This conclusion, however, he repeats, is but an empirical formula and has provisional value only. One substance, he says, acts in both consciousness and the bodily organism, but what kind of a substance is this, and why does it have this twofold form of manifestation? These are questions, he replies, beyond the reach of our knowledge. We can simply make a statement which seems to be required by the facts, namely, that the same thing which lives, grows, and takes on form in the outward world, apprehends itself inwardly as thinking, feeling, and willing. No opinion is thereby ventured as to whether mind or matter is the more original form of existence. By no means is metaphysical speculation upon this question excluded. The hypothesis of identity (for so Professor Höffding terms it) is consistent with philosophical idealism and also with the view that the innermost nature of being is not identical with consciousness. He simply claims for it that it is the most natural conclusion with regard to the relation between two empirical sciences, physiology and psychology. These sciences, according to the hypothesis, treat of the same material viewed from two different sides, and there can be no more conflict between them than between one person who looks on the convex side of a circle and another who looks on the concave side (to borrow an illustration used by Fechner). On another occasion I may give my own views, and content myself now with saying that I have followed with the greatest interest and with much (if not unlimited) satisfaction the treatment of the subject at the hands of the genial, large-minded Danish professor. W. M. SALTER. LITERARY CORRESPONDENCE. FRANCE. The work of M. FOUILLÉE which I announced in my last communication (to your other magazine), bears the title of _L'Evolutionnisme des Idées-Forces_. It is a voluminous work; and it contains a great many things—perhaps too many. We have from M. Fouillée, the promise of a constructive work—_La Psychologie des Idées-Forces_, in two volumes; but his present book is chiefly devoted to the labor of demolition. As contemporaneous psychology has its weak sides, and as M. Fouillée is a skilful critic, you may imagine that his attacks upon Wundt, Herbert Spencer, Taine, Ribot, W. James, and numbers of others, both living and dead, are conducted with spirit. The successful fulfilment of the task he has set himself would necessitate the ruin of the hypothesis, avowed or concealed, that has supported psychological research as well as furnished occasional excellent conclusions; for it is the aim of M. Fouillée to overthrow what he has ingeniously termed the theory of "idea-reflexes," and the place once cleared, to substitute for it the theory of "idea-forces."