Kant treats similarly the problem of the relations of physical and final causes, of necessity and freedom. Here, as in the case just mentioned, his main problem is to discover their _harmony_. His solution, again, is in the union, in our intelligence, of the understanding--as the source of the notions which "make nature"--with the ideas of that reason which gives a "categorical imperative." The cause of the possibility of this harmony between nature and freedom, between the sense world and the rational, he finds in a being, God, whose sole function in the Kantian philosophy may be said to be to "pre-establish" it. I cannot believe that Kant, in postulating the problems of philosophy as the harmony of sense and understanding, of nature and freedom, and in finding this harmony where he did, was not profoundly influenced, consciously as well as unconsciously, by Leibniz. In fact, I do not think that we can understand the nature either of Kant's immense contributions to modern thought or of his inconsistencies, until we have traced them to their source in the Leibnizian philosophy,--admitting, on the other hand, that we cannot understand why Kant should have found necessary a new way of approach to the results of Leibniz, until we recognize to the full his indebtedness to Hume. It was, indeed, Hume that awoke him to his endeavors, but it was Leibniz who set before him the goal of these endeavors. That the goal should appear somewhat transformed, when approached from a new point of view, was to be expected. But alas! the challenge from Hume did not wholly awaken Kant. He still accepted without question the validity of the scholastic method,--the analytic principle of identity as the type of perfect knowledge,--although denying its sufficiency for human intelligence. Leibniz suggested, and suggested richly, the synthetic, the negative aspect of thought; Kant worked it out as a necessary law of _our_ knowledge; it was left to his successors to work it out as a factor in the law of _all_ knowledge.