If we now look closely at the two doctrines, CHAP, i REALISM AND IDEALISM 17 we shall discover in them a common postulate, which we may formulate thus: perboth imply an cefition has a wholly speculative interest; erroneous.., _...,,.
postulate, it is pure knowledge. The whole disviz.,that. * J • perception cussion turns upon the importance to be has merely a.,, *,,, speculative attnbuted to this knowledge as com pared with scientific knowledge. The one doctrine starts from the order required by science, and sees in perception only a confused and provisional science. The other puts perception in the first place, erects it into an absolute, and then holds science to be a symbolic expression of the real. But, for both parties, to perceive means above all to know.
Now it is just this postulate that we dispute. Even the most superficial examination of the structure of the nervous system in the animal series gives it the lie. And it is not possible to accept it without profoundly obscuring the threefold problem of matter, consciousness, and their relation.
For if we follow, step by step, the progress of external perception from the monera to the higher vertebrates, we find that living matter, But facts.
reaiiy suggest even as a simple mass of protoplasm, is the opposite,,..,,,., view. already irritable and contractile, that Evidence bom the it is open to the influence of external structure and.
evolution of stimulation, and answers to it by mechanical, physical, and chemical re actions. As we rise in the organic series, we find a division of physiological labour. Nerve cells l8 MATTER AND MEMORY CHAP. I appear, are diversified, tend to group themselves into a system; at the same time, the animal reacts by more varied movements to external stimulation. But even when the stimulation re ceived is not at once prolonged into movement, it appears merely to await its occasion; and the same impression, which makes the organism aware of changes in the environment, determines it or pre pares it to adapt itself to them. No doubt there is in the higher vertebrates a radical distinction between pure automatism, of which the seat is mainly in the spinal cord, and voluntary activity, which requires the intervention of the brain. It might be imagined that the impression received, instead of expanding into more movements, spiritualizes itself into consciousness. But as soon as we compare the structure of the spinal cord with that of the brain, we are bound to infer that there is merely a difference of complication, and not a difference in kind, between the functions of the brain and the reflex activity of the medullary system. For what takes place in reflex action? The centripetal movement communicated by the stimulus is reflected at once, by the intermediary of the nerve centres of the spinal cord, in a centrifugal movement determining a muscular contraction.
In what, on the other hand, does the function of the cerebral system consist? The peripheral excita tion, instead of proceeding directly to the motor- cells of the spinal cord and impressing on the muscle a necessary contraction, mounts first to the brain, CHAP, i THE CHOICE OF IMAGES 1 9 and then descends again to the very same motor cells of the spinal cord which intervened in the reflex action. Now what has it gained by this round about course, and what did it seek in the so-called sensory cells of the cerebral cortex? I do not un derstand, I shall never understand, that it draws thence a miraculous power of changing itself into a representation of things; and moreover, I hold this hypothesis to be useless, as will shortly ap pear. But what I do see clearly is that the cells of the various regions of the cortex which are termed sensory, — cells interposed between the terminal branches of the centripetal fibres and the motor cells of the Rolandic area, — allow the stimulation received to reach at will this or that motor mechan ism of the spinal cord, and so to choose its effect. The more these intercalated cells are multiplied and the more they project amoeboid prolonga tions which are probably capable of approaching each other in various ways, the more numerous and more varied will be the paths capable of opening to one and the same disturbance from the periphery, and, consequently, the more systems of movements will there be among which one and the same stimulation will allow of choice. In our opinion, then, the brain is no more than a kind of central telephonic exchange: its office is to allow communication, or to delay it. It adds nothing to what it receives; but, as all the organs of perception send it to their ultimate prolongations, and as all the motor mechanisms of the spinal 20 MATTER AND MEMORY CHAP, i cord and of the medulla oblongata have in it their accredited representatives, it really constitutes a centre, where the peripheral excitation gets into relation with this or that motor mechanism, chosen and no longer prescribed. On the other hand, as a great multitude of motor tracks can open simul taneously in this substance to one and the same excitation from the periphery, this disturbance may subdivide to any extent, and consequently dissipate itself in innumerable motor reactions which are merely nascent. Hence the office of the brain is sometimes to conduct the movement received to a chosen organ of reaction, and sometimes to open to this movement the totality of the motor tracks, so that it may manifest there all the potential reactions with which it is charged, and may divide and so disperse. In other words, the brain appears to us to be an instrument of analysis in regard to the movement received, and an instrument of selec tion in regard to the movement executed. But, in the one case as in the other, its office is limited to the transmission and division of movement. And no more in the higher centres of the cortex than in the spinal cord do the nervous elements work with a view to knowledge: they do but indicate a number of possible actions at once, or organize one of them.
That is to say that the nervous system is in no sense an apparatus which may serve to fabricate, or even to prepare, representations. Its function is to receive stimulation, to pro vide motor apparatus, CHAP, i THE CHOICE OF IMAGES 21 and to present the largest possible number of these apparatuses to a given stimulus. The more it develops, the more numerous and the more distant are the points of space which it brings into relation with ever more complex motor mechan isms. In this way the scope which it allows to our action enlarges: its growing perfection consists in nothing else. But if the nervous system is thus constructed, from one end of the animal series to the other, in view of an action which is less and less necessary, must we not think that perception, of which the progress is regulated by that of the nervous system, is also entirely directed towards action, and not towards pure knowledge? And, if this be so, is not the growing richness of this perception likely to symbolize the wider range of indetermination left to the choice of the living being in its conduct with regard to things? Let us start, then, from this indetermination as from the true principle, and try whether we cannot deduce from it the possibility, and even the necessity, of conscious perception. In other words, let us posit that system of closely-linked images which we call the material world, and imagine here and there, within the system, centres of real action, represented by living matter: what we mean to prove is that there must be, ranged round each one of these centres, images that are subordinated to its posi tion and variable with it; that conscious percep tion is bound to occur, and that, moreover, it is possible to understand how it arises.
22 MATTER AND MEMORY CHAP, i We note, in the first place, that a strict law con nects the amount of conscious perception with the intensity of action at the disposal of the st°ar7efr?msthe living being. If our hypothesis is well founded, this perception appears at the precise moment when a stimulation re- ceived by matter is not prolonged into a necessary action. In the case of a rudi mentary organism, it is true that immediate contact with the object which interests it is necessary to pro duce the stimulation, and that reaction can then hardly be delayed. Thus, in the lower organ isms, touch is active and passive at one and the same time, enabling them to recognize their prey and seize it, to feel a danger and make the effort to avoid it. The various prolongations of the pro tozoa, the ambulacra of the echinodermata, are organs of movement as well as of tactile percep tion; the stinging apparatus of the coelenterata is an instrument of perception as well as a means of defence. In a word, the more immediate the reaction is compelled to be, the more must percep tion resemble a mere contact; and the complete process of perception and of reaction can then hardly be distinguished from a mechanical impul sion followed by a necessary movement. But in the measure that the reaction becomes more un certain, and allows more room for suspense, does the distance increase at which the animal is sensible of the action of that which interests it. By sight, by hearing, it enters into relation with an CHAP, i THE CHOICE OF IMAGES 23 ever greater number of things, and is subject to more and more distant influences; and, whether these objects promise an advantage or threaten a danger, both promises and threats defer the date of their fulfilment. The degree of independence of which a living being is master, or, as we shall say, the zone of indetermination which surrounds its activity, allows, then, of an a 'priori estimate of the number and the distance of the things with which it is in relation. Whatever this relation may be, whatever be the inner nature of percep tion, we can affirm that its amplitude gives the exact measure of the indetermination of the act which is to follow. So that we can formulate this law: perception is master of space in the exact measure in which action is master of time.
But why does this relation of the organism to more or less distant objects take the particular form what then °f conscious perception? We have Sonsdous-* examined what takes place in the or- p?eiiLinary ganized body, we have seen movements hmts- transmitted or inhibited, metamor phosed into accomplished actions or broken up into nascent actions. These movements appear to us to concern action, and action alone; they remain absolutely foreign to the process of repre sentation. We then considered action itself, and the indetermination which surrounds it and is implied in the structure of the nervous system, — an indetermination to which this system seems to point much more than to representation.
24 MATTER AND MEMORY CHAP. I From this indetermination, accepted as a fact, we have been able to infer the necessity of a perception, that is to say, of a variable relation between the living being and the more or less distant influence of the objects which interest it. How is it that this perception is consciousness, and why does everything happen as if this con sciousness were born of the internal movements of the cerebral substance?
To answer this question, we will first simplify considerably the conditions under which conscious perception takes place. In fact, there is no perception which is not full of memories. With the immediate and present data of our senses we mingle a thousand details out of our past experience. In most cases these memories supplant our actual perceptions, of which we then retain only a few hints, thus using them merely as ' signs ' that recall to us former images. The convenience and the rapidity of perception are bought at this price; but hence also springs every kind of illusion. Let us, for the purposes of study, substitute for this perception, impregnated with our past, a per ception that a consciousness would have if it were supposed to be ripe and full-grown, yet confined to the present and absorbed, to the exclusion of all else, in the task of moulding itself upon the external object. — It may be urged that this is an arbitrary hypothesis, and that such an ideal perception, obtained by the CHA*. I THE CHOICE OF IMAGES 25 elimination of individual accidents, has no corre spondence with reality. — But we hope to show that the individual accidents are merely grafted on to this impersonal perception, which is at the very root of our knowledge of things; and that just because philosophers have overlooked it, because they have not distinguished it from that which memory adds to or subtracts from it, they have taken perception as a whole for a kind of interior and subjective vision, which would then differ from memory only by its greater intensity. This will be our first hypothesis. But it leads naturally to another. However brief we suppose any perception to be, it always occupies a certain duration, and involves consequently an effort of memory which prolongs one into another a plurality of moments. As we shall endeavour to show, even the 'subjectivity' of sensible quali ties consists above all else in a kind of contraction of the real, effected by our memory. In short, memory in these two forms, covering as it does with a cloak of recollections a core of immediate percep tion, and also contracting a number of external moments into a single internal moment, con stitutes the principal share of individual con sciousness in perception, the subjective side of the knowledge of things; and, since we must neglect this share in order to make our idea clearer, we shall go too far along the path we have chosen. But we shall only have to retrace our steps and to correct, especially by bringing memory 26 MATTER AND MEMORY CHAP, i back again, whatever may be excessive in our conclusions. What follows, therefore, must be regarded as only a schematic rendering, and we ask that perception should be provisionally understood to mean not my concrete and com plex perception — that which is enlarged by memories and offers always a certain breadth of duration — but a pure perception, I mean a percep tion which exists in theory rather than in fact and would be possessed by a being placed where I am, living as I live, but absorbed in the present and capable, by giving up every form of memory, of obtaining a vision of matter both immediate and instantaneous. Adopting this hypothesis, let us consider how conscious per ception may be explained.
To deduce consciousness would be, indeed, a bold undertaking; but it is really not necessary here, be- cause by positing the material world we as- sume an aggregate of images, and more- reflectedfrom over because it is impossible to assume thoiuh by a anything else. No theory of matter escapes mirror. ^his necessity. Reduce matter to atoms in motion: these atoms, though denuded of physical qualities, are determined only in relation to an eventual vision and an eventual contact, the one without light and the other without materiality. Condense atoms into centres of force, dissolve them into vortices revolving in a continuous fluid: this fluid, these movements, these centres, can themselves be determined only in relation to an CHAP, i THE CHOICE OF IMAGES 27 impotent touch, an ineffectual impulsion, a colour less light; they are still images. It is true that an image may be without being perceived; it may be present without being represented; and the distance between these two terms, presence and representation, seems just to measure the interval between matter itself and our con scious perception of matter. But let us examine the point more closely, and see in what this difference consists. If there were more in the second term than in the first, if, in order to pass from presence to representation, it were necessary to add something, the barrier would indeed be insuperable, and the passage from matter to perception would remain wrapt in impenetrable mystery. It would not be the same if it were possible to pass from the first term to the second by way of diminution, and if the representation of an image were less than its presence; for it would then suffice that the images present should be compelled to abandon some thing of themselves in order that their mere pre sence should convert them into representations. Now, here is the image which I call a material object; I have the representation of it. How comes it that it does not appear to be in itself that which it is for me? It is because, being bound up with all other images, it is continued in those which follow it, just as it prolonged those which pre ceded it. To transform its existence into represen tation, it would be enough to suppress what follows it, what precedes it, and also all that fills it, and to 28 MATTER AND MEMORY CHAP, i retain only its external crust, its superficial skin. That which distinguishes it as a present image, as an objective reality, from a represented image is the necessity which obliges it to act through every one of its points upon all the points of all other images, to transmit the whole of what it receives, to oppose to every action an equal and contrary reaction, to be, in short, merely a road by which pass, in every direction, the modifications propagated through out the immensity of the universe. I should con vert it into representation if I could isolate it, especially if I could isolate its shell. Represen tation is there, but always virtual — being neutral ized, at the very moment when it might become actual, by the obligation to continue itself and to lose itself in something else. To obtain this con version from the virtual to the actual it would be necessary, not to throw more light on the object, but on the contrary to obscure some of its aspects, to diminish it by the greater part of itself, so that the remainder, instead of being encased in its sur roundings as a thing, should detach itself from them as a picture. Now if living beings are, within the uni verse, just ' centres of indetermination,' and if the degree of this indetermination is measured by the number and rank of their functions, we can con ceive that their mere presence is equivalent to the suppression of all those parts of objects in which their functions find no interest. They allow to pass through them, so to speak, those external in fluences which are indifferent to them; the others CHAP, i THE CHOICE OF IMAGES 2Q isolated, become ' perceptions ' by their very isolation. Everything thus happens for us as though we reflected back to surfaces the light which emanates from them, the light which, had it passed on unopposed, would never have been revealed. The images which surround us will appear to turn towards our body the side, emphasized by the light upon it, which interests our body. They will detach from themselves that which we have arrested on its way, that which we are capable of influencing. Indifferent to each other because of the radical mechanism which binds them to gether, they present each to the others all their sides at once: which means that they act and react mutually by all their elements, and that none of them perceives or is perceived consciously. Suppose, on the contrary, that they encounter some where a certain spontaneity of reaction: their action is so far diminished, and this diminution of their action is just the representation which we have of them. Our representation of things would thus arise from the fact that they are thrown back and reflected by our freedom.
When a ray of light passes from one medium into another, it usually traverses it with a change of direction. But the respective den sities of the two media may be such that, for a given angle of incidence, refraction is no longer possible. Then we have total reflexion. The luminous point gives rise to a virtual image which symbolizes, so to speak, the fact that the luminous 3O MATTER AND MEMORY CHAP, i rays cannot pursue their way. Perception is just a phenomenon of the same kind. That which is given is the totality of the images of the material world, with the totality of their internal elements. But if we suppose centres of real, that is to say of spontaneous, activity, the rays which reach it, and which interest that activity, instead of pass ing through those centres, will appear to be re flected and thus to indicate the outlines of the object which emits them. There is nothing positive here, nothing added to the image, nothing new. The objects merely abandon something of their real action in order to manifest their virtual action — that is to say, in the main, the eventual influence of the living being upon them. Per ception therefore resembles those phenomena of reflexion which result from an impeded refraction; it is like an effect of mirage.