In the title of his 1980 Dewey Lectures, Rawls famously characterizes his theory of justice as fairness as an example of “Kantian Constructivism in Moral Theory.” This description clearly identiies constructivism as a particular option in moral philosophy, to be contrasted with other “familiar traditional moral conceptions, such as utilitarianism, perfectionism, and intuitionism” (CP 303). The description also implies that there can be different versions of constructivism, of which the Kantian form is only one. Since the Dewey Lectures, there has been great interest in constructivism as a potentially distinct option in moral theorizing, but little agreement about what constructivism actually is, or about whether it can ever be fairly described as Kantian.

The dificulties can be traced back to Rawls’s own deinition. “What distinguishes the Kantian form of constructivism is essentially this: it speciies a particular conception of the person as an element in a reasonable procedure of construction, the outcome of which determines the content of the irst principles of justice” (CP 304). It is not so hard to see how this deinition applies to Rawls’s own theory of justice. He speciies a particular conception of persons as characterized by the two moral powers, possessing both a conception of the good and a sense of justice, and thus to be treated as free and equal. He then uses this conception of the person as an element in a procedure of construction, the original position, in which the free and equal persons themselves choose the two fundamental principles of justice, the principle of equal liberty and the difference principle. So a natural interpretation of Rawls’s deinition would seem be: a constructivist moral theory is one in which some suitably characterized set of persons selects moral principles for themselves, and the Kantian form of constructivism is one in which the set of persons is characterized in a speciically Kantian way.