Realism, Structural Realism, Liberalism, and Neoliberalism in International Relations

The strong do what they can, the weak suffer what they must.


The story of the discipline of International Relations is often told in terms of the four Great Debates. The first great debate was the realist-liberal schism, which began in the late 1930s and dominated the early 1940s. The question scholars sought to resolve: How could they account for Manchuria, Abyssinia, the failure of the League of Nations, Munich, and the outbreak of the war?

The words realism and liberalism, in this context, aren’t defined as common usage would have it. You can be a Marxist realist or a right-wing liberal, and there have been prominent examples of both.


Realism, sometimes called Realpolitik, is the oldest theory of international relations. Definitions vary, but all involve the following precepts:

  1. The fundamental unit of analysis in international relations is the state.
  2. Broadly speaking, states pursue their aims rationally.
  3. There is no such thing as international government. This means the international realm is anarchic, and the nature of this anarchy is Hobbesian: “During the time men live without a common power to keep them all in awe, they are in that condition which is called war; and such a war as is of every man against every man.”
  4. The aims of states are selfish, because states are comprised of men, who are wicked. (Machiavelli: “It must be taken for granted that all men are wicked, and that they will always give vent to the malignity that is in their minds when opportunity offers.”)
  5. Within states, human selfishness is constrained by governments. In international relations, because there is no government, the worst aspects of human nature are expressed.
  6. Thus conflict and war are intrinsic to human nature.
  7. State behavior is best described as a ceaseless quest for power and security. The maximization of power in pursuit of the national interest is the sole imperative of the international realm.
  8. International relations is a zero-sum game. One state’s gain in power and security is the other state’s loss.
  9. Whether it is a democracy, an oligarchy, or a tyranny, a state will pursue the same aim: maximizing its power and security.
  10. “States are unitary actors with a single motive—the wish to survive.”[1]Kenneth Waltz.Survival is assured when a state has relative power over other states.
  11. Because the international system is a uniquely anarchic domain, it may and should be analyzed apart from any social or economic development within or across societies.
  12. In analyzing international relations, we should treat the interior of the state as a black box. States and their quest for power and security are the only things that matter; they interact with each other like billiard balls.
  13. History is cyclical. Change for the better is not possible.

Those are descriptions of the international realm, not prescriptions. But from this description, realist policy prescriptions follow:

  1. Statesmen should seek mitigate and manage conflict rather than pursue such abstract ideals as “democracy promotion” or “ridding the world of tyranny.”
  2. As John Mearsheimer puts it: “States should maximize power, and their ultimate goal should be hegemony, because that is the best way to guarantee survival.”
  3. Ethical considerations should always give way to raison d’état. “Realism maintains,” Hans Morgethau wrote, “that universal moral principles cannot be applied to the actions of states.”

There are various shades and flavors of realism. Radical realists deny that anything but the pursuit of power matters in international politics; strong realists accept that other factors may determine state behavior, but they emphasize the primacy of the pursuit of power; weak realists accept the realist position in some cases, but allow for the possibility that state behavior might sometimes be better explained in other ways. No matter the solution, however, the realist emphasizes the primacy of the state and its ceaseless quest for security and power.

The seminal realist texts—and the books that created the academic discipline of IR theory—are E. H. Carr’s The Twenty Years’ Crisis, published in 1939, and Hans Morgenthau’s Politics Among Nations, published in 1948. Both evaluated the crisis in the interwar years that led to the Second World War. Both sought to correct what the authors viewed as profound and dangerous liberal misunderstandings about the nature of international politics.

These misunderstandings, they argued, led to the fatal collapse of the interwar order. “The breakdown of the 1930s,” wrote Carr, “involved the bankruptcy of the postulates on which it was based.” Carr was, by the way, a Marxist, although not a radical one, and he supported the policy of appeasement. There was no incompatibility in these views. “Collective security” and “international solidarity,” he argued, were the “disguises of selfish vested interests.” Established powers must appreciate that rising powers will always seek to unseat them. A sound policy would “oscillate between the apparently opposite poles of force and appeasement.


Structural realism, or neorealism, of whom Kenneth Waltz is the best-known exponent, is a refinement of the realist thesis:

  1. The structure of the international system (as opposed to the states it comprises) is the fundamental object of analysis.
  2. We can predict the behavior of states from the structure of the international realm, for example, its unipolarity or multipolarity.
  3. This structure “constrains [states] from taking certain actions while propelling them toward others,” giving rise to a “striking sameness in the quality of international life through the millennia,” as Waltz wrote.
  4. Unipolar, bipolar, or multipolar worlds each have their own logic.
  5. Sovereign states can live in peace for long periods so long as there is a stable balance of power. But when that balance breaks down, war follows.
  6. States are concerned with relative gains; that is to say, they assess their status only vis-à-vis their rivals.
  7. States do not bandwagon, they balance. In domestic politics, a bandwagoner attempts to maximize his power by siding with a stronger party. (J.D. Vance, for example, is a bandwagoner.) But in international relations, a stronger party is always a threat. Therefore, whenever a strong state arises, other powers will form alliances to balance it.

Structural realists would argue that this balancing imperative explains why the United States formed an alliance with the Soviet Union to counter Nazi Germany. Such an alliance, they would point out, can’t be explained by the two states’ ideologies: The United States, after all, was virulently opposed to Bolshevism and vice-versa.

The structural realist would deny that the United States fought the Cold War for ideological reasons. To the contrary, they would argue, the Cold War was structurally overdetermined; the Soviet Union’s power ensured the United States would seek to balance it. (The ideological justifications offered for fighting the Cold War would be, in this account, something like false consciousness.)

The theory likewise purports to explain the Sino-Soviet split and the US rapprochement with China. If you’re a structural realist—I caricature slightly, but this is basically how they see things—you don’t need to spend time wondering why, exactly, Mao believed Khrushchev a revisionist traitor; you don’t need to bother yourself with tedium like learning Russian and Chinese. What happens inside states doesn’t really matter, and neither does the ideology statesmen claim to espouse. What mattered was Russia’s growing cooperation with India, and particularly Russia’s position on the Sino-Indian war.[2]The realist theory has unusually good explanatory power here. Those who saw the communist world as monolithic, and above all ideological, failed to predict or capitalize upon the Sino-Soviet split. … Continue reading

Structural realists generally argue that a unipolar world, such as the one that emerged in the wake of the Cold War, is prone to instability—although a unipolar system with one major power can be stable if the hegemon is powerful enough to keep it that way. The impulse to balance, however, ensures that new powers will emerge, so such a system is unlikely to be durable. Structural realists are fond of bipolar systems, which they believe to be the most stable, and horrified by multipolar systems, which they believe inherently unstable.

In addition to the prescriptions above, therefore, structural realists advise:

A balance of power being the most stable international configuration, statesmen should seek to create them.


The theory of international relations to which the realists were responding is liberalism, sometimes called pluralism, or idealism, or contemptuously, Utopianism. In essence, liberals believe that an intelligent and rational system of international organization can put an end to war, or greatly reduce its likelihood. Its most famous exponent, Immanuel Kant, made this case in Perpetual Peace.

Normal Angell was another prominent liberal theorist; in 1909, he published The Great Illusion, arguing that economic interdependence had made war obsolete. Liberals, like realists, come in many varieties, but most agree on the following:

  1. War is in no one’s interest and no one rational would want it.
  2. Peace, not war, is the normal state of affairs. As Kant wrote, peace can even be perpetual. Wars are the product of corrupt institutions, bad leadership, and misunderstandings.
  3. Corrupt figures in undemocratic governments wage wars for their own vested interests, but democratic governments are peace-loving, because this is the natural human state.
  4. The international realm is not completely anarchic. The principles of legitimacy that apply to domestic politics also apply in international affairs.
  5. Human beings can apply rationality to international relations to establish systems, structures, and organizations for the benefit of all.
  6. Everyone, and every state, benefits from free trade and the free exchange of of ideas.
  7. States are not the only unit of analysis in international relations: To describe and predict international relations we must look at things both smaller and larger: the role of the individual, in the first case, and the role of the global economy and transnational organizations in the second.
  8. International relations need not be a zero sum game.
  9. Public opinion is a constructive force. If diplomacy is open to public scrutiny, agreements will be sensible and fair.
  10. This only works, however, if people have control over their governments and access to uncensored information. Therefore a state system comprised of liberal democracies is best suited to securing international peace.
  11. Thus it matters quite a bit what happens inside the state: autocratic, authoritarian, and militaristic states are more likely to go to war. The projection of liberal-democratic principles into the international realm provides the best prospect for a peaceful world order.
  12. Economic interdependence among states reduces their proclivity to war with one another. The spirit of war and the spirit of commerce are incompatible. “Trade,” wrote Kant, serves to “increase the wealth and power of the peace-loving, productive sections of the population at the expense of the war-orientated aristocracy,” and brings “men of different nations into constant contact with one another,” which makes “clear to all of them their fundamental community of interests.”
  13. States are concerned with absolute gains: They assess their welfare independent of their rivals.
  14. History is progressive, linear, and headed in a better direction. As Francis Fukuyama put it, “There is a fundamental process at work that dictates a common evolutionary pattern for all human societies—in short, something like a Universal History of mankind in the direction of liberal democracy.”

The liberal school dominated the nascent field of international relations in the wake of the Great War. The enormity of the catastrophe that had befallen Europe led many to argue that the old assumptions and prescriptions of power politics had been completely discredited. Total mechanized warfare between industrial states was, they held, a horror so great that the international system must be completely reconceived.

Among the most prominent exponents of liberalism was the English classicist Sir Alfred Zimmern, who argued that the classical idea of a balance of power must be replaced by a system of collective security governed by the rule of law. He drafted the blueprint for what came to be called the League of Nations.

Central to liberalism is the Whiggish, nineteenth-century idea of progress: the belief that mankind advances by means of greater understanding and rational argument; critical, too, are nineteenth century ideas about liberty and free trade. John Stuart Mill, for example, claimed that free trade was the means to bring about the end of war: “It is commerce which is rapidly rendering war obsolete, by strengthening and multiplying the personal interests which act in natural opposition to it.”

Contra the realists, liberals see the character of states—particularly, the distinction between democracies and autocracies—as analytically central. Democracies, they argue, do not and will not go to war with each other. They likewise see economic interdependence as a disincentive to war, an idea Thomas Friedman expressed with his Golden Arches Theory of Conflict Prevention. Similar theses were advanced by Montesquieu, Adam Smith, and Richard Cobden.

Liberals argued that the First World War broke out because statesmen had embraced the obsolete precepts of a balance of power and an alliance system. This way of thinking was given enormous support in the interwar years by Woodrow Wilson. If you’re a liberal, Wilson’s peace program is exactly how you’d recommend the international system be configured:

  • Secret diplomacy to be replaced with “open covenants, openly arrived at.”
  • Freedom of navigation on the seas;
  • The removal of barriers to free trade;
  • Armaments to be reduced to “the lowest point consistent with domestic safety;”
  • Colonial and territorial claims to be settled in light of the principle of self-determination of peoples;
  • A general association of nations offers mutual guarantees of the political independence and territorial integrity of great and small nations alike;
  • Liberal democracy should be encouraged as a form of governance;
  • International relations would be regulated by a common international law …

Zimmern, whose belief in the inevitable progress of the human race was undimmed by the paucity of evidence for the proposition, advocated for the outlawing of war, by international treaty.

Here’s an amusing article in the New Yorker arguing that contrary to everything you might think, the Kellogg-Briand pact did successfully outlaw war. It’s also a nice survey of the major debates in IR theory. It also illustrates why I gave up IR theory as a bad job: If you can get tenure by arguing the Kellogg-Briand pact was a success, your discipline is preposterous.


Neoliberals, like realists, begin with the assumption that the state is the fundamental unit of analysis. But where realists conclude this means the natural state of affairs among states is conflict, neoliberals argue that conflict is not in the interest of states, and the natural state of affairs is cooperation. Thus, even in an anarchic state system, states may be expected to work cooperatively to achieve collective interests through, for example, trade agreements and international organizations.

Neoliberal institutionalists place a great premium on creating international institutions to ensure cooperation on a range of issues, from, for example, the environment to money laundering.

For liberal theorists, the interwar years were a catastrophic blow. The growth of fascist and Nazi dictatorships in Italy, Germany, and Spain and the rise of authoritarianism throughout the new states of Central and Eastern Europe that had been brought into existence with the Paris Peace Conference dashed hopes for the spread of democracy. The Wall Street Crash of 1929 gave rise to the return of protectionist barriers. The US Senate failed to ratify the Covenant of the League of Nations. Lacking the power of the strongest state in the system, the League was helpless to restrain the aggressive impulses of its member states. Interdependence manifestly failed to lead to peaceful cooperation.

By the outbreak of the Second World War, the realist school was ascendent. Liberals, they argued, had gravely erred in their belief that the international realm could be tamed by international law. The notions of collective security and a non-zero sum game in international relations had been and would always be dangerous fantasies. No such system could ever supersede national self-interest. Indeed, attempts to bring about fundamental change in the international system only compound its inherent dangers.

At the end of the Second World War, realists clearly had the better of the argument. Realism dominated academic IR theory throughout the 1950s and 60s. By the 1970s, however, liberalism returned as an important theoretical construct: Liberal thinkers pointed to trends not amenable to realist analysis, such as the growth of transnational organizations, regional integration, and growing economic interdependence.

What’s more, liberal ideals have been embedded in UN charter and such major security alliances as NATO. The preamble to the NATO treaty is a declaration of liberal ideas:

The parties to this Treaty affirm their faith in the purposes and principles of the Charter of the United Nations and their desire to live in peace with all peoples and governments. They are determined to safeguard the freedom, common heritage and civilization of their peoples, founded on the principles of democracy, individual liberty and the rule of law. They seek to promote stability and well-being in the North Atlantic area. They are resolved to unite their efforts for collective defense and for the preservation of peace and security.

While the UN has only arguably been more successful than the League of Nations in ensuring peace, NATO has been exceptionally successful. This is hard to explain in strictly realist terms. The European Union is impossible to explain in realist terms. The demise of the Soviet Union and the globalization of the world economy greatly enhanced greatly enhanced the influence of liberal theories in the academy and presaged the renaissance of liberal thinking in the Western world. When Francis Fukuyama proclaimed the end of history, he was expressing an essentially liberal view.

But the theory took another hit in the wake of September 11. It has been languishing ever since.

With Russia’s invasion of Ukraine, a number of scholars who identify as realists are saying, “We told you so.” Stephen Walt writes, “We are back in a world that realism explains best, one where great powers compete for power and influence and others adapt as best they can.”

John J. Mearsheimer goes further, writing that the Ukraine crisis is the West’s faultThe taproot of the trouble is NATO enlargement, the central element of a larger strategy to move Ukraine out of Russia’s orbit and integrate it into the West.” Realists, he argues,

opposed expansion, in the belief that a declining great power with an aging population and a one-dimensional economy did not in fact need to be contained. And they feared that enlargement would only give Moscow an incentive to cause trouble in eastern Europe.

The problem is that there’s no special sense in which this is a realist argument. First, the premises are false. No matter how old Russia’s population or unidimensional its economy, it clearly does need to be contained. If a revisionist power is expanding its borders and shedding an enormous amount of blood in the process, it requires containment. (Mearsheimer, who wrote the article in 2014, also argued Russia wouldn’t invade the rest of Ukraine because that would be both irrational and impossible. The falsification of this premise has not caused him to revisit his conclusion.)

But even if we imagine his premises correct, one could equally well argue that from a realist perspective, the failure of the West was not enlarging NATO enough. Certainly, realists would not have naively assumed, as Germany purported to do, that trading with Russia would temper its quest for power and security.

The realist precepts are so general that they may be used to support several contradictory positions at once. I can see no clear sense in which realism would militate against NATO expansion. This was simply Mearsheimer’s preference, which he called realism, perhaps to make it sound as if it rested upon a real theoretical substrate.

If you look at the literature, you’ll find that many people claim to be a realists, but few agree what it practically entails. Here, Henrik Larson argues that from a realist perspective, we should be more aggressive about defeating Ukraine. Here’s another paper arguing that from a realist perspective, the Ukraine crisis is a positive accomplishment for the West, not a policy failure. Mearsheimer, according to this paper, just doesn’t understand realism:

It has been widely established by the realist scholars that both the United States and the European Union are acting in their policies concerning the former Soviet space in accordance with the realist principles despite the fact that it is not directly acknowledged in the narratives of their leaders.

Here’s another article arguing that realism doesn’t mean what Mearsheimer thinks it does:

The Soviet Union lost the Cold War decisively. Its empire fell into pieces, its regional alliance disappeared, and most of its former allies joined NATO. Russia lost, and the Western alliance won. Given this, it is not NATO’s responsibility to protect Russian state security interests. It is Russia’s responsibility to give a wide berth to NATO, recognizing—as every realist should—that the strong do what they will, the weak do what they must …

So I leave it to my readers as an exercise: Is realism a coherent theory? Does it accurately describe the world? What about liberalism?

And do either of these theories suggest principles of statecraft that might have been applied by Western statesmen to prevent the war in Ukraine?


📣 Join our members-only discussion forum, here, to debate these questions. We’ll publish the best comments here in the magazine.

Claire Berlinski is the editor of the Cosmopolitan Globalist.


1 Kenneth Waltz.
2 The realist theory has unusually good explanatory power here. Those who saw the communist world as monolithic, and above all ideological, failed to predict or capitalize upon the Sino-Soviet split. Realists—and Kissinger was a realist—instinctively grasped that the US was now in a position to balance against the Soviet Union, and that China would be receptive to this despite its ideological commitments.

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