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 UNIVERSITY 
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I N Q^U I R y\ 
 
 INTO THE 
 
 HUMAN MIND, 
 
 On the Principles of 
 
 COMMON SENSE. 
 
 By THOMAS REID, D. D; 
 
 Profeffor of Moral Philofophy in the Univerfity 
 of Glasgow. 
 
 The infpiration of the Almighty gi-veth them under/landing, 
 
 Job« 
 
 The THIRD EDITION Correfted. 
 
 LONDON: 
 
 Printed for T. Cadell, (Succeflbr to A. Millar} in the 
 
 Strand, and T. Longman, in Pater-Nofter Row, London ; 
 
 and A. Kincaid and J. Bell, Edinburgh. 
 
 MDCCLXIX. 
 
T O 
 THE RIGHT HONOURABLE 
 
 JAMES Earl of FINDL ATER 
 and SEAFIELD, 
 
 Chancellor of the Univerfity of 
 OLD ABERDEEN. 
 
 ,. My LoRi), 
 
 fTp hough I apprehend that there are 
 -*■ things new, and of fome import- 
 ance, in the following inquiry* it is 
 not without timidity that I have con- 
 fented to the publication of it. The 
 fubjeet has been canvafied by men of 
 very great penetration and genius : for 
 who does not acknowledge Des Cartes, 
 Malebranche, Locke, Berkeley, and 
 Hume, to be fuch? A view of the hu- 
 man underftanding fo different from 
 that which they have exhibited* will, 
 no doubt, be condemned by many 
 a 2 without 
 
fv DEDICATION. 
 
 without examination, as proceeding 
 from temerity and vanity. 
 
 But I hope the candid and difcern- 
 ing Few, who are capable of attend- 
 ing to the operations of their own 
 minds, will weigh deliberately what 
 is here advanced, before they pafs fen- 
 tence upon it. To fuch I appeal, as 
 the only competent judges. If theydif- 
 approve, I am probably in the wrong, 
 and fhall be ready to change my opi- 
 nion upon conviction. If they approve, 
 the Many will at lafl yield to their au- 
 thority, as they always do. 
 
 However contrary my notions are 
 to thofe of the writers I have mention- 
 ed, their fpeculations have been of 
 great ufe to me, and feem even to 
 point out the road which I have taken j 
 and your Lordfhip knows, that the me- 
 rit of ufeful difcoveries is fometimes 
 not more juftly due to thofe that have 
 hit upon them, than to others, who 
 
DEDICATION. v 
 
 have ripened them, and brought them 
 to the birth. 
 
 I acknowledge, my Lord, that I 
 never thought of calling in queftion 
 the principles commonly received with 
 regard to the human underftanding, 
 until the Treatife of human nature was 
 publifhed, in the year 1 739. The inge- 
 nious author of that treatife, upon the 
 principles of Locke, who was no fceptic, 
 hath built a fyftem of fcepticifm, which 
 leaves no ground to believe any one 
 thing rather than its contrary. His 
 reafoning appeared to me to be juft: 
 there was therefore a neceffity to call 
 in queftion the principles upon which 
 it was founded, or to admit the con- 
 clufion. 
 
 But can any ingenious mind admit 
 this fceptical fyftem without reluct- 
 ance ? I truly could not, my Lord : for 
 I am perfuaded,., that abfolute fcepti- 
 cifm is not more deftructive of the 
 a 3 faith 
 
vi DEDICATION. 
 
 faith of a Chriftian, than of the fci- 
 ence of a philofopher, and of the pru- 
 dence of a man of common under- 
 ftanding. I am perfuaded, that the 
 unjuft live by faith as well as the jujl ; 
 that, if all belief could be laid alide, 
 piety, patriotifm, friendfhip, paren- 
 tal affection, and private virtue, 
 would appear as ridiculous as knight- 
 errantry ; and that the purfuits of 
 pleafure, of ambition, and of avarice, 
 mufl: be grounded upon belief, as well 
 as thofe.that are honourable and vir- 
 tuous. 
 
 The day-labourer toils at his work, 
 in the belief that he mall receive his 
 wages at night; and if he had not 
 this belief, he would 'not toil. We 
 may venture to fay, that even the au- 
 thor of this fceptical fyftem, wrote it 
 in the belief that it fhould be read and 
 regarded. I hope he wrote it in the 
 belief alfo, that it would be ufeful to 
 mankind : and perhaps it may prove 
 
 fo 
 
DEDICATION. vii 
 
 fb at laft. For I conceive the fceptical 
 writers to be a fet of men, whofe bu- 
 finefs it is, to pick holes in the fabric 
 of knowledge wherever it is weak and 
 faulty ; and when thefe places are 
 properly repaired, the whole building 
 becomes more firm and folid than it 
 was formerly. 
 
 Tor my own fatisf action, I entered 
 Into a ferious examination of the prin- 
 ciples upon which this fceptical fyf- 
 tem is built ; and was not a little fur- 
 prifed to find, that it leans with its 
 whole weight upon a hypothefis, 
 which is ancient indeed, and hath 
 been. very generally received by phi- 
 lofophers, but of which I could find 
 no folid proof. The hypothefis I mean 
 is, That nothing is perceived but what 
 is in the mind which perceives it: 
 That we do not really perceive things 
 that are external, but only certain 
 images and pictures of them imprint- 
 a 4 - ed 
 
viii DEDICATION. 
 
 «► 
 
 ed upon the mind, which are called 
 
 imprejjions and ideas. 
 
 If this be true; fuppofing certain 
 impreflions and ideas to exift in my 
 mind, I cannot, from their exiftence, 
 infer the exiftence of any thing elfe ; 
 my impreflions and ideas are the only 
 exiftence s of which I can have any 
 knowledge or conception: and they 
 are fuch fleeting and transitory beings, 
 that they can have no exiftence at all, 
 any longer than I am confcious of 
 them. So that, upon this hypothefis, 
 the whole univerfe about me, bodies 
 and fpirits, fun, moon, ftars, and 
 earth, friends and relations, all things 
 without exception, which I imagined 
 to have a permanent exiftence, 
 whether I thought of them or not, 
 vanifh at once ; 
 
 And like the bafelefs jabric of a vi/tQti, 
 Leave not a tra5l hehind % 
 
 X 
 
DEDICATION. ix 
 
 I thought it unreafonable, my 
 Lord, upon the authority of philofo- 
 phers, to admit a hypothecs, which, 
 in my opinion, overturns all philoso- 
 phy, . all religion and, virtue, and all 
 common fenfe: and finding that all 
 the fyftems concerning the human 
 understanding which I was acquaint- 
 ed with, were built upon this hypo- 
 thefis, I refolved to inquire into this 
 fubjedt. anew, without regard- to any 
 hypothefis. 
 
 What I now humbly prefent to 
 your Lordfhip, is the fruit of this in- 
 quiry, fo far only as it regards the five 
 fenfes. In which I claim no other me- 
 rit, than that of having given great 
 attention to the operations of my own 
 mind, and of having expreffed, with 
 all the perfpicuity I was able, what I 
 conceive, every man who gives the 
 fame attention, will feel and perceive. 
 The productions of imagination, re- 
 quire a genius which foars above the 
 
 common 
 
x DEDICATION. 
 
 common rank j but the treafures of 
 knowledge are commonly buried 
 'deep, and may be reached by thofe 
 drudges who can dig with labour and 
 patience, tho' they have not wings to 
 fly. The experiments that were to be 
 made in this inveftigation fuited me, 
 as they required no other expence, but 
 that of time and attention, which I 
 could bellow. The leifure of an aca- 
 demical life, difengaged from the 
 purfuits of interefl and ambition ; the 
 
 duty of my profeffion, which obliged 
 me to give prelections on thefe fubjects 
 to the youth ; and an early inclination" 
 to fpeculations of this kind, have en- 
 abled me, as I flatter myfelf, to give 
 a more minute attention to the fub- 
 jecT: of this inquiry, than has been 
 given before. 
 
 My thoughts upon this fubjedl were, 
 a good many years ago, put together 
 in another form, for the ufe of my 
 pupils ; and afterwards were fubmitted 
 
 to 
 
DEDICATION. xi 
 
 to the judgment of a private philofo- 
 phical fociety, of which I have the 
 honour to be a member. A great part 
 of this inquiry was honoured even by 
 your Lordfliip's perufal. And the en- 
 couragement which you, my Lord, 
 and others, whofe friendfhip is my 
 boaft, and whofe judgment I reve- 
 rence, were pleafed to give me, coun- 
 terbalanced my timidity and diffi- 
 dence, and determined me to offer it 
 to the public. 
 
 If it appears to your Lordfhip to ju- 
 itify the common fenfe and reafon of 
 mankind, againft the fceptical fubtil- 
 ties which, in this age, have endea- 
 voured to put them out of counte- 
 nance ; if it appears to throw, any new 
 light upon one of the noblefl parts of 
 the divine workmanfhip ; your Lord- 
 fliip's refpect for the arts and fciences, 
 and your attention to every thing 
 which tends to the improvement of 
 them, as well as to every thing elfe 
 
 that 
 
xii D..E D I C A T I O N. 
 
 that contributes to the felicity of your 
 c mutry, leave aie no room to doubt 
 of your favourable acceptance of this 
 efTav, as the fruit of my induftry in a 
 pr oreffion wherein I was accountable 
 to your Lordlhip; and as a teftimony 
 of the gr.-at efteem and refpecl: where- 
 with I have the honour to be, 
 
 My Lord, 
 
 Your Lordship's 
 
 mod obliged, and 
 
 moft devoted fervant, 
 
 THO. REID. 
 
CONTENTS. 
 
 CHAPTER I. 
 INTRODUCTION. 
 
 Sett. Page 
 
 1. The importance of the fubjeft, and the 
 means of profecuting it,. i 
 
 2. The .impediments to .our knowledge of the 
 
 mind, 4 
 
 3. The prefent Jlate of this part of philofo- 
 
 phy. Of Des Cartes, Malebranche, and 
 Locke, 10 
 
 4. Apology for thofe philofophers, - 14 
 
 5. Of Bifhop Berkeley ; the Treatife of human 
 nature ; and .of fcepticifm, - - 16 
 
 6. Of the Treatife of human nature, - 20 
 
 7. T^tf j/y/«» of all thefe authors is the fame, 
 
 and leads to fcepticifm, - - 22 
 
 8. We ought not to dtfpair of a better, - 23 
 
 CHAP. II. 
 
 Of SMELLING. 
 
 Sed. 
 
 1 . The order of proceeding. Of- the medium 
 
 and organ of fmell, - - 26 
 
 2. Thefenfationconjideredabflraclly, - 28 
 
 3. Senfation and remembrance, natural princi- 
 
 ples of belief - - -30 
 
 4. Judgment and belief- in fame cafes precede 
 
 Jimple apprehenjion, - - 34 
 
 6 5. Two 
 
xiv CONTENTS. 
 
 Soft. Page 
 
 5. Two theories of the nature of belief refuted. 
 
 Conclufions from what hath been f aid, 35 
 
 6. Apology for metaphyjical abfurdities. Senfa- 
 
 tion without a fentient, a confequence of 
 the theory of ideas. Conferences of this 
 firange opinion, - - 39 
 
 7. The conception and belief of a fentient being 
 
 or mind, is fuggejled by our confiitution. 
 The notion of relations not always got by 
 comparing the related ideas, - 47 
 
 8. There is a quality or virtue in bodies, which 
 
 we call their fmell. How this is connecled 
 in the imagination with the fenfation, 5 1 
 
 g. That there is a principle in human nature, 
 from which the notion of this, as well as 
 of all other natural virtues or caufes, is de- 
 rived, - - 54 
 
 10. Whether in fenfation the mind is aElive or 
 fajjive? - - - 6» 
 
 CHAP. Ill, 
 Of TASTING, - z 6$ 
 
 CHAP. IV. 
 Of HEARING. 
 
 Sefo 
 
 1 . Variety of founds. Their place and diftance 
 
 learned by cuftom, without reafoning, 65? 
 
 2. Of natural language, - - 72 
 
 3 CHAP. 
 
CONTENTS. xv 
 
 CHAP. V. 
 
 Of T O U C H. 
 
 Seft. Page 
 
 i. Of heat and cold, - ; - 78 
 
 2. Of hardnefs and foftnefs, » - 81 
 
 3. Of natural figns, - - 87 
 
 4. Of hardnefs, and other primary qualities, 92 
 
 5. Of extenfion, - - - 94 
 
 6. Of extenfion, - - - 99 
 
 7. Of the exiftence of a material world, 102 
 
 8. Of the Jyftems of philofophers concerning the 
 
 fenfes, z - - 113 
 
 CHAP. VI: 
 Of SEEING. 
 
 Sea. 
 
 1. The excellence and dignity of this fa- 
 
 culty, - - - - 120 
 
 2. Sight difcovers almoft nothing which the 
 
 blind may not comprehend. The reafon 
 
 of this, . - - 123 
 
 3. Of the vifible appearances of objecls, 130 
 
 4. That colour is a quality of bodies, not a 
 
 fenfation of the mind, - - 135 
 
 5. An inference from the preceding, - 139 
 
 6. That none of our fenfations are refem- 
 
 hlances of any of the qualities of bodies, 1 45 
 
 7. Of vifible figure and extenfion, - 153 
 
 8. Some queries concerning vifible figure an- 
 
 fwered, - - - 159 
 
 9. Of the geometry of vifibks t - 168 
 
 10. Of 
 
xvi Contents. 
 
 Se£t. Page 
 
 10. Of the parallel motion of the eyes, 1 85 
 
 11. Of our feeing objects eretl by inverted 
 
 images, - - » 190 
 
 iz. The fame fubjeSl continued, 199 
 
 13. Of feeing- objeSis fingle with two eyes, 222 
 H4. Of the laws of vifion in brute animals^ 233 
 15 Squinting confidered hypothetical^, 237 
 
 16. Fails relating to fquinting, 253 
 
 17. Of 4 he effeil-of cuftom in feeing objeSfs 
 Jingle, - 258 
 
 18. Of Dr Porterfield's account of Jingle 
 
 ■timd double <vifim, - - 268 
 
 19,- Of Dr. Briggs's theory, and of Sir Ifaac 
 
 Newton's conjetJure on this fubjetl, 273 
 
 10. Of perception in general, - 288 
 
 2 1 . Of the prccefs of nature in perception, 301 
 
 22. Of the figns by which we learn to per- 
 
 ceive diftance from the eye, 309 
 
 23. Of the figns ujed in other acquired per- 
 
 ceptions, - - 326 
 
 24. Of the analogy between perception, and 
 
 the credit we give to human teftimony t 330 
 
 CHAP. VII. 
 
 CONCLUSION. 
 
 Containing, Reflections upon the opinions 
 of Philosophers on this fubjedt* - 355 
 
INQUIRY' 
 
 INTO THE 
 
 HUMAN'MIND. 
 
 CHAP. I. 
 
 INTRODUCTION. 
 
 SECT. I. 
 
 The importance of the fubjeffj and the means of 
 ■profecuting it. 
 
 TH E fabric of the human mind is curi- 
 ous and wonderful, as well as that of 
 the human body. ' .The faculties of the 
 One are with no lefs Wifdom adapted to their fe- 
 veral ends, than the organs of the other. Nay, 
 it is reafonable to think, that as the mind is a 
 nobler work, and of a higher order than the 
 body, eveji more of the wifdom and fkill of 
 the divine architect hath been employed in its 
 ftruclure. It is therefore a fubjec\ highly 
 
 A worthy 
 
2 Of the HUMAN MIND. Chap. I. 
 worthy of inquiry on its own account, but ftill 
 more worthy on account of the extehfive influ- 
 ence which the knowledge of it hath over every 
 Other branch of fcience. 
 
 In the arts and fciences which have leaft con- 
 nexion with the mind, its faculties are the en- 
 gines which we muft employ j and the better we 
 underftand their nature and ufe, their defects and 
 diforders, the more fkilfully we mail apply them, 
 and with the greater fuccefs. But in the nobleft 
 arts, the mind is alfo the fubjett upon which we 
 operate. The painter, the poet, the a&o'r, the 
 orator, the moralift, and the ftatefman, attempt 
 to operate upon the mind in different ways, and 
 for different ends ; and they fucceed, according 
 as they touch properly the firings of the human 
 frame. Nor can their feveral arts ever ftand on 
 a folid foundation, or rife to the dignity of fci- 
 ence, until they are built on the principles of the 
 human eonflitution. 
 
 Wife men now agree, or ought to agree in 
 this, that there is but one way to the knowledge 
 of nature's works 5 the way of obfervatiOn and 
 experiment. By our eonftitution, we have a 
 ftrong propensity to trace particular fafts and ob- 
 fervations to general rules, and to apply fuch ge- 
 neral rules to account for other effedls, or to dr- 
 re£t us in the production of them. This proce- 
 dure of the underftandingjs familiar to every hu- 
 man creature in the common affairs of life, and 
 it is the only one by which any real di&overy 
 in philofbphy can be made. 
 
 The 
 
Seft. i. INTRODUCTION. $ 
 
 The man who firft difcovered that cold free- 
 zes water, and that heat turns it into vapour* 
 proceeded on the fame general principles, and in 
 the fame method, by which Newton difcovered 
 the law of gravitation, and the properties of light* 
 His reguld • philpfopbdndi are maxims of common, 
 fenfe, and are prattifed every day in common 
 life; and he who philofophjzes by other rules, 
 either concerning the material fyftem, of con- 
 cerning the mind, miftakes his aim. 
 
 Conjectures and theories are the creatures of 
 men, and will always be found very unlike the 
 creatures of God. If we would know the works 
 of God, we muft confult themfelves with atten- 
 tion and humility, without daring to add any 
 thing of ours to what they declare. A juft in- 
 terpretation of nature is the Only found and or- 
 thodox philofophy : Whatever we add of out 
 own, is apocryphalj and of no authority. 
 
 All our curious theories of the formation of 
 the earth, of the generation of animals, of the 
 origin of natural and moral evil, fo far as they go 
 beyond a juft induction from fads, are vanity 
 and folly, no lefs than the vortices of Des Cartes* 
 or the Archseus of Paracelfus. Perhaps the phi- 
 lofophy of the mind hath been no lefs adultera- 
 ted by theories, than that of the material fyfterri* 
 The theory of ideas is indeed very ancient, and 
 hath been very univerfally received j but as nei-» 
 ther of thefe titles can give it authenticity, they 
 ought not to fcreen it from a free and candid 
 examination -, efpecially in this age, when it hath 
 A a pro* 
 
4 OftheHUM AN MIND. Chap. L 
 produced a fyftem of fcepticifm, that feems to 
 triumph over all fcience, and even over the dic- 
 tates of common fenfe. 
 
 All that we- know of the body, is owing to 
 anatomical difledlionand obfervation, and it mult 
 be by an anatomy of the mind that we can dis- 
 cover its powers and principles. 
 
 SECT.. II. 
 
 'the impediments to our knowledge of the mind. 
 
 T> UT it muft be acknowledged, that, this 
 kind of anatomy is much more difficult 
 than the other ; and therefore it needs not feem 
 ftrange, that mankind have made lefs progrefs in 
 it. To attend accurately to the operations of 
 our minds, and make them an object of thought, 
 is no eafy matter even to the contemplative, and 
 to the bulk of mankind is next to impoffible. 
 
 An anatomift who h3th happy opportunities, 
 may have accefs to examine with his own eyes, 
 and with equal accuracy, bodies of all different 
 ages, fexes, and conditions ; fa that what is de-r 
 fedlive, obfcure, or preternatural in one, may be 
 difcerned clearly, and in its moft perfedl ftate in 
 another. But the anatomift of the mind cannot 
 have the fame advantage. It is his own mind 
 only that he can examine, with any degree of 
 accuracy and diftin&nefs. This is the only fub- 
 jecl: he can look into. He may, from outward 
 figns, collecT: the operations of other minds ; but 
 2 thefe 
 
Seft. 2. INTRODUCTION. 5 
 
 thefe figns are for the moft part ambiguous, and 
 muft be interpreted by what he perceives within 
 himfelf. 
 
 So that if a philofopher could delineate to us, 
 diftinftly and methodically, all the operations of 
 the thinking principle within him, which no man 
 was ever able to do, this would be only the ana- 
 tomy of one particular fubjecl:; which would be 
 both deficient and erroneous, if applied to human 
 nature in general. For a little- reflection may 
 fatisfy us, that the difference of minds is greater 
 than that of any other beings, which we confider 
 as of the fame fpecies. 
 
 Of the various powers and. faculties we pof- 
 fefs, there are fome which nature feems both to - 
 have planted and reared, fo as to have left no- 
 thing to human induftry. Such are the powers 
 which we have in common with the brutes, and 
 which are neceflary to the prefervation of the in- 
 dividual, or the continuance of the kind. There 
 are other powers, of which nature hath only 
 planted the feeds in our minds, but hath left the 
 rearing of them to human culture. It is by the 
 proper culture of thefe that we are capable of all 
 thofe improvements in intellectuals, in tafte, and 
 in morals, which exalt and dignify human na- 
 ture -, while, on the other hand, the neglect or 
 perverfion of them makes its degeneracy and 
 corruption. 
 
 The two-legged animal that eats of nature's 
 
 dainties what his tafte or appetite craves, and fa- 
 
 tisfies his thirft at the cryftal fountain, who pror 
 
 A 3 pagates 
 
6 OftheHUMAN MIND. Chap, I, 
 
 pagates his kind as occafion and, lqft prompt, re* 
 pels injuries, and takes alternate labour and re- 
 pofe, is, like a tree in the foreft, purely of na^ 
 ture's growth. But this fame favage hath with^ 
 in him the feeds of the logician, the man of tafte 
 and breeding, the orator, the ftatefman, the man 
 of virtue, and the faint, ; which feeds, though 
 planted in his mind by nature, yet, through want 
 of culture and exercife, muft lie for ever buried, 
 and be hardly perceivable by himfelf or by 
 others, 
 
 The loweft degree of focial life will bring to 
 Jight fome of thofe principles which lay hid in 
 the favage ftate ; and according to his training, 
 9nd company, and manner of life, fome of them, 
 either by their native vigour, or by the force of 
 culture, will thrive and grow up to great perfect 
 tion, pthers will be ftrangely perverted from 
 their natural form, and others checked, or per- 
 haps quite eradicated. ■$£ „ 
 
 This makes human nature fo various and mul-r 
 tiform in the individuals that partakea)f it, that, 
 in point of morals, and intellectual endowments, 
 it fills up all that gap which we conceive to be 
 between brutes and devils belqw, and the eelef- 
 tial orders above ; and fuch a prodigious diver^ 
 fity of minds muft make it extremely difficult to 
 djfcover the common principles of the fpecies. 
 
 The language of philofqphers, with regard to 
 the original faculties of the mind, is fo adapted 
 to the prevailing^ fyftem, that k cannot fit any 
 Other $ Jjk? a. coat that fits the. maji for whom it 
 
 was 
 
Scft. a. INTRODUCTION. 7 
 
 was made, and fhows Him to advantage, which 
 yet will fit very aukward upon one of a different 
 make, although perhaps as handfome and as well 
 proportioned. It is hardly poflible to make any 
 innovation in our philofophy concerning the mind 
 and its operations, without ufing new words and 
 phrafes, or giving a different meaning to thofe 
 that are received ; a liberty which, even when 
 neceffary, creates prejudice and mifconftru&ion, 
 and which muft wait the fancldon of time to au- 
 thorife- it. For innovations in, language, like 
 thofe in religion and 'government, are always 
 fufpe&ed and diffiked by the many, till ufe hath 
 made them familiar, and prefcription hath given 
 them a title. 
 
 If the original perceptions and notions of the 
 mind were to make their appearance fingle and 
 unmixed, as we fifft received them from the hand 
 of nature, one accuftomed to reflection would 
 have lefs difficulty in tracing them ; but before 
 we are capable of reflection, they are fo mixed, 
 compounded, and decompounded, by habits, af- 
 fociations, and abftraclions, that it is hard to 
 know what they were originally. The mind 
 may in this refpeft be compared to an apothecary 
 or a chymift, whofe materials indeed are furnifli- 
 ed by nature ; but for the purpofes of his art, 
 he mixes, compounds, difiblves, evaporates, and 
 fublimes them, till they put on a quite different 
 appearance i fo that it is very difficult to know 
 what they were at firft, and much more to bring 
 them back to their original and natural form, 
 A 4 And 
 
8 Of -the H U M A N M I N D. ' Chap. I, 
 
 And this work of the mind is not carried on by 
 deliberate acts of mature reafon, which we might 
 recoiled, but bymeansof inftincts, habits, affocia- 
 tions, andother principles, which operate before we 
 come to the ufe of reafon •, fo that it is extremely 
 difficult for the mind to return upon its own foot- 
 fteps, and trace back thofe operations which have 
 employed it fince it firft began to think and to aft. 
 . Could we obtain a diftinct and full hiftory of 
 all that hath paffed in the mind of a child, from 
 the beginning of life and fenfation, till it grows 
 up to the ufe of reafori'; how its infant faculties 
 began to work,: and-hew they brought forth and 
 ripened all. the various notions, opinions* and fen- 
 timents, which we find in ourfelves' when we 
 come to be capable of reflection \ this would be a 
 treafure of natural hiftory, which would probably 
 give more light. into- the human faculties, than 
 all the fyftems of philolbphers about them fince 
 the beginning of the world. But it is in vain 
 to wifh for what nature has not put within the 
 reach of our power. Reflection, the only inftru- 
 ment by -which we can difcern the powers of 
 the mind,; comes too late to obferve the progrefs 
 of nature, in raifing them from their infancy to 
 
 perfection. 
 
 It mufL therefore require great caution, and 
 .greats application of mind, for a man that is 
 grown up in all the prejudices of education, fa- 
 ihion, and philofophy, to unravel his notions and 
 ppinions, till he finds out the fimple and original 
 principles of his conftitution, of which no ac r 
 
 count 
 
Seft. 2. INTRODUCTION. 9 
 
 count can be given but the will of our Maker. 
 This may be truly called an analyfis of the hu^ 
 man faculties ; and till this is performed, it is in 
 vain we expeel: any juft jyftem of the mind -, that 
 is, an enumeration of the original powers and 
 laws of our conftitution, and an explication from 
 them of the various pb'asnomena of human na- 
 ture. 
 
 Suceefs, in an inquiry of this kind, it is not in 
 human power to' command ; but perhaps' it is 
 poffible, by caution and humility, to avoid error 
 and delufion. The labyrinth may be too intri- 
 cate, and the , thread too fine, to be traced thro' 
 all its windings ; but if we ftop where we can 
 trace it no farther', and fecUre. the ground we 
 have gained, there is no harm done; a quicker 
 eye may in time trace it farther. 
 
 It is genius, and not the want of it, that adul- 
 terates philofophy, and fills it with error and 
 falfe theory."' A creative imagination difdains 
 the mean "offices of digging for a foundation, of 
 removing rubbifh, and carrying materials : lea- 
 ving thefe feryile employments to the drudges, in 
 fcience, it 1 plans a defign, and raifes a fabric. In- 
 vention fupplies materials- where they are want- 
 ing, and fancy adds colouring, and every befit- 
 ting ornament. The work pleafes the eye, and 
 wants nothing but folid'ity'artd a good founda- 
 tion. It feems even to vye with the works of 
 nature, till fome fucceeding architect blows it 
 into rubbifh, and builds as goodly a fabric of 
 his own in its place. Happily for the prefent 
 
 age, 
 
IO OftheHUMAN MIND. Chap. L 
 age, the caftle-builders employ themfelves more 
 in romance than in philofophy. That is un- 
 doubtedly their province, and in thofe regions 
 the offspring of fancy is legitimate, but in phU 
 lofophy it is all fpurjoys. 
 
 SECT. Ill, 
 
 *f. he prefent ft ale of this part of philofophy. Of 
 Des Cartes, Malefranche, and Lpcke, 
 
 r T i H A T our philofophy concerning the mind 
 and its faculties, is but in a very low ftate, 
 may be reafonably conjectured, even by thofe 
 who never have narrowly examined it. Are 
 there any principles with regard to the mind, 
 fettled with that perfpicuity. and evidence, which 
 attends the principles 'of mechanics, aftronomy, 
 and optics ? Thefe are really fciences, built up- 
 on laws of nature which univerfally obtain, 
 "What is difcovered in them, is no longer matter 
 of difpute : future ages may add to it, but till 
 the CQurfe of nature be changed, what is already 
 eftablifhed can never be overturned. But when 
 we turn our attention inward, and confider the 
 phenomena of human thoughts, opinions, and 
 perceptions, and endeavour to trace them to the 
 general laws and the firft principles- of our con- 
 stitution, we are immediately involved in darl$- 
 nefs and perplexity. And if common fenfe, or the 
 principles of education, happen not to be flub- 
 born, it is odds but we end in abfolute fcepticifm, 
 
 Des 
 
Beft. S , INTRODUCTION. u 
 
 Des Cartes finding nothing eftablifhed in this 
 part of philofophy, in order to lay the founda- 
 tion of it deep, refolved not to believe his own 
 exiftence till he fhould be able to give a good 
 reafon for it. He was, perhaps, the firft that 
 took up fuch a reiblution : but if he could indeed 
 have effected his purpofe, and really become dif- 
 fident of his exiftence, his cafe would have been 
 deplorable, and without any remedy from reafon, 
 or philofophy, A man that difbelieves his own 
 exiftence, is furely as unfit to be reafoned with, 
 as a man that believes he is made of glafs. There 
 may be diforders in the human frame that may 
 produce fuch extravagancies, but they will never 
 be cured by reafon ing. Des Cartes indeed would 
 make us believe, that he got out of this delirium 
 by this logical argument, Cegito, ergo /urn. But 
 it is evident he was in his fenfes all the time, and 
 neVer ferioufly doubted of his exiftence. For he 
 takes it for granted in this argument, and proves 
 nothing at all. I am thinking, fays he, therefore 
 I am : and is it not as good reafoning to fay, I 
 am deeping, therefore I am ? or, I am doing no- 
 thing, therefore 1 am ? If a body moves, it muft 
 exift, no doubt ; but if it is at reft, % it muft exift 
 likeways. 
 
 Perhaps Des Cartes meant not to afTume his 
 own exiftence in this enthymeme, but the exi- 
 ftence of thought ; and to infer from that the 
 exiftence of a mind, or fubjeft of thought. But 
 why did he not prove the exiftence of his 
 thought ? Confcioufnefs, \ t m? y b e faid, vouches 
 
 that. 
 
12 Of the HUMAN MIND. Chap. I. 
 that. But who is voucher for confcioufnefs ? 
 Can any man prove that his confcioufnefs may not 
 deceive him ? No man can : nor can we give a 
 better reafon for trufting to it, than that every 
 man, while his mind is found, is determined, 
 by the conftitution of his nature, to give impli- 
 cit belief to it, and to laugh at, or pity the man 
 who doubts its teftimony. And is not every 
 man, in his wits, as much determined to take his- 
 exiftence upon truft as his confcioufnefs ? 
 
 The other proportion affumed in' this argu- 
 ment, That thought cannot be without a mind or 
 fubjecl, is liable to the fame objection : not that 
 it wants evidence; but that its evidence is no 
 clearer, nor more immediate, than that of the 
 propofition to be proved by it. And taking all 
 thefe propoficions together, — I think, — I am 
 confcious,' — Every thing that thinks, exifts, — 
 I exift, — would not every fober man form the 
 fame opinion of the man who ferioufly doubted 
 any one of them ? And if he was his frierld, would 
 he not hope for his cure from phyfic and good 
 regimen, rather than from metaphyfic and logic ? 
 
 But fuppofing it proved, that my thought and 
 my confcioufnefs muft have a fubjecl, and confe- 
 quently that I exift, how do I know that all that 
 train and ^ucceflion of thoughts which I remem- 
 ber, belong to one fubjecl, and that the I of this 
 moment, is the very individual I of yefterday, 
 and of times paft ? 
 
 Des Cartes did not think proper to ftart this 
 doubt : but Locke has done it ; and, in order 
 
 to 
 
Sea. 3. INTRODUCTION. 13 
 
 to refolve it, gravely determines, that perfqnal 
 identity confifts in confcioufnefs ; that is, if you 
 are confcious. that you did fuch a thing a twelve- 
 month ago, this confcioufnefs makes you to be 
 the very perfon that did it. Now, confcioufnefs 
 of what is paft, can fignify nothing elfe but the 
 remembrance that I did it. So that Locke's 
 principle rnuft be, That identity confifts in re- 
 membrance ; and confequently a man muft lofe 
 his perfonal. identity with regard to every thing 
 he forgets. 
 
 Nor are thefe the'only instances whereby our 
 philofophy concerning the mind appears to be 
 very fruitful in creating doubts, but very un- 
 happy in refolving them. 
 
 Des Cartes, Malebranche, and Locke, have all 
 employed their genius and (kill, to prove the 
 exiftence of a material world ; and with very 
 bad fuccefs. Poor untaught mortals believe un- 
 doubtedly, that there is a fun, moon, and ftars ; 
 an earth, which we inhabit ; country, friends, 
 and relations, which we enjoy ; land, houfes, and 
 moveables, which we pofiefs. But philofophers, 
 pitying the^ credulity of the vulgar, refolve to 
 have no faith but what is founded upon reafon. 
 They apply to philofophy to furnifh them .with 
 reafons for the belief of thofe things which all 
 mankind have believed, without being able to 
 give any reafon for it. And fureiy.one would 
 expeft, that, in matters of fuch importance, the 
 proof would not be difficult : but it is the molt 
 difficult thing in the world. For thefe three 
 
 great 
 
*4 Ofthe HUMAN MlND. Chap. I 
 great frien, with the beft good will, #have not 
 been able$ from all the treafures of philofophy, 
 to draw one argument, that is fit to convince a 
 man that can reafon* of the exiftence of any one 
 thing without him. Admired Philofophy ( 
 daughter of light ! parent of wifdom and know- 
 ledge ! if thou art fhe ! furely thou haft not yet 
 arifen upon the human mind, nor blefled us with 
 more of thy rays* than are fufficient to fhed a 
 darknefs vifible upon the human faculties, and to 
 difturb that repofe and fecurity which happief 
 mortals enjoy, who never approached thine al- 
 tar, nor felt thine influence ! But if indeed thou 
 haft not power to difpel thofe clouds and phan-> 
 toms which thou haft difcovered or created* 
 withdraw this penurious arid malignant ray { I 
 defpife Philofophy, and fenounce its guidance; 
 let my foul dwell with Common Senfe. 
 
 SECT. IV. 
 
 Apology for thofe philosopher U 
 
 t? U T inftead of defpifing the dawn of right* 
 we ought rather to hope for its increafe i 
 Inftead of blaming the philofophefs I have men- 
 tioned, for the defedts and blemifhes of their 
 fyfterrij we ought rather to honour their me- 
 mories, as the firft difcoverefs of a region in phi- 
 lofophy formerly unknown ; and however lame 
 and imperfect the fyftem may be, they have 
 opened the way to future difcoveries, and are 
 
 juftly 
 
&& 4 . INTRO DtJCTIOK. i$ 
 
 juftly intitled to a great mare in the merit of 
 them. They have removed an infinite deal of 
 duft and rubbifli, collected in the ages of fcho- 
 laftic fophiftry, which had obftructed the way. 
 They have put us in the right road, that of ex- 
 perience and accurate reflection. They have 
 taught us to avoid the fnares of ambiguous and 
 ill-defined words, and have fpoken and thought 
 upon this fubject with a diftinctnefs and perfpi* 
 cuity formerly unknown. They have made 
 many openings that may lead to the difcovery 
 of truths which they did not reach, or to the de- 
 tection of errors in which they were involun- 
 tarily intangled. 
 
 It may be obferved, that the defe&s and ble- 
 milhes in the received philofophy concerning the 
 mind, which have moll expofed it to the con- 
 tempt and ridicule of fenfible men, have chiefly 
 been owing to this : That the votaries of this 
 Philofophy, from a natural prejudice in her fa- 
 vour, have endeavoured to extend her jurifdic- 
 tion beyond its juft limits, and to call to her bar 
 the dictates of Common Senfe. But thefe de- 
 cline this jurifdictibn ; they difdain the trial of 
 reafoning, and difown its authority; they nei- 
 ther claim its aid, nor dread its attacks. 
 
 In this unequal conteft betwixt Common 
 Senfe and Philofophy, the latter will always 
 come off both with dilhonour and lofs ; nor cart 
 me ever thrive till this rivalfhip is dropt, thefe 
 incroachmertts given up, and a cordial friendftiip 
 reftored : for, in reality, Common Senfe holds 
 f nothing 
 
i6 Of the HI/MAN MIND. Chap. L 
 nothing of Philofophy, nor needs her aid. But, 
 on the other hand, Philosophy (if I may be per- 
 mitted to change the metaphor) has no other 
 root but the principles of Common Senfe; it 
 grows out of them, and draws its nourimment 
 from them : fevered from this root, its honours 
 wither, its fap is dried up, it dies and rots. 
 
 The philofophers of the laft age, whom I have 
 mentioned, did not attend to the preferving t-hi® 
 union and fubordination fo carefully as the hoi- 
 nour and intereft of philofophy required : but 
 thofe of the'prefent have waged open war with 
 Common Senfe, and hope to make a complete 
 conqueft of it by the fubtilties of Philofophy s 
 an attempt no lefs audacious and vain, than that 
 of the giants to dethrone almighty Jove. 
 
 S E C T. V. 
 
 Of Bijhop Berkeley -, the "Treatife of human nature ; 
 and of fcepticifm. 
 
 *TP H E prefent age, I apprehend, has not 
 produced two more acute or more pra&i- 
 fed in this part of philofophy, than the Bifhop 
 of Cloyne, and the author of the Treatife of hu- 
 man nature. The firft was no friend to fcepti- 
 ciim, but had that warm concern for religious 
 and moral principles which became his order: 
 yet the refult of his inquiry was, a ferious con- 
 vicYion, that there is no fuch thing as a material 
 world ; nothing in nature but fpirits and ideas ; 
 
 and 
 
Seflr.5. INTRODUCTION. jy 
 
 and that the belief of material fubftances, and of 
 abftraft ideas, are the chief caufes of all our er- 
 rors- in philofophy, and of all infidelity and here- 
 fy, in religion. His arguments are founded upon 
 the principles which were formerly laid down by 
 Des Cartes, Malebranche, and Locke, and which 
 have been very generally received. 
 
 And the opinion of the ableft judges feems to 
 be, that they neither have been, nor can be con- 
 futed ; and that he hath proved by unanfwerable 
 arguments what no man in his fenfes can believe. 
 
 The fecond proceeds upon the fame principles, 
 but carries them to their full length; and as the 
 Bilhop undid the whole material world, this au- 
 thor, upon the fame grounds, undoes the world 
 of fpirits, and leaves nothing in nature but ideas 
 and impreffions, without any fubject on which 
 they may be imprefied. 
 
 It feems to be a peculiar ftrain of humour in 
 this author, to fet out in his introduction, by 
 promifing, with a grave face, no lefs than a com- 
 plete fyftem of the fciences, upon a foundation 
 entirely new, to wit, that of human nature; 
 when the intention of the whole work is to fhew, 
 that there is neither human nature^nor fcience in 
 the world. It may perhaps be unreafonable t,o 
 complain of this conduct in an author, who nei- 
 ther believes his own exiftence, nor that of his 
 reader; and therefore could not mean to difap- 
 point him, or to laugh at his credulity. Yet I 
 cannot imagine, that the author of the Treatife 
 of human nature is fo fceptical as to plead -this 
 B apology. 
 
18 Of the HUMAN MIND. Chap.!. 
 
 apology. He believed, againft his principles, that 
 he ihould be read, and that he mould retain his 
 perfonal identity, till he reaped the honour and re- 
 putation jufllyduetohis metaphyCica.1 acumen. In- 
 deed he ingenuoufly acknowledges, that it was only 
 in folitude and retirement that he could yield any 
 aflfent to his own philofophy •, fociety, like day- 
 light, difpelledthedarknefsandfogs of fcepticifm, 
 and made him yield to the dominion of Common 
 Senfe. Nor did I ever hear him charged with 
 doing any thing, even in folitude, that argued 
 fuch a degree of fcepticifm as his principles main- 
 tain. Surely if his friends apprehended this, they 
 would have the charity never to leave him alone. 
 
 Pyrrho the Elean, the father of this philofo- 
 phy, feems to have carried it to greater perfec- 
 tion than any of his fuccefibrs : for if we may be- 
 lieve Antigonus the Caryftian, quoted by Dio- 
 genes Laertius, his life correfponded to his doc- 
 trine. And therefore, if a cart run againft him, or 
 a dog attacked him, or if he came upon a'precf- 
 pice, he would not ftir a foot to avoid the dan- 
 ger, giving no credit to his fenfes. But his atten- 
 dants, who, happily for him, were not fo great 
 fceptics, took care to keep him out of harm's 
 way ; fo that he lived till he was ninety years of 
 age. Nor is it to be doubted, but this author's 
 friends would have been equally careful to keep 
 him from harm, if ever his principles had taken 
 too ftrong a hold of him. 
 
 It is probable the Treatife of human nature was 
 not written in company; yet it cbritaihs'mani- 
 
 feft 
 
Sect. 5 . iNf RODtJtTlON. t 9 
 
 Fed indications, that the author every now and 
 then relapfed into the faith of the vulgar, and 
 could hardly, for half a dozen pages, keep up the 
 fceptical character. 
 
 In like manner, the great Pyrrho himfelf for- 
 got his principles on fome occafions -, and is faid 
 once to have been in fuch a paflion with his cook, 
 who probably had not roafted his dinner to hfs 
 mind, that with thefpit in his hand, and the meat 
 Upon it; he purfued him even into the market- 
 place. 
 
 It is a bold philofophy that rejects; without ce- 
 remonyj principles which irrefiftibly govern the 
 belief and the conduct of all mankind in the 
 common concerns of life ; and to which the phi- 
 lofopher himfelf mult yield, after he imagines he 
 hath confuted them. Such principles are older; 
 and of more authority, than Philofophy: (he refts 
 Upon them as her bafis, not they upon her. If fhe 
 could overturn them, (he muft be buried in their 
 ruins ; but all the engines of philofophical fubcil- 
 ' ty are too weak for this purpofe ; and the at- 
 tempt is no lefs ridiculous, than if a mechanic 
 fhould contrive an axis in peritrochib to remove 
 the earth out of its place ; or if a mathematician 
 fhould pretend to demonftfate, that things equal 
 to the fame thing are hot equal to one another. 
 Zeno endeavoured to demonftrate the impof- 
 fibility of motion -, Hobbes, that there was no 
 difference between right and wrong ; and this 
 author, that no credit is to be given to our fen- 
 fes, to our memory, or even to demonstration. 
 B 2 Such 
 
20 Of the HUMAN MIND. Chap, I. 
 Such philofophy is juftly ridiculous, even to thofe 
 who cannot detect the fallacy of it. It can have 
 no other tendency, than to ftiew the acutenefs of 
 the fophift, at the expence of difgracing reafon 
 and human nature, and making mankind Yahoos. 
 
 SECT. VI. 
 
 Of the Treatife of human nature. 
 
 "J~HEItE are other prejudices againft this 
 fyftem of human nature, which, even up- 
 on a general view, may make one diffident of it. 
 
 Des Cartes, Hobbes, and this author, have 
 each of them given us a fyftem of human nature j 
 an undertaking too vaft for .any one man, how 
 great foever his genius and abilities may be. 
 There muft furely be reafon to apprehend, that 
 many parts of human nature never came under 
 their obfervation •, and that others have been 
 ftretchedand diftorted, to fill up blanks, andcom- 
 plete the fyftem. Chriftopher Columbus, or Se- 
 baftian Cabot, might almoft as reafonably have 
 undertaken to give us a complete mapof America. 
 
 There is a certain character and ftyle in na- 
 ture's works, which is never attained in the molt 
 perfedl imitation of them. This feems to be 
 wanting in the fyftems of human nature I have 
 mentioned, and particularly inthelaft. One may 
 fee a puppet make variety of motions and aefti- 
 culations, which ftrike much at firft view *? but 
 when it is accurately obierved, and taken to 
 
 pieces, 
 
Seft.6. INTRODUCTION. 21 
 pieces, our admiration ceafes ; we comprehend 
 the whole art of the maker. How unlike is it 
 to that which it repre fents ! what a poor piece 
 of work compared with the body of a man, whofe 
 ftrufture the more we know, the more won- 
 ders we difcover in it, and the more fenfible we 
 are of our ignorance ! Is the mechanifm of the 
 mind fo eafily comprehended, when that of the 
 body is fo difficult ? Yet, by this fyftem, three 
 laws of affociation, joined to a few original feel- 
 ings, explain the whole mechanifm of fenfe, ima-. 
 gination, memory, belief, and of all the actions 
 and pafiions of the mind. Is this the man that 
 Nature. made ? I furpecT: it is not fo eafy to look 
 behind the fcenes in Nature's work. This is a 
 puppet furely, contrived by too bold an appren- 
 tice of Nature, to mimic her work. It fliews to- 
 lerably by candle light, but brought into clear 
 day, and taken to pieces, it will appear to be a 
 man made with mortar and a trowel. The more 
 we know of other parts of nature, the more we 
 like and approve them. The little I know of the 
 planetary fyftem ; of the earth which we inha- 
 bit; of minerals, vegetables, and animals; of my 
 own body, and of the laws which obtain in thefe 
 parts of nature, opens to my mind grand and beau- 
 tiful fcenes, and contributes equally to my hap- • 
 pinefs and power. But when I look within, and 
 confider the mind itfelf, which makes me capa- 
 ble of all thefe profpects and enjoyments ; if it is 
 indeed what the Treatife of human nature makes 
 it, I find I have been only in an incha'nted caftle, 
 B 3 impofed 
 
22 Of the HUM AN MIND. Chap. I, 
 jmpofed upon by fpeftres and apparitions. I blufb, 
 inwardly to think how I have been deluded ; I 
 am afnamed of my frame, and can hardly for- 
 bear expoftulating with my deftiny : Is this thy 
 paftime, O Nature, to put fuch tricks upon a fil- 
 ly creature, and then to take off the mafic, and 
 fhew him how he hath been befooled ? If this is 
 the philofophy of human nature, my foul enter 
 thou not into her fecrets. It is furely the forbidden, 
 tree of knowledge; I no fooner tafte of it, than 
 I perceive rnyfelf naked, and ftript of all things, 
 yea even of my very felf. 1 fee rnyfelf, and the 
 whole frame of nature, {brink into fleeting ideas, 
 which, like Epicurus's atqms, dance about in, 
 emptinefs. 
 
 S E C T. VII. 
 
 The fyjlem of all tbefe authors is tbffame, and leads 
 to fcepticifm. 
 
 T)UT what if thefe profound difquifitions into 
 the firft principles of human nature, do natu- 
 rally and neceffarily plunge a man into this abyfs 
 of fcepticifm ? May we not reafonably judge fa 
 from what hath happened ? Des Cartes no foon- 
 er began to dig in this mine, than fcepticifm was 
 ready to break in upon him. He did what he 
 could to (hut it out. Malebranche and Locke, 
 who dug deeper, found the difficulty of keeping 
 out this enemy ftill to increafe •, but they la- 
 boured honeftly in the defign. Then Berkeley, 
 
 v/ho 
 
.Seft. 7. INTRODUCTION. 23 
 
 who carried on the work, defpairing of fecuring 
 all, bethought himfelf of an expedient : By gi- 
 ving up the material world, which he thought 
 might be fpared without lofs, and even with ad- 
 vantage, he hoped by an impregnable partition 
 to fecure the world of fpirits. But, alas ! the 
 Treatife of human nature wantonly fapped the 
 foundation of this partition, and drowned all in 
 one univerfal deluge. 
 
 Thefe fa&s, which are undeniable, do indeed 
 give reafon to apprehend, that Des Cartes's fy- 
 ftem of the human understanding, which I fliall 
 beg leave to call the ideal fyft em, and which, with 
 fome improvements made by later writers, is now 
 generally received, hath fome original defect; 
 that this fcepticifm is inlaid in it, and reared 
 along with it; and, therefore, that we mull: lay it 
 open to the foundation, and examine the materi- 
 als, before we can expedt to raife any folid and ufe- 
 ful fabric of knowledge on this fubjed, 
 
 SECT. VIII. , 
 
 We ought not to defpair of a better. 
 
 Y> U T is this to be defpaired of, becaufe Des 
 Cartes and his followers have failed ? by no 
 means. This pufillanimity would be injurious to 
 ourfelves,- and injurious to truth. Ufeful difco- 
 veries are fometimes indeed the effecT: of iuperior 
 genius, but more frequently they are the birth of 
 time and of accidents. A traveller of good judg- 
 
 B 4 nunc 
 
24 OftheHUMAN MIND. Chap. I. 
 
 ment may miftake his way, and be unawares led 
 into a wrong track; and while the road is fair 
 before him, he may go on without fufpicion and 
 be followed by others ; but when it ends in a 
 coal-pit, it requires no great judgment to know 
 that he hath gone wrong, nor perhaps to find out 
 what mifled him. 
 
 In the mean time, the unprofperous ftate of this 
 part of philofophy hath produced an effect, fome- 
 what difcouraging indeed to any attempt of this 
 nature, but an effect which might be expected, 
 and which time only and better fuccefs can reme- 
 dy. Senfible men, who never will be fceptics in 
 matters of common life, are* apt to treat with fo- 
 vereign contempt every thing that hath been 
 faid, or is to be faid, upon this fubject. It is me- 
 taphyfic, fay they : Who minds it ? Let fchola- 
 ftic fophifters intangle themfelves in their own 
 cobwebs ; I am refolved to take my own exift- 
 ence, and the exiftence of other things, upon 
 trnft •, and to believe that fnow is cold, and ho- 
 ney fweet, whatever they may fay to the contra- 
 ry. He muft either be a fool, or want to make 
 a fool of me, that would reafon me out of my rea- 
 fon and fenfes. 
 
 I confefs I know not what a fceptic can anfwer 
 to this, nor by what good argument he can plead 
 even for a hearing ; for either his reafoning is fo- 
 phiftry, and fo deferves contempt; or there is no 
 truth in human faculties, and then why mould 
 
 we reafon ? 
 
 ,. ,• .„: If 
 
Seft.8. INTRODUCTION. a$ 
 If therefore a man find himfelf intangled in 
 thefe metaphyfical toils, and can find no other 
 way to efcape, let him bravely cut the knot which 
 he cannot loofe, curfe metaphyfic, and diffuade 
 every man from meddling with it. For if I have 
 been led into bogs and quagmires by following 
 an ignis fqtuus, what can I do better than to 
 warn others to beware of it ? If Philofpphy con- 
 tradicts herfelf, befools her votaries, and deprives 
 them of every object worthy to be purfued or 
 enjoyed, let her be fent back to the infernal re- 
 gions from which Ihe mull have had her original. 
 But is it abfolutely certain that this fair lady 
 is of the party ? Is it not poifible fhe may have 
 been mifreprefented ? Have not men of genius in- 
 former ages often made their own dreams to pafs 
 for her oracles ? Ought lhe then to be condemn- 
 ed without any farther hearing ? This would be 
 unreafonable. I have found her in "all "other mat- 
 ters an agreeable companion, a faithful counfel- 
 lor, a friend to Common Senfe, and to the hap- 
 pinefs of mankind. This juftly intitles her to 
 my correfpondence arid confidence, till I find 
 pfallible proofs of her infidelity. 
 
 CHAP. 
 
#6 
 
 CHAP. II, 
 Of SMELLING. 
 
 SECT. I. 
 
 The order of proceeding. 'Of the medium and, 
 organ of fmell, 
 
 T T is fo difficult to unravel the operations of 
 the human understanding, and to reduce 
 them to their firft principles, that we cannot 
 expect to fucceed in the attempt, but by begin- 
 ning with the ' fimpleft, and proceeding by very 
 cautious fteps to the more complex. The five 
 external fenfes may, for this reafon, claim to be 
 firft confidered in an analyfis of the human facul- 
 ties. And the fame reafon ought to determine us 
 to make a choice even among the fenfes, and to 
 give the precedence, not to the nobleft, or moft 
 ufeful, but to the fimpleft, and that whofe objects 
 are leaft in danger of being miftaken for other 
 things. 
 
 In this view, an analyfis of our fenfations may 
 be carried on, perhaps with moft eafe and diftinct- 
 nefs, by taking them in this order : Smelling, 
 Tafting, Hearing, Touch, and, laftof all, Seeing. 
 Natural philofophy informs us, that all animal 
 and vegetable bodies, and probably all or moft 
 other bodies, while expofed to the air, are conti- 
 nually fending forth effluvia of vaft fubtilty, not 
 6 only 
 
Sedti. Of SMELLING. %y 
 
 only in their ftate of life and growth, but in the 
 ftates of fermentation and putrefaction. Thefe 
 volatile particles do probably repel each other, 
 and fo fcatter themfelves in the air, until they 
 meet with other bodies to which they have fome 
 chymical affinity, and with which they unite, and 
 form new concretes. All the fmell of plants, and 
 of other bodies, is caufed by thefe volatile parts, 
 " and is fmelled wherever they are fcattered in the 
 air : And the acutenefs of fmell in fome animals, 
 ihews us, that thefe effluvia fpread far, and mufj; 
 be inconceivably fubtile. 
 
 Whether, as fome chymifts conceive, every 
 fpecjes of bodies hath afpiritus reffor, a kind of 
 foul, which caufes the fmell, and all the fpecific 
 virtues of that body, and which, being extreme- 
 ly volatile, flies about in the air in queft of a'pro- 
 per receptacle, I do not inquire. This, like moft 
 other theories, is perhaps rather the product of 
 imagination than of juft induction. But that all 
 bodies arefmelled by means of effluvia which they 
 emit, and which are drawn into the noftrils 
 fllong with the air, there is no reafon to doubt. 
 So that there is manifeft appearance of defign in 
 placing the organ of fmell in the infide of that 
 panal, through which the air is continually pafs- 
 ing in inipiration and expiration. 
 
 Anatomy informs us, that the membrana pitui- 
 taria, and'th'e olfactory nerves, which are diftri- 
 buted %o the villous parts of this membrane, are 
 the organs deftined by the wifdom of nature to 
 f;hj,s fenfe ; fo that when a body emits no efflu- 
 via, 
 
aS Of the HUMAN MIND. Chap. II. 
 
 via, or when they do not enter into the nofe, or 
 ■when the pituitary membrane or olfactory nerves 
 are rendered unfit to perform their office, it can- 
 not be fmelled. 
 
 Yet, notwithftanding this, it is evident, that 
 neither the organ of fmell, nor the medium, nor 
 any motions we can conceive excited in the mem- 
 brane above mentioned, or in the nerve or ani- 
 mal fpirits, do in the leaft refemble the fenfation 
 of fmelling} nor could that fenfation of itfelf 
 ever have led us to think of nerves, animal fpi- 
 rits, or effluvia. 
 
 SECT. II. 
 
 The fenfation confldered abftraBly, 
 
 TT A V I N G premifed thefe things, wiph 
 regard to the medium and organ of 
 this fenfe, let us now attend carefully to what 
 the mind is-confcious of when we fmell a rofe or 
 a lily ; and fxnce our language affords no other 
 name for this fenfation, we fhall call \t a fmell or 
 odour, carefully excluding from the meaning of 
 thofe names every thing but the fenfation itfelf, 
 at leaft till we have examined it. 
 
 Suppofe a perfon who never had this fenfe be- 
 fore, to receive it all at once, and to fmell a 
 rofe; can he perceive any fimilitude or agree- 
 ment between the fmell and the rofe ? or indeed 
 between it and any other objeft whatfoever ? 
 Certainly he cannot. He finds himfelf affe&ed 
 
Sea. 2. Of SMELLING. 29 
 
 in a new way, he knows not why or from what 
 caufe. Like a man that feels fome pain or plea- 
 fure formerly unknown to him, he is confcious 
 that he is not the caufe of it himfelf ; but can- 
 not, from the nature of the thing, determine 
 whether it is caufed by body or fpirit, by fome* 
 thing near, or by fomething at a diftance. It 
 has no fimilitude to any thing elfe, fo as to ad- 
 mit of a comparifon ; and therefore he can con- 
 clude nothing from it, unlefs perhaps that there 
 muft be fome unknown caufe of it. 
 
 It is evidently ridiculous, to afcribe to it 
 figure, colour, extenfion, or any other quality of 
 bodies. He cannot give it a place, any more 
 than he, can give a place to melancholy or joy : 
 nor can he conceive it to have any exiftence, but 
 when it is fmelled. So that it appears to be*'. a 
 fimple and original affe&ion or feeling of the 
 mind, altogether inexplicable and unaccountable. 
 It is indeed impoflible that it can be in any body : 
 It is a fenfation, and a fenfation can only be in a 
 fentient thing. 
 
 The various odours have each their different 
 degrees of ftrength or weaknefs. Moft of them 
 are agreeable or difagreeable ; and frequently 
 thofe that are agreeable when weak, are difagree- 
 able when ftronger. When we compare diffe- 
 rent fmells together, we can perceive very few 
 refemblances or contrarieties, or indeed relations 
 of any kind between them. They are all fo fimple 
 in' themfelves, and fo different from each other, 
 that it is hardly poflible to divide them into gene- 
 8 ra % 
 
3 o Of the H U M A N M I N D. Chap. ft. 
 ra, and /pedes.. ' Moft of the names we give 
 them are particular ; as the fmell of a rofe, of a 
 jejfamine, and the like. Yet there are fome ge- 
 neral names ; as fweet, Jlinkifig, mufly, putrid^ 
 cadaverous, aromatic. Some of them feem to re- 
 frefh and animate the mind, others to deaden 
 and deprefs it. 
 
 SECT. III. 
 
 Senfatioti and rememhrance, natural principles of 
 belief. 
 
 C O far we have confidered this fenfation ab- 
 ftraclly. Let us next compare it with other 
 things to which it bears fome relation. And 
 firft I mall compare this fenfation with the re- 
 membrance^ and the imagination of it. 
 
 I can think of the fmell of a rofe when I 
 do not fmell it •, and it is poffible that when I 
 think of it, there is neither rofe nor fmell any 
 where exifting. But when I fmell it, I am ne- 
 ceflarily determined to believe that" the fenfa-* 
 fation really exifts. This is common to all fenfa- 
 tions, that as they cannot exift but in being per- 
 ceived, fo they cannot be perceived but they 
 muft exift. I tould as eafily doubt of my own 
 exiftence, as of the exiftence of my fenfationsi 
 Even thofe profound philofophdrs who have en- 
 deavoured to difprove their own exiftence, have 
 yet left their fenfations to ftand upon their own 
 
 bottom, 
 
Se£t. 3. Of SMELLING. 3* 
 
 bottom, ftript of a fubjeft, rather than call in 
 queftion the reality of their exiftence. 
 
 Here then a fenfation, a fmell for inftance, 
 may be prefented to the mind three different 
 ways : it may be fmelled, it may be remember- 
 ed, it may be, imagined or thought of. In the 
 firfl: cafe, it is nece'fTarily accompanied with a 
 belief of its prefent exiftence -, in the fecond, 
 it is neceffarily accompanied with a belief of its 
 paft exiftence ; and in the laft, it is not accom- 
 panied with belief at all, but is what the logi- 
 cians call a Jimph apprehenjion: 
 
 "Why fenfation fhould compel our belief of 
 the prefent exiftence of the thing, memory a 
 belief of its paft exiftence, and imagination no 
 belief at all, I believe no philofopher can give 
 a fhadow of reafon, but that fuch is the nature of 
 thefe operations : They are all fimple and origi- 
 nal, and therefore inexplicable acts of the 
 mind. 
 
 Suppofe that once, and only once, I fmelled 
 a tuberofe in a certain room where it grew in 
 a pot, and gave a very grateful perfume. Next 
 day I relate what I faw and fmelled. When I 
 attend as carefully as I can to what paffes in my 
 mind in this cafe, it appears evident, that the 
 very thing I faw yefterday, and the fragrance I 
 fmelled, are now the immediate objects of my 
 mind when I remember it. Further, I can ima- 
 gine this pot and flower tranfported to the room 
 where I now fit, and yielding the fame perfume. 
 Here likewife it appears, that the individual thing 
 
 which 
 
$2 Of the H U M A N M I N D. Chap. If; 
 which I faw and fmelled, is the objecl: of my ima- 
 gination. 
 
 Philofophers indeed tell me, that the imme- 
 diate object of my memory and imagination in 
 this cafe, is not thepaftfenfation, but an ideaof it, 
 an image, pharitafm, or fpecies of the odour 
 I fmelled : that this idea now exifts in my mind* 
 or in my fenforium •, and the mind contemplating 
 this prefentidea, finds it a reprefentation of what 
 is paft, or. of what may exift ; and accordingly 
 calls it memory, or imagination. This is the 
 dodtrine of the ideal philofophy ; which we fhall 
 not now examine, that we may not interrupt the 
 thread of the prefent investigation. Upon the 
 ftridteft attention, memory appears to me to 
 have things that are paft, and not prefent ideasj 
 for its object. We fhall afterwards examine this 
 fyftem of ideas, and endeavour to make it ap- 
 pear, that no folid proof has ever been advanced 
 of the existence of ideas ; that they are a mere 
 fiction and hypothefis, contrived to folve the 
 phaenomena of the human understanding ; that 
 they do not at all anfwer this end ; and that this 
 hypothefis of ideas or images of things in the 
 mind, or in the fenforium, is the parent of thofe 
 many paradoxes fo fhocking to common fenfe, 
 and of that fcepticifm, which difgrace our phi- 
 lofophy of the, mind, and have brought upon it 
 the ridicule and contempt of fenfible men. 
 
 In the mean time, I beg leave to think with 
 the vulgar, that when I remember the fmell of 
 the tuberofe, that very fenfation which I had 
 
 yefterday, 
 
Sect. 3. Of SMELLING. 33 
 
 yefterday, and which has now no more any ex- 
 iftence, is the immediate object of my memory » 
 and when I imagine it pfefent, the fenfation it- 
 felf, and not any idea of it, is the object of my 
 imagination. But though the object of my fen- 
 fation, memory, and imagination, be in this cafe 
 the fame, yet thefe acts or operations of the 
 mind are as different, and as eafily diftinguifti- 
 able, as fmell, taftej and found. I am confcious 
 of a difference in kind between fenfation and me- 
 mory, and between both and imagination. I 
 find this alfoj that the fenfation compels my be- 
 lief of the prefent exiftence of the fmell, and 
 memory my belief of its pad exiftence. There 
 is a fmell, is the immediate teftimony of fenfe ; 
 there Was a fmell, is the immediate teftimony of 
 memory. If you afk me, why I believe that the 
 fmell exifts ? I can give no other reafon, nor 
 fhall ever be able to give any other, than that I 
 fmell it. If you afk- why I believe that it ex- 
 ifted yefterday ? I can give no other reafon but 
 that I remember it. 
 
 Senfation and memory therefore are fimple, 
 Original, and perfectly diftirtct operations of the 
 mind, and both of them are original principles 
 of belief. Imagination is diftinct from both, 
 but is no principle of belief. Senfation implies 
 the prefent exiftence of its object ; memory its 
 paft exiftence ; but imagination views its object 
 naked, and without any belief of its exiftence or 
 non-exiftence, . and is therefore what the fchools 
 cv\\ fimple appreh.enfion. 
 
 C SECT. 
 
34 Of the HUMAN MIND. Chap, II. 
 
 SECT. IV. 
 
 Judgment and belief in fome cafes precede fimple 
 apprehenfion. 
 
 "OUT here again the ideal fyftem comes in our 
 way : it teaches us, that the firft operation 
 of the mind about its ideas, is fimple apprehen- 
 fion ; that is, the bare conception of a thing 
 without any belief about it ; and that after we 
 have got fimple apprehenfions, by comparing 
 them together, we perceive agreements or difa- 
 greements between them ; and that this percep- 
 tion of the agreement or difagreement of ideas, 
 is all that we call belief, judgment, or know- 
 ledge. Now, this appears to me to be all fic- 
 tion, without any foundation in nature : for it 
 is acknowledged by all, that fenfation muft go 
 before memory and imagination ; and hence it 
 neceffarily follows, that apprehenfion accompa- 
 nied with belief and knowledge, mull go before 
 fimple apprehenfion, at leaft in the matters we 
 are now fpeaking of. So that here, inftead of 
 faying, that the belief or knowledge is got by 
 putting together and comparing the fimple ap- 
 prehenfions, we ought rather to fay, that the 
 fimple apprehenfion is performed by refolving 
 and analysing a natural and original judgment. 
 And it is with the operations of the mind, in 
 this cafe, as with natural bodies, which are in- 
 deed compounded of fimple principles or ele- 
 ments. 
 
Seft. 4. Of SMELLING. 33 
 
 ments. Nature does not exhibit thefe eleriients 
 feparate, to be compounded by us ; fhe exhibits 
 them mixed and compounded in concrete bodies, 
 and it is only by art and chymical analyfis that 
 they can be feparated. 
 
 SECT. V. 
 
 Two theories of the nature of belief refuted. Con* 
 clujiom from what hath been faid. 
 
 DUT what is this belief or knowledge which 
 accompanies fenfation aud memory ? Every 
 man knows what it is, but no man can de- 
 fine it. Does any man pretend to define fenfa- 
 tion, or to define confcioufneis ? It is happy in* 
 deed that no man does. And if no philofopher 
 had endeavoured to define and explain belief, 
 fome paradoxes in philofophy, more incredible 
 than ever were brought forth by the moft abjecT: 
 fuperftition, or the moft frantic enthufiafm, had 
 never feen the light. Of this kind furely is 
 that modern difcovery of the ideal philofophy, 
 that fenfation, memory, belief, and imagina- 
 tion, when they have the fame object, are only 
 different degrees of ftrength and vivacity in the 
 idea. Suppofe the idea to be that of a future 
 ftate after death ; one man believes it firmly 5 
 this means no more than that he hath a ftrong 
 and lively idea of it : Another neither believes 
 nor difbelieves ; that is,* he has a weak and faint 
 idea. Suppofe now a third perfon believes firm-* 
 C 2 ly 
 
3 6 Of the HUMAN MIND. Chap. II. 
 ly that there is no fuch thing ; I am at a lofs 
 to know whether his idea be faint or lively : If 
 it is faint, then there may be a firm belief where 
 the idea is faint ; if the idea is lively, then the be- 
 lief of a future ftate and the belief of no future 
 ftate muft be one and the fame. The fame ar- 
 guments that are ufed to prove that belief implies 
 only a ftronger idea of the object than fimple ap- 
 prehenfion, might as well be ufed to prove that 
 love implies only a ftronger idea of the object 
 than indifference. And then what fhall we fay 
 of hatred, which muft upon this hypothefis be 
 a degree of love, or a degree of indifference ? 
 If it fhould be faid, that in love there is fome- 
 thing: more than an idea, to wit, an affection of 
 
 o 
 
 the mind ; may it not be faid with equal reafon, 
 that in belief there is fomething more than an 
 idea, to wit, an affent or perfuafion of the mind ? 
 But perhaps it may be thought as ridiculous to 
 argue againft this ftrange opinion, as to maintain 
 it. Indeed, if a man fhould maintain, that a 
 circle, a fquare, and a triangle, differ only in 
 magnitude, and not in figure, I believe he would 
 find nobody difpofed either to believe him or to 
 argue againft him ; and yet I do not think it lefs 
 (hocking to common fenfe, to maintain, that 
 fenfation, memory, and imagination, differ Only 
 in degree, and not in kind. I know it is faid, 
 that in a delirium, or in dreaming, men are apt 
 to miftake one for the other. But does it fol- 
 low from this, that men' who are neither dream- 
 ing, nor in a delirium, cannot diftinguifh them ? 
 
 But 
 
Sea. 5. Of SMELLING. 37 
 
 But how does a man know, that he is not in a 
 delirium ? I cannot tell : neither can I tell how 
 a man knows that he exifts : But if any man fe- 
 rioufly doubts whether he is in a delirium, I 
 think it highly probable that he is, and that it 
 is time to feek for a cure, which I am perfuad- 
 ed he will not find in the whole fyftem of logic. 
 
 I mentioned before Locke's notion of belief 
 or knowledge : he holds that it eonfifts in a per- 
 ception of the agreement or difagreement of 
 ideas ; and this he values himfelf upon as a very 
 important difcovery. 
 
 We fhall have occafion afterwards to examine 
 more particularly this grand principle of Locke's 
 .philofophy, and to Ihew that it is one of the 
 main pillars of modern fcepticifm, although he 
 had no intention to make that ufe of it. At 
 prefent let us only confider how it agrees with 
 the inftances of belief now under confideration ; 
 and whether it gives any light to them. I be- 
 lieve that the fenfation I have, exifts ; and that 
 the fenfation I remember, does not now exift, 
 but did exift yefterday. Here, according to 
 Locke's fyftem, I compare the idea of a fenfation 
 with the ideas of paft and prefent exiftence : at 
 one time I perceive that this idea agrees with 
 that of prefent exiftence, butdifagrees with that of 
 paft exiftence ; but at another time it agrees with 
 the ideaof paft exiftence, and difagtiees with that of 
 prefent exiftence. Truly thefe ideas feem to be 
 yery capricious in their agreements and difagree- 
 ments. Befides, 1 cannot for my heart con- 
 C 3 ceiye 
 
g« Ofthe HUMAN MIND. Chap. II, 
 ceive what is meant by either. I fay a fenfation 
 exifts, and I think I understand clearly what I 
 mean. But you want to make the thing clearer, 
 and for that end tell me, that there is an agree- 
 ment between the idea of that fenfation and 
 the idea of exiftence. To fpeak freely, this 
 conveys to me no light, but darknefs ; I can 
 conceive no otherwife of it, than as an odd and 
 obfcure circumlocution. I conclude, then, that 
 the belief which accompanies fenfation and me- 
 mory, is a fimple aft of the mind, which can?- 
 not be defined. It is in this refpefl: like feeing 
 and hearing, which can never be fo defined as 
 to be underftood by thofe who have not thefe fa- 
 culties : and to fuch as have them, no definition 
 can make thefe operations more clear than they 
 are already. In like manner, every man that 
 has any belief, and he muft be a curiofity that 
 has none, knows perfectly what belief is, but 
 can never define or explain it. I conclude alfo, 
 that fenfation, memory, and imagination, even 
 where they have the fame object, are operations 
 pf a quite different nature, and perfectly diftin- 
 guifhable by thofe who are found and fober. A 
 .man that is in danger of confounding them, is 
 indeed to be pitted -, but whatever relief he may 
 find from another airth, he can find none from lo- 
 gic or metaphyfic. I conclude further, that it 
 js no lefs a part of the human conftitution, to 
 believe the prefent exiftence of our fenfations, 
 and to believe the paft exiftence of what we re- 
 rnerriber ? fhan it is to believe that twice two 
 
 ipak,s 
 
Sett. 5. Of S M E L L I N G. 39 
 
 make four. The evidence of fenfe, the evi- 
 dence of memory, and the evidence of 
 the neceffary relations of things, are all di- 
 ftincl: and original kinds of evidence, equal- 
 ly grounded on Our conltitution : none of them 
 depends upon, or can be refolved into another. 
 To reafon againft any of thefe kinds of evidence, 
 is abfurd ; nay to reafon for them, is abfuid. 
 They are firft principles ; and fuch fall not with- 
 in the province of Reafon, but of Common 
 Senfe. 
 
 SECT. VI. 
 
 Apology for metaphyseal abfurdities. Senfation 
 without a fentient, a canfequence of the theory 
 of ideas. Conferences of this Jlrange opi- 
 nion. 
 
 Tjr A VI NG confidered the relation which the 
 fenfation of fmelling bears to the remem- 
 brance and imagination of it, I proceed to con- 
 fider, what relation it bears to a mind, or fen- 
 tient principle. It is certain, no man can con- 
 ceive or believe fmelling to exift of itfelf, with- 
 out a mind, or fomething that has the power of 
 fmelling, of which it is called a fenfation, an 
 operation, or feeling. Yet if any man fhould 
 demand a proof, that fenfation cannot be with- 
 out a mind or fentient being, I conf'efs that I 
 can give none ; and that to pretend to prove it, 
 feems to me almoft as abfurd as to deny it. 
 
 This 
 C 4 
 
40 Ofthe HUMAN MIND. Chap. II. 
 
 This might have been faid without any apo- 
 logy before the Treatife of human nature appear- 
 ed in the world. For till that time no man, as 
 far as I know, ever thought either of calling 
 in queftion that principle, or of giving a 
 reafon for his belief of it. Whether think- 
 ing beings were of an ethereal or igneous nature, 
 whether material or immaterial, was varioufly 
 difputed ; but that thinking is an operation of 
 fome kind of being or other, was always taken 
 for granted, as a principle that could not pof- 
 fibly admit of doubt. 
 
 However, fince the author above mentioned, 
 who is undoubtedly one ofthe m oft acute meta- 
 phyficians that this or any age hath produced, 
 hath treated it as a vulgar prejudice, and maintain- 
 ed, that the mind is only a fucceffion of ideas 
 and impreffions without any fubjecT: ; his opini- 
 on, however contrary to the common apprehen- 
 sions of mankind, deferves refpect. I beg there- 
 fore, once for all, that no offence may be taken 
 at charging this or other metaphyfical notions 
 with abfurdity, or with being contrary to the 
 common fenfe of mankind. No difparagement 
 is meant to the underftandings ofthe authors or 
 maintainers of fuch opinions. Indeed, they com- 
 monly proceed not from defect of understanding, 
 but from an excefs of refinement : the reafoning 
 that leads to them, often gives new light to the 
 fubjecT, and fliews real genius and deep penetra- 
 tion in the author ; and the premifes do more 
 
 than attone for the conclufion, 
 
 .: v ,.. .... ■. • |f 
 
Seft. 6. Of SMELLING, 41 
 
 If there are certain principles, as I think there 
 are, which the conftitution of our nature leads 
 ,us to believe, and which we are under a necef- 
 lity to take for granted }n the common concerns 
 of life, without being able to give a reafon for 
 jhem ; thefe are what we call the principles of 
 common fenfe ; and what is manifestly contrary 
 to them, is what we call abfurd. 
 
 Indeed, if it is true, and to be received as a prin- 
 ciple of philofophy, That fenfation and thought 
 may be without a thinking being ; it muft be 
 acknowledged to be the moft wonderful difcove^ 
 ry that this or any other age hath produced. The 
 received doctrine of ideas is the principle from 
 which it is deduced, and of which indeed it feems 
 to be a juft and natural confequence. And it is 
 probable, that it would not have been fo late a 
 difcovery, but that it is fo fhocking and repug- 
 nant to the common apprehenlions of mankind, 
 that it required an uncommon degree of philofo- 
 phical intrepidity to ufher it into the world. ' It 
 is a fundamental principle of the ideal fyftem, 
 That every object of thought muft be an impref- 
 fion, or an idea, that is, a faint copy of fome 
 preceding impreffion. This is a principle fo 
 commonly received, that the author above men- 
 tioned, although his whole fyftem is built upon 
 it, never offers the leaft proof of it. It is upon 
 this principle, as a fixed point, that he erects 
 his metaphyfical engines, to overturn heaven and 
 earth, body and fpirit. And indeed, in my ap- 
 prehenfion, it is altogether fufficient for the pur- 
 ' 5 k pofe. 
 
4 z Of the HUMAN MIND. Chap. II. 
 pofe. For if impreffions and ideas are the on- 
 ly objects of thought, then heaven and earth, 
 and body and fpirit, and every thing you pleafe, 
 muft fignify only impreffions and ideas, or they 
 muft be words without any meaning. It feems, 
 therefore, that this notion, however orange, is 
 clofely connected with the received doctrine of 
 ideas, and we muft either admit the conGlufion," 
 or call in queftion the premifes. 
 
 Ideas feem to have fomething in their nature 
 unfriendly to other exiftences. They were firft 
 introduced into philofophy, in the humble cha- 
 raft^r of images or reprefentatives of things ; and 
 in this character they feemed not only to be in- 
 offenfive, but to ferve admirably well for ex- 
 plaining the operations of the human understand- 
 ing. But fince men began to reafon clearly and 
 diftinctly about them, they have by degrees fup- 
 planted their conftituents, and undermined the 
 exiftence of every thing but themfelves. Firft, 
 they difcarded all fecondary qualities of bodies ; 
 and it was found out by their means, that fire is 
 not hot, nor fnow cold, nor honey fweet ; and, 
 in a word, that heat and cold, found, colour, 
 tafte, and ftnell, are nothing but ideas or impref- 
 fions, Bilhop Berkeley advanced them a ftep 
 higher, and found out, by juft reafoning, from 
 thefame principles, thatextenfion, folidity, fpace, 
 figure, and body, are ideas, and that there is no- 
 thing in nature but ideas and fpirits. But the 
 triumph of ideas was completed by the Treatife 
 of human nature, which difcards fpirits alfo, and 
 
 leaves 
 
Sett. 6. Of S M E L L I N G. 43 
 
 leaves ideas and impreffions as the fole exiftences 
 in the univerfe. What if at laft, having nothing 
 elfe to contend with, they mould fall foul of 
 one another, and leave no exiftence in nature at 
 all? This would furely bring philofophy into 
 danger •, for what fhould we have left to talk or 
 to difpute about ? 
 
 However, hitherto thefe philofophers acknow- 
 ledge the exiftence of impreffions and ideas -, they 
 acknowledge certain laws of attraction, or rules 
 of precedence, according to which ideas and im- 
 preffions range themfelves in various forms, and 
 fucceed one another: but that they fhould be- 
 long to a mind, as its proper goods and chattels, 
 this they have found to be a vulgar error. Thefe 
 ideas are as free and independent as the birds of 
 the air, or as Epicurus's atoms when they purfuqd 
 their journey in the vaft inane. Shall we con- 
 ceive them like the films of things in the Epicu- 
 rean fyftem ? 
 
 Vrincipio hoc dicp, rerum firmdacra vagarj, 
 MultH modis multis, in cuntlas undique parieif 
 Tenuia, qu^e facile inter fe junguntur in auris, 
 Qfrvia cum yeniunt. Lucr. 
 
 Or do they rather refemble Ariftotle's intelligi- 
 ble fpecies after they are fhot-forth from the, ob- 
 ject, and before they have yet (truck upon the 
 paffive intellect ? But why fhould we feek to com- 
 pare them with any thing, fince there is nothing 
 >n nature but themfelves ? They make the whole 
 
 furniturg 
 
44 Of the HUMAN MIND. Chap. II. 
 furniture of the univerfe ; ftarting into exiftence, 
 or out of it, without any caufe ; combining in- 
 to parcels, which the vulgar call minds ; and fuc- 
 ceeding one another by fixed laws, without time, 
 place, or author of thofe laws. 
 
 Yet, after all, thefe felf-exiftent and indepen- 
 dent ideas look pitifully naked and deftitute, 
 when left thus alone in the univerfe, and feefn, 
 upon the whole, to be in a worfe condition than 
 they were before. Des Cartes, Malebranche, 
 and Locke, as they made much ufe of ideas, 
 treated them handfomely, and provided them in 
 decent accommodation; lodging them either in the 
 pineal gland, or in the pure intellect, or even in 
 the divine mind. They moreover clothed them 
 with a commiffion, and made them reprefenta- 
 tives of things, which gave them fome dignity 
 and character. But the Treat ife of human nature, 
 though no lefs indebted to them, feems to have 
 made but a bad return, by bellowing upon them 
 this independent exiftence-, fince thereby they 
 are turned out of houfe and home, and fet adrift 
 in the world, without friend or connexion, with- 
 out a rag to cover their nakednefs ; and who 
 knows but the whole fyftem of ideas may perifh 
 by the indifcreet zeal of their friends to exalt 
 them ? 
 
 However this may be, it is certainly a moft 
 amazing difcovery, that thought and ideas may 
 be without any thinking being. A difcovery big 
 with confequences which cannot eafily be traced 
 by thofe deluded mortals who think and reafon in 
 
 the 
 
Seft. 6. OfSMELLING. 45 
 
 the common track, We were always apt to ima- 
 gine, that thought fuppofed a thinker, and love a 
 lover, and treafon a traitor : but this, it feems, 
 was all a miftake ; and it is found out, that there 
 .may be treafon without a traitor, and love with- 
 out a lover, laws without a legifiator, and punifh- 
 ment without a fufferer, fucceflion without time, 
 and motion without any thing moved, or fpace 
 in which it may move : or if, in thefe cafes, ideas 
 are the lover, the fufferer, the traitor, it were 
 to be wifhed - that the author of this difcovery 
 had farther condefcended to acquaint us, whe- 
 ther ideas can converfe together, and be under 
 obligations of duty or gratitude to each other ; 
 whether they can make promifes and enter into 
 leagues and covenants, and fulfil or break them, 
 and be punifhed for the breach ? If one fetof ideas 
 makes a covenant, another brezks it, and a third 
 is punilhed for it, there is reafon to think that 
 juftice is no natural virtue in this fyftem. 
 
 It feemed very natural to think, that the Trea- 
 tife of human nature required an author, and a 
 very ingenious one too; but now we learn, that 
 it is only a fet of ideas which came together, 
 and arranged themfelves by certain aflbciations 
 and attractions. 
 
 After all, this curious fyftem appears not to 
 be fitted to the prefent ftate of human nature. 
 How far it may fuit forrie choice fpirits, w,ho are 
 refined from the dregs of common fenfe, I can- 
 not fay. It is acknowledged, I think, that even 
 thefe can enter into this fyftem only in their moft 
 
 Ipeculative 
 
46 Of the H U M A N M I N D. Chap. If, 
 
 fpeculative hours, when they foarfo high in pur- 
 fuit of thofe felf-exiftent ideas, as to lofe fight of 
 all other things. But when they condefcend to 
 mingle again with the human race, and to con- 
 verfe with a friend, a companion, or a fellow ci- 
 tizen, the ideal fyflem vanifhes ; common fenfe, 
 like an irrefiftible torrent, carries them along 5 
 and, in fpite of all their reafoning arid philofophy* 
 they believe their own exiftence, and the exifi> 
 ehce of other things. 
 
 Indeed, it is happy they do fo ; for if they* 
 ihould carry their clofet belief into the world, 
 the reft of mankind would confider them as dif- 
 eafed, and fend them to an infirmary. Therefore, 
 as Plato required certain previous qualifications 
 of thofe who entered his fchool, I think it would 
 be prudent for the doctors of this ideal philofo- 
 >phy to do the faitse, and to refufe admittance to 
 every man who is fo weak, as to imagine that he 
 ought to have the fame belief in folitude and in 
 company., or that his principles ought to have 
 any influence upon his practice : for this philofo- 
 phy is like a hobby-horfe, which a man in bad 
 health may ride in his clofet, without hurting his 
 reputation; but if he fhould take him abroad 
 with him to church, or to the exchange, or to 
 the play-houfe, his heir would immediately call a 
 jury, andfeize his eftate. 
 
 SECT. 
 
Se&7< Of SMELLING. 47 
 
 SECT. VII. 
 
 The conception and belief of a fentient being or 
 mind, is fuggefted by our conftitution. The no- 
 tion of relations not always got by comparing the 
 related ideas. 
 
 T EAVlNG this philofbphy therefore to 
 thofe who have occafion for it, and can ufe 
 it difcreetly as a chamber-exercife, we may ftill 
 inquire, how the reft of mankind, and even the 
 adepts themfelves, except in fome folitary mo- 
 ments, have got fo ftrong and irrefiflible a belief, 
 that thought muft have a fubjecl:, and be the act 
 of fome thinking being : how every man believes 
 himfelf to be fomething diftinct from his ideas 
 and impreffions ; fomething which continues the 
 fame identical felf when all his ideas and im- 
 preflions are changed. It is impofiible to trace 
 the origin of this opinion in hiftory : for all lan- 
 guages have it interwoven in their original con- 
 ftruction. All nations have always believed it. 
 The conftitution of all laws and governments, as 
 well as the common tranfa&ions of life, fuppofe 
 it. 
 
 It is no lefs impoffible for any man to recol- 
 lect when Jie himfelf came by this notion : for, 
 as far back as we can remember, we were alrea- 
 dy in poffeffion of it, and as fuliy perfuaded of 
 our own exiftence, and the exiftence of other 
 things, as that one and one make two. It feems, 
 
 therefore, 
 
4 8 Of the HUMAN MIND. Chap. II. 
 therefore, that this opinion preceded all reafon- 
 ing, and experience, and inftruction ; and this is 
 the more probable, becaufe we could not get it 
 by any of thefe means. It appears then to be an 
 undeniable fact, that from-thought or fenfation,- 
 all mankind, conftantly and invariably, from the 
 firft dawning of reflection, do infer a power or 
 faculty of thinking, and a permanent being or 
 mind to which that faculty belongs ; and that we' 
 as invariably afcribe all the various kinds of fen- 
 fation and thought we are confcious of, to one 
 individual mind or felf. 
 
 But by what rules of logic we make thefe in- 
 ferences, it is impofiible to mow ; nay, it is im- 
 pofiible to fhow how our fenfations and thoughts 
 can give us the very notion and .conception ei- 
 ther of a mind or of a faculty. The faculty of 
 fmelling is fomething very different from the ac- 
 tual fenfation of fmelling ; for the faculty may 
 remain when we have no fenfation. And the 
 mind is no lefs different from the faculty ; for it 
 continues the fame individual being when that fa- 
 culty is loft. Yet this fenfation fuggefts to us 
 both a faculty and a mind ; and not only fuggefts 
 the notion of them, but creates a belief of their 
 exiftence -, although it is impofiible to difcover, 
 by reafon, any tie or connection between one 
 and the other. 
 
 What fhall we fay then ? Either thofe infe- 
 rences which we draw from our fenfations, name- 
 ly, the exiftence of a mind, and of powers or fa- 
 culties belonging to it, are prejudices of philofb- 
 
 phy 
 
Se&. 7. Of S M £ L L I N G. 49 
 
 phy or education, mere fidtionsof the mind, which 
 a wife man fhould throw off as he does the belief 
 of fairies , or they are judgments of nature, judg- 
 ments not got by comparing ideas, and percei- 
 ving agreements and difagreements, butimmedi- 1 
 ately infpired by our constitution. 
 
 If this laft is the Cafe, as 1 apprehend it is, it 
 will be impofiible to .fhake offthofeopinions, and 
 we muft yield to them at laft, though we strug- 
 gle hard to get rid of them. And if we could, 
 by a determined obftinacy, fhake off the princi- 
 ples of our nature, this is not to adt the philofo- 
 pher, but the fool or the madman. It is incum- 
 bent upon thofe who think that thefe are not na- 
 tural principles, to fhow, in the firft place, how 
 we can otherwife get the notion of a mind and 
 its faculties ; and then to fhow, how we come to 
 deceive ourfelves into the opinion that fenfation 
 Cannot be without a fentient being. 
 
 It is the received doctrine of philofophers, that 
 our notions of relations can only be got by com- 
 paring the related ideas : but, in the prefent cafe, 
 there feems to be an inftance to the contrary. It 
 is not by having firft: the notions of mind and 
 fenfation, and then comparing them together, 
 that we perceive the one to have the relation of 
 a fubject or fubftratum, and the other that of aa 
 act or operation : on the contrary, one of the 
 related things, to wit, fenfation, fuggefts to us 
 both the correlate and the relation. 
 
 I beg leave to make ufe of the word fuggefli- 
 
 on, becaufe I know not one more proper, to ex- 
 
 D prefa 
 
5 o OftheHUMAN MIND. Ch^ II. 
 prefs a power of the mind, which feems entirely 
 to have efcaped the notice of philofophers, and 
 to which we owe many of our fimpje notions 
 which are neither impreffions nor ideas, as well as 
 many original principles of belief. I /hall endea- 
 vour to illuftrate, by an example, what I under- 
 ftand by this word. We all know, that a certain 
 kind of found fqggefts immediately to the mind, 
 a coach paffing in the ftreet •, and not only pro- 
 duces the imagination, butthe belief, thata coach 
 is paffing. Yet there is here no comparing of 
 ideas, no perception of agreements or difagree- 
 ments, to produce this belief; nor is there the 
 leaft fimilitude between the found we hear, and 
 the coach we imagine and believe to be paffing. 
 It is true that this fuggeftion is not natural and 
 original ; it is the refult of experience and ha- 
 bit. But I think it appears, from, what hath been 
 faid, that there are naturaj fuggeftions ; particu- 
 larly, that fenfation fuggefts the notion of prefent 
 exiftence, and the belief that what we perceive, 
 or feel, does now exift ; that memory fuggefts 
 the notion of pad exiftence, and the belief that 
 what we remember did exift in time paft ; and 
 that our fenfations and thoughts do alfo fuggeft 
 the notion of a mind, and the belief of its exift- 
 ence, and of its relation to our thoughts. By a 
 like natural principle it is, that a beginning of 
 exiftence, or any change in nature, fuggefts to 
 us the notion of a caufe, and compels our belief 
 of its exiftence. And in like manner, as fhall be 
 {hewn when we come to theefenfe of touch, cer- 
 tain 
 
Sed. 7. Of S M E L L I N G. £1 
 
 tain fenfations of touch, by the conftitution of oup 
 nature, fuggeft to usextenfion, folidity, and mo*- 
 tion, which are nowife like to fenfations, although 
 they have been hitherto confounded with them. 
 
 SECT. VIII. 
 
 There is a quality or virtue in bodies, which we call 
 their fmell. How this is come fled in the imagi- 
 nation with the fenfation. 
 
 Wf E have confidered fmell as fignifying a fen- 
 fation, feeling, or irnpreffion upon the 
 mind ; and in this fenfe, it can only be in a mind, 
 or fentient being : but it is evident, that man- 
 
 [ kind give the name of fmell much more fre- 
 quently to fomething which they conceive to be 
 external, and to be a quality of body : they un- 
 derftand fomething by it which does not at all 
 infer a mind; and have not the leaft difficulty in 
 conceiving the air perfumed witharomaticodours 
 in the defarts of Arabia, or in fome uninhabited 
 ifland, where the human foot never trod. Every 
 fenfible day-labourer hath as clear a notion of 
 this, and as full a conviction of the poffibility of 
 it, as he hath of his own exiftence ; and can no 
 more doubt of the one than of the other. 
 
 j Suppofe that fuch a man meets with a modern 
 philofopher, and wants to be informed, what 
 fmell in plants is. The philofopher tells him, 
 that there is no fmell in plants, nor in any thing, 
 but in the mind ; that it is impofiible there can ' 
 D i be 
 
5 2 Ofthe HUMAN MIND. Chap. II. 
 
 be fmell but in a mind ; and that all this hath 
 been demonftrated by modern philofophy. The 
 plain man will, no doubt, be apt to think him 
 merry : but if he finds that he is ferious, his next 
 conclufion will be, that he is mad ; or that phi- 
 lofophy, like magic, puts men into a new world, 
 and gives them different faculties from common 
 men. And thus philofophy and common fenfe 
 are fet at variance. But who is to blame for it ? 
 In my opinion the philofopher is to blame. For 
 if he means by fmell, what the reft of mankind 
 moft commonly mean, he is certainly mad. Bat 
 if he puts a different meaning upon the word, 
 without oblerving it himlelf, or giving warning 
 to others ; he abufes language, and difgraces phi- 
 lofophy, without doing any fervice to truth : as 
 if a man fhould exchange the meaning of the 
 words daughter and cow, and then endeavour to 
 prove to his plain neighbour, that his cow is his 
 daughter, and his daughter his cow. 
 
 I believe there is not much more wifdom irt 
 many of thofe paradoxes of the ideal philofophy, 
 which to plain fenfible men appear to be palpa- 
 ble abfurdities, but with the adepts pafs for. pro- 
 found difcoveries. I refolve, for my own part, 
 always to pay a great regard to the dictates' of 
 common fenfe, and not to depart from them 
 without abfolute neceffity : and therefore I am 
 apt to think, that there is really fometfring in the 
 rofe or lily, which is by the vulgar called fmell, 
 and which continues to exift when it is not 
 fmelled,: and fhall proceed to inquire what this 
 
 13 
 
Seft. 8; OfSMELLING. 53 
 
 is ; how we come by the notion of it; and what 
 relation this quality or virtue of fmell hath to the 
 fenfation, which we have been obliged to call by 
 the fame name, for want of another. 
 
 Let us therefore fuppofe, as before, a perfon 
 beginning to exercife the fenfe of fmelling : a 
 little experience will difcover to him, that the 
 nofe is the organ of this fenfe, and that the air, 
 or fomething in the air, is a medium of it. And 
 finding by farther experience, that when a rofe 
 is near, he has a certain fenfation ; when it is re- 
 moved, the -fenfation is gone; he finds a connec- 
 tion in nature betwixt the rofe and this fenfation. 
 The rofe is confidered as a caufe, occafion, or an- 
 tecedent, of the fenfation ; the fenfation as an ef- 
 fect or confequent of the prefence of the rofe : 
 they are afibciated in the mind, and conftantly 
 found conjoined in the imagination. 
 
 But here it deferves our notice, that altho' 
 the fenfation may feem more clofely related to 
 the mind its fubjeft, or to the nofe its organ ; 
 yet neither of thefe connexions operate fo pow- 
 erfully upon the imagination, as its connexion 
 with the rofe its concomitant. The reafon of this 
 feems to be, that its connexion with the mind 
 is more general, and noway diftinguifheth it from 
 other fmells, or even from taftes, founds, and 
 other kinds of fcnfations. The relation it hath 
 to the organ, is likewife general, and doth not 
 diftinguifh it from other fmells > but the con- 
 nection it hath with the rofe is fpecial, and con- 
 ftant; by which means theyibecome almoft in- 
 D^ 'fcparable 
 
54 Of the H U M A N M I N D. Chap. II. 
 feparable in the imagination, in like manner as 
 thunder and lightning, freezing and cold. 
 
 SECT. IX. 
 
 tfbat there is a principle in human nature, front 
 which the notion of this, as well as all dtber 
 natural virtues or caufes, is derived. 
 
 I 
 
 N order to illuftrate further how we come to 
 conceive a quality or virtue in the rofe which 
 we call fmell, and what -this fmell is, it is pro- 
 per to obferve, that the mind begins very early 
 to thirft after principles, which may direct it in 
 the exertion of its powers. The fmell of a 
 rofe is a certain affection or feeling of the mind ; 
 and as it is not conftant, but comes and goes, we 
 want to know when and where we may expect 
 it, and are uneafy till we find fomething, which 
 being prefent, brings this feeling along with it, 
 and being removed, removes it. This, when 
 found, we call the caufe of it ; not in a ftrict and 
 philofpphical fenfe : as if xhe feeling were really 
 effected or produced by that caufe, but in a po- 
 pular fenfe : for the mind is fatisfied, if there is 
 a conftant conjunction between them ; and fuch 
 caufes are in reality nothing elfe but laws of na- 
 ture. Having found the fmell thus conftantly 
 conjoined with the rofe, the mind is at reft, with- 
 out inquiring whether this conjunction is owing 
 to a real efficiency or not ; that being a philofo^ 
 phical inquiry, which does not concern human 
 
 .»«*• 
 
Sect. 9. Of SMELLING. 55 
 
 life. But every difcovery of fuch a coriftant 
 conjunction is of real importance in life, and 
 makes a llrong impreffion upon the mind. 
 
 So ardently do we defire to find every thing 
 that happens within our obfervation, thus con- 
 nected with fomething elfe, as its caufe orocca- 
 fion, that we are apt to fancy connections upon 
 the flighteft grounds : and this weaknefs is mofl 
 remarkable in the ignorant, who know leaft of 
 the real connections eftabliflied in nature. A 
 man meets with an unlucky accident on a certain 
 day of the year; and knowing no other caufe 
 of his misfortune, he is apt to conceive fome- 
 thing unlucky in that day of the calendar; and 
 if he finds the fame connection hold a fecond 
 time-, is ftrongly confirmed 1 in his fuperftition. 
 I remember, many years ago, a white ox was 
 brought into this country, of fo enormous a fize, 
 that people eame many miles to fee him. There 
 happened, feme months after, an uncommon fa* 
 tality among women in child-bearing. Two 
 fuch uncommon events following one another^ 
 gave a fufpicion of their connection, and occa- 
 fioned a common opinion among the country- 
 people, that the white ox was the caufe of this 
 fatality. 
 
 However filly and ridiculous this opinion was, 
 it fprung from the fame root in human nature, on 
 which all natural philofophy grows ; namely, an 
 eager defire to find out connections in things, 
 and a natural, original, and unaccountable pro- 
 penfity to believe, that the connections which 
 D 4 we 
 
$6 Of the HUMAN MIND. Chap. II. 
 we have obferved in time paft, will continue in 
 time to come. Omens, portents, good and bad 
 luck, palmiftry, aftrology, all the numerous arts 
 of divination, and of interpreting dreams, falfe 
 hypothefes and fyftems, and true principles in 
 the philofophy of nature, are all built upon the 
 fame foundation in the human conftitution -, and 
 are diftinguifhed only according as we conclude 
 rafhjy from too few inftances, or cautiouflyfrom 
 3 fufficient induction. 
 
 As it is experience only that difcovers thefe 
 connections between natural caufes and their ef- 
 fects ; without inquiring further, we attribute to 
 the caufe fome vague and indiftinct notion of 
 powerorvirtueto produce the effect. Andinmany 
 cafes, the purpofes of life do not make it neceflary 
 to give diftinct names to the caufe and the effect. 
 Whence ithappens, that beingclofely connected in 
 the imagination, altho' very unlike to each other, 
 one name ferves for both ; and, in common dif- 
 courfe, is moft frequently applied to that which, 
 of the two, is moft the objedr. of our attention. 
 This occaGons an ambiguity in many words, 
 which having the fame caufes in all languages, is 
 common to all, and is apt to be overlooked even 
 by philofophers. Some inftances will ferve both 
 to illuftrate and confirm what we have faid. 
 
 Magnetifm fignifies both the tendency of the 
 iron towards the magnet, and the power of the 
 magnet to produce that tendency : and if it was 
 alked, whether' it is a quality of the iron or of 
 the magnet ? one would perhaps be puzzled at 
 
 firfti 
 
Sea. 9. Of SMELLING. 57 
 
 firftj but a little attention would difcover, that 
 we conceive a power or virtue in the magnet as 
 the caufe, and a motion in the iron as the effe<5t ; 
 and altho' thefe are things quite unlike, they are 
 ib united in the imagination, that we give the 
 common name of magnetifm to both. The fame 
 thing may be faid of gravitation^ which fome- 
 times fignifies the tendency of bodies towards the 
 earth, fbmetimes the attractive power of the 
 earth, which we conceive as the caufe of that 
 tendency. We may obferve the fame ambiguity 
 in fome of t Sir lfaac Newton's definitions; and 
 that even in words of his own making. In three 
 of his definitions, he explains very diftinctly 
 what he underftands by the abfolute quantity, 
 what by the accelerativc quantity, and what by 
 the motive quantity, of a centripetal force. In 
 the firft of thefe three definitions, centripetal 
 force is put for the caufe, which we conceive to 
 be fome power or virtue in the centre or central 
 body : in the two laft, the fame word is put for 
 the effect of this caufe, in producing velocity, or 
 in producing motion towards that centre. 
 
 Heat fignifies a fenfation, and cold a contrary 
 one. But heat likewife fignifies a quality or ftate 
 of bodies, which hath no contrary, but different 
 degrees. When a man feels the fame water hot 
 to one hand, and cold to the other, this gives 
 him occafion to diftinguifh between the feeling, 
 and the heat of the body •, and altho' he knows 
 that the fentations are contrary, he does not ima- 
 gincthat the body can have contrary qualities 
 
 at 
 
58 Of the HUMAN MIND. Chap. If. 
 
 at the fame time. And when he finds a different 
 tafte in the fame body in ficknefs and in health, 
 he is eafily convinced, that the quality in the bo- 
 dy called tafte is the fame as before, altho' the 
 fenfations he has from it are perhaps oppofite. 
 
 The vulgar are commonly charged by philofo- 
 phers, with the abfurdity of imagining the fmell 
 in the rofe to be fomething like to the fenfation 
 of fmelling: but I think, unjuftly; for they nei- 
 ther give the fame epithets to both, nor do they 
 reafon in the fame manner from them. What is 
 fmell in the rofe ? It is a quality or virtue of the 
 rofe, or of fomething proceeding from it, which 
 we perceive by the fenfe of fmelling ; and this is 
 all we know of the matter. But what is fmel- 
 ling ? It is an aft of the mind, but is never ima- 
 gined to be a quality of the mind. Again, the. 
 fenfation of fmelling is conceived to infer ne- 
 ceffarily a mind or fentient being -, but fmell in 
 the rofe infers no fuch thing. We fay, This bo- 
 dy fmells fweet, that ftinks ; but we do not fay, 
 This mind fmells fweet, and that ftinks. There- 
 fore fmell in the rofe, and the fenfation which it 
 caufes, are not conceived, even by the vulgar, 
 to be things of the fame kind, altho' they have 
 the fame name. 
 
 From what hath been faid, we may learn, 
 that the fmell of a rofe fignifies two things. Firft, 
 A fenfation, which can have no exiftence but 
 when it is perceived, and can only be in a fen- 
 tient being or mind. Secondly, It fignifies fome 
 power, quality, or virtue, in the rofe, or in efflu- 
 via 
 
St&.f. Of SMELLING. 59 
 
 via proceeding from it, which hath a permanent 
 exiftence, independent of the mind, and which 
 by the conftitution of nature, produce? the fen- 
 fation in us. By the original conftitution of our 
 nature, we are both led to believe, that there is 
 a permanent caufeof the fenfation, and prompt- 
 ed to feek after it; and experience determines 
 us to place it in the rofe. The names of all 
 fmells, taftes, founds, as well as heat and cold, 
 have a like ambiguity in all languages : but it de- 
 fences our attention, that thefe names are but 
 rarely, in common language, ufed to fignify the 
 fenfations; for the moft, part, they fignify the ex- 
 ternal qualities which are indicated by the fen- 
 fations. The caufe of which phenomenon I 
 take to be this. Our fenfations have very dif- 
 ferent degrees of ftrength. Some of them are 
 fo quick and lively, as to give us a great deal 
 either of pleafure or of uneafinefs : When this 
 is the cafe, we are compelled to attend to the 
 fenfation kfelf, and to make it an object of thought 
 and difcourfe ; we give it a name, which fignifies 
 nothing but the fenfation ; and in this cafe we 
 readily acknowledge, that the thing meant by 
 that name is in the mind only, and not in any 
 thing external* Such are the various kinds of 
 pain, ficknefs, and the fenfations of hunger and 
 other appetites. But where the fenfation is not 
 fo intefefting as to require to be made an object 
 of thought, our conftitution leads us to confider 
 it as a fign of fomething external, which hath a 
 conftanc conjunction with it; and having found 
 
 what 
 
6o Ofthe HUMAN MIND. Chap. II. 
 what it indicates, we give a name to that : the 
 fenfation, having no proper name, falls in as an 
 accefibry to the thing fignified by ir, and is con- 
 founded under the fame name. So that the name 
 may indeed be applied to the fenfition, but mod 
 properly and commonly is applied to the thing in- 
 dicated by that fenfation. The fenfations of fmell 
 tafte, found, and colour, are of infinitely more 
 importance as figns or indications, than they are 
 upon their own account; like the words of a 
 language, wherein we do not attend to the found, 
 but to the fenfe. 
 
 SECT. X. 
 
 Whether in fenfation the mind is aSlive or 
 faffive ? 
 
 *T< HERE is one inquiry remains, Whether 
 in fmelling, and in other fenfations, the 
 mind is acYive or pafiive ? This poffibly may 
 feem to be a queftion about words, or at leaft of 
 very fmall importance -, however, if it leads us 
 to attend more accurately to the operations of 
 our minds, than we are accuftomed to do, it is 
 upon that very account not altogether unprofit- 
 able. 1 think the opinion of modern philofo- 
 phers is, that in fenfation the mind is-altogether 
 paffive. And this undoubtedly is fo far true, 
 that we cannof raife any fenfation in our minds 
 by willing jt ; and, on the other hand, it feems 
 hardly poffible to avoid having the fenfation when 
 
 the 
 
Sett. 10. Of SMELLING. 61 
 
 the object is prefented. Yet it feems like wife to 
 be true, that in proportion as the attention is more 
 or lefs turned to a fenfation, or diverted from it, 
 that fenfation is more or lefs perceived and re- 
 membered. Every one knows, that very in- 
 tenfe pain may be diverted by a furprife, or by 
 any thing that entirely occupies the mind. When 
 we are engaged in earneft converfation, the clock 
 may ftrike by us without being heard; at l'eaft 
 we remember not the next moment that we did 
 hear it. The noife and tumult of a great tra- 
 ding city, is not heard by them who have lived 
 in it all their days ; but it ftuns thofe ftrangers 
 who, have lived in the peaceful retirement of the 
 country. Whether therefore there can be any 
 fenfation where the mind is purely paffive, I will 
 not fay •, but I think we are confcious of having 
 given fome.attention to every fenfation which we 
 remember, though ever fo recent. 
 
 No doubt, where the impulfe is ftrongand un- 
 common, it is as difficult to withhold attention, 
 as it is to forbear crying out in racking pain, or 
 ftarting in a fudden fright : but how far both 
 might be attained by ftrong refolution and prac- 
 tice, is not eafy to determine. So that, al- 
 though the Peripatetics had no good reafon to 
 fuppofe an active and a paffive intellect, fince at-' 
 tention may be well enough accounted an act of 
 the will ; yet I think they came nearer to the 
 truth, in holding the mind to be in fenfation 
 partly paffive and partly active, than the moderns, 
 in affirming it to be purely paffive. Senfation, 
 
 imagination, 
 
62 Of the HUMAN MIND. Chap. II. 
 
 imagination, memory, and judgment, have, by 
 the vulgar, in all ages, been confidered as afts of 
 the mind. The manner in which they are ex- 
 prefled in all languages, fhews this. When the 
 mind is much employed in them, we fay it is 
 very active ; whereas, if they were impreflions 
 only, as the ideal philofophy would lead us to 
 conceive, we ought in fuch a cafe rather to fay, 
 that the mind is very paflive: for I fuppofe no 
 man would attribute great activity to the paper 
 I write upon, becaufe it receives variety of cha- 
 racters. 
 
 The relation which the fenfation of fmell bears 
 to the memory and imagination of it, and to a 
 mind or fubject, is common to all our fenfations, 
 and indeed to all the operations of the mind : 
 the relation it bears to the will, is common to 
 it with all the powers of underftanding : and 
 the relation it bears to that quality or virtue of 
 bodies which it indicates, is common to it with 
 the fenfations of tafte, hearing, colour, heat, 
 and cold : fo that what hath been faid of this 
 fenfe, may eafily be applied to feveral of our fen- 
 fes, and to other operations of the mind ; and 
 this, I hope, will apologize for our infifting fo 
 long upon it. 
 
 CHAP. 
 
i 63 •] 
 
 CHAP. III. 
 
 Of TASTING. 
 
 AG R E A T part of what hath been faid of 
 the fehfe of fmelling, is fo eafily applied 
 to thofe of tailing and hearing, that we fhall 
 leave the application entirely to the reader's judg- 
 ment, and fave ourfelves the trouble of a tedious 
 repetition. 
 
 It is probable that every thing that affedts the 
 tafte, is in fome degree foluble in the faliva. It 
 is not conceivable how any thing mould enter 
 readily, and of its own accord, as it were, into 
 the pores of the tongue, palate, and fauces, un- 
 lefs it had Fome chymical affinity to that liquor 
 with which thefe pores are always replete. It is 
 therefore an admirable contrivance of nature, that 
 the organs of tafte mould always be moift with a 
 liquor which is fo univerfal a menftruum, and 
 which deferves to be examined more than it hath 
 been hitherto,, both in that capacity, and as a 
 medical unguent. Nature teaches dogs, and 
 other animals, to ufe it in this laft way ; and its 
 fubferviency both to tafte and digeftion, Ihews 
 its efficacy in the former. 
 
 It is with manifeft defign and propriety, that 
 
 the organ of this fenfe guards the entrance of the 
 
 alimentary canal, as that of fmell, the entrance 
 
 of the canal for refpiration. And frpm thefe or- 
 
 7 gans 
 
64 Of the H U M A N M I N D. Chap. If. 
 gans being placed in fuch manner, that every 
 thing that enters into the ftomach muft undergo 
 the fcrutiny of both fenfes, it is plain, that they 
 were intended by nature to diftinguifh wholefome 
 food from that which is noxious. The brutes 
 have no other means of chufing their food ; nor 
 would mankind, in the favage ftate. And it is 
 very probable, that the fmell and tafte, no way 
 vitiated by luxury or bad habits, would rarely, 
 if ever, lead us to a wrong choice of food among 
 the productions of nature-, akho' the artificial 
 compofnionsof a refined and luxurious cookery, or 
 of chymiftry and pharmacy, may often impofe 
 upon both, and produce things agreeable to the 
 tafte and fmell, which are noxious to health. And 
 it is probable, that both fmell and tafte are vitia- 
 ted, and rendered lefs fit to perform their natural 
 offices, by the unnatural kind of life men com- 
 monly lead in fociety. 
 
 Thefe fenfes are likewife of great ufe to di- 
 ftinguilh bodies that cannot be diftinguiftied by 
 our other fenfes, and to difcern the changes 
 which the fame body undergoes, which in many 
 cafes are fooner perceived by tafte and fmell than 
 by any other means. How many things are there 
 in the market, the eating-houfe, and the tavern, 
 as well as in the apothecary and chymift's (hops, 
 which are known to be what they are given out 
 to be, and are perceived to be good or bad in 
 their kind, only by tafte or fmell ? And how far 
 our judgment of things, by means of our fenfes, 
 might be improved by accurate attention to the 
 
 fmall 
 
Of TASTING. 65 
 
 fmall differences oftafte and fmell, and other fen- 
 fible qualities, is not eafy to determine; Sir 
 Ifaac Newton, by a noble effort of his great geni- 
 us, attempted, from the colour of opaque bodies, 
 to difcover the magnitude of the minute pellucid 
 parts, of which they are compounded : and who 
 knows what new lights natural philofophy may 
 yet receive from other fecondary qualities duly 
 examined ? 
 
 Some taftes and fmells Simulate the nerves* 
 and raife the fpirits : but fuch an artificial eleva- 
 tion of the fpirits is, by the laws of nature, fol- 
 lowed by a depreffion, which can only be relie- 
 ved by time, or by the repeated ufe of the like 
 Jlimulus. By the ufe of fuch things we create 
 an appetite for them, which very much refem- 
 bles, and hath all the force of a natural one. It 
 is in this manner that men acquire an appetite 
 forfnuff, tobacco, ftrong liquors, laudanum, and 
 the like. 
 
 Nature indeed feems ftudioufly to have fefc 
 bounds to the pleafures and pains we have by 
 thefe two fenfes, and to have confined them with- 
 in very narrow limits, that we might not place 
 any part of our happinefs in them ; there being 
 hardly any fmell or tafte fo d'fagreeable that ufe 
 will not make it tolerable, and at laft perhaps 
 agreeable, nor any lb agreeable as not to lofe its 
 relifh by conftant ufe. Neither is there any 
 pleafore or pain of thefe fenfes which is not in- 
 troduced, or followed, by fome degree of irs 
 contrary, which nearly balances it. So that 
 E we 
 
66 OftheHUMAN MIND. Chap. HI. 
 
 we may here apply the beautiful allegory of the 
 divine Socrates •, That altho' plead; re and pain 
 are contrary in their nature, and their faces look 
 different ways, yet Jupiter hath tied them {o to- 
 gether, that he that lays hold of the one, draws 
 the other along with it. 
 
 As there is a great variety of fmells, feeming- 
 ly fimple and uncompounded, not only altoge- 
 ther unlike, but fome of them contrary to 
 others -, and as the fame thing may be faid of 
 taftes •, it would feem that one tafte is not lefs 
 different from another than it is from a fmell : 
 and therefore it may be a queftion, how all 
 fmells come to be confidered as one genus, and 
 all taftes as another ? What is the generical di- 
 ftinclion ? Is it only that the nofe is the organ 
 of the one and the palate of the other ? or r 
 abftra&ing from the organ, is there not in the 
 fenfations themfeives fomething common to 
 fmells, and fomething elfe common to taftes, 
 whereby the one is diftinguifhed from the other ? 
 It feems moft probable that the latter is the cafe; 
 and that under the appearance of the greateft 
 fimplicity, there is ftill in thefe fenfations fome- 
 thing of compofition. 
 
 If one confiders the matter abftractly, it 
 would feem, that a number of fenfations, or in- 
 deed of any other individual things, which are 
 perfect ly fimple and uncompounded, are incapa- 
 ble of being reduced into genera and /pedes ; bc- 
 caufe individuals which belong to a fpecies, muft 
 have fomething peculiar to each, by which thev 
 
 3^2 
 
Of TASTING. 67 
 
 are diftinguifhed, and fomething common to the 
 whole fpecies. And the fame may be faid of 
 fpecies which belong to one genus. And whe- 
 ther this does not imply fome kind of compofi- 
 tion, we fhall leave to metaphyficians to deter- 
 mine. „ 
 
 The fenfations both of fmell and tafte do un- 
 doubtedly admit of an immenfe variety of modi- 
 fications, which no language can exprefs. If a 
 man was tdexamine five hundred different wines, 
 he would hardly find two of them that had pre- 
 cifely the fame tafte : the fame thing holds in 
 cheefe, and in many other things. Yet of , five 
 hundred different taftes in cheefe or wine, we 
 can hardly defcribe twenty, fo as to give a dif- 
 tindt notion of them to one who had not tafted 
 them. 
 
 Dr. Nehemiah Grew, a moft judicious and la- 
 borious naturalift, in a difcourfe read before the 
 Royal Society, anno 1675, hath endeavoured to 
 fhow, that there are at leaft fixteen different fim- 
 ple taftes,, which he enumerates. How many 
 compounded ones may be made out of all the va- 
 rious combinations of two, three, four, or more 
 of thefe fimple ones, they who are acquainted with 
 the theory of combinations will eafily perceive. 
 All thefe have various degrees of intenfcnefs and 
 weaknefs. Many of them have other varieties : 
 in fome the tafte is more quickly perceived upon 
 the application of the fapid body, in others more 
 flowly ; in fome the fenfation is more permanent, 
 in others more transient ; in fome it feems to un- 
 E 2 dukte, 
 
68 OftheHUMANMIND.Chap.il. 
 dulate, or return after certain intervals, in others 
 it is conftant : the various parts of the organ, as 
 the lips, the tip of the tongue, the root of the 
 tongue, the fauces, the uvula, and the throat, 
 are fome of them chiefly affected by one fapid bo- 
 dy, and others by another. All thefe, and other 
 varieties of taftes, that accurate writer illuftrates 
 by a number of examples. Nor is it to be doubt- 
 ed, but fmells, if examined with the fame ac- 
 curacy, would appear to have as great variety. 
 
 CHAP. 
 
[ €9 J. 
 CHAP. IV. 
 
 Of HEARING. 
 
 SECT. I. 
 
 Variety of founds. Their place and dijlance learn- 
 ed by cujlom, without reafoning. 
 
 SOUNDS have probably no lefs variety 
 of modifications, than either taftes or 
 odours. For, firft, founds differ in tone. 
 The ear is capable of perceiving fpur or five hun- 
 dred variations of tone in found, and probably as 
 many different degrees of ftrength ; by combi- 
 ning thefe, we have above twenty thoufand fim- 
 ple founds that differ either in tone or ftrength 
 fuppofing every tone to be perfect. But it is 
 to be oblerved, that to make a perfect tone, a 
 great many undulations of elaftic air are re- 
 quired, which muft all be of equal duration and 
 extent, and follow one another with perfect re- 
 gularity ; and each undulation muft be made up 
 of the advance and recoil of innumerable parti- 
 cles of elaftic air, whofe motions are all uniform 
 in direction, force, and time. Hence we may 
 eafily conceive a prodigious variety in the fame 
 tone, arifing from irregularities of it, occafioned 
 by the conftitution, figure, fituation, or manner 
 oi ftriking the fonorous body : from the confti- 
 tutiqn of the elaftic medium, or its being difturb- 
 L % ed 
 
70 Of the H U M A N M I N D. Chap. IV. 
 ed by other motions •, and from the conftitution 
 of the ear itfclf, upon which the imprefilon is 
 made. 
 
 A flute, a violin, a hautboy, and a French 
 horn, may all found the fame tone, and be eafily 
 diftinguiihable. Nay, if twenty human voices 
 found the fame note, and with equal ftrength, 
 there will ft ill be fome difference. The fame 
 voice, while it retains its proper diftinflions, may 
 yet be varied many ways, by ficknefs or health, 
 youth or age, leannefs or fatnefs, good or bad 
 humour, The fame words fpoken by foreigners 
 and natives, nay, by perfons of different provin- 
 ces of the fame nation, , may be diftinguifhed. 
 Such an immenfe variety of fenfatio'ns of fmell, 
 tafte,, and found, furely was not given us in vain. 
 They are figns, by which we know and diftin- 
 guifh things without us -, and it was fit that the 
 variety of the figns mould, in fome degree cor- 
 refpond with the variety of the things fignified 
 by them. 
 
 it feems to be by cuftom, that we learn to dif- 
 tinguim both the place of things, and their na- 
 ture, by means of their found. That fuch a 
 noife is in the ftreet, fuch another in the room 
 above me - ? that this is a knock at my door, that 
 a perfon walking up ftairs, is probably learnt by 
 experience. I remember, that once lying a-bed, 
 and having been put into a fright, I heard my own 
 heart beat •, but I took it to be one knocking at 
 the door, and arofe and opened the door oftener 
 than once, before I difcovered that the found was 
 
 in 
 
Seft. i. Of HEARING. ;i 
 
 in my own breaft. It is probable, that previ- 
 ous to all experience, we fhould as little know, 
 whether a found came from the right or. left, 
 from above or below, from a great or a fmall di- 
 ftance, as we fhould know whether it was the 
 found of a drum, or a bell, or a cart. Nature 
 is frugal in her operations, and will not be at the 
 expence of a particular inftincT:, to give us that 
 knowledge which experience will foon produce, 
 by means of a general principle of human na- 
 ture. 
 
 For a little experience, by the conftitution of 
 human nature, tiestogether, not only in our ima- 
 gination, but in our belief, thofe things which 
 were in their nature unconnected. When I hear 
 a certain found, I conclude immediately, without 
 reafonihg, that a coach paries by. There are 
 no premifes from which this conclufion isinferred 
 by any rules of logic. It is" the effect of a prin- 
 ciple of our nature, common to us with the 
 
 brutes. 
 
 Akho' it is by hearing, that we are . capable 
 
 of the perceptions of harmony and melody, and 
 of all the charms of mufic j yet it would feem, 
 that thefe require a higher faculty, which we 
 call a mufical ear. This feems to be in very dif- 
 ferent degrees, in thofe who have the bare facul- 
 ty of hearing equally perfect: ; and therefore 
 ought not to ht claffed with the external fenfes, 
 but in a higher order. , 
 
 E 4 SECT. 
 
72 Of the HUMAN MIND. Chap. IV. 
 
 SECT. II, 
 
 Of natural language. 
 
 N E of the nobleft purpofes of found un- 
 doubtedly is language-, without which man- 
 kind would hardly be able to attain any degree 
 of improvement above the brutes. Language 
 is commonly confidered as purely an invention of 
 men, who by nature are no lei's mute than the 
 brutes, but having a fuperior degree of invention 
 and reafon, have been able to contrive artificial 
 figns of their thoughts and purpofes, and to efta- 
 blifh them by common conient. But the origin 
 of language deferves to be more carefully inqui- 
 red into, not only as this inquiry may be of im- 
 portance for the improvement of language, but 
 as it is related to the prefent fubjecr, and tends 
 to lay open lome of the firft principles of human 
 nature. I mail therefore offer fome thoughts 
 upon this fubject. 
 
 By language I underftand all thofe figns which 
 mankind ufe in order to communicate to others 
 their thoughts and intentions, their purpofes and 
 defires. And fiich figns may be conceived to be 
 of two kinds : Firft, kich as? have no meaning, 
 but what is affixed to them by compacl or agree- 
 ment among thofe wi;o ufe them -, theie are arti- 
 ficial figns : Secondly, fuch as, previous to all 
 compadt or agreement, have a meaning which 
 every man underftands by the principles of his 
 
 nature. 
 
Sed. 2. Of HEARING. 73 
 
 nature. Language, fo far as it confifts of arti- 
 ficial figns, may be called artificial; fo far as it 
 confifts of natural figns, I call it natural. 
 
 Having premifed thefe definitions, I think it 
 is demonstrable, that if mankind had not a natu- 
 ral language, they could never have invented an 
 artificial one by their reafon and ingenuity. For 
 all artificial language fuppofes fome compact or 
 agreement to affix a certain meaning to certain 
 figns; therefore there muft be compacts or agree- 
 ments before the ufe of artificial figns ; but there 
 can be no compact or agreement without figns, 
 nor without language ; and therefore there muft 
 be a natural language before any artificial lan- 
 guage can be invented : Which was to be demon- 
 strated. 
 
 Had language in general been a human inven- 
 tion, as much as writing or printing, we ftiould 
 find whole nations as mute as the brutes. Indeed 
 even the brutes have fome natural figns by which 
 they exprefs their own thoughts, affectiom, 
 and defires, and underftand thofe of others. A 
 chick, as foon as hatched, underftands the dif- 
 ferent founds whereby its dam calls it to food, 
 or gives the alarm of danger. A dog or a horfe 
 underftands, by nature, when the human voice 
 careffes, and when it threatens him. But brutes, 
 as far as we know, have no notion of conn acts 
 or covenants, or of moral obligation to perform 
 them. If nature had given them thefe notions, 
 fhe would probably have given them natural 
 figns to expreis them. And where nature has 
 
 denied 
 
74 Ofthe HUMAN MIND. Chap. IV. 
 denied thefe notions, it is as impoffible to acquire 
 them by art, as it is for a blind man to acquire 
 the notion of colours. Some brutes are feniible 
 of honour or difgrace ; they have refentment 
 and gratitude; but none of them, as far as we 
 know, can make a promife, or plight their faith, 
 having; no fuch notions from their conftitution. 
 And if mankind had not thefe notions by nature, 
 and natural figns to exprefs them by, with all 
 their* wit and ingenuity they could never have 
 invented language. 
 
 The elements of this natural language of man- 
 kind, or the figns that are naturally exprefiive 
 of our thoughts, may, I think, be reduced to 
 thefe three kinds ; modulations of the voice, 
 geftures, and features. By means of thefe,' two 
 favages who have no common artificial language, 
 can converfe together; can communicate tK j .ir 
 thoughts in fome tolerable manner ; can afk and 
 refufe-, affirm and deny, threaten and fupplicate ; 
 can traffic, enter into covenants, and plight their 
 faith. This might be confirmed by historical 
 facl:s of undoubted credit, if it were neceffary. 
 
 Mankind having thus a common language by 
 nature, tho' a fcanty one, adapted only to the 
 neceffities of nature, there is no great ingenuity 
 required in improving it by the addition of arti- 
 ficial figns, to fupply the deficiency of the natu- 
 ral. Thefe artificial figns muft multiply with 
 the arts of life, and the improvements of know- 
 ledge. The articulations of the voice, feem to 
 be, of all figns, the moil proper for artificial 
 
 language ; 
 
Sect, a. Of H E A R I N G. 75 
 
 language; and as mankind have univerfally 
 ufed them for that purpofe, we may rea- 
 fonably judge that nature intended them for it. 
 But nature probably does not intend that we 
 Ihould lay afide the ufe of the natural figns ; it is 
 enough that we fupply their defects by artificial 
 ones. A man thatrides always in a chariot, by 
 degrees lofes the ufe of his leg's ; and one who 
 ufes arcificial figns only^ lofes both the knowledge 
 and ufe of the natural. Dumb people retain 
 much more of the natural language than others, 
 becaufe neceffity obliges them to ufe it. And 
 for the fame reafon, favages have much more of 
 it than civilized nations. It is by natural figns 
 chiefly that we give force and energy to lan- 
 guage ; and the lefs language has of them, it is 
 the lefs expreffive and perfuafive. Thus, writing 
 is lefs expreffive than reading, and reading lefs 
 expreffive than fpeaking without book ; fpeaking 
 without the proper and natural modulations, 
 force, and variations of the voice, is a frigid 
 and dead language, compared with that which 
 . is attended with them ; it is ftill more expreffive 
 when we add the language of the eyes and fea- 
 tures; and is then only in its perfect and natural 
 ftate, and attended with its proper energy, when 
 (to all thefe we fuperadd the force of action, 
 
 Where fpeech is natural, it will be an exer- 
 cifc, not of the voice and lungs only, but of all 
 the mufcles of the body; like that of dumb 
 people and favages, whofe language, as it has 
 
 more 
 
7 6 Of the HUMAN MIND. Chap. IV. 
 more of nature, is more expreffive, and is more 
 eafily learned. 
 
 Is it not pity that the refinements of a civi- 
 lized life, inftead of fupplying the defects of na- 
 tural language, fliould root it out, and plant in 
 its ftead dull and lifejefs articulations of unmean- 
 ing' founds, or the fcrawling of infignificant cha- 
 racters ? The perfection o' language is common- 
 ; ly thought to be, to exprefs human thoughts and 
 fentiments diftin&ly by thefe dull figns •, but if 
 this is the perfection of artificial language, it is 
 furely the corruption of the natural. 
 
 Artificial figns fignify, but they do not ex- 
 prefs •, they fpeak to the underftanding, as alge- 
 braical characters may do, but the paffions, the 
 affections, and the will, hear them not : diefe 
 continue dormant and inactive, till we fpeak to 
 them in the language of nature, to which they 
 are all attention and obedience. 
 
 It were eafy to fbow, that the fine arts of the 
 mufician, the painter, the actor, and the orator, 
 fo far as they are expreffive ; aitho' the know- 
 ledge of them requires in us a delicate tafte, a 
 nice judgment, and much ftudy and practice; 
 yet they are nothing elfe but the language of 
 nature, which we brought into the world with 
 us, but have unlearned by difufe, and fo find the 
 greateft difficulty in recovering it. 
 
 Abolifh the ufe of articulate founds and wri- 
 ting among mankind for a century, and every 
 ' man would be a painter, an actor, and an orator. 
 We mean not to affirm that fuch an expedient is 
 
 practicable ; 
 
Seft. 2. Of HEARING. 77 
 
 practicable ; or, if it were, that the advantage 
 would counterbalance thelofs ; 'but that, as men 
 are led by nature and neceffity to converfe to- 
 gether, they wi\l ufe every mean in their power 
 to make themfelves underftood ; and whe/e they 
 cannot do this by artificial figns, they will do it, 
 as far as poffible, by natural ones : and he that 
 underftands perfectly the ufe of natural figns, 
 muft be the beft judge in all the exprefiive atts. 
 
 CHAP. 
 
G H A P. V. 
 
 Of TOUCH. 
 
 S E C T. I. 
 
 Of heat and cold. 
 
 TH E fenfes which we have hitherto con- 
 fidered, are very fimple and uniform, 
 each of them exhibiting only one kind of fenfa- 
 tion, and thereby indicating only one quality of 
 bodies. By the ear we perceive founds, and no- 
 thing elfe •, by the palate, taftes ; and by the 
 nofe, odours : Thefe qualities are all likewife of 
 one order, being all fecondary qualities : Where- 
 as by touch we perceive not one quality only, 
 but many, and thofe of. very different kinds. 
 The chief of them are heat and cold, hardnefs 
 and foftnefs, roughnefs and fmoothnefs, figure, 
 folidity, motion, and extenfion. "We mall con- 
 fider thefe in order. 
 
 As to heat and cold, it will eafily be allowed 
 that they are fecondary qualities, of the fame or- 
 der with fmell, tafte, and found. And, there- 
 fore, what hath been already faid of fmeil, is 
 eafily applicable to them ; that is, that the words 
 heat and cold have each of them two fignifica- 
 tions ; they fometimes fignify certain feniations 
 of the mind, which can have no exiftence when 
 they are not felt, nor can exift any where but 
 
 in 
 
Sea. i. Of TOUCH. 79 
 
 in a mind or fentient being ; but more frequent- 
 ly they fignify a quality in bodies, which, by 
 the laws of nature, occafions the fenfations of 
 heat and cold in us : A quality which, tho' con- 
 nected by cuftom fo clofely with the fenfation, 
 that we cannot without difficulty feparate them •, 
 yet hath not the leaft refemblance to it, and 
 may continue to exift when there is no fenfation 
 at all. 
 
 The fenfations of heat and cold are perfe&ly 
 known; for they neither are, nor can be, any 
 thing elfe than what we feel them to be ; but 
 the qualities in bodies which we call heat and cold, 
 are unknown. They are only conceived by us, 
 as unknown caufes or occafions of the fenfations 
 to which we give the fame names. But though 
 common fenfe fays nothing of .the nature of thefe 
 qualities, it plainly dictates the exiftence of them ; 
 and to deny tharthere can be heat and cold when 
 they are not felt, is an abfurdity too grofs to 
 merit confutation. For what could be more ab- 
 furd, than to fay, that the thermometer cannot 
 rife or fall unlefs fome perfon be prefent, or that 
 the coafl: of Guinea would be as cold as Nova 
 Zembla, if it had no inhabitants ? 
 
 It is the bufinefs of philofophers to investigate, 
 by proper experiments and induction, what heat 
 and cold are in bodies. And whether they make 
 best a particular element diffufed through nature, 
 and accumulated in the heated body, or whether 
 they make it a certain vibration of the parts of 
 the heated body j whether they determine that 
 2 heat 
 
80 Of the H U M A N M I N D. Chap. V. 
 heat and cold are contrary qualities, as the fen- 
 fations undoubtedly are contrary, or that heat 
 only is a quality, and cold its privation ; thefe 
 queftions are within the province of philofophy ; 
 for common fenfe fays nothing on the one fide or 
 the other. 
 
 But whatever be the nature of that quality in 
 bodies which we call heat, we certainly know 
 this, that it cannot in the leaft refemble the fen- 
 fation of heat. It is no lefs abfurd to fuppofe a 
 likenefs between the fenfation and the quality, 
 than it would be to fuppofe, that the pain of the 
 gout refembles a fquare or a triangle. The 
 fimpleft man that hath common fenfe, does not 
 imagine the fenfation of heat, or any thing that 
 refembles that fenfation, to be in the fire. He on- 
 ly imagines, that there is fomething in the fire, 
 which makes him and other fentient beings feel 
 heat. Yet as the name of heat, in common lan- 
 guage, more frequently and more properly fig- 
 nifies this unknown fomething in the fire, than 
 the fenfation occafioned by it, he juftly laughs at 
 the philofopher, who denies that there is any 
 heat in the fire, and thinks that he fpeaks con- 
 trary to common fenfe. 
 
 SECT. 
 
Seft. 2. Of TOUCH. Si 
 
 S EC T. II. 
 
 Of hardnefs and foft nefs. 
 
 T ET us next confider hardnefs and-foftnefs $ 
 by which words we always underftandireal 
 properties or qualities of bodies, of which we 
 have a diftindt conception. 
 
 When the parts of a body adhere fo firmly 
 that it cannot eafily be made to change its figure, 
 we call it hard; when its parts are eafily difpla- 
 ced, we call it foft. This is the notion which all 
 mankind have of hardnefs and foftnefs : they are 
 neither fenfations, nor like any fenfation ; they 
 were real qualities before they were perceived by 
 touch, .and continue to be fo when they are not 
 perceived : for if any man will affirm, that dia- 
 monds were not hard "till they were handled, who 
 would reafon with him ? 
 
 There is, no doubt, a fenfation by which we 
 perceive a body to be hard or foft. This fenfa- 
 tion of hardnefs may eafily be had, by prefiing 
 one's hand againft the table, and attending to 
 the feeling that enfues, fetting afide, as much as 
 poffible, all thought of the table and its qualities, 
 or of any external thing. But it is one thing to 
 have the fenfation, and another to attend to it, 
 and make it a diftindt object of reflection. The 
 firft is very eafy ? the laft, in molt cafes, ex- 
 tremely difficult. 
 
 F We 
 
82 OftheHUMAN MIND. Chap. V. 
 
 We are fo accuftomed to ufe the fenfaticn as 
 a fign, and to pafs immediately to the hardnefs 
 fignified, that, as far as appears, it was never 
 made an obje£t of thought, either by the vulgar 
 or by philofophers ; nor has it a name in any 
 language. There is no fenfation more diftinft, or 
 more frequent ; yet it is never attended to, but 
 paffes through the mind inftantaneoufly, and ferves 
 only to introduce that quality in bodies, which, 
 by a law of our conftitution, it fuggefts. 
 
 There are indeed fome cafes, wherein it is no 
 difficult matter to attend to the fenfation occafi- 
 oned by the hardnefs of a body ; for inftance, 
 when it is fo violent as to occafion considerable 
 pain : then nature calls upon us to attend to it, 
 and then we acknowledge, that it is a mere fen- 
 fation, and can only be in a fentient being. If a 
 man runs his head with violence againft a pillar, 
 I appeal to him, whether the pain he feels refem- 
 bles the hardnefs of the ftone ; or if he can con- 
 ceive any thing like what he feels, to be in an 
 inanimate piece of matter. 
 
 The attention of the mind is here entirely 
 turned towards the painful feeling ; and, tofpeak 
 in the common language of mankind, he feels no- 
 thing in the ftone, but feels a violent pain in his 
 head. It is quite otherwife when he leans his 
 head gently againft the pillar ; for then he will 
 tell you that he feels nothing in his head, but 
 feels hardnefs in the ftone. Hath he not a fen- 
 fation in this cafe as well as in the other ? Un- 
 doubtedly he hath : but it is a fenfation which 
 
 nature 
 
Sect. «. Of T O U C M. 83 
 
 nature intended only as a fign of fomethirig in 
 the ftone; and, accordingly, he inftantly fixes 
 his attention upon the thing fignified ; and can- 
 not, without great difficulty, attend fo much to 
 the fenfation, as to be perfuaded that there is 
 any fuch thing, diftinft from the hardnefs it fig- 
 nifies. 
 
 But however difficult it may be to attend to 
 this fugitive fenfation, to ftop its rapid progrefs, 
 and to disjoin it from the external quality of 
 hardnefs, in whofe fhadow it is apt immediately 
 to hide itfelf ; this is what a philofopher by pains 
 and practice muft attain, otherwife it will be im- 
 poffible for him to reafon juftly upon this fub- 
 ject, or even to underftand what is here advanced. 
 For the laft appeal, in fubjefts of this nature, 
 muft be to what a man feels and perceives in his 
 own mind. 
 
 It is indeed flrange, that a fenfation which we 
 have every time we feel a body hard, and which, 
 confequently, we can command as often, and con- 
 tinue as long as we pleafe, a fenfation as diftinct 
 and determinate as any other, (hould yet be fo 
 much unknown, as never to have been made an 
 object of thought and refleftion, nor to have 
 been honoured with a name in any language ; 
 that philofophers, as well as the vulgar, fhould 
 have entirely overlooked it, or confounded it 
 with that quality of bodies which we call hard- 
 nefs, to which it hath not the leaft fimilitude. 
 May we not hence conclude, That the know- 
 ledge of the human faculties is but in its infan- 
 F 2 cy? 
 
84 Of the HUMAN MIND. Chap.V. 
 cy ? That we have not yet learned to attend to 
 thofe operations of the mind, of which we are 
 confcious every hour of our lives ? That there 
 are habits of inattention acquired very early, 
 which are as hard to be overcome as other ha- 
 bits ? For I think it is probable, that the novel- 
 ty of this fenfation will procure fome attention to 
 it in children at firft-, but being in nowife inte- 
 refting in itfelf, as foon as it becomes familiar, i£ 
 is overlooked, and the attention turned folely to 
 that which it fignifies. Thus, when one is learn- 
 ing a language, he attends to the founds ; but 
 when he is mafter of ir, he attends only to the 
 fenfe of what he would exprefs. If this is the 
 cafe, we muft become as little children again, if 
 we will be philofophers :' we muft overcome this 
 habit of inattention which has been gathering 
 ftrength ever fince we began to think -, a habit, 
 the ufcfulnefs of which, in common life, atones 
 for the difficulty it creates to the philofopher in 
 difcovering the firft principles of the human mind. 
 The firm cohefion of the parts of a body, is 
 no more like that fenfation by which I perceive 
 it to be hard, than the vibration of a fonorous 
 body is like the found I hear : nor can I poffibly 
 perceive, by my reafon, any connexion between 
 the one and the other. No man can give a rea- 
 fon, why the vibration of a body might not have 
 given the fenfation of fmelling, and the effluvia 
 of bodies affected our hearing, if it had fo plealed 
 , our Maker. In like manner, no man can give a 
 reafon, why the fenfations of fmell, or tafte, or 
 
 found, 
 
Sed. 2. Of TOUCH. 8 5 
 
 found, might not have indicated hardnefs, as well 
 as that fenfaiion, which, by our constitution, does 
 indicate it. Indeed no man can conceive any fen- 
 fation to refemble any known quality of bodies. 
 Nor can any man mow, by any good argument, 
 that all our fenfations might not have been as 
 they are, though no body, nor quality of body, 
 had ever exifted. 
 
 Here then is a phenomenon of human nature, 
 which comes to be relblved. Hardnefs of bodies 
 is a thing that we conceive as diftinclly, and be- 
 lieve as firmly, as any thing in nature. We have 
 no way of coming at this conception and belief, 
 but by means of a certain fenfation of touch, to 
 which hardnefs hath not the leaft fimilitude ; nor 
 can we, by any rules of reafoning, infer the one 
 from the other. The queftion is, How we come 
 by this conception and belief ? 
 
 Firft, as to the conception : Shall we call it 
 an idea of fenfation, or of refledion ? The laft 
 will not be affirmed ; and as little can the firft, 
 unlefs we will call, that an idea of fenfation, which 
 hath no refemblance to any fenfation. So that 
 the origin of this idea of hardnefs, one of the 
 raoft common and moft diftindT: we have, is not 
 to be found in all our fyftems of the mind : not 
 even in thofe which have fo copioufly endea- 
 voured to deduce all our notions from fenfation 
 and reflection. 
 
 But, fecondly, fuppofing we have got the con- 
 ception of hardnefs, how come we by the belief 
 of it? Is it felf-evident, from comparing the 
 F 3 ideas, 
 
Z6 Of the HUMAN MIND. Chap. V. 
 ideas, that fuch a fenfation could not be felt, un- 
 lefs fuch a quality of bodies exifted ? No. Can 
 it be proved by probable or certain arguments ? 
 No, it cannot, Have we got this belief then by 
 tradition, by education, or by experience ? No, 
 it is not got in any of thefe ways. Shall we then 
 throw off this belief, as having no foundation in 
 reafon ? Alas ! it is not in our power •, it tri- 
 umphs over reafon, and laughs at all the argu- 
 ments of a philofopher. Even the author of the 
 Treatife of human nature^ though he faw no rea- 
 fon for this belief, but many againft it, could 
 hardly conquer it in his fpeculative and folitary 
 moments ; at other times he fairly yielded to ir, 
 and confeffes that he found himfelf under a ne- 
 ceffity to do fo. 
 
 What lhall we fay then of this conception, 
 and this belief, which are fo unaccountable and 
 untraceable ? I fee nothing left, but to conclude, 
 that, by an original principle of our conftitution, 
 a certain fenfation of touch both fuggefts to the 
 mind the conception of hardnefs, and creates the 
 belief of it : or, in other words, that this fenfa- 
 tion is a natural fign of hardnefs. And this J 
 jhall endeavour more fully to explain, 
 
 SECT. 
 
Seft. 3. OfTOUCH. 87 
 
 SECT. III. 
 
 Of natural Jigns. 
 
 A S in artificial figns there is often neither fi- 
 militude between the fign and thing fig- 
 nified, nor any connection that arifes neceffarily" 
 from the nature of the things ; fo it is alfo in na- 
 tural figns. The word gold has no fimilitude to 
 the fubftance fignified by it •, nor is it in its own 
 nature more fit to fignify this than any other 
 fubftance : yet, by habit and cuftom, it fuggefts 
 this and no other. In like manner, a fenfation of 
 touch fuggefts hardnefs, although it hath neicher 
 fimilitude to hardnefs, nor, as far as we can per- 
 ceive, any necefiary connection with it. The 
 difference betwixt thefe two figns lies only in 
 this, that, in the firft, the fuggeftion is, the ef- 
 fect of habit and cuftom ; in the fecond, it is 
 not the effect of habit, but of the original con- 
 ftitution of our minds. 
 
 It appears evident from what hath been faid 
 on the fubject of language, That there are natu- 
 ral figns, as well as artificial j and particularly, 
 That the thoughts, purpofes, and difpofitions of 
 the mind, have their natural figns in the features 
 of the face, the modulation of the voice, and the 
 motion and attitude of the body : That without 
 a natural knowledge of the connexion between 
 thefe figns, and the things fignified by them, lan- 
 guage could never have been invented, and efta- 
 F 4 blifhed 
 
8Z Of the HUMAN MIND. Chap. V. 
 
 blifhed among men : and, That the fine arts are 
 all founded upon this connexion, which we may 
 call the natural language of mankind. It is now 
 proper to obferve, that there are different orders 
 of natural figns, and to point out the different 
 claffes into which they may be diftinguifhed, that 
 we may more diftin£tly conceive the relation be- 
 tween our fenfations and the things they fuggeft, 
 and what we mean by calling fenfations figns of 
 external things. 
 
 The firft clafs of natural figns comprehends, 
 thofe whofe connection with the thing fignified is 
 eflablifhed by nature, but difcovered only by ex- 
 perience. The whole of genuine philofophy con^ 
 fifls in difcovering fuch connections, and redu- 
 cing them to general rules. The great Lord Ve- 
 rulam had a perfect comprehenfion of this, when 
 he called it an interpretation of nature. No man 
 ever more distinctly underftood, or happily ex- 
 prefled the nature and foundation of th&philofo- 
 phic art. What is all we know of mechanics, 
 aftronomy, and optics, but connections eflablifh- 
 ed by nature, and difcovered by experience or ob- 
 fervation, and confequences deduced from them ? 
 All the knowledge we have in agriculture, gar- 
 dening, chymiftry, and medicine, is built upon the 
 fame foundation. And if ever our philofophy 
 concerning the human mind is carried fo far as to, 
 deferve the name of fcience, which ought never 
 to be defpaired of, it muft be by obferving facts, 
 reducing them to general rules, and drawing juft 
 conclufions from them. What we commonly call 
 
 natural 
 
Sect. 3. OfTOUC H. 89 
 
 natural caufes might, with more propriety, be 
 called natural Jigns, and what we call effefls, the 
 things fignified. The caufes have no proper 
 efficiency or cafuality, as far as we know -, and 
 all we can certainly affirm, is, that nature hath 
 eftabliihed a conftant conjunction between them" 
 and the things called their effects ; and hath gi-< 
 ven to mankind a difpofition to obferve thofe 
 connections, to,confide in their continuance, and 
 to make ufe of them for the improvement of our 
 knowledge, and increafe of our power. 
 
 A fecond clafs is that wherein the connection 
 between the fign and thing fignified, is not only 
 eftabliflhed by nature, but difcovered to us by a 
 natural principle, without reafoning or experi- 
 ence. Of this kind are the natural figns of hu- 
 man thoughts, purpofes, and defires, which have 
 been already mentioned as the natural language 
 of mankind. An infant may be put into a fright 
 by an angry countenance, and foothed again by 
 fmiles and blandifhments. A child that has a 
 good mufical ear, may be put to fleep or to 
 dance, may be made merry or forrowful, by 
 the modulation of mufical founds. The prin- 
 ciples of all the fine arts, and of what we call a 
 fine tafte, may be refolved into connections of 
 this kind. A fine tafte may be improved by 
 reafoning and experience ; but if the firft princi-~ 
 pies of it weve not planted in our minds by na- 
 ture, it could- never be acquired. Nay, we have 
 already made it appear, that a great part of this 
 knowledge, which we have by nature, is loft by 
 
 the 
 
9 o OftheHUMAN MIND. Chap. V. 
 
 the difufe of natural figns, and the fubftitution 
 of artificial in their place. 
 
 A third clafs of natural figns comprehends 
 thofe which, tho' we never before had any no- 
 tion or conception of the things fignified, do 
 fuggeft it, or conjure It up, as it were, by a 
 natural kind of magic, and at once give us a 
 conception, and create a belief of it. I ftiewed 
 formerly, that our fenfations fuggeft to us a 
 fentient being or mind to which they belong : a 
 being which. hath a permanent exiftence, altho* 
 the fenfations are tranfient and of fhort duration : 
 a being which is ftill the fame, while its fenfati- 
 ons and other operations are varied ten thou- 
 sand ways : a being which hath the fame relati- 
 on to all that infinite variety of thoughts, pur- 
 pofes, actions, affections, enjoyments, and fuf- 
 ferings, which we are confcious of, or can re- 
 member. The conception of a mind is neither 
 an idea of fenfation nor of reflection ; for it is 
 neither like any of our fenfations, nor like any 
 thing we are confcious of. The firft conception 
 of it, as well as the belief of it, and of the com- 
 mon relation it bears to all that we are confcious 
 of, or remember, is fuggefted to every thinking 
 being, we don't know how. 
 
 The notion of hardnefs in bodies, as well as 
 the belief of it, are got in a fimilar manner •, be- 
 ing by an original principle of our nature, annex- 
 ed to that fenfation which we have when we 
 feel a hard body. And fo naturally and necef- 
 farily does the fenfation convey the notion and 
 
 belief 
 
Seft. 3. Of T O U C H. gi 
 
 belief of hardnefs, that hitherto they have been 
 confounded by the moft acute inquirers into the 
 principles of human nature, altho' they appear, 
 upon accurate refkaion, not only to be different 
 things, but as unlike as pain is to the point of a 
 fword. 
 
 It may be obferved, that as the firft clafs of 
 natural figns I have mentioned, is the founda- 
 tion of true philofophy, and the fecond, the 
 foundation of the fine arts, or of tafte ; fo the 
 laft is the foundation of common fenfe ; a part 
 of human nature which hath never been ex- 
 plained. 
 
 I take it for granted, that the notion of hard- 
 nefs, and the belief of it, is firft got by means 
 of that particular fenfation, which, as far back 
 as we can remember, does invariably fuggeft it; 
 and that if we had never had fuch a feeling, we 
 mould never have had any notion of hardnefs. I 
 think it is evident, that we cannot, by reafon- 
 ing from our fenfations, colleft the exiftence of 
 bodies at all, far lefs any of their qualities. This 
 hath been proved by unanfwerable arguments by 
 the Bifhop of Cloyne, and by the author of the 
 Treatife of human nature. It appears, as evident, 
 that this conneaion between our fenfations and 
 the conception and belief of external exiftences 
 cannot be produced by habit, experience, edu- 
 cation or any principle of human nature that 
 hath been admitted by philofophers. At the 
 fame time it is a faa, that fuch fenfations are 
 invariably conneaed with the conception and be- 
 lief 
 
92 Of the HUMAN MIND. Chap. V. 
 lief of external exiftences. Hence, by all rules 
 of juft reafoning, we muft conclude, that this 
 connection is the effect of our constitution, and 
 ought to be considered as an original principle 
 of human nature, till we find fome more gene- 
 ral principle into which it may be refolved. 
 
 SECT. IV. 
 
 Of hardnefs, and other primary qualities. 
 
 Tp Urther I obferve, that hardnefs is a qua- 
 lity, of which we have as clear and diftinct 
 a conception as of any thing whatfoever. The 
 cohefion of the parts of a body with more or lefs 
 force, is perfectly underfjtood, . tho' its caufe is 
 not : we know what it is, as well as how it a"f- 
 fefts the touch. It is therefore a quality of a 
 quite different order from thofe fecondary quali- 
 ties we have already taken notice of, whereof 
 we know no more naturally, than that they are 
 adapted to raife certain fenfations in us. If hard- 
 nefs were a quality of the fame kind, it would 
 be a proper inquiry for philofophers, What hard- 
 nefs in bodies is ? and we fhould have had vari- 
 ous hypothefes about it, as well as about colour 
 ,and heat. But it is evident that any fuch hypo- 
 thefis would be ridiculous. If any man fhould - 
 fay, that hardnefs in bodies is a certain vibra- 
 tion of their parts, or that it is a certain effluvia 
 emitted by them which effect our touch in the 
 manner we feel ; fuch hypothefes would fhock 
 
 common 
 
Sedt. 4: OfTOUC H. 93 
 
 common fenfe ; becaufe we all know, that if 
 the parts of a body' adhere ftrongly, it is hard, 
 altho' it mould neither emit effluvia, nor vibrate. 
 Yet at the fame time, no man can fay, but that 
 effluvia, or the vibration of the parts of a body, 
 might have arFeiSted our touch, in the fame man- 
 ner that hardnefs now does, if had fo pleated 
 the author of our nature ; and if either of thefe 
 hypothefes is applied to explain a fecondary qua- 
 lity, fuch as fmell, or tafte, or found, or colour, 
 or heat, . there appears • no manifeft abfurdity in 
 the fuppofition. 
 
 The diftinftipn betwixt primary .and fecondary 
 qualities hath had feveral revolutions. Demo* 
 critus and Epicurus, and their followers, main- 
 tained it. Ariftotle and the Peripatetics abolifh- 
 ed it. Des Cartes, Malebranche, and Locke, 
 revived it, and were thought to have put it in 
 a very clear light. But Biihop Berkeley again 
 difcarded this diftin&ion, by fuch proofs as muft 
 be convincing to thofe that hold the received 
 dodtrine of ideas. Yet, after all, there appears 
 to be a real foundation- for it in the principles of 
 our nature. 
 
 What hath been faid of hardnefs, is fo eafily 
 applicable, not only to its oppofite, foftnefs, but 
 likewife to roughnefs and fmoothnefs, to figure 
 and motion, that we may be excufedfrom mak- 
 ing the application, which would only be a re- 
 petition of what hath been faid. All thefe, by 
 means of certain correfponding fenfations of" 
 touch, are prefented to the mind as real exter- 
 nal 
 
94 Of the HUMAN MIND. Chap. V. 
 nal qualities ; the conception and the belief of 
 them are invariably connected with the corre- 
 fponding fenfations, by an original principle of 
 human nature. Their fenfations have no name 
 in any language ; they have not only been over- 
 looked by the vulgar, but by philofophers ; or if 
 they have been at all taken notice of, they have 
 been confounded with the external qualities 
 which they fuggeft. 
 
 SECT. V. 
 
 Ofextenjion. 
 
 T T is further to be obferved, that hardnefs and 
 foftnefs, roughnefs and fmoothnefs, figure and 
 motion, do all fuppofe extenfion, and cannot be 
 conceived without it ; yet I think it muft, on 
 the other hand, be allowed, that if we had 
 never felt any thing hard or foft, rough or 
 fmooth, figured or moved, we mould never 
 have had a conception of extenfion : fo that as 
 there is good ground to believe, that the notion 
 of extenfion could not be prior to that of other 
 primary qualities ; fo it is certain that it could 
 not be pofterior to the notion of any of them, 
 being neceflarily implied in them all. 
 
 Extenfion, therefore, feems to be a quality 
 fuggefted to us, by the very fame fenfations 
 which fuggeft the other qualities above mention- 
 ed. , "When I grafp a ball in my hand, I per- 
 ceive it at once hard, figured, and extended. 
 
 The 
 
Seft. 5. Of T O U C H. 95 
 
 The feeling is very fimple, and hath not the leaft 
 refemblance to any quality of body. Yet it 
 fuggefts to us three primary qualities perfectly 
 diftinct from one another, as well as from the 
 fenfation which indicates them. When I move 
 my hand along the table, the feeling is fo fim- 
 ple, that I find it difficult to diftinguifh it into 
 things of different natures ; yet it immediately 
 fuggefts hardnefs, ftnoothnefs, extenfion, and mo- 
 tion, things of very different natures, and all of 
 them as diftinctly underftood as the feeling which 
 fuggefts them. 
 
 We are commonly told by philofophers, that 
 we get the idea of extenfion by feeling along the 
 extremities of a body, as if there was no man- 
 ner of difficulty in the matter. I have fought, 
 with great pains, I confefs, to find out how this 
 idea can be got by feeling, but I have fought in 
 vain. Yet it is one of the cleareft and moft 
 diftindr. notions we have j nor is there any thing 
 whatfoever, about which the human underftand- 
 ing can carry on fo many long and demonftra- 
 tive trains of reafoning. 
 
 The notion of extenfion is fo familiar to us 
 from infancy, and fo constantly obtruded by 
 every thing we fee and feel, that we are apt to 
 think it obvious how it comes into the mind ; 
 but upon a narrower examination we fhall find 
 it utterly inexplicable. It is true we have feel- 
 ings of touch, which every moment prefent ex- 
 tention to the mind •, but how they come to do 
 fo, is the queftion ; for jhofe feelings do no more 
 
 refemble 
 
g6 Ofthe HUMAN MIND. Chap. V. 
 referable extenfion, than they refemble jufticeor 
 courage : nor can the exiftence of extended 
 things be inferred from thofe feelings by any 
 rules of reafoning : fo that the feelings we have 
 by touch, can neither explain how . we get the 
 notion, nor how we come by the belief of ex- 
 tended things. 
 
 What hath impofed upon philofophers in this 
 matter, is, that the feelings of touch, which fug- 
 ged primary qualities, have no names, nor are 
 they ever reflected Upon. They pafs through 
 the mind inftantaneoufly, arid ferve only to in- 
 troduce the notion and belief of external things, 
 which by our conftitution are con nefted with them. 
 They are natural figns, and the mind immediately 
 pafles to the thing fignified, without making the 
 kaft reflection upon the fign, or obferving that 
 there was any fuch thing. Hence it hath always 
 been taken for granted, thatthe ideas of extenfion, 
 figure, and motion, are ideas of fenfation, which 
 enter into the mind by the fenfe of touch, in the 
 fame manner as the fenfatioris of found and fmell 
 do by the ear and nofe.' The fenfations of touch 
 are fo connected, by our conftitution, with the 
 notions of extenfion, figure, and motion, that phi- 
 lofophers have miftaken the one for the other, 
 and never have been able to difcern that they 
 were not only diftincl things, but altogether un- 
 like. However, if we will reafon diftinctly up- 
 on this fubjeft, we ought to give names to thofe 
 feelings of touch ; we muft accuftom ourfelves 
 3 * to 
 
Se«5t. 5 . Or TOUCH. 97 
 
 to attend to them, and to refledl upon them, 
 that we may be able to disjoin them from, and 
 to compare them with, the qualities fignified or 
 fuggefted by them. 
 
 The habit of doing this is not to be attained 
 without pains and practice ; and till a man hath 
 acquired this habit, it will be impoffible for him 
 to think diftin&ly, or to judge right, upon this 
 fubject. 
 
 Let a man prefs his hand againft the table : 
 he feels it hard. But what is the meaning of 
 this ? the meaning undoubtedly is, that he hath 
 a certain feeling of touch, from which he con-^ 
 eludes, without any reafoning, or comparing 
 ideas, that there is fomething external really ex^ 
 ifting, whofe parts flick fo firmly together, that 
 they cannot be difplaced without confiderable 
 force. , 
 
 There is here a feeling, and a conclufion drawn 
 from it, or fome way fuggefted by it. In order 
 to compare thefe, we muft view them feparately, 
 and then confider by what tie they are connected, 
 and wherein they refemble one another. The 
 hardnefs of the table is the conclufion, the feeling 
 is the medium by which we are led to that con- 
 clufion. Let a man attend diftin&ly to this me- 
 dium, and to the conclufion, and he will perceive 
 them to be as unlike as any two things in nature, 
 The one is a fenfation of the mind, which can 
 have no exiftence but in a fentient being ; nor 
 can it exift one moment longer than it is felt ; 
 the other is. in the table, and we conclude with- 
 G ' owl 
 
98 Of the HUMAN MIND. Chap. V, 
 out any difficulty, that it was in the table before 
 it was felt, and continues after the feeling is 
 over. The one implies no kind of e^tenfion, 
 nor parts, nor cohefion ; the other implies all 
 thefe. Eoth indeed admit of degrees, and the 
 feeling, beyond a certain degree, is a fpecies of 
 pain; but adamantine hardnefs does not imply 
 the leaft pain. 
 
 And as the feeling hath no fimilitude to hard- 
 nefs, fo neither can our reafon perceive the leaft 
 tie or connection between them ; nor will the 
 logician ever be able to (how a reafon why we 
 ftiould conclude hardnefs from this feeling, rather 
 than foftnefs, or any other quality whatfoever. 
 But in reality all mankind are led by their eon- 
 ftitution to conclude hardnefs from this feeling. 
 
 The fenfation of heat, and the fenfation we 
 have by preffinga hard body, are equally feelings : 
 nor can we by reafoningdraw any conclufion from 
 the one, but what may be drawn from the other: 
 but, by our conftitution, we conclude from the 
 firft an obfcure or occult quality, of which we 
 have only this relative conception, that it is 
 fomething adapted to raife in us the fenfation of 
 heat; from theiecond, we conclude a quality of 
 which we have a clear and diftincl: conception, 
 to wit, the hardnefs of the body. , 
 
 SECT. 
 
Sed. 6. Of TOUCH. 99 
 
 SECT. VI. 
 
 Of extenfion. 
 
 HT O put this matter in another light, it may 
 be proper to try, whether from fenfation 
 alone we can colled any notion of extenfion, fi- 
 gure, motion, and fpace. I take it for granted, 
 that a blind manjiath the fame notions of exten- 
 fion, figure, and motion, as a man that fees $ 
 that Dr. Saunderfon had the fame notion of a cone* 
 a cylinder, and a fphere, and of the motions and 
 diftances of the heavenly bodies, as Sir Ifaac 
 Newton. 
 
 As fight therefore is not neceffary for our ac- 
 quiring thofe notions, we (hall leave it out alto- 
 gether in ourinquiry into the firfl; origin of them ; 
 and (hall fuppofe a blind man, by fome flrange 
 diftemper, to have loft all the experience and ha- 
 bits and notions he had got by touch ; not to 
 have the leaft conception of the exiftence, figure, 
 dimenfions, or extenfion, either of his own body, 
 or of any other ; but to have all his knowledge 
 of external things to acquire anew, by means of 
 fenfation, and the. power of reafon, which we 
 fuppofe to remain entire. 
 
 "We fhall; firfty fuppofe his body fixed immove- 
 ably in one place, and that he can only have 
 the feelings of touch, by the application of other 
 bodies to it. Suppofe him firft to be pricked 
 with a pin ; this will, no doubt, give a fmart 
 G 2 fenfation s 
 
ioo OftheHUMAN MIND. Chap. V. 
 fenfation : he feels pain •, but what can he infer 
 from it ? Nothing furely with regard to the exift- 
 ence or figure of a pin. He can infer nothing 
 from this fpecies of pain, which he may not as 
 well infer from the gout or fciatica. Common 
 fenfe may lead him to think that this pain has a 
 caufe ; but whether this caufe is body or fpirit, 
 extended or unextended, figured or not figured, 
 he cannot pofiibly, from any principle's he is fup^ 
 pofed to have, form the leaft conjecture. Ha- 
 ving had formerly no notion of body or of exten- 
 fion, the prick of a pin can give him none, 
 
 Suppofe, next, a body not pointed, but blunt, 
 is applied to his body with a force gradually in- 
 creafed until it bruifes him. What has he got 
 by thisi but another fenfation, or train of fenfa,- 
 tions, from which he is able to conclude as little 
 as from the former ? A fchirrous tumour in any 
 inward part of the body, by prefilng upon the 
 adjacent parts, may give the fame kind of fenfa- 
 tion as the preffure of an external body, without, 
 conveying any notion but thai: of pain, which 
 furely hath no refemblance to extenfion. 
 
 Suppofe, thirdly, that the body applied to him 
 touches a larger or a lefier part of his body. 
 Can this give him any notion of its extenfion or 
 dimenfions ? To me it feems impofiible that it 
 fhould, unlefs he had fome previous notion of the 
 dimenfions and figure of his own body, to ferve 
 him as a meafure. When my two hands touch 
 the extremities of a body ; if I know them to be 
 a foot afunder, I eafily called that the body is a 
 
 % foot 
 
Se&. 6. Of TOUCH. lot 
 
 foot long ; and if I know them to be five feet 
 afunder, that it is five feet long : but if I know 
 not what the diftance of my hands is, I cannot 
 know the length of the objedT: they grafp ; and 
 if I have no previous notion of hands at all, or 
 of diftance between them, I can never get that 
 notion by their being touched. 
 
 Suppofe, again, that a body is drawn along 
 his hands or face, while they are at reft : Can 
 this give him any notion of fpace or motion ? It 
 no doubt gives a new feeling; but how it 
 mould convey a notion of fpace or motion, to 
 one who had none before, I cannot conceive. 
 The blood moves along the arteries and veins, 
 and this motion, when violent, is felt : but I 
 imagine no man, by this feeling, could get the 
 conception of fpace or motion, if he had it not 
 before. Such a motion may give a certain fuc- 
 ceffion of feelings, as the cholic may do ; but 
 no feelings, nor any combination of feelings, can 
 ever refemble fpace or motion* 
 
 Let us next fuppofe, that he makes fome in- 
 ftindive effort to move his head cr his hand ; but 
 that no motion follows, either on account of ex- 
 ternal refiftance, ar of palfy. Can this effort 
 convey the notion of fpace and motion to one 
 who never had it before ? Surely it cannot. 
 
 Laft of all, let us fuppofe, that he moves a limb 
 by inftin£r, without having had any previous no- 
 tion of fpace or motion. He has here anew fenfa- 
 tion, which accompanies the flexure of joints,, and 
 thefwellingofmufcles. But how this fenfation can 
 convey into his mind the idea of fpace and motion, is 
 G 3 l ftill 
 
102 OftheHUMAN MIND. Chap. V, 
 {till altogether my fterious and unintelligible. The 
 motion's of the heart and lungs are all performed 
 by the contraction of mufcles, yet give no con- 
 ception of fpace or motion. An embryo in the 
 womb has many fuch motions, and probably the 
 feelings that accompany them, without any idea 
 pf fpace or motion. 
 
 Upon the whole, it appears, that our philofo- 
 phers have impofed upon themfelves, and upon us, 
 in pretending to deduce from fenfation the firfb 
 origin of our notions of external exiftences, of 
 fpace, motion, andextenfion, and all the primary 
 qualities of body, that is, the qualities whereof 
 we have the moft clear and diftinct conception. 
 Thefe qualities do not at all tally with any fy- 
 fiem of the human faculties that hath been ad- 
 vanced. They have no refemblance to any fen- 
 fation, or to any operation of our minds ; and 
 therefore they cannot be ideas either of fenfation, 
 , or of reflection. The very conception of them 
 is irreconcileable to the principles of allourphi- 
 lofophic fyftems of the underftanding. The be-, 
 lief of them is no lefs fo. 
 
 SECT. VII. 
 
 Of the exiftence of a material world. 
 
 T T is beyond our power to fay, when or in 
 what order we came by our notions of thefe 
 qualities. When we trace the operations of our 
 minds as far back as memory and reflection can 
 carry us,,* we find them already in poffeffion of 
 
 our 
 
Seft. 7. Of T O U C H. 103 
 
 our imagination and belief, and quite familiar to 
 the mind : but how they came firft into its ac- 
 quaintance, or what has given them fo ftrong a 
 hold of our belief, and what regard they deferve, 
 are no doubt very important queftions in the 
 philofophy of human nature. 
 
 Shall we, with the Bifhop of Cloyne, ferve 
 them with a <j$uo warranto, and have them tried 
 at the bar of philofophy, upon the ftatute of the 
 ideal fyftem ? Indeed, in this trial they feem to 
 have come off very pitifully. For altho' they 
 had very able counfel, learned in the law, viz. 
 Des Cartes, Malebranche, and Locke, who faid 
 every thing they could for their clients •, the Bi- 
 fhop of Cloyne, believing them to be aiders and 
 abetters of herefy and fchifm, profecuted them 
 with great vigour, fully anfwered all that had been 
 pleaded in their defence, and filenced their ableft 
 advocates, who feem for. half a century paft to 
 decline the argument, and to truft to the favour 
 of the jury rather than to the ftrength of their 
 pleadings. 
 
 Thus, the wifdom of philofophy is fet in oppo- 
 fition to the common fenje of mankind. The 
 firft pretends to demonftrate a priori, that there 
 can be no fuch thing as a material world ; that 
 fun, moon, ftars, and earth, vegetable and ani- 
 mal bodies, are, and can be nothing elfe, but fen- 
 fations in the mind, or images of thofe fenfations 
 in the memory and imagination ; that, like pain 
 and joy, they can have no existence when they 
 are not thought of. The la'ft can conceive no 
 G 4 otherwife 
 
*©4 Ofthe HUMAN MIND. Chap. V. 
 otherwife of this opinion, than as a kind of me- 
 taphyfical lunacy ; and concludes, that too much 
 learning is apt to rr.ake men mad ; and that the 
 man who ferioufly entertains this belief, tho' in 
 other refpe&s he may be a very good man, as a 
 man may be who believes that he is made of 
 glafs •, yet furely he hath a foft place in hisunder- 
 ftanding, arid hath been hurt by much thinking* 
 
 This oppofition betwixt philofophy and com- 
 mon fenfe, is apt to have a very unhappy influ- 
 ence upon the philofopher himfelf. He fees hu- 
 man nature in an odd, unamiable, and mortifying 
 light. He confiders himfelf, and the reft of his 
 fpecies, as born under a neceffity of believing ten 
 thoufand abfurdities and contradictions, and en- 
 dowed with fuch a pittance of reafon, as is juft 
 fufficient to make this unhappy difcovery : and 
 this is all the fruit of his profound fpeculations. 
 Such notions of human nature. tend to flacken 
 every nerve of the foul, to put every noble pur- 
 pofe and fentiment out of countenance, and fpread 
 a melancholy gloom over the whole face of 
 things. / 
 
 If this is wifdom, let me be deluded with the vul- 
 gar. I find fomething within methat recoils againft 
 It, and infpires more reverent fentiments of the 
 human kind, and of the universal adminiftration. 
 Common fenfe and reafon have both one author ; 
 that Almighty author, in all whofe other works 
 we obferve a confiftency, uniformity, and beauty, 
 which charm and delight the underftanding : there 
 muft therefore be fome order and confiftency in the 
 
 human 
 
Sea. 7. Gf TOUCH. 105 
 
 human faculties, as well as in other parts of his 
 workmanfhip. A man that thinks reverently of 
 his own kind, and efteems true wifdom and phi- 
 lofophy, will not be fond, nay, will be very fuf- 
 picious, of fuch ftrange and paradoxical opi- 
 nions. If they are falfe, they difgrace philofophy; 
 and if they are true, they degrade the human fpe- 
 cies,. and make us juftly afliamed of our frame. 
 
 To what purpofe is it for philofophy to decide 
 againft common fenfe in this or any other matter? 
 The belief of a material world is older, and of more 
 authority, than any principlesof philofophy. Itde- 
 clines the tribunal of reafon, and laughs at all the 
 artillery of the logician. It retains its fovereign 
 authority in fpite of all the edicts of philofophy, 
 and reafon itfelf muft floop to its orders. Even 
 thofe philofophers who have difowned the autho- 
 rity of our notions of an external material world, 
 confefs, that they find themfelves under a necef- 
 fity of fubmitting to their power. 
 
 Methinks, therefore, it were better to make 
 a virtue of neceffity ; and, fince we cannot get 
 rid of the vulgar notion and belief of an external 
 world, to reconcile our reafon to it as well as we 
 can : for if Reafon mould ftomach and fret ever 
 fo much at this yoke, fhe cannot throw it off; if 
 fhe will not be the fervant of Common Senfe, 
 fhe muft be her flave. 
 
 In order therefore to reconcile reafon to com- 
 mon fenfe in this matter, I beg leave to offer to 
 the confederation of philofophers thefe two ob- 
 servations. Firft, That in all this debate about 
 
 the 
 
ioo" Ofthe HUMAN MIND. Chap. V. 
 the exiftence of a material world, it hath been 
 taken for granted on both fides, that this fame 
 material world, if any fuch there be, muffc 
 be the exprefs image of our fenfations ; that we 
 can have no conception of any material thing 
 which is not like fome fenfation in our minds ; 
 and particularly, that the fenfations of touch 
 are images of extenfion, hardnefs, figure, and 
 motion. Every argument brought againft the 
 exiftence of a material world, either by the Bi- 
 fhop of Cloyne, or by the author of the Treatife 
 of human nature, fuppofeth this. If this is true, 
 their arguments are conclufive and unanfwerable: 
 but, on the other hand, if it is not true, there is 
 no fhadow of argument left. Have thofe philo- 
 sophers then given any folid proof of this hypo- 
 thefis, upon which the whole weight of fo ftrange 
 a fyftem refts ? No. They have not fo much as 
 attempted to do it. But, becaufe antient and 
 modern philofophers have agreed in this opinion, 
 they have taken it for granted. But let us, as 
 becomes philofophers, lay afide authority ; we 
 need not furely confult Ariftotle or Locke, to 
 know whether pain be like the point of a fword. 
 I have as clear a conception of extenfion, hard* 
 nefs, and motion, as I have of the point of a fword} 
 and, with fome pains and pra&ice, I can form as 
 clear a notion of the other fenfations of touch, as 
 1 have of pain. When I do fo, and compare them 
 together., it appears to me clear as day-light, that 
 the former are not of kin to the latter, nor re= 
 femble them in any one feature. They are as 
 
 -f unlike. 
 
Seft. 7. Of T O U C H. 107 
 
 unlike, yea as certainly and manifeftly unlike, 
 as pain is to the point of afword. It may be true, 
 that thofe fenfations firft introduced the material 
 world to our acquaintance ; it may be true, that it 
 feldom or never appears without' their company; 
 but, for all that, they are as unlike as the paffion 
 of anger is to thofe features of the countenance 
 which attend it. 
 
 So that, in the fentence thofe philofophers 
 have pafled againft the material world, there is 
 an error per/on*. Their proof touches not mat- 
 ter, or any of its qualities •, but ftrikes direaiy 
 againft an idol of their own imagination, a ma- 
 terial world made of ideas and fenfations, which 
 never had nor can have an exiftence. 
 
 Secondly, The very exiftence of our concept 
 tions of extenfion, figure, and motion, fince they 
 are neither ideas of fenfation nor refkaion, over- 
 turns the whole ideal fyftem, by which the 
 material world hath been tried and condemned : 
 fo that there hath been likewife in this fentence 
 an error juris. 
 
 It is a very fine and a juft obfervation of 
 Locke, That as no human art can create a fingle 
 particle of matter, and the whole extent of our 
 power over the material world, confifts in com- 
 pounding, combining, and disjoining the matter 
 made to our hands ; fo in the world of thought, 
 the materials are all made by nature, and can 
 only be varioufly combined and disjoined by us. 
 So that it is impoMible for reafon or prejudice, 
 true or falfe philofophy, to produce one fimple 
 
 notion 
 
io8 Ofthe HUMAN MIND. Chap. V. 
 notion or conception, which is not the work of 
 nature, and the refult of our conftitution. The 
 conception of extenfion, motion, and the other 
 attributes of matter, cannot be the effect of 
 error or prejudice-, it muft be the work of na- 
 ture. And the power or faculty, by which we 
 acquire thofe conceptions, muft be fomething 
 different from any power of the human mind 
 that hath been explained, fince it is neither fen- 
 fation nor reflection. 
 
 This I would therefore humbly propofe as an 
 experimentum cruets, by which the ideal fyftem 
 muft ftand or fall ; and it brings the matter to 
 a fhort iffue : Extenfion, figure, motion, may, 
 any one, or all of them, be taken for the fub- 
 jecT: of this experiment. Either they are ideas 
 of fenfation, or they are not. If any one of 
 them can be fhown to be an idea of fenfation, or 
 to have the leaft refemblance to any fenfation, I 
 lay my hand upon my mouth, and give up all 
 pretence to reconcile reafon to common fenfe in 
 this matter, and muft fuffer the ideal fcepticifm 
 to triumph. But if, on the other hand, they 
 are not ideas of fenfation, nor like to any fenfa- 
 tion, then the ideal fyftem is a rope of fand, and 
 all the laboured arguments of the fceptical philo- 
 fophy againft a material world, and againft the 
 existence of every thing but impreffions and 
 ideas, proceed upon a falfe hypothefis. 
 
 If our philofophy concerning the mind be fo 
 lame with regard to the origin of our, notions of 
 the cleareft, moft fimple, and mod familiar ob- 
 jects 
 
Se£t. 7. Of TOUCH. 10$ 
 
 jefts of thought, and the powers from which 
 they are derived, can we expedt that it fhould 
 be more perfedl in the account it gives of the 
 origin of our opinions and belief? We have ken 
 already fome inftances of its imperfe&ion in 
 this refpecl: : and perhaps that fame nature which 
 hath given us the power to conceive things al- 
 together unlike to any of our fenfations, or to 
 any operation of our minds, hath likewife pro- 
 vided for our belief of them, by fome part of 
 our conftitution hitherto not explained, 
 
 Bifhop Berkeley hath proved, beyond the 
 poflibility of reply, that we cannot by reafonino- 
 infer the exiftence of matter from our fenfations: 
 and the author of the Treatife of human nature 
 hath proved no lefs clearly, that we cannot by 
 reafoning infer the exiftence of our own or other 
 minds from our fenfations. But are we to ad- 
 mit nothing but what can, be proved by reafon- 
 ing ? Then we muft be fceptics indeed, and be- 
 lieve nothing at all. The author of the Treatife 
 of human nature appears to me to be but a half 
 fceptic. He hath not followed his principles fo 
 far as they lead him : but after having, with un- 
 paralleled intrepidity and Tuccefs, combated vul- 
 gar prejudices ; when he had but one blow to 
 flrike, his courage fails him, he fairly lays down 
 his arms, and yields himfelf a captive to the moft 
 common of all vulgar prejudices, I mean the be- 
 lief of the exiftence of his own imprefiions and 
 ideas. 
 
 I beg 
 
iio Of the HUMAN MIND. Chap. V, 
 I beg therefore to have the honour of mak- 
 ing an addition to the fceptical fyftem, without 
 which I conceive it cannot hang together. I 
 affirm, that the belief of the exiftence of impref- 
 lions and ideas, is as little fupported by reafonj 
 as that of the exiftence of minds and bodies. 
 No man ever did, or could offer any reafon for 
 this belief. Des Cartes took it for granted* 
 that he .thought, and had fenfations and ideas; 
 fo have all his followers done. Even the hero 
 of fcepticifm hath yielded this point, I crave 
 leave to fay* weakly and imprudently. I fay 
 fo, becaufe I am perfuaded that there is no prin- 
 ciple of his philofophy that obliged him to make 
 this conceffion. And what is there in impref- 
 fions and ideas fo formidable, that this all-con- 
 quering philofophy, after triumphing over every 
 other exiftence, mould pay homage to them ? 
 Befides, the conceffion is dangerous : for belief 
 is of fuch a nature, that if you leave any root, 
 It will fpread ; and you may more eafily pull it 
 up altogether, than fay, Hitherto (halt thou go, 
 and no further •, the exiftence of impreffions and 
 ideas I give up to thee ; but fee thou pretend to 
 nothing more. A thorough and confiltent fcep- 
 tic will never, therefore, yield this point ; and 
 while he holds it, you can never oblige him to 
 yield any thing elfe. 
 
 To fuch a fceptic I have nothing to fay ; but 
 of the femi-fceptics, I fhould beg to know, why 
 they believe the exiftence of their impreffions 
 and ideas. The true reafon I take to be, be- 
 caufe 
 
Seel. 7. Of TOUCH. rii 
 
 caufe they cannot help it; and the fame realofl 
 will lead them to believe many other things. 
 All reafoning muft be from firft principles ; 
 . . and for firft principles no other reafon can be 
 given but this, that, by the conftitution of our 
 nature, we are under a neceflity of aflenting to 
 them. Such principles are parts of our confti- 
 tuiion, no lefs than the power of thinking: rea- 
 fon can neither make nor deftroy them ; nor 
 can it do any thing without them : it is like a 
 telefcope, which may help a man to fee farther, 
 who hath eyes; but without eyes, a telefcope 
 fhews nothing at all. A mathematician cannot 
 prove the truth of his axioms, nor can he prove 
 any thing, unlefs he takes them for granted. We 
 cannot prove the exiftence of our minds, nor 
 even of our thoughts and fenfations. A hifto- 
 rian, or a witnefs, can prove nothing, unlefs it is 
 taken for granted, that the memory and fenfes 
 may be trufted. A natural philofopher can prove 
 nothing, unlefs it is taken for granted, that the 
 courfe of nature is fteady and uniform. 
 
 How or when I got fuch firft principles, upon 
 which I build all my reafoning, I know not; for 
 I had them before! can remember: but I am 
 fure they are parts of my conftitution, and that 
 I cannot throw them off. That our thoughts 
 and fenfations muft have a fubjecl, which we 
 call ourfelf, is not therefore an opinion got by 
 reafoning, but a natural principle. That our 
 fenfations of touch indicate fomething external, 
 extended, figured, hard or foft, is not a de- 
 duction 
 
ii2 Ofthe HUMAN MIND. Chap.V. 
 
 duftion of reafon, but a natural principle. The 
 belief of it, and the very conception of it, are 
 equally parts of our conftitution. If we are de- 
 ceived in it, we are deceived by him that made 
 us, and there is no remedy. 
 
 1 do not mean to affirm, that the fenfations 
 of touch do from the very firft fuggeft the fame 
 notions of body and its qualities, which they do 
 when we are grown up. Perhaps Nature is 
 frugal in this, as in her other operations. The 
 paflion of love, with all its concomitant fenti- 
 ments and defires, is naturally fuggefted by the 
 perception of beauty in the other fex. Yet the 
 fame perception does not fuggeft the tender paf- 
 fion, till a certain period of life. A blow given 
 to an infant, raifes grief and lamentation ; but 
 when he grows up, it as naturally ftirs refent-- 
 ment, and prompts him to refiftance. Perhaps 
 a child in the womb, or for fome fhort period of 
 its existence, is merely a fentient being: the 
 faculties, by which it perceives an external 
 world, by which it reflects on its own thoughts, 
 and exiftence, and relation to other things, as 
 well as its reafoning and moral faculties, unfold 
 themfelves by degrees ; fo that it is infpired with 
 the various principles of common fenfe, as with 
 the paffions of love and refentment, when it has 
 occafion for them. 
 
 SECT. 
 
Sea. 8. Of TOUCH. 
 
 i»3 
 
 SECT. VIII. 
 
 Of the fyftems of philofophers concerning thefenfes. 
 
 ALL the fyftems of philofophers about our 
 fenfes and their objects have fplit upon this 
 rock, of not diftinguifhing properly fenfations, 
 which can have no exiflence but when they are 
 felt, from the things fuggefted by them. Ari- 
 ftotle, with as diftinguifhing a head as ever ap- 
 plied to philofophicaldifquifidons, confounds thele 
 two ; and makes every fenfation to be the fcrm 4 
 without the matter, of the thing perceived by it. 
 As the impreffion of a feal upon wax has the form 
 of the feal, but nothing of the matter of it ; (o 
 he conceived our fenfations to be impreffions up- 
 on the mind, which bear the image, likenefs, or 
 form of the external thing perceived, without 
 the matter of it. Colour, found, and fmell, as 
 well as extenfion, figure, and hardnefs, are, ac- 
 cording to him, various forms of matter : our 
 fenfations are the fame forms imprinted on the 
 mind, and perceived in its own intellect. It is 
 evident from this, that Ariftotle made no diftinc- 
 tion between primary and fecondary qualities of 
 bodies, although that diftinction was made by 
 Democritus, Epicurus, and others of the ancients. 
 Des Cartes, Malebranche, and Locke, revived 
 the diftinction between primary and fecondary 
 qualities. But they made the fecondary qualities 
 mere fenfations, and the primary ones refemblan- 
 
 H ces 
 
ii4 Of the HUMAN MIND. Chap. V. 
 
 ces of our fenfations. They maintained, that co- 
 lour, found, and heat, are not any thing in bo- 
 dies, but fenfations of the mind : At the fame 
 time, they acknowledged fome particular texture 
 or modification of the "body, to be the caufe or 
 occafion of thofe fenfations ; but to this modifi- 
 cation they gave no name. Whereas, by the vul- 
 gar, the names of colour, heat, and found, are 
 but rarely applied to the fenfations, and moft 
 commonly to thofe unknown caufes of them } as- 
 hath been already explained. The conftitution of 
 ,our nature leads us rather to attend to the things 
 fignified by the fenfation, than to the fenfation it- 
 felf, and to give a name to the former rather than 
 to the latter. Thus we fee, that with regard to 
 fecondary qualities, thefe philoibphers thought 
 with the vulgar, and With common fenfe. Their 
 paradoxes were only an abufe of words. For when 
 they maintain, as an important modern difcovery, 
 that there is no heat in the fire, they meah no 
 more, than that the fire does not feel heat, which 
 every one knew before. 
 
 With regard to primary qualities, thefe philo- 
 fophers erred more grofsly : They indeed belie- 
 ved the exiftence of thofe qualities ; but they 
 did not at all attend to the fenfations that fug- 
 geft them, which having no names, have been as 
 little considered as if they had no exiftence. 
 They were aware, that figure, extenfion, and- 
 jiardnefs, are perceived by means of fenfations of 
 touch ; whence they ralhly concluded, that thefe 
 
 J fenfations 
 
Seft. 8. Of TOUCH. n 5 
 
 fenfations muft be images and refemblances of 
 figure, extenfion, and hardnefs. 
 
 The received hypothefis of ideas naturally led 
 them to this conclufion ; and indeed cannot con- 
 fift with any other ; for, according to that hy- 
 pothefis, external things muft be perceived by- 
 means of images of them in the mind ; and what 
 can thofe images of external things in the mind 
 be, but the fenfations by which we perceive them ?. 
 
 This however was to draw a conclufion from 
 a hypothefis againft fact. We need not have re- 
 courfe to any hypothefis to know what our fen- 
 fations are, or what they are like. By a proper 
 degree of reflection and attention we may un- 
 derftand them 'perfectly, and be as certain that 
 they are not like any quality of body, as we can 
 be, that the toothach is not like a triangle. How 
 a fenfation mould inftantly make us conceive and 
 believe the exiftence of an external thing altoge- 
 ther unlike to it, I do not pretend to know ; and 
 when I fay that the one fuggefts the other, I 
 mean not to explain the manner of their connec- 
 tion, but to exprefs a fact, which every one may 
 be confcious of; namely, that, by a law of our 
 nature, fuch a conception and belief conftantly 
 and immediately follow the fenfation. 
 
 Biftiop Berkeley gave new light to this fub- 
 je£t, by Ihowing, that the qualities of an inani- 
 mate thing, fuch as matter is conceived to be, 
 cannot referable any fenfation ; that it is impof- 
 fible to conceive any thing like the fenfations 
 of pur minds, but the fenfations of other minds. 
 H 2 Every 
 
n6 Of the HUMAN MIND. Chap,V. 
 Every one that attends properly to his fenfatioriS' 
 fnuft afient to this ; yet. it had efcaped all the 
 philofophers that came before Berkeley ; it had 
 efcaped even the ingenious Locke, who had fo 
 much praclifed reflection' on the operations of his 
 own mind. So difficult it is to attend properly 
 even to our own feelings. They are fo accuftom- 
 ed to pafs through the mind unobferved^ and irr- 
 ftantly to make way for that which nature in- 
 tended them to fignify, that it is extremely diffi- 
 cult to ftop, and furvey them ; and when we- 
 think we have acquired this power,, perhaps the 
 mind ftill fluctuates between the fenfation and its- 
 afibciated quality, fo that they mix together, and 
 prefent fomething to the imagination that is com- 
 pounded of both. Thus in a globe or cylinder,, 
 whofe oppofite fides are quite unlike in colour, if 
 you turn it (lowly, the colours are perfedly di- 
 ftinguifhable, and their diffimilitude is manifeft ; 
 but if it is turned fafl, they lofe their distinction, 
 and feem to be of one and the fame colour. 
 
 No fuccefilon can be more quick, than that of 
 tangible qualities to the fenfations with which 
 nature has aflbciated them : But when one has 
 once acquired the art of making them feparate 
 and diftinct objects of thought, he will then clear- 
 ly perceive, that the maxim of Bifhop Berkeley 
 above mentioned, is felf-evident ; and that the 
 features of the face are not more unlike to a paf- 
 fion of the mind which they indicate, than the 
 fenfations of touch are to the primary qualities of 
 body. 
 
 But 
 
Se<3. 8. Of TOUCH. u 7 
 
 But let us obferve what ufe the Bilhop makes 
 •of this important difcovery : Why, he concludes, 
 that we can have no conception of an inanimate 
 fubftance, fuch as matter is conceived to be, or 
 ©f any of its qualities ; and that there is the 
 ftrongeft ground to believe that there is no ex- 
 iftence in nature but minds, fenfations, and ideas : 
 If there is any other kind of exi'ftences, it muft 
 be what we neither have nor can have any con- 
 ception of. But how does this follow ? Why 
 thus : We can have no conception of any thing 
 but what refembles fome fenfation or idea in our 
 minds ; but the fenfations and ideas in our minds 
 can refemble nothing but the fenfations and ideas 
 in other minds ; therefore, the conclufion is evi- 
 dent. This argument, we fee, leans upon two 
 propofitions. The laft of them the ingenious au- 
 thor hath indeed made evident to all that under- 
 ftand his reafoning, and can attend to their own 
 fenfations : but the firft propofition he never at- 
 tempts to prove ; it is taken from the doctrine of 
 ideas, which hath been fo univerfally received by 
 philofophers, that it was thought to need no 
 proof. 
 
 We may here again obferve, that this acute 
 writer argues from a hypothefis againft faft, and 
 againft the common fenfe of mankind. That we 
 can have no conception of any thing, unlefs there 
 is fome impreffion, fenfation, or idea, in our minds 
 which refembles it, is indeed an opinion which 
 hath been very generally received among philo- 
 fophers j but it is neither felf-evident, nor hath 
 
 H 3 it 
 
n8 Of the HUM AM MIND. Chap.V. 
 
 it been clearly proved -, and therefore it had been 
 more reafonable to call in queftion this doctrine 
 of philofophers, than to difcard the material 
 world, and by that means expofe philofophy to 
 the ridicule of all men, who will not offer up 
 common fenfe as a facrifice to metaphyfics. 
 
 We ought, however, to do this juftice both to 
 the Bifhop of Cloyne and to the author of the 
 Treatife of human nature, to acknowledge, that 
 their conclufions are juftly drawn from the doc- 
 trine of ideas, which has been fo univerfally re- 
 ceived. On the other hand, from the character of 
 Bifhop Berkeley, and of his predeceffors Des Car- 
 tes, Locke, and Malebranche, we may venture 
 to fay, that if they had feen all the confequences 
 of this doctrine, as clearly as the author before 
 mentioned did, they would have fufpected it ve- 
 hemently, and examined it more carefully than 
 they appear to have done. 
 
 The theory of ideas, like the Trojan horfe, 
 had a fpecious appearance both of innocence and 
 beauty •, but if thofe philofophers had known that 
 it carried in its belly death and destruction to all 
 fcience and common fenfe, they would not have> 
 broken down their walls to give it admittance. 
 
 That we have clear and diftindt conceptions of 
 extenfion, figure, motion, and other attributes of 
 body, which are neither fenfations, nor like any 
 fenfation, is a fact of which we may be as certain, 
 as that we have fenfations. And that all mankind 
 have a fixed belief of an external material world, 
 a belief which is neither got by reafoning nor 
 
 .education, 
 
Seft. 8. Of TOUCH. 119 
 
 education, and a belief which we cannot Ihake off, 
 even when we feem to have ftrong arguments 
 againft it, and no fhadow of argument for it, is 
 likewife a fact, for which we have all the evidence 
 that the nature of the thing admits. Thefe facts 
 are phsenomena of human ..nature, from which 
 we may juftly argue againft any hypothefis, how- 
 ever generally received. But to argue from a 
 hypothefis againft facts, is contrary to the rules 
 of true philolbphy. 
 
 H 4 CHAP. 
 
C I20 ] 
 
 CHAP. VI. 
 
 Of SEEING. 
 
 SECT. I. 
 
 The excellence and dignity of this faculty. 
 
 THE advances made in the knowledge of 
 optics in the laft age, and in the prefent, 
 and chiefly the difcoveries of Sir Ifaac Newton, 
 do honour, not to philofophy only, but to hu- 
 man nature. Such difcoveries ought for ever to 
 put to fhame the ignoble attempts of our modern 
 fceptics to depreciate the human understanding, 
 and to difpirit men in the fearch of truth, by 
 reprefenting the human faculties as fit for no- 
 thing, but to lead us into abfurdities and contra- 
 dictions. 
 
 Of the faculties called the five fenfes, fight is 
 without doubt the nobleft. The rays of light, 
 which minifter to this fenfe, and of which, with- 
 out it, we could never have had the leaft con- 
 ception, are the moft wonderful and aftonifhing 
 part of the inanimate creation. We muft be fa- 
 tisfied of this, if we confider their extreme mi- 
 nutenefs, their inconceivable velocity, the regular 
 variety of colours which they exhibit, the inva- 
 riable laws according to which they are acted up- 
 on by other bodies, in their reflexions, inflexi- 
 ons, 
 
Seft. i. Of SEEING. i 2t 
 
 ons, and refradbions, without the leaft change of 
 their original properties, and the facility with 
 which they pervade bodies of great denfity, and 
 oftheclofelt texture, without refiftance, without 
 crowding or difturbing one another, without gi- 
 ving the leaft fenfible impulfe to the lighteft bo- 
 dies. 
 
 The ftrutture of the eye, and of aH its appur- 
 tenances, the admirable contrivances, of nature for 
 performing all its various external and internal 
 motions, and the variety in the eyes of different 
 animals, fuited to their feveral natures and ways 
 of life, clearly demonftrate this organ to be a 
 mafterpiece of Nature's work. And he muft be 
 very ignorant of what hath been difcovered 
 about it, or have a very ftrange caft of underftand- 
 ing, who can ferioufly doubt, whether or not 
 the rays of light and the eye were made for one 
 another, with confummate wifdom, and perfect 
 fkill in optics. 
 
 If we lhall fuppofe an order of beings, en- 
 dued with every human faculty but that of fight, 
 how incredible would it appear to fuch beings, ac- 
 cuftomed only to the flow informations of touch, 
 that, by the addition of an organ^ confifting of a 
 ball and focket of an inch diameter, they might 
 be enabled in an inftant of time, without chan- 
 ging their place, to perceive the difpofition of a 
 whole army, or the order of a battle, the figure 
 of a magnificent palace, or all the variety'of a 
 landfeape ? If a man were by feeling to find out 
 the figure of the peak of TenerifFe, or even of 
 
 St. 
 
U2 OftheHUMAN MIND. Chap. YI. 
 St. Peter's church at Rome, it would be the work 
 of a lifetime. 
 
 It would appear ftill more incredible to fuch 
 beings as we have fuppofed, if they were inform- 
 ed of the difcoveries which may be made by this 
 little organ in things far beyond the reach of any 
 other fenfe : That by means of it we can find 
 our way in the pathlefs ocean ; that we can tra- 
 verfe the globe of the earth, determine its figure 
 and dimenfions, and delineate every region of it : 
 Yea, that we can meafure the planetary orbs, and 
 make difcoveries in the fphere of the fixed ftars. 
 
 Would it not appear ftill more aftonifhing to 
 4uch beings, if they {hould be farther informed, 
 That, by means of this fame organ, we can per- 
 ceive the tempers and difpofitions, the paffions 
 and affeolions of our fellow-creatures, even when 
 they want moft to conceal them ? That when 
 .the tongue is taught moft artfully to lie and dif- 
 fembie, the hypocrify fhould appear in the coun- 
 tenance to a difcernkig eye ? And that by this 
 organ, we can often perceive what is ftraight and 
 •what is crooked in the mind as well as in the 
 •body ? How many myfterious things mufta blind 
 man believe, if he will give credit to the rela- 
 tions of thofe that fee ? Surelv he needs as ftrona 
 a faith as is required of a good Chriftian. 
 
 It is not therefore without reafon, that the fa- 
 culty of feeing is looked upon, not only as more 
 noble than the other fenfes, but as having fome- 
 thing in it of a nature fuperior to fenfation. The 
 evidence of reafon is called feeing not feeling, 
 
 fondling* 
 
Sea. i. Of SEEING. 123 
 
 fuelling, or tafting. Yea, we are wont to exprefs 
 the manner of the divine knowledge by feeing, 
 as that kin4 of knowledge which is moft perfect 
 in us. 
 
 SECT. II. 
 
 Sight difcovers almoft nothing iiohich the blind may 
 not comprehend. The reafon of this. 
 
 "VTOtwithstanding what hath been, faid of 
 the dignity and fuperior nature of this 
 faculty, it is worthy of our obfervation, that 
 there is very little of the knowledge acquired 
 by fight, that may not be communicated to a 
 man born blind. One who never faw the light, 
 may be learned , and knowing in every fcience, 
 even in optics ; and may make difcoveries in 
 every branch Of philofophy. He may underftand 
 as much as another man, not only of the order, 
 diftances, and motions of the heavenly bodies ; 
 but of the nature of light, and of the laws of 
 the reflexion and refraction of its rays. He may 
 underftand diftindlly, how thofe laws produce 
 the phasnomena of the rain-bow, the prifm, the 
 camera obfcura, and the magic lanthorn, and all 
 the powers of the microfcope and telefcope. 
 This is a fact fufRciently attefted by experience. 
 In order to perceive the reafon of it, we mu(b 
 diftinguifh the appearance than objects make to 
 the eye, from the things fuggefted by that ap- 
 pearance : and again, in the vifible appearance 
 
 of 
 
ii4 Of the H U M A N M I N D. Chap. VI. 
 ef objects, we muft diftinguifh the appearance 
 of colour from the appearance of extenfion 
 figure, and motion. Firft, then, as to the vi- 
 sible appearance of the figure, and motion, and 
 extenfion of bodies, I conceive that a man born 
 blind may have a diftinct notion, if not of the 
 very things, at leaft of fomething extremely- 
 like to them. May not a blind man be made 
 to conceive, that a body moving directly from 
 the eye, or directly towards it, may appear to 
 be at reft ? and that the fame motion may ap- 
 pear quicker or flower, according as it is nearer 
 to the eye or farther off, more direct or more 
 oblique ? May he not be made to conceive, that 
 a plain furface, in a certain pofition, may appear 
 as a ftraight line, and vary its vifible figure, as 
 its pofition, or the pofition of the eye, is varied ? 
 That a circle feen obliquely will appear an ellipfe; 
 and a fquare, a rhombus, or an oblong rectangle ? 
 Dr. Saunderfon understood the projection of the 
 fphere, and the common rules of perfpective ; 
 and if he did, he mufl have underftood all that 
 I have mentioned. If there were any doubt of 
 Dr. Saunderfon's underftanding thefe things, I 
 could mention my having heard him fay in con- 
 verfarion, that he found great difficulty in under- 
 ftanding Dr. Halley's demonftration of that pro- 
 pofition, That the angles made by the circles 
 of the fphere, are equal to the angles made by 
 their reprefentatives in the ftereographic pro- 
 jection : but, faid he, when I laid afide that de- 
 monftration, and confidered the propofition in 
 
 my 
 
Sea. 2. Of S E E I N G. 125 
 
 my own way, I faw clearly that it muft be 
 true. Another gentleman, of undoubted credk 
 and judgment in thefe matters, who had part in 
 this converfation, remembers it diftinctly. 
 
 As to the appearance of colour, a blind man 
 muft be more at a lofs ; becaufe he hath ho per- 
 ception that refembles it. Yet he may, by a 
 kind of analogy, in part fupply this defect. To 
 thefe who fee, a fcarlet colour fignifies an un- 
 known quality in bodies,, that makes to the eye 
 an appearance, which they are well acquainted 
 with, and 'have often obferved : to a blind man, 
 it fignifies an unknown quality that makes to 
 the eye an appearance; which he is unacquaint- 
 ed with. But he can conceive the eye to be 
 varioufly affected by different colours, as the 
 nofe is by different fmelis, or the ear by dif- 
 ferent founds. Thus he can conceive fcarlet to 
 differ from blue,, as the found of a trumpet does 
 from that of a drum ; or as the frnell of an orange 
 differs from that of an apple. It is impoffible to 
 know whether a fcarlet colour has the fame ap- 
 pearance, to me which it hath to another man ; 
 and if the appearances of it to different perfons 
 differed as much as colour does from found, they 
 might never be able to difcover this difference. 
 Hence it appears obvious, that a blind man 
 might talk long about colours diftincfly and per- 
 tinently : and if you were to examine him in 
 the dark about the nature, compofition, and. 
 beauty of them, he might be able to anfwer, fo 
 as not to betray his defect. 
 
 We 
 
i 2 6 Of the HUM AN MIND. Chap. VI. 
 
 "We have ften how far a blind man may go in 
 the knowledge of the appearances which things 
 make to the eye. As to the thing3 which are fug- 
 gefted by them, or inferred from them ; altho* 
 he could never difcover them of himfelf, yet he 
 may understand them perfectly by the informa- 
 tion of others. And every thing of this kind 
 that enters into our minds by the eye, may en- 
 ter into his by the ear. Thus, for inftance, he 
 could never, if left to the direction of his own 
 faculties, have dreamed of any fuch thing as 
 light ; but he can be informed of every thing 
 we know about it. He can conceive, as di- 
 ftin&ly as we, the minutenefs and velocity of 
 its rays, their various degrees of refrangibility 
 and reflexibility, and all the magical powers and 
 virtues of that wonderful element. He could 
 never of himfelf have found out, that there are 
 fuch bodies as the fun, moon, and ftars ; but he 
 may be informed of all the noble difcoveries of 
 aftronomers about their motions, and the laws 
 of nature by which they are regulated. Thus 
 it appears, that there is very little knowledge 
 got by the eye, which may not be communicat- 
 ed by language to thofe who have no eyes. 
 
 If we fhould fuppofe, that it were as uncom- 
 mon for men to fee, as it is to be born blind ; 
 would not the few who had this rare gift, ap- 
 pear as prophets and infpired teachers to the 
 many ? We conceive, infpiration to give a man 
 no new faculty, but to communicate to him in 
 a new way, and by extraordinary means, what 
 
 the 
 
Scft. 2. Of S E E I N G. iiy 
 
 the faculties common to mankind can apprehend, 
 and what he can communicate to others by or- 
 dinary means. On the fuppofition we have 
 made, fight would appear to the blind very fi- 
 milar to this, for the few who had this' gift, 
 could communicate the knowledge acquired by 
 it to thofe who had it not. They could not in- 
 deed convey to the blind any diftinct notion of 
 the manner in which they acquired this know- 
 ledge. A ball and focket would feem, to a- 
 blind man, in this cafe^ as improper an inftru- 
 ment for acquiring fuch a variety and extent of 
 knowledge, as a dream or a vifion. The man- 
 ner in which a man who fees, difcerns fo many 
 things by means of the eye, is as unintelligible 
 to the blind, as the manner in which a man may 
 be infpired with knowledge by the Almighty, 
 - is to us. Ought the blind man therefore, with- 
 out examination, to treat all pretences to the 
 gift of Feeing as impofture ? Might he not, if he 
 were candid and tradable, find reafonable evi- 
 dence of the reality of this gift in others, and 
 draw great advantages from it to himfelf ? 
 
 The diftindion we have made between the 
 vifible appearances of the obje&s of fight, and 
 things fuggefted by them, is- necefiary to give 
 us a juft notion of the intention of nature in 
 giving us eyes. If we attend duly to the ope- 
 ration of our mind in the ufe of this faculty, we 
 fhall perceive, that, the vifible appearance of 
 objects is hardly ever regarded by us. It is not 
 at all made an objecY of thought or refle&ion, 
 
 but 
 
i 2 8 Ofthe HUM AN MIND. Chap. VI, 
 but ferves only as a fign to introduce to the mind 
 fomething elfe, which may be diftindtly concei- 
 ved by thofe who never faw. 
 
 Thus the vifible appearance of things- in my 
 room varies almoft every hour* according as the 
 day is clear or cloudy, as the fun is in the eaft s 
 or fouth, or weft, and as my eye is in one pare 
 of the room or in another : but I never think 
 of thefe variations, otherwife than as figns of 
 morning, noon, or night, of a clear or cloudy 
 fky. A book or a chair has a different appear- 
 ance to the eye, in every different diftance and 
 pofition ; yet we conceive it to be ftill the 
 fame •, and, overlooking the appearance, we im- 
 mediately conceive the real figure, diftance, and 
 pofition of the body, of which its vifible or per- 
 fpe&ive appearance is, a fign and indication. 
 
 "When I fee a man at the diftance of ten 
 yards, and afterwards fee him at the, diftance 
 of a hundred yards, his vifible appearance in its 
 length, breadth, and all its linear proportions, 
 is ten times lefs in the laft cafe than it is in the 
 firft : yet I do not conceive him one inch dimi- 
 nifhed by this diminution of his vifible figure. 
 Nay, 1 do not in the leaft attend to this diminu- 
 tion, even when I draw from it the conclufion 
 of his being at a greater diftance'. For fuch is 
 the fubtiky of the mind's operation in this cafe, 
 that we draw the conclufion, without perceiving 
 that ever the premifes entered into the mind. 
 A thoufand fuch inftances might be produced, 
 in order to fhew that the vifible appearances of 
 i objects 
 
Seft.2. Of SEEING. - 129 
 
 objects are intended by nature only as figns or 
 indications ; and that the mind paflfes inftantly 
 to the things fignified, without making the leaft 
 reflection upon the fign, or even perceiving that 
 there is any fuch thing. It is in a way fomewhat 
 fimilar, that the founds of a language, after it 
 is become familiar, are overlooked, and we at- 
 tend only to the things fignified by them. 
 
 It is therefore a juft and important obferva- 
 tion of the Bifhop of Cloyne, That the vifible 
 appearance of objects is a kind of language ufed 
 by nature, to inform us of their diftance, magni- 
 tude, and figure. And this obfervation hath 
 been very happily applied by that ingenious wri- 
 ter, to the folution of fome phenomena in optics, 
 which had before perplexed the greateft matters 
 in that fcience. The fame obfervation is further 
 improved by the judicious Dr. Smith", in his Op- 
 tics, for explaining the apparent figure of the hea- 
 vens, and the apparent diftances and magnitudes! 
 of objects feen with glaffes, or by the naked eye. 
 
 Avoiding as much as poffible the repetition of 
 what hath been faid by thefe excellent writers, 
 we fhall avail ourfelves of the diftindtion between 
 the figns that nature ufeth in this vifual language, 
 and the things fignified by them ; and in what 
 remains to be faid of fight, fhall firft make fome 
 obfervations upon the figns. 
 
 SECT. 
 
i 3 o Ofthe HUMAN MIND. Chap. VI. 
 
 SECT. III. 
 
 Of the vifible appearances of objefls. 
 
 J N this fedYion we muft fpeak of things which 
 are never made the object of reflexion, 
 tho' almoft every moment prefented to the mind. 
 Nature intended them only for figns ; and in the 
 whole courfe of life they are put to no other ufe. 
 The mind has acquired a confirmed and invete- 
 rate habit of inattention to them •, for they no 
 fooner appear, than quick as lightning the thing 
 fignified fucceeds, and ingrofles all our regard. 
 They have no name in language ; and altho' we 
 are confcious of them when they pafs through the 
 mind, yet their paflage is fo quick, and fo fami- 
 liar, that it is abfolutely unheeded ; nor do they 
 leave any footfteps of themfelves either in the 
 memory or imagination. That this is the cafe 
 with regard to the fenfations of touch, hath been 
 fhown in the lafl: chapter ; and it holds no lefs 
 with regard to the vifible appearances of objects. 
 I cannot therefore entertain the hope of being 
 intelligible to thofe readers who have nor, by 
 pains and practice, acquired the habit of diftin- 
 guifhing the appearance of objects to the eye, 
 from the judgment which we form by fight of 
 their colour, diftance, magnitude, and figure. 
 The only profeflion in life" wherein it is necefia- 
 ry to make this diftinclion, is that of painting. 
 Thepainter hath occafion for an abftraction, with 
 
 regard 
 
Seft. 3 . Of SEEING. i 5 t 
 
 regard to vifible objects, fomewhat fimilar to that 
 which we here require : and this indeed is the 
 moft difficult part of his art. For it is evident, 
 that if he could fix in his imagination the vifible 
 appearance ofobjecls, without confounding it with 
 the things fignified by that appearance, it would 
 be as eafy for him to paint from the life, and *x> 
 give every figure its proper fhading and relief, 
 and its perfpeclive proportions, as it is to paint 
 from a copy. Perfpeclive, lhading, giving re- 
 lief, and colouring, are nothing elfe but copying 
 the appearance which things make to the eye. 
 We may therefore borrow fome light on the fub- 
 jecT: of vifible appearance from this art. 
 
 Let one look upon any familiar object, fuch 
 as a book, at different diftanoes and in different 
 pofitions : is he not able to affirm, upon the 
 teftimony of his fight, that it is the fame book, 
 the fame object , whether feen at the diftance of 
 one foot or of ten, whether in one pofition or 
 another -, that the colour is the fame, the dimen- 
 fions the fame, and the figure the fame, as far as 
 the eye can judge ? This furely muft be acknow- 
 ledged. The fame individual objecl: is prefented 
 to the mind, only placed at different diftances, 
 and in different pofitions. Let me aflc, in the 
 next place, Whether this object has the fame ap- 
 pearance to the eye in thefe different diftaiices f 
 Infallibly it hath not. For, 
 
 Firft, However certain our judgment may be 
 
 that the colour is the fame, it is as certain that 
 
 it hath not the fame appearance at different 
 
 I 2 diftances. 
 
132 Of the HUMAN MIND. Chap. VI. 
 
 diftarices. There is a certain degradation of the 
 colour, and a certain confufion and indiftindtnefs 
 of the minute parts, which is the natural confe- 
 quence of the removal of the object to a greater 
 diftance. Thofethat are not painters, or critics 
 in painting, overlook this ; and cannot eafily be 
 perfuaded, that the colour of the fame object 
 hath a different appearance at the diftance of one 
 foot and often, in the made and in the light. 
 But the mailers in painting know how, by the de- 
 gradation of the colour, and the confufion of the 
 minute parts, figures, which are upon the fame 
 canvas, and at the fame diftance from the eye, 
 may be made to reprefent objects which are at the 
 moft unequal diftances. They know how to 
 make the objects appear to be of the fame colour, 
 by making their pictures really of different co- 
 lours according to their diftances or fhades. 
 
 Secondly, Every one who is acquainted with 
 the rules of perfpedtive, knows that the appear- 
 ance of the figure of the book muft vary in eve- 
 ry different pofition : yet if you afk" a man 
 that has no notion of perfpedtive, whether the 
 figure of it does not appear to his eye to be the 
 fame in all its different pofitions ? he can with a 
 good confcience affirm, that it does. He hath 
 learned to make allowance for the variety of 
 vifible figure arifing from the difference of pofi- 
 tion, and to draw the proper conclufions from it. 
 But he draws thefe conclufions fo readily and 
 habitually, as to lofe fight of the premifes : 
 and therefore where he hath made the fame 
 
 conclufion. 
 
Seel. 3. Of SEEING. i 33 
 
 conclufion, he conceives the vifible appearance 
 mult have been the fame. 
 
 Thirdly, Let us conlider the apparent magni- 
 tude or dimenfions of the book. Whether I 
 view it at the diftance of one foot or of ten feet, 
 it feems to be about feven inches long, five 
 broad, and one thick. I can judge of thefe di- 
 menfions very nearly by the eye, and I judge 
 them to be the fame at both diftances. But yet 
 it is certain, that at the diftance of one foot its 
 vifible length and breadth is about ten times as 
 great as at the diftance of ten feet ; and confe- 
 quently its furface is about a hundred times as 
 great. This great change of apparent magni- 
 tude is altogether overlooked, and every man is 
 apt to imagine, that it appears to the eye of the 
 fame fize at both diftances. Further, when I 
 look at the book, it feems plainly to have three 
 dimenfions, of length, breadth, and thicknefs : 
 but it is certain that the vifible appearance hath 
 no more than two, and can be exactly reprefent- 
 ed upon a canvas which hath only length and 
 breadth. 1 
 
 In the laft place, Does not every man, by 
 fight perceive the diftance of the book from his 
 eye ? Can he not affirm with certainty, that in 
 one cafe it is not above one foot diftant, that in 
 another it is ten ? Neverthelefs it appears certain, 
 that diftance from the eye, is no immediate ob- 
 ject of fight. There are certain things in the 
 vifible appearance which are figns of diftance 
 from the eye, and from which, as we Ihall after- 
 I 3 wards 
 
r 3 4 Of the H U M A N M I N D. Chap. VI. 
 wards (how, we learn by experience to judge of 
 that diftance within certain limits ; but it feems 
 beyond doubt, that a man born blind, and fud- 
 denly made to fee, could form no judgment 
 at firft of the diftance of the objects which he 
 faw. The young man couched by Chefelden, 
 thought, at firft, that every thing he faw touch- 
 ed his eye, and learned only by experience to 
 judge of the diftance of vifible objects. 
 
 I have entered into this long detail, in order 
 to (hew, that the vifible appearance of an object 
 is extremely different from the notion of it which 
 experience teaches us to form by fight ; and to 
 enable the reader to attend to the vifible appear- 
 ance of colour, figure, and extenfion, in vifi- 
 ble things, which is no common object of 
 thought, but muft be carefully attended to by 
 thofe who would enter into the philofophy of 
 this fenfe, or would comprehend what fhall be 
 faid upon it. To a man newly made to fee, the 
 vifible appearance of objects would be, the fame 
 as to us ; but he would fee nothing at all of their 
 real dimenfions, as we do. He could form no 
 conje<5lure, by means of his fight only, how ' 
 many inches orfeet they were in length, foreadth, 
 or. thick nefs. He could perceive little or no- 
 thing of their real figure.; nor could he difcern, 
 that this was a cube, that a fphere ; that this 
 Was a cone, and that a cylinder. - His eye 
 could not inform him, that this object was near, 
 and that more remote. The habit of a man or 
 of a woman, which appeared to us of one uni- 
 form 
 
Seel. 3. Of SEEING. i 35 
 
 form colour, varioufly folded and fhaded, would 
 prefent to his eye neither fold nor fhade, but 
 variety of colour. In a word, his eyes, tho' 
 ever fo perfect, would at firft give him almoft 
 no information of things without him. They 
 would indeedprefent the fame appearances to him 
 as they do to us, and fpeak the fame language ; 
 but to him it is an unknown language ; and 
 therefore he would attend only to the figns, 
 without knowing the fignification of them : 
 whereas to us it is a language perfectly familiar j 
 and therefore we take no notice of the figns, but 
 attend only to the thing fignified by them. 
 
 SECT. IV. 
 
 'That colour is a quality of bodies, not a fenfation 
 of the mind. 
 
 TJ Y colour, all men, who have not been tutor- 
 ed by modern philofophy, underftand, not 
 a fenfation of the mind, which can have no ex- 
 iftence when it is not perceived, but a quality 
 or modification of bodies, which continues to- 
 be the fame, whether it is f en or not. The 
 fcarlet-rofe, which is before me, is ftill a fcarlet- 
 rofe when I fhut my eyes, and was fo at mid- 
 night when no eye faw it. The colour re- 
 mains when the appearance ceafes : it remains 
 the fame when the "appearance changes. For 
 when I view this fcarlet-rofe through a pair of 
 green fpeftacles, the appearance is changed, but 
 I 4 I do 
 
136 Of the H UMA NMIND. Chap. VI. 
 I do not conceive the colour of the rofe changed. 
 To a perfon in the jaundice, it has ftill another 
 appearance ; but he is eafily convinced, that the 
 change is in his eye, and not in the colour of 
 the object. Every different degree of light 
 makes it have a different appearance, and total 
 darknefs takes away all appearance, but makes 
 not the leaft change in the colour of the body. 
 We may, by a variety of optical experiments, 
 change the appearance of figure and magnitude 
 in a body, as well as that of colour •, we may 
 make one body appear to be ten. But all men 
 believe, that as a multiplying glafs does not 
 really produce ten guineas out of one, nor a mi- 
 crofcope turn a guinea into a ten pound piece ; 
 fo neither does a coloured glafs change the real 
 colour of the object feen thro' it, when it chan- 
 ges the appearance of that colour. 
 
 The common language of mankind mows evi- 
 dently, that we ought to diftinguifh between the 
 colour of a body, which is conceived to be a fix- 
 ed and permanent quality in the body, and the 
 appearance of that colour to the eye, which may 
 be varied a thoufand ways, by a variation of the 
 light, of the medium, or of the eye itfelf. The 
 permanent colour of the body is the caufe, which, 
 by the mediation of various kinds or degrees of 
 light, and of various tranfparent bodies interpo- 
 fed, produces all this variety of appearances. 
 "When a coloured body is prefented, there is a 
 certain apparition to the eye, or to the mind, 
 which we have called the appearance of colour. 
 
 ' Mr. 
 
Seft. 4 . Of SEEING. 137 
 
 Mr. Locke calls it an idea ; and indeed it may be 
 called fo with the greateft propriety. This idea 
 can have no exiftence but when it is perceived. 
 It is a kind of thought, and can only be the aft 
 of a percipient or thinking being. By the con- 
 ftitutionof our nature, we are led to conceive 
 this idea as a fign of fomething external, and are 
 impatient till we learn its meaning. A thoufand 
 experiments for this purpofe are made every day 
 by children, even before they come to the ufe of 
 reafon. They look at things, they handle them, 
 they put them in various pofitions, at different 
 diftances, and in different lights. The ideas of 
 fight, by thefe means, come to be aflbciated with, 
 and readily to fuggeft, things external, and alto- 
 gether unlike them. In particular, that idea which 
 we have called the appearance of colour, fuggefts 
 the conception and belief of fome unknown qua- 
 lity in the body, which occafions the idea ; and 
 it is to this quality, and not to the idea, that we 
 give the name of colour; The various colours, 
 although in their nature equally unknown, are 
 eafily diftinguifhed when we think or fpeak of 
 them, by being aflbciated with the ideas which 
 they excite. In like manner, gravity, magnetifm, 
 and eleftricity, although all unknown qualities, 
 are diftinguifhed by their different effects. As 
 we grow up, the mind acquires a habit of pafling 
 fo rapidly from the ideas of fight to the external 
 things fuggefted by them, that the ideas are not 
 in the leaft attended to, nor have they names gi- 
 ven them in common language. 
 
 When 
 
i 3 8 Of the H U M A N M I N D. Chap. VI. 
 
 When we think or fpeak of any particular co- 
 lour, however fimple the notipn may feem to be, 
 which is prefented to -the imagination, it is really 
 in fome fort compounded. It involves an un- 
 known caufe, and a known effect. The name of 
 colour belongs indeed to the caufe only, and not 
 to the effect. But as the caufe is unknown, we 
 can form no diftinct conception of it, but by its 
 relation to the known effect. And therefore both 
 go together in the imagination, and are fo clofely 
 united, that they are miftaken for one fimple 
 object of thought. When I would conceive thofe 
 colours of bodies which we call fcarlet and blue ; 
 if 'I conceived them only as unknown qualities, 
 I could perceive no diftinction between the one 
 and the other. I muft therefore, for the fake of 
 diftinetion, join to each of them in my imagi- 
 nation fome effect or fome relation that is pecu- 
 liar. And the moil obvious diftincTion is, the ap- 
 pearance which one and the other makes to the 
 eye. Hence the appearance is, in the imagina- 
 tion, fo clofely united with the quality called a 
 fearkt-colour, that they are apt to be miftaken 
 for one and the fame thing, altho' they are in 
 reality fo different and fo unlike, that one is ah 
 idea in the mind, the other is a quality of body. 
 
 I conclude then, that colour is not a fenfation, 
 but a fecondary quality of bodies, in the fenfe 
 we have already explained ; that it is a certain 
 power or virrue in bodies, that in fair day-light 
 exhibits to the eye an appearance, which is very 
 familiar to us, although it hath no name. Co- 
 lour 
 
Seft. 4- Of SEEING. 139 
 
 lour differs from other fecond,ary qualities in this, 
 that whereas the name of the quality is fome- 
 times given to the fenfation which indicates it* 
 and is occafioned by it, we never, as far as I can 
 judge, give the name of colour to the fenfation, 
 but to the quality only. Perhaps the reafon of 
 this may be, that the appearances of the fame co- 
 lour are fo various and changeable, according to 
 the different modifications of the light, of the 
 medium, and of the eye, that language could not 
 afford names for them. And indeed they are fo 
 little intereftirig, that they are never attended to, 
 but ferve only as figns to introduce the things 
 fignified by them. Nor ought it to appear incre- 
 dible, that appearances fo frequent and fo familiar 
 fhould have no names, nor be made objects of 
 thought ■, fince we have before fhown, that this 
 is true of many fenfations of touch, which are no 
 lefs frequent, nor lefs familiar. 
 
 SECT. V. 
 
 An inference from the ■preceding: 
 
 Tp R O M what hath been faid about colour, we 
 may infer two things. The firft is, that one 
 of the moft remarkable paradoxes of modern phi- 
 lofophy, which hath been univerfally efteemed as 
 a great difcovery, is, in reality, when examined 
 to the bottom, nothing elfe but an abufe of 
 words. The paradox I mean is, That colour is, 
 not a qualijy of bodies, but only an idea in the 
 
 mind. 
 
140 Of the H U M A N M I N D. Chap. VI.' 
 mind. We have fhown, that the word colour, as 
 ufed by the vulgar, cannot fignify an idea in the 
 mind, but a permanent quality of body. We have 
 ihown, that there is really a permanent quality of 
 body, to which the common ufe of this word ex- 
 actly agrees. Can any ftronger proof be defired, 
 that this quality is that to which the vulgar give 
 the name of colour? If it fhould be faid, that this 
 quality, to which we give the name of colour, is 
 unknown to the vulgar, and therefore can have 
 no name among them ; I anfwer, it is indeed 
 known only by its effe&s ; that is, by its exci- 
 tino- a certain idea in us : but are there not num- 
 berlefs qualities of bodies which are known only 
 by their effects, to which, notwithftanding, we 
 find it neceffary to give names ? Medicine alone 
 might furnifh us with a hundred inftances of this 
 kind. Do not the words afiringent, narcotic, 
 epifpaftic, cauflic, and innumerable others, fignify 
 qualities of bodies which are known only by their 
 effects upon animal bodies ? Why then mould not 
 the vulgar give a name to a quality, whofe ef- 
 fects are every moment perceived by their eyes ? 
 We have all the reafon therefore that the nature 
 of the thing admits, to think that the vulgar ap- 
 ply the name of colour to that quality of bodies 
 which excites in us what the philofophers call the 
 idea of colour. And that there is fuch a quality 
 in bodies, all philofophers allow, who allow that 
 there is any fuch thing as body. Philofophers 
 have thought fit to leave that quality of bodies 
 which the vulgar call colour, without a name, 
 
 and 
 
Sett. 5. Of S E E I N G. * 4 i 
 
 and to give the name, of colour to the idea or ap- 
 pearance, to which, as we have fhown, the vul- 
 gar give no name, becaufe they never make it an 
 objec"b of thought or reflection. Hence it appears, 
 that when philofophers affirm that colour is not 
 in bodies, but in the mind -, and the vulgar af- 
 firm, that colour is not in the mind, but is a qua- 
 lity of bodies ; there is no difference between 
 them about things, but only about the meaning 
 of a word. 
 
 The vulgar have undoubted right to give 
 names to things which they are daily converfant 
 about; and philofophers feem juftly chargeable 
 with an abufe of language, when they change the 
 meaning of a common word, without giving 
 warning. 
 
 If it is a good rule, to think with philofophers, 
 and fpeak with the vulgar, it muft be right to 
 fpeak with the vulgar when we think with them, 
 and not to (hock them by philofophical paradoxes, 
 which, when put into common language, exprefs 
 only the common fenfe of mankind. 
 
 If you alk a man that is no philofopher, what 
 colour is ? or, what makes one body appear white, 
 another fcarlet ? He cannot tell. He leaves that 
 inquiry to philofophers, and can embrace any hy- 
 pothefis about it, except that of our modern phi- 
 lofophers, who affirm, that colour is not in body, 
 but only in the mind. 
 
 Nothing, appears more fhocking to his appre- 
 
 .henfion, than that vifible objects lhould have no 
 
 colour, and that colour fhould be in that which 
 
 7 he 
 
i 4 2 Of the HUMAN MIND. Chap. VI. 
 he conceives to be invjlible. Yet this ftrange pa- 
 radox is not only univerfally received, but confi- 
 . dered as one of the nobleft difcoveries of modern 
 philofophy. The ingenious Addifon, in the Spec- 
 tator, N°4i:$. fpeaks thus of it. " I have here 
 " fuppofed that my reader is acquainted with 
 " that great modern difcovery, which is at pre- 
 " fent univerfally acknowledged by all the in- 
 *' quirers into natural philofophy, namely, that 
 " light and colours, as apprehended by the ima- 
 " gination, are only ideas in the mind, and not 
 " qualities that have any exiftence in matter. 
 " As this is a truth which has been proved in- 
 " conteftably by many modern philofophers, and 
 " is indeed one of the fineft fpeculations in that 
 " fcience, if the Englifh reader would fee the no- 
 " tion explained at large, he may find it in the 
 " eighth chapter of the fecond book of Locke's 
 " EJfay on human underftanding." 
 
 Mr. Locke and Mr. Addifon are writers who 
 have deferved fo well of mankind, that one muft 
 feel fome uneafinefs in differing from them, and 
 would wifh to afcribe all the merit that is due to 
 a difcovery upon which they put fo high a va- 
 lue. And indeed it is juft to acknowledge, that 
 Locke, and other modern philofophers, on the 
 fubject of fecondary qualities, have the merit of 
 diftinguifhing more accurately than thofe that 
 went before them, between the fenfation in the 
 mind, and that conftitution or quality of bodies 
 which gives occafion to the fenfation. They 
 have (hown clearly, that thtfe two things are 
 
 not 
 
Sea. 5. Of SEEING. 143 
 
 flot only diftinet, but altogether unlike: that 
 there is no fimilitude between the effluvia of an 
 odorous body, and the fenfation of frneil, or be- 
 tween the vibrations of a founding body ? and the 
 (enfation of found : that there can be no refem- 
 blance between the feeling of heat, and the con- 
 ftitution of the heated body which occafions it ; 
 or between the appearance which a coloured body 
 makes to the eye, and the texture of the body 
 which caufes that appearance. 
 
 Nor was the merit fmall of diftinguifhing 
 thefe things accurately •, becaufe, however dif- 
 ferent and unlike in their nature, they have been 
 always fo affociated in the imagination, as to 
 coalefce, as it were into one two-faced form, 
 Which, from its amphibious nature, could not 
 juftly be appropriated either to body or mind ; 
 and until it was properly diftinguifhed into its 
 different conftituent parts, it was impoflible to 
 aflign to either their jult mares in it. None of 
 the ancient philolbphers had made this diftinc- 
 tion. The followers of Democritus and Epi- 
 curus conceived the forms of heat, and found, 
 and colour, to be in the mind only, but that 
 our fenfes fallaciouQy reprefented them as beinc 
 in bodies. The Peripatetics imagined, that 
 thofe forms are really in bodies ; and that the 
 images of them are conveyed to the mind by our 
 fenfes. 
 
 The one fyftem made the fenfes naturally fal- 
 lacious and deceitful; the other made the qua- 
 lities of body to referable the fenfations of the 
 
 mind. 
 
144 Of the HUMAN MIND. Chap. VI, 
 mind. Nor was it poffible to find a third, with- 
 out making the diftindtion we have mentioned ; 
 by which indeed the errors of both thefe ancient 
 fyftems are avoided, and we are not left under 
 the hard neceffity of believing, either, on the 
 one hand, that our fenfations are like to the 
 qualities of body, or, on the other, that God 
 hath given us one faculty to deceive us, and an- 
 other to detect the cheat. 
 
 We defire therefore, with pleafure, 1 to do 
 juftice to the doctrine of Locke, and other 
 modern philofophers, with regard to colour, 
 and other fecondary qualities, and to afcribe to 
 it its due merit, while we beg leave to cenfure 
 the language in which they have exprefled their 
 doctrine. When they had explained and efta- 
 blifhed the diftinction between the appearance 
 which colour makes to the eye, and the modifica- 
 tion of the coloured body, which, by the laws of 
 Nature, caufes that appearance ; the queftion 
 was* Whether to give the name of colour to the 
 caufe, or to the effect ? By giving it, as they 
 have done, to tlje effect, they fet philofophy 
 apparently in oppofition to common fenfe, and 
 expofe it to the ridicule of the vulgar. But had 
 they given the name of colour to the caufe, as 
 they ought to have done, they muff then have 
 affirmed, with the vulgar, that colour is a qua- 
 lity of bodies ; and that there is neither colour 
 nor any thing like it in the mind. Their lan- 
 guage, as well as their fentiments, would have 
 been perfectly agreeable to the common appre- 
 
 henfions 
 
Sefl:. 5. Of S E E I N G. 145 
 
 henfions of mankind, and true philofophy would 
 have joined hands with Common Senfe. As 
 Locke was no enemy to common fenfe, it may- 
 be prefumed that, in this inftance, as in fome 
 others, he was feduced by fome received hypo- 
 thecs : and that this was actually the cafe, will 
 appear in the following feftion. 
 
 SECT. VI. 
 
 That none of our fenfations are refemblances of any 
 of the qualities of bodies. 
 
 A Second inference is. That altho' colour 
 is really a quality of body, yet it is not re- 
 prefented to the mind by an idea or fenfation 
 that refembles it} on the contrary, it is fug- 
 gefted by an idea which does not in the leaft 
 refemble it. And this inference is applicable, 
 not to colour only, but to all the qualities of 
 body which we have examined. 
 
 It deferves to be remarked, that in the ana- 
 lyfis we have hitherto given of the operations of 
 the five fenfes, and of the qualities of bodies 
 difcovered by them, no inftance hath occurred, 
 either of any fenfation which refembles any qua- 
 lity of body, or of any quality of body whofe 
 image or refemblance is conveyed to the mind 
 by means of the fenfes. 
 
 There is no phenomenon in nature more un- 
 accountable, than the intercourfe that is carriecl 
 on between the mind and the external world : 
 K there 
 
146 Ofthe HUMAN MIND. Chap. VI. 
 there is no phenomenon which philofophical fpi- 
 rits have fhown greater avidity to pry into, and to 
 refblve, It is agreed by all, that this intercourfe 
 is carried on by means of the fenfes : and this 
 fatisfies the vulgar curiofity, but not the philofo- 
 phic. Philofophers muft have fome fyftem, 
 fome hypothefis, that Ihews the manner in which 
 our fenfes make us acquainted with external 
 things. All the fertility of human invention 
 feems to have produced only one hypothefis 
 for this purpofe; which therefore hath been 
 uniyerfally received ; and that is, that the mind, 
 like a mirror, receives the images of things 
 from without, by means of the fenfes ; fo that 
 their ufe muft be to convey thefe images into 
 the mind. 
 
 Whether to thefe images of external things 
 in the mind we give the name of fenfible forms, 
 or fenfible fpecies, with the Peripatetics, or the 
 name of ideas of fenfatiori, with Locke ; or whe- 
 ther, with later philofophers, wediftinguifby^a- 
 fations, which are immediately conveyed by the 
 fenfes, from ideas of fenfation, which are faint 
 copies of our fenfations retained in the memory 
 and imagination ; thefe are only differences about 
 words. The hypothefis I have mentioned is 
 common to all thefe different fyftems. 
 
 The neceffary and allowed confequence of 
 this hypothefis is, That no material things nor 
 any quality of material things, can be conceiv- 
 ed by us, or made an object of thought, until 
 its image is conveyed to the mind by means 
 6 of 
 
SZ&. 6. Of S E E 1 U G< i 47 
 
 of the ferifes. We fhall examine this hypothefis 
 particularly afterwards, and at this time only 
 obferve, that in confequence of it, one would na- 
 turally expect, that to every quality and attri- 
 bute of body we know or can conceive, there 
 lhould be a fenfation correfponding, which is 
 the image and refemblance of that quality ; and 
 that the fenfations which have no fimilitude or 
 refemblance to body, or to any of its qualities, 
 lhould give us no conception of a material world*, 
 or of any thing belonging to it. Thefe things 
 might be expected as the natural confequences of 
 the hypothefis we have mentioned. 
 
 Now, we have confidered, in this and the 
 preceding chapters, extenfion, figure, folidify* 
 motion, hardnefs, rough nefs, as well as colour, 
 heat, and cold, found, tafte, and fmell. We 
 have endeavdurect to fhew, that our nature and 
 conftitution lead us to conceive thefe as qualities 
 of body, as all mankind have always conceived 
 them to be. We have likewife examined, with 
 great attention, the various fenfations we have 
 by means of the five fenfes, and are hot able to 
 find among them all one fingle. image of body, 
 or of any of its qualities. From whence then 
 come thofe images of body and of its qualities 
 into the mind? Let philofophers refolve this 
 queftion. All I can fay is, that they come not 
 by the fenfes. I' am fure, that, by proper at- 
 tention and care, I may know my fenfations, 
 and be able to, affirm with' certainty'what they 
 refemble, and what they do not refemble. I 
 K 2 have. 
 
i 4 8 OftheHUMAN MIND. Chap.VL 
 have examined them one by one, and compared 
 them with matter and its qualities; and I cannot 
 find one of them that confefles a refembling 
 
 feature. 
 
 A truth fo evident as this, That our fenfa- 
 tions are not images of matter, or of any of its 
 qualities, ought not to yield to a hypothefis 
 fuch as that above mentioned, however ancient, 
 or however univerfally received by philofophers ;, 
 nor can there be any amicable union between, 
 the two. This will appear by fome reflexions, 
 upon the fpirit of the ancient and modern philo- 
 fophy concerning fenfation. 
 
 During the reign of the Peripatetic philofo- 
 phy, our fenfations were not minutely or accis- 
 rately examined. The attention of philofophers, 
 as well as of the vulgar, was turned to the things 
 fignified by them : therefore, in conlequence of 
 the common hypothefis, it was taken for granted, 
 that all the fenfations . we have from external" 
 things, are the forms or images of thefe external 
 things. And thus the truth we have mentioned 
 yielded entirely to the hypothefis, and was alto- 
 gether fupprefied by it. 
 
 Des Cartes gave a noble example of turning 
 our attention inward, and fcrutinizing our fen- 
 fations ; and this example hath been very wor- 
 thily followed by modern philofophers, particu- 
 larly by Malebranch.e, Locke, Berkeley, and 
 Hume. The effect of this fcrutiny hath been, 
 a gradual difcovery of the truth above mention- 
 ed, to wit, the diffimilitude between the fen- 
 
 ' fations 
 
Seft. 6. Of SEEING. 149 
 
 fations of pur minds and the qualities or attri- 
 butes of an infentient, inert fubftance, fuch as 
 we conceive matter to be. But this valuable and 
 ufeful difcovery, in its different ftages, hath ftill 
 been unhappily united to the ancient hypothe- 
 fis : and from this inauipicious match of opinions, 
 fo Unfriendly and difcordant in their natures, 
 have arifen thofe monfters of paradox and fcep- 
 ticifm with which the modern philofophy is too 
 juft'ly chargeable. 
 
 Locke faw clearly, and proved inconteftably, 
 th3t the fenfations we have by tafte, fmell, and 
 hearing, as well as the fenfations of colour, heat, 
 and cold, are not refemblances of any thing in 
 bodies ; and in this he agrees with Des Cartes 
 and Malebranche. Joining this opinion with 
 the hypothefis, it follows necefiarily, that three 
 fenfes of the 'five are cut off from giving us any 
 intelligence of the material world, as being alto- 
 gether inept for that office. Smell, and tafte, 
 and found, as well as colour and heat, can have 
 no more relation to body, than anger or grati- 
 tude ; nor ought the former to be called qualities 
 of body, whether "primary or fecondary, any 
 more than the latter. For it was natural and 
 obvious to argue thus from that hypothefis : If 
 heat, and colour, and found, are real qualities of 
 body, the fenfations by which we perceive them, 
 mutt be refemblances of thofe qualities; but 
 thefe fenfations are not refemblances j therefore 
 thofe are not real qualities of body. 
 
 K 3 We 
 
i S o Of the HUMAN MIND, Chap. VI, 
 
 We fee then, that Locke, having found that 
 the ideas of fecondary qualities are no refembjan^ 
 ces, was compelled, by a hypothecs common to 
 all philofophers, to deny that they are real qua- 
 lities of body. It is more difficult to afilgn a 
 reafon, why, after this, he mould call them fecon- 
 dary qualities ; for this. name, if I miftake not, 
 was of his invention. Surely he did not mean 
 that they were fecondary qualities of the mind ; 
 and I do not fee with what propriety, or even by 
 what tolerable licence, he could call them fecon- 
 dary qualities of body, after finding that they 
 were no qualities of body at all. In this., he 
 feems to have facrificed to Common Senfe, and 
 to have been led by her authority even in oppo- 
 fition to his hypothefis. The fame fovereign 
 miftrefs of our opinions that led this phjlofopher 
 to call thofe things fecondary qualities of body, 
 which, according.to his principles and reafonings, 
 were no qualities of body at all, hath led, not 
 the vulgar of all ages only, but philofophers al- 
 fo, and even the difciples of Locke, to believe 
 them to be real qualifies of body : fhe hath led 
 them to inveftigafe, by experiments, the nature 
 pf colour, and "found, and hear, in bodies. 
 Nor hath this inveftigation been fruitlefs, as it 
 muft ruve been, if there had been no fuch thing 
 in bodies : on the contrary, it hath produced ve- 
 ry noble and ufeful difcoveries, which make a 
 vecy considerable part of natural philofophy. If 
 then natural philofophy be not a dream, there is 
 fornething in bodies, which we call colour, and 
 
Sed. 6. Of SEEING. i 5 i 
 
 heat, and found. And if this be fo, the hypo- 
 thefis from which the contrary is concluded, muft 
 be falfe : for the argument, leading to a falfe 
 conclulion, recoils againft the hypothefis from 
 which it was drawn, and thus directs its force 
 backward. If the qualities of body were 
 known to us only by fenfations that refemble 
 them, then colour, and found, and heat, could be 
 no qualities of body; but thefe are real qualities 
 of body; and- therefore the qualities of body 
 are not known only by means of fenfations that 
 refemble them. 
 
 But to proceed : What Locke had proved 
 with regard to the fenfations we have by fmell, 
 tafte, and hearing, Bifhop Berkeley proved no lefs 
 unanfwerably with regard to all our other fenfa^- 
 tions ; to wit, that none of them can in the 
 leaft refemble the qualities of a lifelefs and infen- 
 tient being, fuch as matter is conceived to be. 
 Mr. Hume hath confirmed this by his authority 
 and reafoning. This opinion furely looks with 
 a very malign afpecT: upon the old hypothefis ; 
 yet that hypothefis hath frill been retained, and 
 conjoined with it. And what a brood of mo'n- 
 fters ha'h this produced ! 
 
 The firft-born of this union, and perhaps the 
 moft harmlefs, was, That the fecondary quali- 
 ties of body were mere fenfations of the mind. 
 To pafs by Malebranche's notion of feeing all 
 things in the ideas of the divine mind, as a fo- 
 reigner never naturalized in this ifland ; the 
 next was Berkeley's fyftem, That extenfion, 
 K 4 and 
 
i 5 2 OftheHUMAN MIND. Chap. VI. 
 and figure, and hardnefs, and motion ; that land, 
 and fea, and houfes, and our own bodies, as 
 well as thofe of our wives, and children, and 
 friends, are nothing but ideas in the mind ; and 
 that there is nothing exifting in nature, but 
 minds and ideas. 
 
 The progeny that followed, is ftill more 
 frightful ; fo that it is furprifing, that one could 
 befonnd who had the courage to act the midwife, 
 to rear it up, and to ulher it into the world. 
 No caufes nor 'effects ; no fubftances, material 
 orfpiritual; no evidence even in mathematical 
 dernonftration ; no liberty nor active power ; 
 nothing exifting in nature, but impreffions and 
 ideas following each other, without time, place, 
 or fubject. Surely no age ever produced fuch a 
 fyftem of opinions, juftly deduced with great 
 acutenefs, perfpicuity, and eleganc'e, from a 
 principle univerfally received. The hypothefis 
 we have mentioned, is the father of them all. 
 The diffimilitude of our fenfations and feelings 
 to external things, is the innocent mother of 
 moft of them. 
 
 As it happens fometimes in an arithmetical 
 operation, that two errors balance one another, 
 fo that the conclufion is little or nothing affect- 
 ed by them •, but when one of them is corrected, 
 and the other left, we are led farther from the 
 truth, than by both together : fo it feems to 
 have happened in the Peripatetic philofophy of 
 fcnfation, compared with the modern. The 
 Peripatetics adopted two errors j but the laft fer- 
 
 ved 
 
Seft. 6. Of seeing: i 55 
 
 ved as a corrective to the firft, and rendered it 
 mild and gentle ; fa that their fyftem had no 
 tendency to fcepticifm. The moderns have re- 
 tained the firft of thofe errors, but have gradual- 
 ly detected and corre&ed the laft. The confe- 
 quence hath been, that the light we have ftruck 
 out hath created darknefs, and fcepticifm hath 
 advanced hand in hand with knowledge, fpread- 
 ing its melancholy gloom, firft over the material 
 world, and at laft over the whole face of na- 
 ture. Such a phenomenon as this, is apt to 
 ftagger even the lovers of light and knowledge, 
 while its caufe is latent; but when that is detect- 
 ed, it may give hopes, that this darknefs fhall 
 not be everlafting, but that it fhall be fucceeded 
 by a more permanent light. 
 
 SECT. VII. 
 
 Of vijibk figure and extenjion. 
 
 A Lthough there is no refemblance, nor, as 
 far as we know, any neceffary connection, 
 between that quality in a body which we call 
 its colour, and the appearance which that colour 
 makes to the eye ; it is quite otherwife with re- 
 gard to its figure and magnitude. There is cer- 
 tainly a refemblance, and a neceffary connection, 
 between the vifible figure and magnitude of a 
 body, and its real figure and magnitude ; no man 
 can give a reafon why a fcarlet colour affects the 
 eye in the manner it does ; no man can be fure, 
 
 that 
 
154 Of the HUMAN MIND. Chap. VI. 
 that it affects his eye in the fame manner as it 
 affects the eye of another, and that it has the 
 fame appearance to him, as it has to another 
 man ; but we can affign a reafon why a circle 
 placed obliquely to the eye, fhould appear in the 
 form of an ellipfe. The vifible figure, magni- 
 tude, and pofition, may, by mathematical rea- 
 foning, be deduced from the real ; and it may be 
 demonftrated, that every eye that fees diftindtly 
 and perfectly, muft, in the fame fituation, fee 
 it under this form, and no other. Nay, we may 
 venture to affirm, that a man born blind, if he 
 were , inftrudted in mathematics, would be able 
 to determine the vifible figure of a body, when 
 its real figure, diftance, and pofition, are given. 
 Dr. Saunderfon understood the projection of the 
 fphere, and perfpedtive. Now I require no 
 more knowledge in a blind man, in order to his 
 being able to determine the Vifible figure of bo- 
 dies, than that he can project the outline of a 
 given body, upon the furface of a hollow fphere, 
 whofe centre is in the eye. This projection is 
 the vifible figure he wants ; for it is the fame 
 figure with that which is projected upon the tu-< 
 pea retina in vifion, 
 
 A blind man can conceive lines drawn from 
 every point of the object to the centre of the 
 eye, making angles. He can conceive, that 
 the length of the object will appear greater or 
 lefs, in proportion to the angle which it fub- 
 tends at the eye •, and that, in like manner, the 
 breadth, and in general the diftance of any one 
 
 pojnt 
 
Seft. 7. Of S E E I N G. 155 
 
 point of the object from any other point, will ap- 
 pear greater or lefs, in proportion to the angles 
 which thofe diftances fubtend. He can eafily be 
 made to conceive, that the vifible appearance has 
 no thicknefs, 'any more than a projection of the 
 fphere, or a perfpedtive draught. He may be 
 informed, that the eye, until it is aided by ex- 
 perience, does not reprefent one object as nearer 
 or more remote than another. Indeed he would 
 probably conjecture this of himfelf, and be apt 
 to think that the rays of light muft make the 
 fame impreffion upon the eye, whether they 
 come from a greater or a lefs diftance. 
 
 Thefe are all the principles which we fuppofe 
 our blind mathematician to have ; and thefe he 
 may certainly acquire by information and reflec- 
 tion. It is no lefs certain, that from thefe prin- 
 ciples, having given the real figure and magni- 
 tude of a body, and its pofition and diftance with 
 regard to the eye, he can find out its vifible fi- 
 gure and magnitude. He can demonftrate in ge- 
 neral, from thefe principles, that the vifible fi- 
 gure of all bodies will be the fame with that of 
 their projection upon the furface of a hollow 
 fphere, when the eye is placed in the centre. 
 And he can demonftrate, that their vifible magr 
 nitude will be greater or lefs, according as their- 
 projection occupies a greater or lefs part of the 
 furface of this fphere. 
 
 To fetthis matter in another light, let us dif- 
 tinguifh betwixt the pofition of objectij with re-? 
 gard to the eye, and their d$am;e from it. Ob- 
 jects, 
 
i S 6 Of the HU M A N M I N D. Chap. VI. 
 je£ts that lie in the fame right line drawn from 
 the centre of the eye, have the fame pofition, 
 however different their diftances from the eye 
 may be : but objects which lie in different right 
 lines drawn from the eye's centre, have a differ- 
 ent pofition -, and this difference of pofition is 
 greater or lefs in proportion to the angle made 
 at the eye by the right lines mentioned. Ha- 
 ving thus defined what we mean by the pofition 
 of objects with regard to the eye, it is evidenr, 
 that as the real figure of a body confifts in the 
 fituation of its feveral parts with regard to one 
 another, fo its vifible figure confifts in the pofition 
 of its feveral parts with regard to the eye; and 
 as he that hath a diftinct conception of the fitu- 
 ation of the parts of the body with regard to one 
 another, mult have a diftincl conception of its 
 real figure; fo he that conceives diftinclly the 
 pofition of its feveral parts with regard to the 
 eye, muft have a diftincl conception of its vifible 
 figure. Now, there is nothing furely to hinder 
 a blind man from conceiving the pofition of the 
 feveral parts of a body with regard to the eye, 
 any more than from conceiving their fituation 
 with regard to one another ; and therefore I con- 
 clude, that a blind man may attain a diftincl 
 conception of the vifible figure of bodies. 
 
 Altho' we think the arguments that have been 
 offered are fufficient to prove, that a blind man 
 may conceive the vifible extenfion and figure of 
 bodies ; yet, in order to remove fome prejudices 
 againft this truth, it will be of ufe to compare 
 
 the 
 
SeA. 7. Of SEEING. 157 
 
 the notion which a blind mathematician might 
 form to himfelf of viable figure, with that which 
 is prefented to the eye in vifion, and to obferve 
 wherein they differ. 
 
 Firft, Vifible figure is never prefented to the 
 eye but in conjunction with colour : and akho* 
 there be no connexion between them from the 
 nature of the things, yet having fo invariably kept 
 company together, we are hardly able to disjoin 
 them even in our imagination. What mightily 
 increafes this difficulty is, that we have never 
 been accuftomed to make vifible figure an object 
 of thought. It is only ufed as a fign, and ha- 
 ving ferved this purpofe, pafies away, without 
 leaving a trace behind. The drawer or defigner, 
 whofe bufinefs it is to hunt this fugitive form, 
 and to take a copy of it, finds How difficult his 
 talk is, after many years labour and practice 
 Happy ] if at laft he can acquire the art of ar- 
 refting it in his imagination, until he can deline- 
 ate it. For then it is evident, that he muft be 
 able to draw as accurately from the life as from 
 a copy. But how few of the profefled matters 
 of defigning are ever able to arrive at this de- 
 gree of perfeel ion ? it is no wonder, then, that 
 we fhould find fo great difficulty in conceiving 
 this form apart from its conftant aflociate, when 
 it is fo difficult to conceive it at all. But our 
 blind man's notion of vifible figure will not be 
 affociated with colour, of which he hath no 
 conception ; but it will perhaps be aflbciated with 
 hardnefs or fmoothnefs, with which he is ac- 
 quainted 
 
i 5 8 Ofthe HUMAN MIND. Chap. VI. 
 quainted by touch. Thefe different afibciations 
 are apt to impofe upon us, and to make things 
 feem different, which in reality are the fame. 
 
 Secondly, The blind man forms the notion of 
 vifible figure to himfelf, by thought, and by ma- 
 thematical reafoning from principles ; whereas 
 the man that fees, has it prefented to his eye at 
 once, without any labour, without any reafoning, 
 by a kind of infpiration. A man may form to 
 himfelf the notion of a parabola, or a cycloid, 
 from the mathematical definition of thofe figures, 
 altho' he had never feen them drawn or deline- 
 ated. Another, who knows nothing of the ma- 
 thematical definition of the figures, may fee them 
 delineated on paper, or feel them cut out in wood. 
 Each may have a diftinct conception of the fi- 
 gures, one by mathematical reafoning, the other 
 by fenfe. Now, the blind man forms his notion 
 of vifible figure in the fame manner as the firft 
 of thefe formed his notion of a parabola or a cy- 
 cloid, which he never faw. 
 
 Thirdly, Vifible figure leads the man that fees, 
 direftly to the conception of the real figure, of 
 which it is a fign. But the blind man's thoughts 
 move in a contrary direction. For he rnufr. firft 
 know the real figure, diftance, and fituation, of 
 the body, and from thence he flowly traces out 
 thevifible figure by mathematical reafoning. Nof 
 does his nature lead him to conceive this vifible 
 figure as a fign ; it is a creature of his own rea- 
 fon and imagination. 
 
 SECT, 
 
Sea. 8. Of SEEING. 
 
 '59 
 
 SECT. VIII. 
 
 Some queries concerning vifible figure anfwered. 
 
 T T may be afked, What kind of thing is this 
 : vifible figure ? Is it a fenfation, or an idea ? 
 If it is an idea, from what fenfation is it copied ? 
 Thefe questions may feem trivial or impertinent 
 to one who does not know, that there is a tribu- 
 nal of inquifition ere&ed by certain modern phi- 
 lofophers, before which every thing in nature 
 muft anfwer. The articles of inquifition are few 
 indeed, but very dreadful in their confequences. 
 They are only thefe : Is the prifoner an imprei- 
 fion, or an idea ? If an idea, from what impref- 
 fion copied ? Now, if it appears that the prifoner 
 is neither an impreflion, nor an idea copied from 
 p>me impreflion, immediately, without being al- 
 lowed to offer any thing, in arreft of judgment, 
 he is fentenced to pafs out of exigence,, and to 
 be, in all time to come, an. empty unmeaning 
 found, or the ghoft of a departed entity. 
 
 Before this dreadful tribunal, caufe and effeft,. 
 time and plaee, matter and fpirit, have been tried 
 andcaft : how.thenfhall'fuch.a poor flimfy form 
 as vifible figure ftand before it? It muft even 
 plead guilty, and confefs that it is neither an irn- 
 preflion,. nor an idea. For, alas ! it is notorious, 
 that it is extended in length and breadth ; it may 
 be long or fhort, broad or narrow, triangular, 
 quadrangular, or circular: and therefore unlefs 
 
 ideas 
 
i6o Of the H U M A N M I N D. Chap. VL 
 ideas and imprefiions are extended and figured, 
 it cannot belong to that category. 
 
 If it fhould ftill be afked. To what category of 
 beings does vifible figure then belong ? I can on- 
 ly, in anfwer, give fome tokens, by which thofe 
 who are better acquainted with the categories, 
 may chance to find its place. It is, as we have 
 {aid, the pofition of the feveral parts of a figu- 
 red body with regard to the eye. The differ- 
 ent pofitions of the feveral parts of the body 
 with regard to the eye, when put together, make 
 a real figure, which is truly extended in length 
 and breadth, and which reprefents a figure that 
 is extended in length, breadth, and thicknefs. 
 In like manner, a projection of the fphere is a 
 real figure, and hath length and breadth, but re- 
 prefents the fphere, which hath three dimensions. 
 A projection of the fphere, or a perfpective view 
 of a palace, is a reprefentative in the very fame 
 fenfe as vifible figure is, and wherever they 
 have their lodgings in the categories, this will be 
 found to dwell next door to them. 
 
 It may-farther be afked, Whether there be 
 any fenfation proper to vifible figure, by which 
 it is fuggefted in vifion ? Or by what means it is 7 
 prefented to the mind ? This is a queftion of 
 fome importance, in order to our having a dif- 
 tinct notion of the faculty of feeing : and to give! 
 all the light to it we can, it is necefiary to com- 
 pare this fenfe with other fenfes, and to make 
 fome fuppo/itions, by which we may be enabled 
 3 to 
 
Sect. 8, Of S E E I N Q. 161 
 
 to diftinguifti things that are apt to be confound* 
 ed, although they are .totally different; 
 
 There are three of our fenfes which give us 
 intelligence of things at a diftanGB^fmell, hear- 
 ing, and fight. In fmelling, and in hearing, we 
 have a fenfation or imprefijon upon the mind* 
 Which, by our cpnftitdtion, we conceive to be a 
 fign of fomething external : but the pofition of 
 this external thing, with regard to the organ of 
 fenfe, is not presented to the mind along with 
 the fenfation* When I hear the found of a coach, 
 I could not, previous to experience, determine 
 whether the founding body was above or below^ 
 to the right hand or to the left. So that the fcnr 
 fetion fuggefts to me fbme external object as the 
 taufe or occafion of it; but jt fuggefts not the 1 
 pofuipn of thjat object, whether h lies in this di- 
 rection or in that. The fame thing may be faid 
 With regard to fmelling,* But the cafe is quite 
 different with regard to feeing. When' I fee art 
 objectj the appearance which the colour of it 
 makes, may be called the fenfaUm, which fug- 
 gefts to me fome external thing as its caufe ; bu£ 
 it fuggefts likewife the individual dire&ion and 
 pofition of this eaufe with regard to the eye. I 
 know it is precifely in fuch a direction, and in no 
 Other. At thq fame time I am not confcious of 
 any thing that can be called Jenfatiom, but the 
 feufatipn of colour. The pofition of the coloured 
 thing is no fenfation, but.it is by the laws of my 
 constitution prefented to the mind along with 
 the colour, without any additional fenfation. 
 
 L LetT 
 
i6i OftheHUMAN MIND. Chap.Vf. 
 
 Let us fuppofe, that the eye werefo conftitu- 
 ted, that' the rays coming from any one point ofi 
 the object, were not, as they are in our eyes, col- 
 lected in one "point of the retinn, but difFufecf 
 over the whole : It is evident to thofe who un- 
 derftand the ftrudture of the eye, that fuch an 
 eye as we have fuppofed, would Ihew the colour 
 of a body as our eyes do, but that it would nei- 
 ther fhew figure nor pofition. The operation of 
 fuch an eye would be precifely fimilar tp that of 
 hearing and fmell; it would give no perception 
 of figure or extenfion, but merely of colour. Nor 
 is the fuppofitiorc we have made altogether ima- 
 ginary: for it is nearly the cafe of moft people 
 who have cataracts, whofe cryftalline, as Mr. 
 Chefeldenobferves, does not altogether exclude 
 the rays of light, but diffufes them over the retina, 
 fo that fuch perfons fee things as one does thro" 
 a glafs of broken gelly : they perceive the colour, . 
 but nothing of the figure or magnitude of ob- 
 jects. 
 
 Again, if we mould fuppofe, that fmell and 
 found were conveyed in right lines from the ol> 
 jects, and that every fenfation of hearing and 
 fmell fuggefted the precift direction or pofition 
 of its object •, in this cafe the operations of hear" 
 ing and fmelling would be fimilar to that of fee- 
 ing : we fhould fmell and hear the figure of ob- 
 jects, in the fame fenfe as now we fee it; and 
 every fmell and found would be aflbciated with 
 fome figure in the imagination, as colour is in 
 our prefen: ftate. 
 
 We 
 
Sect. 8. Of.SEEING. 163 
 
 We have reafon to believe, that the rays of 
 light make feme impreffion upon the retina ; but 
 we are not confcious of this impreffion ; nor have 
 anatomifts or philofophers been able to difcover 
 the nature and effects of it ; whether it produ- 
 ces a vibration in the nerve, or the motion of 
 fome fubtile fluid contained in the nerve, or 
 fomething different from either, to which we 
 xannot give a name. Whatever it is, we (hall j 
 call it the material impreffion <, remembring care- 
 fully, that it is not an impreffion upon the mind § 
 but upbn the body ; and that it is no feiifation, 
 nor can refemble fenfation, any more than figure 
 or, motion can refemble thought. Now, this 
 material impreffion, made upon a particular point 
 of the retina, by the laws of our conftitution, 
 fuggefts two things to the mind, namely, the co- 
 lour, and the pofition of fome external object. 
 No man can give a reafon, why the fame material 
 imprefiion might not, have fuggefted found, or 
 fmell, or either of thefe, along with the pofition 
 of the object. That it fhould fuggeft colour 
 and pofitionj and nothing elfe, we can refolve only 
 into our conftitution, or the will of our Maker. 
 And fince there is no neceifary connection be- 
 tween thefe two things fuggefted by this mate* 
 rial impreffion, it might, if it had fo pleafed our 
 Creator, have fuggefted one of them without the 
 other. Let us fuppbfe, therefore, fince it plain- 
 ly appears to be poffible, that our eyes had been 
 fo framed, as to fuggeft to us the pofition of the 
 object, without fuggefting, colour, or any other 
 L 2 quality . 
 
i6 4 Ofthe HUMAN MIND. Chap.Vfl 
 quality : What is the confequence of this fup- 
 pofition ? It is evidently this*, that the perfon en- 
 dued with fuch an eye, would perceive the vifible 
 figure of bodies, without having any fenfation or 
 impreffion made upon his mind. The figure he 
 perceives is altogether external ; and therefore 
 cannot be called an impreffion upon the mind y 
 without the groffeft abufe of language. If it 
 mould be faid, that it is-impoffible to perceive a 
 figure, unlefs there be fome impreffion of it upon 
 the mind ; I beg leave not to admit the impof- 
 fibiiity of this without fome proof: and I can? 
 find none. Neither can I conceive what- is 
 meant by an impreffion of figure upon the mind, 
 I can conceive an impreffion of figure upon wax,, 
 or upon' any body that is fit to receive it ; but 
 an impreffion of it upon the mind, is to me quite 
 unintelligible - y and altho' I form the moil dif- 
 tinct conception of the figure, I cannot, upon' 
 the ilricteft examination, find any impreffion of 
 it upon my mind. 
 
 If we fuppofe, laft of all; that the eye fiath? 
 the power reftored of perceiving colour,; I ap- 
 prehend that it will be allowed,, that now it per- 
 ceives figure in- the very fame manner as before y 
 with this difference only, that- colour' is always 
 joined with it. 
 
 In anfwer therefore to the queftion propofed,, 
 there feems„to be no fenfation that is appropriated:' 
 to vifible figure, or whofe office it is to fuggefe 
 it. It feems to be fuggefted immediately bf 
 the material impreffion upon the organ, of which 
 
 we 
 
$edV8. Of SEE'INsG. 165 
 
 f/e are not confcious : and why may not a ma- 
 terial impreffion upon the .rjetina fuggeft vifible 
 figure, as well as the material impreffion made 
 «pon the hand, when we grafp a ball, fuggefts 
 real figure ? In the one cafe, one and the fame 
 material impreffion, fuggefts both colour and vi- 
 fible figure ; and in the other cafe, one and the 
 fame material impreffion fuggefts hardnefs., heat, 
 -or cold, and real figure, all at the fame time. 
 • We fhall conclude this fe&ion with another 
 .queftion upon this fubjecl. Since the vifible fi- 
 gure of bodies is a real and external object to the 
 <eye, as their tangible figure is to the touch; it 
 may be aflced, Whence arifes the difficulty of at- 
 tending to the firft, and the facility of attending 
 to the laft ? It is certain that the firft is more fre- 
 quently prefented to the eye, than the laft is to 
 the touch : the firft is as. diftinct and determi- 
 aiate an object as the laft, and feems in its own 
 mature as proper for (peculation. Yet fo little 
 ihath it been attended to, that it never had ^ 
 .name in any language, until Bifhop Berkeley 
 gave it that which we .have ufed after his exam- 
 ple, to diftinguifh itfrom the figure whichisthe 
 objecl: of touch. 
 
 The difficulty of attending to the vifible fi- 
 gure of bodies, and making it an object of 
 thought, appears fo fimilar to that which we find 
 dn attending to our fenfations, .that both have 
 :probably like caufes. Nature intended the yi- 
 iible figure as a fign of the tangible figure and 
 iituation of bodies, and hath taught us by a kind 
 L 3 ~ of 
 
1 66 Of the HUMAN MIND. Chap. VI. 
 of inftinct to put it always to this ufe. Hence 
 it happens, that the mind pafles over it with a 
 rapid motion, to attend to the things fignified by 
 it. It is as unnatural to the mind to flop at the 
 vifible figure, and attend to it, as it is to a fphe- 
 rical body to Hop upon an inclined plane^ There 
 is an inward principle, which conftantly carries 
 it forward, and which cannot be overcome but 
 by a contrary force. 
 
 There are other external things which nature 
 intended for figns •, and we find this common to 
 them' all, that the mind is difpofed to overlook 
 them, and to attend only to the things fignified 
 by them. Thus there arc certain modifications 
 of the human face, which are natural figns of the 
 prefent difpofition of the mind. Every man 
 underftands the meaning of thefe figns, but not 
 one of a hundred ever attended to the figns them- 
 felves, or knows any thing about them. Hence 
 you may find many an excellent practical phyfiog- 
 nomift, who knows nothing of the proportions 
 of a face, nor can delineate or defcribe the ex- 
 preffion of any one paffion. 
 
 An excellent painter or ftatuary can tell, not 
 only what are the proportions of a good face, 
 but what changes every paffion makes in it. 
 This, however, is one of the chief myfteries of 
 his art, to the acquifition of which, infinite la- 
 bour and attention, as well as a happy genius, 
 are required. But when .he puts his art in 
 practice, and happily expreffes a paffion by its 
 proper figns., every one underftands the meaning 
 
 of 
 
■3c&..8. Of SEEING. 167 
 
 of thefe figns, without art, and without re- 
 flection. 
 
 What has been faid of painting, might eafily 
 he applied to .all the fine arts,. The difficulty in 
 them all confiils in knowing and attending to 
 thofe natural figns, whereof every man under- 
 stands the meaning. 
 
 We pafs from the fign to the thing fignified, 
 with eafe, and by natural impulfe.; but to go 
 backward from,the thing fignified ,to the fign, is 
 a work of labour and difficulty. Viable figure, 
 therefore, being intended by nature to be a fign, 
 we pafs on immediately to the thing fignified, 
 and cannot eafily return to give any attention to 
 ihe fign. 
 
 Nothing thews' more clearly our indifpofifion 
 to attend to vifible figure and vifible extenfion 
 than this, that altho' mathematical reafoning is 
 no lefs applicable to them, than to tangible 
 ■figure and extenfion, yet they have entirely 
 eicaped the notice of mathematicians. While 
 that figure and that extenfion which are objects 
 "of touch, have been tortured ten thoufand ways 
 for twenty centuries, and a very noble fyftern 
 of fcience has been drawn out of them ; not a 
 fingle proposition do we find with regard to the 
 figure and extenfion which are the immediate ob- 
 jects of fight ! , 
 
 When the geometrician draws a diagram with 
 
 the mod perfect accuracy; when he keeps his 
 
 eye fixed upon it, while he goes through a long 
 
 procefs of reafoning* and demonftrates the rela- 
 
 L 4 tions 
 
i68 Ofthe HUMAN MIND. Chap. VI, 
 
 tions of the feveral parts of his figure; he does 
 not confider, that the vifibJe figure preferred to 
 his eye, is only the reprefentative of a tangible 
 figure, upon which all his attention is. fixed; he 
 does not confider that thefe two figures have 
 really different properties ; and that what he de-; 
 jnonftrates tq be true of the one, is not true of 
 the other, 
 
 This perhaps will feem fo great a paradox, 
 even to mathematicians, as to require demo^ 
 {Iration before it can be believed. Nor is the de- 
 rnonftration at all difficult, if the reader will have 
 patience to enter but a little into the mathema-* 
 peal confideration of vifible figure^ which wq 
 {hall call the geometry of vifibles, 
 
 SECT. IX. 
 
 Of the geometry of vifihhs. 
 
 !f N this geometry, the definitions of a poin£ ; 
 
 of a line, whether ftraight or curve; of an 
 angle, whether acute, or right, or obtufe ; and 
 t)f a circle, are the fame as in common geome- 
 try. The mathematical reader will eafily enter 
 into the whole myftery of this geometry, if he 
 attends duly to thefe few evident principles. 
 
 I. Suppofing the eye placed in the centre 
 of a fphere, every great circle of the fphere will 
 have the fame appearance to the eye as if it was 
 £ ftraight line. For the curvature of the circle 
 being turned directly toward the eye, is not 
 
 perceived 
 
Se&.g. Of SEEING, ify 
 
 perceived by it. And for the fame reafon, any 
 Jine which is drawn in the plane of a great 
 Circle of the fphere, whether it be in reality 
 ftraight or curve, will appear ftraight to th« 
 eye. 
 
 2. Every" vifible right line will appear to 
 coincide with fome great circle of the fphere j 
 and the circumference of that great circle, even 
 when it is produced until it returns into itfelf, 
 will appear to be a continuation of the fame vifi- 
 ble right line, all the parts of it being vifibly in 
 directum. For the eye, perceiving only the 
 pofition of .objects with regard to itfelf, and not 
 their diftance, will fee thofe points in the fame 
 vifible place which have the fame pofition with 
 regard to the eye, how different foever their 
 diftahces from it may be. Now, fince a plane 
 palling through the eye and a given vifible 
 right line, will be the plane of fome great circle 
 of the fphere, every point of the vifible right 
 line will have the fame pofition as fome point df 
 the great circle -, therefore they will both have 
 the fame vifible place, and coincide to the eye ; 
 and the whole circumference of the great circle 
 continued even until it returns into itfelf, wilj 
 appear to be a continuation of the fame vifibl© 
 right line. 
 
 Hence it follows. 
 
 3, That every vifible right line, when i% 
 48 continued in $re£ium i as far as it may be 
 continvied, will be reprefented. by a great circle 
 
 of 
 
iyo Ofthe HUMAN MIND. Chap. VL 
 
 of a fphere, in whofe centre the eye is placed. 
 It follow^, 
 
 4 . That the vifible angle comprehended un- 
 der two vifible right lines, is equal to the 
 Ipherical angle comprehended under the two 
 great -circles which are the reprefentatives of 
 thefe vifible lines. For fince tKe vifible lines 
 appear to qoincide with the great circles, the 
 vifible angle., comprehended under the former, 
 muft be equal to the vifible angle comprehend- 
 ed under the latter. But the vifible angle com- 
 prehended under the two great circles, when 
 fcen from the centre, is of the fame magnitude 
 .with the fpherical angle which they really com- 
 prehend, as mathematicians know ; therefore the 
 vifible angle made by any two vifible lines, is 
 equal to the fpherical angle made by the. two 
 great circles of the fphere which are their repre-t 
 fentatives. 
 
 5. Hence it is evident, that every vifible 
 right-lined triangle, will coincide in all it's 
 parts with fome fpherical triangle. The fides 
 of the one will appear equal to the fides of the 
 other, and the angles of the one to the angles 
 of the other, each to each ; and therefore the 
 whole of the one triangle will appear equal to 
 the whole of the other. In a word, to the 
 eye they will be one and the fame, and have 
 the fame mathematical properties. The pro- 
 perties therefore of vifible right-lined triangles, 
 are not the fame with the properties of plain 
 
 triangles, 
 
Seft.V Of SEEING. 17I 
 
 triangles, but are the fame with thofe of fphe- 
 rical triangles. 
 
 6. Every leffer circle of the fphere, will ap- 
 pear a circle to the eye, placed, as we have fup- 
 pofed all along, in the centre of the fphere. 
 And, on the other hand, every vifible circle 
 will appear to coincide with fome leffer circle of 
 the fphere. 
 
 7. Moreover, the, whole furface of the fphere 
 will reprefent the whole of vifible fpace : for, 1 
 fince every vifible point coincides with fome 
 point of the furface of the fphere, and has the 
 fame vifible place, it follows, that all the parts 
 of the fpherical furface taken together, will re- 
 prefent all poffible vifible places, that is, the 
 whole of vifible fpace. And from this it fol- 
 lows,- in "the laft place, 
 
 8. That every vifible figure will he repre- 
 fented by that part of the furface of the fphere, 
 on which it might be projected, the eye being 
 jn the centre. And every fuch vifible figure 
 will bear the fame ratio to the whole of vifible 
 fpace, as the part of the fpherical furface which 
 r^prefents it, bears to the whole fpherical fur- 
 face. 
 
 The mathematical reader, I hope, will enter 
 into thefe principles with perfect facility, and 
 will as eafily perceive, that the following pro- 
 pofitions with regard to vifible figure and fpace, 
 which we offer only as a fpecimen, may be ma- 
 thematically demonflrated from them, and are 
 |iot lefs true nor lefs evident than the pro- 
 
 pofitions 
 
tyz Of the HUMAN MIND. Chap. VI. 
 
 pofitions of Euclid, with regard to tangible 
 figures. 
 
 Prop. i. Every right line being produced, 
 will at laft return into itfelf. 
 
 2. A right line returning into itfelf, is the 
 longeft pofiible right line ; and all other right 
 lines bear a finite ratio to it. 
 
 3. A right line returning into itfelf, divides 
 tiie whole of vifible fpace into two equal parts, 
 which will both be comprehended under this 
 sight line. 
 
 4. The whole of vifible fpace bears a finite 
 rat ia to any part of it. 
 
 5. Any two right lines being produced, will 
 meet in two points, and mutually bifect each 
 Other. 
 
 6. If two lines be parallel, that is, every 
 where equally diftant from each other, they can- 
 not both be ftraight. 
 
 7. Any right line being given, a point may 
 be found, which is at the fame distance from all 
 f he points of the given right line. 
 
 8. A circle may be parallel to a right line, 
 that is, may be equally diftant from it in all its 
 parts. 
 
 9. Right-lined triangles that are fimilar, are 
 alfo equal. 
 
 10. Of every right-lined triangle, the three 
 angles taken together, are greater than two right 
 
 angles. 
 
 1 1 . The angles of a right-lined triangle, may 
 
 all be right angles, or all obtufe angles. 
 
 12. Unequal 
 
Scfl. 9- Of SEEING. x?$ 
 
 12. Unequal circles are not as the fquares of 
 their diameters, nor are their circumferences ift 
 the ratio of their diameters. 
 
 This fmall fpecimen of the geometry of vift- 
 bles, is intended to lead the reader to a clear and 
 diftinft conception of the figure and extenfion 
 which is prefented to the mind by vifion ; and 
 to demonftrate the truth of what we have affirm- 
 ed abovCj namely, That thofe figures and that 
 extenfion which are the immediate objefb of 
 fight, are not the figures and the extenfion about 
 which common geometry is employed ; that th& 
 geometrician, while he looks at his diagram,, and 
 demonftrates a propofition-, hath a figure prefent- 
 ed to his eye, which is only a fign and repre&it- 
 tative of a tangible figure ; that he gives- not the 
 leaft attention to the firft, but attends only to the 
 iaft i and that thefe two. figures have different 
 properties, fo that what he demonftrates' of the 
 one, is not true of the other. 
 
 It deferves, however, to be remarked, that as 
 a fmall part of a fpherical furface differs not fen- 
 fibly from a plain furface ; fo a fmall part of vt- 
 fible extenfion differs very little from that exten- 
 fion in length and breadth, which is the objeel: of 
 touch. And k is likewife to be obferved, that 
 *he human eye is fo formed, that an object which; 
 is feen diftincHy and at one view, can occupy 
 buc a fmall part of vifible fpace : for we never 
 fee diftin&ly what is at a eonfiderable diftance 
 from the axis of the eye •, and therefore when 
 we would fee a large object at one view, the eye 
 3 muft 
 
'j 74 Of the HUMAN MIND. Chap.VL 
 tnuft be at fo great a diftanee, that the objecT; 
 occupies but a fmall part of vifible fpace. From 
 thefe two obfervations, it follows, that plain fi^ 
 gures which are feen at one view, when their 
 planes are not oblique, but direct to the eye, dif-* 
 fer little from the vifible figures which they pre- 
 sent to the eye- The feveral lines in the tangible 
 figure have very nearly the fame proportion to 
 each other as in the vifible ; and the angles of 
 the one are very nearly, altho' not ftrictly and 
 mathematically, equal to thofe of the other. Al- 
 tho' therefore we have found many inftances of 
 natural figns which have no fimilitude to the 
 things fignified, this is not the cafe with regard 
 to vifible figure. It hath in all cafes fuch a fimi- 
 litude to the thing fignified by it, as a plan or 
 profile hath to that which it reprefents ; and in 
 fome cafes the fign and^thing fignified, have to all 
 fenfe the fame figure and the fame proportions. 
 If we could find a being endued with fight only, 
 without any other external fenfe, and capable of 
 reflecting and reafoning upon what he fees, th& 
 notions and philofophical {peculations of fuch a 
 being, might afiift us in the difficult tafk of drf- 
 tinguifhing the perceptions which we have pure- 
 ly by fight, from thofe which derive their origin 
 from other fenfes. Let us fuppofe fuch a being,, 
 ' and conceive, as well as we can, what notion he 
 would have of vifible objects, and what concju- 
 fions he would deduce from them. We mult not 
 conceive him difpofed by his conftitution, as we 
 are, to confider the vifible appearance as a fign 
 
 of 
 
Se&. o. Of SEEING. 175 
 
 of fomething elfe : it is no fign to him,^ becaufis 
 there is nothing fignified by it ; and therefore we 
 tnuft fuppofe him as much difpofed to attend to 
 the vifible figure and extenfion of bodies, as we 
 are difpofed to attend to their tangible figure and 
 extenfion. 
 
 - If various figures were prefented to his fenfe, 
 he might without doubt, as they grow familiar, 
 compare them together, and perceive wherein 
 they agree, and wherein they differ. He might 
 perceive vifible objedls to have length and breadth, 
 but could have no notion of a third dimenfion, 
 any more than we can have of a fourth. All vi- 
 fible objects would appear to be terminated by 
 lines, ftraight or curve ; and objefts terminated 
 by the fame vifible lines, would occupy the fame 
 place, and fill the fame part of vifible fpace. It 
 would not be poffible for him to conceive one 
 object to be behind another, or one to be near- 
 er, another, more diftant. 
 
 To us, who conceive three dimenfions, aline 
 may be conceived ftraight ; or it may be con- 
 ceived incurvated in one dimenfion, and ftraight 
 in another ; or, laftly, it may be incurvated in 
 two dimenfions. Suppofe a line to be drawn up- 
 wards and downwards, its length makes one di- 
 menfion, which we fhall call upwards and down- 
 wards ; and there are two dimenfions remaining, 
 according to 'which it may be ftraight or curve. 
 It may be bent to the right or to the left; and 
 if it has no bending either to right or left, it 
 .is ftraight in this dimenfion. But fuppofing it 
 
 ftraight 
 
1 7 6 O," the HUMAN MIND. Chap. VL 
 ftraight in this dimenfion of right and left, there 
 is ftill another dimenfion remaining, in which it 
 may be curve ; for it may be bent backwards of 
 forwards. When we conceive a tangible ftraightj 
 line, we exclude curvature in either of thefe two 
 dimenfions : and as what is conceived to be ex- 
 cluded, muft be conceived, as well as what is con- 
 ceived to be included, it follows, that all the three 
 dimenfions enter into our conception of a ftraight 
 line. Its length is one dimenfion^ its ftraight- 
 nefs in two other dimenfions is included, or cur- 
 vature in thefe two dimenfions excluded, in the 
 conception of it. 
 
 The being we have fuppofed, having no con- 
 ception of more than two dimenfions, of which 
 the length of a line is one, cannot poffibly con- 
 ceive it either ftraight or curve in more than one 
 dimenfion : fo that in his conception of a right 
 line, curvature to the right hand or left is ex- 
 cluded ; but curvature backwards or forwards 
 cannot be excluded, becaufe he neither hath, nor 
 can have any conception of fuch curvature. Hence 
 we fee the reafon that a line, which is ftraight to 
 the eye, may return into itfelf : for its being 
 ftraight to the eye, implies only ftraightnefs in 
 one dimenfion ; and a line which is ftraight in 
 one dimenfion, may notwithftanding be curve in 
 another dimenfion, and fo may return into itfelf* 
 
 To us, who- conceive three dimenfions, a fur- 
 face is that which hath length and breadth, ex- 
 cluding thicknefs : and ailurface may be either 
 plain in this third dimenfion, or it may be in- 
 cur vated : 
 
Seft.g. Of SEEING. 177 
 
 curvated : fo that the notion of a third dimen- 
 sion enters into our conception of a furface; for it 
 is only by means of this third dimenfion that we 
 can diftihguifli furfaces into plain and curve fur- 
 faces j and neither one nor the other can be con- , 
 ceived without conceiving a third dimeniion. 
 
 The being we have fuppofed having no con- 
 ception of a third dimenfion, his vifible figures 
 have length and breadth indeed ; but thicknefs 
 is neither included nor excluded; being a thing 
 of which he has no conception. And therefore vi- 
 fible figures, altho' they have length and breadth, 
 as furfaces have, yet they are neither plain fur- 
 faces, nor curve furfaces. For a curve furface 
 implies curvature in a third dimenfion, and a plain 
 furface implies the want of curvature in a third 
 dimenfion ; and fuch a being can conceive nei- 
 ther of thefe, becaufe he has no conception of a 
 third dimenfion. Moreover, altho* he hath a dif-, 
 tirift conception of the inclination of two lines 
 which make an angle, yet he can neither con- 
 ceive a plain angle nor a fpherical angle. Even 
 , his notion' of a point is fomewhat lefs determined 
 than ours. In the notion of a point we exclude 
 length, breadth, and thicknefs •, he excludes 
 length and breadth, but cannot either exclude or 
 include thicknefs, becaufe he hath no conception, 
 of it. 
 
 Having thus fettled the notions which fuch a 
 , being as we have fuppofed might form of ma- 
 thematical points, lines, angles, and figures, it is 
 eafy to fee, that by comparing thefe together, 
 M and 
 
1 78 Of the H O M A N M I N D. Chap. .Vi- 
 and reaforiing about them, he might difcover 
 their relations, and form geometrical conclufiona 
 built uponfelf-evident principles. He might like- 
 wife, without doubt, have the fame notions of 
 numbers as we have, and form a fyftem of arith- 
 metic. It is not material to fay in what order 
 he might proceed in fuch difcoveries, or how 
 much time and pains he might employ about 
 them ; but what fuch a being, by reafon and in- 
 genuity, without any materials of fenfation but 
 thofe of fight only, might difcover. 
 
 As it is more difficult to attend to a detail of 
 poffibilities,. than of fafts even of flender authori- 
 ty, I fliall beg leave to give an extract from the 
 travels of Johannes Rudblphus Anepigraphus, a 
 Roficrucian philofopher, who having, by deep 
 ftudy of the occult fciences, acquired the art of 
 tranfporting himfelf to various fublunary regions, 
 and of converfmg with various orders of intelli- 
 gences, in the courfe of his adventures, became 
 acquainted with an order of beings exacBy fuch 
 as I have fuppofed. 
 
 How they communicate their fentiments ta 
 one another, and by what means he became ac- 
 quainted with their language, and was initiated 
 into their philofophy, as well as of many other 
 particulars, which might have gratified the curio- 
 fity of his readers, and perhaps added credibility 
 to his relation, he hath not thought fit to inform 
 us ; thefe being matters proper for adepts only 
 to know. 
 
 His 
 
Sea. £» t)f SEEING. i 79 
 
 His account of their philofophy is as follows* 
 " The Idomenians," faith he, " are many of 
 cc them very ingenious* and much given to con- 
 ** templation. In arithmetic, geometry, meta- 
 " .phyfics, and phyfics, they have moft elaborate 
 " fyftems, In the two latter indeed they have 
 " had many difputes carried on with great fub- 
 " tilty, and are divided into various feels ; yet in 
 " the two former there hath been no lefs una- 
 " nimity than among the human fpecies. Their 
 *' principles relating to numbers and arithmetic* 
 " making allowance for their notation, differ in 
 *' nothing from, ours : but their geometry differs 
 " very cOnfiderably." 
 
 As our author's account of the geometry of the 
 Idomenians agrees in every thing with the geo- 
 metry of vifibles, of Which we have already gi* 
 ven a fpecimen, we mail pafs over it. He goes on 
 thus : " Colour, exterifion, and figure, are con- 
 " ceived to be the effential properties of body. 
 " A very 'con fiderable feet maintains, that colour 
 " is the effence of body. If there had been no 
 " colour, fay they, there had been no perception 
 " or fenfation. Colour is all that we perceive, 
 " or can conceive, that is peculiar to body ; ex* 
 " tenfion and figure being modes common to 
 " body and to empty fpace. And if We fhould 
 " fuppofe a body to be annihilated, 'colour is the 
 " only thing in it that can be annihilated ■, for 
 " its place, and confequently the figure and ex- 
 " tenfion of that place, mud remain, and cannon 
 «' be imagined not to exift. Thefe philofophers 
 M 2 " hold 
 
180 Of the HUMAN MIND. Chap.VL 
 " hold fpace to be the place of all bodies, im- 
 " moveable and indeftru&ible, without figure, 
 " and fimilar in all its parts, incapable of increafe 
 " or diminution, yet not unmeafureable : for 
 " every the leaft part of fpace bears a finite ratio 
 w to the whole. So that with them the whole 
 " extent of fpace is the common and natural 
 " meafure of every thing that hath length and 
 " breadth, and the magnitude of every body and 
 " of every figure is exprefied by its being fuch a 
 * c part of the univerfe. In like manner, the com- 
 " mon and natural meafure of length, is an in- 
 " finite right line, which, as hath been before 
 " obferved, returns into itfelf, and hath no 11- 
 " mits, but bears a finite ratio to every other 
 " line. 
 
 " As to their natural philofophy, it is now 
 " acknowledged by the wifeft of them to have 
 «' been for many ages in a very low ftate. The 
 " philofophers obferving, that one body can dif- 
 " fer from another only in colour, figure, or 
 " magnitude, it was taken for granted, that all 
 " their particular qualities mult arife from the 
 *' various combinations of thefe their efiential at- 
 " tributes. And therefore it was looked upon as 
 " the end of natural philofophy, to fhew how 
 " the various combinations of thefe three quali- 
 " ties in different bodies produced all the phse- 
 «* nomena of nature. It were endlefs to enume- 
 " rate the various fyftems that were invented 
 " with this view, and the difputes that were car- 
 *' ried on for ages ; the followers of every fy- 
 t !' ftem 
 
Seft. 9. Of SEEING. 181 
 
 *' Item expofing the weak fides of other fyftems, 
 " and palliating thofe of their own, wich great 
 " art. 
 
 " At laft, fome free and facetious fpirits, wea- 
 " ried with eternal difputation, and the labour 
 " of patching and propping weak fyftems, be- 
 " gan to complain of the fubtilty of nature ; of 
 " the infinite changes that bodies undergo in fi- 
 " gure, colour, and magnitude; and of the diffi- 
 " culty of accounting for thefe appearances, ma- 
 " king this a pretence for giving up all inquiries 
 *' into the caufes of things, as vain and fruitlefs. 
 
 " Thefe wits had ample matter of mirth and 
 ** ridicule in the fyftems of philofophers, aj»d 
 " finding it an eafier tafk to pull down than to 
 *' build or fupport, and that every feet furnifhed 
 w them with arms and auxiliaries to deltroy an- 
 " other, they began to fpread mightily, ano went 
 ** on with great fuccefs. Thus philofophy gave 
 u way to fcepticifm and irony, and thofe fyftems 
 " which had been the work of ages, and the ad- 
 " miration of the learned, became thejeftof the 
 M vulgar : for even the vulgar readily took part 
 " in the triumph over a kind of learning which 
 " they had long fufpected, becaufe it produced 
 " nothing but wrangling and altercation. The * 
 " wits having now acquired great reputation, 
 ** and being flufhed with fuccefs, began to think 
 " their triumph incomplete, until every pretence 
 *•' to knowledge was overturned ; and according- 
 *' ly began their attacks upon arithmetic, geo- 
 ?' metry, and even upon the common notions of 
 M 3 ** untaught 
 
i82 Of the HUMAN MIND. Chap. VI, 
 
 " untaught Idomenians. So dijfHcult it hath al- 
 " ways been (fays our author) for gteap con- 
 *' querors to know where to flop. 
 
 " In the mean time, natural pbilofophy be-* 
 " gan to rife from its afhes, under the direction 
 " of a perfon of great genius, who is looked 
 " upon as having had fomething in him above 
 «* Idomenian nature, He obferved, that the Xdo- 
 *' menian faculties were certainly intended for 
 " contemplation, and that the works of nature 
 *' were a nobler fubje6t to exercife them upon, 
 " than the follies of fyftems, or the errors of the 
 " learned ; and being fenfible of the difficulty 
 *' of finding out the caufes of natural things, he 
 *' propofed, by accurate obfervation of the pha^ 
 «' nomena of nature, to find out the rules ac- 
 *' cording' to which they happen, without in- 
 " quiring into the caufes of thofe rules. In this 
 *' he made confiderable progrefs himfelf, and 
 *' planned out much work for his followers, who 
 " call themfelves induftive philofopbers. The 
 " fceptics look with envy upon this riling feci, 
 " as eclipfing their reputation, and threatning to 
 " limit their empire •, but they are at a lofs on 
 ? ' what hand to attack it.. The vulgar begin to 
 *' reverence it, as producing ufeful difcoveries. 
 
 " It is to be obferved, that every Idomenian 
 " firmly believes, that two or more bodies may 
 *^ exift in the fame place. For this they have 
 " the teftjmony of fenfe, and they can no more 
 " doubt of it, than they can doubt whether 
 ** they have any perception at all. They often, 
 
Sect. 9; Of SEEING. ,« 3 
 
 *' fee two bodies meet, and coincide in the 
 " fame place, and feparate again, without ha- 
 * c ving undergone any change in their fenfible 
 *' qualities by this penetration. When two 
 " bodies meet, and occupy the fame place, com- 
 " monly one only appears in that place, and 
 *' the other difappears. That which continues 
 '* to appear is faid to overcome, the other to be 
 " overcome." 
 
 To this quality of bodies they gave a name, 
 which pur author tells us hath no word anfwer- 
 ing to it in any human language. And there- 
 fore, after making a long apology, which I 
 omit, he begs leave to call it the over-coming qua- 
 lity of bodies. He allures us, that " the ipe- 
 *' culations which had been raifed about this 
 *' fingle quality of bodies, and the hypothefes 
 " contrived to account for it, were fufficient to 
 * c fill many volumes. Nor have there been 
 " fewer hypothefes invented by their philofo- 
 " phers, to account for the changes of magni- 
 *' tude and figure ; which, in moft bodies that 
 " move, they perceive to be in a continual 
 *' fluctuation. The founder of the inductive 
 * c feet, believing it to be above the reach of 
 ** Idomentan faculties, to difcover the real caufes 
 " of thefe phenomena, applied himfelf to find 
 " from obfervation, by what laws they are 
 *' connected together ; and difcovered many 
 " mathematical ratios and relations concerning 
 "the motions, magnitudes, figures, and over- 
 *' coming quality of bodies, which conftaflc 
 M 4 ** experience 
 
j 84 Of the HUM AN" MIND. Chap. VI. 
 " experience confirms. But the oppofers of 
 " this feci: chufe rather to content themfelves 
 " with ftigned caufes of thefe phenomena, than 
 *' to acknowledge the real laws whereby they 
 ** are governed, which humble their pride, by 
 " being confefiedly unaccountable." 
 
 Thus far Johannes Rudolphus Anepigraphus, 
 "Whether this Anepigraphus be the fame who is 
 recorded among the Greek alchemiftical writers 
 not yet publiflied, by Borrichius, Fabricius, and 
 others, I do not pretend to determine. The 
 identity of their name, and the fimilitude of 
 their ftudies, although no flight arguments, yet 
 are not abfolutely conclusive. Nor will I take 
 upon me to judge of the narrative of this learn- 
 ed traveller by the external marks of his credi- 
 bility -, I fhall confine myfelf to thofe which the 
 critics call internal. It would even be of fmall 
 importance to enquire, whether the Idomenians 
 have a real, or only an ideal exiftence-, fince 
 this is difputed among the learned with regard 
 to things with which we are more nearly con- 
 nected. The important queftion is, Whether 
 the account above given, is a juft account of 
 their geometry and philofophy ? We have all 
 the faculties which they have, with the addition 
 of others which they have not : we may there- 
 fore form fome judgment of their philofophy 
 and geometry, by fepararing from all others,, 
 the perceptions we have by fight, and reafon- 
 ing upon them. As far as I am able to judge 
 in this way after a careful examination, their 
 
 geometry 
 
Sea. 9. Of S E E I N G. 185 
 
 geometry muft be fuch as Anepigraphus hath 
 defcribed. Nor does his account of their phi- 
 lofophy appear to contain any evident marks of 
 impofture •, altho' here, no doubt, proper al- 
 lowance is to be made for liberties which tra- 
 vellers take, as well as for involuntary mjftakes 
 which they are apt to fall into. 
 
 SECT. X. 
 
 Of the parallel motion of the eyes. 
 
 TT Aving explained, as diftin&ly as we can, 
 vifible figure, and (hewn its connection 
 with the things fignified by it, it will be proper 
 next to confider fome phenomena of the eyes, 
 and of vifion, which have commonly been re- 
 ferred to cuftom, to anatomical or to mechani- 
 cal caufes ; but which, as I conceive, muft be re- 
 folved into original powers and principles of the 
 human mind -, and therefore belong properly to 
 the fubject of this inquiry. 
 
 The firft is, the parallel motion of the eyes ; 
 by which, when one eye is turned to the right 
 or to the left, upwards or downwards, or ftraight 
 forwards, the other always goes along with it 
 in the fame direction. We fee plainly, when 
 both eyes are open, that they are always turn- 
 ed the fame way, as if both were acted upon by 
 the fame motive force : and if one eye is fhur, 
 and the hand laid upon it, while the other turns 
 yarious ways, we feci the eye that is fhut turn 
 
 at 
 
|86 Of the H U M A N MI N D. Chap. VI. 
 at the fame time, and that whether we will or 
 riot. What makes this phenomenon furprifing 
 is, that it is acknowledged by all anatomifts, 
 that the mufcles which move the two eyes, and 
 the nerves which ferve thefe mufcles, are entire- 
 ly diftincl and unconnected. It would be thought 
 very furprifing and unaccountable to fee a man, 
 ■who, from his birth, never moved one arm, 
 without moving the other precisely in the fame 
 manner, fo as to keep them always parallel: 
 yet it would not be more difficult to find the 
 phy.fical caufe of fuch motion of the arms, than 
 it is to find the caufe of the parallel motion of 
 .the eyes, which is perfectly fimilar. 
 
 The only caufe that hath been affigned of this 
 parallel motion of the eyes, is cuftom. We find 
 by experience, it is faid when we begin to 
 look at obje&s, that in order to have diftinct 
 virion, it is neceffary to turn both eyes the 
 fame way •, therefore we foon acquire the habit 
 of doing it conftantly, and by degrees ioofe the 
 power of doing otherwife. 
 
 This account of the matter feems to b.e in- 
 fufficient -, becaufe habits are not got at once s 
 it takes time to acquire and to confirm them ; 
 and if this motion of the eyes were got by habit, 
 we mould fee children, when they are born, 
 turn their eyes different ways, and move one 
 without the other, as they .do their hands or 
 Jegs. I know fome have affirmed' that they 
 are apt to do fo. But I have never found it true 
 fjrom my own obfervation, altho' J have taken 
 
 pains 
 
Seft. 10. Of S E E I N G. 137 
 
 pains to make obfervations of this kind, and 
 have had good opportunities. I have likewife 
 confulted experienced midwives, mothers and 
 nurfes, and found them agree, that they had 
 never obferved diftortions of this kind in the 
 eyes of children, but when they had reafon 
 to fufpedt convulfions, or ibme preternatural 
 caufe. 
 
 It feems therefore to be extremely probable, 
 that, previous to cuftom, there is fornething 
 jn the conftitution, fome natural inftinct, which 
 directs us to move both eyes always the fame 
 way. 
 
 We know not how the mind acts upon the 
 body, nor by what power the mufcks are con- 
 tracted and relaxed : but we fee that in fome of 
 the voluntary, as well as in fome of the invo- 
 luntar.y motions, this power is fo directed, that 
 many mufcles which have no material tie or 
 connection, act in concert, each of them being 
 taught to play its part in exact time and meafure, 
 £Jor doth a company of expert players in a 
 theatrical performance, or of excellent mufieians 
 in a concert, or of good dancers in a country- 
 dance, with more regularity and order, confpire 
 and contribute their feveral. parts, to produce 
 one uniform effect, than a number of mufcles 
 do, in many of the animal functions, and in 
 many voluntary actions. Yet welee fuch ac^ 
 tions no lefs fkilfully and regularly performed 
 jn children, and in thofe who know not that 
 
 § they 
 
..j«8 Of the HUMAN MIND. Chap. VI. 
 they have fuch mufcles, than in the moft fkilful 
 anatomift and phyfiologift. 
 
 Who taught all the mufcles that are concern- 
 ed in fucking, in fwallowing our food, in breath- 
 ing, and in the feveral natural expulfions, to act 
 their part in fuch regular order and exact 
 meawre ? It was not cuftom furely. It was 
 that fame powerful and wife Being who made 
 the fabric of the human body, and fixed the 
 laws by which the mind operates upon every 
 part of it, fo that they may anfwer the purpofes 
 intended by them. And when we fee, in fo 
 many other inftances, a fyftemof unconnected 
 mufcles confpiring fo wonderfully in their feveral 
 functions, without the aid of habit, it needs 
 not be thought ftrange, that the mufcles of the 
 eyes ihould, without this aid, confpire to give 
 that direction to the eyes, without whichr they 
 eould not anfwer their end. 
 
 We fee a like confpiring adlion in the mufcks 
 which contract the pupils of the two eyes ; and 
 in thofe mufcles, whatever they be, by which 
 the conformation of the eyes is varied according 
 to the diftance of objects. 
 
 It ought however to be obferved, that altho* 
 it appears to be by natural inftinct that both eyes 
 are always turned the fame way, there is, ftill 
 fome latitude left for cuftom. 
 
 What we have faid of the parallel motion of 
 the eyes is not to be underftood fo ftriftly, as 
 jf nature directed us to keep their axes always 
 precifely and mathematically parallel to each 
 
 other, 
 
$eft. 10. Of SEEING. 189 
 
 other. Indeed, although they are always nearly 
 parallel, they hardly ever are exaftly fo. When 
 we look at an object, the axes of the eyes meec 
 in that object ; and therefore make an angle, 
 which is always fmall, but will be greater or 
 lefs, according as the object is nearer or more 
 remote. Nature hath very wifely left us the 
 power of varying the parallelifm of our eyes a 
 little, fo that we can direct them to the fame 
 point, whether remote or near. This, no doubt, 
 is learned by cuftom ; and accordingly we fee, 
 that it is a^ long time before children get this 
 habit in perfection. . 
 
 This power of varying the parallelifm of the 
 eyes is naturally no more than is fufficient for 
 the purpofe intended by it, but by much practice 
 and (training, it may be increafed. Accord- 
 ingly we fee, that fome have acquired the 
 power of diftorting their eyes into unnatural 
 directions, as others have acquired the power of 
 diftorting their bodies into unnatural poftures. 
 
 Thofe who have loft the fight of an eye, 
 commonly lofe what they had got by cuftom, 
 in the direction of their eyes, but retain what 
 they had by nature •, that is, altho' their eyes 
 turn and move always together ; yet, when they 
 look upon an objedt, the blind eye will often, 
 have a very fmall deviation from it ; which is 
 not perceived by a (light observer, but may be 
 difcerned by one accuftomed to make exact ob- 
 fervations in thefe matters. 
 
 S?CT. 
 
i 9 o Of the H U M A N Mt N D. Chap, tl 
 
 SECT. XI. 
 
 Of our feeing objetls ereB by inverted images. 
 
 A NOTHER phenomenon which hdth per- 
 ■"" plexed philofophers, is, our feeing objects 
 erect, when it is well known that their images 
 or picture's upon the tunica retina of the eye are 
 inverted. 
 
 The fagacious Kepler firft made the noble dis- 
 covery, That diftindt but inverted, pictures of 
 vifible objects, are formed upon the retina by the 
 rays of light coming from the object. The fame 
 great philOfopher demonftrated from the prin- 
 ciples of optics, how thefe pictures are formed, 
 to wit, That the rays coming from any one 
 point of the object, and falling upon the vari- 
 ous parts of the pupil, are, by the cornea and 
 chryftalline, refracted fo as to meet again in one 
 point of the retina, and there paint the colour of 
 that point of the object from which they come. 
 As the rays from different points of the object 
 crofs each other before they come to the retina, 
 the picture they form muft be inverted ; the up- 
 per part of, the object being painted upon the 
 lower part of the retina, the right fide of the ob- 
 ject upon the left of the retina, and fo of the 
 other parts. 
 
 This philofopher thought that we fee objects 
 erect by means of thefe inverted pictures, for 
 this reafon, That as the rays from different points 
 
 of 
 
Sect, ii. Of S£ El N G. tgi 
 
 of the object crofs each Other, before they fall 
 upon the rttind, we conclude that the impulfe 
 which we feel Upbn the lower part of the retina, 
 comes from above ; and that the impulfe which 
 we feel upon the higher part, conies from below. 
 Des Cartes afterwards gave the farrie folution 
 of this phenomenon, and illuftrated it by thfe 
 judgment which we form of the pdfitidh of ob- 
 jects which we feel with our arms crofled, or 
 with two flicks that crofs each other. 
 
 But we cannot acquiefce in this folutiori. 
 Firft, Becaufe it fuppofes our feeing things erect, 
 to be a deduction of reafon, drawn from certain 
 premifes : whereas it feems to be an immediate 
 perception. And, fecondly, Becaufe the pre- 
 mifes from which all mankind are fuppofed to 
 draw this conclusion, never entered into the minds 
 of the far greater part, but are abfolutely un- 
 known to them. We have no feeling or per- 
 ception of the pictures upon the retina, and as 
 little furely of the pofition of them. In order 
 to fee objects erect, according to the principles 
 of Kepler or Des Cartes, we muft previbufly 
 know, that the rays of light come from the ob- 
 ject to the eye in ftraight lines ; we muft know, 
 that the- rays from different points of the object 
 crofs one another, before they form the pictures 
 upon the . retina ; and laftly we muft know that 
 thefe pictures are really inverted. Now, althu' 
 all thefe things "are true, and known to philofo- 
 phers, yet they are abfolutely unknown to the 
 far greateft part of mankind : nor is it poflible 
 
 that 
 
i 9 2 Ofthe HUMAN MIND. Chap. VI. 
 that they who are abfolutely ignorant of them, 
 fliould reafon from them, and build conclufions 
 upon them. Since therefore vifible objects ap- 
 pear erect to the ignorant as well as to the learn- 
 ed, this cannot be a conclufion drawn from pre- 
 mifes which never entered into the minds ofthe 
 ianorant. We have indeed had occafion to bb- 
 ferve many inftances of conclufions drawn, either 
 by means of original principles, or by habit, 
 from premifes which pafs through the mind very 
 quickly, and which are never made the objects 
 of refle&ion ; but furely no man wilL conceive it. 
 pofiible to draw conclufions from premifes which 
 never entered into the mind at all. 
 
 Bifliop Berkeley having juftly rejected this fo- 
 lution gives one founded upon his own princi- 
 ples •, wherein he is followed by the judicious 
 Dr. Smith in his Optics j and this we fhall next 
 explain and examine. 
 
 That ingenious writer conceives the ideas of 
 fight to be altogether unlike thofe of touch. 
 And fince the notions we have of an object by 
 thefe different fenfes have no fimilitude, we can 
 learn only by experience how one fenfe will be 
 affected, by what, in a certain manner, affects 
 the other. Figure, pofition, and even number, 
 in tangible objects, are ideas of touch ; and al- 
 tho' there is no fimilitude between thefe and the 
 ideas of fight, yet we learn by experience, th-it 
 a triangle affects the fuht in fuch a manner, and 
 that a fquare affects it in fuch another manner : 
 hence we judge that which affects it in the firfl 
 
 manner, 
 
Sect, ii. Of SEEING. 193 
 
 manner, to be a triangle, and that which affe&s 
 it in the fecond, to be a fquare. In the fame 
 way, finding from experience, that an object 
 in an erect pofition, affects the eye in one 
 manner, and the fame object in an inverted po- 
 fition, affects it in another, we learn to judge, 
 by the manner in which the eye is affected, whe- 
 ther the object is erect or inverted. In a word, 
 vifible ideas, according to this author, are figns 
 of the tangible ; and the mind pafleth from the 
 fign to the thing fignified, not by means of any 
 fimilitude between the one and the other, nor by 
 any natural principle ; but by having found them 
 conftantly conjoined in experience, as the founds 
 of a language are with the things they fignify. 
 So that if the images upon the retina had been 
 always erect, they would have fhewn the objects 
 erect, in the manner as they do now that they 
 are inverted : nay, if the vifible idea which we 
 now have from an inverted object, had been affo- 
 ciated from the beginning with the erect pofi- 
 tion of that object, it would have fignified an 
 erect pofition, as readily as it now fignifies an in- 
 verted one. And if the vifible appearance of 
 two {hillings had been found connected from the 
 beginning with the tangible idea of one {hilling, 
 that appearance would as naturally and readily 
 have fignified the unity of the object, as now it 
 fignifies its duplicity. 
 
 This opinion is undoubtedly very ingenious ; 
 
 and, if it is juft, ferves to refolve, not only the 
 
 phenomenon now under confederation, but like- 
 
 N wjfe 
 
194 Of the HUMAN MIND. £hap. Vt 
 likewtfe that which we fhall next ebnfider, ouf 
 feeing objects fingle with two eyes. 
 
 It is evident, that in this folu^ion it is fuppo- 
 fed, that we do not originally, and previous to- 
 acquired habits, fee things either erect or invert- 
 ed, of one figure or another, fingle or double, 
 but learn from experience to judge of their tan- 
 gible pofition, figure, and number, by certain vi- 
 fibte figns. 
 
 Indeed it muft be acknowledged to be ex- 
 tremely difficult to diftinguifh the immediate and 
 natural objects of fight, from the conclufions 
 which we have been accuftomed from infancy to 
 draw from them. Bifhop Berkeley was the 
 firft that attempted to diftinguifh the one from 
 the other, and to trace out the boundary that 
 divides them. And, if in doing fo, he hath, 
 gone a little to the right hand or to the left, 
 this might be expected in a fubject altogether 
 new, and of, the greateft fubtilty. .The nature- 
 of vifion hath received great light from this dif- 
 tin&ion ; and manyphsnomena in optics, which 
 before appeared altogether unaccountable, have 
 been clearly and diftinctly refolved by it. . It is- 
 natural, and almoft unavoidable, to one who hath 
 made an important difcovery in philofophy, to 
 carry it a little beyond its fphere, and to ap- 
 ply it to the refolution of phenomena which 
 do not fall within its province. Even the great 
 Newton, when he had difcovered the univerfal 
 law of gravitation, and obferved how many of 
 the phenomena of nature depend upon this, and 
 
 other 
 
Sect, ii. Of SEEING. * 195 
 
 other laws of attraction and repulfion, could not 
 help expreffing his conjecture,, that all the phe- 
 nomena of the material world depend upon at- 
 tracting and repelling forces in the particles of 
 matter. And I fufpect that the ingenious Bifhop 
 of Cloyne, having found fo many phaenomena 
 of virion reducible to the conftant afibciation of 
 the ideas of fight and touch, carried this princi- 
 ple a little beyond its juft limits. 
 
 In order to judge as well as we can, whether 
 it is fo, let us fuppofe fuch a blind man as Dr. ' 
 Saunderfon, having ail the knowledge and abili- 
 ties which a blind man may have, fuddenly made 
 to fee perfectly. Let us fuppofe him kept from 
 all opportunities of afibciating his ideas of fight 
 with thofe of touch, until the former become a 
 little familiar ; and the firft furprife, occafioned 
 by objects fo new, being abated, he has time to 
 canvafs them, and to compare them, in his mind, 
 with the notions which he formerly had by 
 touch; and in particular to compare, in his mind, 
 that vifible extenfion which his eyes prefent, with 
 the extenfion in length and breadth with which 
 he was before acquainted. 
 
 We have endeavoured to prove, that a blind 
 man may form a notion of the vifible extenfion 
 and figure of bodies, from the relation which it 
 bears to their tangible extenfion and figure. 
 Much more, when this vifible extenfion and fi- 
 gure are prefented to his eye, will he be able to 
 compare them with tangible extenfion and figure, 
 and to perceive, that the one has length and 
 N 2 breadth 
 
196 OftheHUMAN MIND. Chap. VI. 
 breadth as well as the otfter; that the one may 
 be bounded by lines, either ftraight or curve, as 
 well as the other. And therefore, he will per- 
 ceive, that there may be vifible, as well as tangi- 
 ble circles, triangles, quadrilateral and multila- 
 teral figures. And altho' the vifible figure is 
 coloured, and the tangible is not, they may, not- 
 withftanding, have the fame figure ; as two ob- 
 jects of touch may have the fame figure, altho* 
 one is hot and the other cold. 
 
 We have demonftrated, that the properties of 
 vifible figures differ from thofe of the plain fi- 
 gures which they reprefent : but it was obferved 
 at the fame time, that when the objecT: is fo fmall 
 as to be feen diftinctly at one view, and is pla- 
 ced directly before the eye, the difference between 
 the vifible and the tangible figure is too fmall 
 to be perceived by the fenfes. Thus, it is true, 
 that of every vifible triangle, the three angles are 
 greater than two right angles ; whereas in a plain 
 triangle, the three angles are equal to two right 
 angles : but when the vifible triangle is fmall, 
 its three angles will be fo nearly equal to two 
 right angles, that the fenfe cannot difcern the dif- 
 ference. In like manner, the circumferences of 
 unequal vifible circles are not, but thofe of plain 
 circles are, in the ratio of their diameters ; yet 
 in fmall vifible circles, the circumferences are ve- 
 ry nearly in the ratio of their diameters; and 
 the diameter bears the fame ratio to the circum- 
 ference, as in a plain circle, very nearly. 
 
 Hence 
 
Se£t. ii. Of SEEING. 197 
 
 Hence it appears, that fmall vifible figures 
 (and fuch only can be feen diftinclly at one view) 
 have not only a refemblance to the plain tangible 
 figures which have the fame name, but are to all 
 fenfe the fame. So that if Dr. Saunderfon had 
 been made to fee, and had attentively viewed 
 the figures of the firft book of Euclid, he might, 
 by thought and confideration, without touching 
 them, have found out that they were the very 
 figures he was before fo well acquainted with by 
 touch. 
 
 When plain figures are feen obliquely, their 
 vifible figure differs more from the tangible ; and 
 the reprefentation which is made to the eye, of 
 folid figures, is ftill more imperfeft ; becaufe vi- 
 fible extenfion hath not three, but two dimen- 
 sions only. Yet as it cannot be faid that an exact 
 picture of a man hath no refemblance of the man, 
 or that a perfpective view of a houfe hath no re- 
 femblance of the houfe ; fo it cannot be faid, 
 with any propriety, that the vifible figure of a 
 man, or of a houfe, hath no refemblance of the 
 objects which they reprefent. 
 
 Bifhop Berkeley therefore proceeds upon a ca- 
 pital miftake, in fuppofing that there is no refem- 
 blance betwixt the extenfion, figure, and pofition 
 which we fee, and that which we perceive by 
 touch. 
 
 We may further obferve, that Bifhop Berke- 
 ley's fyftem, with regard to material things, mufl 
 have made him fee this queftion, of the erect ap- 
 pearance of objects, in a very different light from 
 N 3 that 
 
198 Ofthe HUMAN MIND. Chap. VI. 
 that in which it appears to thofe who do not 
 adopt his fyftem. 
 
 In his theory of vifion, he feems indeed to al- 
 low, that there is an external material world : 
 but he believed that this external world is tangi- 
 ble only, and not viable; and that the vifible 
 world, the proper object of fight, is not external, 
 but in the mind. If this is fuppofed, he that 
 affirms that he fees things erect and not inverted, 
 affirms that there is a top and a bottom, a right 
 and a left in the mind. Now, I confefs I am not 
 f® well acquainted with the topography of the 
 mind, as to be able to affix a meaning to thefe 
 words when applied to it., 
 
 We ihall therefore allow, that if vifible objects 
 were not external, but exifled only in the mind, 
 they could have no figure, or pofition, or ex- 
 tenfion •, and that it would be abfurd to affirm, 
 that they are feen either erect or inverted •, or 
 that there is any refemblance between them and 
 the objects of touch. But when we propofe the 
 queftion, Why obje&s are feen erect and not in- 
 verted ? we take it for granted, that we are not 
 in Bifliop Berkeley's ideal world, but in that 
 world which men, who yield to the dictates of 
 common fenfe, believe themfelves to inhabit. 
 We take it for granted, that the objects both of 
 fight and of touch, are external, and have a cer- 
 tain figure, and a certain polition with regard to 
 one another, and with regard to our bodies, whe- 
 ther we perceive it or not. 
 
 When 
 
Sect, i r. , Of S E E I N G. 199 
 
 "When I hold my .walking-cane upright in my 
 hand, and look at it, I take it for granted, that 
 I fee and handle the fame individual object. When 
 I fay that I feel it erect, my meaning is, that I 
 feel the head directed from the horizon, and the 
 point directed towards it : and when I fay that 
 I fee it erect, I mean that I fee it with the head 
 directed from the horizon, and the point towards 
 it. I conceive the horizon as a fixed object both 
 of fight and touch, with relation to which, ob- 
 jects are faid to be high or low, erect or invert- 
 ed : and when the queftion is afked, Why I fee 
 the object erect, and not inverted ? it is the 
 fame as if you mould afk, Why I fee it in that 
 pofition which it realiy hath ? or, Why the eye 
 fliows the real pofition of objects, and doth not 
 ihow them in an inverted pofition, as they are 
 feen by a common aftronomical telefcope, or as 
 their pictures are feen upon the retina of an eye 
 when it is diffected ? 
 
 S E C T. XII. 
 
 _ The, fame fubjeSl continued. 
 
 TT is ifnpoffible to give a fatisfactory anfwer to 
 this queftion, otherwife than by pointing out 
 
 the laws of nature which take place in vifion ; 
 
 for by thefe the phenomena of vifion muft be 
 
 regulated. , 
 
 Therefore I anfwer, Firft, That, by a law of 
 
 nature the rays of light proceed from every point 
 N 4 of 
 
200 Ofthe HUMAN MIND. Chap. VI. 
 of the object to the pupil of the eye in ftraight 
 lines. Secondly, That, by the laws of nature, the 
 rays coming from any one point of the object to 
 the various parts of the pupil, are fo refradled, 
 as to meet again in one point of the retina; and 
 the rays from different points of the object, firft 
 croffiog each other, and then proceeding to as 
 many different points of the retina % form an in- 
 verted picture of the object. 
 
 So, far the principles of optics carry us; and 
 experience further aflbres us, that if there is no 
 fuch picture upon the retina, there is no vifion ; 
 and that fuch as the picture on the retina is, fuch 
 is the appearance of the object, in colour and fi- 
 gure, diftindtnefs or indiftinctnefs, brightnefs or 
 faintnefs. 
 
 It is evident, therefore, that the pictures upon 
 the retina are, by the laws of nature, a mean of 
 vifion; but in what way they accomplifh their 
 end, we are totally ignorant. Philofophers con- 
 ceive, that the impreifion made on the retina by 
 the rays of light, is communicated to the optic 
 nerve, and by the optic nerve conveyed to fome 
 part of the brain, by them called the fenforium ; 
 and that the impreffion thus conveyed to the fen- 
 fcrium is immediately perceived by the mind, 
 which is fuppofed to refide there. But we know 
 nothing of the feat of the foul: and we are fo 
 far from perceiving immediately what is tranfr 
 a,£ted in the brain, that of all parts of the hu- 
 man body we know leaft about it. It is indeed 
 very probable, that the, optic nerve is an inftru- 
 
 ment 
 
Seft. re. Of S E E IN G. aoi 
 
 ment of vifion no lefs neceffary than the retina j 
 and that fome impreffion is made -upon it, by 
 means of the pictures on the retina. But of what 
 kind this impreffion is, we know nothing; 
 
 There is not the leaft probability, that there 
 is any picture or image of the object either in the 
 optic nerve or brain. The pictures on the retina 
 are formed by the rays of light; and whether 
 we fuppofe, with fome, that their impulfe upon 
 the retina caufes fome vibration of the fibres of 
 the optic nerve j or, with others, that it gives 
 motion to fome fubtile fluid contained in the 
 nerve; neither that vibration, nor this motion, 
 can refemble the vifible object which is prefent- 
 ed to the mind. Nor is there any probability; 
 that the mind perceives the pictures upon the 
 retina. Thefe pictures are no more objects of our 
 perception, than the brain is,' or the optic nerve. 
 No man ever faw the pictures in his own eye; 
 nor indeed the pictures in the eye of another, un- 
 til it was taken out of the head, and duly pre- 
 pared. 
 
 It is very ftrange, that philofophers, of all 
 ages, fhould have agreed in this notion, That the 
 images of external objects are conveyed by the 
 organs of fenfe to the brain, and are there per- 
 ceived by the mind. Nothing can be more un> 
 philofophical. For, firft, This notion hath no 
 foundation in fact and obfervation. Of all the 
 organs of fenfe, the eye only, as far as we can 
 difcover, forms any kind of image of its object j 
 and the images formed by the eye are not in the 
 
 brain, 
 
202 Of the H U M A N M I N D. Chap. VI. 
 brain, but only in the bottom of the eye •, nor 
 are they at all perceived or felt by the mind. 
 Secondly, It is as difficult to conceive how the 
 mind perceives images in the brain, as, how it 
 perceives things more diftant. If any man will 
 fhew how the mind may perceive images in the 
 brain, I will undertake to (hew how it may per- 
 ceive the moft diftant objects : for if we give 
 eyes to the mind, to perceive what is tranfadled 
 at home in its dark chamber, why may we not 
 make thefe eyes a little longer-lighted ? and then 
 we (hall have no occafion for that unphilofophi- 
 cal fi&ion of images in the brain. In a word, the 
 manner and mechanifm of the mind's perception 
 is quite beyond our comprehenfion : and this 
 way of explaining it by images in the brain, 
 feems to be founded upon very grofs notions of 
 the mind and its operations ; as if the fuppofed 
 images in the brain, by a kind of contacf r form- 
 ed limilar impreffioris or images of objefts upon 
 the mind, of which impreffions it is fuppofed to 
 be confcious. 
 
 We have endeavoured to fhew, throughout 
 the courfe of this inquiry, that the impreffions 
 made upon the mind by means of the five fenfes, 
 have not the leaft refemblance to the objefts of 
 fenfe : and therefore, as we fee no fhadow of 
 evidence, that there are any fuch images in the 
 brain, fo we fee no purpofe, in philofophy, that 
 the fuppofition of them can anfwer. Since the 
 picture upon the retina therefore is neither itfelf 
 feen by _the mind, nor produces any impreffion 
 
 upon 
 
Seft. 12. Of SEEING. 203 
 
 upon the brain or fenforium, which is feen by 
 the mind, nor makes any impreffion upon the 
 mind that refembles the object, it may ftill be 
 afked, How this picture upon the retina caufes 
 vifion ? 
 
 Before we anfwer this queftion, it is proper 
 to obferve, that in the operations of the mind, 
 as well as in thofe of bodies, we muft often be 
 fatisfied with knowing, that certain things are 
 connected, and invariably follow one another, 
 without being able to difcover the chain that 
 goes between them. It is to fuch connections 
 that we give the name of laws of nature; and 
 when we fay that one thing produces another 
 by a law of nature, this fignifies no more, but 
 that one thing, which we call in popular lan- 
 guage the caufe, is constantly and invariably fol- 
 lowed by another, which we call the effebl ; and 
 that we know not how they are connected. 
 Thus, we fee it is a fa£t, that bodies gravitate 
 towards bodies •, and that this gravitation- is re- 
 gulated by certain mathematical proportions, 
 according to the diftances of the bodies from 
 each other, and their quantities of matter. Be- 
 ing unable to difcover the caufe of this gravita- 
 tion, and prefuming that it is the immediate 
 operation, either of the Author of nature, or of 
 fome fubordinate caufe, which we have not 
 hitherto been able to reach, we call it a law of 
 nature. '■ If any philofopher mould hereafter be 
 fo happy as to difcover the caufe of gravitation, 
 t<hjs can only be done by difcovering fome more 
 
 general 
 
2 o4 Of the H U M A N M I N D. Chap. VI. 
 general law of nature, of which the gravitation 
 of bodies is a neceffary confequence. In every 
 chain of natural caufes, the higheft link is a 
 primary law of nature •, and the higheft link 
 which we can trace, by juft induction, is either 
 this primary law of nature, or a neceffary con- 
 fequence of it. To trace out the laws of nature, 
 by induction, from the phaenomena of nature, is 
 all that true philofophy aims at, and all that it 
 can ever reach. 
 
 There are laws of nature by which the ope- 
 rations of the mind are regulated ; there are 
 aifo laws of nature that govern the material 
 fyftem : and as the latter are the ultimate con- 
 dufions which the human faculties can reach in 
 the pffilofophy of bodies, fo the former are the 
 ultimate conclufions we can reach in the philo- 
 fophy of minds. 
 
 To return, therefore, to the queftion above 
 ptopofed, we may fee, from what hath been 
 juft now obferved, that it amounts to this, By 
 what law of nature is a picture upon the retina y 
 the mean or occafion of my feeing an external 
 object of the fame figure and colour, in a con- 
 trary petition, and in a certain direction from 
 the eye ? 
 
 It will, without doubt, be allowed, that I 
 fee: the whole object in the fame manner and by 
 the fame law by which I fee any one point of it. 
 Now, I know it to be a fact, that, in direct 
 vifion, I fee every point of the object in the 
 direction of the right line that pafieth from the 
 
 centre 
 
Sect. 12. Of SEEING. -105 
 
 centre of the eye to that point of the objectj 
 and I know likewhe, from optics, that the ray 
 of light that comes to the centre of my eye, 
 paffes on to the retina in the fame direction. 
 Hence it appears to be a fact, that every point 
 of the object is feen in the direction of a right 
 line pafllng from the picture of that point on the 
 retina through the centre of the eye. As this 
 is a fact that holds univerfally and invariably, it 
 muft either be a law of nature, or the neceflary 
 confequence of fome more general law of nature. 
 And according to thejuft rules of philofophizing, 
 we may hold it for a law of nature, until fome 
 more general law be difcovered, whereof it is 
 a neceflary confequence, which I fufpect can 
 never be done. 
 
 Thus we fee, that the phaenomena of vifion 
 lead us by the hand to a Jaw of nature, or 
 a law of our conftitution, of which law our 
 feeing objects erect by inverted images, is a 
 neceflary confequence. For it neceflarjly fol- 
 lows, from the law we have mentioned, that 
 the object whbfe picture is loweft on the retina, 
 muft be feen in the higheft direction from the 
 eye; and that the object whofe picture; is on 
 the right of the retina, muft be feen on the 
 left-, fo that if the pictures hacl been erect in 
 the, retina, we fhould have fee^n the object in- 
 serted. My chief intention in handling this 
 queftion, was to point put this law of nature ; 
 which as it is a part of the conftitution of the 
 human mind, belongs properly to the fubject of 
 
 this 
 
io6 Of the H U M A N M 1 N D. Chap, VI. 
 this inquiry. For this reafon I (hall make fome 
 farther remarks upon it, after doing juftice to 
 the ingenious Dr. Porterfield, who, long ago in 
 the ' Medical Effays, or more lately in his 
 Treatife of the Eye, pointed out, as a primary 
 law of our nature, That a vifible object appears 
 in the- direftion.of a right line perpendicular to 
 the retina at that point where its image is paint- 
 ed. If lines drawn from the centre of the eye 
 to all parts of the retina be perpendicular to it, 
 as they muft be very nearly, this coincides with 
 the law we have mentioned, and is the fame in 
 other words. In order, therefore, that we may 
 have a more diftin<5t notion of this law of our 
 conftitution, we may obferve, 
 
 i. That we can give no reafon why the 
 retina is, of all parts of the body, the only one 
 on which pictures made by the rays of light 
 caufe vifion •, and therefore we muft refolve this 
 folely into a law of our conftitution. We may 
 form fuch pictures by means of optical glafies, 
 upon the hand, or upon any other' part of the 
 body; but they are not felt, nor do they pro- 
 duce any thing like vifion. A picture upon the 
 retina is as little felt as one- upon the hand ; bur 
 it produces vifion •, for no other reafon that we 
 know, but becaufe it is deftined by the wifdom 
 of nature to this pnrpofe. The vibrations of 
 the air ftrike upon the eye, the palate, and the 
 olfactory membrane, with the fame force as upon 
 the membrani tympani of the ear : The impref- 
 fion they make upon the laft, produces the fen- 
 
 fation 
 
Scft. 12. Of S E E I N G. 207 
 
 fatipn of found ; but their impreffion upon any 
 of the former, produces no fenfation at all. This 
 may be extended to all the fenfes, whereof each 
 hath its peculiar laws, according to which, the 
 impreffions made upon the organ of that fenfe, 
 produce fenfations or perceptions in the mind, 
 that cannot be produced by impreffions made 
 upon any other organ. 
 
 2. We may obferve, that the laws of per- 
 ception, by the different fenfes, are very dif- 
 ferent, not only in refpeet of the nature of the 
 objeds perceived by them, but likewife in re- 
 fpecVof the notices they give us of the diftance 
 and fituation of the object. In all of them the 
 object is conceived to be external, and to have 
 real exiftence, independent of our perception : 
 but in one, the diftance, figure, and fituation of 
 the object, are all prefented to the mind ; ia 
 another, the figure and fituation, but not the 
 diftance ; and in others, neither figure, fituation, 
 nor difbtnce. In vain do we attempt to account 
 for thefe varieties in the manner of perception 
 by the different fenfes^ from principles of ana- 
 tomy or natural phllofophy. They muft at laft 
 be refolved into the will of our Maker, who in- 
 tended that our powers of perception fhould have 
 certain limits, and adapted the organs of percep- 
 tion, and the laws of nature by which they ope- 
 rate, to his wife purpofes. 
 
 When we hear an unufual found, the fenfa* 
 
 tion indeed is in the mind, but we know that 
 
 there is fomething external that produced this 
 
 1 found. 
 
2o8 OftheHUMAN MIND. Chap. VI* 
 found. At the fame time our hearing does not 
 inform us, whether the founding body is near 
 or at a diftance, in this direction or that ; and 
 therefore we look round to difcover it. 
 
 If any new phasnomenon appears in the hea- 
 vens, we fee exactly its colour, its apparent 
 place, magnitude, and figure, but we fee not its 
 diftance. It may be in the atmofphere, it may 
 be among the planets, of it may be in the fphere 
 of the fixed ftars, for any thing the eye can de- 
 termine. 
 
 The teftimony of the fenfe of touch reaches 
 only to objects that are contiguous to the or- 
 gan, but with regard to them, is more precife 
 and determinate. When we feel a body with 
 our hand, we know the figure, diftance, and 
 pofition of it, as well as whether it is rough or 
 fmooth, hard or foft, hot or cold. 
 
 The fenfations of touch, of feeing, and hear- 
 ing, are all in the mind, and can have no exift- 
 ence but when they are perceived. How do 
 they all conftantly and invariably fuggeft the 
 conception and belief of external objects, which 
 exift whether they are perceived or not ? No 
 philofopher can give any other anfwer to this, 
 but that fuch is the conftitution of our nature. 
 How do we know, that the object of touch is 
 at the fingers end, and no where elfe ? That the 
 object of fight is in fuch a direction from the 
 eye, and in no other, but may be at any di- 
 ftance ? and that the object of hearing may be 
 at any diftance, and in any dire&ion ? Not by 
 
 cuftom 
 
Se<5t. 12. Of S E E I N G. 209 
 
 cuftom furely; not by reafoning, or comparing 
 ideas, but by the conftitution of our nature. 
 How do we perceive vifible objects in the di- 
 rection of right lines perpendicular to that part 
 of the 'retina on which the rays ftrike, while 
 we do not perceive the objects of hearing in 
 lines perpendicular to the membrana tympanic 
 upon which the vibrations of the air ftrike ? Be- 
 caufe fuch are the laws of our nature. How 
 do we know the parts of our bodies affected by 
 particular pains ? Not by experience or by rea- 
 foning, but by the conftitution of nature. The 
 fenfation of pain is, no doubt, in the mind, and 
 cannot be faid to have any relation, from its own 
 nature, to any part of the body ^ but this fenfa- 
 tion,. by.our conftitution, gives a perception of 
 fome particular part of the body, whbfe diforder 
 caufes the uneafy. fenfation. If it were not fo, 
 a man who never before felt either the gout or 
 the- toothach, when he is firltifeized with .the , 
 gout in his toe,, might m'jftake it for the tooth- 
 ache ' . . „-',", ",_;.; 
 
 Every fenfe therefore rhath its peculiar laws - 
 and limits, by the -conftitution of oar nature; 
 and one of the laws of fight is, That .we always 
 fee an object in the direction of a right line.pak. ,; 
 fing from its image on the retina- through the - 
 centre of the eye. c -. 
 
 3. Perhaps fome readers will imaginei that 
 
 it is. eafier, "and will anfwer the purpofeas well, 
 
 to conceive a law: of nature, by which, we fhall 
 
 always fee objects in the place in which* they are, 
 
 O and 
 
aio Of the HUMAN MIND. Chap. VI. 
 and in their true pofition, without having re- 
 courfe to images on the retina, or to the optical 
 centre of the eye. 
 
 To this I anfwer, That nothing can be a law of 
 nature which is contrary to fact. The laws of 
 nature are the m oft general facts we; can difcover 
 in the operations of nature. Like other facts, they 
 are not to be hit upon by a happy conjecture, but 
 juftly deduced from obfervation : Like other ge- 
 neral facts, they are not to be drawn from a few 
 particulars, but from a copious, patient, and 
 cautious induction. That we fee things always 
 in their true place and pofition, is not fa«5b ; and 
 therefore it can be no law of nature. In a plain 
 mirror, I fee myfelf, and other things, in places 
 very different from thofe they really occupy. 
 And fo it happens in every inftance, v wherein 
 the rays coming from the object are either re- 
 flected or refracted before falling upon the eye. 
 Thofe who know any thing of optics, know 
 that, in all fuch cafes, the object is feen in the 
 direction of a line paffyig from the centre of the 
 eye, to the point where the rays were laft re- 
 flected or refracted ; and that upon this all the 
 powers of the telefcope and microfcope depend. 
 
 Shall we fay then, that it is a law of nature, 
 that the object is feen in the direction which the 
 rays have when they fall on the eye, or rather 
 in the direction contrary to that of the rays 
 ■when they fall upon the eye ? No. This is not 
 true, and therefore it is no law of nature. For 
 the rays, from any one point of the object, come 
 
 to 
 
Se£hi2. t)£ SEEING. dii 
 
 to all parts of the pupil ; and therefore muft have 
 different directions k but we fee the object only 
 ihonedf thefedireftionsi to wit, in the direction 
 of the rays that come to the centre of the eye. 
 And this holds true, even when the rays that 
 fhould pafs through the centre are ftopt, and the 
 object is feen by rays that pafs at a diftance front 
 the centre. 
 
 Perhaps it may ftill be imagined, that alcho* 
 we are not made fb as to fee objects always in 
 their true place, nor fo as to fee them precifely 
 in the direction of the rays when they falPupon 
 the cornea •, yet we may be fo made, as to fee 
 the object in the direction Which the rays have 
 when they fall upon the retina,, after they have 
 undergone all their refractions in the eye, that 
 is, in the direction in which the rays pafs from 
 the cryftalline to the retina. But neither is this 
 true ; and confequently it is ho law of our con- 
 stitution. In order to fee that it is not true, we 
 muft conceive all the rays that pafs from the 
 cryftalline to one point of the retina, as forming 
 a fmall cone, whofe bafe is upon the back of the 
 cryftalline, and whofe vertex is a point of the 
 retina. It is eVident that the rays which form 
 the picture in this point, have various directions^ 
 even after they pafs the Cryftalline ; yet the ob- 
 ject is feen only in one of thefe directions, to wit$, 
 in the direction of the rays that come from the 
 centre of the eye. Nor is this owing to any 
 particular virtue in the central rays, or in the 
 centre itfelf j for the central rays may be ftopt. 
 O 2 When 
 
2i2 Ofthe HUMAN MIND. Chap. VI. 
 When they are ftopt, the image will be formed 
 upon the fame point of the retina as before, by 
 rays that are not central, nor have the fame 
 direction which the central rays had : and in 
 this cafe the object is feen in the fame direction 
 as before, altho' there are now no rays coming 
 in that direction. 
 
 From this indu&ion we conclude, That our 
 feeing an objecl: in tliat particular direction in 
 which we do fee it, is not owing to any law of 
 nature by which we are made to fee it in the 
 direction of the rays, either before their refrac- 
 tions in the eye, or after, but to a law of our 
 nature, by which we fee the object in the direc- 
 tion of the right line that pafleth from the pic- 
 ture of the object upon the retina to the centre 
 of the eye. 
 
 The facts upon which I ground this induction, 
 are taken from fome curious experiments of 
 Scheiner, in his Fundament. Optic, quoted by Dr. 
 Porterfield, and confirmed by his experience. I 
 have alfo repeated thefe experiments, and found 
 them to anfwer. As they are eafily made, and 
 tend to illuftrate and confirm the law of nature I 
 have mentioned, I (hall recite them as briefly and 
 diftinctly as I can. 
 
 Experiment I. Let a very fmall object, fuch 
 as the head of a pin, well illuminated, be fix- 
 ed at fuch a diftance from the eye, as to be be- 
 yond the neareft limit and within the fartheft 
 limit of diftinct vifion. For a young eye, not 
 rcear-fighted, the object may be placed at the 
 
 diftance 
 
"Seft. 12. Gf SEEING. 213 
 
 diftance of eighteen inches. Let the eye be 
 kept fteadily in one place, and take a diftindt 
 view of the object. We know from the princi- 
 ples of optics, that the rays from any one point 
 of this object, whether they pafs thro' the cen*. 
 tre of the eye, or at any diftance from the centre 
 which the breadth of the pupil will permit, do 
 all unite again in one point of the retina. We 
 know alfo, that thefe rays have different direc- 
 tions, both before they fall upon the eye, and af» 
 ter they pafs through the cryftalline. 
 
 Now we can fee the object by any one fmall 
 parcel of thefe rays, excluding the reft,, by look- 
 ing thro' a fmall pin-hole in a card. Moving 
 this pin-hole over the various parts of the pupil, 
 we can fee the object, firft by the rays that pafs 
 above the centre of the eye, then by the central 
 rays, then by the rays that pafs below the centre, 
 and in like manner by the rays that pafs on the 
 right and left of the centre. Thus, we view 
 this object, fucceffively, by rays that are 
 central, and by rays that are not central ; by 
 rays that have different directions, and are vari- 
 ouQy inclined to each other, both when they 
 fall upon the cornea^ and when they fall upon 
 the retina ; but always, by rays which fall upon 
 the fame point of the retina. And what is the 
 event ? It is this, that the object is feen in the 
 fame individual direction, whether feen by all 
 thefe rays together, or by any one parcel of 
 them. 
 
 O 3 Experiment 
 
*i 4 Ofthe HUMAN MIND. Cha^. VI, 
 Experiment 2. Let the object above mentis 
 oned be now placed within, the neareft limit of 
 diftinct vifion, that is, for an eye that is not 
 near-fighted, at the diftance of four or five inches. 
 We know, that in this cafe, the rays coming 
 from one point of the object, do not meet in 
 one point of the retina, but fpread over a fmall 
 circular fpot of it •, the central rays occupying 
 the centre of this circle, the rays that pafs above 
 the centre occupying the upper part of the cir- 
 cular fpot, and fo of the reft. And we know 
 that the object is in. this cafe feen confufed, eve- 
 ry point of it being feen, not in one, but in va- 
 rious directions. To remedy this confufion, we 
 look at the object thro' the pin-hole, and while 
 we move the pin-hole over the various parts of 
 the pupil, the object, does not keep its place, 
 but leems to move in a cpntrary dire£tion. 
 
 It is here to be obferved, that when the 
 pin-hole is' carried upwards over the pupil, the 
 picture of the object is carried upwards upon the 
 retina, and the object at the fame time feems to 
 move downwards, fo as to be always in the right 
 line paffing from the picture thrp' the centre of 
 the eye. It is likewife to be obferved, that the 
 rays which form the upper and the lower pic- 
 tures upon the retina, do not crofs each other as, 
 in ordinary vifion ; yet ftill the higher pifture 
 fliews the object lower, and the lower picture 
 ihews the object higher, in the fame manner as 
 when the rays crofs each other. "Whence we 
 rnaj cbferve, by the way, that this phaenome- 
 
 non, 
 
Sc&. i a. Of SEEING. 215 
 
 non of our feeing objects in a pofuion contrary 
 to that of their pictures upon the retina, does 
 not depend upon the croffing of the rays, as 
 Ifepler and Des Cartes conceived. 
 
 Experiment 3. Other things remaining as in 
 the laft experiment, make three pin-holes in a 
 ftraight line, fo near, that the rays coming from 
 the object thro' all the holes, may enter the pu- 
 pil at the fame time^ In this cafe we have a ve- 
 ry curious phaenomenon ; for the object is feen 
 triple with one eye. And if you make more 
 holes within the breadth of the £>upil, you will 
 fee as many objects as there are holes. How- 
 ever, we (hall fuppofe them only three ; one on 
 the right, one in the middle, and one on the left; 
 in which cafe you fee three objects ftanding in a 
 line from right to left. 
 
 It is here to be obferved, that there are three 
 pictures on the retina ; that on the left being 
 formed by the rays which pafs on the left of the 
 eye's centre ; the middle pifture being formed 
 by the central rays, and the right-hand picture by 
 the rays which pafs on the right of the eye's cen- 
 tre. It is farther to be obferved, that the abject 
 which appears on the right, is not that which is 
 feen thro' the hole on the right, but that which 
 is feen thro' the hole on the left ; and in like 
 manner, the left-hand object is feen thro' the 
 hole on the right, as is eafily proved by cover- 
 ing the holes fucceflively. So that, whatever is 
 the direction of the rays which form the right- 
 h$nd and left hand pictures, ftill the right-hand 
 O 4 picture 
 
216 Ofthe HUMAN MIND. Chap. VI. 
 picture fhows a left-hand object, and the left- 
 hand picture fhows a right-hand object. 
 
 Experiment 4. It is eafy to fee how the two 
 laft experiments may be varied, by placing the 
 object beyond the fartheft limit of diftinct vi- 
 fion. In order to make this experiment, I look- 
 ed at a candle at the diftance of ten feet, and put 
 the eye of my fpectacles behind the card, that 
 the rays from the fame point ofthe object might 
 meet, and crofs each other, before they reached 
 the retina. In this cafe ? as in the former, the 
 candje was feen triple through the three pin-: 
 holes ; buc the candle on the right, was feen 
 thro' the hole on the right ; and, on the contra- 
 ry, the left-hand candle was feen trjro' the hole 
 on the left. In this experiment it is evident 
 from the principles of optics, that the rays forr 
 rning the feveral pictures on the retina, crofs each 
 other a little before they reach the retina ; and 
 therefore the left-hand picture is formed by the 
 rays which pafs thro' the hole on the right: fo that 
 the pofition of the pictures is contrary to that of 
 the holes by which they are formed ; and there- 
 fore is alfo contrary to that of their objects, as 
 we have found it to be in the former expert? 
 ments. 
 
 Thefe experiments exhibit feyeral uncommon 
 phenomena, that regard the apparent place, and 
 the direction of vifible objects from the eye; 
 phenomena that feem to be moft contrary to the • 
 common rules of yifion. \Yher} we look at the 
 
 fame 
 
Sett. 12. Of SEEING. 217 
 
 fame time through three holes that are in a right 
 line, and at certain diftances from each other, 
 we expeft, that the objects feen through them 
 fhould really be, and fhould appear to be, at a dis- 
 tance from each other : Yet, by the firft expe- 
 riment, we may, through three fuch holes, fee 
 the fame object, and the fame point of that ob- 
 ject ; and through all the three it appears in the 
 fame individual place and direction. 
 
 When the rays of light come from the ob- 
 ject in right lines to the eye, without any re- 
 flexion, inflexion, or refraction^ we expect, that 
 the object fhould appear in its real and proper di- 
 rection from the eye -, and fo it, commonly does : 
 But in thefecond, third, and fourth experiments, 
 we fee the object in a direction which is not its 
 true and real direction from the eye, altho' the 
 rays come from the object to the eye, without 
 any inflexion, reflexion, or refraction. 
 
 "When both the object and the eye are fixed 
 without the leaft motion, and the medium un- 
 changed, we expeCt, that the object fhould ap- 
 pear to reft, and keep the fame place : Yet in 
 the fecond and fourth experiments, when both 
 the eye and the object are at reft, and the me- 
 dium unchanged, we make the object appear to 
 move upwards or downwards, or in any direction 
 we pleafe. 
 
 When we look at the fame time, and with 
 the fame eye, through holes that ftand in a line 
 from right to left, we expect, that the object feen 
 through the left-hand hple fhould appear on the 
 
2i8 Ofthe HUMAN MIND. Chap. VI. 
 k r c, and the object feen through the right-hand 
 hole, fhould appear on the right: Yet in the 
 third experiment, we find the direft contrary. 
 Altho* many instances occur in feeing the fame 
 ^ tjfd du^i-'e with two eyes, we always expect, 
 t; vi.; it fhould appear fingle when feen only by 
 oiiv eye : Yet in the fecond and fourth experi- 
 ments, we have inftances wherein the fame ob- 
 ject may appear double, triple, or quadruple to 
 one eye, without the help of a polyhedron or 
 multiplying glafs. 
 
 All thefe "extraordinary phenomena, regarding 
 the direction of vifible objects from the eye, as 
 well as thofe that are common and ordinary, lead 
 us to that law of nature which I have mentioned, 
 and are the neceflary confequences of it. And, 
 as there is no probability that we fhall ever be 
 able to give a reafon why pictures upon the retina 
 make us fee external objects, any more than pic- 
 tures upon the hand or upon the cheek ; or, that 
 we fhall ever be able to give a reafon, why we 
 fee the object in the direction of a line pafling 
 from its picture through the centre, of the eye, 
 rather than in any other direction ; I am there- 
 fore apt to look upon this law as a primary law 
 of our conftitution. 
 
 To prevent being mifunderftood, I beg the 
 reader to obferve, that I do not mean to affirm, 
 that the picture upon the retina will make us fee 
 an object in the direction mentioned, or in any 
 direction, unlefs the optic nerve, and the other 
 more immediate inftruments of vifion, be found, 
 
 and 
 
Seft. 12. Of SEEING. 219 
 
 and perform their funf^oxu We know not well 
 what is the office of the optic nerve, nor in what 
 manner if performs that office ; but that it hath 
 fome part in the faculty of feeing, feems to be 
 certain j becaufe in an amaurofu, which is be- 
 lieved to be a diforder of the optic nerve, the 
 pictures on the retina are clear and diftindt, and 
 yet there is no vifion. 
 
 We know (till lefs of the ufe and function of 
 the choroid membrane; but it feems likewle" to 
 be neceflary to vifion : for it is well known, that 
 pictures upon that part of the retina where it is 
 not covered by the choroid, I mean at the en- 
 trance of the optic nerve, produce no vifion, any 
 more than a picture upon the hand. We ac- 
 knowledge, therefore, that the retina is not the 
 laft and moft immediate inftrument of the mind 
 in vifion. There-are other material organs, whofe 
 operation is neceflary to feeing, even after the 
 piiflures upon the retina are formed. If ever we 
 pome to know the ftrufture and ufe of the cho- 
 roid membrane, the optic nerve, and the brain, and 
 what impreffions are made upon them by means 
 of the pictures on the retina, fome more links of 
 the chain may be brought within our view, and a 
 more general law of vifion difcovered : but while 
 we know fo little of the nature and office of thefe 
 more immediate inftruments of vifion, it feems to 
 be impoffible to trace its laws beyond the pictures 
 upon the retina. 
 
 Neither do I pretend to fay, that. there may 
 
 not be difeafes of the eye, or accidents, which 
 
 7 may 
 
220 Of the HUMAN MIND. Chap. VI. 
 
 mayoccafionour feeingobjects in a direction fome- 
 what different from that mentioned above. I 
 fhall beg leave to mention one inftance of this 
 kind that concerns myfelf. 
 
 In May 1761, being occupied in making an 
 exact meridian, in order to obferve the tranfit of 
 Venus, I rafhly directed to the fun, by my right, 
 eye, the crofs hairs of a fmall telefcope. I had 
 often done the like in my younger days with im- 
 punity •, but I fuffered by it at laft, which I men- 
 tion as a warning to others. 
 
 I foon obferved a remarkable dimnefs in that 
 eye ; and for many weeks, when I was in the 
 dark, or fhut my eyes, there appeared before the 
 right eye a lucid fpot, which trembled much like 
 the image of the fun feen by reflection from wa- 
 ter. This appearance grew fainter, and lefs fre- 
 quent by degrees ; fo that now there are feldom 
 any remains of it. But fome other very fenfible 
 effects of this hurt ftill remain. For, firft, The 
 fight of the right eye continues to be more dim 
 than that of the left. Secondly, The nearefl: limit 
 of diftinct virion is more remote in the right eye 
 than in the other ; altho', before the time men- 
 tioned, they were equal in both thefe refpects, as 
 I had found by many trials. But, thirdly, what 
 I chiefly intended to mention is, That a ftraight 
 line, in fome circumftances, appears to the right 
 eye to have a curvature in it. Thus, when I 
 look upon a mufic-book, and, ftiuttjng my left 
 eye, direct the right to a point of the middle 
 line of the five which, compofe.#ie ftaff pf mufic ; 
 
 the 
 
Sect. 12. Of S E E I N G. 221 
 
 the middle line appears dim indeed, at the point 
 to which the eye is directed, but ftraight; at 
 the fame time the two lines above it, and the 
 two below it, appear to be bent outwards, and 
 to be more diftant from each other, and from 
 the middle line, than at other parts of the ftaff, 
 to which the eye is not directed. Fourthly, 
 Altho' I have repeated this experiment times in- 
 numerable, within thefe fixteen months, I do not 
 find that cuftom and experience takes away this 
 appearance of curvature in ftraight lines. Laft- 
 ly, This appearance of curvature is perceptible 
 when I look with the right eye only, but not 
 when I look with both eyes ; yet I fee better 
 with both eyes together, than even with the left 
 eye alone. 
 
 I have related this fact minutely as it is, with- 
 out regard to any hypothefis; becaufe I think 
 fuch uncommon fads deferve to be recorded. I 
 fhall leave it to others to conjecture the caufe of 
 this appearance. To me it feems moil probable, 
 that a fmall part of the retina towards the centre is 
 fhrunk, and that thereby the contiguous parts are 
 drawn nearer to the centre, and to one another, 
 than they were before; and that objects whofe 
 images fall on thefe parts, appear at that diftance 
 from each other which correfponds, not to the 
 interval of the parts in their prefent preternatu- 
 ral contraction, but to their interval in their na- 
 tural and found flate. 
 
 SECT. 
 
222 Of the HUMAN MIND. Chap. VL 
 
 SECT. XIII. 
 
 Of feeing objeSts fingle with two eyes. 
 
 A Nother phenomenon of vifion which de- 
 ferves attention, is our feeing objects fingle 
 with two eyes. There are two pictures of the 
 object, one on each retina ; and each picture by 
 itfelf makes us fee an object in a certain direc- 
 tion from the eye : yet both together common- 
 ly make us fee only one object. All the accounts 
 or folutions of this phenomenon given by anato* 
 mifts and philofophers, feem to be unfatisfactory. 
 I (hall pafs over the opinions of Galen, of Gaf- 
 fendus, of Baptifta Porta, and of Rohault. The 
 reader may fee thefe examined and refuted by 
 Dr. Porterfield. I fhall examine Dr. Porterfield's 
 own opinion, Bifhop Berkeley's, and fome others. 
 But it will be neceffary firft to afcertain the facts ; 
 for if we miftake the phenomena of fingle and 
 double vifion, it is ten to one but this miftake 
 will lead us wrong in affigning the caufes. This 
 likewife we ought carefully to attend to, which is 
 acknowledged in theory by all who have any true 
 judgment or juft tafte in inquiries of this nature, 
 but is very often overlooked in practice, name- 
 ly, That in the folution of natural phenomena, 
 all the iength that the human faculties can carry 
 us, is only this, that from particular phenomena, 
 we may, by induction, trace out general pheno- 
 mena, of which all the particular ones are necef- 
 
 fary 
 
Sea. 13. Of SEEING. 223 
 
 fary confequences. And when we have arrived 
 at the moft general phenomena we can reach, 
 there we muft flop. If it is alked, Why fuch a 
 body gravitates towards the earth ? all the an- 
 fwer that can be given is, Becaufe all bodies gra- 
 vitate towards the earth. This is refolving a par- 
 ticular phenomenon into a general one. If it 
 fhould again be alked, Why do all bodies gravi- 
 tate towards the earth ? we can give no other 
 folation of this phenomenon, but that all bodies 
 whatfoever gravitate towards each other. This 
 is refolving a general phenomenon into a more 
 general one. If it fhould be alked, Why all bo- 
 dies gravitate to one another ? we cannot tell ; 
 but if we could tell, it could only be by refol- 
 ving this univerfal gravitation of bodies into fome 
 ether phenomenon ftill more general, and of 
 which the gravitation of all bodies is a particular 
 inftance. The moft general phenomena we can 
 reach, are what we call laws of nature. So that 
 the laws of nature are nothing elfe but the moft 
 general facts relating to the operations of nature, 
 which include a great many particular facts un- 
 der them. And if in any cafe we fhould give- 
 the name of a law of nature to a general pheno- 
 menon, which human induftry fhall afterwards 
 trace to one more general, there is no great 
 harm done. The moft general afiumes the name 
 of a law of nature, when it is difcovered; and 
 the lefs general is contained and comprehended in 
 k. Having premifed thefe things, we proceed to 
 conflder the phenomena of fingie and double vi- 
 
 fion, 
 
224 Of the HUMAN MIND. Chap. VI. 
 fion, in order to difcover fome general principle 
 to which, they all lead, and of which they are the 
 neceffary confequences. If we can difcover any 
 fuch general principle, it muft either be a law of 
 nature, or the neceffary confequence of fome law 
 of nature ; and its authority will be equal, whe- 
 ther it is the firft or the laftl 
 
 i. We find, that when the eyes are found 
 and perfect, and the axes of both directed to one 
 point, an object placed in that point is leen An- 
 gle : and here we obferve, that in this cafe the 
 two pictures which fhow the object fingle, are in 
 the centres of the retina. When two pictures of 
 a fmall object are formed upon points of the re- 
 tina, if they fhow the object fingle, we fhall, for 
 the fake of perfpicuity, call fuch two points of the 
 retina, correfponding points; and where the ob- 
 ject is feen double, we fhall call the points of the 
 retina on which the pictures are formed, points 
 that do not correspond. Now, in this firft phasno- 
 menon it is evident, that the two centres of the 
 retina are correfponding points. 
 
 2. Suppofing the fame things as in the laft 
 phenomenon, other objects at the fame diftance 
 from the eyes as that to which their axes are di- 
 rected, do alfo appear fingle. Thus, if I direct 
 my eyes to a candle placed at the diftance of ten 
 feet ; and, while I look at this candle, another 
 ftands at the fame diftance from my eyes, within 
 the field of vifion ; I can, while I look at the 
 firft candle, attend to the appearance which the 
 fecond makes to the eye; and I find that in this 
 
 cafe 
 6 
 
Sed, 13. Of SEEING. 225 
 
 cafe it always appears fingle. It is here to be ob- 
 ferved, that the pictures of the fecond candle do 
 not fall upon the centres of the retina, but they 
 both fall upon the fame fide of the centres, that 
 is, both to the right, or both to the left, and 
 both are at the fame diftance from the centres. 
 This might eafily be demonflrated from the prin- 
 ciples of optics. Hence it appears, that in this fe- 
 cond phenomenon of fingle virion, the corre- 
 fponding points are pointsof the tvroretina, which 
 are fimilarly fituate with refpect to the two 
 centres, being both upon the fame fide of the 
 centre, and at the fame diftance from it. It ap- 
 pears likewife from this phenomenon, that every 
 point in one retina correfponds with that which 
 is fimilarly fituate in the other. 
 
 3. Suppofing ftill the fame things, objects 
 which are much nearer to the eyes, or much 
 more diftant from them, than that to which the 
 two eyes are directed, appear double. Thus, if 
 the candle is placed at the diftance of ten feet, 
 and I hold my finger at arms-length between my 
 eyes and the candle; when I look at the candle, 
 I fee my finger double •, and when I look at my 
 finger, I fee the candle double : And the fame 
 thing happens with regard to all other objects at 
 like diftances which fall within the fphere of vs- 
 fion. In this phenomenon it is evident to thofe 
 who understand the principles of optics, that the 
 pictures of the objects which are feen double, do 
 not fall upon points of the retina which are fimi- 
 larly fituate, but that the pictures of the objects 
 P ken 
 
226 Of the H U M A N M I N D. Chap. VI. 
 feen fingle do fall upon points fimilarly fuuate. 
 "Whence we infer, that as the points of the two 
 retina, which are fimilarly fituate with regard to 
 the centres, do correfpond, fo thofe which are 
 diffimilarly fituate do not correfpond. 
 
 4. It is to be obfcrved, that altho', in fuch 
 cafes as are mentioned in the laft phenomenon, 
 we have been accuftomed from infancy to fee ob- 
 jects double which we know to be fingle ; yet 
 cuftom, and experience of the unity of the ob- 
 ject, never take away this appearance of dupli- 
 city. 
 
 5. It may however be remarked, that the cu- 
 • ftom of attending to vifible appearances has a 
 
 con (iderable effect, and makes the phsenomenon 
 of double vifion to be more or lefs obferved and 
 remembered. Thus you may find a man that can 
 fay with a good confcience, that he never faw 
 thingsdouble all his life; yet this very man, put 
 in the fituation above mentioned, with his finger 
 between him and the candle, and defired to at- 
 tend to the appearance of the object which he 
 does not look at, will, upon the firft trial, fee 
 the candle double, when he looks at his finger; 
 and his finger double, when he looks at the can- 
 dle. Does he now fee otherwife than he faw 
 before? No, furely; but he now attends to 
 what he never attended to before. The fame 
 double appearance of an object hath been a thou- 
 sand times prefented to his eye before now ; but 
 fie "did not attend to it; and fo it is as little an 
 
 object 
 
Seft. 13. Of S E E 1 N C. ay 
 
 Object of his reflection and memory, as if it had 
 never happened. 
 
 When we look at an object, the circumja- 
 cent objects may be feen at the fame time, al* 
 tho' more obfcurely and indiftinctly : for the eye 1 
 hath a considerable field of vifion, which intakes 
 in at once. But we attend only to the object we 
 look at. The other objects which fall within the 
 field of vifion, are not attended to ; and there- 
 fore are as if they were not feen. If any of them 
 draws our attention, it naturally draws the eyes 
 at the fame time : for in the common courfe of 
 life, the eyes always follow the attention : or if 
 at any time, in a reverie, they are feparated from 
 it, we hardly at that time fee what is directly be- 
 fore us. Hence we may fee the reafon, why the 
 man we are fpeaking of, thinks that he never be- 
 fore faw an object double. When he looks at 
 any object, he fees it fingle, and takes no notice 
 of other vifible objects at that time, whether they 
 appear fingle or double. If any of them draws 
 his attention, it draws his eyes at the fame time 4 
 and as foon as the eyes are turned towards it, it 
 appears fingle. But in order to fee things double, 
 at leaft in order to have any reflexion or remem-* 
 brance that he did fo, it is necefiary that he 
 Ihould look at one object, and at the fame time 
 attend to the faint appearance of other objects' 
 which are within the field of vifion. This is a 
 practice which perhaps he never ufed, nor at-> 
 tempted ; and therefore he does not recollect 
 that ever he faw an object double. B-ut when he 
 P 2 is 
 
228 Of the HUM AN MIND. Chap. VI. 
 is put upon giving this attention, he immediately 
 fees objects double in the fame manner, and with 
 the very fame circumftancts, as they who have 
 been accuftomed, for the greateft part of their 
 lives, to give this attention. 
 
 There are many phsenomena of a fimilar na- 
 ture, which ihew, that the mind may not at- 
 tend to, and thereby, in fome fort, not per- 
 ceive object.-, that ftrike the fenfes. I had pc- 
 cafion to mention fevera-1 instances of this in the 
 fecond chapter •, and I have been allured, by 
 perfons of the beft flcill in mufic, that in hearing 
 a tune upon the harpflchprd, when they give 
 attention to the treble, they do, not hear the 
 bafs •, and when they attend to the bafs, they 
 do not perceive the air of the treble. Some 
 perfons are fo near- fighted, that, in reading, 
 they hold the book to one eye, while the other 
 is directed to other objects. Such perfons ac- 
 quire the habit of attending in this cafe to the 
 objects of one eye, while they give no attention 
 to thofe of the other. 
 
 6. It is obfervable, that in all cafes wherein 
 we fee an object double, the two appearances 
 have a certain pofition with regard to one ano- 
 ther, and a certain apparent or angular diftance. 
 This apparent diftance is greater or lefs in diffe- 
 rent circumftances ; but in the fame circum- 
 ftances, it is always the fame, not only to the 
 fame, but to different perfons. 
 
 Thus, in the experiment above mentioned, if 
 twenty different perfons, who fee perfectly with 
 
 both 
 
Setit. 13. Of SEEING. 229 
 
 both eyes, fhall ptece their fin'ger and the candle 
 at the d'i#a'nces above expre'ffed, and hold their , 
 heads upright ;• looking at the finger, they will 
 fee two cages', one on the right, another on 
 the left. That whiefo is feen on the right, is 
 feen by the right eye, and that which is feen on 
 the left, by the left eye ; and they will fee 
 them at t:he fame apparent diftance from each 
 other. If again they look at the candle, they 
 wiM fee two fingers, one on the right, and the 
 other on the left; and all will ; fee them at the 
 fame apparent diftance ; the finger towards the 
 left being feen by the right eye, and the other 
 by the left. If the head is hid' horizontally to 
 onefide, other circurhrtances remaining' the fame, 
 One appearance of the objeil: feen double, will 
 be direttly above the other. In a word, vary 
 thecircumftarices as-you'-ple-.fe, and the appear- 
 ances' are varied to- all the fpedtatbris in one and' 
 the fame manner. 
 
 7. Having' made many experiments in order 
 to afcertain the apparent diftance of the two- 
 appearances of an Object feen double, I have 
 found that' in all<cafes this apparent diftance is 
 proportioned to the diftance between the point 
 of the retina, where the picture is made in one 
 eye, and the point which is fituated fimilarly to 
 that on which the picture is made on .the other 
 eye. So that as the apparent diftance of two 
 objects feen with one eye, is proportioned to 
 the arch of the retina, which lies between their 
 piiftures ; in like manner, when an object is 
 P 3 feen 
 
2 3 o Ofthe HUMAN MIND. Chap. VI. 
 
 feen double with the two eyes, the apparent 
 diftance of the two appearances is proportioned 
 to the arch of either retina, which lies between 
 the picture in that retina, and the point corre- 
 sponding to that of the picture in the other 
 retina. 
 
 8. As in certain circumftances we invariably 
 fee one obje<St appear double, fo in others we 
 as invariably fee two objects unite into one ; 
 and, in appearance, lofe their duplicity. This 
 is evident in the appearance of the binocular 
 telefcope. And the fame thing happens when 
 any [two fimilar tubes are applied to the two 
 eyes in a parallel direction ; for in this cafe we 
 fee only one tube. And if two {hillings are 
 placed at the extremities of the two tubes, one 
 exactly in the axis of one eye, and the other in 
 the axis of the other eye, we {hall fee but one 
 fhilling. If two pieces of coin, or other bodies, 
 of different colour, and of different figure, be 
 properly placed in the two axes of the eyes, and 
 at the extremities of the tubes, we (hall fee 
 both the bodies in one and the fame place, each 
 as it were fpread over the other, without hiding 
 it ; and the cqlour will be that which is com- 
 pounded of the two colours,. 
 
 9. From thefe phenomena, and from all _the 
 trials I have been able to make, it appears evi- 
 dently, that in perfect human eyes, the centres 
 of the two retina correfpond and harmonize with 
 one another ; and that every other point in one 
 retina, doth correfpond and harmonize with the 
 
 point, 
 
Scd. 13. Of SEEING. 231 
 
 point which is fimilarly fituate in the other; in 
 fuch manner, that pictures falling on the cor- 
 refpondihg points of the two retina, fhew only 
 one object, even when there are really two : 
 and pictures falling upon points of the retina 
 which do not correfpond, fhew us two vifible 
 appearances, altho' there be but one object. So 
 that pictures, upon correfponding points of the 
 two retina, prefent the fame appearance to the 
 mind as if they had both fallen upon the fame 
 point of one retina ; and pictures upon points of 
 the two retina, which do not correfpond, prefent 
 to the mind the fame apparent diftance and po- 
 fition of two objects, as if one of thofe pictures 
 was carried to the point correfpodning to it in 
 the other retina. This relation and fympathy 
 between correfponding points of the two retina, 
 I do not advance as a hypothefis, but as a gene- 
 ral fact or phenomenon of vifion. All the.phs- 
 nomena before mentioned, of fingle or double 
 vifion, lead to it, and are neceflary confequences 
 of it. It holds true invariably in all perfect hu- 
 man eyes, as far as I am able to collect from 
 innumerable trials of various kinds made upon 
 my own eyes, and many made by others at my 
 deQre. Moll of the hypothefes that have been 
 contrived to refolve the phenomena of fingle and 
 double vifion, fuppofe this general fact, while 
 their authors were not aware of it. Sir Ifaac 
 Newton, who was too judicious a philofopher, 
 and too accurate an obferver, to have offered 
 $ven a conjecture which did not tally with the 
 P 4 facts 
 
232 Of the HUMAN MIND, Ch.ip.VJ. 
 
 fa us that had fallen under his obfervation, pro- 
 pofes a query with refpect to the caufe of it, 
 Optics, quer. 15. The judicious Dr. Smith, in 
 his Optics, lib. i. § 137. hath confirmed, the 
 truth of this general phenomenon from his own 
 experience, not only as to the apparent unity of 
 objects whofe pictures fall upon the correspond- 
 ing points of the retina^ but alfo as to the ap- 
 parent diftance of the two appearances of the 
 fame object' when feea double. 
 
 This general phsenomenon appears therefore 
 to be founded upon a very full induction, which 
 is all the evidence we can have for a fact of this 
 nature. Before we make an end of this fubject, 
 it will be proper to inquire, firft, Whether thofe 
 animals whofe eyes have an adverfe pofition in 
 their heads, and look contrary ways, have fuch 
 correfponding points in their retina? Secondly, 
 \Vhat,is the pofition of the correfponding points 
 in imperfect human eyes, I mean in thofe that 
 fquint ? And, in the laft place, Whether this 
 harmony of the correfponding points in the re- 
 tina, be natural and original, or the effect of 
 cufiom ? And if it is original, Whether it can 
 be accounted for by any of the. laws of nature 
 already discovered ? or whether it is itfelf to be 
 looked upon as a law of nature, and a part of 
 the human constitution ? 
 
 SECT. 
 
Sea. 14. Of SEEING. ag 3 
 
 SECT. XIV. 
 
 Of the laws, of vifion in hrute animals. 
 
 T T is the intention of nature, in giving eyes., 
 to animals, that they may perceive the fituar 
 tion of vifible objects, or the direction in which, 
 they are placed : it is, probable, therefore, that,, 
 in ordinary cafes, every animal, whether it has 
 many eyes or few, whether of one ftructure or 
 of another, fees objects fingle, and in their true, 
 and proper direction. And fince there is a pro- 
 digious variety in the ftructure, the motions, 
 and the number of eyes in different animate and 
 infects, it is probable that the laws by which vi- 
 fion is regulated, are not the fame in all, but 
 various, adapted to the eyes which nature hath 
 given them. 
 
 Mankind naturally turn their eyes always the 
 fame way, fo that the axes of the two eyes meet 
 in one point. They naturally attend to, or 
 look at that object only which is placed in the 
 point where the axes meet. And whether the 
 object be more or lefs diftant, the configuration 
 of the eye is adapted to the diftance of the ob- 
 ject, fo as to form a diftinct picture of it. 
 
 When we ufe our eyes in this natural way, 
 the two pictures of the object we look at, are 
 formed upon the centres of the two retina ; and 
 fhe two pictures of any contiguous object are 
 formed upon the points of the retina which are 
 
 fiinilarly 
 
2 3 + Of the HUM AN MIND. Chap. VI. 
 fimilarly fituate with regard to the centres. 
 Therefore, in order to our feeing objeils fingle, 
 and in their proper direction, with two eyes, it 
 is fufficient that we be fo conftituted, that ob- 
 jects whofe pictures are formed upon the centres 
 of the two retina, or upon points fimilarly fituate 
 with regard to thefe centres, (hall be feen in 
 the fame vifible place. And this is the confti- 
 tution which nature hath actually given to hu- 
 man eyes. 
 
 When we diftort our eyes from their parallel 
 direction, which is an unnatural motion, but 
 may be learned by practice ; or when we direct 
 the axes of the two eyes to one point, and at 
 the fame time direct our attention to fome vifible 
 object much nearer or much more diftant than 
 that point, which is alio unnatural, yet may be 
 learned •, in thefe cafes, and in thefe only, we 
 fee one object double, or two objects confound- 
 ed in one. In thefe cafes, the two pictures of 
 the fame object are formed upon points of the 
 retina which are not fimilarly fituate, and fo the 
 object is feen double ; or the two pictures of 
 different objects are formed upon points of the 
 retina which are fimilarly fituate, and fo the two 
 objects are feen confounded in one place. 
 
 Thus it appears, that the laws of vifion in 
 the human conftitution are wifely adapted to the 
 natural ufe of human eyes, but not to that ufe 
 of them which is unnatural. We fee objects 
 truly when we ufe our eyes in the natural way; 
 but have falfe appearances prefented to us when 
 
 we 
 
sea. 7. of seeing; 235 
 
 we ufe them in a way that is unnatural. We 
 may reafonably think, that the cafe is the fame 
 with other animals. But is it not unreafonable 
 to think, that thofe animals which naturally turn 
 one eye towards one object, and another eye 
 towards another object, muft thereby have fuch 
 falfe appearances prefented to them, as we have 
 when we do fo againft nature ? 
 
 Many animals have their eyes by nature pla- 
 ced adverfe and immoveable, the axes of the two 
 eyes being always directed to oppofite points. 
 Do objects painted on the centres of the two 
 retina appears to fuch animals as they do to hu- 
 man eyes, in one and the fame vifible place ? I 
 think it is highly probable that they do not ; 
 and that they appear, as they really are, in op- 
 pofite places. 
 
 If we judge from analogy in this cafe, it will 
 lead us to think that there is a certain corre- 
 fpondence between points of the two retina in 
 fuch animals, but of a different kind from that 
 which we have found in human eyes. The 
 centre of one retina will correfpond with the 
 centre of the other, in fuch manner, that the 
 objects whofe pictures are formed upon thefe 
 correfponding points, fhall appear not to be in 
 the fame place, as in human eyes, but in oppo- 
 fite places. And in the fame manner will the 
 fuperior part of one retina correfpond with the 
 inferior part of the other, and the anterior part 
 of one with the pofterior part of the other. 
 
 .„ Some 
 
£' 3 6 Ofthe HUMAN MIND. Chap. VI. 
 
 Some! animals, by nature^ tuarn their eyeswith 
 equal' facility, either the fame way, or different 
 ways, as we tarn our hands and armsi Have 
 fuch animals correfpond'ing points in their retime, 
 and points which do n©t correfpond, as the 
 human kind has ? I think it is probable that they 
 have not •, becauie fuch a constitution in them 
 could ferve no other purpofe but to exhibit falfe 
 appearances. 
 
 If we judge from analogy, it wills lead' us to 
 thittk, that as fuch animals move their eyes in a 
 manner Similar to that in which wemove our arms, 
 they have an immediate and: natural perception 
 of the direction they give to-their eyes, as'-we have' 
 of the direction we give tooaf arms; and perceive' 
 the-ff.uaiion of vifible objedte-by. their eyes-, in a-' 
 manner fimilar to that in which we perceive the' 
 fituacionof tangible objects- with-our- hands-. 
 
 -We- can-not teach brute animals to* ufe their- 
 eyes in any other way than in that which na- 
 ture hath taught them ; nor can- we teach them- 
 to communicate to us the appearances which vi- 
 fible objects-make to them, either in ordinary or 
 in extraordinary cafes,. We have noE therefore' 
 the fame means; of difcovering the laws of virion 
 in them-, as in our own- kind, bur muft fatisfy 
 ourfelves with probable conjectures': and what 
 we have faid: upon this fubjeci:, is chiefly intend- 
 ed to (hew, that animals ta^jjich nature hath 
 given eyes differing in their number, in their po- 
 fition, and in their, natural motions, may very 
 probably be fubjesfted. to different laws of virion, 
 
 adapted 
 
Sect, 14. Of S E E I N G. . 237 
 
 adapted to the peculiarities of their organs of 
 vifion. 
 
 SECT. XV. 
 
 Squinting conjidered hypothetically. 
 
 "VUL^Hetber there be correfponding points 
 in the retina, of thofe who have an invo- 
 luntary fquint? and if there are, whether they 
 be fituate in the fame manner as in thofe who 
 have no fquint ? are not queftions of mere curi- 
 ofity. They are of real importance to the phy- 
 fician who attempts the cure of a fquint, and to 
 the patient who fubmits to the cure. After fo 
 much hath been faid of the Jlrabifmus t or 
 fquint, both by medical and by optical writers, 
 one might exoedl to find abundance of facts for 
 determining thefe queftions. Yet I confefs I 
 have been difappointed in this expectation, after 
 taking fome pains both to make obfervations, 
 and 1 to collect thofe which have been made by 
 others. 
 
 Nor will this appear very ftrange, if we con- 
 fider that to make the obfervations which are 
 neceffary for determining thefe queftions, know- 
 ledge of the principles, of optics, and of the laws 
 of vifion, muft concur with opportunities rare- 
 ly to be met with. 
 
 Of thofe who fquint, the far greater part have 
 no diftinct vifion with one eye. When this is 
 the cafe, it is impoflible, and indeed of no im- 
 portance,. 
 
238 Ofthe HUMAN MIND. Chap. VI. 
 portance, to determine the fituation of the cor- 
 refponding points. When both eyes are good, 
 they commonly differ fo much in their direction, 
 that the fame objecl cannot be feen by both at 
 the fame time ; and in this cafe it will be very 
 difficult to determine the fituation of the corre- 
 fponding points ; for fuch perfons will probably 
 attend only to the objecls of one eye, and the 
 objecls of the other will be as little regarded as 
 if they were not feen. 
 
 We have before obferved, that when we look 
 at a near object, and attend to it, we do not 
 perceive the double appearances of more diftant 
 objefts, even when they are in the fame direc- 
 tion, and are prefented to the eye at the fame 
 time. It is probable that a fquinting perfon, 
 when he attends to the objecls of one eye, will, 
 in like manner, have his attention totally divert- 
 ed from the obje&s, of the other : and that he 
 will perceive them as little as we perceive the 
 double appearances of objecls when we ufe our 
 eyes in the natural way. Such a perfon, there- 
 fore, unltrfs he is fo much a philofopher as to 
 have acquired the habit of attending very accu- 
 rately to the vifible appearances of objecls, and 
 even of objecls which he does not look at, will 
 not be able to give any light to the queftions 
 now under confideration. 
 
 Ic is very probable that hares, rabbits, birds, 
 and fifties, whofe eyes are fixed in an adverfe po- 
 fition, have the natural faculty of attending at 
 the fame time to vifible objecls placed in differ- 
 
Sea. 15. Of S E E I N ; G. 239 
 
 enr, and even in contrary directions ;- becaufe» 
 without this faculty, they could not have thofe 
 advantages from the contrary; direction of their 
 eyes, which nature feems to have intended. But 
 it is not probable that thofe wh'o'fquint have any 
 fuch natural faculty ; becaufe we find no fuch 
 faculty in the reft of the fpecies. We naturally 
 attend to objects placed in the point where the 
 axes of the two eyes meet, and to them only. 
 To give attention to an object in a different di- 
 rection is unnatural, and not to be learned with- 
 out pains and practice. 
 
 A very convincing proof of this may be drawn 
 from a fact now well known to philofophers : 
 when one eye is fhut, there is a certain fpace with- 
 in the field of vifion, where we can fee nothing at 
 all ; the fpace which is directly oppofed to that 
 part of the bottom of the eye where the optic 
 nerve enters. This defect of fight, in one part of 
 the eye, is common to all human eyes, and hath 
 been fo from the beginning of the world •, yet it 
 was never known, until the fagacity of the Ab- 
 be Mariotte difcovered it in the laft century. 
 And now when it is known, it cannot be per- 
 ceived, but by means of fome particular expe- 
 riments, which require care and attention to make 
 them fucceed. 
 
 What is the reafon that fo remarkable a de- 
 fect of fight, common to all mankind, was fo 
 long unknown, and is now perceived with fo 
 much difficulty ? It is furely this, That the de- 
 fect is at fome diftance from the axis of the eye, 
 
 and 
 
240 Of the HU M A N M I N D. Chap. VL 
 and corifequently in a pare of the field of virion 
 to vyhich we never attend natur My, and to 
 which we cannot attend at all, without the aid 
 of fome particular circumftances. 
 
 From what we have faid, it appears, that, to 
 determine the -fituation of the correfponding 
 points in the eyes of thofe that fquint, is impof- 
 fible, if they do not. fee diftinctly with both eyes ; 
 and that it will be very difficult-, unlefs the two 
 eyes differ fo little in their direction, that the 
 fame objedt may be feen with both at the fame 
 time. Such patients I apprehend are rare •, at 
 leaft there are very few of them with whom I 
 have had the fortune to meet : and therefore, 
 for the affiftance of thofe who may have happier 
 opportunities, and inclination to make the pro- 
 per ufe of them, we ihall confider the cafe of 
 fquinting hypothetically, pointing out the pro- 
 per articles of inquiry, the obfervations that are 
 wanted, and the conclusions that may be drawn 
 from them. 
 
 i. It ought to be inquired, "Whether the 
 fquinting perlbn fees equally well with both eyes ? 
 and, if there be a clefecl in one, the nature and 
 degree of that defect Ought to be remarked. The 
 experiments by which this may be done, are fo 
 obvious, that I need not mention them. But I 
 would advife the obferver to make the proper 
 experiments, and not to rely upon the tefti- 
 mony of the patient ; becaufe I have found 
 many inftances, both of perfons that fquinted, 
 and others, who were found, upon trial, to 
 have a great defect in the fight of one eye, 
 
 altho* 
 
Sett. 15. Of SEEING. 241 
 
 alr.ho' they were never aware of it before. 
 In all the following articles, it is fuppofed that 
 the patient fees with both eyes fo well, as to be 
 able to read with either, when the other is co- 
 vered. 
 
 2. It ought to be inquired, Whether, when 
 one eye is covered, the other is turned directly 
 to the object ? This ought to be tried in both 
 eyes fucceffively. By this obfervation, as a touch- 
 ftone, we may try the hypothefis concerning 
 fquinting, invented by M. de la Hire, and adopt- 
 ed by Boerhaave, and many others of the medi- 
 cal faculty. 
 
 The hypothefis is, That in one eye of a fquint- 
 ing perfon, the greateft fenfibility and the moft 
 diftinct vifion is not, as in other men, in' the 
 centre of the retina, but upon one fide of the 
 centre ; and that he turns the axis of this eye 
 afide from the object, in order that the picture of 
 the object may fall upon the moft fenfible part 
 of the retina, and thereby give the moft diftinct 
 vifion. If this is the caufe of fquinting, the 
 fquinting eye- will be turned afide from the ob- 
 ject, when the other eye is covered, as well as 
 when it is not. 
 
 A trial fo eafy to be made, never was made 
 for more than forty years ; but the hypothefis 
 was very generally received. So prone are men 
 to invent hypothefes, and fo backward to exa- 
 mine them by facts. At laft.Dr. Jurin having 
 made the trial, found that- perfons who fquint, 
 turn the axis of the fquinting tye directly to the 
 
 Q^ object, 
 
242 Of the H U M A N M I N D. Chap., JJ r 
 object, when the other eye is covered. This fact 
 is confirmed by Dr. Porterfieldi and I have found 
 it verified in all the inftances that have fallen un- 
 der my obfervation. 
 
 3. It ought to be inquired, Whether the axes 
 of the two eyes follow one another, lb as to have 
 always the fame inclination, or make the fame 
 angle, when the perfon looks to the right or to 
 the left, upward or downward, or ftraight for- 
 ward. By this obfervation we may judge, whe- 
 ther a fquint is owing to any defect in the muf- 
 cles which move the eye, as fome havefuppofed. 
 In the following articles we fuppofe that^the in- 
 clination of the axes of the eyes is found -to be 
 always the fame. 
 
 4. It ought to be inquired, Whether the per- 
 fon that fquints fees an object fingle or double ? 
 
 If he fees the object double; and if the two 
 appearances have an angular diftance equal to the 
 angle which the axes of h'is eyes make with each 
 other, it may be concluded that he hath corre- 
 fponding points in the retina of his eyes,, and that ■ 
 they have the fame fituation as. in thofe who 
 have no fquint.. If the two appearances fhould 
 have an angular diftance which is always the fame, 
 but manifeftly greater or lefs than the angle con- 
 tained under the optic axes, this would indicate 
 correfponding points, in the retina, whofe fitua- 
 tion is not the fame as in thole who have no 
 fquint ; but it is difficult to judge' accurately of 
 the angle which the optic axes make. 
 
 A 
 
Sect. 15. Of SEEING. 243 
 
 A fquint too fmall to be perceived, may oc- 
 Gafion double vifion of objects : for if we fpeak 
 ftrictly, every perfon fquints more or lefs, whofe 
 optic axes do not meet exactly in the object 
 which he looks at. Thus, if a man can only bring 
 the axes of *his eyes to be parallel, but cannot 
 make them converge in the leaft,' he muft have 
 a fmall fquint in looking at near objects, and will 
 fee them double, while he fees very diftant ob- 
 jects fingle. Again, if the optic axes always con- 
 verge, fo as to meet eight or ten feet before the 
 face at fartheft, fuch a perfon will fee near ob- 
 jects fingle ; but when he looks at very diftant 
 objects, he will fquint a little, and fee them dou- 
 ble. 
 
 An inftance of this kind is related by Aguilo- 
 nius in his Optics ; who fays, that, he had fee'h a 
 young man to whom near objects appeared fingle, 
 but diftant objects appeared double. 
 
 Dr. Briggs, in his Nova vifionis theoria, ha- 
 ving collected from authors feveral inftances of 
 double vifiori, quotes this from Aguilonius, as the 
 rnoft wonderful and unaccountable of all, in fo 
 much that he fu (beets fome impofition on the 
 part of the young man : but to thofe who under- 
 stand the laws by which fingle and double vifion 
 are regulated, it appears to be the natural effect 
 of a very fmall fquint. 
 
 Double vifion may always be owing to a fmall 
 fquint, when the two appearances are feen at a 
 fmall angular diftance, altho 5 no fquint was ob- 
 ferved : and I do hot remember any inftances of 
 
 (^ 2 double 
 
244 Of the HUMAN MIND. Chap.Vfc 
 double vifion recorded by authors, wherein any 
 account is given of the angular diftance of the 
 appearances. 
 
 In almoft all the inftances of double vifion, 
 there is reafon to fufpect a fquint or diftortion of 
 the eyes, from the concomitant circumftances, 
 which we find to be one or other of the follow- 
 ing, the approach of death, or of a deliquium, ex- 
 ceffive drinking, or other intemperance, violent 
 headach, bliftering the head, fmoaking tobacco, 
 blows or wounds in the head. In all thefe cafes,, 
 it is reafonable to fufpect a diftortion of the eyes,, 
 either from fpafm, or paralyfis in the mufcles that 
 move them. But altho' it be probable that there 
 is always a fquint greater or lefs where there is. 
 double vifion ; yet it is certain that there is not 
 double vifion always where there is a fquint. I 
 know no inftance of double vifion that continued 
 for life, or even for a great number of years. We 
 fhall therefore fuppofe, in the following articles,, 
 that the fquinting perfon fees objects fingle. 
 
 5. The next inquiry then ought to be, Whe- 
 ther the object is feen with both eyes at the fame 
 time, or only with the eye whofe axis is directed 
 to it ? It hath been taken for granted, by the 
 writers upon the Jlrabifmus, before Dr. Jurin, 
 that thofe who fquint, commonly fee objects 
 fingle with both eyes at the fame time ; but I 
 know not one fact advanced by any writer which, 
 proves it. Dr. Jurin is of a contrary opinion; and 
 as it is of confequence, fo it is very eafy, to de- 
 termine this point in particular inftances, by this 
 
 obvious 
 
Sect. 15. Of S E E I N G. 245 
 
 obvious experiment. While the perfon that fquints 
 looks fteadily at an object, let the obfervef care- 
 fully remark the direction of both his eyes, and 
 obferve their motions ; and let an opaque body 
 be interpofed between the object and the two 
 «yes fucceffively. If the patient, notwithstanding 
 this interpofition, and without changing the di- 
 rection of his eyes, continues to fee the object 
 all the time, it may be concluded that he faw it 
 with both eyes at once. But if the interpofition 
 of the body between one eye and the object, 
 makes it difappear, then we may be certain, that 
 it was feen by that eye only. In the two follow- 
 ing articles, we (hall fuppofe the firft to happen, 
 according to the common hypothefis. 
 
 6. Upon this fuppofition, it ought to be in- 
 quired, Whether the patient fees an object dou- 
 ble in thofe circumftances wherein it appears dou- 
 ble to them who have no fquint ? Let him, for 
 inftance, place a candle at the diftance of ten 
 feet ; and holding his finger at arm's length be- 
 tween him and the candle, let him obferve, when 
 he looks at the candle, whether he fees his finger 
 with both eyes, and whether he fees it fingle or 
 double; and when he looks at his finger, let him 
 obferve whether he fees the candle with both 
 eyes, and whether fingle or double. 
 
 -By this obfervation, it may be determined, 
 whether to this patient, the phenomena of dou- 
 ble as well as of fingle vifion are the fame as to 
 them who have no fquint. If they are not the 
 fame; if he fees objects fingle with two eyes, 
 
 0^3 not 
 
246 Of the HUMAN MIND. Chap. VI. 
 
 not only in the cafes wherein they appear fingle, 
 but in thofe alfo wherein they appear double to 
 other men ; the conclufion to be drawn from this 
 fuppofition is, that his fingle vifion does not arife 
 from ccrrefponding points in the retina of his 
 eyes-, and that the laws of vifion are not the 
 fame in him as in the reft of mankind. 
 
 7. If, on the other hand, he fees objects dou- 
 ble in thofe cafes wherein they appear double to 
 others, the conclufion muft be, that he hath corr 
 refponding points in the retina of his eyes, but 
 unnaturally fituate ; and their fituation may be 
 thus determined. 
 
 When he looks at an object, having the axis 
 of one eye directed to it, and the axis of the 
 other turned afide from it ; let us fuppofe a right 
 line to pafs from the objeft through the centre 
 of the diverging eye. We fhall, for the fake of 
 perfpicuity, call this right line the natural axis of 
 the eye: and it. will make an angle with the real 
 axis, greater or lefs, according as his fquint is 
 greater or lefs. We fhall alfo call that point of 
 the retina in which the natural axis cuts it, the 
 natural centre of the retina ; which will be more 
 or lefs diftant from the real, centre, according as 
 the fquint is greater or lefs. 
 
 Having premifed thefe definitions, it will be 
 evident to thofe who underftand the principles of 
 optics, that in this perfon the natural centre of 
 one retina correfponds with the real centre of 
 the other, in the very fame manner as the two 
 real centres correfpond in perfect eyes ; and that 
 
 the 
 
Seft. 15. Of SEEING. 247 
 
 the ..points fimilarly fituate with regard to the* 
 real centre in one retina, and the natural centre 
 in the other, do likewife correfpond, in the very 
 fame manner as the points fimilarly fituate with 
 regard to the two real centres correfpond in per- 
 fect eyes. 
 
 If it is true, as has been commonly affirmed, 
 that one who fquints fees an object with both 
 eyes at the fame time, and yet fees it fingle, the 
 fquint will moft probably be fuch as we have de- 
 fcribed in this article. And we may further con- 
 clude, that if a perfon affe&ed with fuch a fquint s 
 as we have fuppoied, could be brought to the ha- 
 bit of looking ftraight^ his fight would thereby 
 be greatly hurt. For he would then fee every 
 thing double which he faw with both eyes at the 
 fame time, and diftant objects would appear to 
 be confounded together. His eyes are made for 
 fquinting,as much as .thofe of other men are made 
 for looking ftraight ; and his fight would be no 
 lefs injured by looking ftraight, than that of an- 
 other man by fquinting. He can never fee per- 
 fectly when he does not fquint, unlefs the corre- 
 fppnding points of his eyes mould by cuftom ■ 
 change their place ; but how fmall the probabi- 
 lity of this is, will appear in the i7thfection. 
 
 Thofe of the medical faculty who^ attempt the . 
 cure of a fquint, would do well to confider whe- 
 ther it is attended with fuch fymptoms as are • 
 above defcribed. If it is,, the cure would be worfe 
 than the malady : for every one will readily ac- 
 knowledge, that it is better to put up with the 
 Q^4 deformity 
 
243 Of the HUMAN MIND. Chap. VI. 
 deformity of a fquint, than to purchafe the cure 
 by the lofs of perfect: and diftinct vifion. 
 
 8. We fhall now return to Dr. Jurin's hypo- 
 thefis, and fuppofe, that our patient, when he 
 faw objects fingle notwithstanding his fquint, was 
 found, upon trial, to have feen them only with 
 one eye. 
 
 We would advife fuch a patient, to endeavour, 
 by repeated efforts, to leffen his fquint, and to 
 bring the axes of his eyes nearer to a parallel di- 
 rection. We have naturally the power of ma- 
 king fmall variations in the inclination of the op- 
 tic axes ; and this power may be greatly increa- 
 fed by exercife. 
 
 In the ordinary and natural ufe of our eyes, 
 we can direct: their axes to a fixed ftar ; in this 
 cafe they muft be parallel : we can direct them 
 alfo to an object fix inches diftant from the eye ; 
 and in this cafe the axes muft make an angle of 
 fifteen or twenty degrees. We fee young peo- 
 ple in their frolics learn to fquint, making their 
 eyes either converge or diverge, when they will, 
 to a very confiderable degree. Why fhould it be 
 more difficult for a fquinting perfon to learn to 
 look Straight when he pleafes ? If once, by an 
 effort of his will, he can but leffen his fquint, fre- 
 quent practice will make it eafy to leffen it, and 
 will daily increafe his power. So that if he be- 
 gins this practice in youth, and perfeveres in it, 
 he may probably, after fome time, learn to direct 
 both his eyes to one object. ' 
 
 When 
 
Seft. 15. Of SEEING. 249 
 
 When he hath acquired' this power, it will 
 be no difficult matter to determine, by proper 
 obfervations, whether the centres of -the retina;, 
 and other points fimilarly fituate with regard to 
 the centres, correfpond, as in other men.' 
 : 9. Let us now fuppofe that he finds, this to 
 be the cafe; and that he fees an object fingle 
 with both eyes,' when the axes of both are di- 
 rected to it. It will then concern him to ac- 
 quire the habit of looking ftraight, as he hath 
 got the power, becaufe he will thereby not only 
 remove a deformity, but improve his fight : and 
 I conceive this habit, like all others, may be 
 got by frequent exereife. He may practife be- 
 fore a mirror when alone, and in company he 
 ought to have thofe about him, who will obferve 
 and admonifh him when he fqiiints. 
 
 fo. What is fuppofed in the 9th article is 
 not merely imaginary-; it is really the cafe of 
 ibme fquinting perfons, as will appear in the 
 next fection. Therefore it ought further to be 
 inquired, How it comes to pafs, that fdeh a per- 
 fon fees an object which he looks at, only with 
 one eye, when both are open ? In order to an- 
 fwer this queftion, it may be obferved, firft, 
 Whether, when he looks at an object, the di- 
 verging eye is not drawn fo clofe to the nofe, 
 that it can have no diftindr. images ? Or, fecond- 
 ly, Whether the pupil of the diverging eye is 
 not covered wholly, or in part, by the upper 
 eye- lid ? Dr. Jurin obferved ■ inftances of thefe 
 cafes in perfons that fquinted, and affigns them 
 
 as 
 
250 OftheHUMAN MIND. Chap. VI. 
 as caufes of their feeing 1 the object only with 
 one eye. Thirdly, it may be obferved, Whether 
 the diverging eye is not fo directed, that the 
 picture of the object falls upon that part of the 
 retina where the optic nerve enters, and where 
 there is no vifion ? This will probably happen 
 in a fquint wherein the axes of the eyes con- 
 verge fo as to meet about fix inches before the 
 nofe. 
 
 ii. In the laft place, it ought to be inqui- 
 red, Whether fuch a perfon hath any diftinct vi- 
 fion at all with the diverging eye, at the time 
 he is looking at an object with the other ? 
 
 It may feem very improbable, that he fhould 
 be able to read with the diverging eye when the 
 other is covered, and yet, when both are open,, 
 have no diftinct vifion with it at all. But this 
 perhaps will not appear fo improbable, if the 
 following confiderations are duly attended to. 
 
 Let us fuppofe that one who faw perfectly, 
 gets, by a blow on the head, or fome other ac- 
 cident, a permanent and involuntary fquint. 
 According to the laws of vifion, he will fee 
 objects double, and will fee diftant objects con- 
 founded together : but fuch vifion being very 
 difagreeable, as well as inconvenient, he will do 
 every thing in his power to remedy it. For al- 
 leviating fuch diftrelTes, nature often teaches 
 men wonderful expedients, which the fagacity 
 of a philofopher would be unable to difcover. 
 Every accidental motion, every direction or 
 conformation of his eyes, which lefiehs the 
 
 evil, 
 
Sect. 15. Of SEEING. 251 
 
 evil, will be agreeable ; it will be repeated, un- 
 til it be learned to perfection, and become ha- 
 bitual, even without thought or defign. I\ow, 
 in this cafe, what difturbs the fight of one eye, 
 is the fight of the other ; and all the difagreeabie 
 appearances in vifion would ceafe, if the light 
 of one eye was extinct : The fight of one eye 
 will become more diftinct and more agreeable, 
 in the fame proportion as that of the other be- 
 comes faint and indiftinct. It may therefore 
 be expected, that every habit will, by degrees, 
 be acquired, which tends to deftroy diftinct 
 vifion in one eye, while it is preferved in the 
 •other. Thefe habits will be greatly facilitated, 
 if one eye was at fi'rft better than the other; 
 for in that cafe the belt eye will always be di- 
 rected to the object which he intends to look 
 at, and every habit will be acquired which tends 
 to hinder his feeing it at all, or feeing it diftindt- 
 ly by the other at the fame time. 
 
 I fhall mention one or two habits that may 
 probably be' acquired in fuch a cafe; perhaps 
 there are others which we cannot fo eafily con- 
 jecture. Firft, By a fmall increafe or diminu- 
 tion of his fquint, he may bring it to correfpond 
 with one or other of the cafes mentioned in the 
 laft article. Secondly, The diverging eye may 
 be brought to fuch a conformation as to be ex- 
 tremely fhort-fighted, and confequently to have 
 no diftincSt vifion of objedts at a diftance. I 
 Jcnew this to be the cafe of one perfon that 
 fquinted; but cannot fay whether the Ihort- 
 fighted- 
 
252 Of the HUMAN MIND. Chap. VI. 
 
 iightednefs of the diverging eye was original, or 
 acquired by habit. 
 
 We fee, therefore, that one who fquints, and 
 originally faw objects double by reafon of that 
 fquint, may acquire fuch habits, that when he 
 looks at an object, he fhall fee it only with one 
 eye : nay, he may acquire fuch habits, that 
 ■when he looks at an object with his beft eye, he 
 fhall have no diftinct vifion with the other at all. 
 "Whether this is really the cafe, being unable to 
 determine in the inftances that have fallen under 
 my obfervauon, I fhall leave to future inquiry. 
 
 I have endeavoured, in the foregoing articles, 
 to delineate fuch a procefs as is proper in ob- 
 ferving the phenomena of fquinting. I know 
 well by experience, that this procefs appears 
 more eafy in theory, than it will be found to 
 be in practice ; and that in order to carry it on 
 •with fuccefs, fome qualifications of mind are 
 neceffary in the patient, which are not always 
 to be met with. But if thofe who have pro- 
 per opportunities, and inclination, to obferve 
 fuch phenomena, attend duly to this procefs, 
 they may be able to furnifh facts lefs vague and 
 uninftructive than thofe we meet with, even in 
 authors of reputation. By fuch facts, vain theo- 
 ries may be exploded, and our knowledge of the 
 laws of nature which regard the nobleft of our 
 fenfes, enlarged. 
 
 S EC T. 
 
Seft. 16. Of S E E I N G. 253 
 
 SECT. XVI. 
 
 Fafis relating to fquinting: 
 
 < 
 TLIAving confidered the phenomena of fquint- 
 ing hypothetically, and their connection 
 with correfponding points in the retina ; I (hall 
 now mention the facts I have had occafion to ob-' 
 ferve myfelf, or have met with in authors, that 
 can give any light to this fubject. 
 
 Having examined above twenty peffons that 
 fquinted, I found in all of them a defect in the 
 fight of one eye. Four only had fo much of 
 diftinct virion in the weak eye, as to be able to 
 read with it, when the other was covered. The 
 reft faw nothing at all diftinctly with one eye. 
 
 Dr. Porterfield fays, that this is generally the 
 cafe of people that fquint : and I fufpect it is fo 
 more generally than is commonly imagined. Dr. 
 Jurin, in a very judicious diflertation upon fquint- 
 ing, printed in Dr. Smith's Optics, obferves, that 
 thofe who fquint, and fee with both eyes, ne- 
 ver fee the. fame object with both at the fame 
 time; that when one eye is directed ftraight 
 forward to an object, the other is drawn fo 
 clofe to the nofe, that the object cannot at all 
 be feen by it, the images being too oblique and 
 too indiftinct to affect the eye. In fome fquint- 
 ing perfons, he obferved the diverging eye drawn 
 under the upper eye-lid while the other was 
 directed to the object. From thefe obfervations 
 5 he 
 
4 54 Of the HUMAN MIND. Chap. VI. 
 he concludes, that " the eye is thus diftorted, 
 " not for the fake of feeing better with it, but 
 " rather to avoid feeing at all with it as much 
 " as poflible." From all the obfervations he 
 had made, he was fatisfied that there is nothing 
 peculiar in the ftructure of a fquinting eye ; 
 that the fault is only in its wrong direction •, and 
 that this wrong direction is got by habit. There- 
 fore he propofes that method of cure which we 
 have defcribed in the 8th and 9th articles of the 
 laft fection. He tells us, that he had attempted 
 a cure after this method, upon a young Gen- 
 tleman, with promifing hopes of fuccefs ; but 
 was interrupted by his falling ill of the fmall-pox, 
 of which he died. 
 
 It were to be wifhed that Dr. Jurin had ac- 
 quainted us, whether he ever brought the young 
 man to direct the axes of both eyes to the fame 
 object, and whether, in that cafe, .he faw the 
 object fingle, and faw it with both eyes ; and 
 that he had likevvife acquinted us, whether he 
 faw objects double when his fquint was diminilh- 
 ed. But as to thefe facts he is filent. 
 
 I wifhed long for an opportunity of trying 
 Dr. Jurin's method of curing a fquint, without 
 finding one ; having always, upon examination, 
 difcovered fo great a defect in the fight of one 
 eye of the patient as difcouraged the attempt. 
 
 But I have lately found three young Gentle- 
 men, with whom I am hopeful this method 
 may have fuccefs, if they have patience and 
 perfeverance in ufing it. Two of them are 
 
 brothers, 
 
Seft. 16. Of S E E I N G. 255 
 
 brothers T and, before I had accefs to examine 
 them, had been practifing this method by the 
 direction of their tutor, with fuch fuccefs, that 
 the elder looks ftraight when he is upon his 
 guard : the younger can direct both his eyes to 
 one object; but they foon return to their ufual 
 fquint. 
 
 A third young Gentleman, who had never 
 heard of this method before, by a few days 
 practice, was able to direct both his eyes to 
 one object, bur could not keep them long in 
 that direction. All the three agree in this, 
 that when both eyes are directed to one object, 
 they fee it and the adjacent objects fingle; but 
 when they fquint, they fee objects fometimes 
 fingle and fometimes double. I obferved of all 
 the three, that when they fquinted moft, that 
 is, in the way they had been accuftomed to, 
 the axes of their eyes converged fo as to meet 
 five or fix inches before the nofe. It is pro- 
 bable that in this cafe the picture of the object 
 in the diverging eye, mull fall upon that part 
 of the retina where the optic nerve enters ; and 
 therefore the object could not be {een by that 
 eye. 
 
 All the three have fome defect in the fight 
 of one eye, which none of them knew until I 
 put them upon making trials ; and when they 
 fquint, the beft eye is always directed to the 
 object, and the weak eye is that which di- 
 verges from it. But when the beft eye is co- 
 . vered, the weak eye is turned directly to the 
 1 object. 
 
2 5 6 Of the HUMAN MIND. Chap. VI. 
 object. Whether this defect of fight in one 
 eye, be the effect of its having been long dif- 
 ufed, as. it muft have been when they fquinted ; 
 or whether fome original defect in one eye 
 might be the occafion of their fquinting, time 
 may difcover. The two brothers have found 
 the fight of the weak eye improved by ufing to 
 read with it while the other is covered. The 
 elder can read an ordinary print with the weak 
 eye ; the other, as well as the third Gentleman, 
 can only read a large print with the weak eye. 
 I have met with one other perfon only who 
 fquinted, and yet could read a large print with 
 the weak eye. He is a young man, whofe eyes 
 are both tender and weak-fighted, but the left 
 much weaker than the right. When he looks 
 at any object, he always directs the right eye 
 to it, and then the left is turned towards the 
 nofe fo much, that it is impoflible for him to fee 
 the fame object with both eyes at the fame time. 
 When the right eye is covered, he turns the 
 left directly to the object ; but he fees it indi- 
 ftinctly, and as if it had a mift about it. 
 
 I made feveral experiments, fome of them in 
 the company and with the afiiftance of an in- 
 genious phyfician, in order to difcover, whether 
 objects that were in the axes of the two eyes, 
 were feen in one place confounded together, as 
 in thofe" who have no involuntary fquint. The 
 object placed in the axis of the weak eye was 
 a lighted candle, at the diftance of eight or ten 
 feet. Before the other eye we placed a -printed 
 
 book, 
 
Seft. 16. Of SEEING. 257 
 
 book, at fuch a diftance as that he could read 
 upon it. He faid, that while he read upon the 
 book, he faw the candle but very faintly. And 
 from what we could learn, thefe two objects 
 did not appear in one place, but had all that an- 
 gular diftance in appearance which they had in 
 reality. 
 
 If this was really the cafe, the conclufion to 
 be drawn from it is, that the correfponding 
 points in his eyes are not fituate in the fame 
 manner as in other men j and that if he could 
 be brought to direct both eyes to one object, he 
 Would fee it double. But confidering that the 
 young man had never been accuftomed to ob- 
 servations of this kind, and that the fight of 
 one eye was fo imperfect, I do not pretend to 
 draw this conclufion with certainty from this 
 fingle inftance. 
 
 All that can be inferred from thefe facts is, 
 that of four perfons who fquint, three appear 
 to have nothing preternatural in the ftructure of 
 their eyes. The centres of their retina, and 
 the points fimilarly fituate with regard to the 
 centres, do certainly correfpond in the fame 
 manner as in other men. So that if they can 
 be brought to the habit of directing their eyes 
 .right to an object, they will not only remove a 
 deformity, but improve their fight. With re- 
 gard to the fourth, the cafe is dubious, with 
 ibme probability of a deviation from the ufual 
 courfe of nature in the fituation of the corre- 
 fponding points of his eyes. 
 
 R SECT. 
 
258 Of the HUMAN MIND. Gh.ap.VL 
 
 SECT. XVII. 
 
 Of the effeS of etiftofyi' in feeing objsfls fingle: 
 
 T T appears from the phenomena of fiogle and 
 double vifion, recited in Sect. 13. that our 
 feeing an object fmgle with two eyes, depends 
 upon thefe two things. Firft, Upon that mu- 
 tual correfpondenee of certain. points of the re- 
 titta which we have often defcribed. Secondly, 
 "Upon the two eyes being directed to the object 
 fo accurately, that the two images of it fall upon* 
 correfponding . points. Thefe, ■ two t things- mud 
 concur in order to our feeing an object * •fingle 
 • with two eyes ; and as far as they depend upon 
 cuftom, fo far only can fingle vifion depend upon 
 cuftom. 
 
 With- regard to the fecondy that is, the ac- 
 curate diredion of both, eyes to the object, 1 1 
 think it muft be acknowledged that this is only 
 learned by cuftom. Nature hath wifely or- 
 dained the eyes to move in fuch manner, that 
 their axes fhall always be nearly parallel ; but 
 hath left it in our power to vary their inclina- 
 tion a little, according to the diftance Of the 
 object we look at. Without this power, ob- 
 jects would appear fingle at one particular di- 
 ftance only; and, at diftances mu'chlefs, or much 
 greater, would always appear double. The 
 wifdom of nature is confpicuous in giving us this 
 power, and no lefs confpicuous in making the 
 extent of it exactly adequate to the end. 
 
 3 The 
 
■Sect. i 7 . b£ SEEING'. ly 
 
 The parallelifm of the eyes, in general, is 
 therefore the work of nature; but that preciife 
 and accurate direction, which muft be varied ac- 
 cording to the diftance of the object, is the ef- 
 
 .fect of cuftom; The power which nature hath 
 
 j left us of varying the inclination of the optic 
 axes a little* is turned into a habit of giving 
 them always that inclination which is adapted to 
 
 ..the diftance of the object. 
 
 ( But it may be aiked, What gives rife to this 
 
 . habit ? The only anfwer that can be given to 
 
 .this queftipn is, that it is found necefiary to 
 perfect and diftinct vifion. A man who, hath 
 loft the fight of one eye, very often lofes the 
 habit of directing it exactly to the object he 
 looks at, becaufe that habit is no longer of ufe 
 to him. And if he Ihould recover the fight of 
 his eye, he would recover this habit, by finding 
 it ufefuh ,No part of the human constitution is 
 more admirable than that whereby we acquire 
 habits which are found ufeful, without any def 
 fign or intention. Children muft fee imper- 
 fectly at firft ; but, by ufing their eyes, they 
 learn to ufe them in the beft manner, and ac- 
 quire,, without intending it, the habits necef- 
 fary for that pufpofe. Every man becomes moft 
 expert in that kind of vifion which is moft ufe- 
 ful to him in his particular profeflion and manner 
 of life* A miniature painter, or an engraver* 
 
 ^ fees very near obje&s better than afailor; but 
 
 the failor fees very diftant objects much better 
 
 than they, A perfon that is fhort-fighted, irt 
 
 R ?. looking 
 
i6o Of the HUMAN MIND. Chap. VI. 
 
 looking at diftant objects, gets the habit of con- 
 tracting the aperture of his eyes, by-almoft 
 clofing his eye-lids. Why ? For no other rea- 
 fon, but becaufe this makes him fee the object 
 more diftinct. In like manner, the reafon why 
 every man acquires the habit of directing both 
 eyes accurately to the object, muft be, becaufe 
 thereby he fees it more perfectly and diftinctly. 
 
 It remains to be confidered, whether that cor- 
 refpondence between certain points of the retina, 
 which is likewife neceffary to fingle vifion, Jbe 
 the effect of cuftom, or an original property of 
 human eyes. 
 
 A ftrong argument for its being an original 
 property, may be drawn from the habit juft 
 now mentioned of directing the eyes accurately 
 to an object. This habit is got by our finding 
 it neceffary to perfect and diftinct vifion. But 
 why is it neceffary ? For no other reafon but 
 this, becaufe thereby the two images of the ob- 
 ject falling upon correfponding points, the eyes 
 afiift each other in vifion, and the objecT: is feen 
 better by both together, than it could be by 
 one ; but when the eyes are not accurately di- 
 rected, the two images of an object fall upon 
 points that do not correfpond, whereby the fight 
 of one eye difturbs the fight of the other, and 
 the object is feen more indiftinctly with both 
 eyes than it would be with one. Whence it is 
 reafonable to conclude, that this correfpondence 
 of certain points of the retina, is prior to the 
 
 habits 
 
Seft. 17- Of SEEING. 261 
 
 habits we acquire in vifion, and confequently is 
 natural and original. We have all acquired the 
 habit of directing our eyes always in a particu- 
 lar manner, which caufes fingle vifion. Now, 
 if nature hath ordained that we fhould have fingle 
 vifion only, when our eyes are thus directed, 
 there is an obvious reafon why all mankind 
 fhould agree in the habit of directing them in 
 this manner. But if fingle vifion is the effect 
 of cuftom, any other habit of directing the eyes 
 would have anfwered the purpofe ; and no ac- 
 count can be given why this particular habit 
 ftiould be fo univerfal ; and it muft appear very 
 ftrange, that no one inftance hath been found of, 
 a perfon who had acquired the habit of feeing 
 objects fingle with both eyes, while they were 
 directed'in any other manner. 
 
 The judicious Dr. Smith, in his excellent 
 fyftem of optics, maintains the contrary opinion, 
 and offers fome reafonings and facts in proof of 
 it. He agrees with Bifhop Berkeley in attribu- 
 ting it entirely to cuftom, that we fee objects 
 fingle with two eyes, as well as that we fee ob- 
 jects erect by inverted images. Having confi- 
 dered Bifhop Berkeley's reafonings in the nth 
 fection, we fhall now beg leave to make fome re- 
 marks on what Dr. Smith hath faid upon this 
 fubject, with the refpedt due to an author to whom 
 the world owes, not only many valuable difco- 
 veries of his own, but thofe.of the boghtefl: 
 mathematical genius of this age, which, with 
 R 3 great 
 
262 OftheHUMAN MIND. Chap. VI. 
 
 great labour, he generbufly redeemed from o'bli-. 
 vion, 
 
 He obferves, that the qiieftion, "Why we fee 
 objects fingle with two eyes ? is of the fame fort 
 with this, Why we hear founds fingle with two 
 ears ? and that the fame anfwer muft ferve both. 
 The inference intended to be drawn from this ob- 
 fervation is, that as the fecond of thefe pheno- 
 mena is the effect of cuftom, fo likewife is the 
 firft. 
 
 Now I humbly conceive that the queftions are 
 not fo much of the fame fort, that the fame an- 
 fwer muft ferve for both; and moreover, that 
 our hearing fingle with two, ears, is not the ef- 
 fect of cuftom. 
 
 Two or more vifible objects s altho' perfectly 
 fimilar, and feen at the very fame time, may be 
 diftinguifhed by their vifible places •, but two 
 founds perfectly fimilar, and heard at the fame 
 time, cannot be diftinguifhed ; for from the na- 
 ture of found, the fenfations theyoccafion muftco- 
 alefce into one, and lofe all diftinfHon. If there- 
 fore it is afked, Why we hear founds fingle with 
 two ears ? I anfwer, Not from cuftom ; but be- 
 caufe two founds which are perfectly like and 
 fynchronous, have nothing by which they can be 
 diftinsiuifhed. But will this anfwer fit the other 
 queftion ? I think not. 
 
 The object makes an appearance to each eye, 
 as the found makes an impreffion upon each ear; 
 fo far the two fenfes agree. But the vifible ap- 
 pearances may be diftinguifhed by place, when 
 
 perfectly 
 
Sect. 17. Of SEEING. 263. 
 
 perfectly like in other refpects; the founds can- 
 not be thus diftinguiftied •, and herein the two 
 fjenfes differ. Indeed, if the two appearances 
 have the fame vifibie place, they are, in that 
 cafe, as incapable of diftin&ion as the founds 
 were, and we fee the object fingle. But when 
 they have not the farhe viuble place, they are 
 perfectly diftinguifhable, and we fee the object 
 double. We fee the object fingle only, when 
 the eyes are dire&ed in one particular manner -, 
 while there are many other ways of directing 
 them within the fphere of our power, by which 
 we fee the object double. 
 
 Dr. Smith juftly attributes to cuftom that 
 well-known fallacy in feeling, whereby a button 
 prefied with two oppofite fides of two con- 
 tiguous fingers laid acrofs, is felt double. I 
 agree with him, that the caufe of this appearance 
 is, that thofe oppofite fides of the fingers have 
 never been ufed to feel the fame object, but two 
 different objects, at the fame time. And I beg 
 leave to add, that as cuftom produces this phe- 
 nomenon, fo a contrary cuftom deftroys it : for 
 if a man frequently accuftoms himfelf to feel the 
 button with his fingers acrofs, it will at laft be 
 felt fingle ; as I have found by experience. 
 
 It may be taken for a general rule, That 
 things which are produced by cuftom, may be un- 
 done or changed by difufe, or by a contrary 
 cuftom. On the other hand, it is a ftrong ar- 
 gument, that an effect is not owing to cuftom, 
 but to the conftitution of nature, when a con- 
 R 4 ' trary 
 
264 Of the HUMAN MIND. Chap. VI. 
 trary cuftom, long continued, is found neither 
 to change nor weaken it. I take this to be the 
 beft rule by which we can determine the queftion 
 prefently under confideration. I (hall therefore 
 mention two facts brought by Dr. Smith, to prove 
 that the correfponding points of the retina have 
 been changed by cuftom -, and then I mail mention 
 fome facts tending to prove, that there are cor- 
 refponding points of the retina of the eyes origi- 
 nally, andthatcuftomproduces no change in them. 
 
 " One fact is related upon the authority of 
 *' Martin Folkes, Efq; who was informed by 
 " Dr. Hepburn of Lynn, that the Reverend 
 " Mr. Fofter of Clinchwharton, in that neigh- 
 " bourhood, having been blind for fome years of 
 " a gutta ferena, was reftored to fight by faliva- 
 " tion : and that upon his firft beginning to fee, 
 *' all objects appeared to him double ; but after- 
 " wards the two appearances approaching by 
 " degrees, he came at laft to fee fingle, and as 
 tt diftinctly as he did before he was blind." 
 
 Upon this cafe I obferve, firft, That it does 
 not prove any change of the correfponding points 
 of the eyes, unlefs we fuppofe, what is not affirm- 
 ed, that Mr. Fofter directed his eyes to the ob- 
 ject at firft, when he faw double, with the fame 
 accuracy, and in the fame manner, that he did 
 afterwards when he faw fingle. 2dly, If we 
 fhould fuppofe this, no account can be given, 
 why at firft the two appearances mould be feen 
 at one certain angular diftance rather than ano- 
 ther; or why this angular diftance fhould gra- 
 dually 
 
Sea. if. Of SEEING. 265 
 
 dually decreafe, until at laft the appearances 
 coincided. How could this effect be produced 
 by cuftom ? But, thirdly, Every circumftance of 
 this cafe may be accounted for on the fuppofiti- 
 on that Mr. Fofter had correfponding points in 
 the retina of his eyes from the time he began to 
 fee, and that cuftom made no change with re- 
 gard to them. We need only further fuppofej 
 what is common in fuch cafes, that by fome 
 years blindnefs he had loft the habit of directing 
 his eyes accurately to an object, and that he gra- 
 dually recovered this habit when he came to iee. 
 
 The fecond fact mentioned by Dr. Smith, is 
 taken from Mr. Chefelden's anatomy; * and is 
 this. " A gentleman who, from a blow on the 
 «' head, had one eye diftorted, found every 
 ** object appear double ; but by degrees the moft 
 *' familiar ones became fingle ; and in time all 
 «' objects became fo, without any amendment 
 ** of the diftortion." 
 
 I obferve here, that it is not faid that the 
 two appearances gradually approached, and at 
 laft united, without any amendment of the 
 diftortion. This would indeed have been a de- 
 cifive proof of a change in the correfponding 
 points of the retina ; and yet of fuch a change 
 as could not be accounted for from cuftom. But 
 this is not faid ; and if it had been obferved, a 
 circumftance fo remarkable would have been 
 mentioned by Mr. Chefelden, as it was in the 
 other cafe by Dr. Hepburn. We may therefore 
 take it for granted, that one of the appearances 
 
 vanifhed 
 
*6& OftheH-UMrAN MWD. Chap. VI. 
 vanished by degrees,, without approaching to, the 
 other* And thisr I. conceive might happen fe- 
 deral ways. Firft, The fight of the diftorted 
 eye might gradually decay, by. the hurt : fo the 
 appearances prefented by that eye would gra- 
 dually vanim. Secondly, A fmall and unper- 
 ceived change in the manner of directing the 
 cyesy might oceafion his- not feeing the object 
 with the diftorted eye, as appears from Sect. 15. 
 Art. 10. Thirdly, By acquiring the habit of 
 directing, one and the fame eye always to the ob- 
 ject, the faint and oblique appearance, prefented 
 by the other eye, might be fo little attended to 
 when it became familiar, as not to-be perceived.. 
 One of thefe caufes, or more of them concur- 
 ring,- might produce the effect mentioned-, with- 
 out any change of the correfponding points of 
 the eyes. 
 
 For thefe reafons, the facts mentioned by Dr. 
 Smith, altho* curious, feem not to be decisive. 
 
 The following facts ought to be put in the 
 oppofite fcale. Firft, In the famous cafe of the 
 young gentleman couched by Mr, Chefelden after 
 having had cataracts on both eyes until he was 
 thirteen years of age, it appears, that he faw 
 objects fingle from the time he began to fee with 
 both eyes. Mr. Chefelden's words are, " And 
 *' now being lately couched of his other eye, he 
 ** fays, that objects at firft appeared large to 
 " this eye, but not fo large as they did at firft 
 " to the other ; and looking upon the fame ob- 
 11 jeer, with both eyes, he thought it looked 
 
 «' abouis 
 
a*a. 17. Of SEEING. %4f 
 
 u about twice as large as with the firft couched 
 " eye only, But riot 1 double, that we cah any? 
 « w'ays difcdve'r." 
 
 Secdridly, The 1 three young gentlemen men- 
 tioned in the lalt feciion, who. had fquinted, as 
 far as I know, ffbrn infancy ; as foon as they* 
 learned to direct both eyes to an object, faw it 
 fingle. In thefe four cafes, it appears evident,* 
 that the centres of the retina correfponded origi- 
 nally, and before cuftom could produce any fuch 
 effect: for Mr. Ch£felderi' s yourig.gentleman had 
 never been accuftomed to fee at all before he 
 was couched ; arid the other three had neveV 
 been accuftomed to direct the axes of both eyes 
 to the object. 
 
 Thirdly, From the facts recited in Sect. 13}. 
 it appears, That from the time we are capable 
 of obierving the phenomena of fingle arid double 
 vifion, cuftom makes no change in thetn. 
 
 I have amufed myfelf with fuch obfervations 
 for more than thirty years ; and in every cafe 
 wherein I faw the object double at firft, I fee it 
 fo to this day, notwithftanding the conftant' ex- 
 perience of its being fingle, In other cafes where 
 I know there are two objects, there appears only 
 pne, after thoufarids of experiments. 
 
 Let a man look at a familiar object thrQUgfi" a 
 polyhedron or rriultiplyirig-glafs every hour of 
 his life, the number of vifibleappearances will be 
 the fame at laft as at firft : nor does any number 
 of experiments, or length of time, make the leaft 
 Change. 
 
 Effects 
 
*68 Of the HUMAN MIND. Chap. VI. 
 
 Effects produced by habit, muft vary accord- 
 ing as the acts by which the habit is acquired are 
 more or lefs frequent ; but the phenomena of 
 jingle and double vifion are fo invariable and 
 uniform in all men, are fo exactly regulated by 
 mathematical rules, that I think, we have good 
 reafon to conclude, that they are not the effect 
 of cuftom, but of fixed and immutable laws of 
 nature. 
 
 SECT. XVIII. 
 
 Of Dr. Porterjiel&s account of Jmgle and double 
 vifion. 
 
 TJIshop Berkeley and Dr. Smith feem to attri- 
 bute too much to cuftom in vifion, Dr. Por- 
 terfield too little. 
 
 This ingenious writer thinks, that, by an ori- 
 ginal law of our nature, antecedent to cuftom and 
 experience, we perceive vifible objects in their 
 true place, not only as to their direction, but 
 likewife as to their diftance from the eye : and 
 therefore he accounts for our feeing objects An- 
 gle, with two eyes, in this manner. Having the 
 faculty of perceiving the object with each eye in 
 its true place, we muft perceive it with both 
 eyes in the fame place •, and confequently muft 
 perceive it fingle. 
 
 He is aware, that this principle, altho' it ac- 
 counts for our feeing objects fingle with two eyes, 
 yet docs not at all account for our feeing objects 
 
 double : 
 
Sea. 18. Of SEEING. 2% 
 
 double : and whereas other writers on this fub- 
 ject take it to be a fufficient caufe for double vi- 
 fion that we have two eyes, and only find it dif-, 
 ficuk to affign a caufe for fingle vifion •, on the 
 contrary, Dr. Porterfield's principle throws all 
 the difficulty on the other fide. 
 
 Therefore, in order to account for the phse-" 
 nomena of double vifion, he advances another 
 principle, without fignifying whether he con- 
 ceives it to be an original law of our nature, or 
 the effect of cuftom. It is, That our natural per- 
 ception of the diftance of objects from the eye, 
 is not extended to all the objects that fall within 
 the field of vifion, but limited to that which we 
 directly look at ; and that the circumjacent ob- 
 jects, whatever be their real diftance, are fcen at 
 the fame diftance with the object we look at; as 
 if they were all in the furface of a fphere where- 
 of the eye is the centre. 
 
 Thus, fingle vifion is accounted for by our fee- 
 ing the true diftance of an object which we look 
 at ; and double vifion, by a falfe appearance of 
 diftance in objects which we do not directly look 
 at. 
 
 We agree with this learned and ingenious au- 
 thor, that it is by a natural and original princi- 
 ple that we fee vifible objects in a certain direc- 
 tion from the eye, and honour him as the author 
 , of this difcovery : but we cannot afient to either 
 of thofe principles by which he explains fingle 
 and double vifion, for the following reafons. 
 
 f 1. Our 
 
&jo OfthcHUiM-ANfMIND. Chap ■ VI. 
 i. 'Our having a natural and original percep- 
 tion of the diftance of objects, from the. eye, . ap- 
 pears contrary to a well-attefted : fact : for the 
 
 'young gentleman couched -by , Mr. Chefelden, 
 
 'imagined at firft, that whatever-he; faw„ touched 
 his eye, as what he felt, touched his: hand. 
 
 2. The perception we have .of the diftance of 
 objects from the eye, whether.it be from. nature 
 or cuftom, is -not fo accurate. and determinate as 
 is neceffaryto produce fingle vifion. A miflake 
 of the twentieth, or. thirtieth part of the diftance 
 
 . of a fmall object,- fuch as a pin, ought, according 
 to Dr. Porterfield's hypothefis, to make it appear 
 double. Very few can judge of the diftance of a 
 vifible object .with fuch accuracy. . Yet we never 
 
 j; find double vifion- produced by miftaking the di- 
 
 "ftance of the object. 'There are many cafes in vi- 
 fion, even .with the naked eye, wherein we mif- 
 take the diftance of an objeft by one half or 
 -more : ^why-do we fee fuehobjects fingle ? When 
 
 •'I move my fpectacles, from. my eyes toward; a 
 -fmall object, two or three feet diftant, the ob- 
 ject Teems to- approach,., fo as to be feen at laft at 
 about half its real diftance ; but it is feen fingle 
 at that apparent diftance, as well as when we fee 
 it with the naked eye at its real diftance. And 
 when we look at an object with a binocular re- 
 
 ■ lefcope, properly fitted to the eyes, we fee it fin- 
 gle, while it appears fifteen or twenty times near- 
 er than it is. There are then- few cafes wherein 
 the diftance of an object from the eye is feen fa 
 accurately as is necefiary for fingle vifion, upon 
 
 this 
 
5e&.ji8. Of SEE'IN^G. -2.7*1 
 
 this hypothecs : This feeps ro * be a cowcUafive 
 ar.CTumanttagairrfl'thejaccouritgivfrKSfiififlgie.vi- 
 fion. 'We find iikw/bk, -that fatfe judgments or 
 ''fallacious appearances of the diftanee-4>f an ob- 
 ;je£t, do not proekie© 'double vifion. This feems 
 •to beta> conclu-five 'alignment 'againit the account 
 
 • given- of x3©#ble vifion. 
 
 3. The perception -we'-have- of 5 the 1 linear di- 
 
 • fiance of -objects, 'feems to- be -wholly the effect 
 - of experience. This : I think' hath been proved 
 l byi BimoptJBeFkekyand,by Dr. Smith ; ami when 
 
 ■we come to point out she-rneans ©f judging of 
 ^d-iftance <byiiight, dt -will appear that they are all 
 : furoifhed! by experience. 
 
 •4. ' Supposing- that fey a law of our nature, the 
 ^Iftance of- objects' from- the eye were perceived 
 ■ motbaccurately, a& well-as their direotion, it will 
 -not- follow 'that we muft fee the object- Tingle. 
 Let us eonfldermvhat? means fuch a law of nature 
 •would furnnlifor refblving the queftion, Whe- 
 ther the objects of the two eyes are in one and 
 the' fame place, and confeqnently are not two, 
 but one? 
 
 Suppofe then two right lines, one drawn from 
 the centre of one eye to--its -object, the other 
 drawn, in like-manner, from the centre of the 
 other eye to its object. This law of nature gives 
 us the direction or pofitionof each of : thefe right 
 lines, and 1 the length of each ;- and -this is all thai; 
 it gives. Thefe are geometrical data, and we 
 may learn from geometry what is determined by 
 their means. Is it then determined by thefe data, 
 
 Whether 
 
2 7 2 Of the H U M A N M I N D. Chap* VI. 
 
 Whether 'the two right lines terminate in one 
 and the fame point, or not ? No truly. In order 
 to determine this, we muft have three other da- 
 ta. We muft know whether the two right lines 
 are in one plane: we muft know what angle 
 they make ; and we muft know the diftance be- 
 tween the centres of the eyes. And when thefe 
 things are known, we muft apply the rules of 
 trigonometry, before we can refolve the que- 
 ftion, Whether the objects of the two eyes are 
 in one and the fame place v and confequently 
 whether they are two or one ? 
 
 5. That falfe appearance of diftance into 
 •which double vifion is refolved, cannot be the 
 effect of cuftom ; for conftant experience con- 
 tradicts it : Neither hath it the features of a law 
 of nature; becaufe it does not anfwerany good 
 purpofe, nor indeed any purpofe at all but to de- 
 ceive us. But why mould we feek for argu- 
 ments, in a queftion concerning what appears 
 to us, or does not appear ? The queftion is, At 
 what diftance do the objefts now in my eye 
 appear ? Do they all appear at one diftance, as 
 if placed in the concave furface of a fphere, the 
 eye being in the centre ? Every man furely may 
 know this with certainty ; and, if he will but 
 give attention to the teftimony of his eyes, needs 
 not afk a philofopher, how vifible objects ap~ 
 pear to him. Now, it is very true, that if I 
 look up to a ftar in the heavens, the other ftars 
 that appear at the fame time, da appear in this 
 manner: Yet this phenomenon does not favour 
 
 Dr. 
 
Sect. 18. Of S E E I N G. 273 
 
 Dr. Porterfield's hypothefis ; for the ftars and 
 heavenly bodies, do not appear at their true di- 
 ftances when we look directly to them, any more 
 than when they are feeri obliquely : and if this 
 phenomenon be an argument for Dr. Porter- 
 field's fecond principle, itmuft deftroy the firft. 
 
 The true caufe of this phsenomenon will be 
 given afterwards; therefore fetting it afide for 
 the prefent, let us put another cafe. I fit in 
 my room, and direct my eyes to the door, which 
 appears- to be about fixteen feet diftant: at the 
 fame time I fee many other objects faintly and 
 obliquely -, the floor, floor-cloth, the table which 
 I write upon, papers, ftandifh, candle, i£c. 
 Now, do all thefe obje&s appear at the fame 
 diftance'of fixteen feet ? Upon the clofeft atten- 
 tion, I find they do not. 
 
 SECT. XIX. 
 
 Of Dr. Briggs's theory, and Sir Ifaac Newton's 
 conjecture on this JiibjeM. 
 
 T Am afraid the reader, as well as the writer, 
 is already tired of the fubject of fingle and 
 double vifion. The multitude of theories ad- 
 vanced by authors of great name, and the mul- 
 titude of facts, obferved without fufficient fluU 
 in optics, or related without attention' to the. 
 moft material and decifive circumftances, have 
 equally contributed to perplex it. 
 
 S in 
 
274 Of the HUMAN MIND. Chap. VI. 
 
 In order to bring it to fome ifiue, I have, in 
 the 13th fedtion, given a more full and regular 
 deduction than had been given heretofore, of 
 the phenomena of fingle and double vifion, in 
 thofe whofe fight- is perfect; and have traced 
 them up to one general principle, which appears 
 to be a law of vifion in human eyes that are per- 
 fect and in their natural ftate. 
 
 In the 14th fedtion I have made rt appear, 
 that this law of vifion, altho' excellently adapt- 
 ed to the fabric of human eyes, cannot anfwer 
 the purpofes of vifion in fome other animals ; 
 and therefore, very probably, is not common to 
 all animals. The purpofe of the 15th and 16th 
 fections is, to inquire, whether there be any 
 deviation from this law of vifion in thofe who 
 fquint ? a queftion which is of real importance 
 in the medical art, as well as in the philofophy 
 of vifion ; but which, after all that hath been 
 obferved and written on the fubject, feems not 
 to be ripe for a determination, for want of pro- 
 per obfervations. Thofe who have had fkitt 
 to make proper obfervations, have wanted op- 
 portunities ; and thofe who have had opportu- 
 nities, have wanted fkill or attention. I have 
 therefore thought it worth while to give a diP- 
 tin£t account of the obfervations necefiary for 
 the determination of this queftion, and what 
 conclufions may be drawn from the facts ob- 
 ferved. I have likewife collected, and fet in 
 one view, the moft conclufive facts that have 
 
 occurred 
 
Seft. i 9 . Of S E E I N G. 275 
 
 occurred in authors, or have fallen under my 
 own obfervation. 
 
 It muft be confefied that thefe facts, when 
 applied to the queftion in hand, make a very- 
 poor figure •, and the Gentlemen of the medical 
 faculty are called upon, for the honour of their 
 profeflion, and for the benefit of mankind, to 
 add to them. 
 
 All the medical, and all the optical writers, 
 upon the ftrabifmus, that I have met with, ex- 
 cept Dr. Jurin, either affirm, or take it for 
 granted, that fquinting perfons fee the object 
 with both eyes, and yet fee it fingle. Dr. Jurin 
 affirms, that fquinting perfons never fee the ob- 
 ject with both eyes ; and that if they did, they 
 would fee it double. If the common opinion be 
 true, the cure of a fquint would be as pernici- 
 ous to the fight of the patient, as the caufing of 
 a permanent fquint would be to one who na- 
 turally had no fquint : and therefore no phyfi- 
 ci.an ought to attempt fuch a cure ; no patient 
 ought to fubmit to it.' But if Dr. Jurin's opi- 
 nion be true, mod: young people that fquint 
 may cure themfelves, by taking fome pains ; 
 and may not .only remove the deformity, but 
 at the fame time improve their. fight. If the 
 common opinion be true, the centres and other 
 points of the two retina in fquinting perfons do 
 not correfpond as in other men, 'and nature in 
 them deviates from her common rule. But if 
 Dr. Jurin's opinion be true, there is reafon to 
 think, that the fame general law of vifion which. 
 
 S 2 we 
 
276 Ofthe HUMAN MIND. Chap. VI. 
 we have found in perfect human eyes, extends 
 alfo to thofe which fquint. 
 
 It is impofiible to determine, by reafoning, 
 which of thefe opinions is true •, or whether 
 one may not be found true in fome patients, 
 and the other in others. Here, experience and 
 obfervation are our only guides ; and a deduc- 
 tion of inftances is the only rational argument. 
 It might therefore have been expected, that 
 the patrons of the contrary opinions Ihould have 
 given inftances, in fupport of them, that are clear 
 and indifputable : but I have not found one fuch 
 inftance on either fide of the queftion, in all 
 the authors I have met with. I have given 
 three inftances from my own obfervation, in 
 confirmation of Dr. Jurin's opinion, which ad- 
 mit of no doubt ; and one which leans rather 
 to the other opinion, but is dubious. And 
 here I muft leave the matter to fucther obferva- 
 tion. 
 
 In the 17th fection, I have endeavoured to 
 fhew,- that the correfpondence and fympathy of 
 certain points of the„two retina, into which we 
 have refolved all the phasnomena of fingle and 
 double vifion, is not, as Dr. Smith conceived, 
 the effect of cuftom, nor can be changed by 
 cuftpm, but is a natural and original property 
 of human eyes : and in the laft fection, that it 
 is not owing to an original and natural percep- 
 tion, of the true diftance of objects from the 
 eye, as Dr. 'Porterfield imagined, lifter this 
 recapitulation^ which is intended to relieve the 
 . 2 attention 
 
Seft. 19. Of SEEING. 277 
 
 attention of the reader, fhall we enter into more 
 theories upon this fubject ? 
 
 That of Dr. Briggs, firft publifhed in Englifh, 
 in the Philofophical Tranfactions, afterwards in 
 Latin, under the title of Neva vifwnis theoria, 
 with a prefatory epiftle of Sir Ifaac Newton to 
 the author, amounts to this, That the fibres of 
 the optic nerves pafiingfrom correfponding points 
 of the retina to the tbalami nervorum opticorum, 
 having the fame length, the fame tenfion, and 
 a fimilar fatuation, will have the fame tone ; and 
 therefore their vibrations, excited by the impref- 
 fion of the rays of light, will be like uniibns in 
 mufic, and will prefent one and the fame image 
 to the mind : but the fibres paffing from parts 
 of the retina which do not carrefpond, having 
 different tenfions and tones, will have difcordant 
 vibrations'; and therefore prefent different images 
 to the mind. 
 
 I fhall not enter upon a particular examina- 
 tion of this theory. It is enough to obferve in 
 general, that it is a fyftem of conjectures con- 
 cerning things of which we are entirely igno- 
 rant; and that all fuch theories in philofophy 
 deferve rather to be laughed at, than to be fe- 
 rioufly refuted. 
 
 From the firft dawn of philofophy to this 
 day, it hath been believed that the optic nerves 
 are intended to carry the images of vifible ob- 
 jects from the bottom of the eye to the mind ; 
 and that the nerves belonging to the organs of 
 the other fenfes have a like office. But how 
 
 S3 d0 
 
278 Of the HUMAN MIND. Chap. VI. 
 do we know this ? We conjecture it : and ta- 
 king this conjecture for a truth, we confider how 
 the nerves may belt anfwer this purpofe. The 
 fyftem of the nerves, for many ages, was taken 
 to be a hydraulic engine, confifting of a bundle 
 of pipes which carry to and fro a liquor called 
 animal /pit its. About the time of Dr. Briggs, 
 it was thought rather to be a ftringed inftrument, 
 compofed of vibrating chords, each of which 
 had its proper tenfion and tone. But fome, 
 with as great probability, conceived it to be a 
 wind inftrument, which played its part by the 
 vibrations of an elaftic aether in the nervous 
 fibrils. 
 
 Thefe, I think, are all the engines into which 
 the nervous fyftem hath been moulded by phi- 
 lofophers, for conveying the images of fenfible 
 things from the organ to the fenforium. And 
 for all that we know of the matter, every man 
 may freely chufe which he thinks fitteft for the 
 purpofe ; for, from fact and experiment, no one 
 of them can claim preference to another. In- 
 deed, they all feem fo unhandy engines for car- 
 rying images, that a man would be tempted to 
 invent a new one. 
 
 Since, therefore, a blind man may guefs as 
 well in the dark as one that fees, I beg leave to 
 offer another conjecture touching the nervous 
 fyftem, which I hope will anfwer the purpofe 
 as well as thofe we have mentioned, and which 
 recommends itfelf by its fimplicity. Why may 
 not the optic nerves, for inftance, be made up 
 
 of 
 
Seel. 19. Of S E E I N G. 279 
 
 of empty tubes, opening their mouths wide 
 enough to receive the rays of light which form 
 the image upon the retina, and gently conveying 
 them fafe, and in their proper order, to the 
 very feat of the foul, until they flafli in her 
 face. It is eafy for an ingenious philofopher to 
 fit the caliber of thefe empty tubes to the dia- 
 meter of the particles of light, fo as they (hall 
 receive no groffer kind of matter. And if thefe 
 rays mould be in danger of miftaking their way, 
 an expedient may alfo be found to prevent 
 this. For it requires no more than to beftow 
 upon the tubes of the nervous fyftem a pe- 
 riftaltic motion, like that of the alimentary 
 tube. 
 
 It is a peculiar advantage of this hypothefis, 
 that, altho' all philofophers believe that the 
 {pedes or images of things are conveyed by the 
 nerves to the foul, yet none of their hypothefes 
 fliew how this may be done. For how can the 
 images of found, tafte, fmell, colour, figure, and 
 all fenfible qualities, be made out of the vibra- 
 tions of mufical chords, or the undulations of - 
 animal fpirits, or of asther ? We ought not to 
 fuppofe means inadequate to the end. Is it not 
 as philofophical, and more intelligible, to con- 
 ceive, that as the ftomach receives its food^ fo 
 the foul receives her images by a kind of ner- 
 vous deglutition ? I might add, that we need 
 only continue this periftaltic motion of the ner- 
 vous tubes from the fenforium to the extremities 
 
 S 4 of. 
 
a$o OFthe HUMAN MIND. Chap. VI. 
 
 of the nerves that ferve the mufcles, in order to 
 account for mufcular motion. 
 
 Thus nature will be confonant to herfelf; and 
 as fenfation will be the conveyance of the ideal 
 aliment to the mind, fo mufcular motion will 
 be the expulfion of the recrementitious part of 
 it. For who can deny, that the images of 
 things cenveyed by fenfation, may, after dug 
 ccncoflion, become fit to be thrown off by 
 mufcular mot : on ? I only give hints of thefe 
 things to the ingenious, hoping that in time 
 th:s hypothefis may be wroughtAlp into a fyftem 
 as truly philofophical, as that of animal {pints, 
 or the vibration of nervous fibres. 
 
 To be ferious : In the operations of nature, I 
 hold the theories of a philofopher, which are 
 nnfupported by fact, in the fame eftimation with 
 the dreams of a man aileep, or ihe ravings of a 
 madman. We laugh at the Indian philofopher, 
 who, to account for the fupport of the earth, 
 con rived the hypothefis of a huge elephant, and 
 to fupport the elephant, a huge tortoife. If we 
 will candidly confefs the truth, we know as 
 little of the operation of the nerves, as he did 
 of the manner in which the earth is fupported ; 
 and our hypothefes about animal fpirits, op 
 about the tenfion and vibrations of the nerves, 
 are as like to be true, as his about the fupport 
 of the earth. His elephant was a hypothefis, 
 and our hypothecs are elephants. Every theory 
 in philoiophy, which is built on pure conjecture, 
 is an elephant ; and every theory that is fupport- 
 
 c4 
 
Se&. 19. Of S E E IN G. 281 
 
 ed partly by faft, and partly by conjecture, is 
 like Nebuchadnezzar's image, whofe feet were 
 partly of iron, and partly of clay. 
 
 The great Newton firft gave an example to 
 philofophers, which always ought to be, but:' 
 rarely hath been followed, by diftinguifhing his 
 conjectures from his conclufions, and putting the 
 former by themfelves, in the modeft form of 
 queries. This is fair and legal; but all other' 
 philosophical traffick in conje&ure, ought to be 
 held contraband and illicit. Indeed his conjec- 
 tures have commonly more foundation in faft % 
 and more verifimilttude, than the dogmatical 
 theories of moft other philofophers ; and there- 
 fore we ought not to omit that which he hath 
 offered concerning the caufe of our feeing ob- 
 jects fingle with two eyes, in the 15th query an- 
 nexed to his Optics. 
 
 " Are not the fpecies of objects feen.with 
 " both eyes, united where the optic nerves 
 " meet before they come into the . brain, the 
 *' fibres on the right fide of both nerves uniting 
 •** there, and after union going thence into the 
 " brain in the nerve" 'which is on. the right fide. 
 " of the head, and the fibres on the left fide 
 ** of both nerves unking in the fame place, and 
 " after union going into the brain in the nerve 
 ." which is on the left fide of the head, and 
 " thefe two neryes meeting in the brain in fuch 
 ;*' a manner that their fibres make but one en- 
 .** tire fpecies or pi&ure, half of "which on the 
 .*.* fight fide of the fenfprium comes from the 
 
 « right 
 
a«2 Ofthe HUMAN MIND. Chap. VI. 
 
 " right fide of both eyes through the right fide 
 " of both optic nerves, to the place where the 
 " nerves meet, and from thence on the right 
 " fide of the head into the brain, and the other 
 " half on the left fide of the fenforium comes, 
 *' in like manner, from the left fide of both 
 " eyes ? For the optic nerves of fuch animals 
 " as look the fame way with both eyes (as men, 
 «' dogs, fheep, oxen, &c.) meet before they 
 " come into the brain ; but the optic nerves 
 " of fuch animals as do not look the fame way 
 " with both eyes, (as of fifties and of the cha- 
 " meleon) do not meet, if I am rightly in- 
 " formed." 
 
 I beg leave to diftinguilh this query into two, 
 which are of very different natures ; one being 
 purely anatomical, the other relating to the car- 
 rying fpecies or pictures of vifible objects to the 
 fenforium. 
 
 The firfb queftion is, Whether the fibres com- 
 ing from correfponding points of the two retina, 
 do not unite at the place where the optic nerves 
 meet, and continue united from thence to the 
 brain ; fo that the right optic nerve, after the 
 meeting of the two nerves, is compofed of the 
 fibres coming from the right fide of both re- 
 tina, and the left, of the fibres coming from the 
 left fide of both retina t 
 
 This is undoubtedly a curious and rational 
 queftion; becaufe, if we could find ground from 
 anatomy to anfwer it in the affirmative, it would 
 lead us a ftep forward in difcovering the caufe of 
 
 the 
 
Seft. ig: Of SEEIN G. 283 
 
 the correfpondence and fympathy which there is 
 between certain points of the two retina. For 
 akho' we know not what is the p%rtipular func- 
 tion of the optic nerves, yet it is probable that 
 fome impreffion made upon them, and commu- 
 nicated along their fibres, ' is neceflary to virion : 
 And whatever be the nature of this impreffion, if 
 two fibres are united into one, an impreffion made 
 upon one of them, or upon both, may probably 
 produce the fame effect. Anatomifts think it a fuf- 
 ficient account of a fympathy between two parts 
 of the body, when they are ferved by branches 
 of the fame nerve : we Ihould therefore look up- 
 on it as an important difcovery in anatomy, if it , 
 were found that the fame nerve fent branches to 
 the correfponding points of the retina. 
 
 But bath any fuch difcovery been made ? No* 
 not fo much as in one fubjeft, as far as I can 
 learn. But in feveral fubjefts, the contrary feems 
 to have been difcovered. Dr. Porterfield hath 
 given us two cafes at length from Vefalius, and 
 one from Csefalpinus, wherein the optic nerves, 
 after touching one another as ufual, appeared to 
 be refleded back to the fame fide whence they 
 came, without any mixture of their fibres. Each 
 of thefe perfons had loft an eye fometime before 
 his death, and the optic nerve belonging to that 
 eye was fhrunk, fo that it could be diftinguifned 
 from the other at the place where they met. An- 
 other cafe which the fame author gives from 
 Vefalius, is ftill more, remarkable ; for in it the 
 optic nerves did not touch at all ; and yet, upon 
 
 inquiry, 
 
284 Of the HUMAN MIND. Chap. VI. 
 
 inquiry, thefe who were raoft familiar with the 
 perfon in his lifetime, declared that he never com- 
 plained of any defect of fight, or of his feeing 
 objects double. Diemerbrocck tells us, that 
 Aquapendens and Valverda likeways affirm, that 
 they have met with fubjects wherein the optic 
 nerves did not touch., 
 
 As thefe obfervations were made before Sir 
 Ifaac Newton put this query, it is uncertain whe- 
 ther he was ignorant of them, or whether he 
 fufpected fome inaccuracy in them, and defired 
 that the matter might be more carefully examin- 
 ed. But from the following paflage of the moft 
 accurate Window, it does not appear, that later 
 obfervations have been more favourable to his 
 conjecture. " The union of thefe [optic] nerves, 
 *' by the fmall curvatures of their cornua, is ve- 
 " ry difficult to be unfolded in human bodies. 
 ♦' This union is commonly found to be very 
 *' clofe, but in fome fubjects it feems to be no 
 " more than a ftrong gdhefion, in others to be 
 " partly made by an interferon or croffing of 
 " fibres. They have been found quite feparate; 
 " and in other fubjects, one of them has been 
 " found to be very much altered both in fize 
 " and colour through its whole paflage, the 
 f other remaining in its natural ftate." 
 
 When'we confider this conjecture of Sir Ifaac 
 Newton by itfelf, it appears more ingenious, and 
 to have more verifimilitude, than any thing that 
 has been offered upon the fubject j and we ad- 
 mire, the caution and modeity of the author, in 
 
 pro* 
 
Sett. 19. Of SEEING. 285 
 
 propofing it only as a fubject of inquiry : but 
 when we compare it with the obferyations of 
 anatomifts which contradict it, we are naturally- 
 led to this reflection, That if we truft to the 
 conjectures of men of the greateft genius in the 
 operations of nature, we have only the chance 
 of going wrong in an ingenious manner. 
 
 The fecond part of the query is, Whether the 
 two fpecies of obje&s from the two eyes are not, 
 at the place where the optic nerves meet, united 
 into one fpecies or picture,, half of which is car- 
 ried thence to the fenforium in the right optic 
 nerve, and the other half in the left ? and whe- 
 ther thefe two halves are not fo put together 
 again at the fenforium, as to make one fpecies or 
 picture ? 
 
 Here it feems natural to, put the previous 
 queftion, What reafon have we to believe, that 
 pictures of objects are at all carried to the fenfo- 
 rium, either by the optic nerves, or by any 
 other nerves ? Is it not poflible, that this great 
 philofopher, as well as many of a lower form, 
 having been led into this opinion at firft by edu- 
 cation, may have continued in it, becaufe he ne- 
 ver thought of calling it in queftion ? I confefs 
 this was my own cafe for a considerable part of 
 my life. But fince I was led by accident to think 
 ferioufly what reafon I had to believe it, I could 
 find none at all. It feems to be a mere hypothe- 
 cs, as much as the Indian philofopher's elephant. 
 I am not confcious of any pictures of external ob- 
 jects in my fenforium, any more than in my 
 
 ftomath : 
 
z86 OftheHUMAN MIND. Chap. VI. 
 
 ftomach : the things which I perceive by my 
 fenfes, appear to be external, and not in any part 
 of the brain ; and my fenfations, properly fo 
 called, have norefemblance of external objects. 
 
 The conclufion. from all that hath been faid, 
 in no lefs than feven feflions, upon our feeing 
 objects fingle with two eyes, is this, That, by 
 an original property of human eyes, objects 
 painted upon the centres of the two retina, or 
 upon points fimilarly fituate with regard to the 
 centres, appear in the fame vifible place ; that 
 the moft plaufible attempts to account for this 
 property of the eyes, have been unfuccefsful j 
 and therefore, that it muft be either a primary 
 law of our conflitution, or the confequence of 
 fbme more general law which is not yet difco- 
 vered. 
 
 We have now finifhed what we intended to 
 fay, both of the vifible appearances of things to 
 the eye, and of the laws of our conflitution by 
 ■which thofe appearances are exhibited. But it 
 was obferved, in the beginning of this chapter, 
 that the vifible appearances of objedls ferve only 
 as figns of their diftance, magnitude, figure, and 
 other tangible qualities. The vifible appearance 
 is that which is prefented to the mind by nature, 
 according to thofe laws of our conflitution which 
 have been explained. But the thing fignified by 
 that appearance, is that which is prefented to the 
 mind by cuftom. 
 
 When one fpeaks to us in a language that is 
 familiar, we hear certain founds, and this is all 
 
 the 
 
Sea. 19. Of SEEING. 287 
 
 the effecl: that his difcpurfe has upon us by na- 
 ture : but by cuftom we underftand the mean- 
 ing of thefe founds ; and therefore we fix our 
 attention, not upon the founds, but upon the 
 things fignified by them. In like manner, we fee 
 only the vifible appearance of objects, by nature; 
 but we learn by cuftom to interpret thefe appear- 
 ances, and to underftand their meaning. And 
 when this vifual language is learned, and becomes 
 familiar, we attend only to the things fignified ; 
 and cannot, without great difficulty, attend to the 
 figns by which they are prefe*nted. The mind 
 pafles from one to the other fo rapidly, and fo 
 familiarly, that no trace of the fign is left in the 
 memory, and we feem immediately, and without 
 the intefvention of any fign, to perceive the 
 thing fignified. 
 
 When I look at the apple-tree which ftands 
 before my window, I perceive, at the firft glance, 
 its diftance and magnitude, the roughnefs of its 
 trunk, the difpofition of its branches, the figure 
 of its leaves and fruit. I feem to perceive all 
 thefe things immediately. The vifible appearance 
 which prefented them all to the mind, has en- 
 tirely efcaped me ; I cannot, without great diffi- 
 culty, and painful abftradion, attend to it, even 
 when it ftands before me. Yet it is certain that 
 this vifible appearance only, is prefented to my 
 eye by nature, and that I learned by cuftom to 
 collect allthe reft from it. If I had never feen 
 before now, I fhould not perceive either the di- 
 ftance or tangible figure of the tree, and it would 
 4 fcave 
 
288 Ofthe HUMAN MIND. Chap. VI. 
 
 have required the practice of leeing for many 
 months, to change that original perception Avhich. 
 nature gave me by my eyes, into that which I 
 now have by cuftom. 
 
 The objects which we fee naturally and origi- 
 nally, as hath been before obferved, have length 
 and breadth, but no thicknefs, nor diftance from 
 the eye. Cuftom, by a kind of legerdemain, 
 withdraws gradually thefe original and proper 
 objects of fight, and fubftitutes in their place ob- 
 jects of touch, which have* length, breadth, and 
 thicknefs, and a determinate diftance from the 
 eye, By what means this change is brought 
 about, and what principles of the human mind 
 concur in it, we are next to inquire. 
 
 SECT. XX. 
 
 Of perception in general. 
 
 CEnsation, and the perception of external 
 objects by the fenfes, tho' very different in 
 their nature, have commonly been confidered as 
 one and the fame thing. The purpofes of com- 
 mon life do not make it necefiary to diftinguifh 
 them, and the received opinions of philofophers 
 tend rather to confound them : but, without at- 
 tending carefully to this diftin&ion, it is impof- 
 fible to have any juft conception ofthe operations 
 of our fenfes. The moft fimple operations ofthe 
 mind, admit not of a logical definition : all we 
 can do is to defcribe them, fo as to lead thofe 
 who are confcious of them in themfelves, to at- 
 tend 
 
Seft. 20; Of S E E I N G. 289 
 
 tend to them, and reflect upon them : and it is 
 often very difficult to defcribe them fo as to an- 
 fwer this intention. 
 
 The fame mode of expreffion is ufed to de- 
 note fenfation and perception ; and therefore we 
 are apt to look upon them as things of the fame 
 nature. Thus, I feel a pain ; 1 fee a tree : the 
 firft denoteth a fenfation, the laft a perception. 
 Thegrammaticalanalyfis of bothexpreffionsis the 
 fame : for both confift of an adtive verb and an 
 object. But, if we attend to the things fignified 
 by thefe expreffions, we mail find, that in the firft, 
 the diftindtion between the aft and the objedr. is 
 not real but grammatical; in the fecond, the 
 diftindtion is not only grammatical but real. 
 
 The form of the expreffion, I feel pain, might 
 feem to imply, that the feeling is fomething dif- 
 tindt from the pain felt ; yet, in reality, there 
 is no diftindtion. As thinking a thought is an ex- 
 preffion which could fignify no more than think- 
 ing, to feeling a pain fignifies no more than being 
 pained. What we have faid of pain is applicable 
 to every other mere fenfation. It is difficult to 
 give inftances, very few of our fenfations having 
 names ; and where they have, the name being 
 common to the fenfation, and to fomething elfe 
 which is affociated with it. But when we attend 
 to the fenfation by itfelf, and feparate it from 
 other things which are conjoined with it in the 
 imagination, it appears to be fomething which 
 can have no exiftence but in a fentient mind, no 
 T diftindtion 
 
290 Of the HUMAN MIND. Chap.VL 
 
 diftindtion from the aft of the mind by which ie 
 is felt. 
 
 Perception, as we here underftand it, hath al- 
 ways an object diftincl: from the act by which it 
 is perceived ; an object which may exift whether 
 it be perceived or not. I perceive a tree that 
 grows before my window ; there is here an ob- 
 ject which is perceived, and an a£t of the mind 
 by which it is perceived ; and thefe two are not 
 only diftinguifhable, but they are extremely un- 
 like in their natures. The object is made up of a 
 trunk, branches, and leaves ; but the a£t of the 
 mind by which it is perceived, hath neither trunk, 
 branches* nor leaves. I am confcious of this act 
 of my mind, and I can refleft upon it ; but it is 
 too ample to admit of an analyfis, and I cannot 
 find proper words to defcribe it. I find nothing 
 that refembles k fo much as the remembrance of 
 the tree, or the imagination of it. Yet both thefe 
 differ effentially from perception; they differ 
 likewife one from another. It is in vain that a 
 philofopher affures me, that the imagination of 
 the tree, the remembrance of it, and the percep- 
 tion of it, are all one, and differ only in degree 
 of vivacity. I know the contrary ; for I am as 
 well acquainted with all the three, as I am with 
 the apartments of my own houfe. I know this al- 
 fo, that the perception of an objedt implies both 
 a conception of its form, and a belief of its pre- 
 fent exiftence. I know moreover, that this belief 
 is not the effect of argumentation and reafoningi. 
 it is the immediate effect of my constitution. 
 
 I am 
 
Seel:. 20. Of SEEING. 29 1 
 
 I am aware, that this belief which I have in 
 perception, ftands expofed to the ftrongeft bat- 
 teries of fcepticifm. But they make no great im- 
 preflion upon it. The fceptic afks me, Why do 
 you believe the exiftence of the external objedt 
 which you perceive ? This belief, Sir, is none of 
 my manufacture-, it came from the mint of nature; 
 it bears her image and fuperfcription ; and, if it 
 is not right, the fault is not mine : I even took 
 itupontruft, and without fufpicion. Reafon, fays 
 the fceptiCj is the only judge of truth, and you 
 ought to throw off every opinion and every be- 
 lief that is not grounded on reafon. "Why, Sir, 
 ftiould I believe the faculty of reafon more than 
 t'hat of perception ; they came both out of the 
 fame fhop, and were made by the fame artift ; 
 and if he puts one piece of falfe ware into my 
 hands, what mould hinder him from putting an* 
 other ? 
 
 Perhaps the fceptic will agree to diftruft rea- 
 . fon, rather than give any credit to perception. 
 For, fays he, fince, by your own conceffion, the 
 object which you perceive, and that act of your 
 mind, by which you perceive it, are quite differ- 
 ent things, the one may exift without the other ; 
 and as the object may exift without being per- 
 ceived, fo the perception may exift without an 
 objedt. There is nothing fo fhameful in a philo- 
 sopher as to be deceived and deluded ; and there- 
 fore you ought to refojve firmly to with- hold 
 aflenr, and to throw off this belief of external ob- 
 jects, which may be all delufion. For my part, 
 T 2 I wiU 
 
2:92 OftHeHUMAK MTND. Chap.Vl. 
 I will never attempt to throw it off; and altho' 
 the fober part of mankind will not be very- 
 anxious to know my reafons, yet if they can be 
 of ufe to any fceptic, they are thefe. 
 
 Firft, Becaufe it is not in my power : why 
 then mould I make a vain attempt ? It would be 
 agreeable to fly to the moon, and to make a 
 vifit to Jupiter and Saturn ; but when- I know 
 that nature has bound me down by the law of 
 gravitation to this planet which I inhabit, I reft 
 contented, and quietly fuffer myfelf to be carried 
 along in its orbit. My belief is carried along by 
 perception, as irrefiftibly as my body by the 
 earth. And the greateft fceptic will find him- 
 felf to be in the fame condition. He may ftrug- 
 gle hard to difbelieve the informations of his fen- 
 fes, as a man does to fwim againft a torrent; but 
 ah ! it is in vain. It is in vain that he (trains 
 every nerve, and wreftles with nature, and with 
 every object that ftrikes upon his fenfes. For 
 after all, when his ftrength is fpent in the fruit- 
 lefs attempt, he will be carried down the torrent 
 with the common herd of believers. 
 
 Secondly, I think it would not be prudent to 
 throw off this belief, if it were in my power. If 
 Nature intended to deceive me, and impofe upon 
 me by falfe appearances, and I, by my great 
 cunning and profound logic, have difcovered the 
 Lmpoiture •, prudence would didtate to me in this 
 cafe, even to put up this indignity done me, as. 
 quietly as I could, and not to call her an impo- 
 stor- to her face, left fhe ,I*iould be even with me 
 
 i» 
 
Seft. ao. Of SEEING. 293 
 
 in another way. For what do I gain by refent- 
 ing this injury? You ought at leaft not to believe 
 what fhe fays. This indeed feems reafonable, if 
 fhe intends to impofe upon me. But what is the 
 confequence ? I refolve not to believe my fenfes. 
 I break my nofe againft a poll that comes in my 
 way ; I ftep into a dirty kennel ; and, after 
 twenty fuch wife and rational a&ions, I am 
 taken up and clapt into a mad-houfe. Now, I 
 confefs I would rather make one of the credu- 
 lous fools whom Nature impofes upon, than of 
 thofe wife and rational philofophers who refolve 
 to with-hold aflent at all this expence. If a 
 man pretends to be a fceptic with regard to the 
 informations of fenfe, and yet prudently keeps 
 out of harm's way as other men do, he muft ex- 
 cufe my fufpicion, that he either acts the hypo- 
 crite, or impofes upon himfelf. For if the 
 fcale of his belief were fo evenly pOifed, as to 
 lean no more to one fide than to the contrary, 
 it is impofiible that his actions could be directed 
 by any rules of common prudence. 
 
 Thirdly, Although the two reafons already 
 mentioned are perhaps two more than enough, 
 I (hall offer a third. I gave implicit belief to 
 the informations of Nature by my fenfes, for a 
 ronfiderable part of my life, before I had learned 
 fo much logic as to be able to ftart a doubt con- 
 cerning them. And now, when I reflect upon 
 what "is paft, I do not find that 1 have been im- 
 pofed upofi by this belief. I find, that without 
 jt I muft have perifhed by a thoufand accidents. 
 Tj I find, 
 
2 9 4- Oftfie HUMAN MIND. Chap. VI, 
 I find, that without it I fhould have been no 
 wifer now than when 1 was born. I fhould not 
 even have been able to acquire that logic which 
 fuggefts thefe fceptfcal doubts with regard to my 
 fenfes. Therefore, I confider this inftinftive 
 belief as one of the bed gifts of Nature. I 
 thank the Author of my being who bellowed it, 
 upon me, before the eyes of my reafon were 
 opened, and ftill beftows it upon me to be my 
 guide, where reafon leaves me in the dark. And 
 now I yield to the direction of my fenfes, not 
 from inftincl only, but from confidence and 
 trufr. in a faithful and beneficent monitor, ground- 
 ed upon the experience of his paternal care and, 
 goodnefs. 
 
 In all this, I deal with the Author of my be- 
 ing, no otherways than I thought it reafonable to 
 deal with my parents and tutors. I believed by 
 jnftindr. whatever they told me, long before I 
 had the idea of a lie, or thought of the pofiibi- 
 lity of their deceiving me. Afterwards, upon 
 reflection, I found they had acled like fair and 
 hbneft people who wifhed me well. I found, 
 that if I had pot believed what they told me, 
 before I could give a reafon pf my belief, I had 
 to this day been little better than a changeling. 
 And although this natural credulity hath fome- 
 times occasioned my being impofed upon by de- 
 ceivers, yet jt hath been of infinite advantage 
 to me upon the whole; therefore I confider it 
 as another good gift of Nature. And I con- 
 tinue to give that credit frorn reflection, to 
 
 thafs 
 
Se&. 20. Of S E E I N G. 295 
 
 thofe of whofe integrity and veracity I have had 
 experience, which before I gave from inftincl. 
 
 There is a much greater fimilitude than is com- 
 monly imagined, between the teftimony of na- 
 ture given by our fenfes, and the teftimony of 
 men given by language. The credit we give to 
 both is at firft the effect of inftinfl only. When 
 we grow up, and begin to reafon about them, 
 the credit given to human teftimony, is reftrain- 
 ed, and weakened, by the experience we have 
 of deceit. But the credit given to the 'teftimo- 
 ny of our fenfes, is eftablilhed and confirmed by 
 the uniformity and conftancy of the laws of na- 
 ture. 
 
 Our perceptions are of two kinds : fome are 
 natural and original, others acquired, and thefruit 
 of experience. When I perceive that this is the 
 tafte of cyder, that of brandy ; that this is the 
 fmell of an apple, that of an orange ; that this 
 , is the noife of thunder, that the ringing of bells ; 
 this the found of a coach palling, that the voice 
 of fuch a friend ; thefe perceptions, and others 
 of the fame kind, are not original, they are ac- 
 quired. But the perception which I have by 
 touch of the hardnefs and foftnefs of bodies, of 
 their extenfion, figure, and motion, is not ac- 
 quired, it is original. 
 
 , In all our fenfes, the acquired perceptions are 
 many more than the original, efpecially in fight. 
 By this fenfe we perceive originally the vifible 
 figure and colour of bodies only, and their vifi- 
 ble place ; but we learn to perceive by the eye, 
 T 4 almolt 
 
2 9 6 Ofthe HUMAN MIND. Chap. VI. 
 almoft every thing which we can perceive by 
 touch. The original perceptions of this fenfe, 
 ferve only as figns to introduce the acquired. 
 
 The figns by which objefts are prefented to 
 us in perception, are the language of nature to 
 rrian ; and as, in many refpedts, it hath great 
 affinity with the language of man to man ; fo 
 particularly in this, that both are partly na- 
 tural and original, partly acquired by cuftom. 
 Our original or natural perceptions are analogous 
 to the natural language of man to man, of which 
 we took notice in the 4th chapter-, and our ac- 
 quired perceptions are analogous to artificial lan- 
 guage, which, in our mother-tongue, is got very 
 much in the fame manner with our acquired per- 
 ceptions, as we fhall afterwards more fully explain. 
 
 Not only men, but children, idiots, and 
 brutes, acquire by habit many perceptions which 
 they had not originally. Almoft every employ- 
 ment in life, hath perceptions of this kind that 
 are peculiar to it. The fhepherd knows every 
 fheep of his flock, as we do our acquaintance, 
 and can pick them out of another flock one by 
 one, The butcher knows by light the weight 
 and quality of his beeves and fheep before they 
 are killed. , The farmer perceives by his eye, 
 very nearly, the quantity of hay in a rick, or 
 of corn in a heap. The failor fees the burthen, 
 the built, and the diftance of a fhip at fea, 
 while fhe is a great way off. Every man ac- 
 cuftomed to writing, diftinguifhes his acquaint- 
 ance by their hand-writing, as he does by their 
 
 faces. 
 
Seft. 20. Of SEEING.. 297 
 
 faces. And the painter diftinguifhes in the 
 works of his art, the ftyle of all the great ma- 
 ilers. In a word, acquired perception is very 
 different in different perfons, according to the 
 diverfity of objects about which they are em- 
 ployed, and the application they bellow in ob- 
 ferving them. 
 
 Perception ought not.only to be diftinguifhed 
 from fenfation, but likewife from that knowledge 
 of the objects of fenfe which is got by reafoning. 
 There is no reafoning in perception, as hath been 
 obferved. The belief which is implied in it, is 
 the effect of inftinct. But there are many things,, 
 with regard to fenfible objects, which we can in- 
 fer from what we perceive ; and fuch conclufions 
 of reafon ought to be diftinguifhed from what is 
 merely perceived. "When I look at the moon, 
 I perceive her to be fometimes circular, fome- 
 times horned, and fometimes gibbous. This is 
 fimple perception, and is the fame in the philo- 
 sopher, and in the clown : but from thefe various 
 appearances of her enlightened part, I infer that 
 £he is really of a fpherical figure. This con- 
 clufion is not obtained by fimple perception, but 
 by reafoning. Simple perception has the fame 
 relation to the conclufions of reafon drawn from 
 our perceptions, as the axioms in mathematics 
 have to the propofitions. I cannot demonftrate, 
 that two quantities which are equal to the fame 
 quantity, are equal to each other ; neither can I 
 demonftrate, that the tree which I perceive, 
 psifts. But, by the conftitution of my nature, 
 t my 
 
2 9 8 Of the HUMAN MIND. Chag.VI. 
 my belief is irrefiftibly carried along by my ap- 
 prehension of the axiom ; and by the conftku- 
 tion of my nature, my belief is no lefs irrefiftibly 
 carried along by my perception of the tree. All 
 reafoning is from principles. The firft principles 
 of mathematical reafoning are mathematical axi- 
 oms and definitions ; and the firft principles ofall 
 our reafoning about existences, are our percep- 
 tions. The firft principles of every kind of reafon- 
 ing are given us by nature, and are of equal au- 
 thority with the faculty of reafon itfelf, which is 
 alfo the gift of nature. The conclufions of rea- 
 fon are all built upon firft principles, and can 
 have no other foundation. Moft juftly, there- 
 fore, do fuch principles difdain to be tried by 
 reafon, and laugh at all the artillery of the logi- 
 cian, when it is directed againft them. 
 
 When a long train of reafoning is necesTary 
 in demonstrating a mathematical propofition, it 
 is eafily distinguished from an axiom, and they 
 feem to be things of a very different nature. 
 But there are fome propositions which lie fo 
 near to axioms, that it is difficult to fay, 
 whether they ought to be held as axioms, or 
 demonstrated as propositions. The fame thing 
 holds with regard to perception, and the con- 
 clufions drawn from it. Some of thefe con- 
 clufions follow our perceptions fo eafily, and 
 are -fo immediately connected with them, that 
 it is difficult to fix the' limit which divides the 
 pne from the other. 
 
 Perception 
 
Seft. 20. Of S E E I N G. 299 
 
 Perception, whether original or acquired, 
 implies no exercife of reafon ; and is common 
 to men, children, idiots, and brutes. The 
 more obvious conclufions drawn from our per- 
 ceptions, by reafon, make what we call com- 
 mon underfianding ; by which men conduct thenih?' 
 felves in the common affairs of life, and by 
 which they are diftinguifhed from idiots. The 
 more remote conclufions which are drawn from 
 our perceptions, by reafon, make what we com- 
 monly call fcience in the various parts of na- 
 ture, whether in agriculture, medicine, me- 
 chanics, or in any part of natural philofophy. 
 When I fee a garden in good order, containing 
 a great variety of things of the beft kinds, and 
 in the moft flourifhing condition, I immediate- 
 ly conclude from thefe figns, the fkill and in- 
 duftry of the gardener. A farmer, when he 
 rifes in the morning, and perceives that the 
 neighbouring brook overflows his field, con- 
 cludes that a great deal of rain hath fallen in 
 the night. Perceiving his fence broken, and 
 his corn trodden down, he concludes that fome 
 of his own or his neighbours cattle have broke 
 loofe. Perceiving that his ftable-door is broke 
 open, and fome of his horfes gone, he con- 
 cludes that a thief has carried them off. He 
 traces the prints 'jof his horfes feet in the foft 
 ground, and by them difcovers which road the 
 thief hath taken. Thefe are inftances of com- 
 mon underftanding, which dwells fo near to 
 perception, tha,t it js difficult to trace the line 
 
 which 
 
goo OftheHUMAN MIND. Chap. VL 
 which divides the one from the other. In like 
 manner, the fcience of nature dwells fo near 
 to common underftanding, that we cannot dif- 
 cern where the latter ends and the former be- 
 gins. I perceive that bodies lighter than water 
 fwim in water, and that thofe which are hea- 
 vier link. Hence I conclude, that if a body 
 remains wherever it is put under water, whether 
 at the top or bottom, it is precifely of the fame 
 weight with water'. If it will reft only when 
 part of it is above water, it is lighter than 
 water. And the greater the part above water 
 is, compared with the whole, the lighter is the 
 body. If it had no gravity at all, it would 
 make no imprefiion upon the water, but (land 
 wholly above it. Thus, every man, by com- 
 mon underftanding, has a rule by which he 
 judges of the fpecific gravity of bodies which 
 fwim in water : anJd a ftep or two more, leads 
 him into the fcience of hydroftatics. 
 
 All that we know of nature, or of exiftences, 
 may be compared to a tree, which hath its root, 
 trunk, and branches. In this tree of know- 
 ledge, perception is the root, common under- 
 ftanding is the trunk, and the fciences are the 
 branches. 
 
 SECT. 
 
Seft.ai. Of SEEDING. 30 J 
 
 SECT. XXI. 
 
 Of the proeefs of nature in perception. 
 
 A Ltho' there is no reafoning in perception, 
 yet there are certain means and inftru- 
 ments, which, by the appointment of nature, 
 muft intervene between the object and our per- 
 ception of it •, and, by thefe, our perceptions are 
 limited and regulated. Firft, if the object is 
 not in contact with the organ of fenfe, there 
 muft be fbme medium which paffes between 
 them. Thus, in vifion, the rays of light ; in 
 hearing, the vibrations of elaftic air ; in fmel- 
 ling, the effluvia of the body fmell'd, muft pafs 
 from the object to the • organ ; otherwife we 
 have no perception. Secondly, There muft be 
 fome action or impreflion uspn the organ of 
 fenfe, either by the immediate application of 
 the object, or by the medium that goes between 
 them. Thirdly, The nerves which go from 
 the brain to the organ, muft receive fome im- 
 preflion by means of that which was made upon 
 the organ ; and, probably, by means of the 
 nerves, fome impreflion muft be made upon the 
 brain. Fourthly, The impreflion made upon 
 the organ, nerves, and brain, is~followed by a 
 fenfation. And, laft of all, This fenfation is 
 followed by the perception of the object. 
 
 Thus our perception of objects is the refult 
 of a train of operations ; fome of which affect 
 
 the 
 
$oi Of the HUMAN MlftD. CHap.VL 
 the body only, others affect the mind. We 
 know very little of the nature of fome of thefe 
 operations ; we know not at all how they are 
 connected together, of in what wa'y they cori- 
 tribute to that perception which is the refult of 
 the whole : but, by the laws of our conftitu- 
 fion* we perceive objects in this, and in no other 
 way. 
 
 There may be other beings, who can per- 
 ceive external objects without rays of light, of 
 vibrations of air, or effluvia of bodies, without 
 impreffions on bodily organs, or even without 
 fenfations : but we are fo framed by the Author 
 of nature, that even when we are furrounded 
 by external objects, we may perceive none of 
 them. Our faculcy of perceiving an object lies 
 dormant, until it is roufed and ftimulated by a 
 certain correfponding fenfation. Nor is this 
 fenfatton always at hand to perform its office j 
 for it enters into the mind only in confequence 
 of a certain correfponding impreflion made on 
 the organ of fenfe by the object. 
 
 Let us trace this correfpondence of impref- 
 fions, fenfations, and perceptions, as far as we 
 can -, beginning with that which is firft in order, 
 the impreffion made upon the bodily organ. 
 Bur, alas ! we know not of what nature thefe 
 impreffions are, far lefs how they excite fenfa- 
 tions in the mind. 
 
 We know that one body may act upon ana- 
 ther by preffure, by percuffion, by attraction, 
 by repulfion, and probably in many other ways 
 
 which- 
 
Seft. 21. Of SEEING. 303 
 
 which we neither know, nor have names to ex- 
 prefs. But in which of thefe ways objects* 
 when perceived by us, act upon the organs of 
 fenfe, thefe organs upon the nerves, and the 
 nerves upon the Brain, we know not. Can any 
 man tell me how, in vifion, the rays of light 
 aft upon the retina, how the retina acts upon 
 the optic nerve, and how the optic nerve acts 
 upon the brain ? No man can. When I feel 
 the pain of the gout in my toe, I know that 
 there is fome unufual imprefiion made upon that 
 part of my body. But of what kind is it ? 
 Are the fmall veflels diftended with fome redun- 
 dant elaftic, or unelaftic fluid ? Are the fibres 
 unufually ftretehed ? Are they torn afunder by 
 force, or gnawed and corroded by fome acrid hu- 
 mour 2 I can anfwer none of thefe queftions. 
 AU that I feel is pain, which is not an impref- 
 iion upon the body, but upon the mind ; and all 
 that I perceive by this fenfation is, that fome dif- 
 temper in my toe occafions this pain. But as 
 I know not the natural temper and texture of 
 my toe when it is at eafe, I know as little what 
 change or diforder of its parts occafions this un- 
 eafy fenfation. In like manner, in every other 
 fenfation there is, without doubt, fome im- 
 prefiion made upon the organ of fenfe ; but an 
 imprefiion of which we know not the nature. 
 It is two fubtile to be difcovered by our fenfes, 
 and we may make a thoufand conjectures with- 
 out coming near the truth. If we underftood 
 the ftru&ure of our organs of fenfe fo minutely, 
 
 as 
 
3 64 Of the HUMAN MIND. Chip. Vt. 
 
 as to difcover what effects are produced upon 
 them by external objects, this knowledge would 
 contribute nothing to our perception of the ob- 
 ject •, for they perceive as diftin&ly who know 
 leaft about the manner of perception, as the 
 greateft adepts. It is neceffary that the impref- 
 fion be made upon our organs, but not that it 
 be known. Nature carries on this p,art of the 
 procefs of perception, without our confciouf- 
 nefs or concurrence. 
 
 But we cannot be unconfcions of the next 
 ftep in this procefs, the fenfation of the mind, 
 which always immediately follows the impref- 
 fion made upon the body. It is effential to a 
 fenfation to be felt, and it can be nothing more 
 than we feel it to be. If we can only acquire 
 the habit of attending to our fenfations, we may 
 know them perfectly. But how are the fenfa- 
 tions of the mind produced by impreffions upon 
 the body ?; Of this we. are abfolut'ely ignorant, 
 having no meaiis'-of .knowing how the body'acts 
 upon the mind, or the mind jupon the body. 
 When we confider the nature, arid attributes of 
 both, they feem to 'be fo different, and fo un- 
 like, that we can find no handle by which the 
 one may lay hold of the other. There is a 
 deep and a dark gulf between them, which our 
 understanding cannot pafs ; and the manner of 
 their correfpondence and intercourfe is abfolute- 
 ly unknown. 
 
 Experience teaches us, that certain impreffions 
 upon the body are conftantly followed by cer- 
 tain 
 
Sect. 2i. 6f SEEING. 305 
 
 tain fenfations of the mind; and that, on the 
 other hand, certain determinations of the mind 
 are conftantly followed by certain motions in the 
 body : but we fee not the chain that ties thefe 
 things together. Who knows but their connec- 
 tion may be arbitrary, and owing to the will of 
 our Maker ? Perhaps the fame fenfations might 
 have been connected with other imprefllons, or 
 other bodily organs. Perhaps we might have been 
 fo made, as to tafte with our fingers, 'to fmell 
 with our ears, and to hear by the nofe. Perhaps 
 we might have been fo made, as to have all the 
 fenfations and perceptions which we have, with- 
 out any impreffion made upon our bodily organs 
 at all. 
 
 However thefe things may be* if Nature had 
 given us nothing more than imprefllons made 
 upon the body, and fenfations in our minds cor- 
 refponding to them, we mould in that cafe have 
 been merely fentient, but not percipient beings. 
 We fhtfuld never have been able to form a con-- 
 ception of any external object, far lefs a belief of 
 its exiftence. Our fenfations have no refemblance 
 to external objects ; nor can we difcover, by our 
 reafon, any neceflary connection between the ex- 
 iftence of the former, and that of the latter. 
 
 We might perhaps have been made of fuch a 
 conftitution, as to have our prefent perceptions 
 connected with other fenfations. We might per* 
 haps have had the perception of external objects, 
 without either imprefllons upon the organs of 
 fenfe, or fenfations. Or laftly, The perceptions 
 
 U we 
 
3 o6 Of the H U M A N M I N D. Chap. VI: 
 
 we have, might have been immediately connect- 
 ed with the impreflions upon our organs, without 
 any intervention of fenfations. This laft feems 
 really to be the cafe in one inftance, to wit, in 
 our perception of the vifible figure of bodies, as 
 was obferved in the 8th fection of this chapter. 
 
 The procefs of Nature in perception by the 
 fenfes, may therefore be conceived as a kind of 
 drama, wherein fome things are performed be- 
 hind the fcenes, others are reprefented to the 
 mind in different fcenfes, one fucceeding another. 
 The imprefiion made by the object upon the or- 
 gan, either by immediate contact, or by fome in- 
 tervening medium, as well as the imprefiion made 
 upon the nerves and brain, is performed behind 
 the fcenes, and the mind fees nothing of it. But 
 every fuch imprefiion, by the laws of the drama, 
 is followed by a fenfation, which is the firft fcene 
 exhibited to the mind ; and this fcene is quickly 
 fucceeded by another, which is the perception of, 
 the object. 
 
 In this drama, Nature is the actor, we are the 
 fpectators. We know nothing of the machinery 
 by means of which every different imprefiion 
 upon the organ, nerves, and brain, exhibits its, 
 correfponding fenfation ; or of the machinery by 
 means of which each fenfation exhibits its corre- 
 fponding perception. We are infpired with the 
 fenfation, and we are infpired with the corre- 
 fponding perception, by means unknown. And 
 becaufe the mind pafies immediately from the 
 fenfation to that conception and belief of the ob- 
 ject 
 
Sect. 21. Of SEEING. 307 
 
 ject which we have in perception, in the fame 
 manner as it paffes from figns to the things figni- 
 fied by them, we have therefore called our fen- 
 fations Jigns of external objects ; finding no word 
 more proper to exprefs the function which nature 
 hath affigned them in perception, and the relation 
 "which they bear to their correfponding objects. 
 
 There is no neceffity of a refemblance between 
 the fign and the thing fignified: and indeed no 
 fenfation can refemble any external object. But 
 there are two things neceffary to our knowing 
 things by means of figns. Firft, That a real con- 
 nection between the fign and thing fignified be 
 eftablifhed, either by the courfe of nature, or by 
 the will and appointment of men. When they 
 are connected by the courfe of nature, it is a na- 
 tural fign i when by human appointment, it is an 
 artificial fign. Thus, fmoke is a natural fign of 
 fire j certain features are natural figns of anger : 
 but our words, whether expreffed by articulate 
 founds or by writing, are artificial figns of our 
 thoughts and purpofes. 
 
 Another requifite to our knowing things by 
 figns is, that the appearance of the fign to the 
 mind, be followed by the conception and belief 
 of the thing fignified. Without this the fign is 
 not underftood or interpreted ; and therefore is 
 no fign to us, however fit in its own nature for 
 that purpofe. „ 
 
 Now, there arethree ways in which the mind 
 
 paffes from the appearance of a natural fign to the 
 
 U 2 con- 
 
3 o8 Of theHUMAN MIND. Chap.VI. 
 conception and belief of the thing fignified j by 
 original principles of our conftitution, by cuftom, 
 and by reafoning. 
 
 Our original perceptions are got in the firft of 
 thefe ways, our acquired perceptions in the fe- 
 cond, and all that reafon difcovers of the courfe 
 of nature, in the third. In the firft of thefe ways, 
 nature, by means of the fenfations of touch, in- 
 forms us of the hardnefs and foftnefs of bodies ; 
 of their extenfion, figure, and motion •, and of 
 that fpace in' which they move and are placed, as 
 hath been already explained in the fifth chapter 
 of this inquiry. And in the fecond of thefe ways 
 fhe informs us, by means of our eyes, of almoft 
 all the fame things which originally we could 
 perceive only by touch. 
 
 In order, therefore, to understand more par- 
 ticularly how we learn to perceive fo many things 
 by the eye, which originally could be perceived 
 only by touch, it will be proper, firft, To point 
 out the figns by which thofe things are exhibited 
 to the eye, and their connection with the things 
 fignified by them j and, fecondly, To confider 
 how the experience of this connection produces 
 that habit by which the mind, without any rea- 
 foning or reflexion, pafies from the fign to the 
 conception and belief of the thing fignified. 
 
 Of all the acquired perceptions which we have 
 by fight, the moft remarkable is the perception 
 of the diftance of objects from the eye ; we fhall 
 therefore particularly confider the figns by which 
 
 this 
 
Seel:. 22. Of S E E I N G. 309 
 
 this perception is exhibited, and only make fome 
 general remarks with regard to the figns which 
 are ufed in other acquired perceptions. 
 
 SECT. XXII. 
 
 Of the figns by which we learn to perceive diftance 
 from the eye. 
 
 TT was before obferved in general, That the ' 
 
 original perceptions of fight are figns which 
 ferve to introduce thofe that are acquired : but 
 this is not to be underftood as if no other figns 
 were employed for that purpofe. There are fe- 
 veral motions of the eyes, which, in order to di- 
 ftindt vifion, muft be varied, according as the ob- 
 ject is more or lefs diftant ; and fuch motions be- 
 ing by habit connected with the correfponding 
 diftancesof the objecl:, become figns of thofe di- 
 ftances. Thefe motions were at firft voluntary 
 and unconfined ; but as the intention of nature 
 was, to produce perfect and diftinc~t vifion by 
 their means, we foon learn by experience to re- 
 gulate them according to that intention only, 
 without the leaft reflexion. 
 
 A fhip requires a different trim for every vari- 
 ation of the direction and ftrength of the wind : 
 and, if we may be allowed to borrow that word, 
 the eyes require a different trim for every de- 
 gree of light, and for every variation of the di- 
 ftance of the object, while it is within certain 
 limits. The eyes are trimmed for a particular 
 object, by contracting certain mufcles, and re- 
 U 3 laxing 
 
3 io. Of the H U M A N M 1 N D. Chap. VI. 
 laxing others ; as the (hip is trimmed for a parti- 
 cular wind by drawing certain ropes., and flack- 
 ening others. The failor learns the trim of his 
 Ihip, as we learn the trim of our eyes, by expe- 
 rience. A fhip, akho' the nobleft machine that 
 human art can boaft, is far inferior to the eye in 
 this refpe£t, that it requires art and ingenuity to 
 navigate her ; and a failor muft know what ropes 
 he muft pull, and what he muft flacken, to fit 
 her to a particular wind : but with fuch fuperior 
 wifdom is the fabric of the eye, and the princi- 
 ples of its motion contrived, that it requires no 
 art nor ingenuity to fee by it. Even that part 
 of vifion which it got by experience, is attained 
 by idiots. We need not know what mufcles 
 we are to contract, and what we are to relax, in 
 order to fit the eye to a particular diftance of the 
 object. 
 
 But akho' we are not confcious of the motions 
 we pei form, in. order to fit the eyes to the di- 
 ftance of the object, we are confcious of the ef- 
 fort employed in producing thefe motions ; and 
 probably have fome fenfation which accompanies 
 them, to which we give as little attention as to 
 other fenfations. And thus, an effort confciouf- 
 ly exerted, or a fenfation confequent upon that 
 effort, comes to be conjoined with the diftance 
 of the object which gave occafion to it, and by 
 this conjunction becomes a fign of that diftance. 
 Some inftances of this will appear in confidering 
 the means or figns by which we learn to fee the 
 diftance of objects from the eye. In the enu- 
 meration 
 
Sett. 22. Of SEEING. 311 
 
 meratidn of thefe, we agree with Dr. Porterfkld, 
 notwithftanding that diftance from the eye, in 
 his opinion, is perceived originally, but ih our 
 opinion, by experience only. 
 
 In general, when a near object affects the eye 
 in one manner, and the fame object, placed at 
 a greater diftance, affects it in a different man- 
 ner ; thefe various affections of the eye become 
 figns of the correfponding diftances. The means 
 of perceiving diftance by the eye, will therefore 
 be explained, by (hewing in what various ways 
 objects affecl the" eye differently, according to 
 their proximity or diftance. 
 
 1. It is well known, that to fee objects dif- 
 tinctly at various diftances, the form of the eye 
 muft undergo fome change. And Nature hath 
 given us the power of adapting it to near objects, 
 by the contraction of certain mufcles, and to di- 
 ftant objects by the contraction of other mufcles. 
 As to the manner in which this is done, and the 
 mufcular parts employed, anatomifts do not alto- 
 gether agree. The ingenious Dr. Jurin, in his 
 excellent effay on diftinct and indiftinct vifion, 
 feems to have given the moft probable account 
 of this matter ; and to him I refer the reader. 
 
 But whatever be the manner in which this 
 •change of the form of the eye is effected, it is 
 certain that young people have commonly the 
 power of adapting their eyes to all diftances 
 of the object, from fix or feven inches, to fifteen 
 or fixteen feet ; fo as to have perfect and diftinct 
 vifion at any diftance within thefe limits. From 
 U 4 this 
 
3 iz OftheHtJMAN MIND. Chap. VI. 
 
 this it follows, that the effort we confcioufly 
 employ to adapt the eye to any particular di. 
 ftance of objects within thefe limits, will be 
 connected and aflbciated with that diftahce, and 
 will Jjecome a fign of it. When the object is re- 
 moved beyond the fartheft limit of diftinct vifion, 
 it will be feen indiftinctly ; but more or lefs fo, 
 according as its diftance is greater or lefs : fo that 
 the degrees of indiftinctnefs of the object may 
 become the figns of diftances considerably be- 
 yond the fartheft limit of diftinct vifion. 
 
 If we had no other mean but this, of perceiv- 
 ing diftance of vifible obje&s, the moft diftant 
 •would not appear to be above twenty or thirty 
 feet from the eye, and the tops of houfes and 
 trees would feem to touch the clouds j for in 
 that cafe the figns of all greater diftances being 
 the fame, they have the fame fignifkation, and 
 give the fame perception of diftance. 
 
 But it is of more importance to obferve, that 
 becaufe the neareft limit of diftinct vifion in the 
 time of youth, when we learn to perceive di- 
 ftance by the eye, is about fix or feven inches, 
 no object feen diftinctly, ever appears to be 
 nearer than fix or feven inches from the. eye. 
 We can, by art, make a fmall object appear di- 
 ftinct, when it is in reality not above half an 
 inch from the eye; either by ufing a fingle mir 
 crcfcope, or by looking through a fmall pin-hole 
 jn a card. * When, by either of thefe means, ao 
 object is made to appear diftinct, however fmall 
 jt§ diftance is in reality, it feems to he removed 
 
 at 
 
Sea. 22: Of SEEING. 313 
 
 at leaft to the diftance of fix or feven inches, 
 that is, within the limits of diftinct vifion. 
 
 This obfervation is the more important, be- 
 caufe it affords the only reafon we can give why 
 an object is magnified either by a fingle micro- 
 fcope, or by being feen through a pin-hole ; and 
 the only mean by which we can afcertain the 
 degree in which the object will be magnified by 
 either. Thus, if the object is really half an inch 
 diftant from the eye, and appears to be feven 
 inches diftant, its diameter will feem to be en- 
 larged in the fame proportion as its diftance, that 
 is fourteen times. 
 
 2. In order to direct both eyes to an object, 
 the optic axes muft have a greater or lefs inclU 
 nation, according as the object is nearer or more 
 diftant. And altho' we are not confcious of this 
 inclination, yet we are confcious of the effort 
 employed in it. By this mean we perceive fmall 
 djftances more accurately than we could do by 
 the conformation of the eye only. And there- 
 fore we find, that thofe who have loft the fight 
 of one eye, are apt, even within arm's-length, 
 to make miftakes in the diftance of objects, 
 which are eafily avoided by thofe who fee with 
 both eyes. Such miftakes are often difcovered 
 in fnuffing a candle, in threading a needle, or in 
 filling a tea-cup. 
 
 "When a pitture is feen with both eyes, and at no 
 great diftance, the reprefentation appears not fo 
 natural as when it is feen only with one. The in- 
 dention of painting being to deceive the eye, and 
 
 to 
 
3I4 Of the H U M A N M I N D. Chap. VI. 
 to make things appear at different diftances which 
 in reality are upon the fame piece of canvas, 
 this deception is not fo eafily put upon both 
 eyes as upon one ; becaufe we perceive the di- 
 ftance of vifible objects more exactly and deter- 
 minately with two eyes than with one. If the 
 fljading and relief be executed in the beft manner, 
 the picture may have almoft the fame appearance 
 to <Mie eye as the objects themfelves would have, 
 but it cannot have the fame appearance to both. 
 This is not the fault of the artift, but an una- 
 voidable imperfection in the art. And it is ow- 
 ing to what we juft now obferved, that the per- 
 ception we have of the diftance of objects by one 
 eye is more uncertain, and more liable to decep- 
 tion, than that which we have by both* 
 
 The great impediment, and I think the only 
 invincible impediment, to that agreeable decep- 
 tion of the eye which the painter aims at, is the 
 perception which we have of the diftance of 
 vifible objects from the eye, partly by means 
 of the conformation of the eye, but chiefly by 
 means of the inclination of the optic axes. If 
 this perception could be removed, I fee no rea- 
 fon why a picture might not be made fo perfect 
 as to deceive the eye in reality, and to be 
 triiftaken for the original object. Therefore, 
 in order to judge of the merit of a picture,' we 
 Ought, as much as pofllble, to exclude thefe two 
 means of perceiving the diftance of the feveral 
 parts of it. 
 
 In 
 
Sea. 22. Of SEEING. 315 
 
 In order to remove this perception of diftance, 
 the connoiffeurs in painting ufe a method which 
 is very proper. They look at the picture with 
 one eye, through a tube which, excludes the view 
 of all other objects. By this method, the prin- 
 cipal mean whereby we perceive the diftance of 
 the object, to wit, the inclination of the optic 
 axes, is entirely excluded. I would humbly 
 propofe, as an improvement of this method of 
 viewing pictures, that the aperture of the tube 
 next to the eye fhould be very fmall. If it is as 
 fmall as a pin-hole, fo much the better, pro- 
 viding there be light enough to fee the picture 
 dearly. The reafon of this propofal is, that 
 when we look at an object through a fmall aper- 
 ture, it will be feen diftinctly whether the con- 
 formation of the eye be adapted to its diftance 
 or not, and we have no mean left to judge of 
 the diftance, but the light and colouring, which 
 are in the painter's power. If, therefore, the 
 artift performs his part properly, the picture 
 will by this method affect the eye in the fame 
 manner that the object reprefented would do j 
 which is the perfection of this art. 
 
 Altho' this fecond mean of perceiving the 
 diftance of vifible objects be more determinate 
 and exact than the firft, yet it hath its limits, 
 beyond which it can be of no ufe. For when 
 the optic axes directed to an object are fo near- 
 ly parallel, that in directing them to an object 
 yet more diftant, we are not confcious of any 
 new effort, nor have any different fenfation ; 
 
 there 
 
3 i6 OfthcHUMAN MIND. Chap. VI. 
 there our perception of diftance flops ; and as 
 all more diftant objects affect the eye in the fame 
 manner, we perceive them to be at the fame 
 diftance. This is the reafon why the fun, 
 moon, planets, and fixed ftars, when feen not 
 iiear the horizon, appear to be, all at the fame 
 diftance, as if they touched the concave furface 
 of a great fphere. The furface of this celeftial 
 fphere is at that diftance beyond which all ob- 
 jects affect the eye in the fame manner. Why 
 this celeftial vault appears more diftant towards 
 the horizon, than towards the zenith, will after- 
 wards appear. 
 
 3. The colours of objects, according as they 
 are more diftant, become more faint and languid, 
 and are tinged more with the azure of the in- 
 tervening atmofphere : to this we may add, that 
 their minute parts become more indiftinct, and 
 their outline lefs accurately defined. It is by 
 thefe means chiefly, that painters can reprefent 
 objects at very different diftances, upon, the 
 fame canvas. And the diminution of the mag- 
 nitude of an object, would not have the effect 
 of making it appear to be at a great diftance 
 without this degradation of colour, andindif- 
 tinctnefs of the outline, and of the minute 
 parts. If a'painter fhould make a human figure 
 ten times lefs than other human figures that are 
 in the fame piece, having the colours as bright, 
 and the outline and minute parts as accurately 
 defined, it would not have the appearance of a 
 
 man 
 
Seft. 22. Of SEEING. 317 
 
 man at a great diftance, but of a pigmy or Lilli- 
 putian. 
 
 When an objeft hath a known variety of 
 colours, its diftance is more clearly indicated 
 by the gradual dilution of the colours into one 
 another, than when it is of one uniform colour. 
 In the fteeple which ftands before me at a fmall 
 diftance, the joinings of the ftones are clearly 
 perceptible ; the gray colour of the ftone and 
 the white cement are diftinctly limited : when 
 I fee it at a greater diftance, the joinings of the 
 ftones are lefs diftinct, and the colours of the 
 ftone and of the cement begin to dilute into one 
 another : at a diftance ftill greater, the joinings 
 difappear altogether, and the variety of colour 
 vanifhes. 
 
 In an apple-tree which ftands at the diftance 
 of about twelve feet, covered with flowers, I 
 can perceive the figure and the colour of the 
 leaves and petals ; pieces of branches, fome 
 larger, others fmaller, peeping through the in- 
 tervals of the leaves, fome of them enlightened 
 by the fun 's rays, others fhaded; and fome 
 openings of the fky'are perceived through the 
 whole. When I gradually remove from this 
 tree, the appearance, even as to colour, changes 
 every minute. Pirft, the fmaller parts, then 
 the larger, are gradually confounded and mix- 
 ed. The colours of leaves, petals, branches, 
 and fky, are gradually diluted into each other, 
 and the colour of the whole becomes more and 
 more uniform. This change of appearance, cor- 
 
 refponding 
 
3 i8 Of the HUMAN MIND. Chap. VI. 
 
 refponding to the feveral diftances, marks the 
 diftance more exactly than if the whole object 
 had been of one colour . 
 
 Dr. Smith, in his Optics, gives us a very 
 curious obfervation made by Bifhop Berkeley, in 
 his travels through Italy and Sicily. He ob- 
 ferved, That in ^thofe countries, cities and 
 palaces feen at a great diftance, appeared nearer 
 to him by feveral miles than they really were : 
 and he very judieiouGy imputed it to this caufe, 
 That the purity of the Italian and Sicilian air, 
 gave to very diftant objects, that degree of 
 brightness and diftindtnefs, which, in the grofler 
 air of his own country, was to be feen only in 
 thofe that are near. The purity of the Italian 
 air hath been affigned as the reafon why the Ita- 
 lian painters commonly give a more lively colour 
 to the fky, than the Flemifh. Ought they not, 
 for the fame 'reafon, to give lefs degradation of 
 the colours, and lefs indiftindtnefs of the mi- 
 nute parts, in the reprefentation of very diftant 
 objedts ? 
 
 It is very certain, that as in air uncommonly 
 pure, we are apt to think vifible objedls nearer, 
 and lefs than they redly are ; fo, in air uncom- 
 monly foggy, we are apt to think them more 
 diftant and larger than the truth. Walking by 
 the fea-fide in a thick fog, I fee an objedt which 
 feems to me to be a man on horfeback, and at 
 the diftance of about half a mile. My compa- 
 nion, who has better eyes, or is -more accuftom- 
 ed to fee fuch objedls in fuch circumftances, 
 
 aflures 
 
Se& 22; Of SEEING. 319 
 
 aflures me, that it is a fea-gull, and not a man 
 on horfeback* Upon a fecond view, I imme- 
 diately affent to his opinion j and now it appears 
 to me to be a fea-gull, and at the diftance only 
 of feventy or eighty yards. The miftake made 
 on this occafion, and the correction of it, are 
 both fo fudden, that we are at a lofs whether to 
 call them by the name of judgment, or by that of 
 fimfle perception. 
 
 It is not worth while to difpute about names ; 
 but it is evident, that my belief, both firft and 
 laft, was produced rather by figns than by argu- 
 ments ; and that the mind proceeded to the con- 
 clufion in both cafes by habit, and not by ratio- 
 cination. And the procefs of the mind feems 
 to have been this. Firft, Not knowing, or 
 not minding, the effect of a foggy air on the 
 vifible appearance of objects, the object feems 
 to me to have that degradation of colour, and 
 that indiftinctnefe of the outline, which objects 
 have at the diftance of half a mile ; therefore^ 
 from the vifible appearance as a fign, I imme- 
 diately proceed to the belief that the object is 
 half a mile diftant. Then, this diftance, to- 
 gether with the Vifible magnitude, fignify to me 
 the real magnitude, which, fuppofing the di- 
 ftance to be half a mile, muft be equal to that 
 of a man on horfeback v and the figure, con- 
 fidering the indiftinctnefs of the Outline, agrees 
 with that of a man on horfeback. Thus the 
 deception is brought about. But when I am 
 affured that it is a fea-gull, the real magnitude 
 
 5 of 
 
3 2© Of the HUMAN MIND. Chap.VL 
 of a fea-gull, together with the vifible magni- 
 tude presented to the eye, immediately fuggeft 
 the diftance, which in .this cafe cannot be above 
 feventy or eighty yards : the indiftindtnefs of 
 the figure likewife fuggefts the fogginefs of the 
 air as its caufe : and now the whole chain of 
 figns, and things fignified, feems ftronger and 
 better connefted than it was before; the half 
 mile vanifhes to eighty yards ; the man on horfe- 
 back dwindles to a fea-gull j I get a new percep- 
 tion, and wonder how I got the former, or what 
 is become of it ; for it is now fo entirely gone, 
 that I cannot recover it. 
 
 It ought to be obferved, that in order to 
 produce fuch deceptions from the clearnefs or 
 fogginefs of the air, it mult be uncommonly 
 clear, or uncommonly foggy : for we learn from 
 experience, to make allowance for that variety 
 of conftitutions of the air which we have been 
 accuftomed to obferve, and of which we are 
 aware. Bifhop Berkeley therefore* committed 
 a miftake, when he attributed the large ap- 
 pearance of the horizontal moon to the faintnefs 
 of her light, occafioned by its palling through a 
 larger tract of atmofphere : for we are fo much 
 accuftomed to fee the moon in all degrees of 
 faintnefs and brightnefs, from the greateft to 
 the leaft, that we learn to make allowance for 
 it ; and do not imagine her magnitude increafed 
 by the faintnefs of her appearance. Befides, 
 it is certain that the horizontal moon feen 
 through a tube which cuts off the view of the 
 
 inter- 
 
Sect. iz. 6f SEEING. .321 
 
 interjacent ground, and of all terreftrial objects^ 
 lofes all that unufual appearance of magnitude. 
 
 4. We frequently perceive the diftance of 
 objects, by means of intervening or contiguous 
 objects, whofe diftance or magnitude is other- 
 wife known. When I perceive certain fields 
 or trails of ground to lie between me and an 
 object, it is evident that thefe may become figns 
 of its diftance. Arid altho' we have no parti- 
 cular information of the dimenfions of fuch fields 
 or tracts, yet their fimilitude to others which 
 we know, fuggefts their dimenfions. 
 
 We are fo much accuftomed to meafure With 
 our eye the ground which we travel, and to com- 
 pare the judgments of diftances formed by fight, 
 with our experience or information, that we learn 
 by degrees, in this way, to form a more accu- 
 rate judgment of the diftance Of terreftrial ob- 
 jects, than we could do by any of the means be- 
 fore mentioned. An object placed upon the top 
 Of a high building, appears much lefs than wheri 
 placed upon the ground at the fame diftance. 
 When it ftands upon the ground, the intervening 
 tract of ground ferves as a fign of its diftance ; 
 and the diftance, together with the vifible mag- 
 nitude^ ferves as a fign of its real magnitude. But 
 when the object is placed on high, this fign of its 
 diftance is taken away : the remaining figns lead 
 us to place it at a lefs diftance ; and this lefs di-< 
 fiance, together with the vifible magnitude, be- 
 comes a* fign of a lefs real magnitude. 
 
 5£ TheS' 
 
322 Of the HUMAN MIND. Chap. VI. 
 The two firft means we have mentioned, 
 would never of themfelves make a vifible ob- 
 ject appear above a hundred and fifty, or two 
 hundred feet, diftant ; becaufe, beyond that 
 there is no fenfible, change, either of the confor- 
 mation of the eyes, or of the inclination of their 
 axes. The third mean, is but a vague and un- 
 determinate fign, when applied to diftances 
 above two or three hundred feet, unlefs we know 
 the real colour and figure of the object ; and the 
 fifth mean, to be afterwards mentioned, can only 
 be applied to objects which are familiar, or whofe 
 real magnitude is known. Hence it follows, that 
 when unknown objects, upon, or near the fur- 
 face of the earth, are perceived to be at the di- 
 ftance of fome miles, it is always by this fourth 
 mean that we are led to that conclufion. 
 
 Dr. Smith hath obferved, very juftly, that the 
 known diftance of the . terreftrial objefls which 
 terminate our view, makes that part of the fity 
 which is towards the horizon, appear more diftant 
 than that which is towards the zenith. Hence it 
 comes to.pafs, that the apparent figure of the fky 
 is not that of a hemifphere, but rather a lefs feg- 
 ment of a fphere. And hence likewife it comes 
 to pafs, that the diameter of the fun or moon, or 
 the diftance between two fixed ftars, feen con- 
 tiguous to a hill, or to any diftant terreftrial ob- 
 ject, appears much greater than when no fuch ob- 
 ject ftrikes the eye at the, fame time. 
 
 Thefe obfervations have been fufficiently ex- 
 plained and confirmed by Dr. Smith- I beg leave 
 
 to 
 
Sett. 22, Of SEEING. 333 
 
 £0 add, that when the vifible horizon is termi- 
 nated by very diftant objects* the celeftial vault 
 feems to be enlarged in all its dimensions. When 
 j. view it from a confined ftreet or lane, it bears 
 fame proportion to the buildings that furround 
 me : but when I view it from a large plain, ter- 
 minated on all hands by hills which rife one 
 above another, to the diftance of twenty miles 
 from the eye, methinks I fee a new heaven, 
 whofe magnificence declares the greatnefs of its 
 Author* and puts every human edifice out of 
 countenance ; for now the lofty fpires and the 
 gorgeous palaces (brink into nothing before it, 
 and bear no more proportion to the celeftial 
 dome, than their makers bear to its Maker. 
 
 5. There remains another mean by which we 
 perceive the diftarice of vifible objects, aijd that 
 is, the diminution of their 1 vifible or appparent 
 magnitude. By experience I know what figure a 
 man, or any other known abject, makes to my 
 eye, at the diftance of ten feet : I perceive the 
 gradual and proportional diminution of this vifi- 
 ble figure, at the diftance of twenty, forty, a hun* 
 dred feet, and at greater diftances, until it vanilh 
 altogether. Hence a certain vifible magnitude of 
 a known object, becomes the figrt of a certain de* 
 terminate diftance, and carries along with it the 
 conception and belief of that diftance. 
 
 In this procefs of the mind, the fign is not a 
 fenfation ; it is an original perception. We per- 
 ceive the vifible figure and vifible magnitude of 
 the object, by the original powers of vifion , but 
 X 2 the 
 
j«4 Of the HUMAN MIND. Chap.Vf. 
 the vifible figure is ufed only as a fign of the real 
 figure, and the vifible magnitude is ufed only as 
 a fign either of the diftance, or of the real mag- 
 nitude, of the object ; and therefore thefe origi- 
 nal perceptions, like other mere figns, pafs thro* 
 the mind without any attention or reflexion. 
 
 This laft mean of perceiving the diftance of 
 known objects, fcrves to explain fome very re- 
 markable phenomena in optics, which would 
 otherwife appear very my Ilerious. When we view 
 objects of known dimenfions thro' optical glafies, 
 there is no other mean left of determining their 
 diftance, but this. fifth. Hence it follows, that 
 known objects feen thro' glaffes, mull feem to be 
 brought nearer, in proportion to the magnifying 
 power of the glafs, or to be removed to a great- 
 er diftance, in proportion to the diminifhing 
 power of the glafs. 
 
 If a man who had never before feen objects thro?' 
 a telefcope, were told, that the telefcope, which he 
 is about to ufe, magnifies the diameter of the ob- 
 ject ten times-, when he looks thro' this telefcope 
 at a man fix feet high, what would he expect to 
 fee ? Surely he would very naturally expect to 
 fee a giant fixty feet high. But he fees no fuch 
 thing. The man appears no more than fix feet 
 high, and confequently no bigger than he really 
 is ; but he appears ten times nearer than he is. 
 The telefcope indeed magnifies the image of this 
 man upon the retina ten times in diameter, and 
 muft therefore magnify his vifible figure in the 
 fame proportion ; and as we have been accuftom- 
 7 ed 
 
Sett. 22. Of SEEING. 3 z 5 
 
 <ed to fee him of this vifible magnitude when he 
 was ten times nearer than he is prefently, and in 
 mo other cafe ; this vifible magnitude* therefore, 
 fuggeftsthe conception and belief of that diftance 
 of the object with which it hath been always 
 •connected. We have been accuftomed to con^- 
 ceive this amplification of the vifible figure of a 
 known object, only as the effect or fign of its be^ 
 ing brought nearer : and we have annexed a cer- 
 tain determinate diftance to every degree of vi- 
 fible magnitude of the object ; and therefore, any 
 particular degree of vifible -magnitude, whether 
 feen by. the naked eye or by glaffes, brings along 
 with it the conception and belief of the diftance 
 which correfpondsto it. This is the reafon why 
 a telefcope feems not to magnify known obje&s, 
 but to bring them nearer to the eye. 
 
 When we look thro' a pin-hole, or a fingle 
 microfcope, at an object which is half an inch 
 from the eye, the picture of the object upon the 
 retina is notenlarged, but only rendered diftinct ; 
 neither is the vifible figure enlarged: yet the ob*- 
 ject appears to the eye twelve or fourteen times 
 more diftant, and as many times larger in diame- 
 ter, than it really is. Such a telefcope as we have 
 mentioned, amplifies the image on the retina, 
 and the vifible figure of the object, ten times in 
 diameter, and yet makes it feem no bigger, but 
 •only ten times nearer. Thefe appearances had 
 been long obferved by the writers on optics % 
 they tortured their invention to find the caufes of 
 jhem from optical principles \ but in vain : they 
 X j muft 
 
3 s6 Of the H U M A N M 1 N D. Chap. VI. 
 
 muft be refolved into habits of perception, which 
 are acquired by cuftom, but are apt to be mif- 
 taken for original perceptions. The Bifhop of 
 Cloyne firft furnifhed the world with the proper 
 key for opening up thefe myfterious appear- 
 ances •, but he made considerable miftakes in the 
 application of it. Dr. Smith, in his elaborate and 
 judicious treatife of Optics, hath applied it to the 
 apparent diftance of objects feen with glafles, and 
 to the apparent figure of the heavens, with fuch 
 happy fuccefs, that there can be no more doubt 
 about the caufes of thefe phenomena, 
 
 SECT. XXIII. 
 
 Of the figns ujed in other acquired ■perceptions. 
 
 Hp H E diftance of objetts from the eye, is 
 the moft important lefion in vifion. Many 
 others are eafily learned in confequence of it. 
 The diftance of the object, joined with its v'v 
 fible magnitude, is a fign of its real magnitude : 
 and the diftance of the feveral parts of an ob- 
 ject, joined with its vifible figure^ becomes a 
 fign of its real figure. Thus when I look at a 
 globe which ftands before me ; by the original 
 powers of fight I perceive only fomething of a 
 circular form, varioufly coloured. The vifible 
 figure hath no diftance from the eye, no con- 
 vexity, nor hath it three dimenfions ; even its 
 length and breadth are incapable of being mea- 
 fijred by inches, feet, qr other linear meafures. 
 
 But 
 
Sect. 23. Of SEEING. 327 
 
 But when I have learned to perceive the di- 
 ftance of every part of this object from the eye, 
 this perception gives it convexity, and a fpheri- 
 cal figure ; and adds a third dimenfion to that 
 which had but two before. The diflance of 
 the whole object makes me likewife perceive 
 the real magnitude; for being accuftomed to 
 obferve how an inch or a foot of length affects 
 the eye at that diftance, I plainly perceive by 
 my eye the linear dimenfions of the globe, and 
 qan affirm with certainty that its diameter is 
 about one foot and three inches. 
 
 It was fhewn in the feventh fection of this 
 chapter, that the vifible figure of a body may, 
 by mathematical reafoning, be inferred from its 
 real figure, diftance, and pofition, with regard 
 to the eye : in like manner, we may, by mathe- 
 matical reafoning, from the vifible figure, to- 
 gether with the diftance of the feveral parts of it 
 from the eye, infer the" real figure and pofition. 
 But this laft inference is not commonly made by 
 mathematical reafoning, nor indeed by reafoning 
 of any kind, but by cuftom. 
 
 The original appearance which the colour of 
 an object makes to the eye, is a fenfation for 
 which we have no name, becaufe it is ufed merely 
 as a fign, and is never made an object of atten- 
 tion in common life : but this appearance, ac- 
 cording to the different circumftances, fignifiea 
 various things. If a piece of cloth, of one uni- 
 form colour, is laid fo that part of it is in the 
 fun, and part in the fhade ; the appearance of 
 X 4 colour. 
 
S 28 Of the HUM AN MIND. Chap. VI. 
 colour, in thefe different parts, is very different : 
 yet we perceive the colour to be the fame •, we 
 interpret the variety of appearance as a fign of 
 light and fhade, and not as a fign of real diffe- 
 rence in colour. But if the eye could be fo far 
 deceived, as not to perceive the difference of 
 light in the two parts of the cloth, we fhould, 
 in that cafe, interpret the variety of appearance 
 to fignify a variety of colour in the parts of the 
 cloth. 
 
 Again, if we fuppofe a piece of cloth placed 
 as before, but having the fhaded part fo much 
 brighter in the colour, that it gives the fame 
 appearance to the eye as the more enlightened 
 part \ the famenefs of appearance will here be 
 interpreted to fignify a variety of colour, be- 
 caufe we (hall make allowance for the effect of 
 light and fhade. 
 
 When the real colour of an object is known, 
 the appearance of it indicates, in fome circum- 
 ftances the degree of light or fhade ; in others^ 
 the colour of the circumambient bodies, whofe 
 rays are reflected by it ; and in other circum- 
 ftances it indicates the diftance or proximity, of 
 the object, as was obferved in the laft fection ; 
 and by means of thefe, many other things are 
 fuggefted to the mind. Thus, an unufual ap- 
 pearance in the colour of familiar objects, may 
 be the diagnoftic of a difeafe in the fpectatqr. 
 The appearance cf things in my room, may in- 
 dicate funfhine or cloudy weather, the earth co- 
 
 veied 
 
Sea. 23; Of SEEIN 6: 329 
 
 vered with fnow, or blackened with rain. Ic 
 hath been obferved, that the colour of the fky, 
 in a piece of painting, may indicate the country 
 ©f the painter, becaufe the Italian fky is really 
 pf a different colour from the Flemifh. 
 
 It was already obferved, that the original and 
 acquired perceptions which we have by our fen- 
 fes, are the language of nature to man, which, 
 in many refpe&s, hath a great affinity to human 
 languages. The inftances which we have given 
 of acquired perceptions, fuggeft this affinity, 
 that as, in human languages, ambiguities are often 
 found, fo this language of nature in our acquired 
 perceptions is not exempted from them. We 
 have feen, in vifion particularly, that the fame 
 appearance to the eye, may, in different circum- 
 ftances, indicate different things. Therefore, 
 when the circumftances are unknown upon which 
 the interpretation of the figns depends, their 
 meaning mull be ambiguous ; and when «the 
 circumftances are miftaken, the meaning of the 
 figns muft alfb, be miftaken. 
 
 This is the cafe in all the phenomena which 
 we call fallacies of the fenfes; and particular- 
 ly, in thofe which are called fallacies in vifion. 
 The appearance of things to the eye, always cor- 
 refponds to the fixed laws of nature ; therefore, 
 if we fpeak properly, there is no fallacy in the 
 fenfes. Nature always fpeaketh the fame lan- 
 guage, and ufeth the fame figns in the fame cir- 
 cumftances : but we fometimes miftake the 
 meaning of the figns, either through ignorance 
 
 of 
 
33© Ofthe HUMAN MIND. Chap. VI. 
 
 of the laws of nature, or through ignorance of 
 the circumftances which attend the figns. 
 
 To a man unacquainted with the principles 
 of optics, almoft every experiment that is made 
 with the prifm, with the magic lanthorn, with 
 the telefcope, with the microfcope, feems to 
 produce fome fallacy in vifion. Even the ap- 
 pearance of a common mirror, to- one altoge- 
 ther unacquainted with the effects of it, would 
 feem moft remarkably fallacious. For how can 
 a man be more impofed upon, than in feeing 
 that before him which is really behind him ? 
 How can he be more impofed upon, than in be- 
 ing made to fee himfelf feveral yards removed 
 from himfelf? Yet children, even before they 
 can fpeak their mother-tongue, learn not to be 
 deceived by thefe appearances. Thefe, as well 
 as all the other furprifing appearances produced 
 by optical glafles, are a part of the vifual lan- 
 guage ; and, to thofe who underftand the laws 
 of nature concerning light and colours, are in 
 no wife fallacious, but have a diftincl: and true 
 meaning. 
 
 SECT. XXIV. 
 
 Of the analogy between perception and the credit 
 we give to human tejtimpny. 
 
 'Tp H E obje&s of human knowledge are innu- 
 merable, but the channels by which it is 
 conveyed to the mind are few. Among thefe, 
 
 the 
 
5eft. 24. Of SEEING. 331 
 
 the perception of external things by our fenfes, 
 and the informations which we receive upon 
 human teftimony, are not the leaft confiderable : 
 and fo remarkable is the analogy between thefe 
 two, and the analogy between the principles of 
 the mind which are fubfervient to the one and 
 thofe which are fubfervient to the other, that 
 without further apology, we (hall confider them 
 . together. 
 
 In the teftimony of nature given by the 
 fenfes, as well as in human teftimony given by 
 language, things are fignified to us by figns: 
 and in one as well as the other, the mind, 
 either by original principles, or by c-uftom, 
 paffes from the fign to the conception and be- 
 lief of the things fignified. 
 
 We have diftinguimed our perceptions into 
 original and acquired; and language, into na- 
 tural and artificial. Between acquired percep- 
 tion, and artificial language, there is a great 
 analogy ; but ftill a greater between original 
 perception and natural language. 
 
 The figns in original perception are fenfa- 
 tions, of which nature hath given us a great 
 variety, fuited to the variety of the things 
 fignified by them. Nature hath eftablifhed a 
 real connection between the figns and the things 
 fignified; and nature hath alfo taught us the 
 interpretation of the figns ; fo that, previous to 
 experience, the fign fuggefts the thing fignified, 
 j»nd creates the belief of it. 
 
 The 
 
33 2 Of the HUMAN MIND. Chap. VI. 
 
 The figns in natural language are features of 
 the face, geftures of the body, and modulations 
 of the voice ; the variety of which is fuited to 
 the Variety of the things fignified by them. Na- 
 ture hath eftablifhed a real connection between 
 thefe figns, and the thoughts and difpofitions 
 of the mind which are fignified by them ; and 
 nature hath taught us the interpretation of thefe 
 figns •, fo that, previous to experience, the figns 
 fuggeft the thing fignified, and creates the belief 
 of it. 
 
 A man in cpmpany, without doing good or 
 evil, without uttering an articulate found, may 
 behaVe himfelf gracefully, civilly, politely ; or, 
 on the contrary, meanly, rudely, and imperti- 
 nently. We fee the" difpofitions of his mind, 
 by their natural figns in his countenance and 
 behaviour, in the fame manner as we perceive 
 the figure and other qualities of bodies by the 
 fenfations which nature hath connected with 
 them. 
 
 The figns in the natural language of the hu- 
 man countenance and behaviour, as well as the 
 figns in our original perceptions, have the fame 
 fignification in all climates and in all nations ; 
 and the fkill of interpreting them is not acqui, 
 red, but innate. 
 
 In acquired perception, the figns are either 
 fenfations, or things which we perceive by 
 means of fenfations. The connection between 
 the fign, and the thing fignified, is eflablifhed 
 by nature : and we difcover. this connexion by 
 
 experience ; 
 
Sea. 24.'- Of SEEING. 333 
 
 experience; but not without the aid of our 
 original perceptions, or of thofe which we have 
 already acquired. After this connection is dis- 
 covered, the fign, in like manner as in original 
 perception, always fuggefts the things Signified, 
 and creates the belief of it. 
 
 In artificial language, the figns are articulate 
 founds, whofe connection with the things figni- 
 fied by them is eflablifhed by the will of men : 
 and in learning our mother-tongue, we difcover 
 this connection by experience ; but not without 
 the aid of natural language, or of what we had 
 before attained of artificial language. And after 
 this connection is difcovered, the fign, as in na- 
 tural language, always fuggefts the thing figni- 
 fied, and creates the belie# of it. 
 
 Our original perceptions are few, compared 
 with the acquired ; but without the former, we 
 could not poffibly attain the latter. In like man- 
 ner, natural language is fcanty, compared with 
 artificial ; but without the former, we could not 
 poffibly attain the latter. 
 
 Our original perceptions, as well as the na- 
 tural language of human features and geftures, 
 muft be refolved into particular principles of the 
 human conftitution. Thus, it is by one parti- 
 cular principle of our conftitution, that certain 
 features exprefs anger; and by another parti- 
 cular principle, that certain features exprefs 
 benevolence. It is in like manner, by one par- 
 ticular principle of our conftitution, that a cer- 
 tain fenfauon fignifies hardncfs -in the body 
 
 which 
 
S3 4 Of the H U M A N M I N D. Chap. VL 
 ■which I handle ; and it is by another particular 
 principle, that a certain fenfation fignifies rfiotion 
 in that body. 
 
 But our acquired perceptions, and the infof* 
 mation we receive by means of artificial lan- 
 guage, mud be refolved into general principles 
 of the human conftitution. When a painter 
 perceives, that this picture is the work of Ra- 
 phael, that the work of Titian ; a jeweller* that 
 this is a true diamond, that a counterfeit ; a 
 failor, that this is a fhip of fivd hundred ton* 
 that of four hundred : thefe different acquired 
 perceptions are produced by the fame general 
 principles of the human mind, which have a dif* 
 ferent operation in the fame perfon according as 
 they are variously applied, and in different per- 
 fons according to the diverfity of their educa- 
 tion and manner of life. In like manner, when 
 certain articulate founds convey to my mind the 
 knowledge of the battle of Pharfalia, and others* 
 the knowledge of the battle of Poltowa; when 
 a Frenchman and an Englifhman receive the 
 fame information by different articulate founds; 
 the figns. ufed in thefe different cafes, produce 
 the knowledge and belief of the things, fignifled, 
 by means of the fame general principles of the 
 human conftitution. 
 
 Now, if we compare the general principles 
 of our conftitution, which fit us for receiving 
 information from our fellow- creatures by lan- 
 guage, with the general principles which fit us 
 for acquiring the perception of things- by our 
 
 fenfes, 
 
Seft. 24. Of SEEING. ^5 
 
 fenfes, we lhall find them to be very fimilar in 
 their nature and manner of operation. 
 
 When we begin to learn our mother-tongue, . 
 we perceive by the help of natural language, 
 that they who fpeak to us, ufe certain founds to 
 exprefs certain things: we imitate the fame 
 founds when we would exprefs the fame things, 
 and find that we are underftood. 
 
 But here a difficulty occurs which merits our 
 attention, becaufe the folution of it leads to 
 fome original principles of the human mind, • 
 which are of great importance, and of very ex- 
 tenfive influence. We know by experience, 
 that men have ufed fuch words to exprefs fuch 
 things. But all experience is of the paft, and 
 can, of itfelf, give no notion or belief of what 
 is future. How come we then to believe, and to 
 rely upon it with affurance, that men who have 
 it in their power to do otherwife, will continue 
 to ufe the fame words when they think the fame 
 things ? Whence comes this knowledge and be- 
 lief, this forefight we ought rather to call it, 
 of the future and voluntary actions of our fel- 
 low-creatures ? Have they promifed that they 
 will never impofe upon us by equivocation or 
 falfehood ? No, they have not. And if they 
 had, this would not folve the difficulty : for 
 fuch promife muft be expreffed by words, or by 
 other figns ; and before we can rely upon it, we 
 muft be afiured that they put the ufual mean- 
 ing upon the figns which exprefs that promife. 
 No man of common fenfe ever thought of ta- 
 king 
 
2 j6 Of the H UM A N MIND. Chap. VI. 
 
 king a man's own word for his honefty ; and it is 
 evident that we take his veracity for granted, 
 when we lay any ftrefs upon his word or pro- 
 mife. I might add, that this reliance upon the 
 declarations and teftimony of men, is found in 
 children long before they know what a pro- 
 mife is. 
 
 There is therefore in the human mind art 
 early anticipation, neither derived from expe- 
 rience, nor from reafon, nor from any compact 
 or promife, that our fellow-creatures will ufe 
 the fame figns in language, when they have the 
 fame fentiments. 
 
 This is, in reality, a kind of preference of 
 human acf ions ; and it feems to me to be an 
 original principle of .-the human conftitution, 
 without which we fhould be incapable of lan- 
 guage, and confequently incapable of inftrudtion. 
 
 The wife and beneficent Author of nature* 
 who intended that we mould be focial creatures, 
 and that we fhould receive the greateft andmoft 
 important part of our knowledge by the infor- 
 mation of others, hath, for thefe pufpofes, im- 
 planted in our natures two principles that tally 
 with each other. 
 
 The firfl of thefe principles is, a propenfity to 1 
 fpeak truth, and to ufe the figns of language, fo 
 as to convey our real fentiments. This principle 
 has a powerful operation, even in the greatefl 
 liars ; for where they lie once, they fpeak truth 
 a hundred times. Truth is always uppermoft,' 
 and is the natural iffue of the mind.- It requires 
 
 no- 1 
 
Seft. 24. Of S E E I N G. 337 
 
 no art or training, no Inducement or temptation, 
 but only that we yield to a natural impulfe. Ly- 
 ing, on the contrary, is doing violence to our na- 
 ture j and is never pra&ifed, even by the worft 
 men, without fome temptation. Speaking truth 
 is like ufing our natural food, which we would 
 do from appetite, altho' it anfwered no end; but 
 lying is like taking phyfic, which is naufeous to 
 the tafte, and which no man takes but for fome 
 end which he cannot otherwife attain. 
 
 If it mould be objected, That men may be in- 
 fluenced by moral or political confiderations to 
 fpeak truth, and therefore, that their doing fo, 
 is no proof of fuch an original principle as we 
 have mentioned ; I anfwer, firft, That moral or 
 political confiderations can have no influence, 
 until we arrive at years of understanding and 
 reflexion ; and it is certain from experience, 
 that children keep to truth invariably, before 
 they are capable of being influenced by fuch con- 
 fiderations. Secondly, When we are influenced 
 by moral or political confiderations, we muft be 
 confcious of that influence, and capable of per- 
 ceiving it upon reflexion. Now, when I reflect 
 upon my aclions moft attentively, I am not con- 
 fcious that in fpeaking truth, I am influenced on 
 ordinary occafions by any motive moral or poli- 
 tical. I find, that truth is always at the door of 
 my lips, and goes forth fpontanecufiy, if not held 
 back. It requires neither good nor bad intention 
 to bring it forth, but only that I be artlefs an$ 
 Undefigning. There may indeed be temptations 
 Y to 
 
$38 Of the HUMAN MIND. Chap. VI. 
 
 to falfehood, which would be too ftrong for the 
 natural principle of veracity, unaided by princi- 
 ples of honour or virtue •, but where there is no 
 fuch temptation, we fpeak truth by inftinct ; and 
 this inftinct is the principle I have been explain- 
 ing. 
 
 By this inftinct, a real connection is formed 
 between our words and our thoughts, and there- 
 by the former become fit to be figns of the lat- 
 ter, which they could not otherwife be. And al- 
 tho' this connection is broken in every inftance 
 of lying and equivocation, yet thefe inftances be- 
 ing comparatively few, the authority of human 
 teftimony is only weakened by them, but not 
 deftroyed. 
 
 Another original principle implanted in us by 
 the Supreme Being, is a difpofition to confide in 
 the veracity of others, and to believe what they 
 tell us. This is the counter-part to the former » 
 and as that may be called the principle of veraci- 
 ty, we fhall, for want of a more proper name, call; 
 this the principle of credulity-. It is unlimited in 
 children, until they meet with inftances of deceit 
 arid falfehood : and it retains a very considerable 
 degree of ftrength through life. 
 
 If nature had left the mind of the fpeaker in 
 aauilibrio, without any inclination to the fide of 
 truth more than to that of falfehood ; children 
 would lie as often as they fpeak truth, until rea- 
 fon was fp far ripened, as to fuggeft the impru- 
 dence of lying, or confcience, as to fuggeft its- 
 immorality. And if nature had kft the mind 
 
 of 
 
Sett. 24. Of S E E I N G. 339 
 
 of the hearer in aquilibrio, without any inclina- 
 tion to the fide of belief more than to that of 
 difbelief, we mould take no man's word until we 
 had pofitive evidence that he fpoke truth. His 
 .teftimony would, in this cafe, have no more au- 
 thority than his dreams ; which may be true or 
 falfe, but no man is difpofed to believe them, on 
 this account, that they were dreamed. It is evi- 
 dent, that, in the matter of teftimony, the balance 
 of human judgment is by nature inclined to the 
 fideof belief; and turns to that fideof itfelf, when 
 there is nothing put into the oppofite fcale. If 
 it was not fo, no propofition that is uttered in 
 difcourfe would be believed, until it was exami- 
 ned and tried by reafon ; and moft men would be 
 unable to find reafons for believingthethoufandth 
 part of what is told them. Such diftruft and in- 
 credulity would deprive us of the greateft bene- 
 fits of fociety, and place us in a worfe condition 
 than that of favages. 
 
 Children, on this fuppofition, would be abfb- 
 lutely incredulous •, and therefore abfolutely in- 
 capable of inftrudtion : thofe who had little 
 knowledge of human life, and of the manners 
 and characters of men, would be in the next de- 
 gree incredulous : and the moft credulous men 
 would be thofe of greateft experience, and of the 
 deepeft penetration ; becaufe, in many cafes, they 
 would be able to find good reafons for believing 
 teftimony, which the weak and the ignorant 
 could not difcover. 
 
 Y 2 In 
 
34Q Of the H OMAN MIND. Chap. Vf, 
 
 In a word, if credulity were the effect of rea- 
 soning and experience, it muft grow up and ga- 
 ther ftrength, in the fame proportion as reafon 
 and experience do. But if it is the gift of nature, 
 it will be ftrongeft in childhood, and limited and 
 reftrained by experience ; and the moft fuperfi- 
 cial view of human life fhows, that the laft is 
 really the cafe, and not the firft. 
 
 It is the intention of nature, that We fhould be 
 carried in arms before we are able to walk upon 
 our legs; and it is likewife the intention of na- 
 ture, that our belief fhould be guided by the au- 
 thority and reafon of others, before it can be 
 guided by our own reafon. The weaknefs of the 
 infant, and the natural affection of the mother, 
 plainly indicate the former ; and the natural cre- 
 dulity of youth, and authority of age, as plainly 
 indicate the latter. The infant, by proper nur- 
 fing and care, acquires ftrength to walk without 
 fupport. Reafon hath likewife her infancy, when 
 fhe muft be carried in arms : then fhe leans en- 
 tirely upon authority, by natural inftinct, as if 
 fiie was confcious of her own weaknefs ; and 
 without this fupport, fhe becomes vertiginous. 
 When brought to maturity by properculture, fhe 
 begins to feel her own ftrength, and leans lefs 
 upon the reafon of others ; fhe learns to fufpe& 
 teftimony in fome cafes, and to difbelieve it in 
 others •, and fets bounds to that authority to 
 which fhe was at firft entirety fubject. But ftill, 
 tathe end of life, fhe finds a neceflity of borrow- 
 ing light from teftimony, where fhe has none 
 
 within 
 
Sea. 24. Of S E E I N G. 34 i 
 
 within herfelf, and of learning in fome degree 
 upon the reafon of others, where fhe is confcious 
 of her own imbecillity. 
 
 And as in many inftances, Reafon, even in her 
 maturity, borrows aid from teftimony -, fo in 
 others fhe mutually gives aid to it, and ftrength- 
 ens its authority. For as we find good reafon to 
 reject teftimony in fome cafes, fo in others we 
 find good reafon to rely upon it with perfect fe- 
 curity, in our moft important concerns^ The 
 character, the number, and the difintereftednefs 
 ofwitneffes, the impoflibility of collufion, and 
 the incredibility of theirconcurring in their tefti- 
 1 mony without collufion, may give an irrefiftible 
 ftrength to teftimony, compared to which its 
 native and intrinfic authority is very inconfider- 
 able. 
 
 Having now conftdered .the general principles 
 of the human mind which fit us for receiving 
 information from our fellow-creatures-, by the 
 means of language ; let us next confider the ge- 
 neral principles which fit us for receiving the in- 
 formation of nature by our acquired perceptions. 
 
 Jt is undeniable, and indc£d is acknowledged 
 by all, that when we have found two things to 
 have been conftantly conjoined in the courfe of 
 nature, the appearance of one of them is immedi- 
 ately followed by the conception and belief of 
 the other. The former becomes a natural fign of 
 the latter-, and the knowledge of their conftanc 
 conjunction in tims paft, whether got by expe- 
 dience or otherwife, is fufficient to make us rely 
 Y 3 with 
 
342 Of the HUMAN MIND. Chap. VI. 
 with afTurance upon the continuance of that con- 
 junction. 
 
 This procefs of the human mind is fo familiar, 
 that we never think of inquiring into the princi- 
 ples upon which it is founded. We are apt to 
 conceive it as a felf-evident truth, that what is 
 to come muft be fimilar to what is paft. Thus 
 if a certain degree of cold freezes water to-day, 
 and has been known to do fo in all time paft, 
 we have no doubt but the fame degree of- cold 
 will freeze water to-morrow, or a year hence. 
 That this is a truth which all men believe as foon 
 as they underftand it, 1 readily admit ; but the 
 queftion is, Whence does its evidence arife ? Not 
 from comparing the ideas, furely. For when I 
 compare the idea of cold with that of water hard- 
 ened into a tranfparent folid body, I can perceive 
 no connection between them : no man can (how 
 the one to be the neceflary effect of the other : 
 no man can give a fhadow of reafon why nature 
 hath conjoined them. But do we not learn their 
 conjunction from experience ? True j experience 
 informs us that they have been conjoined in time 
 paft : but no man ever had any experience of 
 what is future : and this is the very queftion to 
 be refolved, How we come to believe that the/«- 
 ture will be like the paft ? .Hath the Author of 
 nature promifed this ? Or were we admitted to 
 his council, when he eftablifhed the prefent laws 
 of nature, and determined the time of their con- 
 tinuance ? No, furely. Indeed, if we believe that 
 there is a wife and good Author of nature, we 
 4 may 
 
5e&. 24. Of S E E I N G. 343 
 
 may fee a good reafon, why he mould continue 
 the fame laws of nature, and the fame connec- 
 tions of things, for a long time : becaufe, if he 
 did otherwife, we could learn nothing from what 
 is paft, and all our experience would be of no ufe 
 to us. But tho' this confideration, when we come 
 to the ufe of reafon, may confirm our belief of 
 the continuance of the prefent courfe of nature, 
 it is certain that it did not give rife to this be- 
 lief; for children and idiots have this belief as 
 foon as they know that fire will burn them. It 
 muft therefore be the effect of inftinft, not of 
 reafon. 
 
 The wife Author of our nature intended, that 
 a great and necefiary part of our knowledge 
 mould be derived from experience, before we 
 are capable of reafoning, and he hath provided 
 means perfedlly adequate to this intention. For, 
 firft, He governs nature by fixed laws, fo that 
 we find innumerable connections of things which 
 continue from age to age. Without this liabi- 
 lity of the courfe of nature, there could be no 
 experience ; or, it would be a falfe guide, and 
 lead us into error and mifchief. If there were 
 not a principle of veracity in the human mind, 
 mens words would not befigns of their thoughts : 
 and if there were no regularity in the courfe of 
 nature, rfo one thing could be a natural fign of 
 another. Secondly, he hath implanted in human 
 minds an original principle by which we believe 
 and expect the continuance of the courfe of na- 
 ture, and the continuance of thofe connections 
 Y 4 which 
 
344 Of the H U M A N M I N D. Chap. VI. 
 which we have obferved in time paft. It is by 
 this general principle of our nature, that when 
 two things have been found connected in time 
 paft, the appearance of the one produces the be- 
 lief of the other. 
 
 I think the ingenious author of the Treatife 
 ef human nature firft obferved, That our belief 
 of the continuance of the laws of nature cannot 
 be founded either upon knowledge or probabi- 
 lity : but, far from conceiving it to be an origi- 
 nal principle of the mind, he endeavours to ac- 
 count for it from his favourite hypothefis, That 
 belief is nothing but a certain degree, of vivacity 
 in the idea of the thing believed. I made a re- 
 mark upon this curious hypothefis in the fecond 
 chapter, and ftiall now make another. 
 
 The belief which we have in perception, is a 
 belief of the prefent exiftence of the objeftj 
 that which we have in memory, is a belief of 
 its paft exiftence,; the belief of which we are 
 now fpeaking, is a belief of its future exiftence, 
 and in imagination there is no belief at all. Now, 
 I would gladly know of this author, how one de- 
 gree of vivacity fixes the exiftence of the objecT: 
 to the prefent moment ; another carries it back 
 to time paft ; a third, taking a contrary direction, 
 carries it into futurity ; and a fourth carries it 
 out of exiftence altogether." Suppofe, for in- 
 ftance, that I fee the fun rifing out of the fea ; I 
 remember to have feen him rife yefterday ; I be- 
 lieve he will rife to-morrow near the fame place ; 
 I can likewife imagine him rifing in that place^ 
 
 with'* 
 
Se&. 24. Of SEEING. 345 
 
 without any belief at all. Now, according to this 
 fceptical hypothefis, this perception, this memory, 
 this foreknowledge, and this imagination, are all 
 the fame idea, diverfifiedonly by different degrees 
 of vivacity. The perception of the fun rifing, is 
 the mod lively idea j the memory of his rifing 
 yefterday, is the fame idea a little more faint; 
 the belief of his rifing to-morrow, is the fame 
 idea yet fainter •, and the imagination of his ri- 
 fing, isftill the fame idea, but fainteftof all. One 
 is apt to think, that this idea might gradually 
 pafs thro' all poflible degrees of vivacity, without 
 ftirring out of its place. But if we think fo, we 
 deceive ourfelves ; for no fooner does it begin to 
 grow languid, than it moves backward into time 
 paft. Suppofing this to be granted, we expect at 
 leaft that as it moves backward by the decay of 
 its vivacity, the more that vivacity decays, it 
 will go back the farther, until it remove quite 
 out of fight. But here we are deceived again ; 
 for there is a certain period of this declining vi- 
 vacity, when, as if it had met an elaftic obftacle 
 , in its motion backward, it fuddenly rebounds 
 from the paft to the future, without taking the 
 prefent in its way. And now having got into 
 the regions of futurity, we are apt to think, 
 that it has room enough to fpend all its remain- 
 ing vigour : but ftill we are deceived ; for, by 
 another fprightly bound, it mounts up into the 
 a/iry region of imagination. So that ideas, in 
 the gradual declenfion of their vivacity, feem 
 
 to 
 
34 6 Of the HUMAN MIND. Chap. VI. 
 to imitate the inflexion of verbs in grammar. 
 They begin with the prefent, and proceed in or- 
 der to the preterite, the future, and the indefi- 
 nite. This article of the fceptical creed is in- 
 deed fo full of myftery, on whatever fide we 
 view it, that they who hold that creed, are very 
 injurioufly charged with incredulity : for to me 
 it appears to require as much faith as that of St. 
 Athanafius. 
 
 However, we agree with the author of the 
 Vreatife of human nature in this, That our belief 
 of the continuance of nature's laws is not deri- 
 ved from reafon. It is an inftinftive prefcience 
 of the operations of nature, very like to that pre- 
 fcience of human actions which makes us rely 
 upon the teftimony of our fellow-creatures ; and 
 as, without the latter, we mould be incapable of 
 receiving information from men by language ; 
 fo, without the former, we mould be incapable of 
 receiving the information of nature by means of 
 experience. 
 
 All our knowledge of nature, beyond our 
 original perceptions, is got by experience, and 
 confifts in the interpretation of natural figns. 
 The conftancy of nature's laws, connects the 
 fign with the thing fignified, and, by the natu- 
 ral principle juft now explained, we rely upon 
 the continuance of the connexions which expe- 
 rience hath difcovered ; and thus the appearance 
 of the fign, is followed by the belief of the 
 thing fignified. 
 
 Upon 
 
Seft. 24. Of S E E IN G. 547 
 
 Upon this principle of our conftitution, not 
 only acquired perception, but all indu&ive rea- 
 foning, and all our reafoning from analogy, is 
 grounded : and therefore, for want of another 
 name, we fhall beg leave to call it the induftive 
 principle. It is from the force of this principle, 
 that we immediately affent to that axiom upon 
 which all our knowledge of nature is built, That 
 effects of the fame kind mult have the fame 
 caufe. For effefts and caufes, in the operations 
 of nature, mean nothing but figns, and the 
 things fignified by them. We perceive no pro- 
 per caufality or efficiency in any natural eaufe ; 
 but only a connection eftablifhed by the courfe 
 of nature between it and what is called its effecl:. 
 Antecedently to all reafoning, we have, by our 
 conftitution, an anticipation, that there is a 
 fixed and fteady courfe of nature ; and we have 
 an eager defire to difcover this courfe of nature. 
 "We attend to every conjunction of things which 
 prefents itfelf, and expect the continuance of 
 that conjunction. And when fuch a conjunction 
 lias been often obferved, we conceive the things 
 to be naturally conne&ed, and the appearance 
 of One, without any reafoning or reflexion, car- 
 ries along with it the belief of the other. 
 
 If any reader fhould imagine that the induc- 
 tive principle may be refolved into what philo- 
 fophers ufually call the affociation of ideas, let 
 him obferve, that, by this principle, natural figns 
 are not affociated with the idea only, but with 
 the belief of the things fignified. Now, this 
 
 can 
 
348 OftheHUMAN MIND. Chap. VI. 
 
 can with no propriety be called an aflbciation 
 of ideas, unlefs ideas and belief be one and the 
 fame thing. A child has found the prick of a 
 pin conjoined with pain ; hence he believes, and 
 knows, that thefe things are naturally connected -, 
 he knows that the one will always follow the 
 other. If any man will call this only an aflbcia- 
 tion of ideas, I difpute not about words, but I 
 think he fpeaks very improperly. For if we ex- 
 prefs it in plain Englilh, it is a prefcience, that 
 things which he hath found conjoined in time 
 paft, will be conjoined in time to come. And 
 this prefcience is not the effect of reafoning, but 
 of an original principle of human nature, which 
 I have called the induSive principle. ' 
 
 This principle, like that of credulity, is un- 
 limited in infancy, and gradually reftrained and 
 regulated as we grow up. It leads us often into 
 miftaker, but is of infinite advantage upon the 
 v;hole. By it the child once burnt fhuns the 
 fire; by it, he likewife runs away from the 
 furgeon by whom he was inoculated. It is bet- 
 ter that he mould do the laft, than that he mould 
 not do the firft. 
 
 But the miftakes we are led into by thefe 
 two natural principles, are of a different kind. , 
 Men fometimes lead us into miftakes, when we 
 perfectly underftand their language, by fpeaking 
 lies. But .Nature never miQeads us in this way; 
 her language is always true ; and it is only by 
 Kiifinterpreting it that we fall into error. There 
 KUift be many accidental conjunctions of things, 
 
 as 
 
Scft. 24. Of S E £ I N G. 349 
 
 as well as natural conne&ions ; and the former 
 are apt to be miftaken for the latter. Thus, 
 in the inftance above mentioned, the child con- 
 nected the pain of inoculation with the furgeon ; 
 whereas it was really connected with the incifion 
 only. Philofophers, and men of fcience, are 
 not exempted from fuch miftakes-, indeed all 
 falfe reafoning in philofophy is owing to them : 
 it is drawn from experience and analogy, as 
 well as juft reafoning, otherwife it could have 
 no verifimilitude : but the one is an unfkilful 
 and rafh, the other, a juft and legitimate in- 
 terpretation of natural figns. If a child, or a 
 man of common understanding, were put to in- 
 terpret a book of fcience, wrote in his mother- 
 tongue, how many blunders and miftakes would 
 he be apt to fall into ? Yet he knows as much of 
 this language as is neceffary for his manner of 
 life. 
 
 The language of nature is the univerfal ftudy; 
 and the ftudents are of different clafTes. Brutes, 
 idiots, and children, employ themfelves in this 
 ftudy, and owe to it all their acquired percep- 
 tions. Men of common understanding make a 
 greater progrefs, and learn, by a fmall degree 
 of refle&ion, many things of which children are 
 
 ignorant. 
 
 Philofophers fill up the higheft form in this 
 fchool, and are critics in the language of na- 
 ture. All thefe different clafles have one teacher, 
 Experience, enlightened- by the indudive prin- 
 ciple. Take- away the light of this inductive 
 
 principle, 
 
35 o Ofth&HUMAN MIND. Chap. VI. 
 
 principle, and Experience is as blind as a mole : 
 Ihe may indeed feel what is prefent, and whafc 
 immediately touches her; but fhe fees nothing 
 that is either before or behind, upon the right 
 hand or upon the left, future or paft. 
 
 The rules of indudtive reafoning, or of a juffc 
 interpretation of nature, as well as the fallacies 
 by which we are apt to mifinterpret her lan- 
 guage, have been, with wonderful fagacity, de- 
 lineated by the great genius of Lord Bacon : fo 
 that his Novum organum may juftly be called a 
 grammar of the language of nature. It adds 
 greatly to the merit of this work, and atones 
 for its defects, that, at the time it was written, 
 the world had not feen any tolerable model of 
 inductive reafoning from which the rules of it 
 might be copied. The arts of poetry and elo- 
 quence were grown up to perfection when Ari- 
 ftotle defcribed them ; but the art of interpret- 
 ing nature was yet in embryo when Bacon de- 
 lineated its manly features and proportions. Ari- 
 ftotle drew his rules, from the beft models of 
 thofe arts that have yet appeared ; but the beft 
 models of inductive reafoning that have yet ap- 
 peared, which I take to be the third book of 
 the Principia and the Optics of Newton, were 
 drawn from Bacon's rules. The purpofe of all 
 thofe rules, is to teach us to diftinguiih feeming 
 or apparent connections of' things in the courfe 
 of nature, from fuch as are real. 
 
 They that are unfkilful in inductive reafon--- 
 ing, are moje apt to fail into error in their 
 
 reafomngs 
 
Se6t. 24. Of S E E I N G. 351 
 
 reafonings from the phaenomena of nature, than 
 in their acquired perceptions -, becaufe we often 
 reafon from a few inftances, and thereby are 
 apt to miftake accidental conjunctions of things 
 for natural connexions : but that habit of paf- 
 fing, without reafoning, from the fign to the 
 thing fignified, which conftitutes acquired per- 
 ception, mul be learned by many inftances or 
 experiments ; and the number of experiments 
 ferves to disjoin thofe things which have been 
 accidentally conjoined, as well as to confirm our 
 belief of natural connections. 
 
 From the time that children begin to ufe 
 their hands, natufe directs them to handle every 
 thing over and over, to look at it while they 
 handle it, and to put it in various positions* 
 and at various diftances from the eye. We 
 are apt to excufe this as a childifh diverfion r 
 becaufe they muft be doing fomething, and have 
 not reafon to entertain themfeives in a more 
 manly way. But if we think more juftly, we 
 fhall find, that they are engaged in the moft 
 ferious and important ftudy ; and if they had 
 all the reafon of a philofopher, they could not 
 be more properly employed. For it is this 
 childifh employment that enables them to make 
 the proper ufe of their eyes. They are there- 
 by every day acquiring habits of perception, 
 which are of greater importance than any thing 
 we can teach them. The original perceptions 
 which Nature gave them are few, and infufB- 
 cient for the purpofea of life j, and therefore fhe 
 
 made 
 
352 OftheHUMAN MIND. Chap.V?. 
 made then* capable of acquiring many more per- 
 ceptions by habit. And to complete her work, 
 fhe hath given them an unwearied afiiduiry in 
 applying to the exercifes by which thofe percep- 
 tions are acquired. 
 
 This is the education which Nature gives 
 to her children. And fince we have fallen upon 
 this fubjefr, we may add, that another part of 
 Nature's education is, That, by the courfe of 
 things, children mud often exert all their muf- 
 cular force, and employ all their ingenuity, in 
 qrder to gratify their curiofity, and fatisfy their 
 little appetites. What they defire is only to be 
 obtained at the expence of labour and patience, 
 and many difappointments. By the exercife of 
 body and mind necelTary for fatisfying their de- 
 fires, they acquire agility, ftrength, and dex- 
 terity in their motions, as well as health and 
 vigour to their conftitutions ; they learn pa- 
 tience and perfeverance ; they learn to bear 
 pain without dejection, and difappointment with- 
 out defpondence. The education of Nature 
 is moft perfect in favages, who have no other 
 tutor: and we fee, that, in the quicknefs of all 
 their fenfes, in the agility of their motions, in 
 the hardinefs of their conftitutions, and in the 
 ftrength of their minds to bear hunger, thirft, . 
 pain, and difappointment, they commonly far 
 exceed the civilized. A moft ingenious writer, 
 on this account, feems to prefer the favage life 
 to that of fociety. But the education of Nature 
 could never of itfelf produce a Rouffeau. It is 
 
 the 
 
Seft. 24. Of SEEING. 353 
 
 the intention of nature, that human education 
 Ihould be joined to her inftitution, in order to 
 form the man. And me hath fitted us for hu- 
 man education, by the natural principles of imi- 
 tation and credulity, which difcover themfelves 
 almoft in infancy, as well aS by others which are 
 of later growth. 
 
 When the education which we receive from 
 men, does not give fcope to the education of 
 Nature, it is wrong directed ; it tends to hurt 
 our faculties of perception, and to enervate both 
 the body and mind. Nature hath her way of 
 fearing men, as fhe hath of curing their dif- 
 eafes. The art of medicine is to follow Nature* 
 to imitate and to affift her in the cure of difea- 
 fes; and the art of education is to follow Na- 
 ture, to affiit and to imitate her in her way of 
 rearing men. The ancient Baleares followed 
 Nature in the manner of teaching their children 
 to be good archers, when they hang their din- 
 ner aloft by a thread, and left the younkers to 
 bring it down by their fkiil in archery. 
 
 The education of Nature, without any more 
 human care than is necefiary to preferve life, 
 makes a perfect favage* Human education, join- 
 ed to that of Nature, may make a good citizen* 
 a fkilful artifan, or a well-bred man. But Rea- 
 ,fon and Reflection muft fuperadd their tutory, 
 in order to produce a 'Roufleauy a Bacon, or a 
 Newton. ' 
 
 Notwithftanding the innumerable errors com- 
 mitted in human education, there is hardly any 
 
 Z education 
 
3 54 Of the H U M A N M I N D. Chap. VI. 
 education fo bad, as to be worfe than none. And 
 I apprehend, that if even Roufleau were to 
 chufe whether to educate a fon among the 
 French, the Italians, the Chinefe, or among the 
 Efkimaux, he would not give the preference to 
 the laft. 
 
 When reafon is properly employed, {he will 
 confirm the documents of Nature, which are 
 always true and wholefome ; fhe will diftingurlh, 
 in the documents of human education, the good 
 from the bad, rejecting the laft with modefty, 
 and adhering to the firft with reverence. 
 
 Moil men continue all their days to be juft 
 what Nature and human education made them. 
 Their manners, their opinions, their virtues, 
 and their vices, are all got by habit, imitation, 
 and inftruftion ; and Reafon has little or no fhare 
 in forming them. 
 
t 355 j 
 CHAP. VIL 
 
 CONCLUSION. 
 
 Containing Reflections- upon the opinions 
 of philofophers on ,this fubjeit. 
 
 TH E R E are two ways in which men may- 
 form their notions and opinions concern- 
 ing the mind, and concerning its powers and 
 operations. The firft is the only way that leads 
 to truth ; but it is narrow and rugged, and few 
 have entered upon it. The fecond is broad and 
 fmooth, and hath been much beaten, not only 
 by the vulgar, but even by philofophers : it is 
 fufficient for common life, and is well adapted 
 to the purpofes of the poet and orator •„ but, in 
 philofophical difquifitions concerning the mind^ 
 it leads to error and delufion. 
 
 We may call the firft of thefe ways* the way 
 of 'reflexion. When the operations of the mind 
 are exerted;, we are confcious of them •, and it 
 is in our power to attend to them, and tO reflect 
 upon them, until they become familiar objects 
 of thought. This is the only way in which we 
 Can form jufb and accurate notions of thofe ope- 
 rations. But this . attention and reflection is ib 
 difficult to man, furrounded on all hands by ex- 
 Z 2 < ternai 
 
35 6 Of the H U M A N M IN" D. Chap. VII. 
 
 ternal objects which conftantly folicit his atten- 
 tion, that it has been very little practifed, even 
 by philofophers. In the courfe of this inquiry, 
 we have had many occafions to fhow, how little 
 attention hath been given to the moft familiar 
 operations of the fenfes. 
 
 The fecond, and the moft common way, in 
 which men form their opinions concerning the 
 mind and its operations, we may call the way of 
 analogy. There is nothing in the courfe of na- 
 ture lb fingular, but we can find fome refem- 
 blance, or at leaft fome analogy, between it and 
 other things with which we are acquainted. The 
 mind naturally delights in' hunting after fuch 
 analogies, and attends to them with pleafure. 
 From them, poetry and wit derive a great pare 
 of their charms ; and eloquence, not a little of 
 its perfuafive force. 
 
 Befides the pleafure we receive from analogies, 
 they are of very confiderable ufe, both to facili- 
 tate the conception of things, when they are not 
 eafily apprehended without fuch a handle, and to 
 lead us to probable conjectures about their nature 
 and qualities, when we want the means of more 
 direct and immediate knowledge. When I con- 
 fider that the planet Jupiter, in like manner as the 
 earth, rolls round his own axis, and revolves 
 round the fun, and that he is enlightened by fe- 
 veral fecondary planets, as the earth is enlight- 
 ened. by the moon ; I am apt to conjecture from 
 analogy, that as the earth by thefe means is fit- 
 ted 
 
Chap. VII. CONCLUSION. 357 
 
 ted to be the habitation of various orders of ani- 
 mals, fo the planet Jupiter is, by the like means, 
 fitted for the fame purpofe : and having no ar- 
 gument more direct and conclufive to determine 
 me in this point, I yield, to this analogical rea- 
 foning, a degree of affent proportioned to its 
 ftrength. When I obferve, that the potatoe-plant 
 yery much refembles thefolanum in its flower and 
 fructification, and am informed, that the laft is 
 poifonous, I am apt from analogy to have fome 
 fufpicion of the former : but in this cafe, I have 
 accefs to more direct and certain evidence ; and 
 therefore ought not to truft to analogy, which 
 would lead me' into an error. 
 
 Arguments from analogy aw always at hand, 
 and grow up fpohtaneoufly in a fruitful imagina- 
 tion, while arguments that are more direct, and 
 more conclufive,, often -require painful attention 
 and application : and therefore mankind in gene- 
 ral have been very much difpofed to truft to the 
 former. If one attentively examines the fyftems 
 of the ancient philofophers, either concerning the 
 material world, or concerning the mind, he will 
 find them to be built folely upon the foundation 
 of analogy. Lord Bacon firft delineated the 
 ftrict and fevere method of induction ; fince his 
 time it has been applied with very happy fuccefs 
 in fome parts of natural philofophy ; and hardly 
 in any thing elfe. But there is no fubject in 
 which mankind are fo much difpofed to tijift to 
 the analogical way of thinking and reafoning, as 
 in what concerns the mind and its operations ; 
 Z 3 becaufe, 
 
35 8 OftheHUMAN MIND. Chap. VII, 
 
 becaufe, to form clear and diftinct notions of 
 thofe operations in the direft and proper way^ 
 and to reafon about them, requires a habit of at- 
 tentive reflexion, of which few are capable, and 
 which, even by thofe few, cannot be attained 
 without much pains and labour. 
 
 Every man is apt to form his notions of things 
 difficult to be apprehended, or lefs familiar, from 
 their analogy to things which are more familiar. 
 Thus, if a man bred to the feafaring life, and ac- 
 cuftomed to think and talk only of matters relat- 
 ing to navigation, enters into difcourfe upon any 
 Other fubjedt ; it is well known, that the lan- 
 guage and the notions proper to his own profef- 
 fion are infufed into every fubjecl, and all thing? 
 are meafured by the rules of navigation : and if 
 he mould take it into his head to philofophize 
 concerning the faculties of the mind, it cannot 
 be doubted, but he would draw his notions from 
 the fabric of his (hip, and would find in the mind, 
 fails, mafts, rudder, and compafs. 
 ■ Senfible objects of one kind or other, do no 
 lefs occupy and ingrofs the reft of mankind, than 
 things relating to navigation, the feafaring man. 
 For a confiderable part of life, we can think of 
 nothing but the objedts of fenfe ; and to attend 
 to objefts of another nature, fo as to form clear 
 and diftindl notions of them, is no eafy matter, 
 even after we come to years of reflexion. The 
 condition of mankind, therefore, affords good 
 reafon to apprehend, that their language, and 
 their common notions, concerning the mind and 
 
 its 
 
Chap. VII. CONCLUSION. 359 
 
 its operations, will be analogical, and derived 
 from the objetts of fenfe; and that thefe analo- 
 gies will be apt to impofe upon philofophers, as 
 well as upon the vulgar, and to lead them to ma- 
 terialize the mind and its faculties : and experi- 
 ence abundantly confirms the truth of this. 
 
 How generally men of all nations, and in all 
 ages of the world, have conceived the foul, or 
 thinking principle in man, to be fome lubtile 
 matter, like breath or wind, the names given t o 
 it almoft in all languages fufficiently teftify. We 
 have words which are proper, and not analogical, 
 to exprefs the various ways in which we perceive 
 external objedts by the fenfes ; fuch as feeling, 
 fight, tafie : but .we are often obliged to ufe thefe 
 words analog'cally, to exprefs other powers of 
 the mind which are of a very different nature. 
 And the powers which imply fome degree of re- 
 flexion, have generally no names but fuch as are 
 analogical. The objects of thought are faid to 
 be in the mind, to be apprehended, comprehended, 
 conceived, imagined, retained, weighed, ruminated.' 
 
 It does not appear that the notions of the an- 
 cient philofophers, with regard to the nature of 
 the foul, were much more refined than thofe of 
 the vulgar, or that they were formed in any 
 other way. We fhalldhtingiufh the philofophy 
 that regards our fubjecc into the old and the new. 
 The old reached down to Oes Cartes, who gave 
 it a fatal blow, of which it has been gradually 
 expiring ever fince, and is now almoft eve net. 
 Des Cartes is the father of the new philofcphy 
 
■ $ 6o Of the HTJ M A N M I N D. Chap. VII, 
 that relai.es to this fubjecl: ; but it hath been gra- 
 dually improving fince his time, upon the princi- 
 ples laid down by him. The old philofophy feems 
 to have been purely analogical : the new is more 
 derived from reflexion, but ftill with a very con- 
 fiderable mixture of the old analogical notions. 
 
 Becaufe the objects of fenfe conliit oimattw 
 and form, the ancient philofophers conceived 
 every thing, to belong to one of thefe, or to be 
 made up of both. Some therefore thought, that 
 trie foul is a particular kind of fubtile matter, fe- 
 parable: from our grofs bodies ; others thought 
 that.it is only a particular form of the body, and 
 infeparable from it. For there feem to have been 
 fome" among the ancients, as well as among the 
 moderns, who conceived that a certain ftructure, 
 • or organization of the body, is all that is necefla- 
 ' r'y to render it fen':ble and intelligent. The dif- 
 ferent powers of the mind were, accordingly, by 
 the laft feet of philofophers, conceived to belong 
 to different parts of the body, as the heart, the 
 Brain, the liver, the ftomach, the blood. 
 
 They who thought that the foul is a fubtile 
 matter feparable from the body, difputed to which 
 cf the four elements it belongs, whether to earth, 
 water, air, or fire. Of the three laft, each had 
 its particular advocates. But fome were of 
 opinion, that it partakes of all the elements ; 
 that it muft have fomething in its cornpofition 
 fjmilar to every thing w.e perceive; and that we 
 perceive earth by the earthly part; water, by the 
 watery part; and fire, by the fiery part of the 
 
 foul, 
 
Chap. VII. CONCLUSION. 361 
 
 foul. Some, philofophersj not fatisfied with de-» 
 termining of what kind of matter the foul is 
 made, inquired likewife into its figure, which 
 they determined to be fpherical, that it might be 
 the more fit for motion. The moft fpiritual and 
 fublime notion concerning the nature of the foul, 
 to be met with among the ancient philofophers, 
 I conceive to be that of the Platonifts, who held 
 that it is made of that celeftial and incorruptible 
 matter of which the fixed ftars were made, and 
 therefore has a natural tendency to rejoin its pro- 
 per element. I am at a lofs to fay, in which of 
 thefe clafles of philofophers Ariftotle ought to 
 be placed. He defines the foul to be, The firft 
 I HTiteXtHz of a natural body which has potential life. 
 I beg to be excufed from tranflating the Greek 
 word, becaufe I know not the meaning of it. 
 
 The notions of the ancient philofophers with 
 regard to ehe operations of the mind, particu- 
 larly with regard to perception and ideas, feem 
 likewife to have been formed by the lame kind 
 of analogy. 
 
 Plato, of the writers that are extant, firft in- 
 troduced the word idea into phik>fophy ; but his 
 doctrine upon this fubjecl: had fomewhat peculiar. 
 He agreed with the reft of the ancient philofo- 
 phers in this, that all things confift of matter and 
 form i and that the matter of which all things, 
 were made a exifted from eternity, without form ; 
 but he likewife believed, that there are eternal 
 forms of all pofiible things which exift, without 
 matter j and to thefe eternal and immaterial forms 
 
 he 
 
3 62 Of the H U M A N M I N D. Chap. VII. 
 
 he gave the name of ideas ; maintaining, that 
 they are the only object of true knowledge. It 
 is of no great moment to us, whether he bor- 
 rowed thefe notions from Parmenides, or whe^- 
 ther they were the iflbe of his own creative 
 imagination. The later Platonifts feem to have 
 improved upon them, in conceiving thofe ideas, 
 or eternal forms of things, to exift, not of them- 
 selves, but in the divine mind, and to be the 
 models and patterns according to which all things 
 were made : 
 
 'Then IrSd tF Eternal One, then, deep retired 
 In his unfathom'd ejfenee, view'd at large 
 The uncreated images of things. 
 
 To thefe Platonic notions, that of Malebranche 
 is very nearly allied. This author feems, more 
 than any other, to have been aware of the dif- 
 ficulties attending the common hypothefis con- 
 cerning ideas, to wit, That ideas of all objects of 
 thought are in the human mind ; and therefore* 
 in order to avoid thofe difficulties, makes the 
 ideas which are the immediate obje&s of human 
 thought, to be the ideas of things in the Divine 
 Mind ; who being intimately prefent to every 
 human mind, may difcover his ideas to it, as far 
 as pleafeth him. 
 
 The Platonifts and Malebranche excepted, all 
 other philofophers, as far as I know, have con- 
 ceived that there are ideas or images of every ob- 
 ject of thought in the human mind, or at lead: in 
 
 fomq 
 
Chap. VII. CONCLUSION. 363 
 
 fome part of the brain, where the mind is fup- 
 pofed to have its refidence. 
 
 Ariftotle had no good •affection to the word 
 idea, and feldom or never ufes it but in refuting 
 Plato's notions about ideas. He thought that 
 matter may exift without form ; but that forms 
 pannot exift without matter. But at the fame 
 time he taught, That there can be no fenfation, 
 no imagination, nor intellection, without forms, 
 phantafms, or fpecies in the mind; and that 
 things fenfible are perceived by fenfible fpecies, 
 and things intelligible, by intelligible fpecies. 
 His followers taught more explicitly, that thofe 
 fenfible and intelligible fpecies are fent forth by 
 the objects, and make their impreffions upon the 
 paffive intellect -, and that the active intellect 
 perceives them in the paffive intellect. And this 
 feems to have been the common opinion while 
 {he Peripatetic philofophy retained its authority. 
 The Epicurean doctrine, as explained by Lu- 
 cretius, though widely different from the Peripa- 
 tetic in many things, is almoft the fame in this. 
 He affirms, that flender films or ghofts (tenuia 
 rerum Jimulacra) are ftill going off from all 
 things, and flying about •, and that thefe being 
 extremely fubtile, eafily penetrate our grofs bo- 
 dies, and ftriking upon the mind, caufe thought 
 and imagination. 
 
 After the Peripatetic fyftem had reigned 
 above a thoufand years in the fchools of Europe, 
 ajmoft without a rival, it funk before that of 
 
 Des 
 
364 Of the HUM AN MIND. Chap. VII. 
 Pes Cartes ; the perfpicuity of whofe writings 
 and notions, contracted with the obfcurity of 
 Ariftotle and his commentators, created a ftrong 
 prejudice in favour of this new philofophy. The 
 characleriftic of Plato's genius was fublimuy, 
 that of Ariftotle's, fubtilty ; but Des Cartes 
 far excelled both in perfpicuity, and bequeathed 
 this fpirit to his fucceflbrs. The fyftem which 
 is now generally received, with regard to the 
 mind and its operations, derives not only its 
 fpirit from Des Cartes, but its fundamental prin- 
 ciples ; and after all the improvements made by 
 Malebranche, Locke, Berkeley, and Hume, may 
 ftill be caMcdjbe Cartejzan Jyjlem : we lhall there- 
 fore make fome remarks upon its fpirit and ten- 
 dency in general, and upon its do&rine concern* 
 jng ideas in particular. 
 
 i. It may be obferved, That the method 
 which Des Cartes purfued, naturally led him to 
 attend more to the operations of the mind by ac- 
 curate reflexion, and to truft lefs to analogical 
 reafoningupon this fubjecl, than any philofopher 
 had done before him. Intending to build a fyf- 
 tem upon a new foundation, he began with a 
 refolution to admit nothing but what was abfo- 
 lutely certain and evident. He fuppofed that 
 his fenfes, iiis memory, his reafon, and every 
 Other faculty to which we truft in common life, 
 might be fallacious ; and refolved to difbelieve 
 every thing, until he was compelled by irre- 
 fiftjble evidence to yield, afient. 
 
 In 
 
Chap. VII. CONCLUSION. 3 € 5 
 
 In this method of proceeding, what appeared 
 to him, firft of all, certain and evident, was, 
 That he thought, that he doubted, that he de- 
 liberated. In a word, the operations of his 
 own mind, of which he was confeious, muft be 
 real, and no delufion ; and though all his other 
 faculties mould deceive him, his confeioufnefs 
 could not. This therefore he looked upon as 
 the firft of all truths. This was the firft firm 
 ground upon which he fet his foot, after being 
 tolled in the ocean of fcepticifm ; and he re- 
 folved to build all knowledge upon it, without 
 feeking after any more firft principles. 
 
 As every other truth, therefore, and parti- 
 cularly the exiftence of the objects of fenfe, 
 was to be deduced by a train of ftridf. argumen- 
 tation from what he knew by confeioufnefs, he 
 was naturally led to give attention to the ope- 
 rations of which he was confeious, without 
 borrowing his notions of them from external 
 things. 
 
 It was not in the way of analogy, but of 
 attentive reflection, that he was led to obferve, 
 That thought, volition, remembrance, and the 
 other attributes of the mind, are altogether 
 unlike to extenfion, to figure, and to all the 
 attributes of body; that we have no reafon, 
 therefore, to conceive thinking fubftances to 
 have any refemblance to extended fubftances -, 
 and that, as the attributes of the thinking fub- 
 ftance are things of which we are confeious, we 
 may have a more certain and immediate know- 
 ledge 
 
3 €6 Of the H U M A N M I N D. Chap.' Vl!» 
 
 Jedge of them by reflection, than we can hav6 
 of external objects by our fenfes. 
 
 Thefe obfervations, as far as I know, were 
 firft made by Des Cartes ; and they are of more 
 importance, and throw more light upon the fub- 
 ject, than all that had been faid upon it before; 
 They ought to make us diffident and jealous of 
 every notion concerning the mind and its opera- 
 tions, which is drawn from fenfible objefts, in 
 the way of analogy, and to make us rely only 
 upon accurate reflection, as the fource of all 
 real knowledge upon this fubjedt. 
 
 , 2. I obferve, That as the Peripatetic fyftem 
 has a tendency to materialize the mind, and its 
 operations ; fo the Cartefian has a tendency to 
 fpiritualize body, and its qualities. One error, 
 common to both fyftems, leads to the firft of 
 thefe extremes in the way of analogy, and to the 
 laft, in the way of reflection. The error I 
 mean is, That we can know nothing about body* 
 or its qualities, but as far as we have fenfations 
 which refemble thofe qualities. Both fyftems 
 agreed in this : but according to their different 
 methods of reafoning, they drew very different 
 conclusions from it ; the Peripatetic drawing 
 his notions of fenfation from the qualities of 
 body ; the Cartefian, on the contrary, drawing 
 his notions of the qualities of body from his fen- 
 fations. 
 
 The Peripatetic, taking it for granted that 
 bodies and their qualities do really exift, and are' 
 fuch as we commonly take them to be, inferred 
 
 from 
 
Chap. VII. CONCLUSION. 367 
 
 from them the nature of his fenfations, and 
 reafoned in this manner: Our fenfations are the 
 impreffions which fenfible objects make upon the 
 mind, and may be compared to the impreffion 
 of a feal upon wax ; the impreffion is the image 
 or form of the feal, without the matter of it : 
 in like manner, every fenfation is the image or 
 form of fome fenfible quality of the object. This 
 is the reafoning of Ariftotle, and it has an evi- 
 dent tendency to materialize the mind, and its 
 fenfations. 
 
 The Cartefian, on the contrary, thinks, that 
 the exiftence of body, or of any of its qualities, 
 is not to be taken as a firft principle ; and that 
 we ought to admit nothing concerning it, but 
 what, by juft reafoning, can be deduced from 
 our fenfations •, and he knows, that by reflection 
 we can form clear and diftinct notions of our 
 fenfations, without borrowing our notions of 
 them by analogy from the objects of fenfe. The 
 Cartefians, therefore, beginning to give atten- 
 tion to their fenfations, firft difcovered that the 
 fenfations correfponding to fecondary qualities, 
 cannot refemble any quality of body. Hence 
 Des Cartes and Locke inferred, that found, tafte, 
 fmell, colour, heat, and cold, which the vulgar 
 took to be qualities of body, we're not qualities 
 of body, but mere fenfations of the mind. After- 
 wards the ingenious Berkeley, confidering more 
 attentively the nature of fenfation in>generaL 
 difcovered, and demonftrated, that no fenfation 
 whatever could poffibly refemble any quality of 
 
 an 
 
B 6l OftheHtFMAN MIND. Ckp.VlL 
 
 an infentient being, fuch as body is fuppofed to 
 be; and hence he inferred, very juftly, that 
 there is the fame reafon to hold exterifion, figure, 
 and all the primary qualities^ to be mere fenfa- 
 .tions, as there is to hold the fecondary qualities 
 to be mere fenfations. Thus, by juft reafoning 
 upon the Cartefian principles, matter was flript 
 of all its qualities ; the new fyftem, by a kind of 
 metaphyfical fublimttion, converted all the qua- 
 lities of matter into fenfations, and fpiritualized 
 body, as the old had materialized fpirit. 
 
 The way to avoid both thefe extremes, is* 
 to admit the exiftence of what we fee and feel 
 as a firft principle, as well as the exiftence of 
 things whereof we are confcious •, and to take 
 our notions of the qualities of body, from the 
 teftimony of our fenfes, with the Peripatetics j 
 and our notions of our fenfations, from the tefti- 
 mony of confcioufnefs, with the Cartefians. 
 
 3. I obferve, That the modern fcepticifm is 
 the natural iflue of the new fyftem ; and that, 
 although it did not bring forth this monfter until 
 the year 1739, it may be faid to have carried it 
 in its womb from the beginning. 
 
 The old fyftem admitted all the principles of 
 common fenfe as firft principles, without requi- 
 ring any proof of them ; and therefore, though 
 its reafoning was commonly vague, analogical, 
 and dark, yet it was built upon a broad founda- 
 tion, and had no tendency to fcepticifm. ' We 
 do not find that any Peripatetic thought it in- 
 cumbent upon him to prove the exiftence of a 
 
 material 
 
Chap. VII. CONCLUSION. 3 6 9 
 
 material world ; but every writer upon the Car- 
 tefian fyftem attempted this, until Berkeley 
 clearly demonftrated the futility of their argu- 
 ments ; and thence concluded, that there was no 
 fuch thing as a material world; and that the 
 belief of it ought to be rejected as a vulgar 
 error. 
 
 The new fyftem admits only one of the prin- 
 ciples of common fenfe as a firft principle; and 
 pretends, by ftricT: argumentation, to deduce all 
 the reft from it. That our thoughts, our fenfa- 
 tions, and every thing of which we are confcious, 
 hath a real exiftence, is admitted in this fyftem 
 as a firft principle ; but every thing elfe muft be 
 made evident by the light of reafon. Reafon 
 muft rear the whole fabric of knowledge upon 
 this fingle principle of confcioufnefs. 
 
 There is a difpofition in human nature to re- 
 duce things to as few prinqiples as poffible ; and 
 this, without doubt,' adds to the beauty of a 
 fyftem, if the principles are able to fupport what 
 refts upon them. The mathematicians glory, 
 very juftly, in having raifed fo noble and mag- 
 nificent a fyftem of fcience, upon the foundation 
 of a few axioms and definitions. This love of 
 fzmplicity, and of reducing things to few prin- 
 ciples, hath produced many a falfe fyftem ; But 
 there never was any fyftem in which it appears 
 fo remarkably as that of Des Cartes. His whole 
 fyftem concerning matter and fpirit is built upon 
 one axiom, exprefied in one word cogito. Upon 
 the foundation of confcious thought, with ideas 
 A a for 
 
370 Of the HUMAN MIND. Chap. VII. 
 for his materials, he builds his fyftem of the hu- 
 man underftanding, and attempts to account for 
 all its phenomena : And having, as he imagined, 
 from his confcioufnefs, proved the exiftence of 
 matter; upon the exifcence of matter, and of a 
 certain quantity of motion originally imprefied 
 upon ir, he builds his fyftem of the material 
 world, and attempts to account for all its phe- 
 nomena. 
 
 Thefe principles, with regard to the material 
 fyftem, have been found inefficient; and it has 
 been made evident, that beTides matter and mo- 
 tion, we mull admit gravitation, cohefion, cor- 
 pufcular attraction, magnetifm, and other cen^ 
 tripetal and centrifugal forces, by whkh the 
 particles of matter attract and repel each other. 
 Newton, having difcovered this, and demon- 
 ftrated, that thefe principles cannot be refolved 
 into matter and motion, was led by analogy, 
 and the love of fimplicity, to conjecture, but 
 with a mo.iefty and caution peculiar to him, 
 that all the phenomena of the material world 
 depended upon attracting and repelling forces in 
 the particles of matter. But we may now ven- 
 ture to fay, that this conjecture fell ftiort of the 
 mark. For, even in the unorganized kingdom, 
 the powers by which falts, cryftals, fpars,. and 
 many other bodies, concrete into regular forms, 
 can never be accounted for by attracting and 
 repelling forces in the particles of matter. And 
 in the vegetable and animal kingdoms, there are 
 ftrong indications of powers of a different nature 
 8 from 
 
Chap. VII. CONCLUSION. 371 
 
 from all the powers of unorganized bodies. We 
 fee then, that altho' in the ftru&ure of the ma- 
 terial world there is, without doubt, all the 
 beautiful fimplicity confiftent with the purpofes 
 for which it was made, it is not lb fimple as the 
 great Des Cartes determined it to be : nay, it 
 is not fo fimple as the greater Newton modeftly 
 conjectured it to be. Both were mifled by ana- 
 logy, and the love of fimplicity. One had been 
 much converfant about extenfion, figure, and 
 motion ; the other had enlarged his views to 
 attracting and repelling forces ; and both formed 
 their notions of the unknown parts of nature, 
 from thofe with which they were acquainted, as 
 the ftiepherd Tityrus formed his notion of the 
 city of Rome from his country village : 
 
 Urbem quant dicunt Romam, Melibcee, putavi 
 Stultus ego, huic nofira fimilem, quo fape folemus 
 Paftores avium teneros depellere fcetus. 
 Sic canibus catulos fimiles, fie matribus h^edos 
 Noram : fie parvis componere magna folebam. 
 
 This is a juft piflure of the analogical way of 
 thinking. 
 
 But to come to the fyftem of Des Cartes, con- 
 cerning the human underftanding ; it was built, 
 as we have obferved, upon confeioufnefs as its 
 fole foundation, arid with ideas as its materials ; 
 and all his followers have bu.lt upon the fame 
 foundation and wi,th the fame materials. They 
 acknowledge that nature hath given us various 
 A a 2 k fimple 
 
372 Of the HUMAN MIND. Chap. VII. 
 fimple ideas j Thefe are analogous to the matter 
 of Des Cartes's phyfical fyftem. They acknow- 
 ledge likewife a natural power by which ideas are 
 compounded, disjoined, affociated, compared : 
 This is analogous to the original quantity of mo- 
 tion in Des Cartes's phyfical fyftem. From, 
 thefe principles they attempt to explain the phse- 
 nomena of the human understanding, juft as in 
 the phyfical fyftem the phasnomena of nature 
 were to be explained by matter and motion. It 
 muft indeed be acknowledged, that there is great 
 fimplicity in this fyftem as well as in the other. 
 There is fuch a fimilitude between the two, as 
 may be expected between children of the fame 
 father : but as the one has been found to be the 
 child of Des Cartes, and not of nature, there is 
 ground to think that the other is fo likewife. 
 
 That the natural iffue of this fyftem is fcep- 
 ticifm with regard to every thing except the ex- 
 iftence of our ideas, and of their necefiary rela- 
 tions which appear upon comparing them, is evi- 
 dent: for ideas being the only objects of thought, 
 and having no exiftence but when we are con- 
 fcious of them, it neceflarily follows, that there 
 is no object of our thought which can have a 
 continued and permanent exiftence. Body and 
 fpirit, caufe and effect, time and fpace, to which 
 we were wont to afcribe an exiftence indepen- 
 dent of our thought, are all turned out of exift- 
 ence by this fhort dilemma : Either thefe things 
 are ideas of ienfation or reflexion, or they are 
 not: if they are ideas of fenfation or reflexion, 
 5 they 
 
Chap. VII. CONCLUSION. 373 
 
 they can have no exiftence but when we are con- 
 scious of them, if they are not ideas of fenfation 
 or reflection,, they are words without any mean- 
 ing. 
 
 Neither Des Cartes nor Locke perceived 
 this confequence of their fyftem concerning 
 ideas. Bifhop Berkeley was the firft who difco- 
 vered it. And what followed upon this difco- 
 very ? Why, with regard to the material world, 
 and with regard to fpace and time, he admits 
 the confequence, That thefe things are mere 
 ideas, and have no exiftence but in our minds : 
 but with regard to the exiftence of fpirits or 
 minds, he does not admit the confequence ; and 
 if he had admitted it, he muft have been an ab- 
 lolute fceptic. But how does he evade this con- 
 fequence with regard to the exiftence of fpirits ? 
 The expedient which the good Bifhop ufes on 
 this occafion is very remarkable, and fhows his 
 great averfion to fcepticifm. He maintains, that 
 we have no ideas of fpirits ; and that we can 
 think, and fpeak, and reafon about them, and 
 about their attributes, without having any ideas 
 of them. If this is fo, my Lord, what, fhould 
 hinder us from thinking. and reafoning about 
 bodies, and their qualities, without having ideas 
 of them ? The Bifhop either did not think of 
 this queftion, or did not think fit to give any 
 anfwer to it. However, we may obferve, that 
 in order to avoid fcepticifm, he fairly ftarts out 
 of the Cartefian fyftem, without giving any 
 reafon why he did fo in this inftance, and in no 
 A a 3 other. 
 
374 Ofthe HUMAN MIND. Chap. VII, 
 other. This indeed is the only inftance of a 
 deviation from Cartefian principles which I have 
 met with in the fucceffors of Des Cartes -, and 
 it feems to have been only a fudden ftart, occa- 
 fioned by the terror of fcepticifm ; for in all other 
 things Berkeley's fyftem is founded upon Carte-: 
 fian principles. 
 
 Thus we fee, that Des Cartes and Locke 
 take the road that leads to fcepticifm, without 
 knowing-the end of it -, but they flop fhort for 
 want oflight to carry them farther. Berkeley, 
 frighted at the appearance of the dreadful abyfs, 
 flans afide, and avoids it. But the author of 
 the I'reatife of human nature, more daring and in- 
 trepid, without turning afide to the right hand 
 or to the left, like Virgil's Alefto, fhqor.s direclly 
 into the sulf: 
 
 t^ 
 
 Hie fpscus horrendum, et fievi fpiracula Ditis 
 Mcnftrantur : ruptoque ingens Acheronte vorago 
 Peftiferas aperit fauces. 
 
 4. We may obferve, That the account given 
 by the new fyftem, of that furniture of the 
 human underftanding which is the gift of na- 
 ture, and not the acquiCtion .of our own rea T 
 foaing faculty, is extremely lame and imper- 
 ftft. 
 
 The natural furniture of the human under- 
 ftanding is of two kinds ; Firft, The notions or 
 fimple apprehenfions which we have of things : 
 and Secondly, The judgments or the belief which 
 
 we 
 
C^ap. VII. CONCLUSION. 375 
 
 we have concerning them. As to our notions, 
 the new fyftem reduces them to two claflcs ; 
 ideas of fenfation, and ideas of reflection; the firft 
 are conceived to be copies of our fenfations, re- 
 tained in the memory or imagination ; the fecond, 
 to be copies of the operations of our minds where- 
 of we are confeious, in like manner retained in 
 the memory or imagination : and we are taught, 
 that thefe two comprehend all the materials 
 about which the human underftanding is, or can 
 be employed. As to our judgment of things, 
 or the belief which we" have concerning them, 
 the new fyftem allows no part of it to be the 
 gift of nature, but holds it to be the acquili- 
 tion of reafon, and to be got by comparing our 
 ideas, and perceiving their agreements or difu- 
 greements. Now I take this account, both of 
 our notions, and of our judgments or belief, to 
 be extremely imperfect ; and I fhall briefly point 
 out fome of its capital defects. 
 
 The divifion of our notions into ideas of fen- 
 fation, and ideas of reflexion, is contrary to all 
 rules of logic ; becaufe the fecond member of 
 the divifion includes the firit. For, can we 
 form clear and j aft notions of our fenfations 
 any other way than by reflexion? Surely we 
 cannot. Senfation is an operation of the mind 
 of which we are confeious ; and we get the 
 notion of fen Cation, by reflecting upon that 
 which we are confeious of. In like manner, 
 doubting and believing are operations of the 
 mind wnereof we are confeious j and we get 
 A a 4 the 
 
376 Of the H U M A N M I N D. Chap. VII. 
 
 the notion of them by reflecting upon what we 
 are confcious of. The ideas of fenfation, there- 
 fore, are ideas of reflexion, as much as the ideas 
 of doubting, or believing, or any other ideas 
 whatfoever. 
 
 But to pafs over the inaccuracy of this divi- 
 fion, it is extremely incomplete. For, fince fen- 
 fation is an operation of the mind, as well as all 
 the other things of which we form our notions 
 by reflexion ; when it is aflerted, that all our no- 
 tions are either ideas of fenfation, or ideas of re- 
 flexion, the plain Englifh of this is, That man- 
 kind neither do, nor can think of any thing but 
 of the operations of their own minds. Nothing 
 can be more contrary to truth, or more contrary 
 to the experience of mankind. I know that 
 Locke, while he maintained this doftrine, be- 
 lieved the notions which we have of body and of 
 its qualities, and the notions which we have of 
 motion and of fpace, to be ideas of fenfation. But 
 why did he believe this ? Becaufe he believed 
 thole notions to be nothing elfe but images of 
 our fenfations. If therefore the notions of body 
 and its qualities, of motion and fpace, be not 
 images of our fenfations, will it not follow, that 
 thofe notions are not ideas of fenfation ? Moft 
 certainly. 
 
 There is no doctrine in the new fyftem which 
 more directly leads to fcepticifm than this. And 
 the author of the Treatife of human nature knew 
 very well how to ufe it for that purpofe : for, if 
 you maintain that there is any fuch exiflence as 
 
 body 
 
Chap. VII. CONCLUSION. 377 
 
 body or fpirit, time or place, caufe or effecT:, he 
 immediately catches you between the horns of 
 this dilemma ; your notions of thefe exiftences 
 are either ideas of fenfation, or ideas of reflexion; 
 if of fenfation, from what fenfation are they co- 
 pied ? if of reflexion, from what operation of the 
 mind are they copied? 
 
 It is indeed to be wifhed, that thofe who have 
 written much about fenfation, and about the 
 other operations of the mind, had likewife thought 
 and reflected much, and with great care, upon 
 thofe operations : but is it not very ftrange, 
 that they will not allow it to be poffible for man- 
 kind to think of any thing elfe ? 
 
 The account which this fyftem gives of our 
 judgment and belief concerning things, is as far 
 from the truth as the account it gives of our no- 
 tions or fimple apprehenfions. It reprefents our 
 fenfes as having no other office, but that of fur- 
 nifhing the mind with notions or fimple appre- 
 henfions of things ; and makes our judgment and 
 belief concerning thofe things to be acquired by 
 comparing our notions together, and perceiving 
 their agreements or difagreements. 
 
 We have fhown, on the contrary, that every 
 operation of the fenfes, in its very nature, implies 
 judgment or belief, as well as fimple apprehen- 
 fion. Thus, when I feel the pain of the gout in 
 my toe, I have not only a notion of pain, but a 
 belief of its exiftence, and a belief of fomedifor- 
 der in my toe which occafions it ; and this be- 
 lief is not produced by comparing ideas, and per- 
 ceiving 
 
378 Of the HUMAN'MIND.' Chap. VII. 
 ceiving their agreements and difagreements •, it 
 is included in the very nature of the fenfation. 
 When I perceive a tree before me, my faculty of 
 feeing gives me not only a notion or fimple ap- 
 prehenfion of the tree, but a belief of its exift- 
 cnce, and of its figure, diftance, and magnitude j 
 and this judgment or belief is not got by compa- 
 ring ideas, it is included in the very nature of the 
 perception. We have taken notice of feveral 
 original principles of belief in the courfe of this in- 
 quiry ; and when other faculties of the mind are 
 examined, we mail find more, which have not 
 occurred in the examination of the five fenfes. 
 
 Such original and natural judgments are there- 
 fore a part of that furniture which nature hath 
 given to the human underftanding. They are 
 the in fpi ration of the Almighty, no lefs than our 
 notions or fimple apprehenfions. They ferve to 
 direct us in the common affairs of life, where our 
 reafoning. faculty would leave us in the dark. 
 They are a part of our conftitution, and all the 
 d'ifcoveries ofpurreafon are grounded upon them. 
 They make up what is called the tommati fenfe of 
 mankind; and what is manifeftly contrary to any 
 of thofe firft principles, is what we call abfurd. 
 The ftrength of them is good fenfi, which is. 
 often found in thofe who are not acute in reafon- 
 ing. A remarkable deviation from them, arifing 
 from a diforder in the conftitution, is what we 
 C&W lunacy, as when a man believes that he is 
 made of glafs. When a man fuffers himfelf to be 
 reafoned out of the principles of common fenfe, 
 
 by 
 
Chap. VII. CONCLUSION. 379 
 
 by metaphylkal arguments, we may call this me- 
 taphyseal lunacy ; which differs from the other 
 fpecies of the diftemper in this, that it is not 
 continued, |but intermittent : it is apt to ferae the 
 patient in folitary and fpeculative moments -, but 
 when he enters into fociety, Common Senfe re- 
 covers her authority. A clear explication and 
 enumeration of the principles of common fenfe, is 
 one of the chief defiderata in logic. We have 
 only confidered fuch of them as occurred in the 
 examination of the five fenfes. 
 
 5. The laft obferyation that I fhall make up- 
 on the new fyftem is, That, altho' it profefies 
 to fet out in the way of reflexion, and not of 
 analogy, it hath retained fome of the old analogi- 
 cal notions concerning the operarions of the mind; 
 particularly, That things which do not now ex- 
 ift in the mind itfelf, can only be perceived, re- 
 membred, or imagined, by means of ideas or 
 images of them in the mind, which are the im- 
 mediate objects of perception, remembrance, and 
 imagination. This doctrine appears evidently to 
 be borrowed from the old fyftem ; which taught, 
 that external things make imprefiions upon the 
 mind, like the imprefiions of a feal upon wax ; 
 that it is by means of thofe imprefiions that we 
 perceive, remember, or imagine them ; and that 
 thofe imprefiions mull refemble the things from 
 which they are taken. When we form our no- 
 tions of the operations of the mind by analogy, 
 this way of conceiving them feems to be very 
 natural, and orfers itfelf to our thoughts : for as 
 
 every 
 
380 Of the HUMAN MIND. Chap. VII. 
 every thing which is felt mud make fome im- 
 preffion upon the body, we are apt to think, that 
 every thing which is underftood mult make fome 
 impreflion upon the mind. 
 
 From fuch analogical reafoning, this opinion 
 of the exiftence of ideas or images of things in 
 the mind, feems to have taken its rife, and to 
 have been fo univerfally received among philofo- 
 phers. It was obferved already, that Berkeley, in 
 one inftance, apoftatizes from this principle of 
 the new fyftem, by affirming, that we have no 
 ideas of fpirits, and that we can think of them 
 immediately, without ideas. But I know not 
 whether in this he has had any followers. There 
 is fome difference likewife among modern philo- 
 fophers, with regard to the ideas or images by 
 which we perceive, remember, or imagine fenfi- 
 ble things. For, tho 5 all agree in the exiftence of 
 fuch images, they differ about their place ; fome 
 placing them in a particular part of the brain, 
 where the foul is thought to have her refidence, 
 and others placing them in the mind itfelf. Des 
 Cartes held the firft of thefe opinions ; to which 
 Newton feems likewife to haye inclined ; for he 
 propofes this query in his Optics : " Annon fen- 
 " forium animalium eft locus cui fubftantia fen- 
 " tiens adeft, et in quern fenfibiles rerum fpecies 
 " per nervos et cerebrum deferuntur, ut ibi 
 " prsefentes a prsefente fentiri poflint ?" But 
 Locke feems to place the ideas of fenfible things 
 in the mind : and that Berkeley, and the au- 
 thor of the Treatife cf human nature, were of 
 
 the 
 
Chap. VII. CONCLUSION. 381 
 
 the fame opinion, is evident. The laft makes 
 a very curious application of this do&rine, by 
 endeavouring to prove from it, That the mind 
 either is no fubftance, or that it is an extended 
 and divifible fubftance ; becaufe the ideas of ex- 
 tension cannot be in a fubjeft which is indivifible 
 and unextended. 
 
 I confefs I think his reafoning in this, as in 
 moil cafes, is clear and ftrong. For whether 
 the idea of extenfion be only another name for 
 extenfion itfelf, as Berkeley and this author af- 
 fert ; or whether the idea of extenfion be an 
 image and refemblance of extenfion, as Locke 
 conceived ; I appeal to any man of common 
 fenfe, whether extenfion, or any image of ex- 
 tenfion, can be in an unextended and indivifible 
 fubjeft. But while I agree with him in his rea- 
 foning, I would make a different application of 
 it. He takes it for granted, that there are ideas 
 of extenfion in the mind ; and thence infers, 
 that if it is at all a fubftance, it muft be an ex- 
 tended and divifible fubftance. On the con- 
 trary, I take it for granted, upon the teftimony 
 of common fenfe, that my mind is a fubftance, 
 that is, a permanent fubjedt of thought ; and my 
 reafon convinces me, that it is an unextended 
 and indivifible fubftance ; and hence I infer, 
 that there cannot be in it any thing that re- 
 fembles extenfion. If this reafoning had oc- 
 curred to Berkeley, it would probably have led 
 him to acknowledge, that we may think and 
 reafon concerning bodies, without having ideas 
 
 of 
 
382 Ofthe HUMAN MIND. Chap. ViL 
 
 of them in the mind, as well as concerning fpi- 
 nts. 
 
 I intended to have examined more pa: iciv 
 larly and fully this dodtrine of the exiftenee of 
 ideas or images of things in the mind-, and 
 likewife another doctrine, which is founded up- 
 on it, to wit, That judgment or belief is no- 
 thing but a perception of the agreement or dif- 
 agreement of our ideas : but having already 
 fhewn, through the courfe of this inquiry, that 
 the operations of the mind which we have exa- 
 mined, give no countenance to either of thefe 
 doctrines, and in many things contradict them, 
 I have thought it proper to drop this part of my 
 defign. It may be executed with more advan- 
 tage, if it is at all necefiary, after inquiring in- 
 to fome other powers of the human underftand- 
 
 ing. 
 
 Although we have examined only the five 
 fenfes, and the principles of the human mind 
 which are employed about them, or fuch as have 
 fallen in our way in the courfe of this examina- 
 tion -, we (hall leave the further profecution of 
 this inquiry to future deliberation. The powers 
 of memory, of imagination, of tafte, of rea-' 
 foning, of moral perception, the will, the paf- 
 fions, the affedions, and all the active powers 
 of the foul, prefent a vaft and boundlcfs field of 
 philofophical difquifition, which the author of 
 this inquiry is far from thinking himfelf able to 
 furvey with accuracy. Many authors of in- 
 genuity, ancient and modern, have made ex- 
 
 curfions 
 
Chap. VII. CONCLUSION. 383 
 
 curfions into this vaft territory, and have com- 
 municated ufeful obfcrvations : but there is rea- 
 fon to believe, that thofe who have pretended. 
 to give us a map of the whole, have fatisfied 
 themfelves with a very inaccurate and incom- 
 plete furvey. If Galileo had attempted a com- 
 plete fyftem of natural pbilolbphy, he had, pro- 
 bably, done little fervice to mankind : but by 
 confining himfelf to what was within his com- 
 prehenfion, he laid the foundation of a fyftem 
 of knowledge, which rifes by degrees, and dees 
 honour to the human underftanding. Newton, 
 building upon this foundation, and m like man- 
 ner, confining his inquiries to the law of gravi- 
 tation and the properties of light, performed 
 wonders. If he had attempted a great deal 
 rnore, he had done a great deal lefs, and per- 
 haps nothing at all. Ambitious of following 
 fuch great examples, with unequal fteps, alas I 
 and unequal force, we have attempted an in- 
 quiry only into one little corner of the human 
 mind ; that corner which feems to be mod: esc- 
 pofed to vulgar obfervation, and to be moil eafily 
 comprehended ; and yet, if we have delineated 
 it juftly, it muft be acknowledged, that the 
 accounts heretofore given of it,, were very lame, 
 and wide of the truth. 
 
 THEE N D.