International relations : The study of political relations between states or across state boundaries; one of the main subfields of political science. Its principal subdivisions include strategic studies, international organizations, and international political economy. International relations grew out of diplomatic history in the early twentieth century. Its profile was clearest in the decades immediately following World War II, as scholars applied methods such as structuralism, system(s) theory, game theory, and rational-choice theory to derive general propositions about relations between states. This “state-centric” approach has since been contested within the field. Debates have revolved around the question of whether a state can be regarded as a unitary actor, the relative importance of interstate power relations and international organizations, the roles of nonstate actors, and the need to include the study of history, institutions, culture, and other contributing factors. Some scholars therefore call for a more inclusive definition of the field, often under the rubric of “world politics” or “international studies.” Nevertheless, three main schools of thought are generally recognized within contemporary international relations:

1. “Realism” or “power-politics,” the oldest and still the dominant tradition, claims Thucydides, Niccolò Machiavelli, and Thomas Hobbes as its precursors. It holds that the international system is anarchic; that unitary, sovereign, self-interested states are its key actors; and that power and war are its basic currencies. With no international sovereign power, states must help themselves in the struggle for survival. Peace therefore depends on the balance of power, while foreign policy should be based on the prudent calculation of national interest. While realism has been criticized for its cynicism, its blindness to anything but “high politics,” and the vagueness of many of its key concepts, it has dominated the academic study and practice of foreign policy.

2. A “liberal” tradition that descends from natural law theorists such as Hugo Grotius, John Locke, and Immanuel Kant. Often in reaction to realism, liberals argue that states form an international society with the capacity for a rational harmony of interests, including peace, order, and (often) democracy and commerce. They point to the development of international organizations and international law to demonstrate the possibility of cooperation among states, and prefer forms of collective security to the balance of power. Contemporary debates between “neoliberalism” and “neorealism” often hinge on emphasis, with each side conceding both the centrality of states and the growth of interdependence.

3. A number of other approaches contest the priority that both realists and liberals assign to sovereign states, and instead focus on other important determinants of international activity. The most important of these approaches are derived from Marxism and argue that economic relations are the underlying determinants of the international political order. World-systems theory, dependency theory, and much of the work in international political economy can be characterized in these terms. Other approaches include constructivism, which studies how the ideas and institutions of world politics have been socially constructed over time, and pluralism, which examines the diverse nonstate participants in international politics.

“international relations” Dictionary of the Social Sciences. Craig Calhoun, ed. Oxford University Press 2002. Oxford Reference Online. Oxford University Press.