 With a few exceptions, the social science literature conceives of norms as exogenous variables. Since norms are mainly seen as constraining behavior, some of the key differences between moral, social, and legal norms—as well as differences between norms and conventions—have been blurred. Much attention has instead been paid to the conditions under which norms will be obeyed. Because of that, the issue of sanctions has been paramount in the social science literature. Moreover, since social norms are seen as central to the production of social order or social coordination, research on norms has been focused on the functions they perform. Yet even if a norm may fulfill important social functions (such as welfare maximization or the elimination of externalities), it cannot be explained solely on the basis of the functions it performs. The simplistic functionalist perspective has been rejected on several accounts; in fact, even though a given norm can be conceived as a means to achieve some goal, this is usually not the reason why it emerged in the first place (Elster 1989a, 1989b). Moreover, although a particular norm may persist (as opposed to emerge) because of some positive social function it fulfills, there are many others that are inefficient and even widely unpopular.