Critics of Jürgen Habermas's theory of communicative action argue that he has failed to recognize the extent to which moral argumentation is grounded in particular historical contexts, cultural traditions, collective identities, or social lifeworlds. Although he has engaged in a series of strategies aimed at acknowledging the role of particularistic considerations without abandoning his primary commitment to ethical universalism, Habermas has not succeeded in meeting all of the objections of his critics. This paper treats the contradiction between formal and substantive (...) rationality, which lies at the heart of the debate, as an empirical phenomenon within the social world. It argues that the antinomy of formal and substantive rationality plays a central role in historical processes of social change. Through critical argumentation, social actors deliberate on contradictions among strategic, moral, and ethical standards of validity, and they struggle to resolve these contradictions through collective action and the reform of laws, policies, and institutions. Examples are drawn from US political history to substantiate the argument, and some questions are raised for further research. (shrink)