For whether, indeed, thought is regarded as a mere function of the brain and the state of consciousness as an epiphenomenon of the state of the brain, or whether mental states and brain states are held to be two versions, in two different languages, of one and the same original, in either case it is laid down that, could we penetrate into the inside of a brain at work and behold the dance of the atoms which make up the cortex, and if, on the other hand, we possessed the key to psycho-physiology, we should know every detail of what is going on in the corresponding consciousness.
This, indeed, is what is most commonly maintained by philosophers as well as by men of science. Yet it would be well to ask whether the facts, when examined without any preconceived idea, really suggest an hypothesis of this kind. That there is a close connexion between a state of consciousness and the brain we do not dispute. But there is also a close connexion between a coat and the nail on which it hangs, for, if the nail is pulled out, the coat falls to the ground. Shall we say, then, that the shape of the nail gives us the shape of the coat, or in any way corresponds to it? No more are we entitled to conclude, because the physical fact is hung on to a cerebral state, that there is any parallelism between the two series psychical and physiological. When philosophy pleads that the theory of parallelism is borne out by the results of positive science, it enters upon an unmistakably vicious circle; for, if science inter-
