 Kant had already published a number of substantial scientific as well as philosophical works before the “great light” of transcendental idealism came to him in 1769, leading to his first statement of it the following year in his inaugural dissertation, On the Forms and Principles of the Sensible and Intelligible Worlds (1770). But it would then take him another decade, the so-called “silent decade”, to publish his full argument for transcendental idealism in the first edition of the Critique of Pure Reason, which appeared in 1781, and even then the relation between the empirical realism and transcendental idealism that he developed in that work continued to vex him: the first substantial review of the book in 1782 charged him with Berkeleianism, in other words, with idealism, and Kant then tried to rebut that accusation in his attempted popularization of the Critique, the Prolegomena to Any Future Metaphysics of 1783, and to further defend that rebuttal of ordinary idealism in the “Refutation of Idealism” that he added to the second edition of the Critique of Pure Reason in 1787. Even then he was not done with the subject, as we know from a dozen further drafts of the “Refutation” that he composed after that second edition of the Critique. Indeed, Kant continued to struggle with the clarification of his own position to the end of his life, attempting a restatement of transcendental idealism in the uncompleted material for a final book that has come down to us under the name of the Opus postumum. But since it was Kant’s presentations of his position in the two editions of the Critique and the Prolegomena that were most influential in his own time and have been since, we shall concentrate on those texts here. It was in these texts that Kant attempted to perfect his combination of empirical realism about space, time, and the categories, transcendental idealism with regard to space and time, and yet realism (agnosticism) about the actual existence of things distinct from our representations of them. It was then primarily in his writings in moral philosophy, above all the Critique of Practical Reason of 1788, that he developed what we have called his practical idealism about the real nature of the self and God. The second half of Kant’s third and final critique, namely, the Critique of Teleological Judgment in the Critique of the Power of Judgment, uses Kant’s complex position to justify the revival of a teleological approach to nature that would seem to have already been outmoded in Kant’s time, but that will lie beyond the purview of the present article (see Guyer 2005).