Liberalism is one of the major theoretical traditions in international relations. Against the realist view that anarchy forces states into perpetual security competition, liberals argue that cooperation under anarchy is possible and often rational. The tradition draws on Enlightenment thinkers — notably Immanuel Kant, whose 1795 essay Perpetual Peace sketched a federation of republics — and on later writers like Hugo Grotius, John Locke, and Woodrow Wilson, whose Fourteen Points (1918) framed self-determination and a League of Nations as routes to peace.
Modern liberal IR theory branches into several strands:
- Liberal institutionalism (Robert Keohane, Joseph Nye): institutions such as the WTO, IMF, and UN reduce transaction costs, provide information, and lengthen the "shadow of the future," making defection costlier. Keohane's After Hegemony (1984) is a foundational text.
- Democratic peace theory (Michael Doyle, Bruce Russett): mature democracies rarely, if ever, go to war with one another, because of shared norms and institutional constraints on executives.
- Commercial liberalism: economic interdependence raises the cost of conflict, an idea traceable to Montesquieu and Norman Angell's The Great Illusion (1909).
- Republican / sociological liberalism (Andrew Moravcsik): state preferences emerge from domestic society, so the configuration of interests across borders shapes outcomes.
Liberals do not deny that states pursue interests or that power matters; they argue that interests are broader than survival and that absolute gains, reputation, and legalized commitments can sustain cooperation. The theory underpins much of the post-1945 order — Bretton Woods, the GATT/WTO system, the EU, and the human-rights regime.
Critics include realists, who point to institutional failures (the League of Nations in the 1930s, UN paralysis over Syria); constructivists, who argue liberalism takes preferences as given; and Marxist or post-colonial scholars, who view liberal institutions as instruments of Western hegemony. Debates intensified after the 2003 Iraq War and again amid the post-2016 backlash against the "liberal international order."
Example
In the 1990s, the expansion of NATO and the EU into Central and Eastern Europe was justified in liberal terms — locking in democracy, markets, and shared institutions to make a return to interstate war less likely.
Frequently asked questions
Realists see anarchy as forcing states to prioritize relative power and survival; liberals argue institutions, trade, and democracy let states pursue absolute gains and sustain cooperation despite anarchy.
Keep learning