Understanding Kant’s account of desire is vital to the project of evaluating his views about moral psychology, as well as his account of freedom qua autonomy. In Anthropology from a Pragmatic Point of View, Kant claims that “Desire (appetitio) is the self-determination of a subject's power through the representation of something in the future as an effect of this representation” (7:251). My goal is to clarify which of the subject’s specific capacities Kant means by the “subject's power,” and what role this capacity plays in desire. I argue that the subject's power cannot be her capacity to act. Rather, the subject's power is best understood as her capacity to generate the psychological states that cause action. I call these motivational states 'activation signals'. Desire consists in the self-determination of the subject’s capacity to generate activation signals by her representation of the object of desire together with an accompanying incentive.