Debates over how ideas matter in international relations have come to occupy a key place in the field. Through a reexamination of the thinking of Hans Morgenthau, this article seeks to recover a tradition of classical realism that stressed the role of ideas in both the construction of action and in political and ethical judgment. Locating Morgenthau's understanding of politics against the background of the oppositional “concept of the political” developed by the controversial jurist Carl Schmitt shows how Morgenthau's realism attempts to recognize the centrality of power in politics without reducing politics to violence, and to preserve an open and critical sphere of public political debate. This understanding of Morgenthau's realism challenges many portrayals of his place in the evolution of international relations, and of the foundations of realist thought. However, it is also of direct relevance to current analyses of collective identity formation, linking to—and yet providing fundamental challenges for—both realist and constructivist theories.