This volume is the first-ever English translation of Kant's last major work, the so-called Opus postumum, a work Kant himself described as his "chef d'oeuvre" and as the keystone of his entire philosophical system. It occupied him for more than the last decade of his life. Professor Förster's introduction places the text in the context of Kant's earlier writings and provides a comprehensive account of the remarkable history of the manuscript from Kant's death to its eventual publication in the 1930s. Also included are extensive explanatory notes and a helpful glossary.