Progress, then, is a kind of collective thinking, which lacks a brain of its own, but which is made possible, thanks to imitation, by the solidarity of the brains of numerous scholars and inventors who interchange their successive discoveries.Gabriel Tarde (1969, 179) Recently there has been a resurgence in the study of how ideas shape policies (see Bockman and Eyal [2002] and Fourcade-Gourinchas and Babb [2002] for two different views.) Two perspectives which dominate this literature are what Habermas has called the empirical-analytical tradition and historical-hermeneutic tradition (1968). These two epistemological positions represent contrasting views. They depict very different pictures of how ideas sway popular values and the policy choices confronted by policymakers. Each also raises important questions about how the processes of knowledge formation and promotion unfold and what actors play a dominant role in furthering these developments.This paper focuses on the formation and institutionalization of mainstream sustainable development knowledge. It puts forward a model of how development ideas are formulated and, later, become ingrained. The process of knowledge formation proposed here begins with a historical and constructive interpretation of the diffusion and institutionalization of development ideas (Latour and Woolgar 1986;Knorr-Cetina 1981). A key assertion derived from this model is that knowledge evolves in dynamic and interrelated phases, propelled by ties among an elite core of intellectuals who form a network. As ideas move from conceptualization to institutionalization, the composition of these networks changes. Intellectual experts progressively relinquish their claims or are pushed aside by members of a more powerful clique of public intellectuals (Jacoby 2000). Making the transition from the academy to the public sphere is an important precondition for ideas to take hold and be established as part of policy paradigms. Thus, one of the implications of this study is that, while many ideas are generated among academ-