Over the past decade, international theory in the United States has often been presented as locked in a struggle between realism and liberal institutionalism. Such an understanding, as I suggested at the end of chapter 2, is largely misguided. Realism and institutionalism – or any other theory or approach – are not potential substitutes for one another. They are “competing” approaches only in the sense that they focus on different forces and thus may provide “better” or “worse” – or at least different – insights in particular cases.

Realist critiques of international institutions, however, do raise two important questions. How much of an impact can international institutions have in principle? And what effects do they in fact have in contemporary international relations? Or, to pose the problem from the opposite direction, can structural realism get by with ignoring (abstracting from) international institutions? I will argue that it cannot.

As is common in the discipline, I use “institutions” in the widest possible sense to refer to regularized patterns of interaction based on formal or informal rules and understandings. Institutions thus include, but go well beyond, bureaucratic organizations (a much narrower sense of the term). They include social practices such as kinship, kingship, property, promises, alliances, sovereignty, and international law. Institutions provide a web of relationships through which social interaction is shaped and channeled.

Norms, understood as guiding rules or principles, are a part of most institutions. Norms establish rules, roles, and meanings that shape, constrain, enable, and even constitute states and other international actors. Although the phrase “norms and institutions” may be redundant, I will often use it in order to emphasize the regulative and other normative dimensions of international institutions.