 The 1877 essay gives a genetic account of the development of Kant’s views about the thing-in-itself from the Inaugural Dissertation (1770) to the second edition of the Critique of Pure Reason (1787). This genetic reconstruction is supposed to reveal the underlying philosophical problems and motivations that drove Kant’s thinking, as well as the inner tensions that, according to Windelband, permeate critical philosophy. In particular, Windelband identifies a “gulf” (1877: 225) between Kant’s critique of knowledge and the metaphysics of morals, as well as a tension between the psychological account of the faculties, and Kant’s mature anti-psychologism. He distinguishes between four phases in Kant’s thinking about the thing-in-itself, and argues that residues of the latter three stages are present in both editions of the Critique (1781; 1787) and in the Prolegomena (1783).