and ideas, the position of the Inquiry seems to be the same as that of the Treatise. The question, however, cannot be decisively determined, because of differences of statement in the two works, or rather because of lack of statement in the later, and also because of some—at least apparent—inconsistencies in both. Thus, with regard to the cause of perceptions, some interpreters hold that there is here a real contradiction in Hume's treatment. Professor Huxley,[1] for example, states that Hume "fully adopted the conclusion to which all that we know of psychological physiology tends, that the origin of the elements of consciousness, no less than that of all its other states, is to be sought in bodily changes, the seat of which can only be placed in the brain." And at the same time he asserts that "Hume is not quite consistent with himself,"[2] respecting the origin of impressions of sensation, for "in one place he says that it is impossible to decide 'whether they arise immediately from the object, or are produced by the creative power of the mind, or are derived from the Author of our being.'" Now this inconsistency is removed on the assumption that in one instance Hume is speaking of the immediate cause, and in the other of the ultimate cause. That he makes such a distinction in the Treatise is quite evident,[3] and that he implies such a distinction in the Inquiry is at least probable.[4]
3. Association of Ideas and result—Complex Ideas. On the question of the laws of association of ideas, the position of both works is almost identical. The result is the same,[5] but the treatment is somewhat different. The attempted partial explanation given in the Treatise[6] of these principles, does not appear in the Inquiry. Concerning the results of the laws of association, that is, complex ideas—philosophical relations, substances, and modes including abstract ideas—the discussion is wholly omitted in the later work. Philosophical relations, however, seem to be assumed.[7] I shall refer to substance later;
