The Mind and the Brain

The essential law of nature is relatively easy to formulate, as it is comprised in the very definition of law. It simply consists in the sentence: uniformity under similar conditions. We might also say: a constant relation between two or several phenomena, which can also be expressed in a more abstract way by declaring that the law of nature rests on the combination of two notions, identity and constancy.

On the other hand, the laws of our psychical activity partly correspond to the same tendencies, and it would be easy to demonstrate that the microcosm of our thoughts is governed by laws which are also an expression of these two combined notions of constancy and identity. It is, above all, in the working of the intellectual machine, the best known and the most clearly analysed up till now, that we see the application of this mental law which resembles, as we say, on certain sides, the physical law: and the best we can do for our demonstration will doubtless be to dissect our reasoning powers. Reason, a process essential to thought in action, is developed in accordance with a law which resembles in the most curious manner a physical law. It resembles it enough to imitate it, to conform to it, and, so to speak, to mould itself on it.

Now, the reason does not follow the caprices of thought, it is subject to rules; it results from the properties of the images, those properties which we have above referred to, the material character of which we have recognised, and which are two in number—similarity and contiguity, as they are termed in the jargon of the schools. They are properties which have for their aim to bring things together, to unite, and to synthetise. They are unceasingly at work, and so apparent in their labour that they have long been known. We know, since the time of Aristotle, that two facts perceived at the same time reproduce themselves together in the memory—this is the law of contiguity; and that two facts perceived separately, but which are similar, are brought together in our mind—this is the law of similarity.

Now, similarity and contiguity form by combination the essential part of all kinds of reasoning, and this reasoning, thus understood, works in a fashion which much resembles (we shall see exactly in what degree) a physical law. I wish to show this in a few words. What renders my demonstration difficult and perhaps obscure is, that we shall be obliged to bring together rather unexpectedly categories of phenomena which are generally considered separate.

The distinctive attribute of the reason consists, as I have said, in the setting to work of these two elementary properties, similarity and contiguity. It consists, in fact, in extending continuity by similarity; in endowing with identical properties and similar accompaniments things which resemble each other; in other words, it consists in impliedly asserting that the moment two things are identical in one point they are so for all the rest. This will be fairly well understood by imagining what takes place when mental images having the above-mentioned properties meet. Suppose that B is associated with C, and that A resembles B. In consequence of their resemblance the passing from A to B is easy; and then B suggesting C by contiguity, it happens that this C is connected with A connected, though, in reality, they have never been tried together. I say they are associated on the basis of their relation to B, which is the rallying point. It is thus that, on seeing a piece of red-hot iron (A), I conclude it is hot (C), because I recollect distinctly or unconsciously another piece of red-hot iron (B), of which I once experienced the heat. It is this recollection B which logicians, in their analysis of logical, verbal, and formal argument, call the middle term. Our representation of the process of reasoning is not special to argument. It also expresses the process of invention, and every kind of progress from the known to the unknown. It is an activity which creates relations, which assembles and binds together, and the connections made between different representations are due to their partial identities, which act as solder to two pieces of metal.

It will now be understood that these relations between the images curiously resemble the external order of things, the order of our sensations, the order of nature, the physical law. This is because this physical law also has the same character and expresses itself similarly. We might say "all things which resemble each other have the same properties," or "all things alike on one point resemble each other on all other points." But immediately we do so, the difference between the physical and the mental law becomes apparent. The formula we have given is only true on condition that many restrictions and distinctions are made.

The process of nature is so to do that the same phenomenon always unfolds itself in the same order. But this process is not always comprehended in real life, for it is hidden from our eyes by the manifold combinations of chance; in the reality that we perceive there is a crowd of phenomena which resemble each other but are not really the same. There are a number of phenomena which co-exist or follow each other without this order of co-existence or succession being necessary or constant. In other words, there are resemblances which are the marks of something, as a logician would say, and others which are not the marks of anything; there are relations of time and space which are the expression of a law; there are some which are accidental, and may possibly never be reproduced.

It would be a wonderful advantage if every scientific specialist would make out a list of the non-significant properties that he recognises in matter. The chemist, for example, would show us that specific weight has hardly any value in diagnosis, that the crystalline form of a salt is often not its own, that its colour especially is almost negligible because an immense number of crystals are white or colourless, that precipitation by a given substance does not ordinarily suffice to characterise a body, and so on. The botanist, on his part, would show us that, in determining plants, absolute dimension is less important than proportion, colour less important than form, certain structures of organs less important than others. The pathologist would teach us that most pathological symptoms have but a trivial value; the cries, the enervation, the agitation of a patient, even the delirium which so affects the bystanders, are less characteristic of fever than the rate of his pulse, and the latter less than the temperature of the armpit or the dryness of the tongue, &c. At every moment the study of science reveals resemblances of facts and contiguities of facts which must be neglected for the sake of others. And if we pass from this profound knowledge of the objects to the empirical knowledge, to the external perception of bodies, it is in immense number that one espies around one traps laid by nature. The sound we hear resembles several others, all produced by different causes; many of our visual sensations likewise lend themselves to the most varied interpretations; by the side of the efficient cause of an event we find a thousand entangled contingencies which appear so important that to disentangle them we are as much perplexed as the savage, who, unable to discriminate between causes and coincidences, returns to drink at the well which has cured him, carefully keeping to the same hour, the same gestures, and the same finery.

The reason of this is that the faculty of similarity and the faculty of contiguity do not give the distinction, necessary as it is, between resemblances and co-existences which are significant and those which are not. The causal nexus between two phenomena is not perceived as something apart and sui generis; it is not even perceived at all. We perceive only their relation in time and space, and it is our mind which raises a succession to the height of a causal connection, by intercalating between cause and effect something of what we ourselves feel when we voluntarily order the execution of a movement. This is not the place to inquire what are the experimental conditions in which we subject phenomena to this anthropomorphic transformation; it will suffice for us to repeat here that, in perception, a chance relation between phenomena impresses us in the same way as when it is the expression of a law.

Our intellectual machine sometimes works in accord with the external law and at others makes mistakes and goes the wrong way. Then we are obliged to correct it, and to try a better adjustment, either by profounder experimenting with nature (methods of concordance, discordance, variations, &c.), or by a comparison of different judgments and arguments made into a synthesis; and this collaboration of several concordant activities ends in a conclusion which can never represent the truth, but only the probable truth. The study of the laws of the mind shows us too clearly, in fact, their fluidity with regard to the laws of nature for us not to accept probabilism. There exists no certitude—only very varied degrees of probability. Daily practice contents itself with a very low degree of probability; judicial logic demands a rather higher one, especially when it is a question of depriving one of our fellow-creatures of liberty or life. Science claims one higher still. But there is never anything but differences of degrees in probability and conjecture.

This, then, is the definition of psychology that we propose. It studies a certain number of laws which we term mental, in opposition to those of external nature, from which they differ, but which, properly speaking, do not deserve the qualification of mental, since they are—or at least the best known of them are—laws of the images, and the images are material elements. Although it may seem absolutely paradoxical, psychology is a science of matter—the science of a part of matter which has the property of preadaptation.

BOOK III

THE UNION OF THE SOUL 40 AND THE BODY

CHAPTER I

THE MIND HAS AN INCOMPLETE LIFE

The problem of the union of the mind and the body is not one of those which present themselves in pure speculation; it has its roots in experimental facts, and is forced upon us by the necessity of explaining observations such as those we are about to quote.

The force of our consciousness, the correctness of our judgments, our tempers and our characters, the state of health of our minds, and also their troubles, their weaknesses, and even their existence, are all in a state of strict dependence on the condition of our bodies, more precisely with that of our nervous systems, or, more precisely still, with the state of those three pounds of proteid substance which each of us has at the back of his forehead, and which are called our brains. This is daily demonstrated by thousands upon thousands of observations.

The question is to know how this union of the body with the consciousness is to be explained, it being assumed that the two terms of this union present a great difference in their nature. The easier it seems to demonstrate that this union exists, the more difficult it appears to explain how it is realised; and the proof of this difficulty is the number of divergent interpretations given to it. Were it a simple question of fact, the perpetual discussions and controversies upon it would not arise.

Many problems here present themselves. The first is that of the genesis or origin of the consciousness. It has to be explained how a psychical phenomenon can appear in the midst of material ones. In general, one begins by supposing that the material phenomena are produced first; they consist, for instance, in the working of the nervous centres. All this is physical or chemical, and therefore material. Then at a given moment, after this mechanical process, a quite different phenomenon emerges. This is thought, consciousness, emotion. Then comes the question whether this production of thought in the midst of physical phenomena is capable of explanation, and how thought is connected with its physical antecedents. What is the nature of the link between them? Is it a relation of cause to effect, of genesis? or a coincidence? or the interaction of two distinct forces? Is this relation constant or necessary? Can the mind enjoy an existence independent of the brain? Can it survive the death of the brain?

The second question is that of knowing what is the rôle, the utility, and the efficacity of the psychical phenomenon. Once formed, this phenomenon evolves in a certain direction and assumes to us who have consciousness of it a very great importance. What is its action on the material phenomena of the brain which surround it? Does it develop according to laws of its own, which have no relation to the laws of brain action? Does it exercise any action on these intra-cerebral functions? Does it exercise any action on the centrifugal currents which go to the motor nerves? Is it capable of exciting a movement? or is it deprived of all power of creating effect?

We will briefly examine the principal solutions which the imagination of mankind has found for these very difficult problems. Some of the best known of these solutions bear the names of spiritualism, materialism, parallelism, and monism. We will speak of these and of some others also.

Before beginning our critical statement, let us recall some of the results of our previous analyses which here intrude themselves, to use the ambitious language of Kant, as the prolegomena to every future solution which claims the title of science. In fact, we are now no longer at the outset of our investigation. We have had to acknowledge the exactness of certain facts, and we are bound to admit their consequences. Notably, the definition of psychical phenomena at which we arrived, not without some trouble, will henceforth play a rather large part in our discussion. It will force us to question a great metaphysical principle which, up till now, has been almost universally considered as governing the problem of the union of the mind with the body.

This principle bears the name of the axiom of heterogeneity, or the principle of psycho-physical dualism. No philosopher has more clearly formulated it, and more logically deduced its consequences, than Flournoy. This author has written a little pamphlet called Métaphysique et Psychologie, wherein he briefly sets forth all the known systems of metaphysics by reducing them to the so-called principle of heterogeneity; after this, the same principle enables him to "execute" them. He formulates it in the following terms: "body and mind, consciousness and the molecular cerebral movement of the brain, the psychical fact and the physical fact, although simultaneous, are heterogeneous, unconnected, irreducible, and obstinately two."41 The same author adds: "this is evident of itself, and axiomatic. Every physical, chemical, or physiological event, in the last resort, simply consists, according to science, in a more or less rapid displacement of a certain number of material elements, in a change of their mutual distances or of their modes of grouping. Now, what can there be in common, I ask you, what analogy can you see, between this drawing together or moving apart of material masses in space, and the fact of having a feeling of joy, the recollection of an absent friend, the perception of a gas jet, a desire, or of an act of volition of any kind?" And further on: "All that we can say to connect two events so absolutely dissimilar is, that they take place at the same time.... This does not mean that we wish to reduce them to unity, or to join them together by the link of causality … it is impossible to conceive any real connection, any internal relation between these two unconnected things."

Let us not hesitate to denounce as false this proposition which is presented to us as an axiom. On looking closely into it, we shall perceive that the principle of heterogeneity does not contain the consequences it is sought to ascribe to it. It seems to me it should be split up into two propositions of very unequal value: 1, the mind and body are heterogeneous; 2, by virtue of this heterogeneity it is not possible to understand any direct relation between the two.

Now, if the first proposition is absolutely correct, in the sense that consciousness and matter are heterogeneous, the second proposition seems to us directly contrary to the facts, which show us that the phenomena of consciousness are incomplete phenomena. The consciousness is not sufficient for itself; as we have said, it cannot exist by itself. This again, if you like, is an axiom, or rather it is a fact shown by observation and confirmed by reflection. Mind and matter brought down to the essential, to the consciousness and its object, form a natural whole, and the difficulty does not consist in uniting but in separating them. Consider the following fact: "I experience a sensation, and I have consciousness of it." This is the coupling of two things—a sensation and a cognition.

The two elements, if we insist upon it, are heterogeneous, and they differ qualitatively; but notwithstanding the existing prejudice by reason of which no direct relation, no commerce, can be admitted between heterogeneous facts, the alliance of the consciousness and the sensation is the natural and primitive fact. They can only be separated by analysis, and a scrupulous mind might even ask whether one has the right to separate them. I have a sensation, and I have consciousness of it. If not two facts, they are one and the same. Now, sensation is matter and my consciousness is mind. If I am judging an assortment of stuffs, this assortment, or the sensation I have of them, is a particle of matter, a material state, and my judgment on this sensation is the psychical phenomenon. We can neither believe, nor desire, nor do any act of our intelligence without realising this welding together of mind and matter. They are as inseparable as motion and the object that moves; and this comparison, though far-fetched, is really very convenient. Motion cannot exist without a mobile object; and an object, on the other hand, can exist without movement. In the same way, sensation may exist without the consciousness; but the converse proposition, consciousness without sensation, without an object, an empty consciousness or a "pure thought," cannot be understood.

Let us mark clearly how this union is put forward by us. We describe it after nature. It is observation which reveals to us the union and the fusion of the two terms into one. Or, rather, we do not even perceive their union until the moment when, by a process of analysis, we succeed in convincing ourselves that that which we at first considered single is really double, or, if you like, can be made into two by the reason, without being so in reality. Thus it happens that we bring this big problem in metaphysics on to the field of observation.

Our solution vaguely resembles that which has sometimes been presented under the ancient name of physical influx, or under the more modern name of inter-actionism. There are many authors who maintain that the soul can act directly on the body and modify it, and this is what is called inter-actionism. Thereby is understood, if I mistake not, an action from cause to effect, produced between two terms which enjoy a certain independence with regard to each other. This interpretation is indubitably close to ours, though not to be confused with it. My personal interpretation sets aside the idea of all independence of the mind, since it attributes to the mind an incomplete and, as it were, a virtual existence.

If we had to seek paternity for ideas I would much rather turn to Aristotle. It was not without some surprise that I was able to convince myself that the above theory of the relations between the soul and the body is to be found almost in its entirety in the great philosopher. It is true that it is mixed up with many accessory ideas which are out of date and which we now reject; but the essential of the theory is there very clearly formulated, and that is the important point. A few details on this subject will not be out of place. I give them, not from the original source, which I am not erudite enough to consult direct, but from the learned treatise which Bain has published on the psychology of Aristotle, as an appendix to his work on the Senses and the Intelligence.

The whole metaphysics of Aristotle is dominated by the distinction between form and matter. This distinction is borrowed from the most familiar fact in the sensible world—the form of solid objects. We may name a substance without troubling ourselves as to the form it possesses, and we may name the form without regard to the substance that it clothes. But this distinction is a purely abstract one, for there can be no real separation of form from matter, no form without matter, and no matter without form. The two terms are correlative; each one implies the other, and neither can be realised or actualised without the other. Every individual substance can be considered from a triple point of view: 1st, form; 2nd, matter; and 3rd, the compound or aggregate of form and matter, the inseparable Ens, which transports us out of the domain of logic and abstraction into that of reality.

Aristotle recognises between these two logical correlatives a difference in rank. Form is superior, nobler, the higher in dignity, nearer to the perfect entity; matter is inferior, more modest, more distant from perfection. On account of its hierarchical inferiority, matter is often presented as the second, or correlatum, and form as the first, or relatum. This difference in rank is so strongly marked, that these two correlations are likewise conceived in a different form—that of the potential and the actual. Matter is the potential, imperfect, roughly outlined element which is not yet actual, and may perhaps never become so. Form is the actual, the energy, the entelechy which actualises the potential and determines the final compound.

These few definitions will make clear the singularly ingenious idea of Aristotle on the nature of the body, the soul, and of their union. The body is matter which is only intelligible as the correlatum of form; it can neither exist by itself nor be known by itself—that is to say, when considered outside this relation. The soul is form, the actual. By uniting with the body it constitutes the living subject. The soul is the relatum, and is unintelligible and void of sense without its correlatum. "The soul," says Aristotle, "is not a variety of body, but it could not exist without a body: the soul is not a body, but something which belongs or is relative to a body." The animated subject is a form plunged and engaged in matter, and all its actions and passions are so likewise. Each has its formal side which concerns the soul, and its material side which concerns the body. The emotion which belongs to the animated subject or aggregate of soul and body is a complex fact having two aspects logically distinguishable from each other, each of which is correlative to the other and implies it. It is thus not only with our passions, but also with our perceptions, our imaginations, reminiscences, reasonings, and efforts of attention to learn. Intelligence, like emotion, is a phenomenon not simply of the corporeal organism nor of the Νους only, but of the commonalty or association of which they are members, and when the intelligence weakens it is not because the Νους is altered, but because the association is destroyed by the ruin of the corporeal organism.

These few notes, which I have taken in their integrity from Bain's text, allow us thoroughly to comprehend the thought of Aristotle, and it seems to me that the Greek philosopher, by making of the soul and body two correlative terms, has formed a comparison of great exactness. I also much admire his idea according to which it is through the union of the body and soul that the whole, which till then was only possible, goes forth from the domain of logic and becomes actual. The soul actualises the body, and becomes, as he said, its entelechy.

These views are too close to those I have myself just set forth for it to be necessary to dwell on their resemblance. The latter would become still stronger if we separated from the thought of Aristotle a few developments which are not essential, though he allowed them great importance: I refer to the continual comparison he makes with the form and matter of corporeal objects. Happy though it may be, this comparison is but a metaphor which perhaps facilitates the understanding of Aristotle's idea, but is not essential to his theory. For my part, I attach far greater importance to the character of relatum, and correlatum ascribed to the two terms mind and matter, and to the actualisation42 produced by their union.