Liberalism in International Relations

In brief

Liberalism in international relations is the great rival to political realism, and it is best understood against that foil. Realism begins from a bleak premise: because there is no world government above states, world politics is an anarchy in which each state must look to its own power and survival, and conflict is the recurring result. Liberalism accepts the same starting fact, that there is no sovereign over sovereigns, but denies that it must have that ending. Anarchy, on the liberal view, can be tamed.

Three mechanisms do the taming, and together they form the spine of the tradition. Commerce: trade binds states together so that war becomes ruinously expensive, and the merchant's interest in stability pushes against the general's interest in conquest. Shared values: republics and later liberal democracies, whose governments answer to citizens who bear the costs of war, behave differently toward one another and, the evidence suggests, almost never fight each other. Institutions: rules, treaties, and organizations let states escape the trap in which each fears the other will cheat, by making cooperation legible, repeated, and enforceable enough to hold.

The tradition's charter is a short essay by Immanuel Kant, "Toward Perpetual Peace" (1795), which laid out all three ideas in embryo. From it descend two of the most productive research programs in modern political science, democratic-peace theory and neoliberal institutionalism, each of which has its own entry.

The full treatment

The problem it answers

The problem is anarchy, in the technical sense the field uses: not chaos, but the absence of a common authority above states. Realists such as Thomas Hobbes in the seventeenth century, and Hans Morgenthau and Kenneth Waltz in the twentieth, argue that this structural fact drives everything. With no one to call for help and no one to enforce agreements, each state must provide for its own security, and steps one state takes to feel safe make its neighbors feel less safe, which is the security dilemma. On this logic, cooperation is fragile, war is always possible, and the search for peace through trust or law is naive.

Liberalism grants that anarchy is real and that states are self-interested. Its wager is that self-interest, correctly understood, points toward cooperation more often than realism allows, and that the conditions of world politics are not fixed. The character of states matters (a republic is not an empire), the density of their economic ties matters, and the rules they build matter. Change those, and you change how much the anarchy bites.

How it works: the three mechanisms

The first mechanism is commercial. The idea predates the label. Baron de Montesquieu, in "The Spirit of the Laws" (1748), argued for what later scholars would call the doux commerce thesis: "the natural effect of commerce is to lead to peace," because two nations that trade become mutually dependent and neither profits from destroying its customer. Commercial liberalism holds that interdependence pacifies. When economies are woven together, war severs supply, markets, and credit, so the costs of fighting rise and the constituencies that gain from peace grow louder than those that gain from conquest. Norman Angell pressed the strongest version in "The Great Illusion" (1910), arguing that in a modern, financially integrated economy military victory could not pay, so conquest was economically futile. (He was widely and unfairly read after 1914 as having predicted that war was therefore impossible; his actual claim was that it would be irrational and self-defeating, which is a different and more defensible thing.)

The second mechanism is republican, or in modern terms democratic. Kant's insight was that the internal character of a state shapes its external behavior. In a republic, where the citizens who must fight and pay decide on war, they will hesitate, since they bear the costs; in an autocracy, where the ruler can treat war, in Kant's phrase, as a kind of pleasure party that costs him little personally, restraint is weaker. Republican liberalism holds that free, representative government is a force for peace, at least among such governments. This is the seed of democratic-peace theory.

The third mechanism is institutional. States fail to cooperate not only from hostility but from fear of being cheated: the structure of many situations is a prisoner's dilemma, in which each does better by defecting even though both would gain from cooperating (see game-theory). Institutions attack that fear. By providing information, reducing the cost of making and monitoring deals, raising the reputational price of breaking them, and turning one-shot encounters into repeated games, international rules and organizations make cooperation stable enough to sustain even without a world government. This is the seed of neoliberal institutionalism.

The key text: Kant's "Perpetual Peace"

Everything in the tradition traces back to Kant's 1795 essay, which is written, wryly, in the form of a peace treaty. Its heart is three "definitive articles" for peace among states. First, the civil constitution of every state should be republican, government by consent and the rule of law, because citizens who share in decisions will be slow to consent to war. Second, the law of nations should rest on a federation of free states, a pacific league (foedus pacificum) that states join voluntarily to secure their freedom, not a single world empire, which Kant feared would become a "soulless despotism." Third, cosmopolitan right should be limited to conditions of universal hospitality, a modest but real claim that a foreigner arriving peaceably on another's soil should not be treated as an enemy, an early articulation of what we would now call the rights of persons across borders.

Note what Kant did not claim. He did not promise that peace was inevitable or near, and he did not rest it on human goodness. He argued that peace could be built by self-interested, even "devilish," beings if their institutions were rightly arranged, and that the "unsocial sociability" of humanity, its very competitiveness, could be channeled by law toward a lawful condition. The three mechanisms of the whole tradition are already here: republican government, a federation of states, and rights that cross borders.

Distinctions that matter

Liberalism in international relations is not the same as liberalism as a domestic ideology. The domestic doctrine, running from John Locke through John Stuart Mill, is about individual liberty, limited government, and rights within a state; classical-liberalism is its own entry. IR liberalism borrows the emphasis on individuals, rights, and consent, but its subject is relations among states, and one can accept the international theory while holding a range of domestic views.

It is also not idealism or pacifism, though its interwar critics tarred it with both. Serious liberal theory does not deny power, interest, or the possibility of war. It claims that power is not the whole story, that interests can be served by cooperation, and that war becomes less likely under specific, identifiable conditions. Modern liberalism in the field is a causal theory about when and why states cooperate, not a moral hope that they will.

Finally, the tradition is internally plural. Andrew Moravcsik's influential restatement, "Taking Preferences Seriously" (1997), argued that what unifies liberal theory is not optimism but a bottom-up premise: state preferences are formed by the demands of individuals and groups in society, and it is the configuration of those preferences, not the distribution of military power, that best explains state behavior. On this account commercial, republican, and institutional liberalism are three faces of one framework that puts society, not the state-as-billiard-ball, first.

Lineage

The tradition has a clear line of descent. Its philosophical headwaters are the Enlightenment: Montesquieu on commerce (1748), and above all Kant's "Perpetual Peace" (1795), which is the founding text. It draws too on the social-contract tradition, extending the idea that legitimate order rests on consent from the domestic to the international plane.

Its first great political trial came after the First World War. Woodrow Wilson's Fourteen Points (1918) and the League of Nations (founded 1920) were a deliberate attempt to build the Kantian program, collective security, open diplomacy, and self-determination, into the actual order of states. The League's failure to prevent the aggressions of the 1930s and the Second World War discredited liberal thinking for a generation and handed the field to realism, whose founding statement, E. H. Carr's "The Twenty Years' Crisis" (1939), was an attack on interwar liberal "utopianism."

The tradition was rebuilt in the 1970s and 1980s on firmer, more empirical foundations. Robert Keohane and Joseph Nye's "Power and Interdependence" (1977) described a world of "complex interdependence" that realism could not capture. Michael Doyle's two-part study "Kant, Liberal Legacies, and Foreign Affairs" (1983) revived Kant directly and launched the modern study of the democratic peace. Keohane's "After Hegemony" (1984) supplied the institutional theory of cooperation. Moravcsik's 1997 synthesis gave the whole a unified statement. From this base the two dedicated research programs, democratic-peace-theory and neoliberal-institutionalism, grew into the specialized theories they are today.

The strongest case for it

The case for liberalism is that it predicts, and explains, features of world politics that realism struggles with. Start with the one empirical regularity in international relations that comes closest to a law: liberal democracies have almost never gone to war with one another. Doyle and later scholars documented this "democratic peace," and even sharp critics concede the pattern is unusually strong. Realism, which says regime type should not matter, has no clean account of it; liberalism predicted it two centuries in advance.

Second, the sheer density of cooperation is hard to square with a purely realist world. States build and largely obey a vast machinery of trade rules, arms-control regimes, monetary arrangements, and law, and they keep doing so even when a single hegemon is not forcing them to, which is the puzzle Keohane's institutionalism was built to solve. Cooperation under anarchy is not rare; it is ordinary, and liberalism explains why.

Third, the commercial claim has real empirical support: statistical studies over recent decades find that, other things equal, pairs of states with higher trade and economic ties are less likely to fight. Interdependence does appear to dampen conflict, as Montesquieu and Angell argued it should.

Fourth, liberalism captures actors realism ignores. Multinational firms, international organizations, courts, and transnational advocacy networks shape outcomes that a theory of unitary states bouncing off one another cannot see. By starting from society rather than the state as a black box, liberalism reads a world realism renders invisible.

The strongest case against it

The realist critique is old, serious, and not easily dismissed. E. H. Carr's "The Twenty Years' Crisis" (1939) charged interwar liberalism with mistaking its own interests for universal morality and its hopes for facts, and the collapse of the League gave the charge terrible force. The general realist objection stands: liberalism underrates how much the fear of others, and the absence of an enforcer, constrains what states can safely do. In a world where a rival's intentions can change overnight and its capabilities cannot be un-built, prudent states cannot bet their survival on trade ties or shared values.

John Mearsheimer has pressed this hardest in the modern era. In "The False Promise of International Institutions" (1994 to 1995) he argued that institutions are largely epiphenomenal: they reflect the underlying distribution of power and do little independent work, so states abandon or ignore them the moment vital interests are at stake. Where liberals see cooperation, realists see the temporary convenience of the strong.

On interdependence, the critics have history on their side at the crucial moment. Europe in 1914 was more economically integrated than ever before, and it went to war anyway; deep trade did not stop it. Interdependence can even be a weapon: a state dependent on another for energy, chips, or finance is a state that can be coerced, so ties that liberals read as pacifying can be read as new instruments of leverage and vulnerability.

Constructivist critics attack from a different angle (see constructivism-in-international-relations). They argue that liberalism, like realism, takes interests as given by material factors, trade flows and regime type, when in fact interests are socially constructed. Whether interdependence pacifies or provokes, on this view, depends on the shared meanings and identities states attach to one another, which liberalism cannot supply from within its own framework.

Finally there is a critique of liberalism's record in power. The claim that democracies are peaceful toward one another has sometimes hardened into a license to spread democracy by force or to treat non-democracies as inherently threatening, and critics point to interventions justified in liberal terms that produced disorder rather than peace. The theory that promised to tame war has at times been enlisted to wage it.

Where it stands now

Liberalism is one of the two or three central traditions taught in every international relations course, and its two research programs are thriving even as the political weather has turned against them. The democratic-peace finding remains one of the most robust regularities in the field, though scholars still argue over its cause. Institutionalist work continues to explain the design and effects of the dense web of organizations that runs the world economy. The commercial-peace literature is active and, on balance, supportive of the interdependence claim.

The larger climate is harsher than it was in the confident 1990s, when Francis Fukuyama's "The End of History and the Last Man" (1992) read the end of the Cold War as the final triumph of liberal order. The rise of powerful non-democracies, the turn to economic coercion and "weaponized interdependence," democratic backsliding, and open great-power rivalry have revived realist pessimism and given constructivists fresh material. The honest verdict is the one the field has settled into: liberalism is not the whole truth about world politics, but neither is realism. The conditions under which anarchy can be tamed, more trade, shared institutions, accountable government, are real and identifiable, and also fragile and reversible. That is the ground liberalism now holds and defends.

Test yourself

Pick two states that trade heavily with each other and think about whether that trade makes war between them less likely, or simply gives each a new way to squeeze the other. Which reading you find more convincing tells you whether you lean liberal or realist. Then ask the harder question the tradition turns on: is the peace among democracies caused by democracy itself, or by something that tends to travel with it, such as wealth, alliance, or shared enemies? Liberalism stands or falls on that answer.