IN THIS PAPER it is argued that the theoretical purview and contemporary political relevance of agro-food studies are significantly weakened by their methodological foundations, still largely unexamined, in modernist ontology. A critical element of this ontology, shared with orthodox social science, is the dualistic separation of nature and society. Nature is theorized in externalized and mechanistic terms, and thereby abstracted from the social domain. The modernist ontology thus supports the objectification of nature and its de-politicization, undermining coherent engagement with the bio-politics and ethical principles of environmental organizations and Green movements. The ubiquity of the modernist nature/society dichotomy and its disabling consequences are examined by analysing several recent theoretical perspectives in agrarian studies. The merits of actor-network theory in surmounting these ontological and epistemological limitations then are considered using three brief case studies of the highly contested bio-politics of agro-food networks.