Æsthetic. It was upon the intuitional basis of mathematical judgments that Kant based his reasonings as to the intuitive, a priori nature of space and time. There is no evidence that I know of that Kant began the investigations which led to his final doctrine, before the period at which Lambert's letter was written. His mathematical studies, it is true, had shown him the erroneous use in philosophy of the mathematical method. But in his essay, The Attempt to Introduce Negative Quantities into Philosophy, the discussion is of logical, not sensuous problems. Kant had learned at this time that synthesis of ontologic validity was impossible for thought; he had not learned that it was likewise impossible for sense. Furthermore, in his reply to Lambert's letter sent him four years before, Kant discusses the problem of mathematical cognitions referred to by Lambert, and even states, to quote his own words,[1] " I could resolve upon nothing else than to communicate to you a clear outline of the way in which this science appeared to me, and also a definite conception of its peculiar method. In carrying out this intention I was led to investigations that were entirely new to me. . . . But a year ago did I arrive at this conception."[2] Does this not at least make probable that it was Lambert's views that formed the starting-point of the Kantian conception of the transcendental ideality of time and space as the only possible solution of the problem of mathematical judgments? Besides, the step was short from a formal a priori concept to a form of sensibility, since Kant's reading of Hume had shown him the importance of sensation. Lambert, having read only Locke, whose sensationalistic epistemology is incomplete, failed to draw this distinction. In his final letter to Kant, however, he agrees with him in paying this tribute to sensation. Again, once having given that time and space were a priori forms of sensibility, the natural supposition was that they were nothing more, at least from the standpoint of Kant, who had rejected the Leibnizian identification of thought and reality. But aside from these reasons, it is certain that from about the time when Kant received Lambert's letter until 1770 he was at work upon
