Professor Höffding does not indeed oppose himself to metaphysical speculation; he believes that the human mind will never consent to being shut out from the task of searching after the ultimate principles of the universe, of which it is a part. But his standpoint in this work is the purely empirical one, as one's standpoint must be in every positive science. Positive science deals with the facts of experience; metaphysics with their ultimate explanation. He regards it as a misfortune to confuse the two, as popular thinking in psychology does; and scientific thinking in this realm is characterised by the effort to avoid the confusion and keep solely to the facts of observation and experience. Accordingly both materialism and spiritualism are excluded from the field—each theory involving a transcending of the realm of experience, i. e., being metaphysical. There are two subdivisions of the realm of experience according to Professor Höffding,—one coextensive with psychical phenomena, such as feelings, thoughts, and volitions, the other with physical phenomena, i. e., with what moves in space. They may be called respectively inner experience and outer experience. Each must be grasped in its distinct features; and only after doing so can we feel the _problem_ involved in the question of their relation to or connection with one another. For it happens that one set of outer experiences stands in an indisputably peculiar relation to the phenomena of consciousness, namely, the set which we describe by the term "body" and, more particularly, by that of "nervous system" or "brain." Much of what we call the physical world stands in relation to consciousness as the thing known to the knower; but a part of the physical world (i. e., the body or brain) seems a part of the knower as well—a body or nervous system of some kind seems an indispensable requirement or at least concomitant of anything like feeling, or thought, or act of volition.