CORNELL UNIVERSITY LIBRARY BOUGHT WITH THE INCOME OF THE SAGE ENDOW^MENT FUND GIVEN IN 189I BY HENRY WILLIAMS SAGE Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924029046774 MECHANISM, LIFE AND PERSONALITY PREFACE This book consists of four lectures which were delivered in the Physiological Labora- tory of Guy's Hospital, during May of this year, as a London University course for senior students. They are reproduced in the form of their delivery, after careful revision, in which I have been much aided by the criticisms and suggestions of my friend Professor J. T. Wilson, F.RS. Philosophical readers who may have chanced to see an essay by my brother and myself on ' The Relations of Philosophy to Science ' in Essays in Philosophical Criticism^ published in 1883, will recognise in these lectures a de- velopment of the ideas put forward in that essay. In a presidential address which I delivered in 1908 before the Physiological Section of the British Association, and in other scattered papers, the same line of argu- ment in relation to the aims of biology and vi PREFACE its position among the sciences was followed out in certain directions. The lectures now published represent an attempt at a more comprehensive treatment of the subject. The time is now more than ripe for bring- ing the great biological movement of the nineteenth century into definite relation with the main stream of human thought; and these lectures form a contribution towards the fulfilment of this task. CONTENTS LECTURE I PAGE The Mechanistic Theory of Life, ... 1 LECTURE TI Criticism of the Mechanistic Theory, . . 31 LECTURE III Biology and the Physical Sciences, , , , 66 LECTURE IV Personality, . 1 06 vil, LECTURE I THE MECHANISTIC THEORY OF LIFE The aim of the first two of these lectures is to examine the hypothesis that living organisms may be regarded as conscious or unconscious physical and chemical mechanisms, and can be satisfactorily investigated from this stand- point. In this first lecture I shall endeavour to state, as well as I can, the case for what may be called, in the absence of a better expression, the mechanistic theory of life. The researches of countless investigators have established with practical unanimity certain very fundamental facts with regard to living organisms(T)One of these is that the matter of which the bodies of organisms are found by analysis to be composed consists of the same chemical elements as are found outside the body, and that no new matter is formed in the body, or disappears 2 THE MECHANISTIC THEORY OF LIFE from it. All the matter which is found in the body, or which passes from it, can be accounted for by what is taken up from the environment. Of the particular chemical si^bstances, moreover, which have been found in the body a large and ever increasing number can be formed artificially outside it, and there is no reason for believing that any ultimate difficulty will be experi- enced in artificially forming any of the chemical substances which have been dis- covered, or are ever likely to be discovered, within the body. ^K /Another fundamental fact is that the whol-e of the energy whi^ch is liberated in the body, whether as beat, mechanical work, or in other forms, can be traced to sources outside the body. The actual external sources of energy in the living body were first pointed out in general terms by Mayer more than sixty years ago, and the exact investigations of subsequent physiologists have completely verified his general conclusions. The two great physical laws of conservation of matter and conservation of energy can thus be extended with apparently rigorous MATTER, ENERGY AND LIFE 3 accuracy to all living organisms, including human beings. From this it may be inferred that, however complex may be the changes involvS3"te*grganic activity,T;Hey are nothing but changes in a material system. As yet we are far from being able to trace this system and its changes completely ; but the main outlines are clear, and the gradual filling in of details can only be a matter of time, though we shall probably never succeed in completely filling in all the details. It is true that, in the case of at least the higher organisms, consciousness accompanies some of the material changes in the living body, \vhereas consciousness is not known to accompany material changes in the in- organic world. Of this mysterious accom- paniment we can of course give no physical account. Possibly consciousness accompanies all material change ; but whether or not this is the case, consciousness seems to make no difference in the end to thnly stands the most searching laboratory tests, but that it also stands the tests of practical experience of a very wide kind. The engineer, the manufacturer, the navigator, the soldier, the lawyer, can apparently rely upon it absolutely. B'lt philosophy points out that if it corresponds to absolute reality it must be consistent with the whole of our experience ; and first and foremost it must be consistent with our own conscious relations to it, which have, after all, been entirely left out in the laboratory and other tests. At first it may seem simple enough to say that we are conscious of the physical world. It is there, plainly before us. But then comes the reflection that the appearance can only be transmitted to us through our sense organs DAVID HUME 69 and sensory nerves. All that we immediately perceive can only be sensory disturbances of some kind, from which we infer the exist ence of the physical reality outside. This is a necessary, but also a fatal admission : for what right have we to draw such an inference? Absolutely none, as Bishop Berkeley first pointed out. We have no right even to call our sensations impressions, or to regard ourselves as anything more than a stream of sensations. The appearance of a sensible world, with our bodies present in it, can be nothing but an appearance due to the manner in which the sensations group themselves. The appearance of substantiality or of cause and effect can be due to nothing else but the mysterious fact that certain sensations are associated together or follow one another in a certain order. Such was the reasoning of David Hume ; and his inferences follow inevitably if we start with the provisional assumption that the physical world as science represents it to us has absolute reality. If it has, then we cannot possibly know it ; and all our supposed knowledge is nothing but the. illusion which Hume described. e2 70 BIOLOGY AND PHYSICAL SCIENCES There is no flaw in the reasoning of Berkeley and Hume, absurd as may seem the conclusions which they reached. The flaw is in the premises, and particularly in the assumption from which the reasoning originally started, that the world is some- thing self-existent and outside us, as physical science appears to teach. This assumption simply destroys itself, leaving nothing but the sceptical conclusions of Hume. How long will it be till the world, and particularly the scientific world, begins to take in the significance of David Hume's reasoning ? His body has lain quiet at the foot of the Calton Hill in Edinburgh for nearly a hundred and forty years ; but the old ideas which he finally showed to be un- tenable are still popularly accepted, just as if he had never lived. To those who imagine that the secrets of our existence are likely to be revealed in, say, the latest discoveries in colloid chemistry, I would commend a careful perusal of Hume's Treatise of Human Nature. Whether we take the ordinary popular view, as taught by the theologians, that the IMMANUEL KANT 71 soul is a non-material entity situated during life within a material body in a material world, or else adopt the mechanistic theory that there is no soul, but only a series of * states of consciousness* lighted up some- how or other within a material brain, we cannot escape Hume's destructive criticism. This criticism destroys utterly the assumption of a universe of self-existent things. But the appearance of knowledge of our universe and all that it contains does certainly exist and must be accounted for. The task of accounting for it was taken up by Immanuel Kant, who carried us far beyond Hume. Kant did not satisfy himself with Hume's account of the data of consciousness as a stream of isolated impressions or sensations, cohering or associating themselves with one another in a manner of which we can give no ultimate account. He proceeded to ex- amine carefully the nature of sensation or perception. One thing which he found was that sensations never do exist in isolation from one another, but that each carries with it a reference to other sensations. A sensation, if it is distinguishable at all, is here and now. 72 BIOLOGY AND PHYSICAL SCIENCES This means that it is given in relation to past, future, and co-existent states of consciousness which are indissolubly united with one another. Moreover, each distinguishable element in experience bears with it its relation to the others in a certain order. Were there no such definite relations of sequence and spatial in- terconnection there could be no perceptipn or experience at all : the ' hereness ' and * nowness ' of each element in experience would be impossible. Hence spatial and temporal relations, causal sequence, substan- tiality, and the other general ideas by the existence of which our experience is ordered, are all given to us in the simplest elements of experience. The supposed possibility of analysing our perceptions into elements con- sisting of ' simple ' unrelated sensations or * states of consciousness,' is an illusion. There are no such things as unrelated sensations. Now this, of course, does not imply that the whole visible universe is given to us as an intelligibly connected system as soon as we open our eyes. It does mean, however, that from the beginning the outlines of such a system are present, however dim and indefinite IMMANUEL KANT 7: the details may be. It means also that be tween ourselves and the world round us, an< between the various things which we find ii the wtJild, there is no ultimate separatenes of existence such as seems to be assumed ii the ordinary physical conception of the world All are parts of one inseparable whole. This is a conclusion of such stupendous an< far-reaching import that it may need centurie for the world to take it in and even diml; realise its implications, and where it lead us to. Sooner or later, however, it will bi realised that the materialism of the nineteentl century has been nothing but an insignifican eddy in the stream of human progress. Ii Kant's writings his thought was evidently trammelled by the difficulty of realising hov great a leap forward he was making. Hume' scepticism had not completely done its worl in his mind, for he still postulates the existenc( of a so-called noumenal world of things-in themselves which are the unknowable caus< of the constant newness and variety in ou: experience. He also retains the idea of finit< individual minds, each armed, as it were, witl general ideas or ' categories ' which conver 74 BIOLOGY AND PHYSICAL SCIENCES into the orderly system of our experience the impressions caused by the noumenal reality. His immediate successors pointed out that there was no reason left for assuming the existence of things-in-themselves outside of us. These supposed existences are nothing but the ghosts of the world of independently existing matter which Hume had shown to be non-existent. The supposed separately existing finite minds are also not proof against Hume's criticism. We must account other- wise for all the variety and ' contingency ' of our universe. Both the external world of things and the spiritual world of persons have their existence, somehow or other, in only one Supreme Existence. In the efforts to show in detail how this is so the philosophical movement initiated by Kant exhausted itself for the time; but we shall have occasion to return later to these efforts. We must now look somewhat more closely at Kant's account of how the sensible world comes to appear to us as it does, and what bearing his conclusions, and those of his suc- cessors, have on the great biological problem which is the main subject of these lectures. KANT AND BIOLOGY 75 Kant enumerated definitely the * categories ' or general ideas under which he believed that our perceptions are ordered. This list seems very artificial, and is based on the old formal logic, but it includes the ideas of substance, cause and effect, and reciprocal action — the ideas of the physics of Kant's time. He him- self, it may be remarked, was a physicist and mathematician of no mean repute. The list limits perception to the perception of a purely physical world, such as the physical sciences described, and he had no special category for living organisms. On Kantian principles, therefore, a living organism can only be per- ceived as a material structure or mechanism. In this respect, Kant was at one with the mechanistic school of biologists. For him, however, the reason why we must perceive organisms as mechanisms is not because they, in themselves, are mechanisms, but because the mind is so constituted that it can only perceive them as mechanisms. Kant's successor, Hegel, pointed out that his list of categories was incomplete in various directions: also that a special cate- gory or categories ought to be added 76 BIOLOGY AND PHYSICAL SCIENCES for organic life, as the idea of life is one of the fundamental ideas. There is no reason why a category or general conception of life should not be just as much constitutive df our experience as the category of substance. Here,, there- fore, we have a possible way out of our difficulties with the mechanistic theory of 'life. In trying to reduce life to physical and chemical mechanism we are perhaps in some way confusing two different cate- gories. Kant's general philosophical con- clusions have in any case thrown a quite new light on our conceptions of the physical world, and have taught us that the validity of these conceptions is of a very different nature from what was previously believed. It may be that just as we cannot base physics on the purely mathematical conceptions of exten- sion, so we cannot base biology on the purely physical conceptions of matter and energy. With these possibilities in mind let us return to a discussion of the facts which biological investigation discloses. \ What we have first to ask is whether, as a matter of fact, we habitually use, in dealing THE CONCEPTION OF ORGANISM 77 with the phenomena of life, a fundamental conception or working hypothesis which is different from the fundamental conceptions of the physical sciences, and cannot be reduced to them. The question, for the moment, is not whether we are justified in using such a conception, but whether we actually do use it. When this question is clearly realised there is, it seems to me, but one answer to it, and that in the affirmative. In dealing with life we not only use a whole series of special terms, but these terms appear to belong to a specific general conception which is never made use of in the physical sciences. Life manifests itself in two ways — as struc- ture and as activity. But we also recognise — a biologist feels it in his very bones — that this is living structure and livirig- activity. Each part of the structure not only bears a more or less definite spatial relation to the other parts, but it is actively maintained in that relation. The structure is thus in itself the expression of the activity, and the ceaseless metabolic activity of which visible structure is the sensuous expression forms one department of 78 BIOLOGY AND PHYSICAL SCIENCES physiological study — that of nutrition. But the more closely living activity in general is examined, the more clear does it become that all living activity is structural or metabolic activity, either directly or indirectly. The changes in the retina when light falls upon it are metabolic or structural activities. The same is true of the activities of nerve cells, muscle cells, gland cells, or any other living cells; and the gross visible movements of the body, no less than its gross visible struc- ture, are but the outer sign of metabolic activity. The body can also be affected mechanically or chemically by influences from without ; but effects so produced are of not the slightest interest to a. biologist, except in so far as they may be connected with living activity. . The living structure is evidently organised : that is to say I every pggrt of it bears a definite relation to every other part. As, however, the structure is the outcome of metabolic activity, it follows that the. metabolic activity of the living body is also organised, every aspect of it bearing a definite relation to ORGANISM AND ENVIRONMENT 79 every other aspect. That this is actually so has become more and more clear with the advance of physiology, particularly in recent times. The fundamental mistake of the mechanistic physiologists of the middle of last century was that they completely failed to realise this. Such processes as secre- tion, absorption, growth, nervous excitation, muscular contraction, were treated as if each was an isolable physical or chemical process, instead of being what it is, one side of a many-sided metabolic activity, of which the different sides are indissolubly associated. q^ The relation of the living organism to its environment is no less peculiar and specific than the relationship of the internal parts and activities of the organism itself. Between organism and environment a constant active exchange is going on. But this exchange, in so far as it has any physiological significance, is always determined in relation to the rest of the living activity of the organism. . Whether material is to be taken up or given off, whether and to^what extent the organism is to respond to any ^stifnulus,' all this is determined in relation to the life of the 80 BIOLOGY AND PHYSICAL SCIENCES organism as a whole. The living body and its physiological environment form an organic whole, the parts of which cannot be under- stood in separation from one another. Our ordinary language as applied to life corresponds with these characteristics. We naturally speak of a living organism as an autonomous active whole, and think of it as such. The idea of its being a mechanism made up of separable parts, and actuated by external causes, is wholly unnatural to us, and becomes more and more unnatural the more we know about organisms. The concept we are using is radically different from any physical concept : for in conceiving what is living we do not separate between matter or structure and its activity. The structure itself is conceived as active — as alive. But the objection may be raised that this is only a loose and inaccurate mode of thinking and expression : for we know that the living substance consists of nothing but matter, though we do not yet know in what exact form the atoms or molecules are combined. This, it must be pointed out clearly, is simply ORGANISM AND MATTER 81 to beg the whole question. It was the com- plete and hopeless failure of the material conception of a living organism that led to our present inquiry. We cannot admit that the living * substance ' is material. It is the very existence of matter as such that is in ques- tion — the adequacy of the concept * matter ' to express the phenomenon we are considering. Let us make no mistake as to what we are really discussing. We have parted company once and for all with the mechanistic philosophy — the notion of a real and self- existent material universe ; and we must remember where we now are. What we have found is that the conception of the living organism is in common and ordinary use, and differs radically from any physical conception. We have also seen that there is no philosophical reason for rejecting this conception. There is no a priori reason why we should not, if it helps us, take it as the fundamental conception for biology, just as the physicist takes the con- ceptions of matter and energy as fundamental for physics. Before going further we must consider a 82 BIOLOGY AND PHYSICAL SCIENCES preliminary objection. Whatever the nature of the actually living parts of an organism may be, all that we can do in investigating them, it may be pointed out, is to observe and measure the physical and chemical changes resulting from their activity. We can measure the shortening of a muscle, the pull it produces, the oxygen it absorbs, the electrical changes which accompany its excitation. All these are physical and chemical changes, however ; and the whole of physiology consists, and can only consist, of such observations and measurements. It must, therefore, from the very nature of its data, be a physical and chemical science in so far as it is a science at all. The reply to this is that apparent physi- cal and chemical changes are the signs or sensuous data which point to the underlying living activity. Just as the physicist has no direct detailed knowledge of matter, but in- fers its properties and measures its amount from various sensuous data, so the physi- ologist infers the nature and activities of a living organism from sensuous data. But to the physiologist the outward appearances of TRUE AIM OF BIOLOGY 83 physical and chemical change are the sensuous data, by bringing which into relation with his guiding idea he arrives at physiological know- ledge; and what he sees behind the appear- ances of changes in form, electrical changes, absorption of oxygen, and all the other out- ward signs of muscular activity is the meta- bolic activity of the living muscle-cells. If we assume that the conception of the living organism is the fundamental conception of biology, it is clear that the aim of biology differs entirely from what it would be if the mechanistic theory were accepted. All attempts to trace the ultimate mechanism of life must be given up as meaningless. The aim of biology becomes a very different one — to trace in increasing detail, and with increas- ing clearness, the organic determination which the ground conception postulates. The bodily processes — for instance, the apparent mechanical or chemical processes of movement of the limbs, of breathing, of circulation, of digestive changes, of the taking up and giving off of various forms of matter and energy — become nothing but the expression of organic activity. Their maintenance and working 84 BIOLOGY AND PHYSICAL SCIENCES during life are only phases of the organic determination which is the key to all the phenomena of life. They must be looked at from the physiological or biological standpoint, and not merely from that of the physical sciences. The details of bodily structure must likewise be interpreted as the expression of or ganic determination . Now it seems to me that the actual pro- gress of physiology, and of biology generally, corresponds exactly with the increasing realisation of this aim. It has already been shown that in tracing the history of phy- siology we find that on the whole there has been no apparent progress whatsoever towards the mechanistic goal. On the other hand it is perfectly plain that there has been enormous progress, not merely in ascer- taining isolated facts, but in tracing organic determination in every detail of bodily struc- ture and physiological activity. ^ To illustrate this conclusion in detail it would be necessary to present to you, not a single lecture, but a whole text-book of physiology. I shall, however, try to give a single illustration by tracing roughly part of ORGANIC DETERMINATION 85 the progress of our knowledge in relation to the regulation of breathing. From the earliest times it was of course known that in all the higher animals breathing is an essential part of organic activity, as mechanical stoppage of the breathing causes rapid death. Very little further was known, however, until the time of Black, Priestley, and Lavoisier, althongh Mayow, the funda- mental importance of whose work was not at the time appreciated, had in reality come very close to modern ideas. With a single flash the whole subject was illuminated by the definite discovery of oxygen and carbon dioxide and their relation to respiration. Henceforth we knew that the necessity for breathing, and the regulation of breathing, is bound up with the necessity for absorbing oxygen and giving off carbon dioxide. Breath- \ ing is of fundamental physiological importance, because the consumption of oxygen and re- moval of carbon dioxide are fundamental organic activities in animals. Assuming that an organism is an organ- ism, and not a mere machine, we should expect to find that these activities are organi- f2 86 BIOLOGY AND PHYSICAL SCIENCES cally determined— determined as in definite relation to the whole functional and structural activities of the organism, and not merely dependent on specific and one-sided conditions, such as the abundance of oxygen in the in- spired air, or its freedom from carbon dioxide, or some mechanical action of the nervous system, unrelated to the central organic deter- mination. Misled by mechanistic conceptions of life, various physiologists have, as a matter of fact, put forward one-sided theories of this kind, and they have invariably turned out to be wrong. As an example we may take the theory that owing to the structure of the respiratory centre, and the properties of the afferent nerves coming to it from the lungs, breathing goes on, under ordinary conditions, automatically and without reference to the removal of carbon dioxide or intake of oxygen. It was believed that as distention of the lungs excites fibres in the vagus-nerve which inhibit inspiration, and collapse of the lung correspond- ingly excites fibres which excite inspiration, normal breathing is regulated by this mechan- ism, though the centre also responds to any ORGANIC DETERMINATION 87 unusual want of oxygen or excess of carbon dioxide in the blood. Now it seemed extremely improbable that such a theory could be correct ; since living organisms do not regulate their affairs in this mechanical manner. Thus guided, we rein- vestigated the whole question in the Oxford Physiological Laboratory, and found that as a matter of fact the breathing is, under normal conditions, so regulated in man as to re- spond with almost incredible exactness to the slightest variation in the output of carbon dioxide or partial pressure of carbon dioxide in the alveolar air. The vagus nerve-fibres play no part in the main regulation, to which their influence is only subsidiary, though not unim- portant. Under ordinary conditions the constancy in the pressure of carbon dioxide in the lung alveoli provides for the supply of oxygen to the lungs and blood ; but quite evidently the breathing is, under abnormal conditions, regu- lated also in direct relation to the oxygen supply ; and the action of the lung epithelium, the concentration of hsemoglobin in the blood, and the mode in which oxyhsemoglobin is 88 BIOLOGY AND PHYSICAL SCIENCES dissociated in the blood, play an important part in helping this regulation. ' The idea which gives unity and coherence to the whole of the physiology of respiration is that of the organic determination of the phenomena. The same idea has to a greater or less extent already given, or is in process of giving, unity and coherence to the phenomena of nutrition, secretion, and circulation. It is an idea which guides us at every turn in physiological work, and constantly suggests new lines of investigation. To leave it out of account in physiology, or to treat it as a mere * heuristic principle ' of very uncertain value, seems to me about as foolish as it would be to reject the idea of mass in chemistry, and retain the phlogiston theory, as Priestley and Caven- dish actually did till their deaths. By regard- ' ing the structure and activities of a living organism as the expression of organic unity we arm ourselves with a theory which is just as useful in biology as the idea of mass in chemistry. Neither the idea of mass nor that of organism will enable us to predict everything in the chemical and biological worlds respectively, but they both help us DEFECTS OF CURRENT PHYSIOLOGY 89 enormously in reducing our observations to order. When we turn from actual physiological investigation to the current text-books on the subject we are confronted by the fact that in accordance with prevalent philosophical beliefs among physiologists, these books are mainly written from what is essentially a mechanistic standpoint, and follow more or less closely the general plan of Ludwig's famous text- book of sixty years ago. An account is given of the physical structure and chemical materials found in the body and its environ- ment, and this account is combined with an analysis of how the whole works when the various elements so distinguished are brought into relation with one another during life. In this general plan there is absolutely no place left for the living organism as such. We find, moreover, that the various ' mechanisms ' to which the headings of the various chapters correspond — the mechanisms of neuro-mus- cular activity, nutrition, secretion, absorption, etc. — exist, for both reader and author, only as ideals on paper ; and at the end the reader is perhaps inclined to become a vitalist — per- 90 BIOLOGY AND PHYSICAL SCIENCES haps not. The author, too, may probably have displayed suspicious vitalistic tendencies. One thing, however, is pretty clear — that the in- formation supplied with regard to the central or 'elementary' problems of physiology is often so vague as to be of little apparent practical importance. The practical physio- logical information which a student of medi- cine needs and uses is to a large extent only picked up afterwards at the bedside or in the study of experimental pathology. What is the reason for this defect in physiological teaching? One might at first suppose that whatever general theoretical opinions might be held by a physiological teacher, yet the facts of the science itself must be the same, and that in teaching the facts, as undoubtedly he does to the best of his ability, he must be doing all that is possible. But here comes in the question, what facts? The facts recorded by physiologists are absolutely indefinite in number, and only the more important ones can be taught. Hence, in accordance with the general plan just alluded to, only those facts which bear on the ' mechanisms ' of the DEFECTS OF CURRENT PHYSIOLOGY 91 various physiological processes can be taught. If, for instance, we are teaching the physi- ology of the kidneys, we must teach the main facts bearing on the possible mechanism of secretion of urine. We must thus discuss the possible influence of filtratidn, diffusion, etc., in the process, leaving out of account all details which are irrelevant to this dis- cussion ; and when at the end it turns out that the essential mechanism of secretion is quite unknown there is nothing further to do than pass on to the next subject. Actually it is known that, mechanism or no mechanism, the kidney fulfils its functions of regulating the composition of the blood, and that it does so with marvellous delicacy ; but facts relating to this do not fit into the plan of exposition of the subject, and have too much of a smack of old-fashioned teleology about them. Hence they are ignored completely, or scarcely touched upon. It is the same with circulation, respiration, and every other part of physiological know- ledge. The fact that the body lives as a whole, each organ or part fulfilling its proper functions and adapting itself to every change. 92 BIOLOGY AND PHYSICAL SCIENCES is scarcely touched upon, while a vast mass of unrelated and unassimilable mechanical detail is carefully recorded and described. The fault evidently lies in the general plan of exposition. This plan does not fit the facts to be described. The living body is a living organism, and physiology must treat it as such, or else submit to the reproach of being a complete failure. The attempt to treat physiology on the principles so clearly laid down in Ludwig's Introduction to his text-book is as wide of the mark as would be an attempt to treat painting and sculpture on the basis of a mere knowledge of the chemistry and physics of paint and marble. Teaching and investigation must begin, con- tinue, and end with the presupposition that the body is a living organism, which must be seen as a whole if it is to be seen at all. To shut our eyes to the central fact of living organic existence is to shut our eyes to physiology itself, and to biology generally. It does not matter what aspect, or what portion of physiology or biology we are studying : we are always face to face with living organisms as wholes or parts of REPRODUCTION AND DEATH 98 organic wholes. The divisions of the subject are due, either to the particular organisms studied, or to the particular methods of investigation which we happen to be capable of using to advantage. In so far as we are in earnest with the work, and are not blinded by wrong theories, we are always, both in physiological and morphological investigation, studying an organism as a whole. In the case of the higher organisms we are of course dealing with a compound organism ; and we have all shades between highly organised compound organisms and more or less indefinite collective organisms such as a colony or a whole species. In these organisms there is constant active main- tenance, constant renewal, constant breaking down and reproduction of the living struc- ture ; and this is of the very essence of our conception of life. Reproduction is not in itself a problem, but an axiom ; for all living structure is active structure ; and it lives in actively maintaining itself and reproducing its structure. In normal reproduction and death, and in 94 BIOLOGY AND PHYSICAL SCIENCES all instinctive social activity, the individual organism shows itself to be more than a mere individual : it belongs to a wider organic whole. Death is certainly not the mere mechanical wearing out of the organic machine : for the organism, as we have already seen, is no machine. Not only in reproducing itself as a whole, but also in the metabolic processes by which it is changing its substance at every moment, does it flout such a conception. So far as we can at present understand the matter, the physiology of death, and that of reproductive and social activity in all their wide ramifications, belong to the physiology of the species. The indi- vidual organism, like the individual cell in a complex organism, belongs to a wider organic whole, apart from which much of its life is unintelligible. It may be argued that in postulating the existence of such a thing as a living organism as a specific entity we are abandoning all attempt at explanation. We are certainly abandoning the attempt at causal explana- tion ; but in doing so we are only abandoning the philosophical ideas which have already KANT AND HEGEL 95 been shown to be defective and irreconcilable with experience in relation to the phenomena of life. This part of our experience implies the conception of life. By a process of abstraction from the distinctive facts of life we can, it is true, regard organisms as simply so much matter, with so much energy passing through them. If they had turned out to be capable of interpretation as mechanisms this would have been no ab- straction, but a correct way of regarding them. But since they are what they are, their structure must be regarded as living structure, and their activity as living activ- ity, both structure and activity being the expression of an organic and indivisible whole. The ideas of matter and energy are notching but ideas, and in the case of life these ideas are united and transformed in the idea of the living organism. This leads us back to the philosophical conclusions of Kant and his successors. For Kant the categories or general conceptions under which our experience is ordered were so many separate conceptions unrelated to one another. We might roughly compare 96 BIOLOGY AND PHYSICAL SCIENCES them to the chemical elements as they appeared to science before the discovery of the periodic law arid the breaking down and probable building up of elements. Hegel pointed out that not only was Kant's list of categories incomplete, but that the cate- gories bear a natural relation to one another, the lower being the more abstract or empty general conceptions furthest from reality, and the higher being the more concrete and definite ones nearest to reality. If, *for in- stance, we regarded our experience as con- sisting of nothing but qualitatively different data we should be using an empty and abstract category. If we regarded it as a world of substances acting on one another we should be seeing it under a much less empty category, and the qualities and their changes would now appear as the qualities and changes of substances. If we regarded it as a world of living organisms we should be using a still higher and less empty category ; for substance, quality, and activity would now be united in a conception out of which they all issue, the activity being no longer regarded as an accident of the KANT AND HEGEL 97 substance or matter, and quality being no longer a mysterious attribute of substance. L- It is evident that we cannot apply this or that category at will. Specific categories seem, as it were, to be embodied in all that we experience. By no mere arbitrary process of thought can I make a piece of stone into a living organism or vice versa. I can, how- ever, deliberately abstract from what the living organism really is, and regard it as simply a material system. This, indeed, is what the mechanistic theory of life invites me to do. I can also abstract from what the stone is, and regard it as simply a patch of colour. This, or something like this, was what Berkeley and Hume invited us to do, pointing out that the stone, as a substance outside us, is only a metaphysical product of our imagination, and that all that is really experienced is a patch of colour. But, as Kant showed in principle, we cannot thus divest our world of its meaning : we cannot reduce higher to lower categories, and thus explain the higher away : we find that the higher categories are embodied in the very texture of our experience. 98 BIOLOGY AND PHYSICAL SCIENCES When we examine the process of know- ledge itself we find that it is a progressive defining of our experience in terms of funda- mental conceptions or categories : also a gradual passing from lower, more abstract or indefinite conceptions to higher, more con- crete or definite ones. This is the course of all scientific investigation. It is only with infinite travail and pains that our experience gradually defines itself in terms of higher and more definite conceptions. A living organism is not given to us complete in thought all at once : it only gradually reveals itself more and more definitely in the course of long and arduous biological investigation. It is the same on a lower plane for the physical world, or for the mathematical world of abstract form and quantitative relations. But from the very nature of the categories or funda- mental conceptions themselves all true know- ledge must be a gradual revelation of the lower or more abstract in terms of the higher or more concrete aspects of reality ; and as the conception of organism is a higher and more concrete conception than that of matter and energy, science must ultimately aim at SIGNIFICANCE OF EVOLUTION 99 gradually interpreting the physical world of matter and energy in terms of the biological conception of organism. No lower claim than this will satisfy the ideals of biological investi- gation : of this we may be well assured. At the time of Kant and his immediate successors biology had hardly begun to be conscious of her strength. Living organisms seemed, as it were, to be at the best only dotted about here and there in the midst of a totally foreign physical universe. Kant assigned to them a very doubtful place in his philosophy, and Hegel in his Philosophy of Nature represented Nature as a sort of waste in which any and every kind of existence is strewed about indiscriminately — a conception repugnant to true science. Meanwhile the advance of the natural sciences has pro- foundly changed our outlook on Nature. First and foremost we have come to realise the fact of evolution. The true significance of this fact is a very different one from what is still very generally supposed. At • first evolution appeared in popular thought, em- bodied, for instance, in the writings of Herbert Spe^ce^, as a derivation of the 100 BIOLOGY AND PHYSICAL SCIENCES organic from the inorganic. We have seen already, however, that, evolution or no evolu- tion, there is not the remotest possibility of deriving the organic from the inorganic. Evolution, therefore, takes on a very different significance. In tracing life back and back towards what appears at first to be the in- organic we are not seeking to reduce the organic to the inorganic, but the inorganic to the organic. The apparently indefinite microscopical aggregations of formless colloid material — * sarcode ' or ' protoplasm ' — which were at first taken for the origins of life from the inorganic, have gradually turned out to be definite living organisms. But biology will not stop at these : for they must have been evolved from something more primitive. She will gradually push her advance victori- ously further and further into the domain of the apparently inorganic. The premonitory signs of this advance are not lacking. For nearly a century — since the days of John Dalton — the chemical atom was the ultimate term of physical and chemical investigation. The world seemed to be resolved into a world of atoms, in THE WORLD OF ATOMS 101 which, as du Bois Reymond pointed out, there was no place for life in any such sense as that which I have endeavoured to depict in this lecture. Recent discoveries in physics and chemistry have, however, completely shattered this conception, and with it that of matter and energy. We now see physicists and chemists groping after biological ideas. No one can yet tell what conceptions will emerge from the ruins of the atomic theory ; but it is at least evident that the extension of biological conceptions to the whole of Nature may be much nearer than seemed conceivable even a few years ago. When the day of that extension comes the physical and chemical world as we now conceive it — the world of atoms and energy — will be recognised as no- thing but an appearance, though for practical purposes it will still remain very useful. It will stand fully confessed as a world of abstractions like that of the pure mathemati- cians. Meanwhile it is already a world of abstractions to the biologist who has faith in the principle of evolution and also in the fundamental conception of the living organism. g2 102 BIOLOGY AND PHYSICAL SCIENCES To one point with reference to the bio- logical conception of a living organism no re- ference has yet been made. Living organisms always, or nearly always, appear to be marvel- lously ' adapted ' to their physical environ- ment. Yet this adaptation is not of the essence of the biological conception of an organism. We know, also, that organisms may develop which, in one way or another, are so misshapen or defective that they cannot survive, though they have all the essential characteristics of organisms. They maintain their existences as organisms for a short time, blindly struggling, as it were, to preserve the defects which make them in- capable of surviving. Organic life is ' blind ' : each organism blindly struggles to maintain its own exist- ence or that of its species. We can only explain the actual marvellous and intricate ' teleological ' adaptation of organism and physical environment by the fact that, as pointed out by Darwin and Wallace, those organisms which are not so adapted must disappear. Even if we could see far enough to be able to regard as organic the whole of THE STRUGGLE BETWEEN ORGANISMS 103 what appears as inorganic, the entire world would still appear as a blind struggle between different organisms. Of this conflict, whether we regard it as conflict between organisms themselves, or between organisms and physical environment, we can give no biological inter- pretation, and are thus forced back on a physical interpretation. From the standpoint of ideal biology organism and environment would be one. The organism would be not something in a more or less foreign environment, but in its own environment, which it has grown in, and which has been part of its very nature from the outset. Of the actual foreignness or imperfection in the environment biology as such can give no account. This discussion brings us to the subject of the last lecture. In the higher organisms, at least, we find distinct evidence of a quite new factor — consciousness. A conscious organism is, as it were, fighting the inorganic world, not blindly but with the weapons of that inorganic world itself. It answers blow with counter- blow, and physical force with counter-force. The conscious organism is aware of the inor- 104 BIOLOGY AND PHYSICAL SCIENCES ganic world as such, and reacts as in presence of that world, whether it be real or unreal. In concluding this lecture let us survey the progress made in our discussion. We have seen that the idea of the physical universe as a world of self-existent matter and energy is only a temporary working hypothesis by means of which we are able to introduce a certain amount of order and coherence into a large part of our experience. The fact that, as shown in the last lecture, this hypothesis breaks down in connection with the pheno- mena of life need not, therefore, puzzle us. The phenomena of life involve another and radically different conception of reality, and I have endeavoured to define this conception, and point out that it is actually used as a working hypothesis by biologists, and that by its means we introduce order and intelligibility into biology, whereas there is no such order or intelligibility if the mechanistic theory of life be adopted. The idea of life is nearer to reality than the ideas of matter and energy, and therefore the presupposition of ideal biology is that inorganic can ultimately be resolved into organic phenomena, and that PHYSICAL AND BIOLOGICAL REALITY 105 the physical world is thus only the appearance of a deeper reality which is as yet hidden from our distinct vision, and can only be seen dimly with the eye of scientific faith. We have seen, finally, that the ideal biological world is never completely realised. LECTURE IV PERSONALITY In the previous lectures I have endeavoured to follow out what is involved in our experi- ence of living organisms looked at from a purely biological standpoint. Actually, how- ever, the higher organisms display characters which do not belong to the conception of them as mere organisms : for they are conscious — in conscious relations of perception and active response with their environment. Let us try to realise more clearly what is involved in the conception of a conscious organism, or person. From the discussion in the previous lecture it is evident that we can- not mean an organism lighted up, as it were, by flashes of consciousness : for isolated flashes of consciousness, as Kant showed, do not exist We must therefore put entirely out of court the theory that conscious life is simply a series 106 CONSCIOUS ORGANISMS 107 of isolated states of consciousness which are the mysterious accompaniments of certain physical and chemical processes in the brain. Such a theory is merely a combination of obsolete philosophy with equally obsolete physiology. Nor can a conscious organism mean that the organism, or its brain, is the ' seat ' of an independent and self-existent soul or Ego, of which consciousness is the activity. This theory involves the impossibilities which Hume and Kant so clearly pointed out. Nor, finally, is a conscious organism conscious merely of its own organic activity. It is certainly conscious generally of its own or- ganic activity, though of the details of this activity it is either totally unconscious, or only dimly conscious. On the other hand, it i