This language has, at least, the merit of being unambiguous, and leaves us in no uncertainty as to where the writer stands. It discloses, likewise, the animus which motivates his peculiar interest in transformistic theories. If evolution were incapable of being exploited in behalf of materialistic philosophy, Mr. Robinson, we may be sure, would soon lose interest in the theory, and would once more align himself with the company, which he has so inappropriately deserted, namely, “the routine minds” that regard evolution “as a merely curious fact of no great moment.” Be that as it may, his final appeal is to the “facts,” and it is to the facts, accordingly, that we shall go; but they will not be the irrelevant “facts” of anatomy, physiology, and palæontology. Sciences such as these confine their attention to the external manifestations of human life, and can tell us nothing of man’s inner consciousness. It does not, therefore, devolve upon them to pronounce final judgment upon the origin of _man_. For that which is the distinguishing characteristic of man is not his animal nature, that he shares in common with the brute, but his rational nature, which alone differentiates him from “a beast that wants discourse of reason.” We cannot settle the question as to whether or not man’s _mind_ is “of animal extraction” by comparing his _body_ with the bodies of irrational vertebrates. To institute the requisite comparison between the rational mentality of man and the purely sentient consciousness of irrational animals falls within the exclusive competence of psychology, which studies the internal manifestations of life as they are presented to the intuition of consciousness, rather than biology, which studies life according to such of its manifestations as are perceptible to the external senses. Hence it is within the domain of psychology alone, that man can be studied on his distinctively human, or rational, side, and it is to this science, accordingly, that we must turn in our search for facts that are germane to the problem of the origin of man and the genesis of the human mind. How little, indeed, does he know of human nature, whose knowledge of it is confined to man’s insignificant anatomy and biology, and who knows nothing of the triumphs of human genius in literature, art, science, architecture, music, and a thousand other fields! Psychology alone can evaluate these marvels, and no other science can be of like assistance in solving the problem of whether man is, or is not, unique among all his fellows of the animal kingdom. § 2. The Science of the Soul