one of the most painful circumstances of recent advances in science is that each one of them makes us know less than we thought we did. when i was young we all knew, or thought we knew, that a man consists of a soul and a body; that the body is in time and space, but the soul is in time only. whether the soul survives death was a matter as to which opinions might differ, but that there is a soul was thought to be indubitable. as for the body, the plain man of course considered its existence self-evident, and so did the man of science, but the philosopher was apt to analyze it away after one fashion or another, reducing it usually to ideas in the mind of the man who had the body and anybody else who happened to notice him. the philosopher, however, was not taken seriously, and science remained comfortably materialistic, even in the hands of quite orthodox scientists.

nowadays these fine old simplicities are lost: physicists assure us that there is no such thing as matter, and psychologists assure us that there is no such thing as mind. this is an unprecedented occurrence. who ever heard of a cobbler saying that there was no such thing as boots, or a tailor maintaining that all men are really naked? yet that would have been no odder than what physicists and certain psychologists have been doing. to begin with the latter, some of them attempt to

reduce everything that seems to be mental activity to an activity of the body. there are, however, various difficulties in the way of reducing mental activity to physical activity. i do not think we can yet say with any assurance whether these difficulties are or are not insuperable. what we can say, on the basis of physics itself, is that what we have hitherto called our body is really an elaborate scientific construction not corresponding to any physical reality. the modem would-be materialist thus finds himself in a curious position, for, while he may with a certain degree of success reduce the activities of the mind to those of the body, he cannot explain away the fact that the body itself is merely a convenient concept invented by the mind. we find ourselves thus going round and round in a circle: mind is an emanation of body, and body is an invention of mind. evidently this cannot be quite right, and we have to look for something that is neither mind nor body, out of which both can spring.

let us begin with the body. the plain man thinks that material objects must certainly exist, since they are evident to the senses. whatever else may be doubted, it is certain that anything you can bump into must be real; this is the plain man's metaphysic. this is all very well, but the physicist comes along and shows that you never bump into anything: even when you run your head against a stone wall, you do not really touch it. when you think you touch a thing, there are certain electrons and protons, forming part of your body, which are attracted and repelled by certain electrons and protons in the thing you think you are touching, but there is no actual contact. the electrons and protons in your body, becoming agitated by nearness to the other electrons and protons, are disturbed, and transmit a disturbance along your nerves to the brain; the effect in the brain is what is necessary to your sensation of contact, and by suitable experiments this sensation can be made quite deceptive. the electrons and protons themselves, however, are only a crude first approximation, a way of collecting into a bundle either trains of waves or the statistical probabilities of serious different kinds of events. thus matter has become altogether too ghostly to be used as an adequate stick with which to beat the mind. matter in motion, which used to seem so unquestionable, turns out to be a concept quite inadequate for the needs of physics.

nevertheless modern science gives no indication whatever of the existence of the soul or mind as an entity; indeed the reasons for disbelieving in it are of very much the same kind as the reasons for disbelieving in matter. mind and matter were something like the lion and the unicorn fighting for the crown; the end of the battle is not the victory of one or the other, but the discovery that both are only heraldic inventions. the world consists of events, not of things that endure for a long time and have changing properties. events can be collected into groups by their causal relations. if the causal relations are of one sort the resulting group of events may be called a physical object, and if the causal relations are of another sort, the resulting group may be called a mind. any event that occurs inside a man's head will belong to groups of both kinds; considered as belonging to a group of one kind, it is a constituent of his brain, and considered as belonging to a group of the other kind, it is a constituent of his mind.