To which of the two belongs the larger share of blame for this implacable hostility is easily determined. Materialism, in dealing with mental phenomena, begins by setting chronology at defiance; but between idealism and the phenomena of matter there is no such aboriginal incongruity. From principles common to every form of idealism a theory is deducible which, while frankly acknowledging the reality of matter, may, with perfect consistency, maintain that reality to be mental--although mental in the sense of being, not a perception by, but a metamorphosis of, mind. Of such a theory the outlines seem to me to have been sketched, and the foundations partly laid, by Descartes, and it cannot be otherwise than interesting to inquire in what manner and how far so consummate an artificer advanced in the work, and where and wherefore he suddenly stopped short in it. When Descartes, after convincing himself of the hollow pretentiousness of most human knowledge, proceeded to dig away the accumulated drift and sand of ages in quest of any clay or rock there might be below, the first indubitable verity he came to was thought, about whose reality there could, as already explained, be no possibility of doubt, inasmuch as any doubt concerning it, being itself thought, would be but an additional proof of it. On the bit of firm ground thus thoroughly tested, he proceeded to place a formula not less carefully verified, his famous 'Cogito, ergo sum'--'I think, therefore I am.' By many of his followers, however, this second verification of his is deemed to be by no means so satisfactory as it was by himself, Professor Huxley more especially taking vehement, though, as I make bold to add, somewhat gratuitous, exception to every single word of the most celebrated of Cartesian formulae. No doubt the premiss of the formula assumes the conclusion, but it likewise includes as well as assumes it. No doubt, since 'I think' is but another way of saying 'I am thinking,' to say that 'I think' is to assume that 'I am;' nay, the same thing is equally assumed by the mere introduction of the pronoun 'I.' But Descartes was fully warranted in taking for granted the truth of his conclusion. For by previously showing incontestably that thought and consciousness are real existences, he had completely proved the premiss wherein his conclusion is included. What though, as Professor Huxley suggests, 'thought' may possibly 'be self-existent,' 'or a given thought the result of its antecedent thought, or of some external power'? Be thought what else it may, it must needs be, also, either an affection or an operation; if not performed, it must be felt; there must needs be, therefore, something by which it is either performed or felt, and that something cannot possibly be other than a thinking and conscious thing. As surely as thought is, so surely must there be a thinker. This is, in substance, affirmed even by many who deny it in terms, and Hume, in