This article examines the contemporary disciplinary claims that the ‘Second Debate’ in international theory was partial and incomplete. Developing the view that the debate exclusively concerned positivist methods, not the status and merits of social scientific inquiry in international relations theory (IR) more broadly, the article advances an understanding of how contemporary ‘social scientific’ IR has begun to integrate historicist and generalising claims in a single theoretical framework. Moreover, the article seeks to transcend the assumption of incommensurability between scientific and historical frames of inquiry that characterised the idea of scientific inquiry in the Second Debate, and does this through an intellectual history of arguments for a ‘science of society’. The article shows how the emergence of non-positivist alternatives entails the development of abstractions and limited generalisations based on ‘mechanismic explanation’, particularly suitable for the development of middle-range theorising in IR. Overall, we argue that one important implication of the named methodological discussion is the reinforcing of the place of historical sociological analysis at the centre stage of international theory.