The extremity to which philosophy had been brought by empiricism on the one hand and formalism on the other was Kant's opportunity. Leibnitz's principle of the "nisi intellectus ipse" was expanded by him into a demonstration the completest yet effected by philosophy of the part played by the subject not merely in the manipulation of the material of experience but in the actual constitution of the object that is known. On the other hand he insisted on the synthetic character of this activity without which it was impossible to get beyond the circle of our own thoughts. The parts of the _Critique of Pure Reason_, more particularly the "Deduction of the Categories" in which this theory is worked out, may be said to have laid the foundation of modern idealism--"articulum stantis aut cadentis doctrinae." In spite of the defects of Kant's statement--to which it is necessary to return--the place of the concepts and ideals of the mind and the synthetic organizing activity which these involve was established with a trenchancy which has been acknowledged by all schools alike. The "Copernican revolution" which he claimed to have effected may be said to have become the starting-point of all modern philosophy. Yet the divergent uses that have been made of it witness to the ambiguity of his statement which is traceable to the fact that Kant was himself too deeply rooted in the thought of his predecessors and carried with him too much of their spirit to be able entirely to free himself from their assumptions and abstractions. His philosophy was more like Michaelangelo's famous sculpture of the Dawn, a spirit yet encumbered with the stubble of the material from which it was hewn, than a clear cut figure with unmistakable outlines. Chief among these encumbering presuppositions was that of a fundamental distinction between perception and conception and consequent upon it between the synthetic and the analytic use of thought. It is upon this in the last resort that the distinction between the phenomenal world of our experience and a noumenal world beyond it is founded. Kant perceives that "perception without conception is blind, conception without perception is empty," but if he goes so far ought he not to have gone still further and inquired whether there can be any perception at all without a concept, any concept which does not presuppose a precept, and, if this is impossible, whether the distinction between a world of appearance which is known and a world of things-in-themselves which is not, is not illusory? Hegel.