Why the Mind Seems to Be and yet Cannot Be Produced by the Brain
IF an electric current is applied to the closed eyelids we have a sensation of colour, if to the ears, a sensation of sound, if to the tongue, or nose, a sensation of taste or smell. What is apparently one and the same stimulus applied to different sense organs gives rise in the brain to different sensations. It seems easy to explain this by what we know of the anatomy and physiology of the brain. When our sense organs are stimulated, the stimulus is conveyed by means of sensory nerves to the brain and there gives rise to sensation, the sense organs are sensitive to various kinds of stimuli, the stimulus to the eyes gives the sensation of sight, to the ears the sensation of sound and so on. It seems then it must be the brain which gives the special character of our sensations to consciousness, for we have only to send the brain a stimulus through the optic nerve to get sight, through the auditory nerve to get sound and so on, and this notwithstanding that the stimulus has in itself none of the things which we distinguish as sensible qualities. Since it is out of sensations that all knowledge is built up, for there is nothing in the understanding which was not first in the senses, it seems to follow that our mind, that is the power or faculty we have of perceiving, remembering and imagining, must be produced by the brain, that is, be an effect of some process or other that goes on in the brain.
But it is not only by experiments such as this that we make the discovery that there is a close and intimate relation between the mind and the brain, a relation which makes the mind dependent on the brain. In ordinary discourse we use the words brain and mind as interchangeable terms, because it is quite evident that where there is lack of intelligence there is deficiency in the brain and where there is a high degree of intelligence there is a correspondingly high development of brain. The immense advance in recent times in our knowledge of the physiology of cerebral process serves more and more to emphasize the entire and absolute dependence of mind on brain, and particularly of the higher processes of mind on the development of the cells and fibres of the cerebral cortex. Physiologists tell us that there are the almost inconceivable number of something like 7000 million nerve cells in the brain of the newly born child and these, which neither increase nor decrease throughout life, undergo a development of interconnection by means of the branching fibres they send out in every direction. When through disease or malformation or any other cause this development is arrested we have mental deficiency or idiocy.
The brain is an organ of immense complexity and has a great deal more to do than only to turn stimuli into sensations. It is part of a complete nervous system and it is only a part of the brain that is concerned in mental process. A nervous system or something that closely corresponds to it seems to be a necessary acquirement of every living organism that moves freely, and its structure, however complex it may be in its higher development, is built up of a simple arrangement of cells and fibres that receive and transmit movement. Its function is to receive a stimulus and to transmit it to a centre where a responsive movement is prepared. The nervous system is therefore described as sensori-motor from the double function that it performs. There are two kinds of response to a stimulus—one immediate and automatic, the other conscious and willed. It is only those stimuli that are transmitted to the cerebral cortex, and only some of these, that give rise to consciousness; consciousness seems to occur just at the moment when the movement in the fibres reaches the cerebral cortex; some of these movements, not all, give rise to consciousness. If a movement gives rise to consciousness it occurs when a stimulus reaches the cortex and before it passes from the brain to the muscles to issue in actions. There appears to be a power of inhibiting or delaying the response to the stimulus while consciousness lasts and consciousness seems to have the function of giving us a choice of the direction which the response shall take.
Moreover, if we sever the connecting fibres between the sense organs and the brain, all sensation and all thought ceases. This seems to indicate that in some way or another the movements that pass to the nerve cells of the cerebral cortex are there transformed into sensations, thoughts and ideas, into what we group together and think of as a different and separate kind of thing and call the mind. And it seems impossible to doubt that it is the brain that produces the mind and not the mind that produces the brain, because the brain is an organ that develops continually throughout life and performs a multitude of other functions besides that of turning the excitation of its cells and fibres into sensations and perceptions, a function that seems to be intermittent and only called into activity at definite times and in special circumstances.
Many people think that our nature is a combination of two realities, a soul and a body, and that the mind belongs to the soul, which is immaterial or spiritual, while the brain belongs to the body, which is material. If this should turn out to be true, or even if it should appear to be credible, it does not alter the fact we are considering. No one can produce for his own or for someone else’s observation a soul that is independent of a body or a body (that is of course a living body,—a dead body is merely inert matter) that is independent of a soul. Therefore those who hold that there are two independent realities have to admit that everything happens just as if processes in the brain produced feelings and thoughts in the mind of the soul.
Why should they not? Why should not feelings and thoughts be manufactured in the brain just as any effect is produced when its necessary conditions are fulfilled? May it not be the function of this wonderfully complex organ to produce mind just as other less complex organs produce the secretions that are necessary to the life of the whole? Is it only the subtlety and ethereal nature of the product that make it seem inconceivable that mind can arise from a material process? If so, is there more than a difference of degree between it and the marvellously effective substances secreted by the various ductless glands? The brain is not a gland but it is an organ of such complexity and perfection that it is impossible to conceive a limit to its power.
There are two reasons that seem to everyone who has studied the problem, unanswerable. One is that it is impossible to explain anything as an effect unless we can regard it as strictly commensurate with the cause, and mind is not commensurate with cerebral process. And the second is that the consciousness which arises in connection with cerebral process is not consciousness of cerebral process but of something which is altogether independent of cerebral process, something existing in a different space, it may be thousands or millions of miles away from the brain, and something existing at a different time, it may be ages before or even after the present moment at which the cerebral process takes place.
Let us examine each of these reasons carefully. And first the reason why the form of explanation we call cause and effect and which is the form of all ordinary and scientific explanation will not explain the production of the mind from the physiological processes in the brain. There is no need to discuss any of the philosophical problems involved in the idea of causality, the question is simply one of fact. Is the relation of the mind to the brain one of those relations that can be explained as cause and effect? When excessive light falls on the retina there follows immediately a contraction of the pupils and, if that is not sufficient relief, then a closing of the eyelids. We can analyze this fact into a series of events each mechanically determined by the preceding one. If we start with the light we say that it communicates to the retina a molecular motion which is transmitted by the optic nerve to the brain, from the brain by efferent fibres to the muscles controlling the iris and eyelid which, by contracting or relaxing as the case may be, cause the iris to close the aperture admitting light, and the eyelid to cover and protect the whole organ. We can pursue our investigation further—in fact in either direction to any extent that we please. We can explain the mechanism of the muscles and the supply to them of their energy, the anatomy of the retina and of the nerve fibres and the nature of their function, or on the other side we may explain the excessive light as due to the solar rays and these as produced by the rapid movement of the molecules in the solar mass. We call all this explanation because we can translate every fact we deal with into a common term and state its exact equivalence (theoretically of course) in that common term. The common term is movement. If throughout the whole series there is anything that cannot be resolved into movement then that thing is not in the causal relation. Now suppose that while this event is happening I am conscious. I shall be aware of a painful sensation, aware of the light as a perception, aware of the sun as the object of perception, aware of the immense velocity of the movement of the molecules of its mass and the consequent propagation of waves of light as my conception of the nature of light, aware also of the response my muscles are making to the stimuli my sense organs are receiving as my effort or conation. This awareness forms a connected series but it is not, like the physiological process, a series of movements, and it does not intervene in that series, it does not form a link in the chain of transformations of movement that I call causes and effects. The two series are quite independent as series, and the physiological process I explain by the relation of cause and effect because I find in every state the exact equivalent measured in movement of the preceding state, but the psychical series I explain by association which does not include the idea of equivalence or of measurement. But the important point is this, that the whole of this awareness with all the association that constitutes it a connected series, comes into existence at one precise moment of the physiological process and at no other. This moment is when the stimulus from the sense organs reaches the cerebral cortex. Therefore it seems that the awareness must be produced at that moment by the process, and yet it is impossible that it can be, because it is not equivalent to the energy received by the cortical cells at that moment, it does not change the form of that energy or intercept it or in any way affect the series, that is to say, not in any way that the physiologist can take into account. The physiological process is complete in itself and explained as a series of exactly equivalent causes and effects independently of the awareness that arises at one of its moments.
Let us now look at the second reason, which rests on the nature of what we may call the content of consciousness, meaning the reality of which we are aware in consciousness. Our body is a part of the universe and like the rest of the universe an external object to the mind. Awareness is occasioned by the various influences which affect the surface of our body. Every one of the things we are aware of, supposing of course that there are realities outside of us and that we are aware of them, is outside of the process that is going on in the brain. Even if we include this process as itself part of the universe we are aware of it not immediately in its functioning, but reflectively in explaining to ourselves the function of the brain as an object independent of our consciousness of it. Whatever therefore the nature is of the processes that are going on in the cells and fibres of the cerebral cortex, it is impossible that we should be aware of a real world outside of the brain and also that that awareness should be produced or manufactured in the brain. If we really could believe that our mind was produced in and by our brain, that the brain cells manufactured it or constructed it out of movements sent to it from the skin and sense organs, we could have no assurance that we had any knowledge of reality or that there was any reality to know. We might of course suppose, as some philosophers in former times supposed, that God performs a miracle every time we know anything, and that our only guarantee that there is any world independent of our knowledge, or that our knowledge is of a real world, is our faith in God that He does not deceive us. But considered simply in itself and according to the rules we apply to all our deductions and inferences, if the mind is simply a product of the brain it is then something potentially present in the brain or present in the materials supplied to the brain before it is actually produced, and this something cannot be what is happening outside the brain or that did or will happen outside the brain. It is not the process going on in our brain that we are aware of, but the process going on outside our brain, and although influences reach our brain from outside and although the physiological processes are directly connected with the outside world by the sense organs, yet these influences are stimuli which cannot be conceived as translating anything, even images of things, into the brain as a material out of which the brain might be conceived to produce the mind.
These two reasons are as I have said unanswerable. The first may be summed up in saying that the chain of causes and effects in the physiological process of which the brain is the centre is complete without the intervention of the psychical process, while the psychical process of consciousness, though a connected series, is not a relation of effects to causes but of association of ideas which involves no conversion of energy. And the second may be summed up in saying that knowledge, if it is knowledge of what is outside the brain, cannot be manufactured inside the brain. It is admitted therefore practically by everyone that consciousness is not an effect of process in the cerebral cortex in the same way that the responsive movement of the muscles is such an effect. The brain directly connects the response of the body to the stimulus received but the consciousness that arises in the process is not part of the efficiency. Yet this consciousness is certainly not independent of the process, for if it is why does it arise at one moment and at one moment only of the process? So it has been suggested that it may be an effect of a different kind, an effect that does not absorb energy or give out energy, but still a direct effect of the cerebral process. It is said to be an epiphenomenon, and is compared to the shadow that accompanies a moving body which neither aids nor hinders it though invariably accompanying it, or to the phosphorescence left along the track of the lucifer match we have struck, a one sided effect that cannot in its turn become a cause.
This theory is widely held and is considered by most of those who support the materialist, or what is now more generally called the mechanistic, view, to meet all the difficulties that are involved in the conception of the mind as an effect or product of processes in the body. We may grant at once that so far as the first difficulty we have noticed is concerned, the conception of the mind as an epiphenomenon of the brain is a possible one. It may be that there are after effects of brain processes which though the direct effect of physical movements and of the conversion of energy, are yet not themselves an absorption of energy and do not therefore become an actual calculable part of the causal chain. We could explain in this way why consciousness is not measureable in terms of physical movement, although a product of physical movement. Moreover, so far as consciousness is simple feeling, pleasure and pain, something without distinguishable content and purely an affection, the conception might suffice. But when we consider the real nature and content of consciousness,—the second of our difficulties—the conception becomes impossible to the point of absolute incredibility. Think what this phosphorescence must be and do! It springs up along the track of a wave or current passing through the centres and fibres of the cerebral cortex and when it springs up we are conscious—of what? Of the passing nerve current? No. Of the fact that it has passed? No. Of the stimuli that originated it on the surface of the body? No. Of the direction towards the muscles which are to be set in movement? No. We are not aware of any of these things that actually are occurring but of the world outside us, of the world outside the nerve current altogether, of other persons and of other things than the body and its processes, of things like stars infinitely distant in space, of recollections, of thoughts of things that may have happened at a time infinitely remote from the moment when the passing current, which occupies a limited portion of space and occurs at a definite moment of time, gives forth its luminous trail.
This is the rock on which all these theories that derive mind from body split. We wish to derive a reality that is unconfined in space and unlimited in time from a reality that is limited to a definite portion of space and to a moment of time. Suppose we succeed, we are then in this extraordinary dilemma that the only actual fact is the brain process with its consequence, and therefore the reality we are aware of may be a pure illusion, for the fact cannot guarantee its independent existence, and yet at the same time our only knowledge that there is a brain process with this consequence is an inference from the reality we falsely suppose ourselves to know. The argument therefore is a vicious circle. How do we know that there is a world outside of our body of which the body is a part? Because a certain process has taken place in a certain portion of our brain. And how do we know that this process has taken place? Because we know that there is a world outside of our body of which the body is a part. Everyone has heard the story that used to be told in derision of the Hegelian philosophy, of the German philosopher who preparatory to writing an essay on ‘The Camel’ went into his study to evolve the animal out of his self-consciousness. The story used to end with the unnecessary information that he is there still. Not more impossibly absurd is the idea that our mind is a product, whether we call it epiphenomenon or whether we think of it as a substantial effect, of our brain.
There are other theories besides that of the epiphenomenon which have been proposed as an explanation of the necessary connection of mind and body, but they come to grief on the same rock. There is the very attractive theory of double aspects, very attractive because it offers a direct solution of the apparent dualism, according to which there is only one fact, but it assumes two aspects, a psychical aspect as consciousness, a physical aspect as movement or brain process, just as the movement we see from the shore as the ship tossing on the rolling billows is the same movement which in the ship’s cabin is felt as conscious experience. Then there is the mind-stuff theory, according to which there is a substance of which every mind is composed which is as universal as material substance, a stuff of which every molecule, atom and electron has its share. I need not go into these theories in detail because it must be obvious that they will be confronted with the very same difficulty that we have been examining, the difficulty of the nature of mind and consciousness, that it is awareness of reality not confined to, nor commensurate with, the physical process which accompanies it.
The difficulty is so great that most psychologists and philosophers seek a way of escape, and so they adopt a theory which seems to them to recognize the fact of necessary connection without committing them to any theory as to its nature. This is the well known hypothesis of psycho-physical parallelism. It is a very old theory that was formulated in the 17th century. Leibniz illustrated it by supposing that a clever artificer had designed two clocks whose movement and appearance might differ, but each of which kept perfect time; they would always synchronise and by reading one clock you might always know the exact condition of the other. So he supposed that God at the Creation had made the mind and the body as two clocks which always kept time and therefore seemed as though the state of one was simply dependent on the state of the other. Now it seems to me that everyone who adopts this hypothesis, whatever be the form he gives it, neglects two very important facts. The first is that the hypothesis goes far beyond anything that is justified by experience, it is much more than a mere admission of facts. Experience tells us that a physical process always accompanies a psychical process, but parallelism tells us that there is a one-one relation between the physical fact and the psychical fact. If it does not imply this, it is not parallelism but merely a fact which no one denies, that there is a constant relation between the psychical and the physical. And the second is this, that so far from its being a non-committal hypothesis it is the distinct adoption of a metaphysical theory.
The difficulties of every form of psycho-physical parallelism have been lately very generally recognized; they are admirably set forth in the new edition (1913) of Dr. Stout’s Manual of Psychology, and there has in consequence been an attempt to restate the doctrine of interaction in a form that will not conflict with the scientific law of the conservation of energy. Interaction supposes that the mind actually supplies energy to the body and that psychical reality undergoes conversion into physical reality. It is clear therefore that it is the first, rather than the second of the two difficulties we have stated, that is the real stumbling block to this theory. To overcome it the hypothesis has been suggested that there may be in every case of conscious action a conversion of energy that exactly compensates itself—a simultaneous conversion of psychical into physical energy and of physical into psychical energy, so that the amount of each remains always constant. If this is the last word of interactionism then it seems to me to offer us only a choice of evils. It is possible, in the sense that it avoids the actual absurdity of parallelism, but like parallelism it is a metaphysical theory that goes far beyond any known facts of experience and that throws no light whatever on the facts.
The fact which we have to recognize, and which there seems to be a natural disinclination in the human mind to recognize, is that mind and brain are absolutely incommensurable. They are two realities which meet—that is certain for we never have one without the other—but they meet like the circle and the tangent at one point only. What constitutes this difference and why is the incommensurability absolute? The brain is material and therefore spatial, it is a certain disposition of material elements. This disposition of elements changes but only externally by influences that affect the disposition, but not the elements themselves. It is a delicate organization easily thrown out of balance or destroyed, but what is essential to its existence is material organization. On the other hand, mind is not spatial but temporal, its essential nature is a duration which conserves the past in memory. Imagine that an instantaneous cut is made across the whole of extension. The brain is there but not the mind, for you are imagining extension without duration and mind has no extension. Imagine on the other hand a section through the whole of duration, the mind is there but not the brain, for matter only exists simultaneously in a present, you cannot imagine matter without extension. The mind is therefore essentially a time continuity and the brain essentially a space continuity. Restrict the mind to the actual condition of the brain at any given moment and there is no mind. Cut off from immediate perception all memory and imagination and there is no perception. Theoretically all that there is to perceive in the present is there, but without memory and imagination it can have none of the content or meaning that mind gives to it. On the other hand, the brain can have neither memory nor imagination, for all that it is, it is at every moment. In this lies the true reason why we cannot think that brain produces mind, it would be imagining that space produces time. It would mean that a present activity produces its own past and future. Nor can we escape the absurdity by supposing that the brain does not create the memory but preserves past impressions and ideas in nerve cells or nerve tracks and sets them free or revives them in response to stimuli. It would be easy to show that the same contradiction we have been examining before follows us here, but it is enough to say that such a theory can adduce no facts in its support. There are, however, many facts which seem to contradict it. One of these facts is very remarkable, and of especial interest, because it forms the basis of the theory of memory expounded by Bergson in Matter and Memory. It is the discovery some years ago, confirmed by every case since observed, of the nature of the malady known as auditory aphasia, a malady in which the patient, while still retaining the sense of hearing, has lost the power of recognizing the meaning of words. He seems to have lost his memory, to have forgotten what words mean, without having lost the power of recognizing the things themselves. This malady is accompanied by a lesion of a particular region of the brain, one of the frontal convolutions well known and mapped out by anatomists. The discovery was the first, and also it remains the only successful, localization in the brain of a particular form of memory, that which we call recognition of words. It seemed at first to confirm the generally held opinion that there are special cells in the brain whose function is to store memories, and it was supposed therefore that the injury involved the destruction of a group of cells in which a particular kind of memories was stored, with the consequent result that the memories were destroyed, and that therefore according to the extent of the lesion was the amount of irrecoverable loss of memory. Bergson was the first to show that the facts pointed to an entirely opposite conclusion, that the memory was still in existence and unimpaired, but that what was thrown out of gear by the injury was the mechanism by which memory inserted itself in action. It was not a psychical reality but a motor mechanism that was affected. This view is now adopted by many of the most prominent psycho-physiologists, but even those who do not accept it no longer quote aphasia as proving that psychical reality is produced by or stored up in material structures.
If we recognize this fact that in mind and brain we have two realities that are incommensurable by their very nature, but which function only in union with one another, we may understand why everything happens just as if the one were produced by the other. Why it is that when the Titan cleaves the head of Zeus the fully armed Athene springs into existence. To understand it we must see what it is that consciousness does, the purpose it fulfils. What we call consciousness is not the whole of mind. If it were, if part of mind were not always something of which we are unconscious in exactly the same sense that the material reality we perceive is always a part of a reality we are not perceiving, then the arising of consciousness at a particular juncture would be as inexplicable a miracle as that of the sudden existence of the fully armed goddess. The union of mind and body is in action. When we regard the facts from the standpoint of action, all difficulty in regard to them disappears. We can see the part the brain plays and the part the mind plays as clearly as we can see the part the senses play and the part the muscles play. First of all we see why there must be union, because without the body, the mind, whatever it is, whether or not it is a separate as well as a distinct existence, can do nothing. The body is the instrument of the mind’s activity. And without the mind the body is the blind play of physical forces. Take them in their union and we see at once what the brain is—a great exchange office or switchboard, where the stimuli that come from the outer world are received and switched on to their responsive movements. We see also what the mind is, it is the whole scheme of our activity, and we see how it functions by bringing the field of our activity to consciousness. The stimuli received become affections and are perceived, and memories give meaning to perceptions, and delineate prospective actions and so direct the response. It is therefore at this point, when the stimuli from the senses reach the cerebral cortex and before they issue in actions, that consciousness functions. If it is to serve action it is only there that its service can be effective. Naturally therefore it seems as if it is the functioning of the brain at this point that produces the mind.
This then is the answer we give to the question why it is that the mind seems to be, and yet cannot be, produced by the brain. The mind guides and controls what the body does, it directs the body’s actions. There is only one point at which control of action can be effective, and that is where the responsive movement of the body to a stimulus received is initiated, that is in the cerebral cortex. Because the mind is acting there it seems to come into existence there. That is our reason for saying that everything must happen just as if the mind was produced by the brain. But the mind is a reality of an entirely different order to that which alone can be produced by physical movement or by the material disposition of such things as atoms and molecules. That is our first reason for saying the mind cannot be produced by the brain. The brain is a certain group of material particles, or a certain equilibrium of physical forces, occupying a definite position in space, which responds to movements by transmitting movements. The mind is a continuity of time, a duration, a perceiving of what is outside the body, a remembering of what is over and past, an imagining of what is not yet. None of these characters are spatial. That is our second reason for saying that the mind cannot be produced by the brain.
- H. WILDON CARR.