International regimes are defined as principles, norms, rules, and decisionmaking procedures around which actor expectations converge in a given issue-area. As a starting point, regimes have been conceptualized as intervening variables, standing between basic causal factors and related outcomes and behavior. There are three views about the importance of regimes: conventional structural orientations dismiss regimes as being at best ineffectual; Grotian orientations view regimes as an intimate component of the international system; and modified structural perspectives see regimes as significant only under certain constrained conditions. For Grotian and modified structuralist arguments, which endorse the view that regimes can influence outcomes and behavior, regime development is seen as a function of five basic causal variables: egoistic self-interest, political power, diffuse norms and principles, custom and usage, and knowledge.