This book explores the main stages and key concepts in the development of Kant's critical philosophy, from the early 1760s to the 1790s. Karl Ameriks provides a detailed and concise account of the main ways in which the later critical works provide a plausible defense of the conception of humanity's fundamental end that Kant turned to after reading Rousseau in the 1760s. Separate essays are devoted to each of the three Critiques, as well as to earlier notes and lectures and several of Kant's later writings on history and religion. A final section devotes three chapters to post-Kantian developments in German Romanticism, accounts of tragedy up through Nietzsche, and contemporary philosophy. The theme of an elliptical path is shown to be relevant to these writers as well as to many aspects of Kant's own life and work. The topics of the book include fundamental issues in epistemology and metaphysics, with a new defense of the Amerik's 'moderate' interpretation of transcendental idealism.