This book presents a new interpretation of Kant's theory of knowledge that emphasizes the coherence and plausibility of his doctrine of transcendental idealism. Many interpreters believe that Kant's transcendental idealism is an incoherent theory. Some have attempted to respond to this charge. Yet, as the author demonstrates, the interpretations that seek to vindicate Kant's theory continue to be committed to some claims that evoke the charge of incoherence. One type of claim which does so is connected to the contradictory notion of subjective necessity. The other type of claim is related to the supposition that knowledge of the reality of appearances entails knowledge of the reality of things in themselves. The interpretation presented in this book does not involve any of these claims. Part One of this book presents an analysis of Kant's concept of a priori knowledge and of his response to skepticism about synthetic a priori knowledge that specifies the content of such knowledge without invoking the notion of subjective necessity. Part Two presents an account of the non-spatiotemporality of things in themselves that does not entail knowledge of the reality of things in themselves. Part Three presents a new interpretation of transcendental synthesis, the transcendental "I" and of the role of transcendental self-consciousness in synthetic a priori knowledge which emphasizes the originality of Kant's account of self-knowledge and subjectivity. The arguments presented in this book relate Kant's ideas to current debates in epistemology, metaphysics and the philosophy of mind in a way that underscores their invaluable relevance to present-day philosophical discourse.