Of course, the movement received a great impetus from the Reformation, whose proud boast was the overthrow of all authority in matters of religious belief, and the enthronement in its stead of the supremacy of individual thought. The systems of Descartes' successors differed not so much in kind as in degree. Immanuel Kant is probably the greatest thinker of modern philosophy. He is certainly the one of whom it is proudest; and yet his greatest contribution to philosophical thought is nothing but a grand act of despair in the capabilities of the human intellect, amounting in fact to a denial of the objective validity of knowledge. Though setting out, like many another reformer, with the best of intentions, it was the author of the Critique of Pure Reason who put the finishing touches to Cartesian doubt and Cartesian rationalism. Modern thought in its origin and development is thus sceptical and agnostic, and Immanuel Kant is its prophet; for he was the one great thinker that has left the deepest impress upon the writers that followed him. He was, in the words of Sabatier, the master mind that makes leaders of lesser calibre proud to boast of the fact that they have received their philosophic initiation and baptism from his Critique. When we speak then of modern thought, we mean systems of philosophy that are preponderantly rationalistic, and, when there is question of the supernatural, altogether agnostic. This is to say that modern thought is dominated and impregnated, colored and tainted, by the philosophy of Kant. Even the philosophical principles underlying the religious sentimentality of Schleiermacher presuppose the Critique of Practical Reason of the professor of Königsberg.