We have first the general fact that all our knowledge of motion, and so of matter, is merely a knowledge of the modifications of mind. That is to say, all our knowledge of the external world--including the knowledge of our own brains--is merely a knowledge of our own mental states. Let it be observed that we do not even require to go so far as the irrefutable position of Berkeley, that the existence of an external world without the medium of mind, or of being without knowing, is inconceivable. It is enough to take our stand on a lower level of abstraction, and to say that whether or not an external world can exist apart from mind in any absolute or inconceivable sense, at any rate it cannot do so _for us_. We cannot think any of the facts of external nature without presupposing the existence of a mind which thinks them; and therefore, so far at least as we are concerned, mind is necessarily prior to everything else. It is for us the only mode of existence which is real in its own right; and to it, as to a standard, all other modes of existence which may be _in_ferred must be _re_ferred. Therefore, if we say that mind is a function of motion, we are only saying, in somewhat confused terminology, that mind is a function of itself. Such, then, I take to be a general refutation of materialism. To use but a mild epithet, we must conclude that the theory is unphilosophical, seeing that it assumes one thing to be produced by another thing, in spite of an obvious demonstration that the alleged effect is necessarily prior to its cause. Such, I say, is a general refutation of materialism. But this is far from being all. 'Motion,' says Hobbes, 'produceth nothing but motion;' and yet he immediately proceeds to assume that in the case of the brain it produces, not only motion, but mind. He was perfectly right in saying that with respect to its movements the animal body resembles an engine or a watch; and if he had been acquainted with the products of higher evolution in watch-making, he might with full propriety have argued, for instance, that in the compensating balance, whereby a watch adjusts its own movements in adaptation to external changes of temperature, a watch is exhibiting the mechanical aspect of volition. And, similarly, it is perhaps possible to conceive that the principles of mechanism might be more and more extended in their effects, until, in so marvellously perfected a structure as the human brain, all the voluntary movements of the body might be originated in the same mechanical manner as are the compensating movements of a watch; for this, indeed, as we have seen, is no more than happens in the case of all the nerve-centres other than the cerebral hemispheres. If this were so, motion would be producing nothing but motion, and upon the subject of brain-action there would be nothing further to say. Without consciousness I should be delivering this lecture; without consciousness you would be hearing it; and all the busy