Realism (classical, neorealism, offensive/defensive)
Realism in IR — classical, neorealism, and the offensive/defensive split — mapped to UPSC GS-2, FSOT, CSS and BCS, with thinkers, texts and exam application.
The realist premise
Realism is the oldest and most durable tradition in International Relations, treating the struggle for power among self-interested states under anarchy as the permanent condition of world politics. Its intellectual lineage is cited from Thucydides' History of the Peloponnesian War (the Melian Dialogue, 416 BCE: "the strong do what they can and the weak suffer what they must"), through Niccolò Machiavelli's The Prince (1532) and Thomas Hobbes's Leviathan (1651, the "state of nature" as a war of all against all). Realism's three load-bearing assumptions are: states are the principal actors; the international system is anarchic (no government above states); and states pursue power and survival as the rational core of the national interest.
Classical realism: human nature
Classical realism locates the drive for power in human nature itself — the animus dominandi, or lust for domination. Its canonical statement is Hans Morgenthau's Politics Among Nations (1948), whose Six Principles of Political Realism insist that politics is governed by objective laws rooted in human nature, that the signpost of realism is "interest defined in terms of power," and that universal moral principles cannot be applied to state action in their abstract formulation. E. H. Carr's The Twenty Years' Crisis, 1919–1939 (1939) is the companion text, attacking inter-war "utopianism" (Wilsonian liberalism) for ignoring the role of power. For classical realists, statecraft is prudence: matching commitments to capabilities, and balancing power against power.
Why the structural turn
Classical realism's reliance on human nature was criticised as unfalsifiable and reductionist. The corrective came from Kenneth Waltz's Theory of International Politics (1979), which relocated the cause of conflict from human nature to the structure of the system. Waltz's earlier Man, the State, and War (1959) had already organised explanations into three images (or levels of analysis): the individual, the state, and the international system. His mature claim is that the third image — anarchy and the distribution of capabilities — best explains recurring patterns such as the balance of power, which Waltz treats as an automatic tendency of the system rather than a deliberate policy. This structural reformulation is neorealism (structural realism), and it dominates the modern syllabus. Candidates must be able to state crisply the move from Politics Among Nations (1948) to Theory of International Politics (1979): from human nature to system structure, from reduction to the unit level to explanation at the systemic level.