Neorealism
Waltz's key contribution to the realm of political science is in the creation of neorealism (or structural realism, as he calls it), a theory of International Relations which posits that the interaction of sovereign states can be explained by the pressures exerted on them by the anarchic structure of the international system, which limits and constrains their choices. Neorealism thus aims to explain recurring patterns in international relations, such as why relations between Sparta and Athens resembled those between the U.S. and the USSR in some important ways.
Waltz emphasizes repeatedly in this book and elsewhere that he is not creating a theory of foreign policy, which aims to explain the behavior or actions of a particular state at a specific time or throughout a period. A sizable amount of criticism of Waltz's balance-of-power theory has been made by scholars who find it unsatisfactory in explaining the foreign policy choices of particular states or in particular areas like nuclear proliferation.
Waltz argues that the world exists in a state of perpetual international anarchy. Waltz distinguishes the anarchy of the international environment from the order of the domestic one. In the domestic realm, all actors may appeal to, and be compelled by, a central authority - 'the state' or 'the government' - but in the international realm, no such source of order exists. The anarchy of international politics – its lack of a central enforcer – means that states must act in a way that ensures their security above all, or else risk falling behind. This is a fundamental fact of political life faced by democracies and dictatorships alike: except in rare cases, they cannot count on the good will of others to help them, so they must always be ready to fend for themselves.
Like most neorealists Waltz accepts that globalization is posing new challenges to states, but he does not believe states are being replaced, because no other non-state actor can equal the capabilities of the state. Waltz has suggested that globalization is a fad of the 1990s and if anything the role of the state has expanded its functions in response to global transformations.
Neorealism was Waltz's response to what he saw as the deficiencies of classical realism. Although the terms are sometimes used interchangeably, neorealism and realism have a number of fundamental differences. The main distinction between the two theories is that classical realism puts human nature, or the urge to dominate, at the center of its explanation for war, while neorealism stakes no claim on human nature and argues instead that the pressures of anarchy shape outcomes regardless of human nature or domestic regimes.
Waltz's theory, as he explicitly makes clear in "Theory of International Politics", is not a theory of foreign policy and does not attempt to predict or explain specific state actions, such as the collapse of the Soviet Union. The theory explains only general principles of behavior that govern relations between states in an anarchic international system, rather than specific actions. These recurring principles of behavior include balancing of power (the theory was revised by Stephan Walt, modifying the "balance of power" concept to "balance of threat"), entering into individually sub-optimal arms races, and exercising restraint in proportion to relative power. In Theory of International Politics (1979:6) Waltz suggests that explanation rather than prediction is expected from a good social science theory, since social scientists cannot run controlled experiments that give the natural sciences so much predictive power.
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