stricter meaning of the word. The history of the development of the scientific spirit and of the achievements of the particular sciences is not the theme of this paper. To trace in detail, or even in its large outlines, the reciprocal influence of science and philosophy during the past hundred years, would itself require far more than the space allotted to me. It must suffice to say that the various advances in the efforts of the particular sciences to enlarge and to define the conceptions and principles employed to portray the Being of the World in its totality, have somewhat steadily grown more and more completely metaphysical, and more and more of positive importance for the reconstruction of systematic philosophy. The latter has not simply been disciplined by science, compelled to improve its method, and to examine all its previous claims. But philosophy has also been greatly enriched by science with respect to its material awaiting synthesis, and it has been not a little profited by the unsuccessful attempts of the current scientific theories to give themselves a truly satisfactory account of that Ultimate Reality which, to understand the better, is no unworthy aim of their combined efforts. During the nineteenth century science has seen many important additions to that Ideal of Nature and her processes, to form which in a unitary and harmonizing but comprehensive way is the philosophical goal of science. The gross mechanical conception of nature which prevailed in the earlier part of the eighteenth century has long since been abandoned, as quite inadequate to our experience with her facts, forces, and laws. The kinetic view, which began with Huygens, Euler, and Ampère, and which was so amplified by Lord Kelvin and Clerk-Maxwell in England, and by Helmholtz and others in Germany, on account of its success in explaining the phenomena of light, of gases, etc., very naturally led to the attempt to develop a kinetic theory, a doctrine of energetics, which should explain all phenomena. But the conception of "that which moves," the experience of important and persistent qualitative _differentiae_, and the need of assuming ends and purposes served by the movement, are troublesome obstacles in the way of giving such a completeness to this theory of the Being of the World. Yet again the amazing success which the theory of evolution has shown in explaining the phenomena with which the various biological sciences concern themselves, has lent favor during the latter half of the century to the vitalistic and genetic view of nature. For all our most elaborate and advanced kinetic theories seem utterly to fail us as explanatory when we, through the higher powers of the microscope, stand wondering and face to face with the evolution of a single living cell. But from such a view of the essential Being of the World as evolution suggests to the psycho-physical theory of nature is not an impassable gulf. And thus, under its growing wealth of knowledge,