Critical theory in the Frankfurt School mould has made various inroads into IR theorising, and provided many a stimulus to attempts at redressing the ‘positivist’ imbalance in the discipline. Many of the conceptual offerings of the Frankfurt School perspective have received critical attention in IR theory debates, and while these are still ongoing, the purpose of this discussion is not to attempt to contribute by furthering either methodological interests, or politico-philosophical inquiry. Instead, I focus on the near omission of the social-theoretic aspect of the work especially of Juergen Habermas. I argue that a more in-depth exploration of critical social theory has considerable potential in the context of the ‘social turn’ in IR theory. The lack of attention to this potential is arguably due in part to the importance of Habermas' contribution to cosmopolitan normative theory, and the status held by the cosmopolitan-communitarian debate as a key site of critical IR debate for many years throughout the 1990s. The productivity of the Habermasian conception of the discourse theory of morality within this set of concerns has been obvious, and continues.