According to a common caricature of Kant’s ethics, it is synonymous with the Categorical Imperative (CI) and with the sublime and clarion call of duty. But in this paper, I argue that the conjunction of Kant’s concept of duty and his idea of morality as a system of imperatives is unsustainable on the grounds that it commits him to the following two theses: (I) If an agent has a duty to D, then she must be constrained to D, and (II) the Supreme Law of Morality always manifests in the form of duty for humans. I begin by examining (and rejecting) various attempts to defend these two theses. I then explore how this bears on various central aspects of Kant's thought including “ought implies can” (OIC), “ought implies able not to” (OIAN), his sys...