The second of the greater problems which the critical philosophy of the eighteenth handed on to the nineteenth century is the ontological problem. This problem, even far more than the epistemological, has excited the intensest interest, and called for the profoundest thought, of reflective minds during the last hundred years. This problem engages in the inquiry as to what Reality is; for to define philosophy from the ontological point of view renders it "the rational science of reality;" or, at least, "the science of the supreme and most important realities." In spite of the fact that the period immediately following the conclusion of the Kantian criticism was the age when the people were singing "_Da die Metaphysik vor Kurzem unbeerbt abging,_ _Werden die Dinge an sich jetzo sub hasta verkauft,_" the cultivation of the ontological problem, and the growth of systematic metaphysics in the nineteenth century, had never previously been surpassed. In spite of, or rather because of, the fact that Kant left the ancient body of metaphysics so dismembered and discredited, and his own ontological structure, in such hopeless confusion, all the several buildings both of Idealism and of Realism either rose quickly or were erected upon the foundations made bare by the critical philosophy. But especially unsatisfactory to the thought of the first quarter of the nineteenth century was the Kantian position with reference to the problem in which, after all, both the few who cultivate philosophy and the multitude who share in its fruits are always most truly interested; and this is the ethico-religious problem. In the judgment of the generation which followed him, Kant had achieved for those who accepted his points of view, his method of philosophizing, and his results, much greater success in "removing knowledge" than in "finding room for faith." For he seemed to have left the positive truths of Ethics so involved in the negative positions of his critique of knowledge as greatly to endanger them; and to have entangled the conceptions of religion with those of morality in a manner to throw doubt upon them both.