This paper first aims to draw attention to, and diagnose, the failure of IR’s ‘sociological turn’ to extend the domain of sociological reason into the philosophical turf of epistemology and thereby fulfill the full promises of the ‘post-positivist turn’. Its second purpose is to revive and deploy the radical version of the sociology of knowledge that can achieve an autonomous reconstruction of epistemology suited to a reflexive, post-Kantian consciousness. The diagnosis begins by tracing the erasure of the radical sociological position in the connected evolutions of Sociology and IR. It shows that the derailing of the ‘sociological revolution’ was paradoxically mediated by the consolidation of social constructionism and science studies, reproduced in IR through their counterparts in the ‘sociological turn’: Constructivism and the sociology of IR. In these otherwise reflexive developments the progression of sociological reason was halted by a self-imposed limitation on the extension of sociological analysis to all domains of thought, and the endorsement of an idealist and institutionalist ontology of ‘the social’. A reformulation of the forgotten, radical sociological position clarifies the implications for IR of a transition to a post-philosophical theory of knowledge, and delineates an empirical research agenda for such a reconstruction of epistemology driven by a sociology of knowledge of a ‘revolutionary’ persuasion. Exploring the centrality of social practice in the social determination of knowledge, the paper argues that, and shows how, a properly reflexive reconstruction of epistemology is best achieved by deploying the sociology of knowledge in two complementary materialist directions: a sociology of everyday social practices that illuminates our epistemic immersion in the ‘carpentered environments’ of the socio-natural order, and a sociology of craft that objectivates the social constitution of the skholè as a mode of existential boundedness by addressing scholarly thought as differentiated social labor.