48 International Organization formal institutions at all).Only advocates of a new ideology of integration-what I call the"community model"perceived interests in the unprecedented institutional project showcased in the ECSC and EEC.Had Europeans followed other viable, historically active ideas about their interests in cooperation-the "confederal"or "traditional"models-they would have solved their problems through more stan- dard diplomatic instruments.Today's Europe would reflect the rule,not the exception,in international relations. This argument confronts two major obstacles.The first is theoretical:Isolating ideas as causes is difficult.A growing literature points to actors'subjective beliefs as important causes of political outcomes.But if ideational theorists argue persua- sively that ideas are often non-negligible factors in politics,they have trouble specifying how much ideas matter.Skeptics thus remain free to dismiss ideas as residual to objective responses to structural or institutional constraints.I argue that certain conditions allow for more concrete and specific claims about ideas.Where ideas strongly cross-cut lines of shared material interests in a polity,we can isolate individuals'beliefs most clearly from objective pressures.Cross-cutting ideas can also fragment coalitions and parties,creating situations similar to the "chaos"and "multiple equilibria"described by game theorists.Entrepreneurial leaders may gain the autonomy to set the policy agenda around their own personal ideas,and to mobilize one of several potential coalitions behind them.Leaders'ideas,as an autonomous causal factor,thereby select from a range of structural and institutional possibilities. The second obstacle is historical:Tracing certain ideas across Europe and the 1950s is an immense task.I surmount this problem by focusing on the pivotal case of French strategic choices.Experts agree that European cooperation took the shape it did in the 1950s-the institutionally strong,geographically limited EECabove all because the French government demanded it.The preferences of the other main actors(Germany,Britain,Benelux)summed to favor broader and weaker institu- tional options.I show that rather than reflecting structural or institutional pressures, French insistence on the EEC resulted from community-minded leadership.Alter- native confederal or traditional French strategies were strongly represented and at least as viable domestically and internationally and would have oriented European bargaining to different outcomes.The differences between the EEC and these alternatives display the range across which French community ideas mattered. Ideas and the "How Much?"Problem Ideas are subjective claims about descriptions of the world,causal relationships,or the normative legitimacy of certain actions.The basic reasons to suspect that ideas 3.See Hall 1989 and 1993:Onuf 1989:Wendt 1989 and 1997:Sikkink 1991:Goldstein 1993; Goldstein and Keohane 1993:Checkel 1993:Katzenstein 1996:Kier 1997:McNamara 1998:and Berman 1998.formal institutions at all). Only advocates of a new ideology of integration—what I call the “community model”—perceived interests in the unprecedented institutional project showcased in the ECSC and EEC. Had Europeans followed other viable, historically active ideas about their interests in cooperation—the “confederal” or “traditional” models—they would have solved their problems through more stan￾dard diplomatic instruments. Today’s Europe would reflect the rule, not the exception, in international relations. This argument confronts two major obstacles. The first is theoretical: Isolating ideas as causes is difficult. A growing literature points to actors’ subjective beliefs as important causes of political outcomes.3 But if ideational theorists argue persua￾sively that ideas are often non-negligible factors in politics, they have trouble specifying how much ideas matter. Skeptics thus remain free to dismiss ideas as residual to objective responses to structural or institutional constraints. I argue that certain conditions allow for more concrete and specific claims about ideas. Where ideas strongly cross-cut lines of shared material interests in a polity, we can isolate individuals’ beliefs most clearly from objective pressures. Cross-cutting ideas can also fragment coalitions and parties, creating situations similar to the “chaos” and “multiple equilibria” described by game theorists. Entrepreneurial leaders may gain the autonomy to set the policy agenda around their own personal ideas, and to mobilize one of several potential coalitions behind them. Leaders’ ideas, as an autonomous causal factor, thereby select from a range of structural and institutional possibilities. The second obstacle is historical: Tracing certain ideas across Europe and the 1950s is an immense task. I surmount this problem by focusing on the pivotal case of French strategic choices. Experts agree that European cooperation took the shape it did in the 1950s—the institutionally strong, geographically limited EEC—above all because the French government demanded it. The preferences of the other main actors (Germany, Britain, Benelux) summed to favor broader and weaker institu￾tional options. I show that rather than reflecting structural or institutional pressures, French insistence on the EEC resulted from community-minded leadership. Alter￾native confederal or traditional French strategies were strongly represented and at least as viable domestically and internationally and would have oriented European bargaining to different outcomes. The differences between the EEC and these alternatives display the range across which French community ideas mattered. Ideas and the “How Much?” Problem Ideas are subjective claims about descriptions of the world, causal relationships, or the normative legitimacy of certain actions. The basic reasons to suspect that ideas 3. See Hall 1989 and 1993; Onuf 1989; Wendt 1989 and 1997; Sikkink 1991; Goldstein 1993; Goldstein and Keohane 1993; Checkel 1993; Katzenstein 1996; Kier 1997; McNamara 1998; and Berman 1998. 48 International Organization