John Rawls, "Kantian Constructivism in Moral Theory: The Dewey Lectures," Journal of Philosophy 77 (1980): 515–72.
In these lectures I examine the notion of a constructivist moral conception, or, more exactly, since there are different kinds of constructivism, one Kantian variant of this notion. The variant I discuss is that of justice as fairness, which is presented in my book A Theory of Justice. I have two reasons for doing this: one is that it offers me the opportunity to consider certain aspects of the conception of justice as fairness which I have not previously emphasized and to set out more clearly the Kantian roots of that conception. The other reason is that the Kantian form of constructivism is much less well understood than other familiar traditional moral conceptions, such as utilitarianism, perfectionism, and intuitionism. I believe that this situation impedes the advance of moral theory.
University of Texas [pdf]