Based on a series of published essays, this book presents a clear account of Kant's views about the capacities a thinking subject must have to be capable of thought. This aspect of Kant's philosophy has been largely ignored by twentieth-century writers. From Kant's analysis of the necessary capacities for thought, Kitcher derives a new interpretation of the structure for the deduction of categories in The Critique of Pure Reason. She defends Kant's belief in the necessity of concepts that occur across all our thinking. She goes on to illuminate the problem of thinking itself, elucidating the uniquely useful set of starting assumptions about what thinking really involves, which are to be found in Kant's work.