In this essay, Pauline Kleingeld notes that Kant’s Principle of Autonomy, which played a central role in both the Groundwork for the Metaphysics of Morals and the Critique of Practical Reason, disappeared by the time of the Metaphysics of Morals. She argues that its disappearance is due to significant changes in Kant’s political philosophy. The Principle of Autonomy states that one ought to act as if one were giving universal laws through one’s maxims. The criterion of just legislation that Kant accepted in the mid-1780s does not require any actual consent on the part of the citizens—genuine universality is sufficient for a law to be just. Hence, at that time, Kant could indeed explicate the criterion governing the moral permissibility of one’s maxims by drawing an analogy with the criterion governing the justice of political laws. In the Metaphysics of Morals and in other works in the 1790s, however, he added the further condition that laws must be given with the consent of the citizens. With this further condition, the moral criterion was no longer fully analogous to the criterion for political laws being just. Accordingly, Kleingeld argues, Kant dropped the Principle of Autonomy, which was firmly based on that analogy.