Citizenship shows renewed vitality as a “novel” idea that needs theoretical development. Nations are extending citizenship to increasing numbers and percentages of people within national boundaries, and social scientists are using citizenship theories to explain this movement. As Michael Walzer states (1983, p. 31), “the primary good that we distribute to one another is membership in some human community” and with increasing frequency that “membership” is citizenship in a country. Academic interest has increased in the area of citizenship, and much more is being written using this concept, although little effort has focused systematically on social science theory. This book has taken the confusing welter of materials burgeoning in the area of citizenship and put them into a theoretical framework that is both coherent and capable of being operationalized. In so doing, it has also provided a theoretical foundation for three regime types, which have been previously grounded in left-right distinctions, or in a political theory format of liberalism, communitarianism, and expansive democracy. Each regime type with its characteristic theory has different constraints and accomplishes different things.