It is not going too far to say that in common estimation psychology has as yet hardly reached what Kant has called the steady walk of science—_der sichere Gang der Wissenschaft_. To assert this is not, of course, to throw any doubts on the importance of the problems, or on the intrinsic value of the results, in the studies which have been prosecuted under that name. It is only to note the obvious fact that a number of inquiries of somewhat discrepant tone, method, and tendency have all at different times covered themselves under the common title of psychological, and that the work of orientation is as yet incomplete. Such a destiny seems inevitable, when a name is coined rather as the title of an unexplored territory, than fixed on to describe an accomplished fact. (i.) Psychology as a Science and as a Part of Philosophy. The _De Anima_ of Aristotle, gathering up into one the work of Plato and his predecessors, may be said to lay the foundation of psychology. But even in it, we can already see that there are two elements or aspects struggling for mastery: two elements not unrelated or independent, but hard to keep fairly and fully in unity. On one hand there is the conception of Soul as a part of Nature, as a grade of existence in the physical or natural universe,—in the universe of things which suffer growth and change, which are never entirely “without matter,” and are always attached to or present in body. From this point of view Aristotle urged that a sound and realistic psychology must, e.g. in its definition of a passion, give the prominent place to its physical (or material) expression, and not to its mental form or significance. It must remember, he said, that the phenomena or “accidents” are what really throw light on the nature or the “substance” of the Soul. On the other hand, there are two points to be considered. There is, first of all, the counterpoising remark that the conception of Soul as such, as a unity and common characteristic, will be determinative of the phenomena or “accidents,”—will settle, as it were, what we are to observe and look for, and how we are to describe our observations. And by the _conception_ of Soul, is meant not _a_ soul, as a thing or agent (subject) which has properties attaching to it; but soul, as the generic feature, the universal, which is set as a stamp on everything that claims to be psychical. In other words, Soul is one, not as a single thing contrasted with its attributes, activities, or exercises of force (such single thing will be shown by logic to be a metaphysical fiction); but as the unity of form and character, the comprehensive and identical feature, which is present in all its manifestations and exercises. But there is a second consideration. The question is asked by Aristotle whether it is completely and strictly accurate to put Soul under the category of natural objects. There is in it, or of it, perhaps, something, and something essential to