Human action is governed by necessitation — the psychological manifestation of the normative standards that govern action at work within us. Sentimentalist and Rationalist theories misconceive the experience of necessitation as a sign that something is wrong with the agent's virtue or rationality. This chapter introduces a different account, according to which necessitation is the experience of a form of work: the work of self-constitution. Following Aristotle and Kant, it distinguishes actions — acts done for the sake of ends — from mere acts, as the objects of choice and the bearers of moral value. We constitute ourselves as agents, and so as the authors of our actions in this sense, in the course of constituting our practical identity. The principles of practical reason govern this process of self-constitution by bringing unity and integrity to the will.