by     Reginald O. Kapp




THERE are two mind-body problems; or, if it be preferred, two distinct sets of such problems. The one set is concerned with the action of body on mind and the other with the action of mind on body. Both are equally important; both have attracted men's occasional attention at least since the days of Aristotle; both have become somewhat prickly subjects, liable to arouse violent emotions among the adherents of the many "isms" that isolate philosophers from each other; both have been discussed far too much in the spirit of the debating room and far too little in the spirit of scientific research.

Philosophers, it must be remembered, seek to perfect the instruments of knowledge rather than to find knowledge itself. This is why philosophical method, fruitful perhaps in the fields of ethics and logic, has led to nothing but rival theories about the nature of reality. Everything that is known about the world in which we live has been discovered by the application of scientific method. It is high time that mind-body problems were also subjected to scientific method. But at present, as I have pointed out in the Preface, scientists become a little impatient when their attention is drawn to any of these problems; they tend to shy away from them.

The set of problems that is concerned with the action of body on mind is associated with that part of the central nervous system that physiologists have called the afferent system. This connects the organs of sense perception with the brain. Happenings that stimulate the eyes, the ears, the fingertips, in fact all happenings that constitute sense data, cause messages to pass through the afferent nervous system to the brain. These messages are appreciated by the mind as perceptions. By the time they have become conscious, physical data have been translated into mental ones, waves of a suitable frequency into the sensation of light, vibrations in the air into the sensation of sound, molecular movements into the sensation of heat, a molecular bombardment of the finger-tips into the sensation of touch, chemical structure into the sensation of flavour.

The translation is thorough; the distinction between the reality discovered in physics and the reality revealed to our senses is radical. There is but one world and yet it can be described in two languages that seem to have no relation to each other. Hence the first set of mind-body problems. How is the translation from the language of physics to the language of sense data performed? Why do we not appreciate the world around us as physicists know it, light as waves in space, sound as vibrations of the air, the flavour of sugar as a configuration of atoms in a chemical structure? Why this strange difference between the subjective world of percepts and the objective world that is described in physics? Why indeed is there such a thing as a subjective world? What meaning can we give to the concept subjectivity? We know from experience that there is such a thing as subjectivity, but we have not yet successfully fitted it into the jigsaw puzzle of science.

In the process of translation from objective to subjective reality the body does something to the mind. What is it? Could an answer to this question be found a step would be taken towards a solution of the first of the two sets of mind-body problems, the set that might conveniently be called the Problem of Perception.

This problem is important and belongs rightly to the domain of science, unwilling though scientists have been to admit it to their domain. But it is not the one that I propose to discuss here. I have to limit my field of enquiry and have decided, on this occasion, to limit it to the other set of problems, to the set that is concerned with the action of mind on body. This set of problems is associated in physiology, not with the afferent, but with the efferent nervous system.

The efferent nervous system is connected between the brain and the muscles. It is concerned, not with perception, but with activity. Voluntary contraction of a muscle occurs only when a stimulus passes from the brain through efferent nerves to the muscle. And as the stimulus that is applied to the efferent nerves occurs as the result of mental activity, as the result of a thought, a wish, we observe in the stimulation of efferent nerves the action of mind on body. The many questions that arise from this observation make up together what can conveniently be called the Problem of Control. The Problem of Perception and the Problem of Control jointly constitute the larger Problem of Interaction.

There are plenty of theories in which it is claimed that this problem has been disposed of. Some are idealistic, some materialistic, some agnostic. In some it is declared that the problem has been solved, in some that there is no problem to solve, in some that this is not a proper problem for scientists to tackle. Like all the philosophical "isms" that flourish side by side, these theories only remain plausible so long as sundry true and relevant facts are ignored; facts of physiology, such as the way nerves and muscles work: facts of physics, such as the principle of conservation of energy: facts of common experience, such as that people do think, that things are sometimes done with a purpose, that specifications are sometimes followed. The idealists make out an excellent and convincing case for their theories by ignoring the physiological and physical facts. And the materialists are able to appear very scientific to those who do not notice how lightly they dismiss all the facts of subjective (and not a few of objective) significance. A question that introduces any of the ignored facts is all that is needed to show that those are equally naive who claim to have solved the problem and who claim that there is no problem to solve. This is why most of those who discuss the problem do not like questions; they prefer answers.

Nevertheless, be it popular or not, questions must be asked with the most uncompromising clarity. I will not apologise for saying so again and again. Nothing makes for looser thinking than answers to questions that have not been formulated but are only implied. This is why I have set myself the task of putting into words all the difficulties that are inherent in the Problem of Control, of drawing attention to the disturbing facts that make an easy solution impossible, of asking all the awkward questions that I can think of. I am well aware that in the no-man's-land where the present subject has hitherto been discussed it is considered reprehensible to formulate a problem without offering the balm of a theory. But yet I have no choice but to embark on this disappointing course. The most I shall be able to do will be to suggest which field might be usefully explored by those who would seek a solution. But whether the solution will be found in that field, or in another, or whether it will never be found, I cannot say.

One result of the prevalent disinclination to ask questions is that there is not even a suitable language in which the questions can be clearly formulated. So I have either to use cumbersome, vague and ambiguous terms or coin a few new ones with a precise meaning. I prefer the latter course and the most important of the words that I shall use as new technical terms have been already defined in Chapter IV. But definitions are not very informative and illustrations are. So I shall introduce the new terms with the help of an example. (When I say an example I mean an example. I do not mean an analogy. It is rather important that this be realised. For in philosophy analogies may serve a useful purpose. But they can only mislead in scientific argument.)

I shall choose as my example an occasion when a mind is doing something quite ordinary, when no creative act is being performed, no particular skill is manifest, no high degree of intelligence displayed. It is all too common to illustrate the action of mind on matter by reference to the plays of Shakespeare or the discoveries of Newton. When this is done the impression is created that the subject can only be properly discussed on a sublime level, that the Problem of Control arises only when the controlled implement is a pen and does not arise when the controlled implement is a shovel. And such an impression is very misleading. The problem arises from facts of everyday observation.


Let, therefore, my illustration be drawn from a place where rough work is being done. I shall choose a foundry. This is a large rectangular building. At the end of it a heavy casting is being picked up by a travelling crane and transported to the other end where it is to be deposited on to a waiting railway truck. The crane girder spans the width of the foundry. It moves from end to end of the building on rails, which are set on stanchions ranged along each wall. Other rails at right angles to these are carried by the crane girder. A wheeled truck, called a crab, travels on them. While the whole girder can travel from end to end of the foundry the crab can travel along the girder from side to side. It can, by a combination of the two movements, be brought above any part of the floor. The crab carries a drum on which steel wire hoisting cables are wound. From these hangs the great crane hook. The casting is held by a sling of hemp rope suspended from the hook.

There are separate electric motors for movement of the girder, movement of the crab and rotation of the drum. Adjacent to each motor are devices known as contactors, by means of which the current to the motor can be switched on or off. These devices are operated by powerful electro-magnets, the current for which is provided by a battery of electric accumulators. The switches for energising the electro-magnets are in a control cabin, so placed that it commands a good view of all that goes on in the foundry. Rheostats for control of the speed of each motor are also placed in the control cabin.

Now let us ask the foreman what causes the casting to move from its initial position at one end of the foundry to its final position on the waiting railway truck at the other end.

Surely, it may be said, the answer is very simple. But is it? The answer is easy certainly, but not quite so simple. For there are two distinct answers and neither is correct unless it be completed by the other. The foreman is well able to give both. But he may give one only.

He may say that the cause is a supply of electrical energy from the local power station. This is true, but I doubt if he will say it. I think he will say that the cause is a craneman, whom we can meet and see at work if we care to climb up into the control cabin. The power station provides the energy, the craneman the control. And both are needed to ensure that the casting shall reach its specified position.

In this instance the function of each is easy to state. The function of the energy is to ensure that the casting shall move at all, the function of the control to ensure that it shall move on to the waiting railway truck as called for in the written instructions that have been sent to the fore- man. Because of these instructions philosophers would say that the movement of the casting was a teleological process. They would call the energy the vis a tergo and they would refer to the instructions, in -not the happiest of phrases, as the final cause.

In our foundry the crane cabin is connected to the crane motors by sundry wires and electrical devices. The purpose of these wires and devices is well known. It is to enable the craneman to control the movement of the casting; the control, one can say without doing violence to the use of language, passes through the wires and devices to the crane motors. And control is but a particular example of the more comprehensive concept to which I have given the name diathesis. I propose to show that this is something much more important than is often realised. So long as one concentrates one's attention exclusively on the energy required for a process one may readily convince oneself that there is no such thing as a mind-body problem. But when one has become aware of the contribution made to a process by diathesis one can no longer succeed in ignoring it.

So let us seek to understand the nature of diathesis, to explore the paths along which it can be traced, to know by what to detect its presence, to discover the laws to which it conforms, if possible to make quantitative state- ments about it. Let us do with it what one ought to do with every proven reality and admit it into the domain of science; let us give a name to the study of diathesis. I suggest "diathetics".

A good way of revealing the reality and significance of diathesis is to speak of it as of a commodity, just as one speaks of energy. I am well aware that there are logical objections to speaking thus both about energy and about diathesis; but it would be bad exposition to hold up the train of thought that brings this useful concept while a discussion is going on about the way it ought to be talked of. So I shall have to delay a justification for my manner of speaking about diathesis until suitable occasions arise. This question of method will be discussed more fully in Chapter XVI, by which time its nature will have become more apparent than it can be at this moment.

The first thing to be done is to distinguish clearly between diathesis and energy. Let us commence our study, therefore, by comparing the paths along which, respectively, the energy and the diathesis reach the casting in our foundry. These paths are shown diagrammatically in Fig. 1. They are admittedly very much oversimplified in the figure and only a few of the stages are labelled through which each commodity passes. In fact each path receives sundry tributaries not shown on the diagram. These are important and will be discussed later. It can be done more profitably after the distinction between the two main paths has been firmly grasped.


There is so much misunderstanding of the nature of energy among non-physicists that I propose to discuss in some detail the path for the energy before I say anything more about diathesis.

On its way to the foundry the energy has followed a long and winding course. It reached its destination finally through electric cables and its immediate source is the electric power station. But it did not originate there. Where and when it did originate no one can say. The earliest knowledge we have of it is that, millions of years ago, it was in the sun. There it existed as the potential energy of protons and electrons. As a result of a complex process with many intermediate stages these protons and electrons came into combination to form helium nuclei. In the process some of their potential energy was converted into radiation.

Undergoing on its way many vicissitudes, many conversions and reconversions from one form of energy to another, this radiation escaped from the sun's deep interior to the surface. Thereafter a minute fraction arrived, after an eight minutes' journey, on our earth. A minute fraction, again, of this radiation fell on the green leaves of those giant forest trees that grew in bygone geological times. Some of the radiant energy was absorbed by the leaves in a process known as photo-synthesis. In this process carbon atoms, contained in molecules of carbon dioxide in the air, were separated from the oxygen atoms and stacked in the tissues of the plant. The energy required to disrupt the carbon dioxide molecules was obtained from the energy in the radiation that fell on the leaves. This energy reappeared as potential energy in the carbon compounds into which the carbon entered after it had been secured in the tissues of the plant.

These compounds reached the trunk and branches of the trees and the energy was stored there. When the trees had died, fallen, and become covered by layer after layer of soil, their substance gradually changed to coal. But the energy did not change. It remained in its chemical form as the energy stored in carbon, about 11,000 British Thermal Units to every pound. Long, long afterwards men dug some of the coal out of the ground and brought it to the power station where it was burnt in the furnaces.

In the power station it has undergone numerous changes in quick succession. Its first conversion was from chemical energy in the coal to radiant energy in the hot flue gases. As water circulated in the boiler tubes the water became hot and turned to steam. The radiant energy passed into this and appeared as heat and pressure.

Passing through the turbines the steam lost both some of its high temperature and some of its pressure. It left the turbines at a temperature of about 1000F. and a pressure of about one thirtieth of atmospheric pressure. In this condition it contained rather less energy than when it was in the boilers. The difference appeared first in mechanical form as torque in the turbine shaft and then as the electrical energy supplied from the station.


Now for the path for the diathesis. The source of the diathesis is as unknown as that of the energy. It is what we are hoping to discover. The first stage along its path that can at present be defined with any confidence is in the craneman's brain. As every physiologist knows, this is in control of his nerves; his nerves are in control of the muscles of his hands; and these are in control of the small switches and rheostats in the crane cabin. From there the diathesis is carried by light electrical currents to the electro-magnets, which are, in turn, in control of the contactors. The contactors are, lastly in control of the crane motors.

The above is a very rapid and superficial survey of the path for the diathesis. It will have to be surveyed very much more thoroughly in due course. Suffice it to note for the moment that this path is distinct from the path for the energy, that it is a true path, and that it permits the passage of something as real as energy. The organisation in the foundry depends on this path as much as on the one that brings its supply of energy. A broken wire between the crane cabin and the contactors or a severed nerve in the craneman's arm would interrupt the flow of diathesis. And after the interruption the organisation in the foundry would be impaired. What is commonly called order depends on an adequate supply of diathesis.

It is strange how little this is appreciated in the no-man's-land where men write for or against belief in interaction. The arm-chair philosophers who indulge their thoughts in that place never seem able to distinguish between energy and what they call order. They speak always as though order and organisation depended on a supply of energy only. Some of them go so far as to say that organisation is energy. In the no-man's-land where men like to indulge in theory spinning one word is as good as another. It is too much bother to pause and consider whether there is any difference between energy and organisation.

This confusion is the seed of many of the weeds that grow so profusely in the no-man's-land. That it should occur to laymen, who do not know what, in science, energy is, might be expected. But that scientists should be equally confused, as many of them are, is surprising indeed.

The reason for the confusion is, no doubt, that those who write on philosophical aspects of science rarely think about foundries and 'similar places where the distinction between the path for the energy and the path for the diathesis is quite obvious. They dwell for choice on more abstract examples in which the distinction can more easily be overlooked.


Our foundry is, of course, neither a recondite nor a rare example of a place where energy and diathesis both contribute to a process. Both have contributed before in many of the places that lie along the path for the energy. I have already mentioned that Fig. 1 is oversimplified. Tributaries of diathesis ought to be shown there meeting the path for the energy in sundry places. They ought to be shown in all places where men have done something to control the direction taken by the energy.

Such tributaries occur in the coal mine, where the coal, with its store of energy, is hewn, loaded on trucks, brought to the bottom of the shaft, and then raised to the surface. They occur in the railway goods yard, where the coal laden wagons are marshalled; in the boiler, turbine, and switch houses of the power station. From the moment when the coal was disturbed in its resting place deep under the earth the path for the energy has been doubly determinate. Its course has depended partly on diathesis supplied to it by men and women. Were it not for their contribution the energy would not have reached the foundry. See Fig. 2.

In human affairs diathesis is indeed an important commodity. Without it civilised man could not survive. And neither could uncivilised man. Without diathesis there would be no clothes, no houses, no books, no cooked meals. For all these things can only come about as the result of a controlled operation. They cannot result from a supply of energy without a supply of diathesis. Yes, and without diathesis there would be no machines. Strange, therefore, that a philosopher should ever quote machines as proof that there is no such thing as diathesis, as in effect the philosophers of the mechanist school do.

Our factories, our shipyards, our offices, our council chambers depend on a copious and continuous supply of diathesis. It reaches its objectives by paths that are sometimes quite short and sometimes much longer than the distance from the crane cabin to the crane motors in a foundry. Some of these paths span the oceans, so that a person in London may control a process in New York. Thus does the human race weave incessantly over the earth a close meshed network consisting of paths for diathesis. And were one to follow any path back towards its source one would always reach a place similar to the one reached in our foundry, namely a human brain. Sometimes it would be a powerful brain, sometimes a very ordinary one. It matters not. If the brain is doing no more than control a simple and insignificant movement that brain is passing diathesis through the efferent nervous system.

Even the foundry accounts provide evidence of this. The cost of the casting when it leaves the foundry is made up partly of the cost of the energy and partly of the cost of the diathesis expended on it. The energy is used to melt the metal and move the materials. It is, in this example, the smaller part of the total cost. The greater part is the cost of the diathesis expended on the casting by managers, office staff and workers. A measure of diathesis, though not a very scientific one, is man-hours. And these are in no sense a measure of energy.

Moreover, what appears in the foundry accountant's books as the cost of electrical energy appears mostly in the books of the electricity supply undertaking as the cost of diathesis. For only a small part of this cost is represented by the cost of the coal in which the energy reached the power station. Even when the energy supplied to an electric power station is obtainable for nothing, as in a hydro-electric station, the electricity is little, if anything, cheaper than when produced in a thermal station. For most of the cost is in sundry wages bills. So, in turn, is the cost of the coal delivered from the mine the cost of the diathesis expended in raising it out of the ground. The commodity that men buy and sell in this world is always diathesis. Energy is not bought or sold. It comes to us, literally, as a free gift from the sky. For its source is the light and heat that the sun, without making any charge for it, sheds generously on the earth.

The energy can be measured in kilowatt hours, or foot pounds, or British Thermal Units, or any other units. The effort made by managers, office staff, bus conductors, dentists, cooks, singers, cannot be measured in any such units. No scientific units for the measurement of diathesis have ever been set up. Perhaps it will be done some day. But one is handicapped in discussing diathesis quantitatively, or in any way at all, so long as the belief remains prevalent that diathesis is a form of energy.

So let me explain, for the benefit of those likely to be misled by the amateur philosophers, that Newton's brain contained less energy than a medium sized lump of coal. And moreover, its expenditure of energy was at much the same rate soon after his death as it had been before. But its expenditure of diathesis occurred at a prodigious rate while he was alive and ceased completely with his death.

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