1. A PROBLEM IN MECHANICS

THE search for questions relevant to the dispute between monists and dualists has taken us further and further from the universe of discourse in which the philosopher dwells and further and further into the universe of discourse in which the scientist is at home. From consideration of purpose in general we came to consideration of the machinery with the help of which human purposes are sometimes achieved. And from consideration of one example of such machinery, namely a crane in a foundry, we came to consideration of specific mechanisms in the human brain. I have called them primary relays. Questions that are relevant, very relevant, to the dispute turn out to be:
How does a primary relay work? How is a primary relay controlled?

This is hardly what one would have expected. By tradition the central question in the dispute is: "What is mind?" And no less assiduously discussed than this one is the further question: "What is the true nature of the world around us? Is it as revealed to us by our senses or is it the quite different world as described by the physicist?" This is the Problem of Perception to which I have already referred at the beginning of Chapter X. Subsidiary to it are further questions such as: "What is the nature of a percept? What is the nature of thought? What is reason? What is instinct?" These are among the questions that I might have been expected to raise here. Instead, I have either ignored them or dismissed them lightly.

All these questions, like most others that are important in philosophy, are concerned with the essential nature of things. They are not concerned with activities. They begin with the words "what is"; the verb "to be" figures most prominently in their formulation, while the verb "to do" occurs only rarely. It is in this that scientifically important questions can be distinguished from philosophical ones. For a scientist makes much more use of the verb to do. "What does this mechanism do?" he is likely to ask. "What is being done to this system to make it undergo the change that is being observed?" "What", it was asked in an earlier chapter, "is done to the casting to make it pursue its specified course from one end of the foundry to the other?" Similarly: "What does a relay do? What does a muscle do? What does acetylcholine do?" And now the question has been reached: "What is done to a primary relay so as to ensure that it shall operate only at specified moments of time?"

Such a question does not belong to metaphysics or to any other branch of philosophy. It belongs to a discipline in which observation and experiment figure prominently, namely to science. And of all the branches of science it belongs to the one that the philosopher may well regard as the most mundane; for a question about the way a given mechanism works is fundamentally a question in mechanics.

That is why philosophers cannot fail to find my questions about primary relays too narrow for so cosmic a theme as the dispute between monists and dualists. At the same time theologians may find it too profane, educated laymen too barren. But it has to be remembered that the traditional questions about the essential nature of things, together with large sweeping questions about the world of percepts, about the whole material universe, about Goodness, Truth and Beauty, about Determinism and Free Will, about the difference between mind and matter, that such questions have received intensive discussion for many centuries and have still left philosophers arguing as fiercely as ever they did about every one of the great problems that they set out to solve. In dragging my theme from the exalted plane on which the philosopher does his thinking to the trivial one on which mechanics is studied I am making it accessible to those trained to think in terms of concrete realities. Where the broad generalisations and transcendental abstractions of philosophical method have so signally failed it is at least worth while to provide the opportunity for the application of scientific method.

2. A UNIVERSAL PROBLEM

Let it be noted, moreover, that questions about primary relays are less narrow than might at first sight be supposed. For primary relays are the most universal, the most indispensable of all mechanisms. It is only occasionally that levers, switches, push-buttons, taps, triggers, motors, cranes, and other engineering devices are used as instruments of the human will. But primary relays are essential instruments whenever a purpose is being served.

It is obviously so when the purpose is conscious and human. I have pointed out on page 91 in Chapter X that every one of the innumerable paths for diathesis on which our civilisation depends has its origin in a human brain. Some of these paths end at human hands; they are entirely within the substance of the human body. Others extend into man-made mechanisms. But at the beginning of every one of them there is a primary relay. If these devices occurred only in the brains of man and the higher animals they would be quite universal enough to merit study. And there are strong reasons for the view that primary relays are even more universal.

Some of these reasons follow from what I have said in Science versus Materialism and I hope to bring more supporting evidence in a later book. At the moment I shall be content to express the view that systems of cascaded relays characterise the structure of all living substance. For any such system there is a first, a primary, relay. And the questions always arise for this: "How does it work? How is it controlled?" The answers to these questions hold, I firmly believe, the key to what is distinctive in the structure and behaviour of all living substance.

However, I have no need to justify that belief just now. For it is not relevant to the present enquiry. The fact that a system of cascaded relays occurs anywhere at all is sufficient to raise the baffling Problem of Control. If the brain is the only place where such a system has its origin the problem is of somewhat limited significance. If such systems occur throughout the organic world the significance is wider. But the problem is equally real no matter how wide its significance.

It is necessary to point this out if only because of a current misapprehension. Some philosophers deprecate the suggestion that anything observable among plants and the lower animals should be interpreted in the teleological sense in which we do interpret the organisation of, say, a foundry. They do not do so because, like the religious fundamentalists, they want to assign to man a unique place in the world. They do so in the confused belief that they may thereby avoid those philosophical and scientific implications of teleology to which I have referred in Chapter VIII. So be it made clear that the Problem of Control cannot be explained away by saying that teleology occurs in human affairs only, or that, unlike man, the lower animals are guided by instinct and not by reason. One cannot eliminate purpose from the world of reality by insisting that there is only a little of it or that that little is only to be found in mundane places such as foundries.

3. THE CONTROLLED ELEMENT OF A PRIMARY RELAY

Nor can a problem that is presented by hard facts be disposed of by abstract speculation. And this brings me back to the hard fact of the series of mechanical devices between the craneman's brain and the casting that I have called a set of cascaded relays. The unit in the set that must now claim our attention is the first one and the part of this primary relay that calls for particular study is its controlled element.

I have explained in Chapter XI. what I mean by the term "controlled element" and I have shown there that even when one knows nothing about its construction, one can at least say that it alternates between two specific states. In the one state it allows energy to pass to the operating element of the same relay and in the other it prevents energy from passing. Once energy has passed to the operating element of the primary relay all the other relays cascaded with it come into action. So the moment when a change of state of the controlled element of a primary relay occurs determines the performance of all the other relays and, in our example, that of the casting.

Whatever may be the difference between the two states of the controlled element it is a physical difference and, therefore, characterised by a difference in the configuration of movable objects, of material particles of some sort. Such a difference can only be brought about when physical forces act on the movable objects. And to be effective the forces must act over a finite distance: their application represents the transfer of energy from or to the objects. One of the causes of a change of state in the controlled element is, therefore, as for every physical change, an exchange of energy with the environment. This is what philosophers call the vis a tergo, as I have explained in Chapter VIII. But it is only one of the causes. The other is that the element receives a supply of diathesis in the form of control of the moment when the change occurs.

In this respect the controlled element is no different from the casting in our foundry, the movement of which we sought to understand in earlier chapters. One of the causes for its movement was found to be a vis a tergo in the form of the energy that was being supplied through cables from the local power station. This explained why the casting moved at all. But to explain why it moved as it did, why it moved so as to meet the written instructions that the foreman had received and not at random, a second cause had to be found. This was that diathesis was also being supplied, that, in other words, the energy was controlled. Without the supply of diathesis the movement would have been a random and not a specified one.

Neither for the casting nor for the controlled element of the primary relay is there any difficulty in accounting for the energy. The power station can supply all that is needed to the one and surrounding tissues in the brain to the other. And in the foundry there is no difficulty in accounting for the supply of diathesis. So long as the craneman is skilful and intelligent an ample quantity is available.

Most of the path along which the diathesis arrives is, moreover, clearly visible. The foundry engineers know how the part of this works that lies beyond the craneman's hands. And a physiologist could tell us how some parts of the path work that are hidden in the body of the craneman. If every one of the mechanisms along this path except the first be called a secondary relay one can say that the energy to the controlled element of every secondary relay is controlled by the relay next to it on the side nearest to the source of the diathesis. In other words, there is always a mechanism, for the control of the energy to a secondary relay just as there is a mechanism for the control of the energy to the casting itself. But a primary relay is different. There is no mechanism for the control of the energy that operates its controlled element. If there were the term "primary relay" would be a misnomer. Unlike every other kind of relay, unlike every controlled and controlling device with which we are familiar, the controlled element of a primary relay receives a random supply of energy.

And yet it operates at controlled moments of time.

Therein lies the challenge to science. Can one prove that the energy does not arrive at random but just at the requisite moments? I fail to see how. Can one prove, alternatively, that the element does not operate at controlled moments of time? Again I fail to see how. So it remains to show why it is possible for a random supply of energy to result in a specified performance. That task does not fall within the province of philosophy; it belongs to science.

4- THE OPERATING ENERGY MUST BE SUPPLIED AS KINETIC ENERGY

There is no mechanism to ensure that the energy shall be available at the moments when it is required. From which the only possible conclusion is that it is available continuously. If the supply were intermittent and random the relay might not receive the operating energy at the required moments of time. Hence I can see no means of avoiding the assumption that we have here a system in which a continuous supply of energy results in an intermittent effect.

This would create no difficulty if one could assume that the energy was supplied in the form of potential energy. The energy in a coiled spring, a detonator, a cylinder containing gas under pressure, is continuously available. But to make use of it one has to have some release mechanism a trigger, a striker, a valve, for instance. And such a release mechanism would be a relay in front of the primary relay; it is precluded by the definition of a primary relay.

Hence it has to be assumed that the energy employed in changing the state of the controlled element of a primary relay is the energy contained in moving particles, that it is kinetic energy, expressible as 1/2 mV²

I do not make this suggestion as a contribution towards a theory of how a primary relay works. I make it as a contribution towards an understanding of the nature and difficulty of the problem. So long as one can assume vaguely that a store of potential energy is, in some undefined way, converted into the kinetic energy of moving particles just at the requisite moments of time one may feel quite happy that the problem will soon find an easy solution. But when one considers what happens in mechanical terms and appreciates that such conversion can only occur with the help of a converting or "trigger" mechanism one sees the problem in more concrete, and more baffling terms. One can then word it as follows:
Is a system possible in which a continuous and random movement of particles causes a specific effect intermittently and only at specified moments of time?

5. THE ENERGY REQUIRED CANNOT BE INDEFINITELY SMALL

In Chapter XI I spoke of the principle of tapering energy requirement. I do not know whether anyone will hope that this principle may point to a solution. Could it be applied without limit one might assume that no more than a single quantum of energy was required to change the state of the controlled element of a primary relay. It is true that the number of cascaded relays would not even have to be very large so as to give an amplification of energy from one quantum up to an amount sufficient for the movement of the casting.

Even if, however, one could base a satisfactory theory on the assumption that the energy requirement of the controlled element of a primary relay was very, very small, I do not believe that it would help. For it is difficult to assume that the energy requirement is very small.

To say that the energy requirement was very small would be to say that the device was very sensitive. And I doubt whether it can be. Every engineer knows that a properly designed mechanism must be neither too insensitive nor too sensitive. If it is too insensitive it does not operate when it is required to; for then the available energy is not sufficient to cause operation. And if it is too sensitive it operates when it is not required to; for then all sorts of stray forces cause operation.

The controlled element of a primary relay must, therefore, be only sensitive enough to be operated with certainty by such energy as the tissues of the brain are able to provide. For this the degree of sensitivity need not be great. As I have already said, the tissues contain an ample store of energy. At the same time the element must be insensitive enough to be proof against any stray forces that may cause unwanted action. Now the brain is a region of considerable activity. It is more reasonable to assume that the stray forces are substantial than that they are negligible. And such an assumption leads to the further conclusion that the controlled element of a primary relay is a robust, rather than a very sensitive, piece of mechanism.

Here again I do not make the suggestion as a contribution towards a theory of how a primary relay works, but, as before, as a contribution towards an understanding of the nature and the difficulty of the problem.

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