"For anything that may be proved to the contrary, there may be a real something which is the cause of all our impressions; that sensations, though not likenesses, are symbols of that something; and that the part of that something, which we call the nervous system, is an apparatus for supplying us with a sort of algebra of fact, based on these symbols. A brain may be the machinery by which the material universe becomes conscious of itself. But it is important to notice that, even if this conception of the uuiverse and of the relation of consciousness to its other components should be true, we should, nevertheless, be still bound by the limits of thought, still unable to refute the arguments of pure idealism. The more completely the materialistic position is admitted, the easier it is to show that the idealistic position is unassailable, if the idealist confines himself within the limits of positive knowledge." However we attempt to form what philosophers call "ejects," to imagine that what is really in our consciousness is really the world outside ourselves, these ejects remain mere phenomena of our minds. Matter itself and its changes may, in the long run, be but modes of motion, but "our knowledge of motion is nothing but that of a change in the place and order of our sensations; just as our knowledge of matter is restricted to those feelings of which we assume it to be the cause." Huxley's exact position in regard to materialism is most plain in his expositions of the writings of Berkeley, with whom began in England the greatest movement towards an idealistic philosophy. "Berkeley faced the problem boldly. He said to the materialists: 'You tell me that all the phenomena of nature are resolvable into matter and its affections. I assent to your statement, and now I put to you the further question, What is matter? In answering this question you shall be bound by your own conditions; and I demand, in the terms of the Cartesian axiom, that you in turn give your assent only to such conclusions as are perfectly clear and obvious.'" Huxley then goes on to state the general lines of the arguments by which Berkeley arrived at the apparently paradoxical conclusion "that all the choir of heaven and furniture of the earth--in a word, all those bodies which compose the mighty frame of the world," have an existence only so far as they are in a perceiving mind. And he proceeds at length to explain the immense importance of the truths underlying Berkeley's position.