1.1 Classical realism

Classical realism emerged after World War II as a response to idealism's failures. It explains international politics through power, self-interest, and conflict between states in an anarchic system, drawing on thinkers like Thucydides, Machiavelli, and Hobbes.

The theory rests on a few core assumptions: power is the central currency of international politics, the international system is anarchic (no authority above states), states act as rational actors, and national interest always comes first. Classical realism directly critiques idealism's optimism about cooperation, insisting that power politics shape state behavior far more than good intentions or international law.

Origins of classical realism

Classical realism became the dominant IR theory after World War II, but its intellectual roots stretch back thousands of years. The theory developed specifically because idealism and liberalism had failed to prevent two devastating world wars. Where idealists believed institutions and cooperation could keep the peace, classical realists argued that international politics is fundamentally driven by power, self-interest, and unavoidable conflict between states operating without any higher authority to keep them in check.

Key thinkers in classical realism

Thucydides

Thucydides was an ancient Greek historian who wrote History of the Peloponnesian War, documenting the conflict between Athens and Sparta in the 5th century BCE. His analysis focused on how fear, honor, and interest drove the behavior of these rival city-states.

His most famous passage for IR theory is the Melian Dialogue, where Athenian envoys tell the neutral island of Melos that "the strong do what they can and the weak suffer what they must." The Melians appealed to justice and fairness; Athens conquered them anyway. This exchange captures the core realist claim that power, not morality, determines outcomes in an anarchic system.

Machiavelli

Niccolò Machiavelli was an Italian Renaissance political thinker best known for The Prince (1532). He advocated a pragmatic, amoral approach to statecraft, arguing that effective rulers must prioritize power and the survival of the state above all else.

His key contribution to realist thought is the idea that a ruler must be willing to act immorally when the state's security demands it. Politics, for Machiavelli, operates by its own rules, and leaders who cling to moral ideals at the expense of practical necessity will lose power.

Hobbes

Thomas Hobbes, the English philosopher who wrote Leviathan (1651), described humanity's natural condition as a "war of all against all." Without a sovereign authority to impose order, individuals are driven by self-interest and the fear of violent death.

Realists draw a direct parallel between Hobbes's state of nature and the international system. Just as individuals in Hobbes's world need a strong sovereign to prevent chaos, states in an anarchic international system face constant insecurity because there is no global sovereign to enforce rules or protect them. This analogy is foundational: the international system is a state of nature, with each state left to fend for itself.

Morgenthau

Hans Morgenthau, a German-American political scientist, is widely considered the father of classical realism in IR theory. His 1948 book Politics Among Nations became the foundational text of the tradition.

Morgenthau developed six principles of political realism (detailed below) that systematized classical realist thought. His central argument was that international politics, like all politics, is a struggle for power rooted in human nature. He distinguished classical realism from purely cynical power worship by insisting that statesmen must still exercise prudence, carefully weighing the consequences of their actions, even if universal morality can't guide foreign policy directly.

Core assumptions of classical realism

Centrality of power

Power is the fundamental currency of international relations. States constantly seek to maximize their power relative to others, and the distribution of power among states is what determines international outcomes.

• Military and economic capabilities are the most important sources of power, enabling states to coerce, deter, or influence others.
• The balance of power plays a crucial stabilizing role. When power is roughly balanced, no single state can dominate, which reduces the likelihood of major war.
• For classical realists, understanding who has power and how much tells you more about international politics than any treaty or institution.

Anarchy in the international system

Anarchy in IR doesn't mean chaos or disorder. It means there is no authority above sovereign states to enforce rules, settle disputes, or punish aggressors. This is the structural condition that shapes everything else.

• Without a global government, states must rely on self-help to ensure their survival. No one else will protect them.
• Anarchy creates persistent uncertainty. You can never be fully sure of another state's intentions, which pushes states to prioritize security above other goals.
• This insecurity is structural, not a choice. Even well-intentioned states face pressure to arm themselves and compete.

States as rational actors

Classical realism treats states as the primary actors in international relations and assumes they behave as rational, unitary actors pursuing their interests.

• Foreign policy decisions are understood as calculations of costs and benefits, with states seeking to maximize power and minimize threats.
• While individual leaders and domestic politics obviously exist, classical realists argue that the pressures of the anarchic system constrain state behavior far more than internal factors do.
• "Rational" here doesn't mean states always make perfect decisions. It means they act purposefully based on their assessment of the situation.

Primacy of national interest

The national interest, defined primarily in terms of power and security, is the guiding principle of state behavior.

• States prioritize their own survival and security over moral or ideological commitments. A state may talk about human rights or democracy, but when those values conflict with security, security wins.
• Cooperation between states is possible, but only when it serves each state's national interest. Alliances form not out of friendship but out of shared threats.
• This doesn't mean morality is irrelevant to individual leaders. It means that in the anarchic international system, moral aspirations consistently take a back seat to power realities.

Classical realism vs. idealism

Classical realism emerged as a direct critique of idealism (sometimes called liberal internationalism), which dominated IR thinking during the interwar period (1919–1939). The contrast between the two schools is sharp:

• Idealists believed international cooperation, collective security arrangements, and the rule of law could prevent war. They championed institutions like the League of Nations as mechanisms for peaceful dispute resolution.
• Classical realists argued this was dangerously naive. The League failed to stop Japanese aggression in Manchuria (1931), Italy's invasion of Ethiopia (1935), or Hitler's expansionism, precisely because it had no power to enforce its decisions against states that chose to ignore it.
• For realists, idealism's fatal flaw was ignoring the reality that states act out of self-interest and that power, not law, determines outcomes. The catastrophe of World War II seemed to vindicate the realist position.

E.H. Carr's The Twenty Years' Crisis (1939) was an early and influential statement of this critique. Carr argued that idealists confused how they wished the world worked with how it actually worked, and that ignoring power realities made conflict more likely, not less.

Morgenthau's six principles of political realism

These six principles, laid out in Politics Among Nations, form the theoretical backbone of classical realism:

1. Politics is governed by objective laws rooted in human nature. Human nature is characterized by self-interest and the desire for power, and these drives shape political behavior in predictable ways. A theory of politics can therefore be built on these regularities.
2. National interest is defined in terms of power. This concept allows us to analyze foreign policy rationally, regardless of the stated motives of decision-makers. What leaders say matters less than what the power calculus demands.
3. Power is a universally valid category, but its content changes. What counts as power varies across time and context (military strength mattered differently in 1648 than in 1948), but the concept itself is constant.
4. Universal moral principles cannot be applied to state action in the abstract. Statesmen must weigh the political consequences of their decisions, not simply follow moral rules. Prudence is the supreme virtue in politics.
5. No nation's moral aspirations equal universal moral law. Every state tends to dress up its interests in moral language, but confusing one nation's values with universal truth is both intellectually dishonest and politically dangerous.
6. The political sphere is autonomous. Politics operates by its own logic, distinct from economics, ethics, or law. Analyzing international relations requires thinking in terms of interest defined as power, not importing criteria from other domains.

Critique of classical realism

Neglect of non-state actors

Classical realism treats states as the only actors that really matter in international politics. Critics point out that this ignores the growing influence of non-state actors such as international organizations (the UN, WTO), transnational corporations, NGOs, and terrorist networks.

• Phenomena like globalization, transnational terrorism, and global financial crises are difficult to explain through a purely state-centric lens.
• The theory was developed in an era when states dominated international politics more completely than they do today, which may limit its explanatory power for contemporary issues.

Overemphasis on power and conflict

Critics argue that classical realism's focus on power and force leads to an overly pessimistic view of international relations.

• The theory struggles to explain sustained cooperation, such as the European Union's decades of integration, or the role of international institutions in managing trade disputes and arms control.
• By treating diplomacy, international law, and economic interdependence as secondary to raw power, classical realism may underestimate the mechanisms that actually prevent conflict in many cases.
• Some critics also challenge the theory's foundation in a fixed, power-seeking human nature, arguing that this is more of a philosophical assumption than an empirically proven claim. Constructivists, for instance, argue that interests and identities are socially constructed, not given by nature.

Legacy of classical realism

Influence on neorealism

Classical realism laid the groundwork for neorealism (structural realism), developed by Kenneth Waltz in Theory of International Politics (1979). Waltz accepted many classical realist premises but shifted the explanatory focus in a significant way.

• Where classical realists rooted state behavior in human nature (the innate drive for power), Waltz argued that the structure of the international system itself forces states to behave the way they do, regardless of human nature or the character of individual leaders.
• Neorealism refined and systematized classical realist insights while addressing criticisms about the theory's reliance on vague claims about human nature.
• The move from classical realism to neorealism represents a shift from a "human nature" explanation to a "systemic" explanation of the same basic patterns. This is the key distinction you'll want to keep straight as you move into Unit 1.2.

Continued relevance in IR theory

Despite challenges from liberalism, constructivism, and other approaches, classical realism remains widely studied and influential.

• Its emphasis on power, self-interest, and competition resonates strongly during periods of great power rivalry or international crisis. Analysts frequently return to realist frameworks when explaining events like Russia's invasion of Ukraine or U.S.-China strategic competition.
• Classical realism provides a useful baseline for analyzing great power behavior and the dynamics of international competition, even in a world that has grown more complex and interdependent.
• The tradition also offers a valuable corrective to overly optimistic theories: it reminds us that institutions and norms can fail when they aren't backed by power.