On Wednesday, October 11, the Department of International Relations held its first Research Seminar of the Academic Year. The speaker, Stefano Guzzini, whose academic career began at CEU and who since then has become one of the leading theorists in International Relations constructivism, talked about the ‘return of geopolitical thinking in Europe.’ This is the subject of his recent edited volume at Cambridge University Press, and also of a forum-discussion organized by the Cooperation and Conflict journal. What Guizzini finds puzzling about the ‘return’ in question is that it happened because of the end of the Cold War, not in spite of it. An historical event that was supposed to undermine realist accounts of international politics reinforced instead one of the most radical streams within realism. To analyze this puzzle Guzzini develops the idea of social mechanisms that, while not purporting to provide any covering-law-like explanations, nevertheless attempts to answer questions that are causal in nature.