Constructivism in the study of world politics is little more than a decade old, yet in that short time it has risen to challenge realism and liberalism as a leading approach in international relations. Its ascent has been dramatic. One prominent theorist recently suggested that constructivism has now replaced Marxism as the main paradigmatic rival to realism and liberalism. While this particular judgment might be debated—other scholars may wish to defend the continued relevance of a revived Marxist or socialist approach, for example—the fact remains that constructivism has reshaped many core debates in international relations theory.