We discuss the demandingness of Kant’s ethics. Whilst previous discussions of this issue focused on imperfect duties, our first aim is to show that Kantian demandingness is especially salient in the class of perfect duties. Our second aim is to introduce a fine-grained picture of demandingness by distinguishing between different possible components of a moral theory which can lead to demandingness: a required process of decision making, overridingness and the stringent content of demands, due to a standpoint of moral purity. (...) This distinction allows a specification of the sources of demandingness in Kant. The most characteristically Kantian form of demandingness springs from overridingness and purity and comes as a constant threat that an agent might find herself in a situation in which, due to no fault of her own, she is required to sacrifice everything for little to no non-moral goods. Our third aim is to discuss whether Kant has the resources to reply to those who criticize his ethics based on its demandingness. For this purpose we discuss Kant’s notion of “rationalizing” in the context of various types of current conceptions of demandingness and calls for moderate ethical theories. (shrink)