Kant describes the concept of freedom as "the keystone of the whole structure of a system of pure reason, even of speculative reason." Kant's theory of freedom thus plays a foundational and unifying role in all aspects of his philosophy and is thus of significant interest to historians of Kant's philosophy. Kant's theory of freedom has also played a significant role in contemporary debates in metaphysics, normative ethics, and metaethics. This volume brings historians of Kant's philosophy into conversation with contemporary metaphysicians and ethicists with the aim of representing the current state of scholarship on Kant's and Kantian accounts of freedom while at the same time opening new avenues of exploration. The Idea of Freedom includes papers by leading scholars on a range of historical and contemporary topics centrally related to the Kantian theory of freedom, including transcendental idealism, determinism, Kant's normative ethical theory, Kant's conception of cognition, Kant's theory of beauty, Kant's conception of logic, and many others.