Core Assumptions of Realism in IR

Why do states arm themselves even when no one has declared war? Why does cooperation between nations so often collapse into suspicion and competition? For more than two thousand years, one theory has offered a consistent answer: realism. As one of the oldest and most influential frameworks in international relations, realism argues that global politics is fundamentally a struggle for power among self-interested states. Understanding its core assumptions is the first step to grasping how diplomats, generals, and policymakers actually think about the world.

What is realism in international relations? 🔗

Realism is a theoretical framework that focuses on the competitive and conflictual nature of global politics. It places the state at the centre of analysis and argues that a state’s primary concern is survival, which is best secured through power. Realists are skeptical of grand moral projects and optimistic promises of permanent peace. Instead, they see international politics as a recurring contest shaped by enduring features of human and state behaviour.

The intellectual roots of realism stretch back to Thucydides, Niccolò Machiavelli, and Thomas Hobbes. In modern times, the theory was systematised by scholars like Hans Morgenthau and later reformulated by Kenneth Waltz. While their explanations differ, they share a common set of assumptions about how the world works. Let us break these down one by one.

The state is the primary actor 🔗

The first and most fundamental assumption of realism is that the sovereign state is the principal actor in international relations. Other bodies certainly exist, such as individuals, corporations, and international organisations, but realists argue their power is limited compared to that of states. According to the realist view, nation-states are the main characters in the unfolding story of global politics.

This focus on the state is closely tied to the idea of sovereignty. A sovereign state recognises no higher authority over its own territory. In international affairs, this means each state is responsible for itself. When a country like India negotiates a trade deal, defends its borders, or signs a treaty, it acts as a single, recognised unit on the global stage.

The state as a unitary actor 🔗

Realists also treat the state as a unitary actor. This means that despite internal disagreements among political parties, bureaucrats, or interest groups, the state ultimately speaks and acts with one voice in foreign affairs, especially during times of war or crisis. National interests, rather than domestic squabbles, are seen as the driving force. When a nation faces an external threat, internal divisions tend to give way to a unified response aimed at protecting the country.

State survival is the supreme goal 🔗

If the state is the main actor, then its most important objective is survival. Realists argue that before a state can pursue any other goal, whether economic growth, cultural influence, or ideological aims, it must first ensure its own continued existence. Survival is the prerequisite for everything else.

This emphasis on survival explains a great deal about state behaviour. It is why nations invest heavily in defence, build alliances, and remain cautious about the intentions of their neighbours. As the structural realist Kenneth Waltz argued, in a world where security is not guaranteed, whether states live, prosper, or die depends largely on their own efforts.

Anarchy defines the international system 🔗

Perhaps the most important structural assumption of realism is that the international system is anarchic. This does not mean chaos or constant violence. It means that there is no overarching authority, no world government, sitting above states to enforce rules and protect them. Within a country, a government and police force maintain order. Between countries, no such global enforcer exists.

For the neorealist Kenneth Waltz, anarchy is the ordering principle of the international system. Because no higher power can be relied upon to come to a state’s rescue, each state must look after its own security. This logic is central to understanding why even peaceful nations prepare for the possibility of conflict.

The self-help system 🔗

Anarchy gives rise to what realists call a self-help system. Since no one else is guaranteed to protect them, states must rely on their own capabilities to ensure survival. They can do this in two main ways: by building up their own military and economic strength, known as internal balancing, or by forming alliances with other states, known as external balancing.

This self-help logic shapes nearly every major foreign policy decision. Defence budgets, weapons development, and strategic partnerships all flow from the basic understanding that, in the end, a state can depend only on itself.

The security dilemma 🔗

One troubling consequence of anarchy is the security dilemma, a concept coined by John Herz. When one state strengthens its military to feel safer, neighbouring states often perceive this as a threat and respond by arming themselves. The result is an arms race in which everyone ends up feeling less secure, even though each was only trying to protect itself. As realists point out, the very means of security for one state can become the means by which other states feel threatened. This dilemma helps explain why mistrust and tension persist in international politics even without any state intending aggression.

Power politics dominates global affairs 🔗

For realists, power is the currency of international politics. States constantly assess their own power relative to others, and this calculation drives their behaviour. Power is usually measured in terms of factors like military strength, economic resources, population, territory, and political stability.

The classical realist Hans Morgenthau placed power at the very heart of his theory. He famously argued that statesmen think and act in terms of interest defined as power. In his influential 1948 work Politics Among Nations, Morgenthau laid out six principles of political realism, emphasising that the national interest of any state is best understood through the lens of power. A national interest that is not backed by power, in this view, exists only on paper.

The balance of power 🔗

A central concept flowing from power politics is the balance of power. Realists believe that the international system tends to be more stable when power is distributed relatively evenly among states. If a single state becomes too powerful, it may threaten others and tempt domination, which provokes weaker states to band together to counter it.

This balancing behaviour is one of the most observable patterns in history. States form alliances, shift partnerships, and adjust their strategies to prevent any one power from achieving hegemony. For Waltz, the balance of power is both a recurring tendency and a stabilising mechanism that emerges naturally from the structure of an anarchic system.

States are rational and self-interested actors 🔗

Realism assumes that states behave as rational actors. This means decision-makers carefully weigh the costs and benefits of their options and choose the course of action that best advances the national interest. Taking actions that would leave a state weak or vulnerable would simply be irrational. This assumption of rationality allows realists to predict and explain state behaviour in a systematic way, regardless of the personality or ideology of any particular leader.

Closely linked to rationality is the assumption of self-interest. States act to advance their own interests, often in competition with one another, rather than out of moral or ideological motives. Realists are not arguing that morality is irrelevant to human life, but they maintain that in the dangerous arena of international politics, abstract moral principles cannot always guide the survival-driven choices of states.

Human nature versus structure: two faces of realism 🔗

Realists agree on the assumptions above, but they disagree on why states pursue power. This disagreement separates the two major branches of the theory.

Classical realism and human nature 🔗

Classical realists, such as Morgenthau, locate the source of conflict in human nature. Drawing on thinkers like Machiavelli and Hobbes, they argue that human beings are inherently egoistic and possess an enduring desire for power. Because states are run by people, this flawed and power-seeking nature is projected onto the behaviour of states themselves. From this perspective, our selfishness and inability to fully trust others leads to predictable patterns of competition and conflict throughout recorded history.

Neo-realism and the structure of the system 🔗

Kenneth Waltz challenged this reliance on human nature, which he considered too difficult to measure scientifically. In his 1979 book Theory of International Politics, he developed neo-realism, also called structural realism. Waltz argued that states pursue power not because of any inner human flaw, but because the anarchic structure of the international system compels them to. Variables like anarchy and the distribution of power can be observed and measured, making the theory more rigorous. For Waltz, structure shapes behaviour: place any state in an anarchic system, and it will be driven toward self-help and balancing, regardless of who its leaders are.

Why realism still matters 🔗

Realism remains one of the most widely used frameworks in the world of policymaking. Its assumptions about anarchy, survival, power, and self-interest continue to explain persistent features of global politics, from territorial disputes to arms build-ups to shifting alliances. Critics from liberal and constructivist traditions argue that realism is too pessimistic and overlooks cooperation, international law, and the role of ideas and institutions. Yet even its critics acknowledge that the realist lens captures something enduring about how states behave when their survival is at stake. Whether analysing great-power rivalry or regional security in South Asia, the core assumptions of realism offer a starting point that few serious students of international relations can afford to ignore.

What do you think? Does the realist emphasis on power and survival still offer the most convincing explanation of how states behave in the twenty-first century? And can transnational challenges like climate change, pandemics, and economic interdependence be adequately understood through a framework built around state-centric power politics?

References

1. https://www.e-ir.info/2018/02/27/introducing-realism-in-international-relations-theory/
2. https://ondisc.nd.edu/news-media/news/an-introduction-to-realism-in-international-relations/
3. https://web.isanet.org/Web/Conferences/CEEISA-ISA-LBJ2016/Archive/5436e425-0feb-4b25-a844-73018e5eac16.pdf
4. https://plato.stanford.edu/entries/realism-intl-relations/
5. https://www.e-ir.info/2021/04/16/a-history-of-anarchy-a-critique-and-apposite-alternatives/
6. https://www.yourarticlelibrary.com/international-politics/morgenthaus-realist-theory-6-principles/48472
7. https://simonchkuaseli.com/kenneth-waltz-and-the-logic-of-anarchy-structure-power-and-the-foundations-of-neorealism/
8. https://www.e-ir.info/pdf/72860