If social scientists are to provide a more useful contribution to international debates over population and environment, we must find ways to combine the insights of our competing theoretical traditions. Political economy, rational choice, and cultural institutionalist perspectives are each associated with a different assessment and characterization of the population "problem", as well as divergent strategies of response, prioritizing in turn the goals of equity, efficiency, and cultural identity. The principal argument of this paper is that these three perspectives, and the goals which they embody, are like the three legs of a stool; none is sufficient and each is necessary to uphold socially acceptable responses to population growth in the context of broader challenges of sustainability. Each perspective is reviewed in turn, distinguishing narrow and polarizing applications that trivialize the way social and economic systems rely on the natural environment from applications that are useful in fashioning a more integrated approach. The paper concludes with reflections on how this approach may support and enrich a focus on sustainable livelihoods in development planning.