This book focuses on the unity, diversity, and centrality of the notion of law as it is employed in Kant's theoretical and practical philosophy. Eric Watkins argues that, by thinking through a number of issues in various historical, scientific, and philosophical contexts over several decades, Kant is able to develop a univocal concept of law that can nonetheless be applied to a wide range of particular cases, despite the diverse demands that these contexts give rise to. In addition, Watkins shows how Kant comes to view both the generic conception of law which he develops and its different particular instances as crucial components of his systematic philosophy as a whole. This volume's new and unified account of a major current running through Kant's work will be important for scholars interested in numerous aspects of his philosophy, from the theoretical and abstract to the practical and empirical.