The period from Kant to Hegel is one of the most intense and rigorous in modern philosophy. The central problem at the heart of it was the development of a new standard of theoretical reflection and of the principle of rationality itself. The essays in this volume consider both the development of Kant's system of transcendental idealism in the three Critiques, the Metaphysical Foundations of Natural Science, and the Opus Postumum, as well as the reception and transformation of that idealism in the work of Fichte, Schelling, and Hegel.