In his later moral writings Kant claims that we have a duty to cultivate certain aspects of our sensuous nature. This claim is surprising for three reasons. First, given Kant's ‘incorporation thesis’ – which states that the only sensible states capable of determining our actions are those that we willingly introduce and integrate into our maxims – it would seem that the content of our inclinations is morally irrelevant. Second, the exclusivity between the passivity that is characteristic of sensibility and the spontaneous quality of our free will that operates throughout Kant's philosophy seems to preclude that any such cultivation is possible. Third, Kant's specific arguments concerning why we are obliged to cultivate our sensible nature are unclear. The goal of this paper is to address each of these three concerns and thus fully explain Kant's theory of the moral necessity of cultivation.