The ontological problem will necessarily always remain the unsolved, in the sense of the very incompletely solved problem of philosophy. But as long as human experience develops, and as long as philosophy bestows upon experience the earnest and candid efforts of reflecting minds, the solution of the ontological problem will be approached, but never fully reached. That Being of the World which Kant, in the negative and critical part of his work, left as an X, unknown and unknowable, the last century has filled with a new and far richer content than it ever had before. Especially has this century changed the conception of the Unity of the Universe in such manner that it can never return again to its ancient form. On the one hand, this Unity cannot be made comprehensible in terms of any one scientific or philosophical principle or law. Science and philosophy are both moving farther and farther away from the hope of comprehending the variety and infinite manifoldness of the Absolute in terms of any one side or aspect of man's complex experience. But, on the other hand, the confidence in this essential Unity is not diminished, but is the rather confirmed. As humanity itself develops, as the Selfhood of man grows in the experience of the world which is its own environment, and of the world within which it is its own true Self, humanity may reasonably hope to win an increased, and increasingly valid, cognition of the Being of the World as the Absolute Self. Closely connected, and in a way essentially identical with the ontological problem, is that of the origin, validity, and rational value of the ideas of humanity. May it not be said that the nineteenth century transfers to the twentieth an increased interest in and a heightened appreciation of the so-called practical problems of philosophy. Science and philosophy certainly ought to combine--and are they not ready to combine?--in the effort to secure a more nearly satisfactory understanding and solution of the problems afforded by the æsthetical, ethical, and religious sentiments and ideals of the race. To philosophy this combination means that it shall be more fruitful than ever before in promoting the uplift and betterment of mankind. The fulfillment of the practical mission of philosophy involves the application of its conceptions and principles to education, politics, morals, as a matter of law and of custom, and to religion as matter both of rational faith and of the conduct of life.