The Unity of Reason, Reconsidered: On the "Autonomy of Ideas" in the Later Kant

abstract: In the Groundwork and all three Critiques , Kant expresses the hope of unifying theoretical and practical reason in one system governed by a common principle—but does not clarify how he aims to achieve this unity. Here, I show that Kant refers to the "autonomy of ideas of reason" in his final decade, enabling a new approach to the unity of reason. This concept of autonomy, however, is not the moral autonomy of the self-legislating will, nor the spontaneity of theoretical reason. Instead, it corresponds to the autonomy ascribed to reflective judgment in representing both theoretical and practical ideas of reason in accordance with the principle of purposiveness, which I propose as the unifying principle Kant had been seeking.