politics in primarily ideational, rather than material, terms. Norms Constructivist scholars have explored in-depth the role of norms in world politics. Abram Chayes and Antonia Handler Chayes have defined “norms” as “a broad class of prescriptive statements – rules, standards, principles, and so forth – both procedural and substantive” that are “prescriptions for action in situations of choice, carrying a sense of obligation, a sense that they ought to be followed”. Norm-based constructivist approaches generally assume that actors tend to adhere to a “logic of appropriateness”. That means that actors follow “internalized prescriptions of what is socially defined as normal, true, right, or good, without, or in spite of calculation of consequences and expected utility”. This logic of appropriateness stands in contrast to the rational choice “logic of consequences”, where actors are assumed to choose the most efficient means to reach their goals on the basis of a cost-benefit analysis. Constructivist norm scholarship has investigated a wide range of issue areas in world politics. For example, Peter Katzenstein and the contributors to his edited volume, The Culture of National Security, have argued that states act on security choices not only in the context of their physical capabilities but also on the basis of normative understandings. Martha Finnemore has suggested that international organizations like the World Bank or UNESCO help diffuse norms which, in turn, influence how states define their national interests. Finnemore and Kathryn Sikkink have explored how norms affect political change. In doing so, they have stressed the connections between norms and rationality, rather than their opposition to each other. They have also highlighted the importance of “norm entrepreneurs” in advocating and spreading certain norms. Some scholars have investigated the role of individual norms in world politics. For instance, Audie Klotz has examined how the global norm against apartheid developed across different states (the United Kingdom, the United States, and Zimbabwe) and institutions (the Commonwealth, the Organization of African Unity, and the United Nations). The emergence and institutionalization of this norm, she argued, has contributed to the end of the apartheid regime in South Africa. Nina Tannenwald has made the case that the non-use of nuclear weapons since 1945 can be attributed to the strength of a nuclear weapons taboo, i.e., a norm against the use of nuclear weapons. She has argued that this norm has become so deeply embedded in American political and social culture that nuclear weapons