Realism in International Relations

Introduction

Realism in international relations starts from an uncomfortable observation: states operate in a system with no authority above them, and in such a system security ultimately depends on power. From that single premise, the tradition builds its account of war, diplomacy, alliances, and the limits of cooperation. For most of the twentieth century it was the dominant way of studying world politics, and its vocabulary of anarchy, national interest, and the balance of power is still the language in which rival theories state their objections.

The name itself is an argument. Realists claim to describe politics as it is, not as reformers would like it to be. E.H. Carr aimed the charge of utopianism at the interwar faith in the League of Nations; Hans Morgenthau turned the same instinct into a systematic theory after 1945. Both wrote under the shadow of catastrophic wars, and both believed that wishful thinking about power had helped cause them (Carr, 1939; Morgenthau, 1948).

Treating realism as one doctrine, though, misreads it. It is a family of related arguments rather than a single theory, held together by shared premises and divided over almost everything else (Donnelly, 2000). Classical realists located the drive for power in human nature. Neorealists located it in the structure of the international system. Neoclassical realists split the difference. The common caricature, realism as cynical power worship, survives only at a distance from the actual texts, which counsel restraint far more often than aggression (Williams, 2005).

1. The Intellectual Roots of Realist Thought

No other approach in the field claims a longer pedigree. Realists trace their core ideas through two and a half millennia of political writing, and three figures anchor the genealogy: Thucydides, Machiavelli, and Hobbes. Each supplied a distinct element that modern realism later fused into theory.

1.1 Thucydides and the Logic of the Melian Dialogue

Thucydides, an Athenian general exiled during the Peloponnesian War, wrote its history in the late fifth century BCE. His explanation of the war's origin is the first recognizably realist claim on record: the growth of Athenian power, and the fear it produced in Sparta, made the conflict unavoidable (Thucydides, 1972). War, on this account, follows from shifts in relative power rather than from the wickedness of particular leaders.

The Melian Dialogue distills the logic. When the small island of Melos appealed to justice against Athenian demands, the Athenian envoys replied that justice is only in question between equals in power; otherwise 'the strong do what they have the power to do and the weak accept what they have to accept' (Thucydides, 1972). Melos refused, was besieged, and was destroyed.

Reading Thucydides as a cheerleader for this logic is a mistake. He records the fate of Melos without approval, and the Athenian expedition to Sicily, launched in the same spirit of confident power, ends in ruin. The founding text of realism doubles as a study of hubris, a tension the tradition has never fully shed (Donnelly, 2000).

1.2 Machiavelli and the Autonomy of Politics

Machiavelli's The Prince, written in 1513 and published in 1532, gave realism its ethical provocation. A ruler responsible for the survival of a state, he argued, cannot be bound by the moral rules that govern private life; a prince must learn the ability not to be good and use it as necessity requires (Machiavelli, 1998).

The point is not that cruelty is admirable. It is that political action must be judged by political results. A conscientiously moral ruler whose state is conquered has failed the people who depended on him, whatever his intentions. Statecraft has its own standards, distinct from those of private ethics.

This claim, the autonomy of politics, became the foundation of raison d'etat: the doctrine that the interests of the state justify measures ordinary morality would condemn. Every later realist works within some version of it, including those who tried hardest to limit its reach.

1.3 Hobbes and the International State of Nature

Hobbes supplied the structural argument. In Leviathan, published in 1651 as the English Civil Wars were ending, he asked what life would be like without government and answered with the state of nature: a war 'of every man against every man' in which life is 'solitary, poor, nasty, brutish, and short' (Hobbes, 1996). The cause is not universal wickedness but insecurity. Where no common power keeps all in awe, even moderate men must arm or strike first, because they cannot know their neighbors' intentions.

Individuals escape this condition by submitting to a sovereign. States cannot, since no world sovereign exists, and Hobbes pictured rulers standing in 'the state and posture of gladiators', weapons pointed and eyes fixed on one another. International politics is a permanent state of nature.

He added a qualification later theorists took seriously: anarchy among states is more bearable than anarchy among individuals, because states can still protect the industry of their subjects while they posture abroad. The insight that insecurity flows from the situation rather than from human badness became, three centuries later, the core of structural realism.

2. Core Assumptions of Realism Theory

Modern realism theory compresses this inheritance into a small set of working assumptions. They are simplifications, and realists know it. The claim is that these particular simplifications capture more of international politics than any comparable set.

2.1 States as the Principal Actors

Realist analysis begins with the state. International organizations, multinational firms, and non-governmental movements exist and act, but when security is at stake, decisions rest with states, and among states the great powers matter most (Mearsheimer, 2001). The familiar image is a billiard table: states collide as hard, closed units, and what happens inside them matters less than the forces acting between them.

Two further assumptions ride along. States are treated as unitary, speaking with one voice in the system, and as rational, selecting the strategies that best serve their interests given what they know. Neither is offered as a description of any real government. They are modeling choices, made so that outcomes can be traced to the pressures of the system rather than the quirks of cabinets.

2.2 Anarchy and Self-Help

Anarchy, in this literature, is a technical term. It does not mean chaos. It means the absence of any overarching authority above states: no world government, no international police force, no court whose judgments are enforced against the unwilling. Order exists internationally, but nobody is in charge of it.

Anarchy makes the system one of self-help. A state that cannot protect itself has no guarantee that anyone else will, so survival becomes the precondition for every other goal a state may have (Waltz, 1979). Wealth, ideology, and prestige all presuppose continued existence.

Self-help generates the security dilemma, a term coined by John Herz (1950). Measures one state takes for its own defense, new weapons, alliances, fortified frontiers, appear threatening to its neighbors, who respond in kind, leaving everyone more heavily armed and no one more secure. Insecurity reproduces itself without aggressive intent on either side. The dilemma explains a distinctive realist claim: war can arise between states that both prefer peace.

2.3 The National Interest Defined in Terms of Power

Morgenthau gave realism its compass in one phrase: interest defined in terms of power (Morgenthau, 1948). The formula does two jobs. It marks politics off as a distinct sphere of inquiry, separate from law, ethics, and economics, and it gives the analyst a standing assumption about what statesmen are doing, whatever they say they are doing.

Power, in realist usage, is broader than armies. It is the total of a state's capabilities relative to a specific context of action: economic weight, geography, population, administrative competence, alliance value, and the will to use what one has. A capability that cannot be brought to bear in a given contest is not power in that contest.

The national interest has a hard minimal core, survival and territorial integrity, and a contested penumbra beyond it. Realists also use the concept prescriptively. Foreign policy, they argue, should track interest rather than ideology or sentiment, a standard from which realists have criticized their own governments as often as foreign ones.

3. Classical Realism and Hans Morgenthau

Classical realism is the twentieth-century school that grounded power politics in human nature. Its formative generation wrote against the failures of the interwar order, and several of its leading figures, Morgenthau among them, were European emigres who had watched that order collapse at close range.

3.1 E.H. Carr and the Critique of Utopianism

Carr's The Twenty Years' Crisis, published on the eve of the Second World War, is the school's polemical founding document. Its target was the interwar conviction that reason, public opinion, and the League of Nations could abolish power politics. Carr called this utopianism: a doctrine that mistook aspirations for facts and paid for the error at Munich (Carr, 1939).

His sharpest argument concerned the 'harmony of interests'. Doctrines presented as universal, free trade, collective security, the sanctity of treaties, tend on inspection to serve the states satisfied with the status quo. What looks like impartial principle is often the ideology of the powerful. Carr taught realists to ask who benefits from any allegedly universal rule.

He did not hand realism a clean victory. Pure realism, Carr wrote, offers no ground for purposive action at all; politics needs both utopia and reality. Realism enters as a corrective to wishful thinking, not as a complete political doctrine. That concession sits at the heart of the tradition's self-understanding.

3.2 Morgenthau's Six Principles of Political Realism

Hans Morgenthau turned the corrective into a discipline. Politics Among Nations, first published in 1948, organized the American study of international politics for a generation. The six principles of political realism that open its later editions, added in the second edition of 1954, remain the most cited formulation of the classical position (Morgenthau, 1954).

The principles can be compressed. Politics is governed by objective laws rooted in human nature. Interest defined as power gives the analyst his map. The content of interest varies with historical circumstances, so realism prescribes no fixed policy. Universal moral principles cannot be applied to state action in the abstract; they must be filtered through concrete consequences, which makes prudence the supreme political virtue. No nation is entitled to identify its own cause with the moral order of the universe. And the political sphere is autonomous, judged by political rather than legal or moral criteria.

Beneath the principles lies a claim about people. Morgenthau held that the drive for power, the animus dominandi, is a permanent element of human nature, and that states channel and magnify it. This is what most cleanly separates classical realism from what came after: the cause of power politics sits inside human beings, not in the arrangement of the system.

3.3 Power Politics and Moral Restraint

The fifth principle deserves more attention than it usually gets. A nation convinced that providence is on its side loses the ability to weigh consequences, and in the nuclear age, Morgenthau argued, moral crusades had become existentially dangerous. Realist prudence is not indifference to morality; it is a claim about where morality bites, in outcomes rather than intentions.

Recent scholarship has pressed this point. Williams (2005) reads Hobbes, Rousseau, and Morgenthau as theorists of restraint: skeptical of universal claims, alert to the limits of knowledge, and committed to keeping the exercise of power answerable to judgment. On this reading, the realist tradition is a discipline of limits, and its reduction to crude realpolitik says more about its critics than its texts.

Morgenthau's own conduct fits the reading. He opposed the Vietnam War publicly and early, on the ground that it served no rational conception of the American national interest, and paid a professional price for saying so. Realism, in his hands, argued against a war that liberal anticommunism had argued into being.

4. Neorealism and the Structural Turn

4.1 Waltz and the Third Image

Kenneth Waltz reoriented the tradition twice. In Man, the State and War, he sorted explanations of war into three images, human nature, the internal character of states, and the international system, and argued that the third supplies the permissive cause: wars occur because nothing prevents them (Waltz, 1959).

Twenty years later, Theory of International Politics rebuilt realism on that insight alone (Waltz, 1979). Structure, for Waltz, has three elements: an ordering principle, anarchy; the functional similarity of the units, since anarchy forces states to perform the same core tasks; and the distribution of capabilities across them. Everything else, ideology, regime type, the personality of leaders, drops out of the theory.

Human nature drops out too. States behave in realist ways not because their leaders lust for power but because the system selects for those who attend to it. States that ignore the balance of power are punished, defeated, or absorbed. Waltz was careful about what such a theory can do: it explains recurring patterns, above all the recurrent formation of balances of power, and does not predict the foreign policy of any particular state.

4.2 The Balance of Power and the Security Dilemma

Balancing takes two forms. Internal balancing builds a state's own capabilities through armament and economic mobilization; external balancing recruits allies. Waltz's central prediction is that balances of power recurrently form, whether or not anyone intends them, because unbalanced power is a standing threat that others must answer (Waltz, 1979).

The severity of the competition varies, and Robert Jervis showed what it varies with. When defensive postures can be distinguished from offensive ones, and defense holds the advantage, the security dilemma relaxes and cooperation among adversaries becomes feasible; when offense dominates, spirals sharpen (Jervis, 1978). The variables are partly technological and partly geographic, which is why the intensity of power politics differs across regions and eras.

Anarchy also shapes what states can accept from cooperation. What matters is not only whether both sides gain but who gains more, since today's partner may be tomorrow's rival. This concern with relative gains is a standing brake on cooperation that realists accuse liberal theory of underestimating.

4.3 Defensive and Offensive Realism

Structural realists divide over how much power a state should want. Waltz's answer is an appropriate amount: security is the end, power the means, and an excess of it frightens others into countervailing coalitions. States, on this defensive reading, are security maximizers that punish overreach.

John Mearsheimer draws a darker inference from the same premises. Because intentions can never be verified and capabilities can, states must assume the worst, and the safest position under uncertainty is primacy, at the limit regional hegemony (Mearsheimer, 2001). Great powers maximize power not from greed but from fear. He calls the result tragedy, since even states that want only security are driven into rivalry, and he applies the logic directly to the rise of China and the American response.

The dispute matters in practice. Defensive realism implies that restrained, status-quo policies are usually rational; offensive realism implies that great-power competition is built in. Both descend from Waltz's structure, which shows how far shared premises can leave conclusions open.

4.4 Polarity and the Question of Stability

Because structure is defined partly by the distribution of capabilities, realists sort systems by their poles: multipolar systems with several great powers, like Europe before 1945; the bipolar Cold War; the unipolar American position after 1991.

Which arrangement is most stable is disputed within the school. Waltz argued for bipolarity: two poles watch each other directly, miscalculation is harder, and allies cannot drag the system into war, an argument the long Cold War peace seemed to support (Waltz, 1979). Wohlforth (1999) argued that unipolarity is more stable still, since counterbalancing a truly dominant power is futile and few will attempt it. Mearsheimer (2001) counts multipolarity most dangerous, especially when one power bids for hegemony, because responsibility for balancing blurs and buck-passing invites miscalculation.

That realists disagree here is itself informative. Polarity constrains outcomes without determining them, and the school's internal debates over unipolar durability and China's rise are conducted with the same concepts it built for earlier eras.

5. Neoclassical Realism and the Global Turn

Structural theory brought rigor at the price of silence about particular states. Two countries facing similar pressures often respond differently, and Waltz's theory cannot say why. Neoclassical realism, named by Gideon Rose (1998), reopens the state to address this: systemic incentives remain the starting point, but they are filtered through intervening variables at the domestic level, including leaders' perceptions of power, the state's capacity to extract resources from society, elite consensus, and strategic culture.

The move restores what classical realists knew, that statesmen act on judgments rather than on objective distributions, while keeping the structural frame. It yields a theory of foreign policy rather than of international outcomes, and it explains cases that embarrass pure structuralism: underbalancing against rising threats, overextension beyond any rational interest.

The same flexibility has made neoclassical realism the tradition's opening toward global IR, the movement arguing that the discipline universalizes Western experience. Foulon and Meibauer (2020) show that the charge lands hardest on structural realism's one-size-fits-all logic, and that neoclassical realism's contextual variables can accommodate non-Western histories, concepts, and cases. Mapping 149 neoclassical realist publications by 96 scholars, they find knowledge production drifting away from North America toward Europe and, more slowly, Asia and Africa. Realism, on this evidence, is a living research program rather than a Cold War artifact.

6. Realism versus Liberalism and Other Challenges

6.1 The Liberal Challenge

The realism vs liberalism debate is the discipline's oldest argument, and it is narrower than the textbook version suggests. Sophisticated liberals concede anarchy and state rationality. Robert Keohane's institutionalism accepts realist premises and then argues that institutions let self-interested states cooperate anyway, by lengthening time horizons, supplying information, and making commitments verifiable (Keohane, 1984). The disagreement concerns whether anarchy's effects can be mitigated, not whether anarchy exists.

The liberal exhibit realists find hardest to dismiss is the democratic peace. Michael Doyle, reviving Kant, documented that liberal democracies almost never fight one another, a regularity that has held up statistically (Doyle, 1983). If regime type governs war and peace, the realist decision to ignore domestic politics looks like an error, and the billiard-ball model breaks.

Realists respond on the evidence and the mechanism. Democracies were rare until recently; many were allied against common threats, so shared enemies rather than shared norms may explain the peace; and the peace deepened under American hegemony, which realists count as a power variable. The exchange remains unresolved, and it is conducted, notably, in realist vocabulary: alliances, threats, hegemony.

6.2 The Constructivist Objection

Alexander Wendt aimed at a deeper premise: 'anarchy is what states make of it' (Wendt, 1992). Anarchy, he argued, has no single logic. Self-help is not given by the absence of world government; it is one culture of anarchy among several, produced and reproduced through interaction. States that treat each other as rivals will generate a rivalrous system, but enemies can become acquaintances and even friends, as Western Europe's transformation after 1945 suggests.

The disagreement concerns what kind of fact anarchy is. Realists treat it as a material condition whose pressures operate regardless of belief. Constructivists treat it as an institution, and institutions can change. If they are right, the security dilemma is a learned practice that can, with difficulty, be unlearned, and realism's timeless wisdom has a history and possibly an expiry date.

6.3 Prediction, Change, and the Standing Criticisms

The end of the Cold War is the tradition's hardest case. No realist theory anticipated that a superpower would abandon its empire and dissolve itself without war. The retreat was driven by domestic collapse and by new thinking in the Soviet leadership, exactly the variables structural realism had excluded. Realists reply that retrenchment under relative decline is what their theory expects, and that a theory of recurring patterns was never in the business of point predictions. The reply is fair as far as it goes; it also concedes how much of world politics the theory leaves out.

Three further criticisms recur. State-centrism undercounts transnational actors, from multinational firms to insurgent networks, whose behavior is not reducible to state interests. A status-quo bias treats the system of territorial states, a form dating roughly from 1648, as permanent, leaving realism poorly placed to theorize integration of the European kind. And the theory risks self-fulfillment: a government advised to treat all others as potential aggressors will act in ways that make them so.

Realists have answers of varying strength to each. Donnelly's (2000) verdict is close to the mark: realism is best treated not as a finished theory but as a set of recurring cautions about power, fear, and the limits of reform, cautions that other theories ignore at their cost.

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Conclusion

Realism endures because its questions come first. Who holds power, who fears whom, and what happens when the balance shifts are questions every rival theory must eventually answer, usually in terms realists coined. Liberalism's institutions were built by powerful states; constructivism's cultures of anarchy include the Hobbesian one from which the alternatives must escape. Realism sets the agenda even where it loses the argument.

The tradition is also less unified, and less cynical, than its reputation. Classical realism, neorealism, and neoclassical realism disagree about the sources of power politics, the amount of power worth wanting, and the stability of every configuration of the system. What they share is a discipline: take power seriously, distrust universal claims, weigh consequences rather than intentions. Thucydides recorded Melos and Sicily in the same book; Morgenthau wrote the six principles and opposed Vietnam.

Great-power rivalry has returned, and with it realism's audience. Whether the tradition's next contribution comes from offensive realism's structural pessimism or from neoclassical realism's engagement with a wider world is genuinely open. Its continuing use, either way, is diagnostic: realism in international relations remains the discipline of asking what power permits before asking what justice demands.

References

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