Chapter 1: Of the Selection of Images

Chapter 1: Of The Selection of Images for Conscious Presentation. What Our Body Means and Does.

We will assume for the moment that we know nothing of theories of matter and theories of spirit, nothing of the discussions as to the reality or ideality of the external world. Here I am in the presence of images, in the vaguest sense of the word, images perceived when my senses are opened to them, unperceived when they are closed. All these images act and react upon one another in all their elementary parts according to constant laws which I call laws of nature, and, as a perfect knowledge of these laws would probably allow us to calculate and to foresee what will happen in each of these images, the future of the images must be contained in their present and will add to them nothing new.

Yet there is one of them which is distinct from all the others, in that I do not know it only from without by perceptions, but from within by affections: it is my body. I examine the conditions in which these affections are produced: I find that they always interpose themselves between the excitations that I receive from without and the movements which I am about to execute, as though they had some undefined influence on the final issue. I pass in review my different affections: it seems to me that each of them contains, after its kind, an invitation to act, with at the same time leave to wait and even to do nothing. I look closer: I find movements begun, but not executed, the indication of a more or less useful decision, but not that constraint which precludes choice. I call up, I compare my recollections: I remember that everywhere, in the organic world, I have thought I saw this same sensibility appear at the very moment when nature, having conferred upon the living being the power of mobility in space, gives warning to the species, by means of sensation, of the general dangers which threaten it, leaving to the individual the precautions necessary for escaping from them. Lastly, I interrogate my consciousness as to the part which it plays in affection: consciousness replies that it is present indeed, in the form of feeling or of sensation, at all the steps in which I believe that I take the initiative, and that it fades and disappears as soon as my activity, by becoming automatic, shows that consciousness is no longer needed. Therefore, either all these appearances are deceptive, or the act in which the affective state issues is not one of those which might be rigorously deduced from antecedent phenomena, as a movement from a movement; and, hence, it really adds something new to the universe and to its history. Let us hold to the appearances; I will formulate purely and simply what I feel and what I see: All seems to take place as if, in this aggregate of images which I call the universe, nothing really new could happen except through the medium of certain particular images, the type of which is furnished me by my body.

I pass now to the study, in bodies similar to my own, of the structure of that particular image which I call my body. I perceive afferent nerves which transmit a disturbance to the nerve centers; then efferent nerves which start from the center, conduct the disturbance to the periphery, and set in motion parts of the body or the body as a whole. I question the physiologist and the psychologist as to the purpose of both kinds. They answer that, as the centrifugal movements of the nervous system can call forth a movement of the body or of parts of the body, so the centripetal movements, or at least some of them, give birth to the representation of the external world. What are we to think of this?

The afferent nerves are images, the brain is an image, the disturbance traveling through the sensory nerves and propagated in the brain is an image too. If the image which I term cerebral disturbance really begot external images, it would contain them in one way or another, and the representation of the whole material universe would be implied in that of this molecular movement. Now to state this proposition is enough to show its absurdity. The brain is part of the material world; the material world is not part of the brain. Eliminate the image which bears the name material world, and you destroy at the same time the brain and the cerebral disturbance which are parts of it. Suppose, on the contrary, that these two images, the brain and the cerebral disturbance, vanish: ex hypothesi you efface only these, that is to say very little, an insignificant detail from an immense picture. The picture in its totality, that is to say the whole universe, remains. To make of the brain the condition on which the whole image depends is, in truth, a contradiction in terms, since the brain is by hypothesis a part of this image. Neither nerves nor nerve centers can, then, condition the image of the universe.

Let us consider this last point. Here are external images, then my body, and, lastly, the changes brought about by my body in the surrounding images. I see plainly how external images influence the image that I call my body: they transmit movement to it. And I also see how this body influences external images: it gives back movement to them. My body is, then, in the aggregate of the material world, an image which acts like other images, receiving and giving back movement, with, perhaps, this difference only, that my body appears to choose, within certain limits, the manner in which it shall restore what it receives. But how could my body in general, and my nervous system in particular, beget the whole or a part of my representation of the universe? You may say that my body is matter, or that it is an image: the word is of no importance. If it is matter, it is a part of the material world; and the material world, consequently, exists around it and without it. If it is an image, that image can give but what has been put into it, and since it is, by hypothesis, the image of my body only, it would be absurd to expect to get from it that of the whole universe. My body, an object destined to move other objects, is, then, a center of action; it cannot give birth to a representation.

But if my body is an object capable of exercising a genuine and therefore a new action upon the surrounding objects, it must occupy a privileged position in regard to them. As a rule, any image influences other images in a manner which is determined, and even calculable, through what are called the laws of nature. As it has not to choose, so neither has it any need to explore the region round about it, nor to try its hand at several merely eventual actions. The necessary action will take place automatically, when its hour strikes. But I have supposed that the office of the image which I call my body was to exercise on other images a real influence, and, consequently, to decide which step to take among several which are all materially possible. And since these steps are probably suggested to it by the greater or lesser advantage which it can derive from the surrounding images, these images must display in some way, upon the aspect which they present to my body, the profit which my body can gain from them. In fact, I note that the size, shape, even the color, of external objects is modified as my body approaches or recedes from them; that the strength of an odor, the intensity of a sound, increases or diminishes with distance; finally, that this very distance represents, above all, the measure in which surrounding bodies are insured, in some way, against the immediate action of my body. To the degree that my horizon widens, the images which surround me seem to be painted upon a more uniform background and become to me more indifferent. The more I narrow this horizon, the more the objects which it circumscribes space themselves out distinctly according to the greater or lesser ease with which my body can touch and move them. They send back, then, to my body, as would a mirror, its eventual influence; they take rank in an order corresponding to the growing or decreasing powers of my body. The objects which surround my body reflect its possible action upon them.

I will now, without touching the other images, modify slightly that image which I call my body. In this image I cut asunder, in thought, all the afferent nerves of the cerebro-spinal system. What will happen? A few cuts with the scalpel have severed a few bundles of fibres: the rest of the universe, and even the rest of my body, remain what they were before. The change effected is therefore insignificant. As a matter of fact, my perception has entirely vanished. Let us consider more closely what has just occurred. Here are the images which compose the universe in general, then those which are near to my body, and finally my body itself. In this last image the habitual office of the centripetal nerves is to transmit movements to the brain and to the cord; the centrifugal nerves send back this movement to the periphery. Sectioning of the centripetal nerves can, therefore, produce only one intelligible effect: that is, to interrupt the current which goes from the periphery to the periphery by way of the center, and, consequently, to make it impossible for my body to extract, from among all the things which surround it, the quantity and quality of movement necessary in order to act upon them. Here is something which concerns action, and action alone. Yet it is my perception which has vanished. What does this mean, if not that my perception displays, in the midst of the image world, as would their outward reflection or shadow, the eventual or possible actions of my body? Now the system of images in which the scalpel has effected only an insignificant change is what is generally called the material world; and, on the other hand, that which has just vanished is "my perception" of matter. Whence, provisionally, these two definitions: call matter the aggregate of images, and perception of matter these same images referred to the eventual action of one particular image, my body.

Let us go more deeply into this reference. I consider my body, with its centripetal and centrifugal nerves, with its nerve centers. I know that external objects make in the afferent nerves a disturbance which passes onward to the centers, that the centers are the theater of very varied molecular movements, and that these movements depend on the nature and position of the objects. Change the objects, or modify their relation to my body, and everything is changed in the interior movements of my perceptive centers. But everything is also changed in "my perception." My perception is, then, a function of these molecular movements; it depends upon them. But how does it depend upon them? It will perhaps be said that it translates them, and that, in the main, I represent to myself nothing but the molecular movements of cerebral substance. But how should this have any meaning, since the image of the nervous system and of its internal movements is only, by hypothesis, that of a certain material object, whereas I represent to myself the whole material universe? It is true that many philosophers attempt to evade the difficulty. They show us a brain, analogous in its essence to the rest of the material universe, an image, consequently, if the universe is an image. Then, since they want the internal movements of this brain to create or determine the representation of the whole material world - an image infinitely greater than that of the cerebral vibrations - they maintain that these molecular movements, and movement in general, are not images like others, but something which is either more or less than an image - in any case is of another nature than an image - and from which representation will issue as by a miracle. Thus matter is made into something radically different from representation, something of which, consequently, we have no image; over against it they place a consciousness empty of images, of which we are unable to form any idea; lastly, to fill consciousness, they invent an incomprehensible action of this formless matter upon this matterless thought. But the truth is that the movements of matter are very clear, regarded as images, and that there is no need to look in movement for anything more than what we see in it. The sole difficulty would consist in bringing forth from these very particular images the infinite variety of representations; but why seek to do so, since we all agree that the cerebral vibrations are contained in the material world, and that these images, consequently, are only a part of the representation? What then are these movements, and what part do these particular images play in the representation of the whole? The answer is obvious: they are, within my body, the movements intended to prepare, while beginning it, the reaction of my body to the action of external objects. Images themselves cannot create images; but they indicate at each moment, like a compass that is being moved about, the position of a certain given image, my body, in relation to the surrounding images. In the totality of representation they are very little; but they are of capital importance for that part of representation which I call my body, since they foreshadow at each successive moment its virtual acts. There is, then, only a difference of degree - there can be no difference in kind - between what is called the perceptive faculty of the brain and the reflex functions of the spinal cord. The cord transforms into movements the stimulation received; the brain prolongs them into reactions which are merely nascent; but, in the one case as in the other, the function of the nerve substance is to conduct, to coordinate, or to inhibit movements. How then does it come about that "my perception of the universe" appears to depend upon the internal movements of the cerebral substance, to change when they vary, and to vanish when they cease?

The difficulty of this problem is mainly due to the fact that the grey matter and its modifications are regarded as things which are sufficient to themselves and might be isolated from the rest of the universe. Materialists and dualists are fundamentally agreed on this point. They consider certain molecular movements of the cerebral matter apart: then, some see in our conscious perception a phosphorescence which follows these movements and illuminates their track; for others, our perceptions succeed each other like an unwinding scroll in a consciousness which expresses continuously, in its own way, the molecular vibrations of the cortical substance: in the one case, as in the other, our perception is supposed to translate or to picture the states of our nervous system. But is it possible to conceive the nervous system as living apart from the organism which nourishes it, from the atmosphere in which the organism breathes, from the earth which that atmosphere envelopes, from the sun round which the earth revolves? More generally, does not the fiction of an isolated material object imply a kind of absurdity, since this object borrows its physical properties from the relations which it maintains with all others, and owes each of its determinations, and, consequently, its very existence, to the place which it occupies in the universe as a whole? Let us no longer say, then, that our perceptions depend simply upon the molecular movements of the cerebral mass. We must say rather that they vary with them, but that these movements themselves remain inseparably bound up with the rest of the material world. The question, then, is not only how our perceptions are connected with the modifications of the grey matter. The problem widens, and can also be put in much clearer terms.

It might be stated as follows: Here is a system of images which I term my perception of the universe, and which may be entirely altered by a very slight change in a certain privileged image - my body. This image occupies the center; by it all the others are conditioned; at each of its movements everything changes, as though by a turn of a kaleidoscope. Here, on the other hand, are the same images, but referred each one to itself, influencing each other no doubt, but in such a manner that the effect is always in proportion to the cause: this is what I term the universe. The question is: how can these two systems coexist, and why are the same images relatively invariable in the universe and infinitely variable in perception? The problem at issue between realism and idealism, perhaps even between materialism and spiritualism, should be stated, then, it seems to us, in the following terms: How is it that the same images can belong at the same time to two different systems: one in which each image varies for itself and in the well-defined measure that it is patient of the real action of surrounding images; and another in which all images change for a single image and in the varying measure that they reflect the eventual action of this privileged image?

Every image is within certain images and without others; but of the aggregate of images we cannot say that it is within us or without us, since interiority and exteriority are only relations among images. To ask whether the universe exists only in our thought, or outside of our thought, is to put the problem in terms that are insoluble, even if we suppose them to be intelligible; it is to condemn ourselves to a barren discussion, in which the terms thought, being, universe, will always be taken on either hand in entirely different senses. To settle the matter, we must first find a common ground where combatants may meet; and since on both sides it is agreed that we can only grasp things in the form of images, we must state the problem in terms of images, and of images alone. Now no philosophical doctrine denies that the same images can enter at the same time into two distinct systems, one belonging to science, wherein each image, related only to itself, possesses an absolute value; and the other, the world of consciousness, wherein all the images depend on a central image, our body, the variations of which they follow. The question raised between realism and idealism then becomes quite clear: what are the relations which these two systems of images maintain with each other? And it is easy to see that subjective idealism consists in deriving the first system from the second, materialistic realism in deriving the second from the first.

The realist starts, in fact, from the universe, that is to say from an aggregate of images governed, as to their mutual relations, by fixed laws, in which effects are in strict proportion to their causes, and of which the character is an absence of center, all the images unfolding on one and the same plane indefinitely prolonged. But he is at once bound to recognize that, besides this system, there are perceptions, that is to say, systems in which these same images seem to depend on a single one among them, around which they range themselves on different planes, so as to be wholly transformed by the slightest modification of this central image. Now this perception is just what the idealist starts from: in the system of images which he adopts there is a privileged image, his body, by which the other images are conditioned. But as soon as he attempts to connect the present with the past and to foretell the future, he is obliged to abandon this central position, to replace all the images on the same plane, to suppose that they no longer vary for him, but for themselves; and to treat them as though they made part of a system in which every change gives the exact measure of its cause. On this condition alone a science of the universe becomes possible; and, since this science exists, since it succeeds in foreseeing the future, its fundamental hypothesis cannot be arbitrary. The first system alone is given to present experience; but we believe in the second, if only because we affirm the continuity of the past, present and future. Thus in idealism, as in realism, we posit one of the two systems and seek to deduce the other from it.

But in this deduction neither realism nor idealism can succeed, because neither of the two systems of images is implied in the other, and each of them is sufficient to itself. If you posit the system of images which has no center, and in which each element possesses its absolute dimensions and value, I see no reason why to this system should accrue a second, in which each image has an undetermined value, subject to all the vicissitudes of a central image. You must, then, to engender perception, conjure up some deus ex machina, such as the materialistic hypothesis of the epiphenomenal consciousness, whereby you choose, among all the images that vary absolutely and that you posited to begin with, the one which we term our brain - conferring on the internal states of this image the singular and inexplicable privilege of adding to itself a reproduction, this time relative and variable, of all the others. It is true that you afterwards pretend to attach no importance to this representation, to see in it a mere phosphorescence which the cerebral vibrations leave behind them: as if the cerebral matter and cerebral vibrations, set in the images which compose this representation, could be of another nature than they are! All realism is thus bound to make perception an accident, and, consequently, a mystery. But, inversely, if you posit a system of unstable images disposed about a privileged center, and profoundly modified by trifling displacements of this center, you begin by excluding the order of nature, that order which is indifferent to the point at which we take our stand and to the particular end from which we begin. You will have to bring back this order by conjuring up in your turn a deus ex machina; I mean that you will have to assume, by an arbitrary hypothesis, some sort of pre-established harmony between things and mind, or, at least (to use Kant's terms), between sense and understanding. It is science now that will become an accident, and its success a mystery. You cannot, then, deduce the first system of images from the second, nor the second from the first; and these two antagonistic doctrines, realism and idealism, as soon as they decide to enter the same lists, hurl themselves from opposite directions against the same obstacle.

If we now look closely at the two doctrines, we shall discover in them a common postulate, which we may formulate thus: perception has a wholly speculative interest; it is pure knowledge. The whole discussion turns upon the importance to be attributed to this knowledge as compared 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, even as a simple mass of protoplasm, is already irritable and contractile, that it is open to the influence of external stimulation, and answers to it by mechanical , physical and chemical reactions. As we rise in the organic series, we find a division of physiological labor. Nerve cells 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 received 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 prepares 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 centers 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 excitation, instead of proceeding directly to the motorcells of the spinal cord and impressing on the muscle a necessary contraction, mounts first to the brain, 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 roundabout course, and what did it seek in the so-called sensory cells of the cerebral cortex? I do not understand, 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 appear. 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 fibers and the motor cells of the Rolandic area - allow the stimulation received to reach at will this or that motor mechanism of the spinal cord, and so to choose its effect. The more these intercalated cells are multiplied and the more they project amoeboid prolongations 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 cord and of the medulla oblongata have in it their accredited representatives, it really constitutes a center, where the peripheral excitation gets into relation with this or that motor mechanism, chosen and no longer prescribed. Yet, as a great multitude of motor tracks can open simultaneously 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 tracts, 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 selection 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 centers 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 provide motor apparatus, 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 mechanisms. 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 toward action, and not toward 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, centers of real action, represented by living matter: what we mean to prove is that there must be, ranged round each one of these centers, images that are subordinated to its position and variable with it; that conscious perception is bound to occur, and that, moreover, it is possible to understand how it arises.

We note, in the first place, that a strict law connects the amount of conscious perception with the intensity of action at the disposal of the living being. If our hypothesis is well founded, this perception appears at the precise moment when a stimulation received by matter is not prolonged into a necessary action. In the case of a rudimentary organism, it is true that immediate contact with the object which interests it is necessary to produce the stimulation and that reaction can then hardly be delayed. Thus, in the lower organisms, 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 protozoa, the ambulacra of the echinodermata, are organs of movement as well as of tactile perception; 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 perception resemble a mere contact; and the complete process of perception and of reaction can then hardly be distinguished from a mechanical impulsion followed by a necessary movement. But in the measure that the reaction becomes more uncertain, 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 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 fulfillment. 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 perception, 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 of conscious perception? We have examined what takes place in the organized body, we have seen movements transmitted or inhibited, metamorphosed 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 representation. 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. From this indetermination, accepted as a fact, we have been able to infer the necessity of a perception, that is to say, 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 consciousness 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 perception 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 molding itself upon the external object. It may be urged that this is an arbitrary hypothesis, and that such an ideal perception, obtained by the elimination of individual accidents, has no correspondence 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 endeavor to show, even the "subjectivity" of sensible qualities 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 perception, and also contracting a number of external moments into a single internal moment, constitutes the principal share of individual consciousness 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 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 complex perception - that which is enlarged by memories and offers always a certain breadth of duration - but a pure perception. By this I mean a perception 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 perception may be explained. To deduce consciousness would be, indeed, a bold undertaking; but it is really not necessary here, because by positing the material world we assume an aggregate of images, and, moreover, because it is impossible to assume anything else. No theory of matter escapes this 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 centers of force, dissolve them into vortices revolving in a continuous fluid: this fluid, these movements, these centers, can themselves be determined only in relation to an impotent touch, an ineffectual impulsion, a colorless 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 conscious 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 wrapped 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 something of themselves in order that their mere presence should convert them into representations. Now, here is the image which I call a material object; I have the representation of it. How then does it 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 preceded it. To transform its existence into representation, it would be enough to suppress what follows it, what precedes it, and also all that fills it, and to 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 throughout the immensity of the universe. I should convert it into representation if I could isolate it, especially if I could isolate its shell. Representation is there, but always virtual - being neutralized, 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 conversion 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 surroundings as a thing, should detach itself from them as a picture. Now, if living beings are, within the universe, just "centers of indetermination," and if the degree of this indetermination is measured by the number and rank of their functions, we can conceive 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 influences which are indifferent to them; the others 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 toward 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 together, 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 somewhere 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 densities of the two media may be such that, for a given angle of incidence, refraction is no longer possible. Then we have total reflection. The luminous point gives rise to a virtual image which symbolizes, so to speak, the fact that the luminous 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 centers of real, that is to say of spontaneous, activity, the rays which reach it, and which interest that activity, instead of passing through those centers, will appear to be reflected 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 influence of the living being upon them. Perception therefore resembles those phenomena of reflexion which result from an impeded refraction; it is like an effect of mirage.

This is as much as to say that there is for images merely a difference of degree, and not of kind, between being and being consciously perceived. The reality of matter consists in the totality of its elements and of their actions of every kind. Our representation of matter is the measure of our possible action upon bodies: it results from the discarding of what has no interest for our needs, or more generally, for our functions. In one sense we might say that the perception of any unconscious material point whatever, in its instantaneousness, is infinitely greater and more complete than ours, since this point gathers and transmits the influences of all the points of the material universe, whereas our consciousness only attains to certain parts and to certain aspects of those parts. Consciousness - in regard to external perception - lies in just this choice. But there is, in this necessary poverty of our conscious perception, something that is positive, that foretells spirit: it is, in the etymological sense of the word, discernment.

The whole difficulty of the problem that occupies us comes from the fact that we imagine perception to be a kind of photographic view of things, taken from a fixed point by that special apparatus which is called an organ of perception - a photograph which would then be developed in the brain-matter by some unknown chemical and psychical process of elaboration. But is it not obvious that the photograph, if photograph there be, is already taken, already developed in the very heart of things and at all the points of space? No metaphysics, no physics even, can escape this conclusion. Build up the universe with atoms: each of them is subject to the action, variable in quantity and quality according to the distance, exerted on it by all material atoms. Bring in Faraday’s centers of force: the lines of force emitted in every direction from every center bring to bear upon each the influences of the whole material world. Call up the Leibnizian monads: each is the mirror of the universe. All philosophers, then, agree on this point. Only if, when we consider any other given place in the universe, we can regard the action of all matter as passing through it without resistance and without loss, and the photograph of the whole as translucent: here there is wanting behind the plate the black screen on which the image could be shown. Our "zones of indetermination" play in some sort the part of the screen. They add nothing to what is there; they effect merely this: that the real action passes through, the virtual action remains.

This is no hypothesis. We content ourselves with formulating data with which no theory of perception can dispense. For no philosopher can begin the study of external perception without assuming the possibility at least of a material world, that is to say, in the main, the virtual perception of all things. From this merely possible material mass he will then isolate the particular object which I call my body, and, in this body, centers of perception: he will show me the disturbance coming from a certain point in space, propagating itself along the nerves, and reaching the centers. But here I am confronted by a transformation scene from fairyland. The material world, which surrounds the body; the body, which shelters the brain; the brain, in which we distinguish centers; he abruptly dismisses, and, as by a magician's wand, he conjures up, as a thing entirely new the representation of what he began by postulating. This representation he drives out of space, so that it may have nothing in common with the matter from which he started. As for matter itself, he would fain go without it, but cannot, because its phenomena present relatively to each other an order so strict and so indifferent as to the point of origin chosen, that this regularity and this indifference really constitute an independent existence. So he must resign himself to retaining at least the phantasm of matter. But then he manages to deprive it of all the qualities which give it life. In an amorphous space he carves out moving figures; or else (and it comes to nearly the same thing), he imagines relations of magnitude which adjust themselves one to another, mathematical functions which go on evolving and developing their own content: representation, laden with the spoils of matter, thenceforth displays itself freely in an un extended consciousness. But it is not enough to cut out, it is necessary to sew the pieces together. You must now explain how those qualities which you have detached from their material support can be joined to it again. Each attribute which you take away from matter widens the interval between representation and its object. If you make matter unextended, how will it acquire extension? If you reduce it to homogeneous movements, whence arises quality? Above all, how are we to imagine a relation between a thing and its image, between matter and thought, since each of these terms possesses, by definition, only that which is lacking to the other? Thus difficulties spring up beneath our feet; and every effort that you make to dispose of one of them does but resolve it into many more. What then do we ask of you? Merely to give up your magician's wand, and to continue along the path on which you first set out. You showed us external images reaching the organs of sense, modifying the nerves, propagating their influence in the brain. Well, follow the process to the end. The movement will pass through the cerebral substance (although not without having tarried there), and will then expand into voluntary action. There you have the whole mechanism of perception. As for perception itself, in so far as it is an image, you are not called upon to retrace its genesis, since you posited it to begin with, and since, moreover, no other course was open to you. In assuming the brain, in assuming the smallest portion of matter, did you not assume the totality of images? What you have to explain, then, is not how perception arises, but how it is limited, since it should be the image of the whole, and is in fact reduced to the image of that which interests you. But if it differs from the mere image, precisely in that its parts range themselves with reference to a variable center, its limitation is easy to understand: unlimited de jure, it confines itself de facto to indicating the degree of indetermination allowed to the acts of the special image which you call your body. And, inversely, it follows that the indetermination of the movements of your body, such as it results from the structure of the grey matter of the brain, gives the exact measure of the extent of your perception. It is no wonder, then, that everything happens as though your perception were a result of the internal motions of the brain and issued in some sort from the cortical centers. It could not actually come from them, since the brain is an image like others, enveloped in the mass of other images, and it would be absurd that the container should issue from the content. But since the structure of the brain is like the detailed plan of the movements among which you have the choice, and since that part of the external images which appears to return upon itself in order to constitute perception includes precisely all the points of the universe which these movements could affect, conscious perception and cerebral movement are in strict correspondence. The reciprocal dependence of these two terms is therefore simply due to the fact that both are functions of a third, which is the indetermination of the will.

Take, for example, a luminous point P, of which the rays impinge on the different parts a, b, c, of the retina. At this point P, science localizes vibrations of a certain amplitude and duration. At the same point P, consciousness perceives light. We propose to show, in the course of this study, that both are right; and that there is no essential difference between the light and the movements, provided we restore to movement the unity, indivisibility, and qualitative heterogeneity denied to it by abstract mechanics; provided also that we see in sensible qualities contractions effected by our memory. Science and consciousness would then coincide in the instantaneous. For the moment all we need say, without examining too closely the meaning of the words, is that the point P sends to the retina vibrations of light. What happens then? If the visual image of the point P were not already given, we should indeed have to seek the manner in which it had been engendered, and should soon be confronted by an insoluble problem. But, whatever we do, we cannot avoid assuming it to begin with: the sole question is, then, to know how and why this image is chosen to form part of my perception, while an infinite number of other images remain excluded from it. Now I see that the vibrations transmitted from the point P to the various parts of the retina are conducted to the subcortical and cortical optic centers, often to other centers as well, and that these centers sometimes transmit them to motor mechanisms, sometimes provisionally arrest them. The nervous elements concerned are, therefore, what give efficacy to the disturbance received; they symbolize the indetermination of the will; on their soundness this indetermination depends; consequently, any injury to these elements, by diminishing our possible action, diminishes perception in the same degree. In other words, if there exist in the material world places where the vibrations received are not mechanically transmitted, if there are, as we said, zones of indetermination, these zones must occur along the path of what is termed the sensori-motor process; and hence all must happen as though the rays Pa, Pb, Pc were perceived along this path and afterwards projected into P. Further, while the indetermination is something which escapes experiment and calculation, this is not the case with the nervous elements by which the impression is received and transmitted. These elements are the special concern of the physiologist and the psychologist; on them all the details of external perception would seem to depend and by them they may be explained.

So we may say, if we like, that the disturbance, after having travelled along these nervous elements, after having gained the center, there changes into a conscious image which is subsequently exteriorized at the point P. But, when we so express ourselves, we merely bow to the exigencies of the scientific method; we in no way describe the real process. There is not, in fact, an unextended image which forms itself in consciousness and then projects itself into P. The truth is that the point P, the rays which it emits, the retina and the nervous elements affected, form a single whole; that the luminous point P is a part of this whole; and that it is really in P, and not elsewhere, that the image of P is formed and perceived.

When we represent things to ourselves in this manner, we do but return to the simple convictions of common sense. We all of us began by believing that we grasped the very object, that we perceived it in itself and not in us. When philosophers disdain an idea so simple and so close to reality, it is because the intracerebral process - that diminutive part of perception - appears to them the equivalent of the whole of perception. If we suppress the object perceived and keep the internal process, it seems to them that the image of the object remains. And their belief is easily explained: there are many conditions, such as hallucination and dreams, in which images arise that resemble external perception in all their details. Because as, in such cases, the object has disappeared while the brain persists, he holds that the cerebral phenomenon is sufficient for the production of the image. But it must not be forgotten that in all psychical states of this kind memory plays the chief part. We shall try to show later that, when perception, as we understand it, is once admitted, memory must arise, and that this memory has not, any more than perception itself, a cerebral state as its true and complete condition. But, without as yet entering upon the examination of these two points, we will content ourselves with a very simple observation which has indeed no novelty. In many people who are blind from birth, the visual centers are intact; yet they live and die without having formed a single visual image. Such an image, therefore, cannot appear unless the external object has, at least, once played its part: it must, once at any rate, have been part and parcel with representation. Now this is what we claim and for the moment all that we require, for we are dealing here with pure perception, and not with perception complicated by memory. Reject then the share of memory, consider perception in its unmixed state, and you will be forced to recognize that there is no image without an object. But, from the moment that you thus posit the intracerebral processes in addition to the external object which causes them, we can clearly see how the image of that object is given with it and in it: how the image should arise from the cerebral movement we shall never understand.

When a lesion of the nerves or of the centers interrupts the passage of the nerve vibration, perception is to that extent diminished. Need we be surprised? The office of the nervous system is to utilize that vibration, to convert it into practical deeds, really or virtually accomplished. If, for one reason or another, the disturbance cannot pass along, it would be strange if the corresponding perception still took place, since this perception would then connect our body with points of space which no longer directly invite it to make a choice. Sever the optic nerve of an animal: the vibrations issuing from the luminous point can no longer be transmitted to the brain and thence to the motor nerves; the thread, of which the optic nerve is a part and which binds the external object to the motor mechanisms of the animal, is broken: visual perception has therefore become impotent, and this very impotence is unconsciousness. That matter should be perceived without the help of a nervous system and without organs of sense, is not theoretically inconceivable; but it is practically impossible because such perception would be of no use. It would suit a phantom, not a living, and, therefore, acting, being. We are too much inclined to regard the living body as a world within a world, the nervous system as a separate being, of which the function is, first, to elaborate perceptions, and, then, to create movements. The truth is that my nervous system, interposed between the objects which affect my body and those which I can influence, is a mere conductor, transmitting, sending back or inhibiting movement. This conductor is composed of an enormous number of threads which stretch from the periphery to the center, and from the center to the periphery. As many threads as pass from the periphery to the center, so many points of space are there able to make an appeal to my will and to put, so to speak, an elementary question to my motor activity. Every such question is what is termed a perception. Thus perception is diminished by one of its elements each time one of the threads termed sensory is cut because some part of the external object then becomes unable to appeal to activity; and it is also diminished whenever a stable habit has been formed, because this time the ready-made response renders the question unnecessary. What disappears in either case is the apparent reflection of the stimulus upon itself, the return of the light on the image whence it comes; or rather that dissociation, that discernment, whereby the perception is disengaged from the image. We may therefore say that while the detail of perception is molded exactly upon that of the nerves termed sensory, perception as a whole has its true and final explanation in the tendency of the body to movement.

The cause of the general illusion on this point lies in the apparent indifference of our movements to the stimulation which excites them. It seems that the movement of my body in order to reach and to modify an object is the same, whether I have been told of its existence by the ear or whether it has been revealed to me by sight or touch. My motor activity thus appears as a separate entity, a sort of reservoir whence movements issue at will, always the same for the same action, whatever the kind of image which has called it into being. But the truth is that the character of movements which are externally identical is internally different, according as they respond to a visual, an auditory or a tactile impression. Suppose I perceive a multitude of objects in space; each of them, inasmuch as it is a visual form, solicits my activity. Now I suddenly lose my sight. No doubt I still have at my disposal the same quantity and the same quality of movements in space; but these movements can no longer be coordinated to visual impressions; they must in future follow tactile impressions, for example, and a new arrangement will take place in the brain. The protoplasmic expansions of the motor nervous elements in the cortex will now be in relation with a much smaller number of the nervous elements termed sensory. My activity is then really diminished, in the sense that although I can produce the same movements, the occasion comes more rarely from the external objects. Consequently, the sudden interruption of optical continuity has brought with it, as its essential and profound effect, the suppression of a large part of the queries or demands addressed to my activity. Now such as query or demand is, as we have seen, a perception. Here we put our finger on the mistake of those who maintain that perception springs from what is properly called the sensory vibration, and not from a sort of question addressed to motor activity. They sever this motor activity from the perceptive process; and, as it appears to survive the loss of perception, they conclude that perception is localized in the nervous elements termed sensory. But the truth is that perception is no more in the sensory centers than in the motor centers; it measures the complexity of their relations, and is, in fact, where it appears to be.

Psychologists who have studied infancy are well aware that our representation is at first impersonal . Only little by little, and as a result of experience, does it adopt our body as a center and become our representation. The mechanism of this process is, moreover, easy to understand. As my body moves in space, all the other images vary, while that image, my body, remains invariable. I must, therefore, make it a center, to which I refer all the other images. My belief in an external world does not come, cannot come, from the fact that I project outside myself sensations that are unextended: how could these sensations ever acquire extension, and whence should I get the notion of exteriority? But, if we allow that, as experience testifies, the aggregate of images is given to begin with, I can see clearly how my body comes to occupy, within this aggregate, a privileged position. And I understand also whence arises the notion of interiority and exteriority, which is, to begin with, merely the distinction between my body and other bodies. For, if you start from my body, as is usually done, you will never make me understand how impressions received on the surface of my body, impressions which concern that body alone, are able to become for me independent objects and form an external world. But if, on the contrary, all images are posited at the outset, my body will necessarily end by standing out in the midst of them as a distinct thing, since they change unceasingly, and it does not vary. The distinction between the inside and the outside will then be only a distinction between the part and the whole. There is, first of all, the aggregate of images; and, then, in this aggregate, there are "centers of action," from which the interesting images appear to be reflected: thus perceptions are born and actions made ready. My body is that which stands out as the center of these perceptions; my personality is the being to which these actions must be referred. The whole subject becomes clear if we travel thus from the periphery to the center, as the child does, and as we ourselves are invited to do by immediate experience and by common sense. On the contrary everything becomes obscure, and problems are multiplied on all sides, if we attempt, with the theorists, to travel from the center to the periphery. Whence arises, then, this idea of an external world constructed artificially, piece by piece, out of unextended sensations, though we can neither understand how they come to form an extended surface, nor how they are subsequently projected outside our body? Why insist, in spite of appearances, that I should go from my conscious self to my body, then from my body to other bodies, whereas in fact I place myself at once in the material world in general, and then gradually cut out within it the center of action which I shall come to call my body and to distinguish from all others? There are so many illusions gathered round this belief in the originally unextended character of our external perception; there are, in the idea that we project outside ourselves states which are purely internal, so many misconceptions, so many lame answers to badly stated questions, that we cannot hope to throw light on the whole subject at once. We believe that light will increase, as we show more clearly, behind these illusions, the metaphysical error which confounds "pure perception" with memory. But these illusions are, nevertheless, connected with real facts, which we may here indicate in order to correct their interpretation.

The first of these facts is that our senses require education. Neither sight nor touch is able at the outset to localize impressions. A series of comparisons and inductions is necessary, whereby we gradually coordinate one impression with another. Hence philosophers may jump to the belief that sensations are in their essence inextensive and that they constitute extensity by their juxtaposition. But is it not clear that, upon the hypothesis just advanced, our senses are equally in need of education - not, of course, in order to accommodate themselves to each other? Here, in the midst of all the images, there is a certain image which I term my body and of which the virtual action reveals itself by an apparent reflection of the surrounding images upon themselves. Suppose there are so many kinds of possible action for my body: there must be an equal number of systems of reflection for other bodies; each of these systems will be just what is perceived by one of my senses. My body, then, acts like an image which reflects others, and which, in so doing, analyzes them along lines corresponding to the different actions which it can exercise upon them. And, consequently, each of the qualities perceived in the same object by my different senses symbolizes a particular direction of my activity, a particular need. Now, will all these perceptions of a body by my different senses give me, when united, the complete image of that body? Certainly not, because they have been gathered from a larger whole. To perceive all the influences from all the points of all bodies would be to descend to the condition of a material object. Conscious perception signifies choice, and consciousness mainly consists in this practical discernment. The diverse perceptions of the same object, given by my different senses, will not, then, when put together, reconstruct the complete image of the object; they will remain separated from each other by intervals which measure, so to speak, the gaps in my needs. It is to fill these intervals that an education of the senses is necessary. The aim of this education is to harmonize my senses with each other, to restore between their data a continuity which has been broken by the discontinuity of the needs of my body, in short, to reconstruct, as nearly as may be, the whole of the material object. This, on our hypothesis, explains the need for an education of the senses. Now let us compare it with the preceding explanation. In the first, un extended sensations of sight combine with unextended sensations of touch and of the other senses to give, by their synthesis, the idea of a material object. But, to begin with, it is not easy to see how these sensations can acquire extension, nor how, above all, when extension in general has been acquired, we can explain in particular the preference of a given one of these sensations for a given point of space. And then we may ask: by what happy agreement, in virtue of what preestablished harmony, do these sensations of different kinds coordinate themselves to form a stable object, henceforth solidified, common to my experience and to that of all men, subject, in its relation to other objects, to those inflexible rules which we call the laws of nature? In the second, "the data of our different senses" are, on the contrary, the very qualities of things, perceived first in the things rather than in us: is it surprising that they come together, since abstraction alone has separated them? On the first hypothesis, the material object is nothing of all that we perceive: you put, on one side, the conscious principle with the sensible qualities and, on the other, a matter of which you can predicate nothing, which you define by negations because you have begun by despoiling it of all that reveals it to us. On the second hypothesis, an ever-deepening knowledge of matter becomes possible. Far from depriving matter of anything perceived, we must on the contrary, bring together all sensible qualities, restore their relationship, and reestablish among them the continuity broken by our needs. Our perception of matter is, then, no longer either relative or subjective, at least in principle, and apart, as we shall see presently, from affection and especially from memory; it is merely dissevered by the multiplicity of our needs. On the first hypothesis, spirit is as unknowable as matter, for (we) attribute to it the undefinable power of evoking sensations we know not whence, and of projecting them, we know not why, into a space where they will form bodies. On the second, the part played by consciousness is clearly defined: consciousness means virtual action, and the forms acquired by mind, those which hide the essence of spirit from us, should, with the help of this second principle, be removed as so many concealing veils. Thus, on our hypothesis, we begin to see the possibility of a clearer distinction between spirit and matter, and of a reconciliation between them. But we will leave this first point and come to the second.

The second fact brought forward consists of what was long termed the "specific energy of the nerves." We know that stimulation of the optic nerve by an external shock or by an electric current will produce a visual sensation and that this same electric current applied to the acoustic or to the glosso-pharyngeal nerve will cause a sound to be heard or a taste to be perceived. From these very particular facts have been deduced two very general laws: that different causes acting on the same nerve excite the same sensation and that the same cause, acting on different nerves, provokes different sensations. And from these laws it has been inferred that our sensations are merely signals and that the office of each sense is to translate into its own language homogeneous and mechanical movements occurring in space. Hence, as a conclusion, the idea of cutting our perception into two distinct parts, thenceforth incapable of uniting: on the one hand, homogeneous movements in space and, on the other hand, unextended sensations in consciousness. Now it is not our part to enter into an examination of the physiological problems raised by the interpretation of the two laws: in whatever way these laws are understood, whether the specific energy is attributed to the nerves or whether it is referred to the centers, insurmountable difficulties arise. But the very existence of the laws themselves appears more and more problematical. Lotze himself already suspected a fallacy in them. He awaited, before putting faith in them, "sound waves which should give to the eye the sensation of light, or luminous vibrations which should give to the ear a sound." The truth is that all the facts alleged can be brought back to a single type: the one stimulus capable of producing different sensations, the multiple stimuli capable of inducing the same sensation, are either an electric current or a mechanical cause capable of determining in the organ a modification of electrical equilibrium. Now we may well ask whether the electrical stimulus does not include different components, answering objectively to sensations of different kinds, and whether the office of each sense is not merely to extract from the whole the component that concerns it. We should then have, indeed, the same stimuli giving the same sensations and different stimuli provoking different sensations. To speak more precisely, it is difficult to admit, for instance, that applying an electrical stimulus to the tongue would not occasion chemical changes, and these changes are what, in all cases, we term tastes. Yet, while the physicist has been able to identify light with an electromagnetic disturbance, we may say, inversely, that what he calls here an electromagnetic disturbance is light, so that it is really light that the optic nerve perceives objectively when subject to electrical stimulus. The doctrine of specific energy appears to be nowhere more firmly based than in the case of the ear: nowhere also has the real existence of the thing perceived become more probable. We will not insist on these facts because they will be found stated and exhaustively discussed in a recent work. We will only remark that the sensations here spoken of are not images perceived by us outside our body, but rather affections localized within the body. Now it results from the nature and use of our body, as we shall see, that each of its so-called sensory elements has its own real action, which must be of the same kind as its virtual action on the external objects which it usually perceives; and thus we can understand how it is that each of the sensory nerves appears to vibrate according to a fixed manner of sensation. But to elucidate this point we must consider the nature of affection. Thus we are led to the third and last argument which we have to examine.

This third argument is drawn from the fact that we pass by insensible degrees from the representative state, which occupies space, to the affective state which appears to be unextended.

Hence it is inferred that all sensation is naturally and necessarily unextended, so that extensity is superimposed upon sensation, and the process of perception consists in an exteriorization of internal states. The psychologist starts, in fact, from his body, and, as the impressions received at the periphery of this body seem to him sufficient for the reconstitution of the entire material universe, to his body he at first reduces the universe. But this first position is not tenable; his body has not, and cannot have, any more or any less reality than all other bodies. So he must go farther, follow to the end the consequences of his principle, and, after having narrowed the universe to the surface of the living body, contract this body itself into a center which he will end by supposing unextended. Then, from this center will start unextended sensations, which will swell, so to speak, will grow into extensity, and will end by giving extension first to his body and afterwards to all other material objects. But this strange supposition would be impossible if there were not, in point of fact, between images and ideas - the former extended and the latter unextended - a series of intermediate states, more or less vaguely localized, which are the affective states. Our understanding, yielding to its customary illusion, poses the dilemma that a thing either is or is not extended, and as the affective state participates vaguely in extension, is in fact imperfectly localized, we conclude that this state is absolutely unextended. But then the successive degrees of extension, and extensity itself, will have to be explained by I know not what acquired property of un extended states; the history of perception will become that of internal unextended states which acquire extension and project themselves without. Shall we put the argument in another form? There is hardly any perception which may not, by the increase of the action of its object upon our body, become an affection, and, more particularly, pain. Thus we pass insensibly from the contact with a pin to its prick. Inversely the decreasing pain coincides with the lessening perception of its cause, and exteriorizes itself, so to speak, into a representation. So it does seem, then, as if there were a difference of degree and not of nature between affection and perception. Now the first is intimately bound up with my personal existence: what, indeed, would be a pain detached from the subject that feels it? It seems, therefore, that it must be so with the second and that external perception is formed by projecting into space an affection which has become harmless. Realists and idealists are agreed in this method of reasoning. The latter see in the material universe nothing but a synthesis of subjective and unextended states; the former add that, behind this synthesis, there is an independent reality corresponding to it, but both conclude, from the gradual passage of affection to representation, that our representation of the material universe is relative and subjective and that it has, so to speak, emerged from us, rather than that we have emerged from it.

Before criticizing this questionable interpretation of an unquestionable fact, we may show that it does not succeed in explaining, or even in throwing light upon, the nature either of pain or of perception. That affective states, essentially bound up with my personality, and vanishing if I disappear, should acquire extensity by losing intensity, should adopt a definite position in space, and build up a firm, solid experience, always in accord with itself and with the experience of other men - is very difficult to realize. Whatever we do, we shall be forced to give back to sensations, in one form or another, first the extension and then the independence which we have tried to do without. But, what is more, affection, on this hypothesis, is hardly clearer than representation. For if it is not easy to see how affections, by diminishing in intensity, become representations, neither can we understand how the same phenomenon, which was given at first as perception, becomes affection by an increase of intensity. There is in pain something positive and active, which is ill explained by saying, as do some philosophers, that it consists in a confused representation. But still this is not the principal difficulty. That the gradual augmentation of the stimulus ends by transforming perception into pain, no one will deny; it is none the less true that this change arises at a definite moment: why at this moment rather than at another? And what special reason causes a phenomenon of which I was at first only an indifferent spectator to suddenly acquire for me a vital interest? Therefore, on this hypothesis I fail to see either why, at a given moment, a diminution of intensity in the phenomenon confers on it a right to extension and to an apparent independence, or why an increase of intensity should create, at one moment rather than at another, this new property, the source of positive action, which is called pain.

Let us return now to our hypothesis and show that affection must, at a given moment, arise out of the image. We shall thus understand how it is that we pass from a perception, which has extensity, to an affection which is believed to be unextended. But some preliminary remarks on the real significance of pain are indispensable.

When a foreign body touches one of the prolongations of the amoeba, that prolongation is retracted; every part of the protoplasmic mass is equally able to receive a stimulation and to react against it; perception and movement being here blended in a single property - contractility. But, as the organism grows more complex, there is a division of labor; functions become differentiated, and the anatomical elements thus determined forego their independence. In such an organism as our own, the nerve fibres termed sensory are exclusively empowered to transmit stimulation to a central region whence the vibration will be passed on to motor elements. It would seem then that they have abandoned individual action to take their share, as outposts, in the maneuvers of the whole body. But nonetheless they remain exposed, singly, to the same causes of destruction which threaten the organism as a whole, and while this organism is able to move - and thereby to escape a danger or to repair a loss - the sensitive element retains the relative immobility to which the division of labor condemns it. Thence arises pain, which, in our view, is nothing but the effort of the damaged element to set things right - a kind of motor tendency in a sensory nerve. Every pain, then, must consist in an effort - an effort which is doomed to be unavailing. Every pain is a local effort, and in its very isolation lies the cause of its impotence, because the organism, by reason of the solidarity of its parts, is able to move only as a whole. It is also because the effort is local that pain is entirely disproportioned to the danger incurred by the living being. The danger may be mortal and the pain slight; the pain may be unbearable (as in a toothache) and the danger insignificant. There is then, there must be, a precise moment when pain intervenes: it is when the interested part of the organism, instead of accepting the stimulation, repels it. And it is not merely a difference of degree that separates perception from affection but a difference in kind.

Now we have considered the living body as a kind of center whence is reflected on the surrounding objects the action which these objects exercise upon it: in that reflection external perception consists. But this center is not a mathematical point; it is a body, exposed, like all natural bodies, to the action of external causes which threaten to disintegrate it. We have just seen that it resists the influence of these causes. It does not merely reflect action received from without; it struggles, and thus absorbs some part of this action. Here is the source of affection. We might therefore say, metaphorically, that while perception measures the reflecting power of the body, affection measures its power to absorb.

But this is only a metaphor. We must consider the matter more carefully in order to understand clearly that the necessity of affection follows from the very existence of perception. Perception, understood as we understand it, measures our possible action upon things, and thereby, inversely, the possible action of things upon us. The greater the body’s power of action (symbolized by a higher degree of complexity in the nervous system), the wider is the field that perception embraces. The distance which separates our body from an object perceived really measures, therefore, the greater or less imminence of a danger, the nearer or more remote fulfillment of a promise. And, consequently, our perception of an object distinct from our body, separated from our body by an interval, never expresses anything but a virtual action. But the more distance decreases between this object and our body (the more, in other words, the danger becomes urgent or the promise immediate), the more does virtual action tend to pass into real action. Suppose the distance reduced to zero, that is to say that the object to be perceived coincides with our body, that is to say again, that our body is the object to be perceived. Then it is no longer virtual action, but real action, that this specialized perception will express, and this is exactly what affection is. Our sensations are, then, to our perceptions that which the real action of our body is to its possible, or virtual, action. Its virtual action concerns other objects and is manifested within those objects; its real action concerns itself, and is manifested within its own substance. Everything then will happen as if, by a true return of real and virtual actions to their points of application or of origin, the external images were reflected by our body into surrounding space and the real actions arrested by it within itself. And that is why its surface, the common limit of the external and the internal, is the only portion of space which is both perceived and felt.

That is to say once more, that my perception is outside my body and my affection within it. Just as external objects are perceived by me where they are, in themselves and not in me, so my affective states are experienced where they occur, that is, at a given point in my body. Consider the system of images which is called the material world. My body is one of them. Around this image is grouped the representation, i.e., its eventual influence on the others. Within it occurs affection, i.e., its actual effort upon itself. Such is indeed the fundamental difference which every one of us naturally makes between an image and a sensation. When we say that the image exists outside us, we signify by this that it is external to our body. When we speak of sensation as an internal state, we mean that it arises within our body. And this is why we affirm that the totality of perceived images subsists, even if our body disappears, whereas we know that we cannot annihilate our body without destroying our sensations.

Hence we begin to see that we must correct, at least in this particular, our theory of pure perception. We have argued as though our perception were a part of the images, detached, as such, from their entirety, as though, expressing the virtual action of the object upon our body, or of our body upon the object, perception merely isolated from the total object that aspect of it which interests us. But we have to take into account the fact that our body is not a mathematical point in space, that its virtual actions are complicated by, and impregnated with, real actions, or, in other words, that there is no perception without affection. Affection is, then, that part or aspect of the inside of our body which we mix with the image of external bodies; it is what we must first of all subtract from perception to get the image in its purity. But the psychologist who shuts his eyes to the difference of function and nature between perception and sensation - the latter involving a real action, and the former a merely possible action - can only find between them a difference of degree. Because sensation (on account of the confused effort which it involves) is only vaguely localized, he declares it unextended, and thence makes sensation in general the simple element from which we obtain by composition all external images. The truth is that affection is not the primary matter of which perception is made; it is rather the impurity with which perception is alloyed.

Here we grasp, at its origin, the error which leads the psychologist to consider sensation as unextended and perception as an aggregate of sensations. This error is reinforced, as we shall see, by illusions derived from a false conception of the role of space and of the nature of extensity. But it has also the support of misinterpreted facts, which we must now examine.

It appears, in the first place, as if the localization of an affective sensation in one part of the body were a matter of gradual training. A certain time elapses before the child can touch with the finger the precise point where it has been pricked. The fact is indisputable, but all that can be concluded from it is that some tentative essays are required to coordinate the painful impressions on the skin, which has received the prick, with the impressions of the muscular sense, which guides the movement, of arm and hand. Our internal affections, like our external perceptions, are of different kinds. These kinds of affections, like those of perception, are discontinuous, separated by intervals which are filled up in the course of education. But it does not at all follow that there is not, for each affection, an immediate localization of a certain kind, a local color which is proper to it. We may go further: if the affection has not this local color at once, it will never have it. For all that education can do is to associate with the actual affective sensation the idea of a certain potential perception of sight and touch, so that a definite affection may evoke the image of a visual or tactile impression, equally definite. There must be, therefore, in this affection itself, something which distinguishes it from other affections of the same kind and permits of its reference to this or that potential datum of sight or touch rather than to any other. But is not this equivalent to saying that affection possesses, from the outset, a certain determination of extensity?

Again, it is alleged that there are erroneous localizations, for example, the illusion of those who have lost a limb (an illusion which requires, however, further examination). But what can we conclude from this beyond the fact that education, once acquired, persists and that such data of memory as are more useful in practical life supplant those of immediate consciousness? It is indispensable, in view of action, that we should translate our affective experience into eventual data of sight, touch and muscular sense. When this translation is made, the original pales, but it never could have been made if the original had not been there to begin with, and if sensation had not been, from the beginning, localized by its own power and in its own way.

But the psychologist has much difficulty in accepting this idea from common sense. Just as perception, in his view, could be in the things perceived only if they had perception, so a sensation cannot be in the nerve unless the nerve feels. Now it is evident that the nerve does not feel. So he takes sensation away from the point where common sense localizes it, carries it toward the brain, on which, more than on the nerve, it appears to depend, and logically should end by placing it in the brain. But it soon becomes clear that if it is not at the point where it appears to arise, neither can it be anywhere else: if it is not in the nerve, neither is it in the brain; for to explain its projection from the center to the periphery a certain force is necessary, which must be attributed to a consciousness that is to some extent active. Therefore, he must go further, and, after having made sensations converge toward the cerebral center, must push them out of the brain and thereby out of space. So he has to imagine, on the one hand, sensations that are absolutely unextended, and, on the other hand, an empty space indifferent to the sensations which are projected into it: henceforth he will exhaust himself in efforts of every kind to make us understand how unextended sensations acquire extensity and why they choose for their abode this or that point of space rather than any other. But this doctrine is not only incapable of showing us clearly how the unextended takes on extension; it renders affection, extension and representation equally inexplicable. It must assume affective states as so many absolutes, of which it is impossible to say why they appear in or disappear from consciousness at definite moments. The passage from affection to representation remains wrapped in an equally impenetrable mystery because, once again, you will never find in internal states, which are supposed to be simple and unextended, any reason why they should prefer this or that particular order in space. And, finally, representation itself must be posited as an absolute: we cannot guess either its origin or its goal.

Everything becomes clearer, on the other hand, if we start from representation itself, that is to say, from the totality of perceived images. My perception, in its pure state, isolated from memory, does not go on from my body to other bodies; it is, to begin with, in the aggregate of bodies, then gradually limits itself and adopts my body as a center. And it is led to do so precisely by experience of the double faculty, which this body possesses, of performing actions and feeling affections; in a word, it is led to do so by experience of the sensori-motor power of a certain image, privileged among other images. For, on the one hand, this image always occupies the center of representation, so that the other images range themselves round it in the very order in which they might be subject to its action; on the other hand, I know it from within, by sensations which I term affective, instead of knowing only, as in the case of the other images, its outer skin. There is, then, in the aggregate of images, a privileged image, perceived in its depths and no longer only on the surface - the seat of affection and, at the same time, the source of action: it is this particular image which I adopt as the center of my universe and as the physical basis of my personality.

But before we go on to establish the precise relation between the personality and the images in which it dwells, let us briefly sum up, contrasting it with the analyses of current psychology, the theory of pure perception which we have just sketched out.

We will return, for the sake of simplicity, to the sense of sight, which we chose as our example. Psychology has accustomed us to assume the elementary sensations corresponding to the impressions received by the rods and cones of the retina. With these sensations it goes on to reconstitute visual perception. But, in the first place, there is not one retina, there are two; so that we have to explain how two sensations, held to be distinct, combine to form a single perception corresponding to what we call a point in space.

Suppose this problem is solved. The sensations in question are unextended; how will they acquire extension? Whether we see in extensity a framework ready to receive sensations, or an effect of the mere simultaneity of sensations coexisting in consciousness without coalescing, in either case something new is introduced with extensity, something unaccounted for: the process by which sensation arrives at extension, and the choice by each elementary sensation of a definite point in space, remain alike unexplained.

We will leave this difficulty, and suppose visual extension constituted. How does it in its turn reunite with tactile extension? All that my vision perceives in space is verified by my touch. Shall we say that objects are constituted by just the cooperation of sight and touch and that the agreement of the two senses in perception may be explained by the fact that the object perceived is their common product? But how could there be anything common, in the matter of quality, between an elementary visual sensation and a tactile sensation, since they belong to two different genera? The correspondence between visual and tactile extension can only be explained, therefore, by the parallelism of the order of the visual sensations with the order of the tactile sensations. So we are now obliged to suppose, over and above visual sensations, over and above tactile sensations, a certain order which is common to both and which, consequently, must be independent of either. We may go further: this order is independent of our individual perception, since it is the same for all men and constitutes a material world in which effects are linked with causes, in which phenomena obey laws. We are thus led at last to the hypothesis of an objective order, independent of ourselves, that is to say, of a material world distinct from sensation.

We have had, as we advanced, to multiply our irreducible data and to complicate more and more the simple hypothesis from which we started. But have we gained anything by it? Though the matter which we have been led to posit is indispensable in order to account for the marvelous accord of sensations among themselves, we still know nothing of it, since we must refuse to it all the qualities perceived, all the sensations of which it has only to explain the correspondence. It is not, then, it cannot be, anything of what we know, anything of what we imagine. It remains a mysterious entity.

But our own nature, the office and the function of our personality, remain enveloped in equal mystery. For these elementary unextended sensations which develop themselves in space, whence do they come, how are they born, what purpose do they serve? We must posit them as so many absolutes, of which we see neither the origin nor the end. And even supposing that we must distinguish, in each of us, between the spirit and the body, we can know nothing either of body or of spirit or of the relation between them.

Now in what does this hypothesis of ours consist, and at what precise point does it part company with the other? Instead of starting from affection, of which we can say nothing, since there is no reason why it should be what it is rather than anything else, we start from action, that is to say from our faculty of effecting changes in things, a faculty attested to by consciousness and toward which all the powers of the organized body are seen to converge. So we place ourselves at once in the midst of extended images, and in this material universe we perceive centers of indetermination, characteristic of life. In order that actions may radiate from these centers, the movements or influences of the other images must be, on the one hand, received and, on the other hand, utilized. Living matter, in its simplest form and in a homogeneous state, accomplishes this function simultaneously with those of nourishment and repair. The progress of such matter consists in sharing this double labor between two categories of organs, the purpose of the first, called organs of nutrition, being to maintain the second: the second, in their turn, are made for action; they have as their simple type a chain of nervous elements, connecting two extremities, of which the one receives external impressions and the other executes movements. Thus, to return to the example of visual perception, the office of the rods and cones is merely to receive excitations which will be subsequently elaborated into movements, either accomplished or nascent. No perception can result from this, and nowhere in the nervous system are there conscious centers, but perception arises from the same cause which has brought into being the chain of nervous elements, with the organs which sustain them and with life in general. It expresses and measures the power of action in the living being, the indetermination of the movement or of the action which will follow the receipt of the stimulus. This indetermination, as we have shown, will express itself in a reflection upon themselves or, better, in a division, of the images which surround our body, and, as the chain of nervous elements which receives, arrests and transmits movements is the seat of this indetermination and gives its measure, our perception will follow all the detail and will appear to express all the variations of the nervous elements themselves. Perception, in its pure state, is, then, in very truth, a part of things. And, as for affective sensation, it does not spring spontaneously from the depths of consciousness to extend itself, as it grows weaker, in space; it is one with the necessary modifications to which, in the midst of the surrounding images that influence it, the particular image that each one of us terms his body is subject.

Such is our simplified, schematic theory of external perception. It is the theory of pure perception. If we went no further, the part of consciousness in perception would thus be confined to threading on the continuous string of memory an uninterrupted series of instantaneous visions, which would be a part of things rather than of ourselves. That this is the chief office of consciousness in external perception is indeed what we may deduce a priori from the very definition of living bodies. For though the function of these bodies is to receive stimulations in order to elaborate them into unforeseen reactions, still the choice of the reaction cannot be the work of chance. This choice is likely to be inspired by past experience, and the reaction does not take place without an appeal to the memories which analogous situations may have left behind them. The indetermination of acts to be accomplished requires, then, if it is not to be confounded with pure caprice, the preservation of the images perceived. It may be said that we have no grasp of the future without an equal and corresponding outlook over the past, that the onrush of our activity makes a void behind it into which memories flow, and that memory is thus the reverberation, in the sphere of consciousness, of the indetermination of our will. But the action of memory goes further and deeper than this superficial glance would suggest. The moment has come to reinstate memory in perception, to correct in this way the element of exaggeration in our conclusions, and so to determine with more precision the point of contact between consciousness and things, between the body and the spirit.

We assert, at the outset, that if there be memory, that is, the survival of past images, these images must constantly mingle with our perception of the present and may even take its place. For if they have survived it is with a view to utility; at every moment they complete our present experience, enriching it with experience already acquired, and, as the latter is ever increasing, it must end by covering up and submerging the former. It is indisputable that the basis of real, and so to speak instantaneous, intuition, on which our perception of the external world is developed, is a small matter compared with all that memory adds to it. Just because the recollection of earlier analogous intuitions is more useful than the intuition itself, being bound up in memory with the whole series of subsequent events and capable thereby of throwing a better light on our decision, it supplants the real intuition of which the office is then merely - we shall prove it later - to call up the recollection, to give it a body, to render it active and thereby actual. We had every right, then, to say that the coincidence of perception with the object perceived exists in theory rather than in fact. We must take into account that perception ends by being merely an occasion for remembering, that we measure in practice the degree of reality by the degree of utility, and, finally, that it is our interest to regard as mere signs of the real those immediate intuitions which are, in fact, part and parcel of reality. But here we discover the mistake of those who say that to perceive is to project externally unextended sensations, which have been drawn from our own depths, and then to develop them in space. They have no difficulty in showing that our complete perception is filled with images which belong to us personally, with exteriorized (that is to say, recollected) images, but they forget that an impersonal basis remains in which perception coincides with the object perceived and which is, in fact, externality itself.

The capital error, the error which, passing over from psychology into metaphysic, shuts us out in the end from the knowledge both of body and spirit, is that which sees only a difference of intensity instead of a difference of nature, between pure perception and memory. Our perceptions are undoubtedly interlaced with memories, and, inversely, a memory, as we shall show later, only becomes actual by borrowing the body of some perception into which it slips. These two acts, perception and recollection, always interpenetrate each other, are always exchanging something of their substance as by a process of endosmosis. The proper office of psychologists would be to dissociate them, to give back to each its natural purity; in this way many difficulties raised by psychology, and perhaps also by metaphysics, might be lessened. But they will have it that these mixed states, compounded, in unequal proportions, of pure perception and pure memory, are simple. And so we are condemned to an ignorance both of pure memory and of pure perception; to knowing only a single kind of phenomenon which will be called now memory and now perception, according to the predominance in it of one or other of the two aspects; and, consequently, to finding between perception and memory only a difference in degree, and not in kind. The first effect of this error, as we shall see in detail, is to vitiate profoundly the theory of memory; for, if we make recollection merely a weakened perception, we misunderstand the essential difference between the past and the present, we abandon all hope of understanding the phenomena of recognition, and, more generally, the mechanism of the unconscious. But, inversely, if recollection is regarded as a weakened perception, perception must be regarded as a stronger recollection. We are driven to argue as though it was given to us after the manner of a memory, as an internal state, a mere modification of our personality; and our eyes are closed to the primordial and fundamental act of perception - the act, constituting pure perception, whereby we place ourselves in the very heart of things. And thus the same error, which manifests itself in psychology by a radical incapacity to explain the mechanism of memory, will in metaphysics profoundly influence the idealistic and realistic conceptions of matter.

For realism, in fact, the invariable order of the phenomena of nature lies in a cause distinct from our perceptions, whether this cause must remain unknowable, or whether we can reach it by an effort (always more or less arbitrary) of metaphysical construction. For the idealist, on the contrary, these perceptions are the whole of reality, and the invariable order of the phenomena of nature is but the symbol whereby we express, alongside of real perceptions, perceptions that are possible. But, for realism as for idealism, perceptions are "veridical hallucinations," states of the subject, projected outside himself, and the two doctrines differ merely in this: that, in the one, these states constitute reality; in the other, they are sent forth to unite with it.

But behind this illusion lurks yet another that extends to the theory of knowledge in general . We have said that the material world is made up of objects, or, if you prefer it, of images, of which all the parts act and react upon each other by movements. And that which constitutes our pure perception, is our dawning action, in so far as it is prefigured in those images. The actuality of our perception thus lies in its activity, in the movements which prolong it, and not in its greater intensity: the past is only idea, the present is ideo-motor. But this is what our opponents are determined not to see because they regard perception as a kind of contemplation, attribute to it always a purely speculative end, and maintain that it seeks some strange disinterested knowledge, as though, by isolating it from action, and thus severing its links with the real, they were not rendering it both inexplicable and useless. But thenceforward all difference between perception and recollection is abolished, since the past is essentially that which acts no longer, and since, by misunderstanding this characteristic of the past, they become incapable of making a real distinction between it and the present, i.e., that which is acting. No difference but that of mere degree will remain between perception and memory and neither in the one nor in the other will the subject be acknowledged to pass beyond himself. Restore, on the contrary, the true character of perception; recognize in pure perception a system of nascent acts which plunges roots deep into the real; and at once perception is seen to be radically distinct from recollection; the reality of things is no more constructed or reconstructed, but touched, penetrated, lived, and the problem at issue between realism and idealism, instead of giving rise to interminable metaphysical discussions, is solved, or rather, dissolved, by intuition.

In this way also we shall plainly see what position we ought to take up between idealism and realism, which are both condemned to see in a matter only a construction or a reconstruction executed by the mind. For if we follow to the end the principle according to which the subjectivity of our perception consists, above all, in the share taken by memory, we shall say that even the sensible qualities of matter would be known in themselves, from within and not from without, could we but disengage them from that particular rhythm of duration which characterizes our consciousness. Pure perception, in fact, however rapid we suppose it to be, occupies a certain depth of duration, so that our successive perceptions are never the real moments of things, as we have hitherto supposed, but are moments of our consciousness. Theoretically, we said, the part played by consciousness in external perception would be to join together, by the continuous thread of memory, instantaneous visions of the real. But, in fact, there is for us nothing that is instantaneous. In all that goes by that name there is already some work of our memory, and consequently, of our consciousness, which prolongs into each other, so as to grasp them in one relatively simple intuition, an endless number of moments of an endlessly divisible time. Now what is, in truth, the difference between matter as the strictest realism might conceive it and the perception which we have of it? Our perception presents us with a series of pictorial, but discontinuous, views of the universe; from our present perceptions we could not deduce subsequent perceptions because there is nothing in an aggregate of sensible qualities which foretells the new qualities into which they will change. On the contrary, matter, as realism usually posits it, evolves in such a manner that we can pass from one moment to the next by a mathematical deduction. It is true that, between this matter and this perception, scientific realism can find no point of contact because it develops matter into homogeneous changes in space, while it contracts perception into unextended sensations within consciousness. But, if our hypothesis is correct, we can easily see how perception and matter are distinguished and how they coincide. The qualitative heterogeneity of our successive perceptions of the universe results from the fact that each, in itself, extends over a certain depth of duration and that memory condenses in each an enormous multiplicity of vibrations which appear to us all at once, although they are successive. If we were only to divide, ideally, this undivided depth of time, to distinguish in it the necessary multiplicity of moments, in a word, to eliminate all memory, we should pass thereby from perception to matter, from the subject to the object. Then matter, becoming more and more homogeneous as our extended sensations spread themselves over a greater number of moments, would tend more and more toward that system of homogeneous vibrations of which realism tells us, although it would never coincide entirely with them. There would be no need to assume, on the one hand, space with unperceived movements, and, on the other, consciousness with unextended sensations. Subject and object would unite in an extended perception, the subjective side of perception being the contraction effected by memory, and the objective reality of matter fusing with the multitudinous and successive vibrations into which this perception can be internally broken up. Such at least is the conclusion which, we hope, will issue clearly from the last part of this essay. Questions relating to subject and object, to their distinction and their union, should be put in terms of time rather than of space.

But our distinction between "pure perception" and "pure memory" has yet another aim. Just as pure perception, by giving us hints as to the nature of matter, allows us to take an intermediate position between realism and idealism, so pure memory, on the other hand, by opening to us a view of what is called spirit should enable us to decide between those other two doctrines, materialism and spiritualism. Indeed, it is this aspect of the subject which will first occupy our attention in the two following chapters because it is in this aspect that our hypothesis allows some degree of experimental verification.

For it is possible to sum up our conclusions as to pure perception by saying that there is in matter something more than, but not something different from, that which is actually given. Undoubtedly, conscious perception does not compass the whole of matter, since it consists, in as far as it is conscious, in the separation, or the "discernment," of that which, in matter, interests our various needs. But between this perception of matter and matter itself there is but a difference of degree and not of kind, pure perception standing toward matter in the relation of the part to the whole. This amounts to saying that matter cannot exercise powers of any kind other than those which we perceive. It has no mysterious virtue; it can conceal none. To take a definite example, one, moreover, which interests us most nearly, we may say that the nervous system, a material mass presenting certain qualities of color, resistance, cohesion, etc., may well possess unperceived physical properties, but physical properties only. And hence it can have no other office than to receive, inhibit or transmit movement.

Now the essence of every form of materialism is to maintain the contrary, since it holds that consciousness, with all its functions, is born of the mere interplay of material elements. Hence it is led to consider even the perceived qualities of matter - sensible, and consequently felt, qualities -as so many phosphorescences which follow the track of the cerebral phenomena in the act of perception. Matter, thus supposed capable of creating elementary facts of consciousness, might therefore just as well engender intellectual facts of the highest order. It is, then, the essence of materialism to assert the perfect relativity of sensible qualities, and it is not without good reason that this thesis, which Democritus has formulated in precise terms, is as old as materialism.

But spiritualism has always followed materialism along this path. As if everything lost to matter must be gained by spirit, spiritualism has never hesitated to despoil matter of the qualities with which it is invested in our perception, and which, on this view, are subjective appearances. Matter has thus too often been reduced to a mysterious entity which, just because all we know of it is an empty show, might as well engender thought as well as any other phenomenon.

The truth is that there is one, and only one, method of refuting materialism: it is to show that matter is precisely that which it appears to be. Thereby we eliminate all virtuality, all hidden power, from matter and establish the phenomena of spirit as an independent reality. But to do this we must leave to matter those qualities which materialists and spiritualists alike strip from it: the latter that they may make of them representations of the spirit, the former that they may regard them only as the accidental garb of space.

This, indeed, is the attitude of common sense with regard to matter, and for this reason common sense believes in spirit. It seems to us that philosophy should here adopt the attitude of common sense, although correcting it in one respect. Memory, inseparable in practice from perception, imports the past into the present, contracts into a single intuition many moments of duration, and thus by a twofold operation compels us, de facto, to perceive matter in ourselves, whereas we, de jure, perceive matter within matter.

Hence the capital importance of the problem of memory. If it is memory above all that lends to perception its subjective character, the philosophy of matter must aim, in the first instance, we said, at eliminating the contributions of memory. We must now add that, as pure perception gives us the whole or at least the essential part of matter (since the rest comes from memory and is superadded to matter), it follows that memory must be, in principle, a power absolutely independent of matter. If, then, spirit is a reality, it is here, in the phenomenon of memory, that we may come into touch with it experimentally. And hence any attempt to derive pure memory from an operation of the brain should reveal on analysis a radical illusion.

Let us put the same statement in clearer language. We maintain that matter has no occult or unknowable power and that it coincides, in essentials, with pure perception. Therefore we conclude that the living body in general, and the nervous system in particular, are only channels for the transmission of movements, which, received in the form of stimulation, are transmitted in the form of action, reflex or voluntary. That is to say, it is vain to attribute to the cerebral substance the property of engendering representations. Now the phenomena of memory, in which we believe that we can grasp spirit in its most tangible form, are precisely those of which a superficial psychology is most ready to find the origin in cerebral activity alone; just because they are at the point of contact between consciousness and matter, and because even the adversaries of materialism have no objection to treating the brain as a storehouse of memories. But if it could be positively established that the cerebral process answers only to a very small part of memory, that it is rather the effect than the cause, that matter is here as elsewhere the vehicle of an action and not the substratum of a knowledge, then the thesis which we are maintaining would be demonstrated by the very example which is commonly supposed to be most unfavorable to it, and the necessity might arise of erecting spirit into an independent reality. In this way also, perhaps some light would be thrown on the nature of what is called spirit and on the possibility of the interaction of spirit and matter. For a demonstration of this kind could not be purely negative. Having shown what memory is not, we should have to try to discover what it is. Having attributed to the body the sole function of preparing actions, we are bound to enquire why memory appears to be one with this body, how bodily lesions influence it, and in what sense it may be said to mold itself upon the state of the brain matter. It is, moreover, impossible that this enquiry should fail to give us some information as to the psychological mechanism of memory and the various mental operations connected therewith. And, inversely, if the problems of pure psychology seem to acquire some light from our hypothesis, this hypothesis itself will thereby gain in certainty and weight.

But we must present this same idea in yet a third form, so as to make it quite clear why the problem of memory is in our eyes a privileged problem. From our analysis of pure perception issue two conclusions, which are in some sort divergent, one of them going beyond psychology in the direction of psycho-physiology and the other in that of metaphysics, but neither allowing of immediate verification. The first concerns the office of the brain in perception: we maintain that the brain is an instrument of action, and not of representation. We cannot demand from facts the confirmation of this thesis because pure perception bears, by definition, upon present objects, acting on our organs and our nerve centers; and because everything always happens, in consequence, as though our perceptions emanated from our cerebral state and were subsequently projected upon an object which differs absolutely from them. In other words, with regard to external perception, the thesis which we dispute and that which we substitute for it lead to precisely the same consequence, so that it is possible to invoke in favor of either the one or the other its greater intelligibility, but not the authority of experience. On the contrary, the empirical study of memory may and must decide between them. For pure recollection is, by hypothesis, the representation of an absent object. If the necessary and sufficient cause of perception lies in a certain activity of the brain, this same cerebral activity, repeating itself more or less completely in the absence of the object, will suffice to reproduce perception: memory will be entirely explicable by the brain. But if we find that the cerebral mechanism does indeed in some sort condition memories, but is in no way sufficient to ensure their survival; if it concerns, in remembered perception, our action rather than our representation; we shall be able to infer that it plays an analogous part in perception itself and that its office is merely to ensure our effective action on the object present. Our first conclusion may thus find its verification. There would still remain this second conclusion, which is of a more metaphysical order - viz.: that in pure perception we are actually placed outside ourselves; we touch the reality of the object in an immediate intuition. Here also an experimental verification is impossible, since the practical results are absolutely the same whether the reality of the object is intuitively perceived or whether it is rationally constructed. But here again a study of memory may decide between the two hypotheses. For, in the second, there is only a difference of intensity, or more generally, of degree, between perception and recollection, since they are both self-sufficient phenomena of representation. But if, on the contrary, we find that the difference between perception and recollection is not merely in degree, but is a radical difference in kind, the presumption will be in favor of the hypothesis which finds in perception something which is entirely absent from memory, a reality intuitively grasped. Thus the problem of memory is in very truth a privileged problem, in that it must lead to the psychological verification of two theses which appear to be insusceptible to proof, and of which the second, being of a metaphysical order, appears to go far beyond the borders of psychology.

The road which we have to follow, then, lies clear before us. We shall first review evidence of various kinds borrowed from normal and from pathological psychology, by which philosophers might hold themselves justified in maintaining a physical explanation of memory. This examination must needs be minute or it would be useless. Keeping as close as possible to facts, we must seek to discover where, in the operations of memory, the office of the body begins and where it ends. And should we, in the course of this inquiry, find confirmation of our own hypothesis, we shall not hesitate to go further and, considering in itself the elementary work of the mind, complete the theory thereby sketched out, of the relation of spirit with matter.