The end of the Cold War helped to prompt new interest in the study of ideas in international politics. Once the province of a few dedicated researchers on the fringes of the discipline, scholarship on the role of ideas now occupies an important place in the mainstream of North American and especially European international relations research. The five articles in this special issue of the journal are intended to move the research agenda on ideas and the end of the Cold War to a new level of rigor. They develop new models of how ideas affected the outcome and, in so doing, take stock of this event to refine our understanding of how ideas work in international politics. Although we seek a deeper understanding of the end of the Cold War itself, we also use this seminal case to clarify and advance the debate over the role of ideas in international politics more generally.

The articles in this special issue of the journal succeeded in meeting the core objective set out in the introduction: to refine, deepen, and extend previous studies of the role of ideas in the end of the Cold War. In particular, they confront more forthrightly than past studies a major challenge of studying ideas in this case; namely, that ideas, material incentives, and policy all covaried. Two other important problems for those seeking to establish an independent role for ideas remain to be addressed in future studies. Facing those problems as squarely as the contributors to this issue have faced the covariation problem will yield major benefits for the study of ideas in this case and in international relations more generally.

So far, scholars of international politics have displayed relatively little inclination to use new evidence from Cold War-era archives to test their theories and generalizations. This indifference is unfortunate. The new archival evidence and memoirs can—and should—provide a reality check for theoretical debates. It is time for students of international relations to recognize the crucial link between historical explanation and theoretical propositions.