John Rawls’s Lectures on the History of Moral Philosophy are an indispensable aid for understanding Rawls’s Kantian constructivism, for they testify to the fact that his approach to normative justification develops out of a dialogue not only with Kant, but also Hume and Hegel. This chapter focuses on the similarities between Rawls’s Hegelian reading of Kant and recent post-Kantian interpretations of Hegel and the light this sheds on the nature and development of Rawls’s constructivism. Rawls’s lectures follow a Hegelian approach in seeking to reconcile Hume’s naturalistic idea of justice as an evolved social practice and Kant’s metaphysical conception of moral autonomy. It is argued that such an approach offers the best prospects for reconciling the twin demands of reflective endorsement and objectivity within constructivism. However, in conclusion, reservations are raised about the practical ambition that is the reverse side of the apparent philosophical modesty of Rawls’s post-Kantian constructivism.