  Habermas summarizes his idealized conception of practical discourse in the “discourse principle” (D), which we might state as follows: A rule of action or choice is justified, and thus valid, only if all those affected by the rule or choice could accept it in a reasonable discourse. Although he first understood (D) as a principle of moral discourse, he now positions it as an overarching principle of impartial justification that holds for all types of practical discourse (cf. 1990a, 66, 93; 1996b, 107). As such, it simply summarizes his argumentation theory for any question involving the various “employments of practical reason” (1993, chap. 1). (D) thus applies not only to moral rightness and ethical authenticity, but also to the justification of technical-pragmatic claims about the choice of effective means for achieving a given end. Each type of practical discourse then involves a further specification of (D) for the content at issue. In developing his democratic theory, Habermas has been especially concerned with two such specifications: moral discourse and legal-political discourse. In distinguishing these two types of discourse, Habermas tackles the traditional problem of the relationship between law and morality. He also shows how to bring ethereal discursive idealizations down to institutional earth. We start with his account of moral discourse.