This article is an intellectual history of two enduring binaries—society-nature and city-countryside—and their co-identification, told through evolving uses of the concept of 'urban metabolism.' After recounting the emergence of the modern society-nature opposition in the separation of town and country under early industrial capitalism, I interpret 'three ecologies'—successive periods of urban metabolism research spanning three disciplines within the social sciences. The first is the human ecology of the Chicago School, which treated the city as an ecosystem in analogy to external, natural ecosystems. The second is industrial ecology: materials-flow analyses of cities that conceptualize external nature as the source of urban metabolism's raw materials and the destination for its social wastes. The third is urban political ecology, a reconceptualization of the city as a product of diverse socio-natural flows. By analyzing these three traditions in succession, I demonstrate both the efficacy and the limits to Catton and Dunlap's distinction between a 'human exemptionalist paradigm' and a 'new ecological paradigm' in sociology.