Abstract
Despite the prominence of constructivism as a paradigm in International Relations, many remain unclear about a central claim: that all of social reality is socially constructed. This paper explains what that claim means, defends it against common objections, and identifies four major implications it has for the study of international politics. Drawing on Searle’s distinction between brute facts and institutional facts, the paper argues that the entities of international politics exist because humans collectively act as if they exist, and have their effects through the meanings humans attach to them. From this it follows that: political concepts lack fixed essences and must be studied as sites of contestation; radical social change is endemic rather than exceptional; legitimation is a central mechanism of political power; and norms and rules are everpresent features of international politics. Each implication is illustrated with empirical examples drawn from recent scholarship.

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