Classical Realism

Classical realism explains international conflict by rooting it in human nature rather than in the structure of the international system. Its adherents argue that individuals — and by extension the statesmen who lead them — are animated by fear, honor, and a drive for power (the animus dominandi, in Hans Morgenthau's phrasing). Because no world government tames these impulses, states pursue power and security as ends in themselves, and ethics in foreign policy is constrained by prudence rather than by universal moral law.

The tradition draws on a long lineage: Thucydides' account of the Peloponnesian War, Machiavelli's The Prince (1532), and Hobbes' Leviathan (1651). Its twentieth-century revival came through E.H. Carr's The Twenty Years' Crisis (1939), which attacked interwar liberal "utopianism," and Morgenthau's Politics Among Nations (1948), which set out six principles of political realism, including the famous claim that statesmen "think and act in terms of interest defined as power." Reinhold Niebuhr added a theological dimension, emphasizing human sinfulness and the tragic character of politics. George F. Kennan and Henry Kissinger applied related ideas to Cold War statecraft.

Classical realism differs from neorealism (or structural realism), associated with Kenneth Waltz's Theory of International Politics (1979), which locates the cause of conflict in anarchy and the distribution of capabilities rather than in human nature. Classical realists therefore retain a place for statesmanship, diplomacy, and moral judgment — qualities Waltz brackets out.

Common critiques include:

• Underdetermination: human nature is a constant, so it cannot explain variation in war and peace.
• Eurocentrism and a narrow canon.
• Difficulty operationalizing concepts like "national interest" and "prudence."

Despite these critiques, classical realism remains influential in foreign policy analysis, particularly in debates over restraint, balance-of-power diplomacy, and the limits of liberal internationalism.