At the same time the victory of this tendency was always more apparent than real. In the first place, “out of the eater came forth meat”—that very advance of the special sciences, which in its earlier stages had tended to throw all speculative thought into the shade, in the long run caused the need of philosophy to be again felt. In particular, the study of development in the organic world, which had received so great a stimulus from the work of Darwin, could not be carried on without the aid of higher conceptions than were required for the guidance of the physicist. The hypothesis of natural selection might expel the idea of design in the cruder form of a special creation of every distinct species; and the emphasis which it had laid upon the outward conditions of growth might seem unfavorable to the higher conception of an immanent teleology of the organism, but it was confessed by its author to be an incomplete theory of development, and Darwin himself, when he turned his attention to the evolution of man, found it necessary to supplement it by what might be called the converse theory of sexual selection; thus adding a principle of co-operation to his first principle of competition. And Mr. Spencer, who defined growth as a process of integration and differentiation, little as he might himself intend it, was really putting into popular language the Hegelian idea of evolution—an idea which necessarily involved the conception of a self-determined end. Evolutionists might cling, as they still cling, to the belief that, though constantly and necessarily speaking of purpose, they could eliminate it from the result of their investigations by the hypothesis of Darwin, or, subsequently, of Weissmann; but their discussions, especially when they were extended to the historical development of man, could not but reawaken the great controversy whether in the _ultimate_ explanation of things it is more reasonable to “level up,” or to “level down,” to explain the higher by the lower, or the lower by the higher. That both explanations are necessary, nay, that no teleology can be of much worth which does not presuppose a thorough inquiry into the causal connections of particular phenomena, was admitted by all modern idealists. But they began to press the question whether the unity of the whole is not prior to its distribution into parts, and does not govern their relations with each other; and, in particular, whether it is possible in the case of organic beings, and especially of organic beings possessed of consciousness and self-consciousness, to be satisfied with a mode of explanation that treats them as mere collections of material elements which act and react externally upon each other. Whatever its value as a provisional hypothesis, can such a mode of explanation be finally regarded as adequate for the explanation of the nature of the world as a whole, or, indeed, of any one existence in it, that has even a