Things’ we may say ‘obey the laws of science…except when they don’t.’ Or, to be more precise, ‘the laws of science are less uniformly valid in one region than in another.’ Details are not necessary here; what is important is the general idea.
But is it necessary to doubt the scientific assumption? Are we obliged to reject the simple and convenient view of the universal validity of science for the undeniably more complicated and tiresome view suggested above? Imagine that, by accident, you rest your bare arm on a hot stove. You will undoubtedly lift your arm in a hurry. Why? Because contact with the hot stove is painful, you may say. But this won’t do at all. What we want is an account of the changes that took place in your nervous system from the time your arm was rested on the stove to the time it was raised; and this account must be in strictly scientific terms. Pain, however, is not a scientific term. We can speak of an electrical or chemical impulse travelling along a nerve up your arm to your brain; for these are all things that can be publicly observed (in theory at least) by each one of a team of physiologists who are experimenting on you. But the pain you feel is strictly private: not even in theory can the team of physiologists observe it.[c] (You can tell them that you feel pain, of course, but this does not make the pain public: what is public here is the sound of your voice, and the meaning of the words you utter is quite irrelevant—to allow that your words are meaningful is to beg the whole question.) A physiologist can observe an impulse moving up your arm, but he cannot observe a pain moving up your arm; only you can do that (if, for example, a red-hot needle is moved on your skin from the elbow to the shoulder; but not, of course, if your nerve is stimulated at a stationary point, when all you will feel is a stationary pain). This means (and I shall emphasize it by underlining it) that a physiologist must make no reference whatsoever to feeling (pleasure, pain, indifference) in his account of human behaviour. If he fails to abstain he abandons scientific method.
A physiologist is bound to maintain that the pain you felt when your arm was against the stove had nothing at all to do with the immediately subsequent removal of the arm from the stove (nor with your remarks about it); he must maintain this because he is obliged to claim, if he is to be consistent, that he can fully account for the movement of your arm (and the sound of your voice) in terms of neural mechanisms alone and without any reference to the pain. And if feeling plays no part in our actions we must count it a fortunate coincidence that the state of the nervous system to which the painful feeling of a burning arm corresponds happens to be one that brings about removal of the arm from the hot surface: if the converse were true, and the nervous system pressed the arm down still harder on the hot surface, we should have a pretty miserable time of it. Imagine it: each time we felt pain we should find the neural mechanism making the body do the very thing that aggravated the pain; and perhaps we should find ourselves recoiling from pleasure ‘as if we had been burned’. But no; our bodies, by some happy chance, do just what we should wish them to do—when there is pleasure the body acts in such a way as to prolong it, and when there is pain the body takes action to bring it to an end. Or can it possibly be that feeling does, after all, dictate—to some extent at least—what our bodies shall do? Were we perhaps wrong in so categorically rejecting your original explanation that you raised your arm because contact with the hot stove was painful?
Or consider the case of a man who takes alcohol. Are the motions of buying the bottle, opening it, pouring the contents into a glass, and finally swallowing, wholly to be accounted for without any reference to the fact that he finds it pleasant to be intoxicated? Certainly, there is good experimental evidence that our behaviour will accommodate itself, after a short period, to a change of environment in such a way as to give us the least possible discomfort in the altered circumstances.[d] This is the principle upon which the conditioning of reflexes depends—a rat is repeatedly made uncomfortable by an electric shock if he behaves in a certain way, and, in consequence, ‘learns’ to behave in a different way.
But if we are to allow, as clearly enough we must, that feeling is capable of affecting the state of the nervous system (either by determining a specific action, such as raising the arm off a hot stove, or by conditioning a fairly lasting change in behaviour), then we shall find ourselves obliged to abandon the postulate of the universal validity of the laws of science. So long as feeling depended upon the state of the nervous system and the state of the nervous system upon scientific determinism, all was well; but if, in addition, the state of the nervous system must be admitted to depend upon feeling, then (at least in the eyes of science) we enter the realms of chaos; for feeling, not being publicly observable, is not a scientific entity, and cannot therefore be governed by any laws of science, and the behaviour of the nervous system, accordingly, ceases to be wholly rational. In short, the living body, and the nervous system in particular, are regions where the laws of science are manifestly less uniformly valid than elsewhere.
