MIND, LIFE AND BODY

by     Reginald O. Kapp

PART III - THE PROBLEM IN TERMS OF DIATHETICS

Chapter XVI - MIND AND THE FUNCTION OF TIMING



1. CONVERSION OF ENERGY

LET us keep our attention for a while longer on the material systems that I have called paths for diathesis and of which an example is provided by the path from the craneman's brain to the casting in our foundry. And let us dwell in particular on a characteristic of every such path that we shall soon find to be very relevant to our enquiry. It is this. The path is so constructed that the diathesis is converted at every stage from one form into another.

It will help towards an understanding of what I mean by conversion of diathesis if I refer for a moment to the more familiar concept of conversion of energy. The energy that passes through an electric power station, for instance, appears in many different forms. It reaches the station as energy bound chemically in coal. Portions of this energy, gradually reduced by sundry losses, appear successively as energy of radiation emitted by the white hot furnace gases, as the potential energy of steam at a pressure of some 900 pounds per square inch in the boilers, as the kinetic energy of molecules of superheated steam as they pass with a high velocity through the turbines, as a torque in the turbine shaft, as a magnetic field in the space between the rotor and the stator of the electric generators, as kilowatt-hours passing through the cables that take the energy to the consumers. Thus a number of happenings in the power station that are in appearance very different from each other all have this in common that they reveal the passage of the same energy.

One could not view the sequence of events in the power station in that way unless one thought of energy as a commodity. And people have not been doing so for very long. Indeed they did not think of energy as a commodity in Newton's day. Nor did anyone think like that in the days of James Watt. Men thought then that only one commodity, namely steam, flows through a steam engine. They did realise that the steam exercises a force on the piston and thus causes it to move. They were right. But yet, so long as they thought thus they had but little understanding of the meaning of thermal efficiency.

Only when they thought in terms of another commodity besides the steam, to which they gave the name energy, did they begin to formulate the laws of thermo-dynamics. Only then did they learn to get as much work out of the coal as they could. When they had formed this new idea of a second commodity that enters the engine along with the steam they realised that the energy does not entirely follow the same path as the steam.

The steam enters through the stop valve and leaves through the exhaust. The energy too enters through the stop valve; and most of it leaves through the exhaust. But a not very large fraction leaves, most surprisingly to those not familiar with the theory of heat engines, through the engine shaft. This alone is the fraction that is useful, and the aim of the designer is to increase it. In the James Watt engine the useful fraction is only a few per cent of the whole. In the best steam turbine it approaches thirty per cent. This great improvement would never have been brought about if engineers had continued to think in terms of force only. It was by thinking of energy as a commodity arid by attempting to divert as much as possible of this commodity through the engine shaft to the places where it could serve a useful purpose that improvements were achieved in the design of heat engines.

Thus does scientific progress depend as much on new concepts as on new discoveries. One of the most valuable things that Newton did for science was to give us the concept of force. This is defined as rate of change of momentum. It is also the product of mass and acceleration and is used to interpret changes in the velocity of a body. It has been said by some philosophers that the concept force is a highly artificial one, devised merely so as to substitute one way of saying things by another. For all I know these philosophers may be right. But it does not detract from the usefulness of the concept.

When force is multiplied by distance a new concept arises, energy. And I have known those who say that force is an artificial concept to say that energy is the only physical reality. Again this may be true for all I know. But it seems rather odd that a very artificial concept should become a very real one when multiplied by distance. And whether or not energy be more real than force it is perfectly true that science made as big a bound forward after men had begun to concentrate their attention on the product of force arid distance as it made in Newton's century after they had begun to concentrate their attention on the produce of mass and acceleration.

It is possible that science may be making another equally big bound forward in this century from concentrating attention on the product of energy and time. For this product is called action and it is now known that all physical changes occur as multiples of a certain small and indivisible unit of action called a quantum. An immensely increased understanding of the structure of the world has already been gained with the help of the concept, be it a very artificial or a very real one, that is reached when force is multiplied both by distance and by time.

However this reference to action was a digression and I must resist the temptation of pursuing it further. What is not wholly a digression is that a notion as fruitful to science as that of treating energy as though it were a commodity should also be such an odd one. Pedantic minds would never have thought of anything like that. Meticulous logicians would not have tolerated it. Had a philosopher been consulted when scientists decided to speak of energy as a commodity he would have advised strongly against it. He would have brought the learning of centuries to the proof that the proposal was absurd, that it flouted the most elementary rules of language, logic and common sense.

For the word commodity suggests a substance capable of being stored in a container of some sort, capable of flowing along some kind of channel, capable of being divided up into small quantities or combined into large ones. How easy it would have been for the all-too-clever to prove that it is quite absurd to say that energy, which can be defined as the product of force and distance, rate of change of momentum, or the product of a mass and half the square of a given velocity, can have such properties. In fact few of the things that one may read in textbooks about energy would suggest to dull minds that it may legitimately be treated as a commodity. It is said to be a capacity for doing work. But can a capacity for doing anything be stored in a container, can it flow from place to place, can it be divided up into a lot of little capacities or combined into one big one? So one might have asked rhetorically. And it must at first sight seem equally unjustified to think of what may be a bending moment as capable of flowing through space, of the product when a mass is multiplied by half the square of a velocity as stored in some container, of foot pounds as flowing out of the steam and into the shaft of an engine. Energy is said to be contained in a moving body by virtue of its velocity, in coal by virtue of its chemical constitution, in a loaded beam by virtue of the bending moment applied to the beam, in empty space by virtue of the electro-static or magnetic field in the space. A strict logician would have every reason to object to such a loose way of speaking. He would say that this was to confuse the container with the contents. But it is fortunate that no such dull and pedantic objections were raised in the early days of thermo-dynamics. For the notion of treating energy as a commodity was a stroke of genius; and genius defies the rules.

2. CONVERSION OF DIATHESIS

And now to return to the concept of diathesis as a commodity. I am not concerned here with the question whether or not it is as useful as the concept of energy as a commodity. I doubt if it is. But I am concerned to point out that, though it be as intangible as the energy that passes out of the steam and into the engine shaft, diathesis is a scientific reality. Let it suffice that it helps towards an understanding of the Problem of Control when, on suitable occasions, one thinks and speaks of diathesis as a commodity. Such an occasion arises when one is considering any sort of indirect control.

A few examples will illustrate this. A pilot on the bridge of a large vessel spins the wheel about its horizontal axis. When he does this he is controlling the course of the vessel. But the control is indirect. The performance of the vessel is not under the direct control of the pilot; it is only under the direct control of the rudder. What is under the direct control of the pilot is the performance of the wheel. And the nature of this is different from the performance of the vessel. When the wheel is spun quite a lot about its horizontal axis the vessel changes course only slightly. And, moreover, it continues to change course so long as the wheel is held there. The angle through which the wheel has been rotated does not determine the course of the ship but the rate at which the course is changing.

In this example there is an equivalence between the two performances. The complicated gear between the wheel and the rudder ensures it. Consequently anyone who was watching what happened to the wheel would know something of what was happening to the ship. And this equivalence can be expressed by saying that the same diathesis is applied both to the wheel and the whole vessel. But as the two performances that are equivalent are also different in nature, the one being a large turning movement of a wheel and the other a small rate of change of direction, one must add that the diathesis has been converted from one form to another during its passage along the path from wheel to rudder.

There is such conversion whenever control is indirect. In a microscope the turning of a micrometer screw is converted into a change in the distance between the lens and the slide. In a typewriter the tapping of keys on a stationary keyboard is converted into the printing of letters on a moving sheet of paper. When a song is being broadcast the sounds that are heard as music, sounds that are no more than a specific performance of the air under the singer's direct control, constitute a diathesis that is converted into other forms many times in the transmitting and the receiving apparatus.

So it is in our foundry. The performance of the crane- man's hands, the performance of the electric currents that flow between the crane cabin and the crane motors, the performance of the casting, these all differ from each other very much. Yet they are all equivalents of each other. A person who knew enough about the way in which the apparatus in the control cabin is connected to the crane motors would know what was happening to the casting merely by watching the performance of the switches and rheostats. He would also know it, at least in theory, from studying a record of the electric currents that flow in the sundry wires that connect the apparatus with the motors.

3. DEFINITION OF A MECHANISM

A mechanism may serve for conversion of energy from one form to another. But so may a thing that would not, by the common use of language, be called a mechanism. There is conversion from kinetic to potential energy whenever a leaf is tossed by the wind, whenever water evaporates from a puddle and rises into the air, whenever a breaking wave fills a rock pool a little way up the shelving beach. And conversions from potential to kinetic energy occur even more frequently. There is conversion of energy in every change, be it an orderly or a chaotic one.

Not so with conversion of diathesis. By definition diathesis implies order. Its conversion can only be effected with the help of a device designed for the purpose. And it is usual to call such a device a mechanism. Indeed I cannot think of any occasion for the use of a mechanism except when it is required to convert diathesis from one form to another. This is the use to which we put push buttons, switches, triggers, taps, levers, and, in fact, every mechanical device that serves any sort of purpose. One cannot find anything that converts diathesis from one form to another for which the word "mechanism" would be inappropriate. Nor could one, without doing violence to the meaning of words, apply the word to anything that does not serve for the conversion of diathesis.

So a suitable definition of a mechanism is: A mechanism is a device for the conversion of diathesis from one form into another. This definition includes everything that it is usual to call a mechanism and excludes everything that one would not usually call by that name. I am unable to suggest any other definition that would do the same.

Conversion, I must insist, not creation. All the mechanisms with which we are familiar are instruments of control, none is an originator of it; they all serve to transmit diathesis and to convert it into other forms. But the diathesis has to be applied to everyone of them, be it through a lever, a trigger, a push button, a handle or any other controlling device.

Would that those who dwell in the no-man's-land of which I have spoken in the preface and spin their engaging theories there could understand this. Then they would discover that the brain, by virtue of being essentially a mechanism, is limited to the purposes that a mechanism can serve. That it can, for instance, be used to make a choice effective but cannot itself exercise a choice; that it can transmit and convert diathesis, but cannot create it; that any device that ingenuity can contrive, no matter how elaborate, no matter how well equipped with thermionic valves and those appliances that are nowadays incorporated in servo-mechanisms, that any mechanism whatever works only when it is controlled.

Yet the dream of producing a mechanism that exercises autonomous choice, that no man need ever control or adjust, that dream persists. And it will persist so long as the theme mind, life and body is studied only in the no-man's-land where, as I have said before, one word is as good as another, where no one is prepared to make the intellectual effort required to understand the distinction between an instrument and an originator, between causation with control and causation without control, between the conversion of a commodity into a different form and the creation of the commodity., between energy and organisation. But let me return to the true purpose served by any and every mechanism.

The function of all man-made mechanisms is to replace a performance that is inconvenient, if not impossible, for human beings by one that is more convenient. To replace the diversion of the course of a vessel weighing thousands of tons by the spinning of a steering wheel; to replace the writing of letters by the tapping of keys; to replace minute adjustment to the distance between the lens and the slide of a microscope, an adjustment for which human fingers are too clumsy, by the turning of a micrometer screw; to replace the manipulation of a heavy casting by the operation of switches and rheostats. There is no limit to the number and variety of forms into which any diathesis may be converted by suitably designed mechanisms. The controlled performances may constitute changes in the positions of things, in their size, their volume, their intensity, their velocity, in any such features as colour, texture, chemical constitution. But when the converting mechanism is well designed the performance under the direct control of human operators is always adapted to the physical characteristics of human beings, to their stature, their strength, the reach of their limbs, the number of fingers on each of their hands. If there be a planet on which octopuses have evolved to the stage when they use tools and make machines we may be quite sure that these differ from ours in the way they are operated. The controls in a motor car designed by the octopuses will be of a different number, differently spaced, differently manipulated from those in our own cars.

4. PRIMARY DIATHESIS

What is true of the portion of the path for diathesis that lies in our foundry between the crane cabin and the .casting is true of every portion. It is true of the portion that lies between the craneman's brain, where the primary relays are, and his hands. There is repeated conversion of diathesis from one form into another all along this path. The performance of the muscle fibres is the same diathesis as the performance of the switches and rheostats, although its appearance is quite different. It is also the same diathesis as the performance of the casting. A person who knew enough about the way in which the craneman's muscles are connected to his joints would, at least in theory, know what the craneman was doing to the apparatus under his control merely by watching the drill performed by the muscle fibres. If the fibres were to perform a different drill the casting would move differently. This is why the living systems that are studied in physiology are correctly described as mechanisms. They conform to the above definition. If they served some purpose other than conversion of diathesis, or if they served no purpose at all, they would not be called mechanisms.

The drill performed by the primary relays in the craneman's brain is also the same diathesis as that applied to the casting. A person who knew enough about every mechanism between these relays and the casting would, at least in theory, know for each stage along the path what the controlled performance was. He would know what the muscle fibres were doing, what the craneman's limbs were doing, what the switches and rheostats were doing, what the casting was doing. All these performances would be different if the drill performed by the primary relays were different.

Let this drill be called a. primary diathesis.

I have already said that every path for diathesis on which civilisation depends passes through a human brain. At the beginning of every such path there is a primary diathesis. Our most trivial gestures, no less than our most important achievements, depend on the drills performed. by primary relays. It depends on such drills what fields are ploughed, what houses are built, what machines are assembled, what ships cross the oceans, what meals are cooked, what words are spoken, what books are written, what songs are sung. A primary diathesis is a very universal phenomenon. It is the basic form of diathesis. All other forms are derived from it.

And in the same sense primary relays must be regarded as the basic form of mechanism. Although one may find the greatest conceivable variety of mechanisms ranged in cascade along a path for diathesis, each serving the purpose of converting diathesis from one form into another, one must always find the same kind of mechanism at the very beginning of the path. Primary relays are the only devices that are absolutely indispensable. Without these all our tools and gadgets, all our machines, all the devices that one can think of for converting diathesis from one form into another would be useless. For there would be no diathesis to convert.

5. THE CONTROLLED FUNCTION IN A PRIMARY DIATHESIS

In every diathesis one can speak of a controlled function. And this function is different at every conversion. By the term I mean the operation applied to a mechanism. The controlled function may be the turning of the wheel or a micrometer screw, the insertion of a key, the raising of a latch, the pressing of a trigger, the drawing of a line across a sheet of paper; there is no limit to the variety of controlled functions that can be applied to and by suitably constructed mechanisms. To say controlled function is only another way of referring to the method by which the mechanism is worked.

In a well designed path for diathesis the controlled function is adapted everywhere to the mechanism that has to exercise it. The controlled function in moving the casting is adapted to the capacity of the crane motors; the controlled function in operating the switches and rheostats is adapted to the capacity of the craneman's hands; the controlled function in operating his muscle fibres is adapted to the capacity of the endplates by which the nerves are joined to the fibres. As I have pointed out above, the controlled function in operating motor-cars to be driven by a race of superintelligent octopuses would be adapted to the capacity of those many armed creatures.

It follows from this mutual adaptation that one can draw some slender inferences about the system that operates a given mechanism when one knows something about that mechanism and that one can, conversely, draw some slender inferences about the mechanism when one knows something about the operating system. From the weight of the objects to be moved in a foundry one could draw some inferences about the horsepower of the crane motors and from the horsepower one could, conversely, draw some inferences about the weights. From the number, arrangement and spacing of the controls in our hypothetical octopus driven motor-cars one could conclude a few things about the strength and structure of the drivers, just as from observations of the octopuses one could say, at least in very general terms, in what ways the arrangement and spacing of the controls in their motor-cars would differ from ours.

These considerations lead naturally to a little speculation about the controlled function in a primary diathesis. It must be adapted to the capacity of a diathete, of an influence without location and unable to transmit energy. Any theory that may be formed about the construction and method of working of a primary relay must be consistent with this fact. If more that is relevant were known about a diathete one might be able to infer more about a primary relay. But more is not known and so there is little to go on for those who would like to form theories. But at least one can say that a primary relay must work on a principle quite unlike any with which we are familiar. For every known mechanism is such that the controlling device does interchange energy with it. A facile explanation of the way control is initiated is not to be expected. The Problem of Control cannot be attractive to those who like easy solutions.

Perhaps the problem will never be solved. But I would like to see an honest, determined and concerted effort made to solve it before science confesses itself beaten. And in this effort attention will have to be concentrated on the sites of a primary diathesis; they are the places where a diathete meets matter. One cannot expect to discover anything about a primary diathesis by examining controlled functions anywhere else.

Though the same energy that enters a power station bound chemically as energy stored in the coal appears later as the energy contained in steam at high pressure, one could not find out anything about the chemistry of coal from observing the conditions in the turbines. This is because at each conversion energy takes on a different form and one not determined by the form it previously had. It is the same with diathesis. By observing the casting in our foundry one could not infer what sort of switches were controlling the motors. And one should not expect to find out anything about the controlled function in a primary diathesis from observation of any other mechanisms except primary relays. To understand, in other words, how mind controls matter one must investigate the places where the control is immediate. It is useless to investigate any other places.

This may be obvious. But it is worth mentioning because it seems often to be overlooked. There are quite a number of people who realise that there is a mind-body problem and admit that they are interested in it. Yet they seem to be impatient of any attempt to discuss the problem in terms of control mechanisms. On mention of the problem some of them immediately refer to religious or ethical questions. They seem to think it is relevant to ask how one can explain religious experience or account for what they call "higher things". Sometimes as I have pointed out already, their first question is how one can account for the works of Shakespeare or some other genius. They tend to suggest that a solution of the problem is to be found in an intensive study of Beauty and Goodness.

They are no less naive than those others for whom mention of the Problem of Interaction immediately arouses speculation, about thought transference, precognition, strange coincidences and other so-called occult phenomena. None of these appreciate what the problem is. They evidently do not realise that it is presented by the most trivial observations of our everyday lives just as much as by the work of a genius, by insignificant experiences as much as by sublime or unusual ones; they do not realise that this baffling interaction between a diathete and matter occurs when someone merely raises an a.rm in an idle gesture, takes a step forward, passes a casual remark, lights a cigarette.

No less naive, again, are those physiologists who seem to think that any recent and recondite discovery in their subject may be relevant to the problem. They tell us sometimes that the painstaking work on which they and their colleagues in the same field are engaged is leading slowly but surely to a solution. The work to which they refer may, perhaps, be the energy changes during a muscular contraction or the way in which secretions from the endocrine glands affect the action of nerves. It is all, they tell us, relevant. That such processes are remote from the places where interaction occurs and cannot possibly reveal anything about the mechanisms in which it does occur is ignored.

Do these physiologists really believe that one can hope to discover anything about the way primary relays work from a study of the way muscles, nerves or glands work? I doubt it. It is more likely, I think, that they have not become aware of the problem. Quite, quite confident that there are no such things as influences without location, no such process as interaction, no mechanisms to which the term primary relay could apply, they deny that there is any problem to solve. And they believe that discovery of more and more physiological mechanisms is slowly but surely proving them right.

So let me point out, even at the risk of some repetition, that, far from being disposed of by the existence of mechanisms, the problem is raised by their existence. It is to discover how diathesis originates; and the purpose served by mechanisms is for the transmission and conversion of diathesis. To speak of a mechanism is not to deny but to assert the reality of diathesis and, in asserting it, to raise the problem of how it is introduced into material systems.

6. THE FUNCTION OF TIMING

We have strayed a little from the concept controlled function. Let us return to it. This function varies greatly according to the nature of the controlled mechanism. One may control the angle through which a wheel or a micrometer screw is rotated; one may control the direction in which a line is drawn across a sheet of paper; in a manually operated telephone exchange control may consist in selection of the sockets into which plugs are inserted; in a muscular effort control consists in selection of the muscles in action together with control of the intensity with which each complete muscle contracts. Of what does the control consist in a primary diathesis?

In the absence of observation or experiment one has to fall back on the principle of minimum hypothesis. And this principle would hardly justify, I venture to suggest, the assumption that a primary diathesis consists in control of the angle through which something is rotated, or of the distance to which something travels, or of the intensity of something. It seems to me more fruitful to explore first the hypothesis that the controlled function in a primary diathesis is only timing and selection. Let me explain why.

Though for a whole muscle there is control of intensity of effort, there is none in the controlled function one stage nearer to the source of the diathesis. As I have mentioned already, variation in the intensity with which a muscle exerts a force depends, not on the intensity with which individual fibres contract, but on the number of fibres that do so. Each fibre works on the "all-or-nothing" principle. It either contracts to the full extent or remains in a state of relaxation. Hence a muscle is a device for converting control of the number of elements in action into control of intensity of effort. It does so by acting as a summating device.

A mechanism that acts on the "all-or-nothing" principle alternates between only two states. In this respect it is in the same category as a knife switch. And the controlled function in such a mechanism, is the simplest that one can think of. There is no gradation in it. Control of the choice between an "open" and a "closed" condition is simpler than control of the choice between an indefinitely large number of alternative angular positions, an indefinitely large number of distances, an indefinitely large number of different intensities. In the absence of any evidence to the contrary it is, therefore, natural to assume as a first hypothesis, that, like a muscle fibre, a primary relay works on the "all-or-nothing" principle, that it alternates between only two states. In the one it allows an impulse to pass to the muscle fibre, in the other it prevents the impulse from passing.

If this most simple of all possible assumptions is justified, a diathete determines only the moment in time when a change of state shall occur in any given primary relay. The controlled function in a primary diathesis consists of what might be aptly called pure timing.

The timing, however, demands considerable coordination. The number of muscle fibres that take part in even a slight activity is very great. The moment when any one of them contracts must be carefully co-ordinated with the moments when all the others do so. Were any of them to contract or relax out of their proper sequence the required movement of a limb would not occur.

Chaos is avoided and order ensured because the fibres perform a genuine drill, because of the correct timing of their operation. If there is a separate primary relay for each muscle fibre the timing in a primary diathesis does not consist in the timing of one operation only but in the coordinated timing of a great many. The diathete selects the relays as well as the moments when they operate.

Admittedly I have met the theory that a very complicated co-ordinating mechanism, constructed on a principle similar to that of an automatic telephone exchange, or an automatic gear change, is interposed between the primary relays and the muscle fibres. A specific "setting" of this mechanism ensures, according to the theory, that the fibres shall all contract and relax in the proper sequence, just as a specific setting of the automatic gear change in a motor-car ensures the correct sequence of operations. The setting would have to be varied from moment to moment so that it might be the correct one for every changing movement of the limbs.

This theory has been propounded by those who seem to believe naively that the assumption of sufficiently elaborate mechanisms in the brain can provide an answer to all questions about a primary diathesis. But actually the controlled function for such an elaborate mechanism would not be very simple; it would be very complicated indeed. The "automatic telephone exchange" theory certainly does not conform to the principle of minimum hypothesis.

7. THE PROBLEM REFORMULATED

Let me therefore make the provisional assumption that the basic diathesis, from which all others are only obtainable by conversion through suitably constructed mechanisms, is pure timing. And let me reformulate the Problem of Control on this assumption.

The part of a primary relay under the direct control of a diathete, is, of course, its controlled element. So our attention must be directed to this. This element, I am supposing, alternates between two states. When it is in the one state an impulse passes successively through every relay in cascade with the primary one; when it is in the other state the impulse cannot pass.

The difference between the two states of the controlled element is a physical difference. It can only be effected by the movement of physical objects and this movement can only occur if energy is transmitted to or from the element. And the requisite quantity of energy must, as I shall show in the next chapter, be appreciable.

The relay may be required to operate at any moment and so the energy needed for a change of state of the controlled element must always be available. But it is not always effective. For it to become so the diathete must do something; but what it does cannot be to transfer energy. One is obliged to picture the controlled element of a primary relay as a mechanism quite different from any with which we are familiar. Like every other mechanism it must receive a supply of energy so that it shall work at all and it must receive a supply of diathesis so that it shall work in the specified manner, the "specified manner" meaning in this case "at the specified moment". But unlike every other mechanism the diathesis is supplied without any expenditure of energy. The controlled element of a primary relay must be a mechanism in which an uncontrolled supply of energy is rendered effective at controlled moments of time. Fig. 4 on page 96 would serve for the controlled element of a primary relay if on the right hand top corner the words "operating energy" were omitted and the word "diathesis" occurred alone. Like the casting the controlled element of a primary relay is supplied with two commodities, energy and diathesis; and each has a separate source. But in the case of a primary relay the diathesis is pure; it is not accompanied by any energy at all. What sort of a mechanism can this be?

Thus can one formulate the Problem of Control in terms of a primary diathesis. The more one knows about energy and mechanical devices the more baffling does it appear.

For no mechanism that behaves as a primary relay must behave has ever been observed or even thought of. But that does not prove that such a mechanism is physically impossible. I have little doubt that more than one plausible theory could be found for the way a primary relay works and I shall venture to suggest one later. But I do not attach much importance to any theories, not even to my own, and anyhow this is not the time for theorising. It is the time for something more difficult, for the asking of relevant questions. It is the time for making an honest effort to appreciate the problem with all its difficulties and to realise how every one of the many theories that come so readily to the mind must be subjected to a rigid criticism. And this applies, let me add, not only to theories about non-material influences and the way they work, but also to such theories that there is no such thing as teleology, that it is in the nature of matter to plan for the future, that in some mystical way the "Gestalt" doctrine provides a solution, that it is unscientific to distinguish between controlled causes and uncontrolled causes, that the initiation of control is not a proper subject for scientific enquiry. The need for criticism exists not only for those theories that purport to explain the Problem of Interaction but also for those that purport to explain it away.

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