Is moral constructivism an account of the basis of the content of morality or of its authority? In fact, different writers have understood constructivism to be addressing different issues. In this paper I argue that Kant should be understood as a constructivist about the content of morality – or better about a limited set of general substantive principles – and as a constititutivist about its authority. After some general remarks in Section 1 about contemporary discussions of constructivism, in Section 2 (...) I discuss Rawls’s understanding of Kant’s constructivism; Rawls takes Kantian constructivism to be a view about the content of morality. In Section 3, I give an overview of Kant’s moral conception as constructivist about the content of morality and as constitutivist about its authority. In Section 4 I address a worry whether certain features of Kant’s constitutivism rest his constructivism on a realist foundation, arguing that they do not. (shrink)