Teaching International Relations

Overview

Why did Russia invade Ukraine? Why are European leaders flying to Beijing as Washington turns inward? Why is NATO suddenly talking about spending 5% of GDP on defense? The answer depends on who you ask – and on the theoretical lens they use.

This module introduces the three foundational traditions of international relations theory: realism, liberalism, and constructivism. Each offers a distinct account of what drives state behavior, why conflict occurs, and whether cooperation is possible under anarchy. Realists emphasize power and self-interest. Liberals point to institutions, trade, and democracy. Constructivists argue that ideas, identities, and norms shape what states want and how they act.

No single tradition explains everything. The analytical skill this module develops is the ability to apply each lens to the same event and understand what it reveals – and what it obscures. The module closes with a live framing experiment that demonstrates, using students’ own responses, how the way we describe the world shapes what we expect from it.

Realism

Realism is historically the most influential tradition in IR. Its core claims are stark: global politics is fundamentally about power and self-interest; the international system operates in anarchy (no authority above states); and in this environment, states must rely on themselves for survival. This is the logic of self-help and Realpolitik.

But realism is not monolithic. Its variants disagree sharply about why states pursue power and how much power they need.

Classical Realism

Classical realists locate the source of conflict in human nature. Drawing on Thucydides, Machiavelli, and Hobbes, they argue that people are inherently selfish and competitive – and that this egoism scales up to the state level. As Hans Morgenthau wrote, the social world is “a projection of human nature onto the collective plane.” E.H. Carr made a similar case in The Twenty Years’ Crisis (1939), arguing that the idealism of the interwar period ignored the realities of power and set the stage for catastrophe.

For classical realists, conflict is an enduring tendency of international politics because the flaws that produce it are hardwired into human beings. Cooperation is possible but fragile, always vulnerable to the reassertion of self-interest.

Structural Realism

Kenneth Waltz broke with classical realism in Theory of International Politics (1979) by arguing that human nature is not the issue. What matters is structure: the anarchic organization of the international system itself. Because there is no world government to enforce agreements or protect states, every state must look after its own security. This structural condition – not the moral failings of leaders – drives competition and conflict.

Waltz’s structural realism (or neorealism) shifted the analytical focus from the unit level (human nature, domestic politics) to the system level (the distribution of power among states). But structural realists themselves split into two camps over a crucial question: how much power is enough?

Offensive Realism

Offensive realists argue that states are power maximizers. Under anarchy, uncertainty about other states’ intentions creates incentives to accumulate as much power as possible. Great powers, in particular, aim for regional hegemony – dominance over their own neighborhood – because you can never be sure you have enough power to guarantee your survival.

John Mearsheimer’s The Tragedy of Great Power Politics (2001) is the foundational text. A standard illustration is the rise of China as a challenge to U.S. primacy in East Asia: from this perspective, competition between a rising power and an established hegemon is structural and difficult to avoid.

Defensive Realism

Defensive realists see states as security maximizers, not power maximizers. The key insight is that overexpansion is counterproductive: grabbing too much power provokes other states to balance against you, leaving you less secure than before. States are better served by strategies of balancing (building capabilities internally or forming alliances externally) and restraint.

Waltz himself leaned defensive, and Stephen Walt extended the framework with his balance of threat theory, arguing that states balance not just against power but against perceived threats. The Cold War logic of nuclear deterrence – mutual assured destruction keeping both superpowers in check – is a classic defensive realist scenario.

Neoclassical Realism

Since the 1990s, neoclassical realists have argued that international structure matters but cannot explain everything. Domestic factors – state capacity, ideology, leadership perceptions, and domestic politics – mediate how states respond to structural pressures. The system creates incentives, but sub-national factors shape the choices states actually make.

Nazi Germany is a telling example. A strict structural realist might attribute German expansion to systemic pressures, but neoclassical realists emphasize that domestic ideology and Hitler’s personal ambitions were crucial. States do not always respond rationally to structural incentives. Key scholars in this tradition include Gideon Rose (who coined the term), Randall Schweller, Fareed Zakaria, Jennifer Sterling-Folker, and Keren Yarhi-Milo, whose work on leader psychology examines how individual perceptions of adversaries shape foreign policy.

Liberalism

Where realists see an arena of relentless competition, liberals see the possibility of rational cooperation. Conflict exists, but it is not inevitable. Institutions, international law, and economic ties can all constrain state behavior and create durable frameworks for peace. The key liberal claim is that realists substantially underestimate how much cooperation is possible – even under anarchy.

Interdependence Liberalism

The oldest strand of liberal IR thought draws on classical economics. Going back to David Ricardo’s theory of comparative advantage and the free-trade advocacy of Richard Cobden and John Bright, the argument is that economic exchange creates mutual dependence among states. When two economies are deeply intertwined, the costs of conflict become prohibitively high.

Robert Keohane and Joseph Nye developed this into the concept of complex interdependence: a world in which multiple channels of contact between societies, the absence of hierarchy among issues, and the diminished role of military force combine to create a fundamentally different kind of international politics than realists describe. Economic ties do not eliminate conflict, but they raise its cost and change its character.

Republican Liberalism

Republican liberalism focuses on domestic political institutions as the key to international peace. The core finding is the democratic peace thesis: democracies virtually never go to war with one another. Michael Doyle’s landmark articles (1983, 1986) traced this insight back to Immanuel Kant’s Perpetual Peace (1795), arguing that democratic institutions – elections, free press, legislative oversight – create checks on leaders that make war less likely. Authoritarian regimes lack these constraints.

This does not mean democracies are pacifist. They fight wars with non-democracies. The claim is narrower and more empirically robust: the internal structure of democratic governance creates a “separate peace” among liberal states.

Neoliberal Institutionalism

Neoliberal institutionalists argue that international organizations and regimes – the UN, WTO, EU, and countless other frameworks – facilitate cooperation by reducing uncertainty, lowering transaction costs, and providing information. States cooperate not out of altruism but because institutions make it rational to do so.

A key concept here is the distinction between absolute gains and relative gains. Realists worry about relative gains: even if both sides benefit from a deal, one may benefit more, shifting the balance of power. Neoliberals argue that states focus on absolute gains – whether they themselves are better off – and that this makes cooperation far more achievable than realists admit. Keohane’s After Hegemony (1984) showed that international cooperation can persist even after the hegemon that created the institutions declines.

The Liberal International Order

The liberal international order (LIO) is not a separate variant of liberalism but a theory of how the post-1945 international system has been organized. G. John Ikenberry argues that the United States, after World War II, built an order based on rules, institutions, and strategic restraint. Unlike empires that rule by force, the U.S.-led order offered legitimacy: other states joined willingly because the institutions gave them a voice and the leading power accepted constraints on its own behavior.

The LIO synthesizes insights from all three liberal strands. From neoliberal institutionalism: rules and organizations stabilize cooperation. From republican liberalism: liberal states are more rule-bound and legitimate. From interdependence liberalism: open markets raise the costs of exit and conflict. Daniel Deudney, Rebecca Lissner, and Ikenberry have explored both the resilience and the vulnerabilities of this order in the face of great-power competition and domestic populism.

Constructivism

Constructivism challenges both realism and liberalism at a foundational level. Rather than taking state interests as given and asking how states pursue them, constructivists ask the prior question: where do state interests come from?

The answer, they argue, is that interests are not fixed by material power or institutional incentives. They are socially constructed – shaped by shared ideas, identities, norms, and historical context. This means the international system is not a fixed structure that determines behavior. It is something states continuously create through their interactions.

Social Construction and Anarchy

Alexander Wendt’s 1992 article “Anarchy Is What States Make of It” is the foundational constructivist text in IR. Wendt’s argument is deceptively simple: anarchy does not inherently produce either conflict or cooperation. What it produces depends on how states interact and perceive each other.

Wendt identifies three cultures of anarchy:

• Hobbesian: States treat each other as existential threats. Survival is at stake in every encounter. (Example: early 20th-century Europe before World War I.)
• Lockean: States are rivals but recognize each other’s sovereignty and right to exist. Competition occurs within limits. (Example: the Cold War – intense rivalry, but within recognized rules.)
• Kantian: States see each other as partners with shared norms and collective identity. (Example: the European Union and NATO, where war among members is virtually unthinkable.)

These cultures are not permanent. They can shift. The move from a Hobbesian to a Lockean or Kantian world is not guaranteed by material forces – it depends on what states do and how they come to understand their relationships. Nicholas Onuf’s World of Our Making (1989) similarly argued that the international system is constituted by rules and social practices, not simply by the distribution of material capabilities.

Norms and Norm Diffusion

Martha Finnemore and Kathryn Sikkink transformed the study of international norms with their work on norm dynamics. Their 1998 article introduced the concept of the norm life cycle: norms emerge through advocacy by “norm entrepreneurs,” reach a tipping point where enough states adopt them, and eventually become internalized as taken-for-granted standards of behavior.

Think of the norm against slavery, or the norm of humanitarian intervention, or the evolving norm around climate responsibility. None of these emerged automatically from material interests. They were constructed through political struggle, persuasion, and social pressure. Finnemore’s National Interests in International Society (1996) showed that international organizations do not merely reflect state preferences – they actively shape what states come to see as their interests. Sikkink’s The Justice Cascade (2011) traced how norms of individual criminal accountability for human rights violations spread across the globe.

Identity and Interest Formation

Constructivists argue that identity is not a fixed attribute but a social product that shapes what states perceive as their interests. A state that sees itself as a “great power” will define its interests differently from one that sees itself as a “middle power” or a “regional leader.” These identities are constructed through interaction, historical narratives, and discourse.

This has concrete analytical implications. Russia’s actions in Ukraine, for instance, are not simply a response to NATO expansion (the realist account). They are shaped by an imperial identity, a great-power self-image, and Putin’s framing of Ukraine as historically Russian. The Western response, in turn, is rooted in norms of sovereignty and self-determination that did not exist as universal principles until they were constructed through decades of diplomatic practice.

Comparing the Traditions

Theory in Action

The point of learning IR theory is not to pick a favorite. It is to develop the ability to analyze real-world events through multiple lenses and understand what each reveals.

Greenland and Tariffs

In early 2026, Trump threatened tariffs against Denmark over Greenland. Each tradition reads this differently:

• Realist lens: This is classic coercive diplomacy – a great power using economic leverage to pursue strategic interests. Greenland’s location matters for Arctic access and military positioning. The tariff threat is a tool of statecraft.
• Liberal lens: The threat undermines the rules-based trade system and strains alliance institutions (Denmark is a NATO ally). It raises questions about whether economic interdependence constrains or empowers coercive behavior.
• Constructivist lens: The episode challenges norms of sovereignty and territorial integrity. The framing of Greenland as a “deal” rather than a sovereign territory reflects a particular identity and worldview – one that other states found alarming precisely because it violated shared understandings about how states relate to each other.

European Leaders Visit Beijing

As U.S. engagement with multilateral institutions declined, European leaders traveled to Beijing to strengthen diplomatic and economic ties.

• Realist lens: This is balancing behavior. As U.S. commitment to European security becomes uncertain, European states hedge by engaging with China – a classic response to shifts in the distribution of power.
• Liberal lens: Economic interdependence drives the visits. European economies depend on trade with China, and leaders seek to maintain market access and supply chain stability through diplomatic engagement.
• Constructivist lens: The visits signal a deeper shift in how European states see themselves. If European identity was previously anchored in the transatlantic relationship, the turn to Beijing may reflect a renegotiation of that identity – a move toward strategic autonomy that changes how Europe defines its interests.

NATO and the 5% Benchmark

NATO’s discussion of raising the defense spending target from 2% to 5% of GDP came as the U.S. signaled it would deprioritize European security.

• Realist lens: Alliance burden-sharing is a perennial realist concern. States free-ride when they can and spend when they must. The 5% target reflects European states responding to the reality that American security guarantees can no longer be taken for granted.
• Liberal lens: This is institutional adaptation. NATO as an institution is adjusting its norms and expectations to new circumstances – exactly what neoliberal institutionalists would predict robust institutions do.
• Constructivist lens: Raising the benchmark signals a transformation in European security identity. States that long defined themselves as post-military, trading powers are reconstituting their identities around defense and strategic capacity. The number itself is a social construction – a signal about commitment and solidarity, not just a spending figure.

Ukraine-Russia

The Russia-Ukraine war is perhaps the most instructive case for multi-theoretical analysis.

• Realist lens: Russia perceived NATO expansion toward its borders as an intolerable security threat. Ukraine was a strategic buffer zone. The invasion reflects the security dilemma at work: Western actions intended to enhance security were perceived as threatening by Moscow. The West miscalculated Russian red lines.
• Liberal lens: Institutions failed – Russia holds a veto at the UN Security Council, rendering collective security inoperable. But economic sanctions imposed real costs on Russia, demonstrating that interdependence can be leveraged as a tool of statecraft even after deterrence fails.
• Constructivist lens: Russia’s invasion was shaped by identity – an imperial narrative, a great-power self-image, and Putin’s framing of Ukraine as historically and culturally Russian. The Western response was rooted in constructed norms of sovereignty and self-determination. The war is not simply a clash of material interests; it is a clash of identities and the norms that follow from them.

No single lens captures the full picture. The skill is knowing when each is most illuminating.

The Framing Experiment

This module includes a live, randomized framing experiment run during class. Students are randomly assigned to read a Hobbesian, Lockean, or neutral description of U.S.–China relations — then answer the same questions about whether cooperation is possible. The results reveal, in students’ own data, that a single paragraph of framing measurably shifts perception. It’s the constructivist insight made visceral.

See the full experiment design, methodology, and illustrative results on the Experiments page.

Further Reading