Some hold that Kant’s conception of autonomy requires the rejection of moral realism in favor of "moral constructivism." However, commentary on a little noticed passage in the Metaphysics of Morals (with the assistance of Kant’s Lectures and Reflexionen) reveals that the conception of legislation at the core of Kant’s conception of autonomy represents a decidedly anti-constructivist strand in his moral philosophy.
I. Summary: the Meaning of "Kant's Moral Constructivism"
A. John Rawls
In A Theory of Justice, although Rawls's method of generating principles of justice from a choice in the Original Position is described as "constructive", in the sense of "helpful to settle disputes", the idea of "constructivism" is hardly present. Constructivism, in the sense that interests us here, first plays a major role in Rawls's 1980 Dewey Lectures, "Kantian Constructivism in Moral Theory", where Rawls clarifies his own project as a limited programme in political theory, not in moral philosophy in general, a programme he has also described as something "political, not metaphysical". (2) There Rawls proposes a procedure of construction that connects a particular conception of the person with first principles of justice. In his article "Themes" Rawls emphasizes a similar idea in his interpretation of Kant moral philosophy, leading him to speak of what he calls "Kant's moral constructivism".
In "Themes" Rawls begins with an outline of the "CI-Procedure" (where CI is an abbreviation for "categorical imperative"), which he sees as something given or laid out, based on the conception of free and equal persons as "reasonable" and "rational". The procedure specifies the first principles of right and justice, and through the procedure the content of the doctrine is constructed. Kant, Rawls had explained in Theory,
begins with the idea that moral principles are the object of rational choice. They define the moral law that men can rationally will to govern their conduct in an ethical commonwealth. Moral philosophy becomes the study of the conception and outcome of a suitably defined rational decision. (3)
In Rawls’s reading, autonomy is given a procedural interpretation according to which it is choice via the procedure which specifies the content of the moral law. Rawls contrasts this constructivism with "rational intuitionism" which maintains that moral principles are true or false in virtue of an order of values, known by rational intuition, that is prior to and independent of our conception of the person. Rawls insists that Kant's conception of "autonomy" rules out the existence of such an order. On Rawls's interpretation, the content of the moral law is constructed by the procedure rather than discovered by it.
The so-called independent order of values does not constitute itself but is constituted by the activity, actual or ideal, of practical (human) reason itself. . . . The intuitionist’s independently given order of values is part of the...