IR Theories

IR theories are lenses for making sense of a complex world. No single theory explains everything — but each highlights different forces and makes different predictions.

Realism

The oldest and most influential IR theory. Core claims:

• States are the main actors; international organizations are tools of powerful states
• The international system is anarchic — no world government
• States seek power and security above all else
• Cooperation is fragile because states can never fully trust each other (the "security dilemma" — when one state arms for defense, others feel threatened)
• War is always possible

Key thinkers: Thucydides, Machiavelli, Hans Morgenthau, Kenneth Waltz, John Mearsheimer

Realism explains: Arms races, balance of power politics, NATO expansion, great power competition between the US and China

Liberalism

A more optimistic view. Core claims:

• States can cooperate and build lasting institutions (UN, WTO, EU)
• Economic interdependence makes war more costly and less likely
• Democracies are more peaceful toward each other (democratic peace theory)
• International law and organizations constrain state behavior over time
• Individuals, NGOs, and multinational corporations also matter — not just states

Key thinkers: Immanuel Kant, Woodrow Wilson, Robert Keohane, Joseph Nye

Liberalism explains: The EU, international trade regimes, the democratic peace, global human rights norms

Constructivism

The newest of the three. Core claims:

• The international system is socially constructed — anarchy is "what states make of it" (Alexander Wendt)
• Ideas, norms, and identity matter as much as material power
• State interests aren't fixed — they're shaped by culture, history, and interaction
• Norms can change: slavery was once accepted; now it's universally condemned

Key thinkers: Alexander Wendt, Martha Finnemore, Peter Katzenstein

Constructivism explains: Why norms spread (human rights, sovereignty), identity-based conflicts, the evolution of the taboo against nuclear weapons use