Studies in this issue show that the epistemic communities approach amounts to a progressive research program with which students of world politics can empirically study the role of reason and ideas in international relations. By focusing on epistemic communities, analysts may better understand how states come to recognize interests under conditions of uncertainty. According to this research program, international relations can be seen as an evolutionary process in which epistemic communities play meaningful roles as sources of policy innovation, channels by which these innovations diffuse internationally, and catalysts in the political and institutional processes leading to the selection of their shared goals. The influence of epistemic communities persists mainly through the institutions that they help create and inform with their preferred world vision. By elucidating the cause-and-effect understandings in the particular issue-area and familiarizing policymakers with the reasoning processes by which decisions are made elsewhere, epistemic communities contribute to the transparency of action and the development of common inferences and expectations and thereby contribute to policy coordination. International cooperation and, indeed, the development of new world orders based on common meanings and understandings may thus depend on the extent to which nation-states apply their power on behalf of practices that epistemic communities may have helped create, diffuse, and perpetuate.