motion, and that of motion which is not uniform. We shall 
 only examine the first, the simplest of all : in this case, the 
 velocity of A B has remained the same throughout all its as- 
 cent, as also the velocity of the movable point A throughout 
 all its translation. Consequently, at the end of half a second, 
 A B is found to be exactly in the middle of 
 its whole transit, that is to say at C D, and 
 at the end of the same half second, the mov 
 able point A is found to be exactly in the 
 middle of its whole transit, that is to say at 
 S. But as A B has mounted in the mean- 
 time to C D, the point S belonging to it has 
 mounted with it, and is to be found at S', the 
 middle point of C D, as S is the middle point of A B. Very 
 simple geometrical considerations show that this point S' is 
 on the diagonal, that is to say on the straight line joining A 
 and B'. By subdividing the divisions of the second, we should 
 prove in the same way that all the other successive positions 
 of the movable point are likewise on the diagonal, hence it 
 follows that the line it describes in its whole double move- 
 ment of ascension and translation is the diagonal. Hence, a 
 very important consequence : our movable body which would 
 have described the line A B in a second, and the line A A 
 also in a second, likewise describes in a second the diagonal 
 A B'. Since, then, the times employed are the same, and the 
 spaces traversed are different, the velocity of the compound 
 movement will not be the same as the velocities of the com- 
 ponent movements, it will be. represented by the diagonal, and 
 they will be represented by the two sides of the angle, these 
 three lines being the measure of the spaces traversed in the 
 unit of time. Now, we have measured force by the greater 
 or less velocity it impresses on the same movable body. 
 Suppose now two forces applied to the preceding movable 
 body, one which,, if acting alone, would make it traverse the
 
 CHAP. II.] GENERAL JUDGMENTS. 
 
 line A B in a second, the other which, if acting alone, would 
 make it traverse the line A A', also in a second ; apply them 
 both together to the movable body ; we have just seen that 
 it will traverse the diagonal in a second. Hence it follows that 
 the resulting force, estimated by the impressed velocity, is to 
 the component forces, estimated also by the impressed veloc- 
 ity, as the diagonal is to the two sides of the angle. There- 
 fore the diagonal measures the resulting force with reference 
 to the component forces, just as it measures the compound 
 velocity with reference to the component velocities. It is now 
 sufficient to insert, in the measurement of forces, the second 
 element of force, mass, and we have already shown how this 
 idea is connected with the idea of velocity.* When we have 
 done this, we possess all the essential axioms of mechanics, 
 and we have formed them, as all other analytical propositions 
 are formed, by the simple analysis of the mental combination 
 in which they were included in a latent state. 
 
 VII. Other less fruitful axioms are also worthy of demon- 
 stration by reason of their immense range, and the prodigious 
 power they seem suddenly to confer on the human mind. 
 These are the ones relating, not to particular times compared 
 with other times, nor to particular spaces compared with 
 other spaces, but to the whole of time and the whole of 
 space. With reference to a given moment, duration is in- 
 finite in the future and the past, and we may picture it by a 
 straight line which starting from a given point is infinite in 
 both directions. With reference to a given point, space is 
 infinite, in three dimensions ; first, in length, which we picture 
 by supposing a point which moving in a straight line gener- 
 ates in two directions an infinite straight line ; then in 
 breadth, which we picture by supposing this infinite straight 
 line by moving in a direction perpendicular to its own to 
 generate on both sides an infinite surface ; lastly, in depth, 
 which we picture by supposing this infinite surface by mov- 
 ing in a direction perpendicular to itself to generate on both 
 sides an infinite geometrical solid. These are propositions 
 which we cannot prevent ourselves from holding to be true, 
 
 * Part ii., Book iv., Ch. i., p. 420 ante.
 
 454 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 and thereupon our imagination gives itself scope ; we repre- 
 sent to ourselves time and space as two infinite, uniform, in- 
 destructible receptacles. In the one are included all real 
 events, in the other, all real bodies. However long may be 
 a series of real events, for instance, the sequence of changes 
 which have occurred since the origin of our solar system, 
 however vast may be a group of real bodies, for instance, the 
 collection of all the stellar systems to which our telescopes 
 can reach, the receptacle extends still further ; however we 
 might increase the series or the group, it would always ex- 
 tend beyond them, and the reason is that the receptacle has 
 no limits. We remain startled, and ask ourselves by what 
 marvellous operation of the mind we have been able to dis- 
 cover so marvellous a property. But our astonishment is 
 diminished when we observe that the same property is met 
 with in all magnitudes, and is at an end when we find that it 
 is comprised in the definition of magnitude. Take the sim- 
 plest of all magnitudes, a collection of individuals or units, as 
 small as we please, that is to say containing two units. To 
 construct it, I have supposed two precisely similar units, that 
 is to say the same unit repeated ; I have then added the 
 second to the first, I to i, supposing the second unit to be 
 the same before as after the adjunction, in other words, that 
 the second I, when added, remains intact and absolutely such 
 as before. Since the second I is the same as the first, I may, 
 when it is alone, perform on it the operation which I have just 
 performed on the first, and therefore add to it I. Since the 
 second I, after its adjunction to the first, remains absolutely 
 such as it was before, I may add I to it when it is added to 
 the first, just as I added I to it when it was alone. I may 
 then add i to I -f i, that is to say to 2, just as I have already 
 added I to I. An analogous reasoning shows that we may 
 similarly add i to 3, then to 4, to 5, to 6, and in general, to 
 any number whatever. Thus every adjunction we effect 
 generates the possibility of another similar adjunction ; hence 
 it follows that the series of numbers is absolutely infinite. 
 There is no number, however enormous, which may not be 
 comprised in this series ; it is, as regards imaginable num- 
 bers, what duration is with regard to real or imaginable
 
 CHAP. II.] GENERAL JUDGMENTS. 455 
 
 events, what space is with regard to real or imaginable 
 bodies, a boundless receptacle in which every determined or 
 determinable number comes necessarily to find a place, some- 
 times above, sometimes below, but always in a precise spot, 
 without ever the number, swollen as enormously as we please, 
 ceasing to be contained by the series like &' thing, enclosed by 
 
 things beyond it. -^WftA P V 
 
 So much for collections which are artificial and discontin- 
 uous magnitudes ; the same reasonings applies to times, lines, 
 surfaces, solids, which are natural and continuous magnitudes. 
 Take any portion whatever of the straight line A C ; the first 
 notions of geometry show us that it may be divided into two 
 equal straight lines, A B, B C, the second of which, if applied 
 to the first, intact and without alteration, will coincide with 
 it exactly ; therefore, except as to its position following the 
 first, it is the same as the first, and moreover, by hypothesis, 
 it is the same as before its translation. Since the second 
 line is the same as the first, I may, when it coincides with 
 the first, perform on it the same operation as upon the first, 
 and therefore prolong it, like the first, by a line equal to 
 itself. Since the second line is the same, now as before its 
 translation, I may before translating it, that is to say when 
 it still prolongs the first, prolong it, like the first, by a line 
 equal to itself. I may, then, prolong A B C by C D just as 
 
 I prolonged A B by B C. An analogous 
 
 A B C D E demonstration shows that we can similarly 
 prolong A B C D by D E and so on, how- 
 ever great may be the line so constituted. Every prolonga- 
 tion we effect, then, generates the possibility of another 
 equal prolongation, whence it follows that the series of pro- 
 longations is absolutely infinite. The reader readily per- 
 ceives that, with the necessary changes of words, this analy- 
 sis becomes equally applicable to surfaces, solids, times, and 
 rigorously demonstrates the infinity of time and space. All 
 the artifice of the proof consists in observing two elements 
 of a given magnitude, and remarking that they are the same 
 except as to their difference of position in the magnitude, 
 that this difference is itself indifferent, that is to say of no 
 effect and without any influence on their nature, that, there-
 
 456 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 fore, the increase given to the first element by the second 
 may be given to the whole by a subsequent third element, 
 and in general, to every other analogous whole by a subse- 
 quent element. What creates the infinity of the series, are 
 the properties of its elements. So again, it is by comparing 
 together the elements of infinite series that we compare 
 together such series themselves. This is the process by 
 which I know that the infinite series of even numbers is 
 equal to the infinite series of odd numbers, and that each 
 of them is half of the infinite series of numbers. This is the 
 process by which I know that the infinite surface comprised 
 above a straight line between two perpendiculars a metre 
 apart, is equal to the infinite surface comprised by the same 
 perpendiculars when prolonged below the line, and that 
 these two infinite surfaces taken together are two-thirds of 
 the infinite surface comprised above the line by two perpen- 
 diculars three metres apart. Thus, when we study the ax- 
 ioms which removes all limit from the possible increase of 
 any magnitude, and which sets out this magnitude when in- 
 finitely increased, as a permanent receptacle in which every 
 limited magnitude of the same kind must necessarily find its 
 place and something beyond it, we find only, as in the other 
 axioms, an analytical proposition. It has been sufficient in 
 every case for us to examine attentively our mental construc- 
 tion, to detect in it conditions which are understood, the 
 latent identity of one datum and another, the latent indiffer- 
 ence of a character which seemed to separate the two data, 
 identities and indifferences which we did not perceive at 
 first, since our supposition had not expressly enunciated 
 them, but which were nevertheless tacitly included in our 
 hypothesis, and which, before they were brought to light, 
 revealed their secret presence by the invincible inclination 
 they impressed on our belief, and by the complete evidence 
 with which they enlightened our judgment. 
 
 VIII. We now see how it is that the contraries of axioms 
 and their consequences are not only incredible but incon- 
 ceivable ; it arises from their being contradictory; in this 
 sense, axioms and their consequences are necessary truths. 
 There is no question of greater importance in psychology,
 
 CHAP. II.] GENERAL JUDGMENTS. 457 
 
 for no question has more important consequences in philoso- 
 phy. In fact, these kinds of propositions are the only ones 
 which are applicable, not only to all observed cases, but to 
 all cases, without possible exception ; hence it follows that, 
 on their value, depends the reach of human knowledge. But 
 their value depends on their origin ; it is essential, then, to 
 know whence they spring, and how they are formed. To 
 this, two original and still existing schools give two opposite 
 answers. Let me be understood to speak only of doctrines 
 which hold a place on the world's stage, and of philosophers 
 who have constructed their doctrines without other care than 
 that for truth. Of the two principal answers, the first is that 
 of Kant. According to him, these propositions are the work 
 of an internal force, and the effect of our mental structure. It 
 is this structure which effects the connection between the 
 two ideas of the proposition; if the idea of straight line, 
 that is to say of a certain direction, is joined in my mind to 
 the idea of the least distance, that is to say of a certain 
 magnitude, it is not because this direction and this distance 
 are in themselves connected, it is because my intelligence is 
 fashioned in a certain way, and, being so fashioned, cannot 
 avoid establishing a connection between the two ideas which 
 it has of this distance and of this direction. In fact, the two 
 data taken in themselves are of different kinds; there is no 
 point of real connection between them. Consequently, the 
 invincible mutual attachment which I observe to exist be- 
 tween them in my mind finds its explanation, not in their 
 intrinsic nature, but in the mental medium into which they 
 have been introduced. My mind has not ascertained their 
 connection, it has constructed it. We must admit, then, 
 that these propositions reveal to us a necessity of our mind, 
 and not a connection of things. In the narrow circle to 
 which our experience is confined, we may, indeed, establish 
 by induction, that the corresponding sensible data are ap- 
 proximately connected ; but to affirm that in every place and 
 at every time these abstract data are connected and necessarily 
 connected, is what is not allowed us ; we have no right to im- 
 pose on facts a connection which belongs only to our ideas, 
 nor to set up an infirmity of the subject as a law of objects.
 
 458 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 Starting from the opposite view, Stuart Mill arrives at a 
 similiar conclusion. According to him, these propositions 
 have as their cause an external force, and are, like other truths 
 of experience, the summed-up impression left on our mind 
 by things. Considering two sensible lines sensibly perpen- 
 dicular to a straight line, we verify by an infinity of readily 
 effected measurements that they remain equally distant from 
 one another. Further, we observe that, the more exactly 
 they are perpendicular, the more exactly equal are their 
 distances. Hence it follows that, if they were rigorously 
 perpendicular, their distances would be rigorously equal. From 
 the equality of these distances on our paper, we conclude by 
 induction that, far beyond our paper and at an infinite dis- 
 tance, they would still remain equal. If the contrary sup- 
 position is inconceivable, it is owing to our imagination exactly 
 repeating our vision while giving it greater range ; the internal 
 eye does but add a telescope to the external eye ; therefore, 
 we cannot imagine the two perpendiculars other than as 
 we see them ; we cannot, then, prolong them mentally, with- 
 out representing them to ourselves as still equally distant. 
 Hence it follows that the truths termed necessary, having 
 the same origin as the truths of experience, are subject to 
 the same restrictions and the same doubts. By the axiom as 
 to parallel lines just as by the law of the movement of the 
 planets, we prove the constant association of two data, which 
 are, in fact, constantly associated in nature ; but this associa- 
 tion is not a connection, it is merely a concurrence. Taken 
 in themselves the two data are nothing more than incidents 
 which coincide ; there is no internal necessity in them which 
 assembles them in a necessary couple. Perhaps, beyond our 
 little world, they are found disconnected ; at all events, we 
 have no right to affirm that beyond it they are in all places 
 and in themselves, connected. A mind constructed upon 
 another model than ours might perhaps readily conceive 
 varying distances between our two perpendiculars. It may 
 be that, beyond the nebulae of Herschel, none of our laws are 
 true, and there may even be no law which holds good. We 
 are, then, inevitably driven back from the infinite ; our fac- 
 ulties and our assertions can in no way attain to it ; we remain
 
 CHAP. II.] GENERAL JUDGMENTS. 459 
 
 confined in a very small circle ; our mind cannot carry itself 
 beyond the range of its experience ; we cannot establish any 
 universal and necessary connection between facts ; perhaps, 
 indeed, no such universal and necessary connection exists. 
 By following out this idea to its full extent, we should arrive 
 at the conception of the universe of events and beings as a 
 simple collection or heap. There would be no internal ne- 
 cessity for their connections or existence. They would be 
 pure data, that is to say, things accidentally existing. Some- 
 times, as in our system, they would be found assembled in 
 such a way as to bring about regular recurrences ; sometimes, 
 they would be so assembled that nothing of the sort would 
 occur. Chance would be, as Democritus taught, at the foun- 
 dation of all things. Laws themselves would be derived from 
 it, and would only be derived from it, in certain places. It 
 would be with beings as with recurring decimals, which, 
 according to the hazard of what may be their two primitive 
 factors, sometimes expand in regular periods, and sometimes 
 not, and which generate their successive ciphers, sometimes 
 according to a law, sometimes without following any law. 
 
 Here are two high conceptions, and the powerful minds 
 which formed them are worthy of all admiration and respect ; 
 but we must examine the foundation on which they are 
 built, and, in my opinion, this foundation is not solid. Ac- 
 cording to Kant, there is no necessary connection between 
 the two data ; if there is an invincible connection between 
 the two corresponding ideas, its cause lies, not in the struc- 
 ture of the data, but in the structure of our mind. We rec- 
 ognize, with Kant, an invincible connection between the two 
 ideas. But between the two data, which are the objects of 
 these ideas, and to which he refuses any intrinsic connection, 
 we have discovered an intrinsic connection ; for the first, in a 
 latent manner, contains the second, from which it follows 
 that the contents being inseparable from what contains them, 
 the unsurmountable connection between our ideas is indes- 
 tructible between their objects. According to Stuart Mill, 
 whether there be a connection between the two data or not, 
 we are incapable of knowing it ; for the two data are con- 
 nected by induction alone ; and all induction can prove be-
 
 460 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 tween them is that they are constantly found together, that 
 is to say, an association of fact. We admit, with Mill, that 
 at the outset and in many minds they are only connected by 
 induction ; but we have proved that they may also be other- 
 wise connected. We can represent two perpendiculars upon 
 a straight line by imagination, but we can also conceive them 
 by reason. We can consider their sensible image, and also, in 
 addition to their sensible image, their abstract definition. We 
 can study them ready constructed and generated, but we can 
 also study them during their construction and generation, in 
 their factors and their elements. We can watch their forma- 
 tion and detect the ascension of the base which generates them, 
 just as we can watch the formation of the cylinder and detect 
 the rectangle by whose revolution it is described. From this 
 construction we extract the included properties, and thus form 
 by analysis the proposition we at first formed by induction. 
 Thanks to this second process, the range of our mind is ex- 
 tended infinitely. We are no longer capable only of relative 
 and limited knowledge ; we are also capable of absolute and 
 unlimited knowledge ; in axioms and their consequences we 
 hold data, not only accompanying one another, but such that 
 one includes the other. If, as Mill teaches, they only ac- 
 companied one another, we should be driven to conclude with 
 him that this might not always be the case ; we should see 
 no internal necessity for their junction ; we should simply 
 state it as a fact ; we should say that the two data being iso- 
 lated in their nature, circumstances might be found in which 
 they would be separate ; we should only affirm the truth of 
 axioms and their consequences relatively to our world and 
 our mind. But since, on the contrary, the two data are such 
 that the first includes the second, we establish by that alone 
 the necessity of their junction ; the first, wherever it may 
 be, will involve the second, since the second is a part of it- 
 self, and since a datum cannot be separated from itself. There 
 is no place between the two for a circumstance to intervene 
 to disjoin them ; for they are but one thing in two aspects. 
 Their connection, then, is absolute and universal, and the 
 propositions which concern them do not permit of doubts, 
 limits, conditions, or restrictions. In truth, these proposi-
 
 CHAP. II.] GENERAL JUDGMENTS, 461 
 
 tions are hypothetical ; all they affirm is that, if the first 
 datum be anywhere met with, and especially in nature, the 
 second datum cannot fail to be also met with there, by con- 
 sequence and correspondence. It remains, then, for us to 
 prove that there are, in fact, equal magnitudes, artificial and 
 natural straight lines, lines perpendicular to a straight line, 
 bodies motionless or moving for a very short time at least 
 uniformly in a straight line, movable bodies possessed of 
 constant velocities in different directions, homogeneous sub- 
 stances exactly divisible into equal portions, in short, real 
 data conforming to our mental constructions. To show this, 
 it is necessary and sufficient for experience to intervene ; in 
 fact, in many cases, in astronomy, optics, acoustics, it ascer- 
 tains that certain existing things present the required charac- 
 ters, or at least tend to present them, and would present 
 them, if we could effect upon them the proper eliminations. 
 In all these cases the necessary propositions are applicable, 
 and the real data have the intrinsic connection which Kant 
 and Mill deny them. Thence follow vast consequences, and 
 a view of the foundation of nature, the essence of laws, and 
 the structure of things opposed to those of Kant and Mill.
 
 462 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 CHAPTER III. 
 
 THE CONNECTION OF GENERAL CHARACTERS, OR THE EX- 
 PLANATORY REASON OF THINGS. 
 
 I. NATURE OF THE EXPLANATORY INTERMEDIATE. 
 
 I. WHEN we have ascertained a connection between two 
 data, possible or real, it often happens that this connection is 
 explainable, and we are then able, not only to affirm that the 
 two data are connected, but also to say why they are con- 
 nected. Between the two data which form a couple, there is 
 found another, an intermediate one, which, being connected 
 on the one side with the first, and on the other side with the 
 second, produces by its presence the connection of the second 
 and first, in such a way that this last connection is derived 
 and presupposes, as conditions, the two preliminary connec- 
 tions whose effect it is. In this case we conceive the two pre- 
 liminary connections by two preliminary propositions which 
 we term premises, and we conceive the derived connection by 
 a derived proposition which we term conclusion. Nothing can 
 be more important than this intermediate datum, since it is 
 the one which, by its insertion between the two data, consol- 
 idates them into a couple. We must attempt to find out in 
 what it consists, how we discover it, where we ought to search 
 for it. When this is done, we shall have no difficulty in com- 
 prehending the formation of the two premises into which it 
 enters, and of the conclusion which results from them. 
 
 II. There is a case in which we know all this, that of in- 
 dividual objects subject to known laws. For instance, Peter 
 is mortal ; the two lines drawn on this slate perpendicularly 
 to a third line are parallel : here are couples of data in which 
 the first member is not general, but an individual, particular, 
 determined object. Moreover, these objects are subject to
 
 CHAP. III.] THE EXPLANATORY REASON. 463 
 
 known laws ; we know that all men, among whom is Peter, 
 are mortal, that all straight lines perpendicular to another 
 straight line, among which are the lines on our slate, are par- 
 allel. Now, in this case, the explanatory intermediate which 
 connects the enounced property to the individual object is the 
 first term of a general law : if Peter is mortal, it is because he 
 is a man, and because every man is mortal ; if our two lines 
 are parallel, it is because they are perpendicular to a third, 
 and because all straight lines perpendicular to a third straight 
 line are parallel. But man is a character included in Peter, 
 an extract from him, more general than he is ; so perpendicu- 
 lar to a third is a character included in our two lines, an ex- 
 tract from them, more general than they are. Hence we see 
 that, in the case of individual objects subject to known laws, 
 the intermediate which connects the enounced property with 
 each object is a character included in it, more abstract and 
 more general than it is, common to it and to other analogous 
 objects, and which, involving by its presence the property 
 enounced, draws this property with it in each of the individ- 
 uals to which it appertains. 
 
 Let us now inquire in what this intermediate consists, 
 when it is a question, not of connecting a property to an indi- 
 vidual object, but of connecting a property to a general thing. 
 In othet words, from the explanation of facts, let us pass to 
 the explanation of laws, and, for this purpose, let us examine 
 some of the laws of which the reason and the why are now 
 discovered. In the seventeenth century, after the experi- 
 ments of Galileo and Pascal, it was known that all terrestrial 
 bodies tend to fall towards the earth, and, after Copernicus 
 and Kepler, it was understood that the earth and all the 
 other planets tend to fall towards the sun. Newton came and 
 proved that the two tendencies are the same ; gravitation is 
 common to celestial, as well as to terrestrial, bodies, and, more 
 generally, to all bodies. From that time it was known why 
 terrestrial bodies tend to fall towards the earth, and why the 
 planets tend to fall towards the sun. The weight of the first, 
 and the centripetal tendency of the others, had as reason a 
 property common to both ; the two laws were cases only of a 
 third and more extensive law. From the group of characters
 
 464 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 which constitute a terrestrial body, Newton retained one only, 
 the property of being a mass with reference to another mass ; 
 he eliminated the rest. From the group of characters which 
 constitute a planet, he retained one only, the property of be- 
 ing a mass with reference to another mass ; here again he 
 eliminated the rest. He had, then, derived from the two 
 groups a general and abstract property, more general and 
 more abstract than either of them, contained in each of them 
 like a part in a total, like a fragment in a whole, like an ele- 
 ment in a sum. Instead of connecting, like his predecessors, 
 weight to the first whole group, and centripetal tendency to 
 the second whole group, he connected the weight and the 
 centripetal tendency to an element found alike in both of 
 them. By this brillaint example, we see in what the inter- 
 mediate datum furnishing the reason of a law consists. Given 
 the object subject to the law, this datum is one of its charac- 
 ters, a character comprised in the group of characters which 
 constitute it, a character included in it, more abstract and 
 more general than it, in short, an extract to be extracted. 
 Let us follow out the series of whys, and we shall see that such 
 is indeed the nature and position of the becauses, or alleged 
 reasons. Why does this stone tend to fall ? Because at the 
 surface of the earth all stones, and more generally still all sol- 
 ids, or liquids opposing any resistance to our muscles, tend to 
 fall. Why do all these solids or liquids tend to fall ? Because 
 all masses at the surface of the earth, whatever they may be, 
 solid, liquid, or gaseous, tend to fall. Why do they tend to 
 fall ? Because not only at the surface of the earth, but still 
 further distant, as we have proved in the case of the moon, in 
 all our solar system, as is the case with the planets and their 
 satellites, with comets and the sun, far beyond again, as hap- 
 pens with the double stars, every mass, as soon as it is in re- 
 lation with another mass, tends to approach it. Why this 
 strange tendency? Physicists* are at present inquiring if it 
 
 * " L'Unita delle forze fisiche, saggio di Filosofia Naturale," by Pere Secchi. 
 M. Lame has examined and adopted an analogous hypothesis. See the develop- 
 ment of the whole hypothesis in" La Physique Moderne," by M. Saigey, especially 
 p. 146.
 
 CHAP. III.] THE EXPLANATORY REASON. 465 
 
 cannot be reduced to a continuous impulsion, to the pressure 
 exercised by an ether. If we could succeed in proving that 
 this ether in fact exists, and that the density of its successive 
 layers about a heavy body goes on increasing as the square of 
 the line which represents their distance from the body, the 
 supposition presented would become a demonstrated truth, 
 we should have an additional because ; we should detect in a 
 gravitating body a character still more general and more ab- 
 stract than gravitation, a property wholly mechanical, that by 
 which a body follows an impulsion, and receives a new veloc- 
 ity at each new impulsion. Now this last explanatory char- 
 acter would have the same characteristics and the same posi- 
 tion as the rest. It would, then, like the rest, be a portion, 
 an element, an extract from the preceding one, and would, like 
 the rest, be found in the preceding one, in which it is included. 
 III. Let us now look at those laws in which the explana- 
 tory intermediate seems at first sight of a wholly different 
 kind. Every vibrating body whose vibrations are comprised 
 within certain known limits of slowness and velocity excites 
 in us the sensation of sound. Why so ? Because its vibra- 
 tions have, among other characters, the power of being propa- 
 gated through the surrounding medium up to our acoustic 
 nerve ; in fact, take from them this property, which we do by 
 the suppression of the medium and by setting the body in a 
 vacuum, the vibrations continue-, but, as they cease to be prop- 
 agated, the sensation is no longer produced. Thus the reason 
 which renders these initial vibrations actually sonorous, is the 
 possiblity they have of being propagated, a property included 
 in them and more general than they are, since it is met with 
 elsewhere, for instance, in the vibrations of the luminous 
 ether. Here again the two data, antecedent and consequent, 
 are connected through the medium of a character comprised 
 in the first, and it is the first which we must study with all 
 its circumstances to extract from it the element which is the 
 reason of the law. Now, why does the vibration of the body, 
 when propagated through the medium up to the acoustic nerve, 
 excite in us the sensation of sound ? Because it possesses, 
 among other characters, the power of propagating itself fur- 
 ther still, along the acoustic nerve, up to the acoustic centres 
 3
 
 THE KNOWLEDGE OF GENERAL THINGS. {BOOK IV. 
 
 of the brain ; in fact, take away this property, which we find 
 effected when the subject is deaf, and which we can effect by 
 paralysing the brain with chloroform ; the vibration will be 
 propagated as far as the acoustic nerves, or even as far as their 
 central termination ; but, as it does not reach or does not 
 disturb the cerebral centres, it will not excite the sensation of 
 sound. Thus the reason which renders vibrations propagated 
 up to the acoustic nerve actually sonorous is the possibility 
 they have of being propagated beyond it up to the cerebral 
 centres, a property included in them, and more general than 
 they are, since it is met with elsewhere, particularly in the lu- 
 minous vibrations transmitted to the retina, and, in, "general, 
 in all the disturbances which external bodies impress on our 
 sensory nerves. As before, the two data, antecedent and con- 
 sequent, are connected through the medium of a character 
 comprised in the first, and it is the first, I mean the vibration 
 already propagated up to the nerve, which we must study with 
 all its circumstances, to ascertain in it and detach from it the 
 possibility of a further and complete propagation which is the 
 reason of the law. 
 
 We see that, in this law, the intermediate datum is a char- 
 acter of the first datum, which is the vibration ; just as, in the 
 preceding law, gravitation is a character of the first datum, 
 which is the planet. In fact, between the two cases there is 
 an important difference. In the first, the explanatory charac- 
 ter is one of the least stable elements of the antecedent ; 
 whether the vibration be propagated or not, does not depend 
 on itself, but on many superadded conditions, sometimes pres- 
 ent, sometimes absent ; it requires to meet with a favorable 
 medium, an uninjured nerve, a healthy brain ; if these circum- 
 stances are absent, it cannot be propagated ; it may, then* 
 exist without being propagated ; this will happen if the sur- 
 rounding medium is wanting, or if the nerve or cerebral cen- 
 tres are in an abnormal state. In the second case, on the con- 
 trary, the explanatory character is one of the most stable ele- 
 ments of the antecedent ; even were the planet to, be shivered 
 into fragments and to fall upon another, its fragments would 
 still tend towards the sun, and towards every mass with which 
 they might be in relation. But this difference of the two
 
 CHAP. III.] THE EXPLANATORY REASON. 467 
 
 cases in no way alters their fundamental resemblance, and in 
 the first, as in the second, the explanatory intermediate, stable 
 or unstable, is a more general character, comprised with others 
 in the antecedent, and which must be looked for in the group 
 in which it occurs, that is to say in the first of the two data 
 of the law. 
 
 IV. In the law associating the sensation with the vibra- 
 tion, the intermediate is composed of two successive interme- 
 diates, the power of the initial vibration to propagate itself 
 up to the nerve, and the power of the propagated vibration 
 to propagate itself up to the brain. In other laws, the inter- 
 mediate is equally multiplex, but the intermediates of which 
 it is composed are simultaneous and not successive.* Besides 
 the cases in which the reason is a series of reasons, there are 
 cases in which it is a group of reasons. For instance, the 
 earth describes a particular orbit about the sun. Now the 
 reason which determines this orbit is a sum of distinct reasons, 
 one of which is the initial impulsion, or tangential force, with 
 its quantity in the case in question, another gravitation or the 
 centripetal force, with its quantity in the case in question, and 
 the last, the distance from the earth to the sun at a fixed time 
 and place. In these instances, if .we ask the why, the answer 
 is a sum of becauses ; here especially there are three united 
 reasons, three explanatory characters, three intermediate data, 
 each of which, taken apart, is more general than the total an- 
 tecedent, and which, included in it, concur by their assembled 
 influences to determine the curve in question. Hence an im- 
 portant consequence. Suppose a law in which the first datum 
 is a whole, a compound of distinct parts, an assemblage of 
 data separable in fact, or at all events mentally separable ; it 
 is evident that the explanatory intermediate will be, as in the 
 preceding case, a sum of intermediates which we have here 
 to seek out and detect, one by one, in the various separable 
 data of which our first datum is the whole. 
 
 Such is the case with numbers and geometrical com- 
 pounds. Every number, written according to our ordinary 
 system of numeration, in which the sum of the digits is di- 
 
 * See, on all these points, the fine chapter in Mill's " System of Logic," book 
 iii., chap, xii., " Of the Explanation of Laws of Nature."
 
 468 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV 
 
 visible by 9, is itself divisible by 9. Every convex polygon 
 contains a number of angles which, together with four right 
 angles, are equal to twice as many right angles as the figure 
 has sides. Here are two laws in which the first datum is a 
 sum of separable data ; in fact, the written number is noth- 
 ing more than the sum of its units of various orders, and the 
 polygon is nothing more than the sum of its parts ; hence it 
 follows that the explanatory intermediates must be sought 
 for in the units of various orders which make up the number, 
 and in the parts which make up the polygon. Let us first 
 observe the number ; the units of various orders which form 
 its elements are already detached, prepared, and presented 
 for analysis, and, to detect them, we have only to consider 
 the digits representing them. Now it is easy to see that in 
 every number the sum of the units of the second, third, 
 fourth order, etc., is divisible by 9, with a remainder equal to 
 the digit representing it ; that, therefore, the sum of these 
 sums is divisible by 9, with a remainder equal to the sum of 
 the digits which represent it ; that consequently the entire 
 number itself is divisible by 9, with a remainder equal to the 
 total sum of the digits which represent it ; hence it follows 
 that if the whole sum of the digits is itself divisible by 9, the 
 remainder disappears, and the entire number, divided by 9, 
 leaves no remainder. Here the explanatory intermediate is 
 a character included in all the elements of the number, ex- 
 cept the first, and common to all the units represented by 
 a digit placed to the left of the first ; this character so re- 
 peated compels every number to be divisible by 9, with a re- 
 mainder equal to the sum of its digits, and consequently, 
 renders it divisible by 9, on the single condition that the sum 
 of its digits is divisible by 9. 
 
 Let us now take the polygon ; when it is presented to us, 
 the portions of surface which form its elements are not 
 yet distinct and separate ; we are compelled, then, to create 
 them, and for this, to effect divisions and trace lines ; a con- 
 struction must precede the analysis. We take any point in 
 the interior of the polygon ; from this point we draw straight 
 lines to all its angles ; we thus replace the polygon by a 
 group of triangles whose number is equal to that of its sides.
 
 CHAP. III.] THE EXPLANATORY REASON. 469 
 
 Now, in each of these triangles, the two angles at the base, 
 together with the angle at the vertex, are equal to two right 
 angles ; therefore, if we take all the triangles, and if, adding 
 together all the angles at their bases, we further add all the 
 angles at their vertices, we shall have as many times two 
 right angles as there are triangles, that is to say sides in the 
 polygon. But these angles at the bases are precisely the 
 angles of the polygon ; so that the angles of the polygon, if 
 we add to them the angles at the vertices, are equal to twice 
 as many right angles as the polygon has sides. Now we 
 know independently that the angles at the vertices are to- 
 gether equal to four right angles ; hence it follows that the 
 polygon contains a number of angles which, together with 
 four right angles, are equal to twice as many right angles as 
 there are sides. Here the explanatory intermediate is a 
 character comprised in all the elements of the polygon, that 
 is to say common to all the triangles of which it is the whole ; 
 this character, thus repeated, compels every polygon to con- 
 tain a number of angles which, estimated in right angles and 
 increased by a constant number of right angles, is double the 
 number of its sides. 
 
 But it is not only in arithmetical and geometrical com- 
 pounds that intermediates of this kind occur. Take a car- 
 nivorous animal like the tiger, or a ruminant animal like the 
 ox. A number of precise laws connect each of its organs, 
 and each fragment of each of its organs, with the rest. The 
 naturalist who dissects one organ, knows beforehand what 
 he will find in the others ; from the external appearance, he 
 predicts the internal structure, and can delineate the form of 
 the stomach, the brain, the heart, the skeleton, before he 
 has laid them bare. If he is asked why, in this animal, a 
 particular portion constructed in a particular way involves 
 some other portion, he can answer : his predecessors, from 
 Galen to Cuvier and Richard Owen, have discovered an ex- 
 planatory intermediate which, common to all these very 
 various parts, is the principal reason of their structure and 
 relations. This intermediate is the property of being useful ; 
 each organ performs a function which contributes, with the 
 rest, to a total effect ; therefore, it is appropriate to its func-
 
 470 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 tion ; therefore, it is determined by its function. But this 
 function is itself determined by the others which contribute 
 with it to the total effect ; hence it follows that the organs 
 determine one another with a view to a total effect. In 
 other words, the organs reconcile their characters in such 
 a way as to reconcile their functions, and they reconcile 
 their functions in such a way as to maintain the circuit 
 of loss and reparation which forms the life of the individ- 
 ual and the succession of individuals which forms the 
 race. Consequently, a particular kind of teeth involves a 
 particular kind of intestines, and conversely. If we find 
 an intestine fitted to digest flesh only, and raw flesh, the 
 animal has jaws constructed to devour its prey, claws fit- 
 ted to seize and tear it, teeth fitted to cut and divide it, a 
 system of motor organs fitted to catch it, senses capable 
 of perceiving it at .a distance, the instinct to hide itself in 
 order to surprise it, and a liking for flesh. " Hence follows," 
 says Cuvier, " a certain form of the condyle in order that the 
 jaws may fit together like scissors, a certain volume in the 
 crotaphyte muscle, a certain depth of the fossa which receives 
 it, a certain convexity of zygomatic arcade through which it 
 passes, and a host of characters of the skeleton, the articu- 
 lations, and the motor muscles. . . . The form of the tooth 
 involves that of the condyle, that of the omoplate, that of the 
 talons, just as the equation of a curve involves all its proper- 
 ties, and just as, by taking each property separately as the 
 base of a particular equation, we should rediscover the ordin- 
 ary equation and all the other properties, so the talon, the 
 omoplate, the condyle, the femur, and all the other bones, 
 taken separately, give the tooth, and are conversely given 
 by it." This is so true that, in the same animal, the meta- 
 morphosis of one organ involves an appropriate metamorpho- 
 sis of the rest. The tadpole, which is not carnivorous, re- 
 quiring a very long canal to digest its food, has an intestine 
 ten times the length of its body; when changed into a car- 
 nivorous frog, its intestine is but twice the length from mouth 
 to anus. The voracious larva of the cockchafer has an oeso- 
 phagus, a vast muscular stomach, surrounded with three 
 crowns of little csecums, a small intestine, an enormous large
 
 CHAP. Ill] THE EXPLANATORY REASON. 47! 
 
 intestine three times the size of the stomach, and filling up 
 the whole posterior third of the body : when it has become 
 a cockchafer and more temperate, all that remains of this 
 apparatus is a slender canal destitute of enlargements. By 
 this discovery of the explanatory intermediate, the face of 
 the animal world is entirely changed. Before, we had de- 
 scriptive anatomy only; we knew that in fact certain charac- 
 ters accompanied one another ; but we did not know why 
 they accompanied one another. They were then simply in 
 juxtaposition ; they are now necessarily connected ; in addi- 
 tion to their constant concurrence, as we ascertain their obliga- 
 tory connection. Every organ, and further, every physical or 
 moral element, of the living animal, comprises, included in 
 itself, a property repeated in all the others, that is to say the 
 particularity of tending to harmonize with the rest, in such a 
 way as to concur with them in a certain final and total effect ; 
 and this common intermediate explains not merely a prodi- 
 gious number of characters in the animal, already enumera- 
 ted by descriptive anatomy, but also an infinite number of 
 other more delicate and intimate characters which our scalpels 
 and microscopes are too clumsy to have yet attained. 
 
 We may now form an idea of the intermediate. Take a 
 law, or a couple of data connected together. What is their 
 link? Whence comes their consolidation? What is the 
 reason, the because, the interposed condition, which connects 
 the second to the first? The reader has just followed this 
 intermediate, and finds it reappear, always alike, under its 
 different forms. Sometimes it is simple, like the force of 
 gravitation, which explains the fall of heavy bodies. Some- 
 times it is multiplex ; composed of many intermediates. 
 Two cases then present themselves. Either the components 
 are successive as is, with the sonorous vibration, the power 
 of propagating itself in the surrounding medium, and then 
 the power of propagating itself along the nerve as far as the 
 cerebral centres ; or else the components are simultaneous 
 as are the characters which combine to direct the earth in its 
 course round the sun. Here again we must make a distinc- 
 tion. Sometimes the simultaneous intermediates are of dif- 
 ferent kinds ; as are, in the preceding case, the tangential
 
 472 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 force, the centripetal force, and the given distance from the 
 earth to the sun. Sometimes the simultaneous intermediates 
 are of the same kind, and are reduced to the same interme- 
 diate repeated in all the elements of the object. This last 
 case is itself divisible into two branches. Either the elements 
 in which the intermediate is repeated are similar, like the 
 units of the number, or the triangles of the polygon ; or they 
 are dissimilar, like the organs of the animal. But simple or 
 multiplex, composed of successive or of simultaneous inter- 
 mediates, of different intermediates, or of the same interme- 
 diate repeated, of the same intermediate repeated by similar 
 elements, or of the same intermediate repeated by dissimilar 
 elements, the explanatory intermediate is always shown to 
 us as a character or a sum of characters included in the first 
 datum of the couple, more general than that datum when 
 they are considered apart, and accessible to our grasp, from 
 being comprised in it and separable from it, by our ordinary 
 processes of isolation and extraction. 
 
 V. When once the intermediate is detected and repre- 
 sented in the mind by a corresponding idea, it effects within 
 us an internal process which we term demonstration. Take 
 one of the above-mentioned laws : every planet tends to ap- 
 proach a central mass with which it is in relation the sun. 
 This law is a couple of two data, one, which is the planet, 
 the other, which is the tendency of the planet to approach 
 the central mass, and the intermediate connecting them is a 
 general datum, common, not only to all the planets, but to 
 all bodies situated at their surfaces and to an infinite number 
 of other bodies ; I mean the property of being a mass, every 
 mass having this character that it tends to approach the cen- 
 tral mass with which it is in relation. Let us compare these 
 three data with one another. The first, the planet, contains 
 the intermediate, that is to say the property of being a mass ; 
 it contains the intermediate as one of its characters among 
 many others ; with relation to the planet, the intermediate 
 is an extract only. The planet, then, is more complex than 
 the intermediate, and the intermediate is more abstract, that 
 is to say more general, than the planet. On the other hand, 
 this intermediate contains the last datum, the tendency to
 
 CHAP. III.] THE EXPLANATORY REASON. 
 
 approach the central mass ; it contains this datum as one of 
 its characters, among many others ; with relation to the in- 
 termediate, this datum is an extract only. The intermediate, 
 then, is more complex than the last datum, and the last da- 
 tum is more abstract, that is to say more general, than the 
 intermediate. Thus the first datum of the law contains the 
 intermediate, which contains the second. In another aspect 
 the first datum is more complex than the intermediate, which 
 is more complex than the second. In another aspect again, 
 the second datum is more abstract and general than the in- 
 termediate, which is itself more abstract and more general 
 than the first datum. Having settled this, let us associate 
 the three data in pairs ; we shall have three couples of data, 
 or laws. Every planet is a mass ; now every mass tends to 
 approach the central mass with which it is in relation ; there- 
 fore, every planet tends to approach the central mass with 
 which it is in relation, that is to say, the sun. Of these 
 three couples, the first associates the first datum and the in- 
 termediate; the second associates the intermediate and the 
 second datum ; the third associates the first datum and the 
 second, and is found to be the law which required demon- 
 stration. If we conceive the three couples in this order, we 
 have three propositions corresponding to them and composed 
 of three ideas, associated in pairs, as the three laws are com- 
 posed of three data associated in pairs. Of these three 
 ideas, the first, which is more comprehensive than the second, 
 contains the second, which is more comprehensive than 
 the third, and which contains the third, and the mind passes 
 from the most comprehensive to the least comprehensive by 
 means of the third, which is of medium comprehension.* 
 Of these three propositions, the two first, being preliminary, 
 are termed premises, and the third, being consecutive, is 
 termed conclusion. The two premises are composed, one, of 
 the first idea, the most comprehensive of all, associated to 
 the second, which is of medium comprehension ; the other, 
 of the second idea, which is of medium comprehension, asso- 
 
 * In my opinion, it is in this order, according to comprehension and not ac- 
 cording to extension, that the terms should be arranged. In this way, reasoning 
 becomes an analysis, and not a logical trick, like the ordinary syllogism.
 
 474 THE KNO WLEDGE OF GENERAL THINGS. [BOOK IV 
 
 ciated to the third, the least comprehensive of all ; and finally, 
 the conclusion is composed of the first idea associated to the 
 third, that is to say of the most comprehensive idea asso- 
 ciated to the least comprehensive. Three propositions of 
 this kind assembled in this order constitute a syllogism, and 
 the syllogism, according to the saying of Aristotle, becomes 
 a scientific demonstration, when, as in the preceding case, 
 the intermediate by which it connects two data is the ex- 
 planatory reasonf of their connection. 
 
 11. 
 
 I. Let us leave to logicians the task of following out in all 
 their details the properties of the syllogism, and the neces- 
 sary relations of its propositions or terms; these are but the 
 curiosities of science ; the essential thing for the mind is to 
 know what are the special characteristics and exact position 
 of the explanatory intermediate, so as to be able to seek for, 
 find, and recognize it. From its nature and situation, as we 
 have ascertained them, we can arrange a general method of 
 inquiry. Let us examine this method successively in the 
 sciences of construction and in the sciences of experience. 
 
 Take a law of arithmetic, of algebra, of geometry, or of 
 pure mechanics ; the proposition which expresses it is termed 
 a theorem ; and this proposition affirms that a particular 
 datum constructed by the mind a number of any kind, a 
 multiplicand, a square, a square root, a triangle, a sphere, an 
 ellipse comprises a particular property. It is here a ques- 
 tion of demonstrating the theorem, that is to say of distin- 
 guishing in the first datum an intermediate which comprises 
 the property enounced. We have, then, to decompose the 
 first datum so as to extract from it the intermediate, and it 
 is this decomposition which, later back, when dealing with 
 axioms, we termed analysis. In the Sciences of Construction, 
 it can always be accomplished ; there is no internal obstacle 
 which prevents our detecting the intermediate ; it is included 
 in the first datum as Constructed by our mind. In fact, the 
 
 * df alrluv KOI irporepuv. " Posterior Analytics," book i. chaps, ii. iv. vi. 
 atria signifies not merely the cause, but the because demanded. These second 
 Analytics of Aristotle are very superior to the first, and are still worthy the at- 
 tention of students of special sciences.
 
 CHAP. III.] THE EXPLANATORY REASON. 475 
 
 combination we have fabricated is purely mental ; it is not 
 bound to correspond to a real combination. It differs in this 
 from the other mental combinations by which we conceive 
 real objects ; it runs no risk, as they do, of presenting blanks, 
 of passing by any important character included in the real 
 object, of omitting the explanatory intermediate which con- 
 nects the enounced property with the real object ; freed from 
 this obligation, it is exempt from this risk. Once formed, it 
 is complete, and whatever be the ideal object number, square, 
 straight line, figure, geometrical solid, velocity, mass, force 
 if the definition furnished is well constructed, the object is 
 entirely and exactly expressed by it.* For, by hypothesis, 
 there is nothing more in the ideal object than what we have 
 put into it, and all we have put into it are certain elements 
 grouped in a certain order, and expressed, together with their 
 order, by the definition. Now, if this group has a property, 
 it is through the medium of some character included in its 
 elements or in their mode of assemblage, as expressed by the 
 definition ; hence it follows that the explanatory and demon- 
 strative intermediate connecting the property to the group 
 will be found by analyzing the terms of the definition. 
 
 Such is in fact the method employed in the Sciences of 
 Construction. All the theorems are demonstrated by analy- 
 sis, by the analysis of the terms of the definitions. We have 
 already seen this in those first theorems with whose demon- 
 stration we dispense, and which we term axioms. We have 
 defined equal magnitudes, the straight line, parallel lines, 
 velocity, force, mass, and have found that the properties at- 
 tributed by the axioms to each primitive compound are con- 
 nected with it through the interposition of some latent, but 
 inherent character, enclosed and concealed in its definition. 
 
 So it is with the later theorems concerning more complex 
 compounds. Here, too, the explanatory and demonstrative 
 intermediate is a character, mere frequently a series of char- 
 acters, included in the definition of the compound. We all 
 know how a theorem of geometry is demonstrated, as for in- 
 stance, that which says that the opposite sides of a parallelo- 
 
 * See part ii., book iv., chap, i., pp. 409 etseq.
 
 476 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 gram are equal. We refer back to the definition of the paral- 
 lelogram and find that it is a four-sided figure of which the 
 opposite sides are parallel. As this double property is includ- 
 ed in the definition, we extract it by analysis, and have the 
 first of the intermediates we are in search of. We analyze 
 this, and on referring back to the properties of parallel lines, 
 
 we find that, if we draw the diagonal 
 A C, the two angles B A C, D A C, 
 are equal to the two A C D, B C A, 
 each to each, being alternate angles ; 
 which gives us a second intermediate. 
 But, on the 'other hand, the diago- 
 nal has formed triangles as well as an- 
 
 gles ; we then analyze this third in- 
 termediate, and, on referring back to the properties of trian- 
 gles, we observe that the two triangles are equal, as having a 
 common side, the diagonal, comprised between two angles 
 equal each to each ; hence it follows that A B is equal to D 
 C, and A D to B C. Thus, the first intermediate the par- 
 allelism of each couple of opposite sides is derived from the 
 definition ; the second the equality of the two alternate an- 
 gles which the diagonal forms with each couple of parallel 
 lines is derived from the first ; the third the equality of the 
 triangles which the diagonal forms on each side with the par- 
 allel lines is derived from the second, and finally, the equal- 
 ity of the opposite sides of the parallelogram is derived from 
 the third. The definition, then, contains the first intermedi- 
 ate, which contains the second, which contains the third, 
 which contains the fourth, which contains the property 
 enounced. This forms, as it were, a series of boxes enclosed 
 in one another ; the largest is the first definition, and the 
 smallest the last attribute ; each larger box encloses a smaller 
 one, and we cannot get at any one box till we have opened 
 in turn all those enclosing it. Observe the difficult part of 
 the operation. Each intermediate contains many characters 
 in addition to the one which we extract and which leads us 
 up to the property enounced ; we must not fall into error, and 
 overlook the right one, to extract another. In other words, 
 and to continue the comparison, every larger box contains, in
 
 CHAP. III.] THE EXPLANATORY REASON. 477 
 
 addition to the smaller box in which we shall at last find the 
 property enounced, several other smaller boxes which it 
 would be useless to open ; we must set our hand, then, on the 
 right box, and if there are, as in the preceding -case, five 
 boxes to open, we must five times consecutively have the tact 
 to make a proper choice. Besides this, it is common to find 
 boxes which do not open readily, a skilful turn of the key is 
 required ; we have been compelled to make a construction, 
 to add a line to the figure, to draw the diagonal. And this 
 turn of the key has, in opening one lock, opened by corre- 
 spondence a second ; in fact, this well chosen diagonal has 
 not only given the two* pairs of alternate internal angles it 
 has also given two equal triangles. In this lies the talent of 
 the geometrician ; he must, by a prompt instinct, or by numer- 
 ous trials, successively open, without a mistake, the series of 
 useful boxes, and must find out the appropriate turn of the key. 
 Let us now follow his steps : he begins by constructing 
 very simple compounds, the single straight line, the straight 
 line cutting another, the straight line perpendicular to another, 
 two parallel straight lines. According to the process we 
 have just seen, and through an intermediate, or arrangement 
 of intermediates included in the definition of the compound, 
 he connects with it several properties. Then, combining 
 together his primitive compounds, he constructs ulterior 
 compounds, triangles, quadrilaterals, and polygons, by means 
 of two, three, and more straight lines cutting each other in 
 pairs ; the circle, by a straight line turning about one of its 
 extremities ; the plane, by a revolving perpendicular which 
 while revolving remains perpendicular to the straight line 
 with the relation to which it was at first perpendicular ; after 
 this polyhedra, by planes terminating in polygons ; the sphere, 
 by a semicircle revolving about its diameter, etc. To these 
 new compounds, he connects new properties by means of new 
 theorems. What intermediates djoes he employ ? They may 
 be recognized at a glance ; they are the already demonstrated 
 properties of the preceding compounds. The more complex 
 compound has simpler compounds as its factors, and the 
 properties of its factors, introduced into it with those factors, 
 are the intermediates by which we connect to it the proper-
 
 478 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 ties with which it is itself furnished. Just now we saw that 
 the properties of the parallelogram were attached to it through 
 the properties of the two pairs of parallel lines which form its 
 elements. We should see in the same way that the properties 
 of the sphere are attached to it through the properties of the 
 revolving semicircle which generates it, and, in general, that 
 the properties of any compound are attached to it through 
 the properties of the simpler compounds which are its factors. 
 In this way, each new compound is a larger box into which 
 we put several smaller boxes, with all they contain. In the 
 one we term parallelogram, we put two pairs of parallel lines 
 cutting each other. In the one we term circle, we put an 
 infinite number of equal straight lines, having one common 
 point. In the one we term sphere, we put an infinite number 
 of equal semicircles having a common diameter, and the 
 properties of the large box so constructed are attached to it 
 through the properties of the smaller boxes which it contains 
 with their contents. Hence it follows that the ultimate rea- 
 son, the ultimate because, the ultimate explanatory and de- 
 monstrative intermediate, which connects a property to any 
 geometrical compound, recedes from box to box, and from 
 containing to being contained, in proportion as we pursue it 
 from the sphere to the revolving semicircle, from the revolv- 
 ing semicircle to the revolving line, from the revolving line 
 to the simple line that is to say, from the compound to its 
 factors, from them to their factors, and so oa, to allow itself 
 to be seized at last in the primitive factors that is to 
 say, in the little elementary boxes in which it is included. 
 Arrived here, we have, in hand the ultimate reason of the 
 geometrical law. It is given, in all the sciences of construc- 
 tion as in geometry, by the axioms; and the axioms give it, 
 because they enounce the properties of the primitive factors. 
 Let us carefully consider this expression ; the ultimate 
 reason of a law. The laws we have discovered in the sciences 
 of construction are of enormous number, and this number 
 increases daily. Now the ultimate intermediates which ex- 
 plain and demonstrate them are the properties of five or six 
 primitive factors, enounced by a dozen axioms, which are 
 themselves, as we have seen, cases or applications only of the
 
 CHAP. III.] THE EXPLANATORY REASON. 
 
 axiom of identity. From this single source, spread out into 
 a dozen rivulets, flow the innumerable streams and waves of 
 science. Such is the value of the primitive factors or ele- 
 ments, when they are as simple, as abstract, and as general 
 as possible : from their laws are derived the laws of their less 
 general and less abstract compounds, and so on, from stage 
 to stage, by a gradual descent, without ever a failure of con- 
 tinuity, between stage and stage, from the highest wave to 
 the lowest level. It is, then, to the primitive factors that the 
 principal efforts of our method should be directed. Hence a 
 new way of considering magnitudes, and especially geometri- 
 cal magnitudes. Take a straight line, or curved lines, and 
 those principally among curves, which we were unable in the 
 beginning to define except by the nature of the solid from 
 which they are derived, as was the case with the sections of the 
 cone that is to say the ellipse, parabola, and hyperbola, and 
 with other still more complex curves. Each of them has a 
 form, and, when once the line is drawn, we see this form in 
 the concrete. But the line is made up of primitive factors or 
 elements which are its points, and its form is but a whole, the 
 whole of the distinct positions occupied by its distinct points. 
 Hence it follows that there is a reason, a because, an interme- 
 diate to explain and demonstrate all the properties we can 
 ascertain in the line and its form, and that this intermediate 
 is met with in the elements of the line and of its form that 
 is to say, in the various points possessed of distinct positions 
 of which the line and form are but the total. Now, how do 
 we determine the position of a point? Among other means, 
 there is a very convenient one, which con- 
 sists in taking in a plane two fixed axes A 
 B, B C, which cut one another at a known 
 angle, in drawing to the point, lines par- 
 allel to these axes, and in giving the lengths 
 of these parallels. These two lengths, which 
 we term co-ordinates, are magnitudes which, 
 when compared together, present a certain relation. Here, 
 then, we have the position of the point defined by the mu- 
 tual relation of two auxiliary magnitudes. Instead, now, 
 of a single point, let us suppose a continuous series of
 
 480 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 points that is to say a line, such that this relation may be 
 the same for all its points ; the line and its form will be 
 wholly defined, and defined by a character common to their 
 elements. 
 
 Thus, to confine ourselves to the simplest examples, if, 
 the two axes being given, the line in question bisects the 
 angle between them, all the points of the bisecting line have 
 this common character that, for each of them, one of the two 
 co-ordinates is equal to the other. If the line in question is 
 a circumference, and the two axes are perpendicular to one an- 
 other and pass through the centre of the circle, all the points 
 of the circumference have this common character that, for 
 each of them, the sum of the squares of the two co-ordinates 
 is equal to the square of the radius. This constant relation, 
 which is everywhere maintained through all the pairs of co- 
 ordinates, gives rise, when ascertained, to an equation ; for 
 the bisecting line, the first co-ordinate x added to the second 
 co-ordinate y is equal to 2 ;r ; x -\- y = 2 x; similarly, for the 
 circumference x 3 -j- j" = r*. This formula is what is termed 
 the equation to the line ; there is one for the ellipse, for the 
 parabola, the hyperbola, for every curve, for every surface. 
 There is a branch of geometry which makes an analysis in 
 this way of a line or a surface, and on decomposing it into 
 its elements, discovers in these elements an algebraical char- 
 acter common to them all; this science is termed analytical 
 geometry. From the character expressed by the equation, 
 we derive all the properties of the line ; in other words, in 
 order to attach the properties to the line, we find an inter- 
 mediate, a reason, a because included in the equation which is 
 the definition of the line. 
 
 We see how important is the consideration of the ele- 
 ments ; in fact, it has been necessary to gain a true notion of 
 magnitude, and to give to mathematics all their scope ; it is 
 this study which, under the name of infinitesimal calculus, 
 constitutes the higher portion of the science. Instead of 
 comparing two magnitudes taken in the mass, we compare 
 the infinitely small increments of the two magnitudes, incre- 
 ments which are their component factors and their primitive 
 elements. " It would be wrong," says a philosophical mathe-
 
 CHAP. III.] THE EXPLANATORY REASON. 48 1 
 
 matician,*-" to take this second mode of expression for noth- 
 ing more than a conventional abbreviation, a form of lan- 
 guage, apparently more convenient because, more usually 
 employed. It is, in fact, more convenient, but simply be- 
 cause it is the natural expression of the mode of generation 
 or extinction of magnitudes, which increase or decrease by ele- 
 ments smaller than any finite magnitude. Thus, when a body 
 cools, the relation between the elementary variations of the 
 heat and time is the true reason of the relation which is 
 established between the variations of these same magnitudes 
 when they have acquired finite values. This last relation, it 
 is true, is the only one which can fall directly under our ob- 
 servation, and, when we define the first by the second through 
 the intervention of the idea of limit, we conform to the con- 
 ditions of our human logic. But, once in possession of the 
 idea of the first relation, we conform to the nature of things, 
 by making it the principle of explanation of the value which 
 observation assigns to the second relation. This is why the 
 notation of infinitesimal quantities, imagined by Leibnitz, 
 constitutes an invention of capital importance which has mar- 
 vellously increased the power of mathematics as an instru- 
 ment, and the field of its applications to natural philosophy." 
 In all directions, the same conclusion springs up. In the 
 sciences of construction,, every theorem which enounces a law 
 is an analytical proposition. Of the two data whose connec- 
 tion forms the law, the second is connected with the first, ob- 
 scurely or clearly, directly or indirectly, by a third datum, rea- 
 son, explanatory and demonstrative intermediate, which is 
 contained in the first datum, and itself contains a series of sub- 
 sequent intermediates enclosed in one another. Finally, if we 
 inquire into the ultimate reason of the law, the ultimate inter- 
 mediate, the ultimate because, after which every question is at 
 an end, because the supreme explanation is furnished and the 
 demonstration complete, we find that it is a character included 
 in the definition of the factors or primitive elements of which 
 the first datum is but the collection and the total. 
 
 * Coumot, " Traite de I'Enchainement des Idees P\>ndamentales," i. 87, and 
 ' Traite Elementaire du Calcul Infinitesimal," i. 82. " In this respect we may 
 truly affirm that infinitely small quantities exist in nature." 
 
 31
 
 482 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 II. We come now to the sciences of experience. Here 
 the resources are fewer and the difficulties greater. Let us 
 take one of the laws examined above namely, that cooling 
 produces dew, that is to say the liquefaction and deposition 
 of the watery vapor in the surrounding air. Of the two 
 data, cooling and liquefaction, whose couple forms the law, 
 the first, according to the theory expounded, must comprise 
 an explanatory character by whose intervention it is con- 
 nected to the second. It is necessary, then, to decompose it 
 in order to derive from it this intermediate. But I am un- 
 able to effect this decomposition ; the analysis which had 
 entire grasp of mental combinations has not an equal grasp 
 of real combinations. Having constructed the first, I know 
 all they contain, since, by supposition, they contain nothing 
 but what I have put in them. Not having constructed the 
 second, I do not know all they contain, and to the portion 
 of knowledge I possess, I must add by further discoveries the 
 various portions I do not possess. What is this cooling of 
 watery vapor? At the time I establish the law by induc- 
 tion, I am ignorant of this. All I know of it is, that it is a 
 change of state, occurring in the vapor, which excites in me 
 the sensation of cold. This change is in itself unknown to 
 me; all I know of it is one of its effects, and this I only know 
 through a sign. We have now, with the aid of this sign and 
 other indications, such as the variations of the thermometer, 
 to study this change, to ascertain its intrinsic properties, and, 
 for this purpose, again to employ induction. Now, we dis- 
 cover by induction that cold applied to a body in whatever 
 state, gaseous, liquid, or solid, tends to bring its molecules 
 mutually together, and in fact does always bring them to- 
 gether, except in some exceptional cases, in which the ten- 
 dency is neutralized by certain contrary tendencies which the 
 bringing together may sometimes develop.* Here is a first 
 explanatory intermediate, included in the characters of the 
 chilled body and set apart by induction. Now other induc- 
 tions establish that a solid, liquid, or gaseous body is a 
 system of molecules placed apart and possessed of attracting 
 
 * For instance, the maximum of density, or of the bringing together the 
 molecules of water, is found at * 4 degrees (centigrade), and not below.
 
 CHAP. III.] THE EXPLANATORY REASON, 483 
 
 and repelling forces in relation to each other ; that in pro- 
 portion to their mutual proximity, the mutual proportions 
 of the attracting and repelling forces are changed and re- 
 versed ; that, during a first period the gaseous state the 
 attracting forces may be considered as annulled by the enor- 
 mous amount of the repelling forces, which explains the force 
 of tension in vapors and gases ; that at the end of this period, 
 when the molecules are sufficiently proximate, there comes 
 an epoch of equilibrium between the attracting and repelling 
 forces, an epoch differing according to the different constitu- 
 tion of the different bodies ; that, during this stage, repulsion 
 and attraction being almost neutralized by one another, the 
 molecules which have neither mutual attraction nor repulsion 
 suffer themselves to be readily disjoined, put forth no effort 
 against what contains them, group themselves in a surface 
 parallel to the horizon ; in short, are fluid and present the 
 sensible characters which constitute the liquid state, instead 
 of the sensible characters which constitute the gaseous state; 
 that later on, beyond this second period, when the molecules 
 are again brought still closer, an epoch is presented in which 
 the attracting forces have not only equality but marked as- 
 cendancy, an epoch differing according to the different con- 
 stitution of the different bodies ; that, during this third stage, 
 the grouped molecules offer a more or less energetic resis- 
 tance to forces attempting to detach them from the system, 
 and, instead of the sensible characters which constitute the 
 liquid state, present the sensible characters which constitute 
 the solid state. Hence it follows that when a certain period 
 is passed, the gas, whose molecules are brought sufficiently to- 
 gether, must become liquid, and the watery vapor must become 
 water. Now we know independently by induction the limit 
 at which this period comes to an end in the case of watery 
 vapor; it is a particular degree of the thermometer for a par- 
 ticular quantity of watery vapor suspended in the air. Here 
 is the second intermediate required. If the cooling produces 
 liquefaction of the surrounding vapor, this arises from its 
 bringing the molecules of vapor together beyond a certain 
 limit ; if, beyond this limit, the approximating molecules 
 arrive at the liquid state, this is because, when this limit is
 
 484 THE KNOWLEDGE OF GENERAL THINGS. [BooK TV. 
 
 passed, the excess of the repelling over the attracting forces 
 ceases without being turned in the contrary direction, and in 
 consequence of this equilibrium, the molecules cease to have 
 any noticeable mutual adherence or repulsion, which is pre- 
 cisely the liquid state. Approximation of molecules, equilib- 
 rium between the attracting and repelling forces of the mole- 
 cules after a certain degree of approximation these are 
 the two intermediates by which the first datum of our law 
 cooling, is attached to the second liquefaction, and the ap- 
 proximation is a property of the molecules of the chilled 
 vapor. Equilibrium is a property of these molecules when 
 brought sufficiently close. And finally, the liquid state as 
 our senses perceive it, is a property of the equilibrium so 
 attained. 
 
 Thus the first datum of the law contains among its char- 
 ractcrs the first explanatory intermediate, which contains the 
 second, which contains the second datum of the law. Plainly, 
 this enclosure is similar to that which we have already ob- 
 served in the demonstration of the theorems. No doubt, 
 we have not here obtained the intermediates by the same 
 method as before. It has not been sufficient for us to con- 
 sult our conception of a cooling body ; there were too many 
 gaps in it ; it taught us nothing except that the body which ex- 
 cites a sensation of cold in ourselves and a lowering of the mer- 
 cury in the thermometer undergoes an unknown alteration. 
 Experiments and an induction were required to discover this 
 alteration, which consists in an approximation of molecules. 
 And so, it was not enough for us to consult our conception 
 of a body whose molecules approximate ; here again there 
 were too many gaps, it taught us nothing as to the effects of 
 approximation. The great induction of Newton was required 
 to enable us to recognize that the attraction of the molecules 
 increases in the inverse ratio of the squares of their distances, 
 whence it follows that, when a certain degree of proximity is 
 passed, the attracting forces must form equilibrium with the 
 repelling forces ; and the inductions of other physicists were 
 necessary to ascertain what degree of cooling induces this 
 degree of proximity between the molecules of watery vapor. 
 But, if the processes of discovery have been different, the
 
 CHAP. Ill,] THE EXPLANATORY REASON. 485 
 
 structure of things has been shown to be the same. In the 
 experimental law as in. the mathematical theorem, the first 
 datum is a large box which, through a series of gradually 
 diminishing boxes, encloses as its final contents the second 
 datum. Only, in the experimental law it is not sufficient, as 
 in the mathematical theorem, to set the hand each time on 
 the proper box and to open it ; we do not find the box at 
 hand, in the mind ; we must go els. where, beyond the mind, 
 and seize it where it is, that is to say in nature, and derive it 
 thence with a great array of experiments and inductions. 
 When this is effected, we transfer it into the mind, we fix it 
 there in its place in the box from which it was missing, and 
 when, by these excursions, we have thus procured all the 
 necessary boxes, we have only to open them in their order, to 
 pass uninterruptedly, as in a theorem, from the first to the 
 second datum of the law. 
 
 Let us now consider those of the experimental sciences 
 which are in a very advanced state, applied mechanics, 
 physical astronomy, optics, acoustics, in which many of these 
 boxes have been discovered and enclosed. Between the real 
 compounds, of which these sciences treat, and the ideal com- 
 pounds, of which the sciences of construction treat, the 
 analogy is striking. Take some of these real compounds, the 
 motion of a cannon-ball impelled with a certain initial velocity 
 along a tangent to the earth, the orbit described by Venus or 
 some other planet, a certain succession of sonorous or luminous 
 waves. Each of these compounds has its properties like the 
 parallelogram or the sphere, and the proposition connecting 
 some property to it, like the theorem connecting some prop- 
 erty to the parallelogram or sphere, enounces a general law. 
 Now, in this compound, as in the parallelogram or sphere, there 
 are factors or more simple compounds which, introduced into 
 it, have brought with them their characters ; and if the com- 
 pound possesses the property indicated by the law, it is owing, 
 as in the parallelogram or sphere, to the isolated or combined 
 characters of its factors. If the cannon-ball has a certain 
 range, describes a certain curve, and undergoes a certain dim- 
 inution of velocity, it is owing to the combined presence of a 
 particular initial impulsion, of terrestrial attraction and the
 
 486 THE KNOWLEDGE OF GENERAL THINGS. [BooK IV. 
 
 resistance of the air. If two luminous rays are in places ex- 
 tinguished by one another, or if two continuous sounds are 
 at times pushed by one another, it is owing to the velocities of 
 the two series of propagaLed waves which, in certain places and 
 at certain times, interfere with and annul one another. Hence 
 it follows that, in the experimental as in the geometrical law, 
 the properties of a more complex compound are connected 
 with it through the intervention of properties of its factors 
 or more simple compounds, that so it is with each of these 
 factors, and that therefore, if we seek the ultimate interme- 
 diates, the ultimate reasons, the ultimate explanatory and 
 demonstrating characters which establish the law, we shall 
 see them recede, from the more complex to the less complex 
 compounds, to permit themselves to be seized at last in cer- 
 tain very simple factors or primitive elements whose proper- 
 ties they are. 
 
 In fact, in each of the sciences we have mentioned, there 
 are some very general laws corresponding to axioms ; these 
 give, like axioms, the ultimate reason of the established law, 
 and they give it because, like axioms, they enounce the prop- 
 erties of the primitive factors. Such, for instance, is the 
 principle in applied mechanics, that if a body loses or acquires 
 a certain quantity of motion, the same quantity is acquired 
 or lost by some other body. Such are the two principles on 
 which astronomy is founded, the one which attributes to the 
 planetary bodies of our system a tendency to move in a 
 straight line with a uniform velocity along the tangent to 
 their orbits, the other which attributes to them a tendency 
 to fall towards each other and towards the central mass, a 
 tendency in proportion to their masses and inversely as the 
 squares of their distances. Such is, in acoustics and optics, 
 the assumption of elastic media, through which waves of cer- 
 tain lengths are propagated with certain velocity in the di- 
 rection of their primitive impulsions, or in a direction per- 
 pendicular to those impulsions. From these laws there flow, 
 as from so many axioms, a prodigious number of partial laws ; 
 and the only difference separating sciences so constructed from 
 the mathematical sciences, is that as, in these last, the axioms 
 have been obtained by construction, we can mount by analy-
 
 CHAP. III.] THE EXPLANATORY REASON. 487 
 
 sis higher than the axioms, to the principle of identity, which 
 is their common scarce, while in the former, the fundamental 
 laws having been obtained by induction, to mount above 
 them we must again have recourse to induction, which to- 
 morrow perhaps we may be able to effect, but which to-day 
 we are unable to effect, and which compels us provisionally 
 to consider them as primitive, until further discoveries place 
 over them more general laws, and so depose them from the 
 first to the second rank. 
 
 III. The same arrangement is found in the other less 
 advanced branches of experimental science, in the theory of 
 heat, of electricity, of chemical, vital, and historical phenom- 
 ena. Here, too, the particular laws which we first attain, 
 and which enounce the properties of the more complex com- 
 pounds, find their explanation and demonstration in the more 
 and more general laws which we subsequently attain, and 
 which enounce the properties of more and more simple fac- 
 tors. Accordingly as we consider the different branches, 
 we find that the operation, which is everywhere similar, has 
 been pushed to greater or less distances; experimental 
 science, as a whole, thus resembles a cathedral commenced in 
 various points at once. Its pillars are of unequal height, 
 some almost completed, others half built, others again 
 scarcely provided with their first stages. But they all indi- 
 cate by their gradual diminution and converging directions, 
 that a loftier arch must finally reunite them. 
 
 Now this constant convergence shows us in what direction 
 to apply our efforts, and what subsequent labor is required 
 to continue the edifice. We have just seen that the proper- 
 ties of a compound are connected with it by intermediates, 
 which are the properties of its factors, components, or ele- 
 ments ; Phis is the universal rule. These elements, then, are 
 what it is principally necessary to discover, and it is to their 
 properties that we should direct our whole attention. The 
 more readily, therefore, these elements fall under our obser- 
 vation, the more readily shall we explain and demonstrate 
 the properties of the compounds formed by their assemblage. 
 This is precisely the case with the most complex com- 
 pounds of all, those which are the object of the natural and
 
 4 88 TrIE KNOWLEDGE OF GENERAL THINGS. [BooK IV. 
 
 historical sciences. And I venture also to assert, that the 
 philosophical and higher portion of science is nowhere 
 more advanced than here. A living body, plant or animal, 
 is a society, of organs ; now, each of these organs is suffi- 
 ciently large to be grasped by our senses, measured by our 
 instruments, detailed by our descriptions, pictured by our 
 drawings. It lends itself directly to study, and compared 
 with those analogous to it, manifests properties which, joined 
 with those of its associates, explain the character of the body 
 whose elements they are. There are two properties common 
 to all the organs of a living body. One of them, mentioned 
 above,* and explained at length by Cuvier, is the property of 
 being useful, which imposes on the organ the obligation of its 
 characters harmonizing with those of all the other associated 
 organs, in such a way as to bring about some total and final 
 effect, that is to say to render possible a certain kind of life, 
 carnivorous, frugivorous, insectivorous, in the water, in the 
 air, or on land, in presence of certain prey and certain ene- 
 mies, in short, in a certain medium ; we have indicated the 
 infinite consequences of this property of every organ ; they 
 are so numerous and so certain that anatomists have re- 
 constructed fossil animals from some of their fragments. 
 There is a second property, discovered by Geoffroy Saint- 
 Hilaire, and still more fruitful in consequences, that of holding 
 a place in a plan. By the first, the organ is an instrument 
 which fulfils an office ; by the second, it is a part appertain- 
 ing to a type. In this respect, whatever be the secondary 
 modifications imposed on it by its passage from one animal 
 to a different one, and its consequent adaptation to a new 
 usage, it remains fundamentally the same ; it is never trans- 
 posed ; we find it always in the same place, and it shows itself 
 through all the elongations, consolidations, impoverishments, 
 changes of part, and even losses of employment, which it has 
 undergone in its deformed, transformed, and atrophied state. 
 The same group of anatomical articulations supplies the arm 
 and hand in man, the wing in the bat, the paw in the cat, 
 the leg in the horse, the fin in the seal ; the natatory bladder 
 of the fish is the respiring lung of the mammal. We often 
 
 * Part ii, book iv. ch. iii. p. 495.
 
 CHAP. III.] THE EXPLANATORY REASON. 489 
 
 find in birds a little useless bone on the border of the wing, 
 furnished, when they are young, with a nail, without use, ex- 
 cept as representing a degraded finger ; the crawling boa has 
 vestiges of limbs, and we find in the slow-worm a rudimen- 
 tary shoulder, sternum, and pelvis ; the same slow-worm has, 
 in its youth, two small projecting tubercles, the surviving and 
 temporary remnants of stunted hinder limbs. A part, then, 
 has the property of exciting by its presence the presence of 
 a whole system of parts, arranged according to a fixed pat- 
 tern, which gives us the rough framework of the whole ani- 
 mal, and has, besides, the property of determining by its 
 structure and function, the structure and function of the other 
 parts which gives us the whole structure and group of the 
 functions of the complete animal. In this way, two proper- 
 ties common to the elements of the group explain nearly all 
 the characters of the group, and philosophical anatomy fur- 
 nishes the reason of the laws which descriptive anatomy had 
 ascertained. 
 
 And so, in those human societies whose fixed or changing 
 characters are the subject-matter of history, the elements, 
 which are readily seized, enable us to comprehend the whole. 
 For these elements are the human individuals of whom a 
 society at any given epoch is the collection only, and we 
 have no difficulty in detecting their common characteristics. 
 By means of existing records, and by the exact processes of 
 methodical reconstruction, we are at present able to suppress 
 the distance of time so as to represent to ourselves by more 
 or less numerous specimens, the Frenchman or Englishman 
 of the seventeenth century or of the Middle Ages, the 
 ancient Roman and even the Hindoo of the Buddhist epoch, 
 to picture to ourselves his life, private, public, industrial, ag- 
 ricultural, political, religious, philosophical, literary, in short, 
 to construct the descriptive psychology of his moral and 
 mental state and the circumstantial analysis of his physical 
 and social medium, then, to pass from these elements to still 
 simpler elements, to discern the aptitudes and tendencies 
 which were found effective and preponderant in all the pro- 
 cesses of his mind and heart, to note the general conceptions 
 which determined every detail of his ideas, to mark the gen-
 
 490 THE KNOWLEDGE OF GENERAL THINGS. [BooK IV 
 
 eral inclinations which determined the directions of all his 
 actions ; in short, to distinguish the primordial forces which, 
 present and in action at each moment of the life of each in- 
 dividual, impress on the total group, that is to say on the 
 society and the age, the characters which observation has rec- 
 ognized there.* Wherever we are able thus to isolate and 
 observe the elements of a compound, we can, from the prop- 
 erties of the elements, explain the properties of the com- 
 pound, and, from a few general laws, can deduce a host of 
 particular laws. This is what we have done here ; we have 
 first descended by degrees to the ultimate elements of cog- 
 nition, to ascend thence stage by stage up to our simplest 
 cognitions, and thence, still by degrees, up to more complex 
 ones ; in this scale, each step possesses its characters by the 
 intervention of characters which were manifested in the lower 
 steps. 
 
 This is why, when, in this progressive decomposition, we 
 arrive at compounds in which our consciousness, senses, and 
 instruments are unable to discover simpler elements, expla- 
 nation is at a standstill and is reduced to conjectures. On 
 our road we have met with sensations, those of touch, smell, 
 and taste, in which we have been unable to distinguish ele- 
 mentary sensations, and all that analogy permits us is to con- 
 ceive that there are such. A similar limit is created by a 
 similar difficulty in the other experimental sciences. By 
 means of the microscope, physiologists and embryogenists 
 have resolved living tissues into anatomical elements, little 
 bodies which are most frequently cells of various forms and 
 variously grouped ; but they have not grasped the elements 
 of the cell, they are ignorant of their properties, at least, 
 they are not at present ignorant of them; in the liquid form- 
 less pulp which becomes organized into a little cell furnished 
 with a nucleus, they are unable to distinguish the particles and 
 d fortiori to distinguish their properties. At the most, they 
 conjecture that these elements are chemical molecules of ex- 
 
 * I have attempted to apply this method in many historical essays, and have 
 explained it in the preface to " Essais de Critique et d'Histoire," and in that to 
 " Historic de la Litteraturc Anglaise."
 
 CHAP. III.] THE EXPLANATORY REASON, 49! 
 
 treme complexity, and that their mutual reactions group 
 them in a certain visible form. So again, chemists and phys- 
 icists establish by their experiments that the ultimate par- 
 ticles of a homogeneous body are molecules or little masses 
 exactly alike, that, if the body is simple like oxygen, each 
 molecule is simple and consists entirely of oxygen ; that, if 
 the body is compound like water, each molecule is composed 
 of two or more little elementary masses, one of which is 
 oxygen and the other hydrogen. But as to these molecules, 
 no one has seen or can see them ; we are ignorant of their 
 form, their weight, their distance, their mutual situation, the 
 magnitude of the attracting and repelling forces which main- 
 tain them in equilibrium, the amplitude and velocity of the 
 vibrations which we suppose they have about a supposed 
 centre of oscillation. At the most, following these indica- 
 tions, we conclude that, from these unknown properties, are 
 derived the known properties of the whole body, the greater 
 or less affinity it has for some other body, the reaction it ex- 
 cites or undergoes, the property it has of combining with 
 some other body in definite and invariable proportions, the 
 equivalence of a certain weight of the first and a certain 
 other weight of the second to combine with the same weight 
 of a third, etc. 
 
 In face of elementary sensations, living cells, chemical 
 molecules, ethereal atoms, the scientific man is in the posi- 
 tion of a short-sighted person before ant-hills of various kinds ; 
 his dull sight can only attain effects of the mass, changes of 
 the whole, the entire form of the edifice ; the little workmen 
 escape him ; he does not see them labor. He can take a 
 quarter or half of one of their constructions, can upset it 
 with its inhabitants on another, can observe, first, an agita- 
 tion, a confusion, then an abatement, an arrangement, and a 
 new development ; nothing more. As he is a skilful handler 
 of experience and induction, he has finally recognized that 
 there are in each heap invisible inhabitants, and in each dif- 
 ferent heap different inhabitants, that certain mixtures suc- 
 ceed better than others, that it is always necessary to pre- 
 serve certain proportions, that after the mixture the new 
 edifice presents characters which are not manifested in either
 
 492 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV 
 
 of the two unmixed heaps. But he would require far "more 
 piercing eyes to discover the economy of the two primitive 
 constructions, the instinct of their ants, the dealings set up 
 between the two associated populations, and the final econ- 
 omy of the subsequent edifice which they together construct. 
 Assume that, in these societies of molecules we term bodies, 
 the inhabitants and materials are one and the same thing ; 
 the comparison will be exactly applicable. 
 
 Thus, at a certain limit, our explanation is at a standstill, 
 and though, from age to age, we push it further on, it is 
 possible that it may always stop before a certain limit. If 
 ever we know exactly the form, distance, magnitude, and 
 weight of molecules of oxygen or sodium, as well as the am- 
 plitude and velocity of their oscillations, we shall perhaps be 
 in face of a system analogous to our solar system, a kind of 
 vortex whose roughly similar elements require a further de- 
 composition, and whose properties only admit of explanation 
 by the wholly different properties of their elements so again, 
 with the elements of their elements, and so on, up to infinity. 
 For magnitude is always relative ; there is nothing to prevent 
 our molecules from having as elements different molecules as 
 small with relation to them as they themselves are with rela- 
 tion to a planet, and so on, without truce or termination. In 
 this case, the successive layers of more and more simple 
 factors would differ as the successive digits of a non-recurring 
 decimal. Perhaps, on the other hand, at a certain point of 
 decomposition, all difference between the compound and the 
 factors is at an end, and the properties of the compound are 
 nothing more than the sum of those of its factors, just as the 
 whole weight of a body is nothing more than the sum of the 
 weights of its molecules; in which case the limit would be 
 attained, since, knowing the properties of the compound, we 
 should thereby know the properties of its final elements. In 
 this case, the successive layers of more and more simple 
 factors v/ould be similar, after a certain limit, as are, after a 
 certain limit, the successive digits of a recurring mixed frac- 
 tion. But whether the properties of the compound arid its 
 factors are similar or different is of no importance ; and we 
 invariably direct our observations or conjectures to the proper-
 
 CHAP. III.] THE EXPLANATORY REASON. 493 
 
 ties of the factors. The structure of things, then, is the same 
 in the sciences of experience as in those of construction, and, 
 in both, the explanatory and demonstrative intermediate 
 which serves as a link between any property and any com- 
 pound is a character, or a sum of characters, different or 
 similar, included in the elements of the compound. 
 
 IV. There remains a surplus of requirement special to 
 the experimental sciences. When we construct by thought 
 some number, some polygon, or some cylinder, we have not 
 to explain its origin ; it does not in fact exist in nature ; it 
 is possible only, and not real. Perhaps indeed, with a na- 
 ture constituted like that which we observe, it is not possi- 
 ble ; but this is unimportant. We suppose its elements 
 combined in the required manner, and explain by their prop- 
 erties the properties of the construction thus effected, with- 
 out encumbering ourselves with the inquiry as to the forces 
 by which they were themselves assembled. It is enough for 
 us that the compound is given ; we do not inquire why it is 
 given. Things do not happen thus when real compounds 
 are in question. We are bound to explain their properties 
 by the properties of their elements, and further, to explain 
 the concurrence of their elements. Then come in questions 
 of origin, the most curious, but most difficult, of all. For, as 
 this concurrence is in most cases of very great antiquity, and 
 can have had no witnesses, we can neither observe it directly 
 nor know it by tradition, and are reduced to conjecture it from 
 present concurrences, which are but approximately similar, 
 and are sometimes entirely wanting. All the experimental 
 sciences have thus their historical chapter, more or less con- 
 jectural, according as more or less precise indications, more 
 or less correct analogies, more or less complete records, per- 
 mit our mental reconstruction more or less exactly to replace 
 the missing evidence of our consciousness or our senses. 
 
 For instance, there is a question for the astronomer, as 
 to the formation of the various planets, for the geologist, as 
 to the formation of the successive strata of the outer crust of 
 the globe, for the mineralogist, to discover how the different 
 rocks were formed, for the naturalist, to know how our species 
 of plants and animals were formed, for the historian, to de-
 
 494 TIIE KNO WLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 tect the formation of the successive epochs of one and the 
 same human society-, and the different traits of a national 
 character. They all start from an anterior state denoted by 
 converging indications, or attested by transmitted records, 
 and from this probable or certain state they deduce, accord- 
 ing to existing laws, the following state, then the next follow- 
 ing state, and so on, up to the existing state. 
 
 Thus Laplace assumes that our system was at first an im- 
 mense nebula extending round a central nucleus ;* that this 
 vast atmosphere, becoming condensed as it cooled, was divi- 
 ded into concentric zones of vapor similar to the rings of Sat- 
 urn ; that, by a subsequent condensation and cooling, these 
 zones became collected into planets, which were first gaseous, 
 then liquid, then solid ; and, from this gradual condensation, 
 combined with the law of gravitation, he deduces, by a mar- 
 vellous adjustment, the principal characters and even the 
 singular peculiarities which our system nowadays presents. 
 Taking up this supposition at the point where Laplace left 
 it, geologists trace with probability the thickening of the ter- 
 restrial crust, and explain, from epoch to epoch, with gaps be- 
 coming gradually fewer, the deposition and superposition of 
 the strata, their partial upheavals, their erosions, their rup- 
 tures, the present disposition of our continents and seas, by the 
 prolonged play of the mineral or organic forces in the midst 
 of which we are now still living.f At their side, their allies, 
 mineralogists and chemists, see that rocks and amalgams sim- 
 ilar to those which the earth presents are formed under their 
 hands and eyes, by slow actions, by prolonged heat, by con- 
 tinued compression, by molecular additions,:}: and from the 
 processes they now observe in their little artificial laborator- 
 ies, they draw conclusions, with fitting precautions, as to the 
 analogous processes by which the amalgam and the rock were 
 formed of old in the great laboratory of nature. 
 
 * " Exposition du Systeme du Monde," ii. 425. 
 
 \ See, as to this, Lyell's " Principles of Geology." 
 
 \ Crystals of granite have been found at Plombieres, in the concrete on which 
 the Romans built. They have been formed there by the infiltration of water for 
 eighteen hundred years. M. Daubree and M. de Senarmont have produced in 
 their laboratories a great number of natural compounds.
 
 CHAP. III.] THE EXPLANATORY REASON. 
 
 Here come in the naturalists. Darwin starts with a fun- 
 damental character common to all the species of animals and 
 vegetables, the struggle for life, from which there follows the 
 destruction of all individuals less properly adapted to their 
 medium, the exclusive survival of the individuals best adapt- 
 ed to their medium, the privilege these have of propagating 
 the race, the successive acquisition of useful characters, the 
 transmission to descendants of all the accumulated treasure 
 of useful characters, and finally, through this, the progressive 
 modification of the species, the gradual perfectionment of the 
 organs, and the slow adaptation of the individual to its defin- 
 itive medium. Provided with this existing law, he explains, 
 by its former presence, the assemblage of the organs of which 
 Geoffrey Saint-Hilaire and Cuvier had ascertained the prop- 
 erties. By one of these properties the organ is a part in a 
 plan and in a type ; that is, the legacy of a common ancestor. 
 All mammals are descended from a mammal* " which had its 
 limbs constructed on the existing general pattern which we 
 now find throughout the whole class." All insects are de- 
 scended from an insect " which had an upper lip, mandibles, 
 and two pair of maxillae, these parts being perhaps very simple 
 in form." If the type is found to be the same throughout so 
 many different species, it is because all these species repeat, 
 by virtue of inheritance, the characteristics of their common 
 progenitor. By the other of these properties, the organ is a 
 useful instrument which brings its structure and function into 
 harmony with those of the others, in such a way that the dif- 
 ferent species can subsist in their different media ; this is be- 
 cause, owing to continuous selection, the common pattern be- 
 queathed by the common progenitor is modified, here in one 
 direction, there in another, so as to accommodate its details 
 to the differences and changes of the medium. The same 
 parts of the same limb become thin and elongated in the bat- 
 shortened and soldered in the whale, so as to be fitted for fly- 
 ing in the first case, and swimming in the second. If the 
 type varies from species to species, it is because circumstances 
 
 * Darwin, on " The Origin of Species," p. 435. See, as to the theory of evo- 
 lution as a whole, the very bold, precise, and most suggestive work of Ht_iLcn 
 Spencer, " Principles of P.iology."
 
 496 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 have varied from group to group, and the variety of circum- 
 stances has produced the variety of acquisitions. When this 
 is settled, we are capable of tracing mentally through the im- 
 mense duration of geological periods, from the protococcus and 
 amoeba up to man, the formation, addition, and assemblage 
 of the parts which now constitute an organized body. It is a 
 living edifice in which selection has superimposed, from spe- 
 cies to species, and upon a common type transmitted by in- 
 heritance, useful differences. Just as, in a house, the carpen- 
 ters and masons first construct the walls and lay down the 
 floors, after which come joiners, painters, and upholsterers to 
 arrange the apartments. We see that the second set of work- 
 men has succeeded to the first, to resume and complete the 
 commenced construction. And so, many generations of an- 
 cestors have successively labored to construct each of our spe- 
 cies. One of these generations, the primitive and most an- 
 cient of all. has established the most general type which is 
 common to all animals of every subkingdom, articulate or 
 vertebrate. The second, a later one, issuing from this last, 
 has superimposed differences which constitute the class that 
 is to say the bird, the fish, or the mammal. Then has come 
 the third, which starting with the mammal, has elaborated 
 the transmitted work and formed families that is to say the 
 cetacea, the cheiroptera, the ruminantia, the carnivora, the 
 primates. Then, finally, have the descendants of the pri- 
 mates, by their distinct developments and increasing diver- 
 gencies, constituted genera, the gorilla, the orang-outang, and 
 man, the latter being distinguished from the rest by a partic- 
 ular conformation of limbs, and a more delicate structure of 
 the brain. 
 
 Here comes in the historian : he takes a people at a given 
 moment. By the combined influence of the former state and 
 of hereditary aptitudes and faculties, he explains the social, 
 intellectual, and moral state at the given moment ; by the 
 combined influence of this new state and of the same heredi- 
 tary aptitudes and tendencies, he explains the social, intel- 
 lectual, and moral state at the later moment, and so on, either 
 by reascending the course of time from the contemporary 
 epoch up to the most ancient beginnings of history, or by de-
 
 CHAP. III.] THE EXPLANATORY REASON. 497 
 
 scending the course of time from the most ancient beginnings 
 of history down to the contemporary epoch. We may con- 
 ceive that in this prodigious evolution, which extends from 
 the formation of the solar system to that of modern man, the 
 gaps are great and numerous ; this is in fact the case, and our 
 materials for filling them are often reduced to conjectures. A 
 history like this is a torn, blotted book, in which some chap- 
 ters, the last especially, are almost entire, in which, of other 
 earlier ones, there subsist but two or three scattered pages, 
 in which, of the earliest chapters, the titles alone remain. 
 But every day a new discovery restores a page, and the sagac- 
 ity of scientific men has detected some portion of the general 
 thought. Thus it is that, within the last fifteen years, we 
 have rediscovered the traces and marked the successive ad- 
 vances of the human race preceding our geological epoch ; 
 and an entirely recent law, that of the conservation of force, 
 derives by transformation all existing forces from the primi- 
 tive forces which the nebula of Laplace comprised in its ear- 
 liest state.* 
 
 From all these great fragments of rigorous or approxima- 
 tive explanation, a universal truth is manifested : that the 
 question of origins is no more mysterious than that of char- 
 acters. When given a compound, its properties are explained 
 by the properties of its united elements. When given this 
 union, it is explained by the properties of these same ele- 
 ments and by the antecedent circumstances. It is, like so 
 many others, an effect only, and, like all the others, it has as 
 reason the combined presence of a group of fixed with a 
 group of changing conditions. To form the planet, there was 
 a fixed state, the gravitation of the gaseous molecules carried 
 round the central nucleus, and a changing condition, the pro- 
 gressive cooling and consequent gradual condensation of these 
 same molecules. To form the species, there was a fixed con- 
 dition, the transmission of an older general type, and chang- 
 ing conditions, the new circumstances which, selecting the 
 subsequent ancestors, added to the type the characters of the 
 species. To form a particular historical epoch, there was a 
 
 * See, as to this, Helmholtz, " Metnoire sur la Conservation de la Force" (tr. 
 Purard), pp. 31-34 et seq. 
 32
 
 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 fixed condition, the maintenance of the national character, 
 and a changing condition, the new state in which the nation 
 happened to be placed on emerging from the preceding epoch. 
 Hence it follows that, in questions of origin, as in other 
 questions, there is an explanatory and demonstrative interme- 
 diate, that the re-union of the elements has its reason of exis- 
 tence, just as the characters of the compound have their rea- 
 son of existence, that it is, like them, a product, and that all 
 the difference between the two products consists in this, that, 
 as the first is historical and the second not historical, the first 
 comprises a factor more than the second, namely, the influ- 
 ence of the historical moment, that is to say of the prelimin- 
 ary circumstances and the antecedent state. 
 
 HI- 
 
 I. Let the reader now collect and glance over the conclu- 
 sions to which we have just arrived ; he will find that they 
 converge, and will be led by their convergence, towards a 
 universal law of a higher order, which governs every law. 
 Take any couple whatever of any data whatever ; as soon as 
 they are actually connected, there is a reason, a because, an 
 intermediate which explains, demonstrates, and necessitates 
 their connection. This is true for cases, or couples of par- 
 ticular data, just as for laws strictly so called, or couples of 
 general data ; there is a reason for the fall of this leaf which 
 has just come to the ground, and for the gravitation of all 
 the planets towards the sun, for this night's dew, and for the 
 liquefaction of all vapor, for the beat of the pulse I feel at 
 this very moment in my wrist, and for the presence of any 
 function or apparatus in any living being. It is true for the 
 laws in which the first datum is a more complex compound, 
 as for the laws in which the first datum is a more simple 
 compound ; there is a reason for the total acts of a human 
 society, and for the individual acts of its members, for the 
 properties of a chemical compound, and for the properties of 
 its constituent substances, for the effects of a machine, and 
 for the effects of its wheelwork. It is true again for the laws 
 concerning mental compounds as for the laws concerning 
 real compounds; there is a reason for the properties of
 
 CHAP. III.] THE EXPLANATORY REASON. 
 
 499 
 
 the ellipse or cylinder as for the properties of water or of 
 granite. It is true again for the laws governing the forma- 
 tion of a compound as for those by which it possesses its char- 
 acters ; there is a reason for the formation, as well as for the 
 properties, of a planet or of a species. But the most remark- 
 able point is, that it is true for the laws whose explanation is 
 still wanting as for those whose explanation we now possess. 
 There is a reason for the attraction which all masses exercise 
 on one another, for the properties of oxygen, for the forma- 
 tion of a living cell, for the origin of our nebula. At all 
 events, we believe this. We cannot show this reason, but we 
 are persuaded that it exists ; we anticipate it by a bold affirm- 
 ation as to our future discoveries, and even as to discoveries 
 which perhaps we shall never make. 
 
 Besides this, we indicate beforehand the position and 
 principal characteristics of the intermediate which still escapes 
 us. We assume that if two masses attract one another, it is 
 by virtue of a simpler and more general character, included in 
 the group of characters which constitute these masses, such 
 as would be an incessantly repeated impulsion superadding 
 at every moment an effect to the preceding effect, which we 
 express by saying that attraction is a force whose action is 
 not momentary but continuous, which enables us to conceive 
 the velocity of the falling mass as the sum of all the velocities 
 acquired since the first moment of its fall, which has led some 
 physicists to explain the attraction of two masses by the 
 continuous impulsion of a surrounding ether. We assume 
 that if oxygen presents such or such characters, it is by 
 virtue of simpler and more general characters appertaining to 
 its elements, and consisting of the masses, distances, and 
 internal movements of its component atoms. We assume 
 that if a formless liquid becomes organized into a cell, it is 
 owing to the mutual reactions and previous state of the very 
 complex particles of which it is the aggregate, and that if 
 our nebula formerly sprung into being, it was due to the forces 
 of its molecules, and to the influence of a previous state which 
 vre cannot, even by conjecture, represent to ourselves. In 
 our view, not only does the explanatory and demonstrative 
 intermediate exist in all these couples, though it may elude
 
 5QO THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 our grasp ; but further, it is a simpler and more general char- 
 acter than the first datum of the couple, it is included in that 
 datum and appertains to its elements, and the properties of 
 that datum, as well as its origin, have as their ultimate reason 
 of existence the characters and previous state of its ultimate 
 elements. 
 
 On these indications, our thought flies off to extend this 
 structure of things beyond our world and history, throughout 
 the two gulfs of space and time, beyond all the distances to 
 which imagination can attain, beyond all the confines which 
 numbers or quantities, fruitlessly swollen and heaped to- 
 gether, can denote to the pure reason. Are we justified 
 in acting thus? And what motives can we allege to au- 
 thorize a supposition which anticipates, not only all future 
 experience, but all possible experience, and involves in the 
 immensity of its forecast the immensity of the universe? 
 
 II. Two series of cases confront us, a considerable one 
 made up of all the facts and laws whose reason we know, 
 another prodigiously disproportioned and infinitely greater, 
 since it is infinite and made up of all the facts and laws whose 
 reason we do not know. Here are two indications, one 
 positive, the other negative, one favorable to our supposi- 
 tion, the other seemingly unfavorable. But this unfavora- 
 bleness is apparent only. For if, when we know the reason 
 of a fact or law, we can conclude its existence, we cannot, 
 from our ignorance of it, conclude its absence. This reason 
 may exist, though unknown, and, in fact, if we look back on 
 the past states of our knowledge, we find that on many oc- 
 casions it existed, though unknown. We see daily, in pro- 
 portion as science becomes extended and precise, the first 
 series increasing at the expense of the second, and analogy 
 leads us to believe that cases still comprised in the second are 
 similar to those which have ceased to be comprised in it. 
 The further our extended experience drives back our horizon 
 in time and space, the more explanatory reasons do we add to 
 our store. It is sufficient to examine the history and nature 
 of experimental science to recognize that, if there were or 
 still are voids in this store, it never arises from the explana- 
 tory reason failing or having failed in things, but always from
 
 CHAP. III.] .THE EXPLANATORY REASON. 501 
 
 its failing or having failed in our minds. It was existing in 
 nature ; but scientific men were imperfectly instructed, and 
 had not yet discovered it. It now exists in nature ; but we 
 are unable, and perhaps shall never be able, to detect it there. 
 The gap arises not through its absence, but through our ig- 
 norance or impotence, and the fault is not in things, but in 
 ourselves. If in Kepler's days the motion of the planets 
 could not be explained, it was because gravitation was then 
 unknown. If, at present, we are unable to explain why pure 
 carbon, according to its different states, furnishes, with the 
 same molecules, compounds as different as the diamond and 
 graphite, it is because we do not know the velocities and 
 masses of its molecules, and so cannot define their various 
 states of equilibrium. To detect the explanatory reason, 
 as we have defined it, certain conditions are required, and 
 if these conditions are not fulfilled, the reason may indeed be 
 present, we shall not be able to distinguish it. To detect the 
 reason explaining the characters of a compound like graphite, 
 it is necessary that we should know the properties of its ele- 
 ments, the molecules of carbon. To detect the reason which 
 explains the origin of the first organic compound, it is neces- 
 sary that we should know, besides the properties of its ele- 
 ments, the primordial circumstances in which they were 
 assembled. This is why we shall be unable, while these 
 preliminaries fail us, to know the explanatory reason. So 
 long as they are attained by simple conjecture, it will be at- 
 tained by simple conjecture, and we shall be at a greater or 
 less distance from it, according as we are a greater or less 
 distance from them. Hence it follows that our ignorance of 
 it is never an indication of its absence, from which it follows 
 that we have no ground to suppose its absence, at any period 
 even for events which preceded the origin of our nebula, or 
 at any place even beyond the furthest points of the visible 
 firmament. That our experimental science has gaps is incon- 
 testable : but its structure is sufficient to account for them, 
 and it is against all the rules of hypothesis to account for 
 them by the arbitrary and useless addition of an unascer- 
 tained cause to the ascertained cause which is sufficient. 
 
 Excluded on one side, presumptions are compelled to turn
 
 5O2 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 to the other. As there is no choice except between the pres- 
 ence and absence of the explanatory reason, the chances, 
 when no longer in favor of its absence, become in favor of 
 its presence, and the balance inclines towards the other scale. 
 It would incline further still in this direction if we could 
 point out sciences free from the conditions imposed on ex- 
 perimental science, and thereby finding an explanatory reason 
 for all their laws. For such a contrast would afford room 
 for the belief that the gaps of experimental science have 
 the conditions to which it is subject, not only as their 
 sufficient, but also as their single cause ; from which it would 
 follow that experimental science, when freed from thes*e con- 
 ditions, would thereby fill up these gaps, and that the explan- 
 atory reason, being everywhere discovered, would exist every- 
 where. Now this is precisely the contrast presented by the 
 sciences of construction when compared with the sciences of 
 experience. In the first, all the explanatory and demonstra- 
 tive intermediates which connect any property to any com- 
 pound, from the first to the last, are known and therefore 
 exist ; there is not one of their laws which does not manifest, 
 and which therefore does not possess, its because and its rea- 
 son. It is to be presumed, then, that if we could employ in 
 our experimental sciences the processes we employ in our 
 sciences of construction, we should arrive at the same dis- 
 coveries, and that just as every law in the last has its reason 
 of existence, so has every law in the first. 
 
 This probability becomes stronger still, when we observe 
 that the laws of the second may be discovered, like the 
 laws of the first, by the inductive method, and that if we 
 follow this method in the second as in the first, the reason of 
 the law then remains unknown though present. Conse- 
 quently, the inductive process is the sole cause of our ignor- 
 ance in this case : hence it follows with all probability that 
 in other cases, that is to say in the experimental sciences, it 
 is still the sole cause of our ignorance, and that, in other 
 cases as in this, the explanatory reason is always present, 
 though it may always elude us. In fact, suppose, as we did 
 before,* the case of a man of very exact and very patient mind, 
 
 * Part ii, book iv., chap, ii, p. 451.
 
 CHAP. III.] THE EXPLANATORY REASON, 503 
 
 very skillful at induction, but capable of induction only ; we 
 request him to ascertain the number of right angles to which 
 the angles of any quadrilateral are together equal. Let us 
 assume this time that he has at hand a number of perfect 
 quadrilaterals, that his instruments of measurement are per- 
 fect, and that he applies them with perfect exactness. By a 
 series of inductions similar to those we have described, he 
 will finally discover that the angles of every quadrilateral of 
 whatever kind, trapezium, parallelogram, rhombus, rectangle, 
 or square, are together equal to four right angles ; but 
 his knowledge of quadrilaterals will stop here, that is to say 
 at the point attained by the most advanced branches of our 
 experimental science. He will ascertain a law which will be 
 inexplicable to him, just as some chemical or physical law is 
 inexplicable to us. He will have connected to every quadri- 
 lateral a constant property, the equality of its angles to four 
 right angles, as we connect to every white crystal of carbon 
 a constant property, octohedric structure. But he will not 
 have discovered, any more than ourselves, the intermediate 
 which necessitates the connection. In his case, this interme- 
 mediate is a property of the two elementary triangles of which 
 the quadrilateral is the possible sum. In our case, this inter- 
 mediate is a property of the elementary molecules of which 
 the white crystal of carbon is the real sum. He will miss his 
 intermediate, then, as as we miss ours, by a defect of method, 
 which can be remedied in his case, but which cannot be reme- 
 died in ours. We have, then, every ground for belief that if, 
 like him, we could apply a remedy, and if to inductive ex- 
 perience we could add, in our case, as in his, deductive analy- 
 sis by way of supplement, the attained intermediate would 
 manifest its presence in our case as it does in his. 
 
 We thus arrive at considering the sciences of construction 
 as a preliminary copy, a reduced model, an indication reveal- 
 ing to us what the sciences of experience might be, an indi- 
 cation similar to the little waxen edifice which architects 
 construct beforehand with a more manageable substance, to 
 represent on a small scale the proportions and total aspect of 
 the great monument they are in process of erecting, and 
 which perhaps they will never complete. In fact, if we look
 
 504 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 at the ideal and the real world, we perceive that their struc- 
 ture is similar. In the first, as in the second, there are ele- 
 ments and compounds, elements of elements and compounds 
 of compounds, objects capable of being classified, species, 
 genera, and families, families of lines and surfaces ranged be- 
 neath one another according to the degree of their equations, 
 less general laws explained by more general laws, and a num- 
 ber of other characteristics no less essential, and common to 
 both. Therefore, the two orders are analogous. But, be- 
 sides, all the materials of the first are found in the second. 
 For we have seen that numbers, lines, surfaces, solids, mo- 
 tions, velocities, forces, exist, not only in the mind, but also 
 in nature; it is in nature that the mind discovers them, and 
 from nature that it extracts them. All its special work con- 
 sists in combining them in its own way, without troubling it- 
 self to inquire whether there are in nature real outlines which 
 adapt themselves to the mental outlines, whether there is any 
 actual sphere or ellipse corresponding to the ideal sphere or 
 ellipse. There remains, then, a single difference which separ- 
 ates our artificial compounds from natural compounds ; the 
 first are more simple, and the second more complex ; Euclid's 
 straight line is simpler than the imperceptibly bent line 
 which a ball describes in the first metre after it leaves the 
 cannon ; the slightly indented ellipse described by a planet 
 is more complex than the geometrical ellipse. For this rea- 
 son we study the mental compound before the real com- 
 pound, and the knowledge of the first leads us to the know- 
 ledge of the second. Herein lies the whole secret of the ser- 
 vices which the sciences of construction render to the sciences 
 of experience ; thus it is that the first have their application 
 in the second. Given two compounds, one mental, the other 
 real, they become adapted to one another with this differ 
 ence, that the second comprises supplementary and perturb 
 ing elements in addition to the elements which constitute 
 the first, and this renders the first simpler, and the second 
 more complex. We take account, by turns, of this general 
 adaptation and this subsidiary difference. We discover by 
 the sciences of construction, the properties of the first com- 
 pound, the geometrical straight line or ellipse ; then, on ac-
 
 CHAP. III.] THE EXPLANATORY REASON. 505 
 
 count of this general adaptation, we attribute them provi- 
 sionally to the path of the bullet or the planet's ellipse ; and 
 thus obtain ideas which are almost, but not wholly, exact 
 Having done this, on account of this subsidiary difference, 
 we gladly introduce into our ideas the supplementary and 
 perturbing elements in nature which bend the path of the 
 ball or indent the planet's ellipse. Thus, from the provisional 
 path and ellipse, which were too simple, and therefore ap- 
 proximate only, the mind passes gradually to the definitive 
 path and ellipse which, while growing complicated, become 
 exact. By this progressive rectification, our idea, which was 
 at first rigorously adjusted to the ideal compound only, finally 
 becomes rigorously adjusted to the real compound. It was 
 in a science of construction that it took its origin, and it is 
 in a science of experience that it finds its use. 
 
 Hence follows a consequence of capital importance, that 
 at every place and time, outside our history and world, as 
 well as in our history and world, the theorems are capable of 
 being applied. In fact, it is sufficient for this that the real 
 compounds, whether near or distant, should enter into our 
 mathematical outlines, and they necessarily enter them, when 
 they have number, situation, or form, when they possess mo- 
 tion, velocity, or mass, when they are subject to forces, that 
 is to say to any conditions of motion. Stuart Mill, then, is 
 wrong to say that " in distant parts of the stellar regions, 
 where the phenomena may be entirely unlike those with which 
 we are acquainted, it would be folly to affirm confidently the 
 prevalence of any law, general or special," and that, " any one 
 accustomed to abstraction and analysis, who will fairly exer- 
 cise his faculties for the purpose, will, when his imagination 
 has once learnt to entertain the notion, find no difficulty in 
 conceiving that in some one, for instance, of the many firma- 
 ments into which sidereal astronomy now divides the uni- 
 verse, events may succeed one another at random, without 
 any fixed law ; nor can anything in our experience, or in our 
 mental nature, constitute a sufficient, or indeed any, reason 
 for believing that this is nowhere the case." No doubt it is 
 possible that bodies do not there attract one another. But 
 there, as with us, if, through the application of any force, a
 
 506 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 body takes, for a time as short as we please, a uniform recti- 
 linear motion, it will tend to continue it indefinitely ; for, the 
 axiom being necessary, as soon as the first of its two data ex- 
 ists in fact, the second cannot fail to exist in fact. And 
 moreover, whatever be the body and whatever be its motion, 
 if this motion be regarded in a purely mechanical aspect, it 
 will, there as with us, be necessarily wholly determined by 
 the magnitudes and directions of the forces whose effect it is ; 
 so that, there as with us, it will be found by the solution of a 
 mechanical problem, and will only resist solution, if the com- 
 plication of its elements be so great that our formulae are not 
 yet sufficiently advanced to comprehend them ; for, not only, 
 as we have seen, are the sciences of construction, being nec- 
 essary, universal, but again, their application is thereby uni- 
 versal. Indeed real compounds, so far as they are formed of 
 the same elements as mental compounds, are subject to the 
 same universal and necessary laws, and nature, in this aspect, 
 is nothing more than applied arithmetic, geometry, and me- 
 chanics. 
 
 It remains to be seen whether nature is not more than 
 this. Now, as far as we can judge, and according to recent 
 discoveries, all changes of a body, physical, chemical, or vital, 
 are reduced to movements of its molecules ; and so again, 
 heat, light, chemical affinities, electricity, gravity itself per- 
 haps, all forces producing these changes and producing move- 
 ment itself, are reduced to movements. Hence it follows 
 that in visible nature there are nothing but bodies in mo- 
 tion, bodies motor or movable, motor and movable in turn, 
 motor when their preliminary motion is the condition of the 
 motion of another, movable when their consecutive motion 
 is the effect of the motion of another ; which reduces all 
 corporeal change to the passage of a certain quantity of 
 motion transferred from the motor to the movable body, an 
 operation which, as we are assured, takes place without gain 
 or loss, so that at the end of the circuit, the expenditure is 
 exactly covered by the receipt, and the final force is found 
 to be equal to the initial force. If this admirable reduction 
 were true, first for our world, and then besides for all beyond 
 our world, not only all our physical, chemical, and physiolo-
 
 CHAP. III.] THE EXPLANATORY REASON. 50? 
 
 gical problems, but further all problems concerning any 
 actual body whatever, would be at bottom pure mechanical 
 problems. Observable compounds would differ in nothing, 
 except complication, from constructed compounds ; and just 
 as the formation, properties, alterations, and transformations 
 of every mental compound, whether arithmetical, geometri- 
 cal, or mechanical, have their reason of existence, so would 
 there be a reason of existence for the formation, properties, 
 alterations, and transformations of every real compound. 
 
 III. We have here considerable probabilities, and may 
 sum them up by saying that there is no analogy to authorize 
 our supposing the absence, in any case, of the explanatory 
 reason, while many analogies lead us to suppose its presence 
 in all cases. Still we have here probabilities only, and must 
 examine whether the enounced principle has no better sup- 
 port. On commencing any new inquiry, scientific men as- 
 sume the principle, and indeed, are compelled to do so ; for, 
 without it, as we have seen, they could' not perform induc- 
 tion.* Given any phenomenon, they invariably assume be- 
 forehand conditions forming its reason of existence and whose 
 reunion is sufficient to produce it, so that the phenomenon 
 cannot fail in any of the cases in which these conditions are 
 reunited. " There is an absolute determinism," says Claude 
 Bernard,f " in the conditions of existence of natural phe- 
 nomena, as well for living, as for inanimate bodies. . . . When 
 the condition of a phenomenon is once known and fulfilled, 
 the phenomenon must invariably and necessarily be repro- 
 duced at the will of the experimenter. .... Phenomena 
 can never contradict one another if they are observed under 
 the same conditions ; if they exhibit variations, this neces- 
 sarily depends on the intervention or interference of other 
 conditions which cloak or modify these phenomena. Hence 
 there is room for attempting to know the conditions of these 
 variations ; for we could not have the effect there, without 
 a cause. This determinism thus becomes the basis of all 
 scientific progress and criticism. If, on repeating an experi- 
 
 * Part ii. book iv. chap. ii. p. 434, ante. 
 \ " Introduction a 1'etude de la Medecine Experimentale," pp. 115 et seg.
 
 50S THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 ment, we find discordant or even contradictory results, we 
 ought never to admit real exceptions or contradictions, for 
 this would be anti-scientific ; we must simply and necessarily 
 conclude that there are differences of conditions in the phe- 
 nomena, which may or may not here explain them. . . . As 
 soon as the laws are known, we cannot have exceptions. . . . 
 We must forcedly admit as an axiom that, in identical con- 
 ditions, every phenomenon is identical, and that as soon as the 
 conditions are no longer the same, the phenomenon ceases 
 to be identical." We see that the words necessarily, forcedly, 
 axiom, are here employed. Helmholtz employs equivalent 
 expressions.* According to him, we cannot otherwise con- 
 ceive the world. Our eyes cannot perceive extension except 
 as colored ; and so, our intelligence cannot conceive facts ex- 
 cept as explicable. There is nothing conceivable by us ex- 
 cept what is explicable, just as there is nothing visible by us 
 except what is colored. The internal eye has, like the ex- 
 ternal, its innate structure from which it cannot be set free, 
 and which imposes on all its conceptions a necessary charac- 
 ter. Helmholtz seems here to believe that this constraint 
 has for ultimate cause, the structure of our mind. With 
 him and Claude Bernard, we recognize the constraint as a 
 fact ; but we do not conceive its ultimate cause to be in the 
 structure of our mind ; for we have already seen many analo- 
 gous necessities of belief. There is one such for each of the 
 axioms of mathematics ; they all exert on our mind the same 
 ascendancy as the axiom of explanatory reason; and still, 
 we have demonstrated them ; we have shown that they have 
 a foundation in things, that they are valid, not only for us, 
 but in themselves, that their empire is absolute, not only 
 over our intelligence, but also over nature, that if the two 
 ideas by which we conceive them are forcedly connected, it is 
 because the two data which constitute them are also forcedly 
 connected, and that, if the constraint experienced by our 
 mind in their presence has, as first cause, our mental struct- 
 ure, it has, as ultimate cause, the adjustment of our mental 
 structure to the structure of things. It is probable, then, 
 
 " Fhysiologische Optik," p. 455.
 
 CHAP. III.] THE EXPLANATORY REASON. 509 
 
 that this great axiom is of the same nature as the rest, and 
 that analysis will, as with the rest, be sufficient to demon- 
 strate it. 
 
 Take a couple of actually connected data, one subject or 
 less general, the other attribute or more general. We ex- 
 press the same thing by saying that the subject possesses 
 the attribute. This attribute may be more or less transitory 
 or permanent ; for instance, in this falling drop of rain, the 
 fall is an entirely momentary and transitory attribute, since 
 it is at an end when once the drop has touched the earth ; 
 the chemical structure is a more permanent attribute, since a 
 chemical combination or decomposition is needed to destroy 
 it ; weight is an entirely permanent attribute, since there is 
 no known circumstance which can suppress it. Here, as in 
 all true propositions, the subject possesses the attribute, 
 whether transitory or permanent, and, as we see, the attri- 
 bute is more general than it, that is to say, common to other 
 subjects than it. I say now that there is an explanatory rea- 
 son for this possession of the attribute by the subject, and, 
 by explanatory reason, is meant, as we have shown, one or 
 more characters of the subject, included in it like a fragment 
 in a whole, more abstract and more general than it, and 
 which, being themselves connected to the attribute, connect 
 the attribute to the subject. This, then, amounts to saying 
 that the attribute is not connected to the whole entire sub- 
 ject itself, but to one or more abstract and general characters 
 of the subject. 
 
 To demonstrate this proposition, let us analyze in turn 
 the attribute and the subject. We have said that the attri- 
 bute is common to the subject and to others. This means 
 that it is the same in the subject and in others. Thus the 
 fall, the chemical structure, the weight, are the same in one 
 drop of rain and in its neighbors. Thus the equality of the 
 opposite sides is the same .in this parallelogram and in all 
 parallelograms, in the right-angled parallelogram and in the 
 parallelogram whose angles are not right. Therefore, to say 
 that the subject possesses an attribute common to it and to 
 others, is to say that other subjects, real or possible, pos- 
 sess the same attribute as it. The equality of the opposite
 
 510 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 sides is the same in my parallelogram and in this other one ; 
 the chemical structure is the same in my drop of rain and in 
 this other one. In other words, taken in itself, with the 
 omission and suppression of the distinct subjects in which 
 they reside, the equality of the opposite sides of my parallel- 
 ogram is confounded with the equality of the opposite sides 
 of the other, and the chemical structure of my drop of rain 
 is confounded w r ith the chemical structure of the other, just 
 as a particular triangle, when detached from the position it 
 occupies, and transferred by superposition upon some other, 
 coincides with the other and is absolutely confounded with it. 
 
 Let us now consider the subject. What we call a subject, 
 a distinct subject, is a sum or reunion of characters which do 
 not all occur rigorously the same in any other subject, how- 
 ever similar we may imagine it. This drop of rain, even if 
 we suppose it to have a form, volume, temperature, and in- 
 ternal structure, exactly the same as the one next to it, or fol- 
 lowing it, further possesses characters which are not possessed 
 either by the one next to it or the one following it, namely, 
 its situation in time with reference to those preceding it, and 
 in space, with reference to those surrounding it. This par- 
 allelogram, even if we suppose its sides precisely the same in- 
 length and its angles exactly the same in expansion as the 
 sides and the angles of the other, possesses in addition at least 
 one character which the other does not possess, namely, its 
 particular position in space, on my paper, or on this board. 
 The analysis is the same, if in this place of an individual 
 subject, as this drop of rain or this parallelogram, we consider 
 a more or less general subject, like the parallelogram in itself 
 or water in general. Water is liquid like mercury, and the 
 parallelogram has its opposite sides equal like the regular 
 hexagon ; but water compared with mercury, just as the 
 parallelogram compared with the regular hexagon, is a distinct 
 subject, which, being distinct, forcedly possesses, like'this drop 
 of rain, one or more characters by which it is distinguished 
 from every other more or less similar subject with which it is 
 compared. 
 
 Here, then, we arrive at this conclusion, that our sub- 
 ject, being distinct from another subject, is not the same, and
 
 CHAP. III.] THE EXPLANATORY REASON tu 
 
 nevertheless, possesses the same attribute. Let us replace the 
 terms by their definition. Distinct subject, signifies sum or 
 reunion of characters of which one or more are absent in the 
 other subject ; it is to this sum or reunion that the attribute 
 directly or indirectly appertains. Hence three possible hy- 
 potheses, and three hypotheses only. Either the attribute 
 appertains directly to the sum of reunited characters ; or it 
 appertains indirectly, that is, by appertaining to that portion 
 of the sum which is composed of characters absent in the 
 other subject, or by appertaining to the other portion. Now 
 the two first hypotheses are contradictory. In fact on the 
 one hand, the attribute cannot appertain to that portion of 
 the sum which is composed of the characters absent in the 
 second subject ; for then it would not appertain to the second 
 subject, in which those characters are wanting; now, by 
 definition, the attribute belongs to that subject. On the 
 other hand, the attribute cannot belong to the sum of the 
 united characters ; for then it would not belong to the second 
 subject, in which this reunion is wanting ; now, by definition, 
 it belongs to that subject. These two suppositions being 
 excluded, the third alone remains. Hence it follows that the 
 attribute belongs to that portion of our subject which is 
 composed of characters present in it and in the second sub- 
 ject, that is to say common to both, that is to say, general. 
 Hence it also follows that it appertains solely to a portion of 
 our subject, in other words to a fragment, to an extract, to 
 an abstract included in our subject ; which is what had to be 
 proved.* 
 
 * We have just demonstrated the axiom by means of the notion of identity ; 
 we can also demonstrate it by means of the notion of indifference ; and this sec- 
 ond demonstration is well suited to the particular form under which the axiom, 
 has been presented by Claude Bernard. 
 
 When given a subject under certain circumstances, take a second subject 
 exactly similar to the first, and in circumstances exactly similar to the first circum- 
 stances, so that there may be no difference between the first and second case but 
 that of time or place. Let us further assume that this difference is indifferent, 
 that is to say, without influence or any event which occurs in the first subject, and 
 that, in relation to this event, it may be considered as null, This supposition is 
 not always true ; the time and position have often an influence ; the same heavy 
 body falls more quickly in the second minute than in the first ; the same penclu-
 
 5i2 THE KNOWLEDGE OF GENERAL THINGS. [BOOK TV. 
 
 The axiom, thus demonstrated and understood, is readily 
 seen to reduce itself to the enunciation of the consequences 
 of a mental construction. Just as with other axioms, it 
 develops a pure supposition ; this it develops by detecting 
 something the same in the two data it connects, and it is re- 
 duced to the principles of identity, of the alternative, and of 
 contradiction. So again, it lays down no datum as real ; all it 
 establishes is an outline to which real data may adapt them- 
 selves. It does not affirm that there are in fact distinct 
 subjects, nor that two or more distinct subjects possess in 
 fact the same attribute. Experience alone can instruct us as 
 to this. But, when experience has instructed us, and when, 
 on considering all the propositions of our experimental 
 sciences, we find throughout nature distinct subjects pos- 
 sessed of the same attribute, then the axiom applies : being 
 demonstrated like a geometrical axiom, it has the same range, 
 and, like a geometrical axiom, it extends its empire, not only 
 over all fragments of duration and extension which are acces- 
 sible to our observation, but beyond and to infinity, to all 
 points of duration and extension in which two distinct subjects 
 present the same attribute. 
 
 Hence follow vast consequences, and first of all the proof 
 of the principle on which induction rests. We had only sup- 
 posed it true, provisionally and by analogy ;* we had only 
 assumed that a general character invariably indicates the 
 presence of another general character to which it is connec- 
 ted ; we are now able to demonstrate this presence. A gen- 
 
 lum oscillates differently at the bottom of a mine and at the summit of the adjacent 
 mountain. But subsequent experiences intervene to confirm or contradict our 
 supposition, and, whether confirmed or contradicted, we shall learn something by 
 it. Meanwhile, let us consider it as a pure mental construction, and see what 
 follows from it. Since, by supposition, the difference of the two cases has no 
 influence or is null, the second case is absolutely and rigorously confounded 
 with the first, and may be substituted for it as legitimately as any triangle may 
 for another equal and similar triangle ; therefore, the event which occurs in the 
 first subject will also occur in the second, or, to use Claude Bernard's expression, 
 " in identical conditions, phenomena are identical." The reader will observe the 
 analogy of the axiom thus enounced and proved with the above demonstrated 
 axioms of mechanics. 
 
 * Part ii. book iv. ch. ii. p. 434 ante.
 
 CHAP. III. J THE EXPLANATORY REASON. 
 
 eral character is an attribute, the same in several distinct 
 subjects. Now, according to the axiom, it does not appertain 
 to such or such a distinct subject directly, but to all indirectly 
 by the intermediate link of a portion common to them, and 
 which, in this respect, is a general character ; in this way, it 
 supposes the presence of another general character to which 
 it belongs; thus, its presence is sufficient to guarantee to us 
 the presence of this other. Moreover, this other character 
 to which the first appertains is general ; in other words, the 
 first appertains to the second, whatever be the subject, what- 
 ever the medium, whatever the place, whatever the moment ; 
 in other words again, the presence of this other is sufficient 
 to involve, and therefore to guarantee to us, the presence of 
 the first. Thus, in general, the presence of the one, which 
 is already known, is sufficient to guarantee to us the presence 
 of the other, which is as yet unknown, and which we are 
 attempting to discover. Now, we have seen that on this 
 sufficiency are founded all the processes of elimination, the 
 methods of agreement and difference, of which induction is 
 composed. 
 
 On the other hand, take any subject considered at two 
 successive moments, and in which some particular attribute 
 is the same at both moments, that is to say common to the 
 two moments, and consequently, general. After what we 
 have just said, this attribute has its condition, which is a 
 character common to both moments of the subject ; and, as 
 its condition is sufficient to involve it, while its condition 
 persists, it will itself persist. Consequently, if, in fact, at the 
 third moment it ceases to exist, this is because its condition 
 has ceased to exist ; hence it finally follows that the suppres- 
 sion of a character has, as condition, the suppression of another 
 character. Now every alteration in a subject is the suppres- 
 sion of one of its characters, so that every alteration has a 
 condition, which we express by saying that it has a cause, 
 and that this cause is another alteration. Here we have the 
 axiom of causalty ; considered with reference to the axiom 
 of explanatory reason, it is a consequence and an application 
 of that axiom. That axiom has many others. Leibnitz, 
 who termed it Principle of Sufficient Reason, constructed 
 33
 
 514 THE KNOWLEDGE OF GENERAL THINGS. [BOOK IV. 
 
 from it all his idea of the universe. And, in fact, it is by 
 this axiom that we arrive at the highest conception of a 
 general aggregate, at the idea of one necessary whole, at the 
 persuasion that existence is itself explainable. For, since 
 existence is a general character, and the most general of all 
 characters, we must conclude from our axiom that it has, like 
 every general character, its condition or explanatory reason, 
 other than itself. Mathematicians assume nowadays that 
 real quantity is only a case of imaginary quantity, a special 
 and singular case, in which the elements of imaginary quantity 
 present certain conditions which are wanting in the other 
 cases. May we not similarly assume that real existence is 
 only a case of possible existence, a special and singular case, 
 in which the elements of possible existence present certain 
 conditions which are wanting in the other cases ? With this 
 assumption, may we not inquire into these elements and these 
 conditions ? We are here on the threshold of metaphysics. 
 
 We will not enter ; we are here concerned with cognitions 
 alone. The reader has seen how they are formed, and by 
 what adjustments they correspond to things. They have, as 
 materials, sensations of various kinds, some primitive and 
 excited, others spontaneous and reviving, attached to one 
 another, counterbalanced by one another, purposely organized 
 by their connections and their antagonism, composed of ele- 
 mentary sensations smaller than themselves, these again of 
 still smaller ones, and so on, till their differences are finally 
 effaced and permit us to divine the existence of wholly similar 
 infinitesimal elements whose various arrangements explain 
 their various aspects. Thus in a cathedral, the ultimate 
 elements are grains of sand agglutinated into stones of various 
 forms, which, attached in pairs, form masses, whose thrusts 
 oppose and balance each other ; all these associations and all 
 these mutual pressures being co-ordinated in one grand har- 
 mony. Such is the simplicity of the means, and such the 
 complication of the effect, and both the simplicity and the 
 complication are as admirable in the mental as in the real 
 edifice. 
 
 THE END.
 
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