of cerebral activity." The Professor here defends a doctrine from which I rather think Hume would have turned away. With all his skepticism, Hume was fond of dwelling on mental rather than on material operations. Such sentences show that Huxley may be properly called a materialist. He denies, indeed, that he is a materialist. The fact is, that he is an agnostic, believing in neither mind nor matter as substances. But then he makes all agency material. "The roots of psychology lie in the physiology of the nervous system." He gives a physical basis to all mental action—inconsistently, I think, for I can not find that on his principles he is entitled to seek for any basis. Neither reason nor experience sanctions the doctrine that matter can produce mind; that molecules or masses of matter can think or feel, or discover the distinction between good and evil. At this point Huxley seems to separate from such men as Tyndall and Du Bois-Reymond, who tell us that to bridge the wide gulf that divides mind from matter is altogether beyond human capacity or conception.
5. At this point it will be necessary to refer—I can do so only briefly—to the question so important in philosophy, as to whether the mind discovers some objects and truths at once, and without a process—that is, by intuition. Hamilton, in his famous Note A, appended to his edition of Reid's "Collected Works," has shown that all thinkers, including even skeptics, have been obliged to assume something without proof, and to justify themselves in doing so. In my "Examination of Mr. J. S. Mill's Philosophy" I have shown that, in his "Examination of Hamilton's Philosophy," he has assumed between twenty and thirty such principles. With Locke I hold that the primary mark of these intuitions is self-evidence. We perceive things and truths by simply looking at them. Intuitions are not high a priori truths independent of things, but they are involved in the very nature of things, and we perceive this as we look at them. Thus we know, by simply looking at them, that things exist; that if two straight lines placed alongside proceed an inch without coming nearer each other, they will not approach nearer, though prolonged through all space; that two things plus two things make four. Truths thus self-evident to our minds become necessary; we can not be made to judge or decide that they are not true. Necessity is commonly put forward by metaphysicians such as Leibnitz and Kant as the test of such truths. I regard it as the secondary, the primary being self-evidence.
Hume and Huxley have discussed the question of Necessity especially as applied to causation. Hume accounts for it by custom and association of ideas: we are accustomed to see cause and effect together, and when we see the one we are constrained, whether we will or not, to think of and expect the other. But this is not the kind of necessity which metaphysicians appeal to. Necessity as a test of truth is a necessity of cognition, belief, or judgment, arising from our viewing the nature of the object, as, for example, when on contemplating
