Central to liberalism, whether conceived as a tradition, an ideology, or as ethical doctrine, is concern for individual liberty. Liberals worry about how individuals can claim and preserve “a certain minimum area of personal freedom which on no account must be violated” (Berlin 1969, 124). The task of the state is to protect that minimum area from arbitrary violations by other people, governments, and institutions. Of course, on the difficult questions of how to define that protected area, which kinds of states and institutions are best suited to do so, and which means are permitted to guarantee and even to extend individual freedom, liberals disagree; indeed, their disagreement on such key issues has helped to keep the tradition vital. Liberals argue about the role of equality, about the nature and importance of democratic self-government, and about the proper relationship between state and society, between liberal tolerance and the shared values of community. Debates on these issues, both within the liberal tradition and between it and competing perspectives, place liberalism at the center of the contemporary discourse of political thought.

Liberalism's contribution to questions of international ethics is more problematic: as one sympathetic interpreter has put it, “international affairs have been the nemesis of liberalism” (Hoffmann 1987, 400). Whereas liberals can claim impressive victories in the realm of domestic politics, the relations among states have proven to be remarkably resistant to liberal reform. The world has yet to emerge from the “lawless state of savagery” Kant deplored in 1784.