“Discourse ethics” has become a generally accepted, though less than self-explanatory, label for a distinctive intersubjectivist approach in practical philosophy in general, and in moral philosophy in particular. It was first developed by Karl-Otto Apel and Jürgen Habermas from the 1970s onward; among its contemporary philosophical practitioners are Seyla Benhabib, Rainer Forst, and Cristina Lafont. In Anglo-American philosophy, the term “discourse ethics” has frequently been used pars pro toto for a complex conception of practical reason, a comprehensive theory encompassing discourse theories of law and democracy, of morality, and of the good life (e.g. Rawls 1995: 141). More often, it is understood in its narrower sense, as denoting that part of a systematic conception of discursive rationality that is concerned exclusively with claims to universal and categorical practical norms. Discourse ethics in the narrow sense is the philosophical study of morality, while the philosophical study of ethics (in the sense of conceptions of the good life) is another, parallel module within discourse theory as a whole. In both its broad and its narrow sense, discourse ethics seeks to reformulate aspects of Kant’s practical philosophy, drawing inspiration from the public use of reason and from the categorical imperative, especially its co-legislation formula. It follows Kant’s lead in distinguishing a realm of morality proper from a realm of law and politics, but also in sharply profiling a narrow and strictly obligatory field of universal norms against the less stringent fields of the communal or personal values, of supererogation and virtue. Discourse theory parts company with Kantianism in practical philosophy not only in subjecting it to a linguistic and intersubjectivist turn, substituting omnilateral communicative exchanges for Kant’s contemplative (“monological”) method of arriving at binding precepts, but also in embedding practical philosophy in a theory of social evolution. Discourse ethics in both its generic and specific sense is perhaps best understood by focusing on its most influential formulation, that of Jürgen Habermas, in its revised version in and after Between Facts and Norms (1996a). In this work, Habermas continues and transforms the early modern program of “moral philosophy,” leading up to Kant’s Metaphysics of Morals and comprising politics, natural law, morality, and personal virtue. Habermas’ discourse theory attempts to formulate a general account of various complementary normative orders, based on a single discourse principle (D).