Key Thinkers and Ideas in Classical Realism

When two nations clash over territory, trade, or influence, what really drives the conflict? Classical realism offers a stark answer: human nature itself. This school of thought, which gained major prominence in international relations after the Second World War, argues that the struggle for power is not an accident of bad leadership or flawed institutions but a permanent feature of politics rooted in the human condition. To understand why classical realists think this way, we need to meet the thinkers who built the tradition, from an ancient Greek historian to a strategist in Mauryan India, and trace the ideas that still shape how states behave today.

What classical realism actually claims
Thucydides and the logic of power politics
The Melian dialogue
Kautilya and the realism of the Arthashastra
The Mandala theory and Saptanga
Machiavelli and the survival of the state
Hobbes and the state of nature
E.H. Carr and the intersection of power and morality
Realism against utopianism
From classical realism to its modern form

What classical realism actually claims

Classical realism is built on a pessimistic reading of human nature. It holds that people are inherently driven by selfishness, fear, and a desire for power, and that states, being run by human beings, behave the same way. The desire for power and the propensity for conflict are seen as natural rather than learned. Because there is no world government to enforce order, international politics becomes a competitive arena where each state pursues its own survival and security above everything else.

This is the feature that separates classical realism from its successor, neo-realism. Classical realists locate the source of conflict inside human beings. Neo-realists, led by Kenneth Waltz, later shifted the explanation to the structure of the international system instead of human nature. The patterns they describe are similar; the cause they identify is different.

A few core assumptions tie the tradition together. States are the central actors. The international system is anarchic, meaning there is no higher authority above sovereign states. National interest, defined in terms of power, is the primary motive of any state. And moral considerations, while not entirely dismissed, usually take second place to survival.

Thucydides and the logic of power politics

The intellectual roots of realism stretch back roughly 2,400 years to the Greek historian Thucydides. In his History of the Peloponnesian War, he documented the long conflict between Athens and Sparta and, in doing so, captured ideas that realists still rely on. He is often called one of the intellectual godfathers of realism because of his unflinching focus on power and self-interest.

The Melian dialogue

The clearest expression of his thinking appears in the famous Melian Dialogue. During the war, Athens demanded that the small, neutral island of Melos submit and pay tribute. The Melians appealed to fairness, justice, and the gods. The Athenians replied that such appeals were irrelevant when power was unequal. In Thucydides’ account, the strong do what they have the power to do and the weak accept what they must. When Melos refused to surrender, Athens besieged the city, killed the men, and enslaved the women and children.

The episode is studied in nearly every international relations course because it strips politics down to its rawest form: in a contest between morality and power, power tends to win. Thucydides also gave us another enduring insight when he explained the war’s deeper cause as the rise of Athens and the fear it created in Sparta. This idea of a rising power threatening an established one continues to inform debates about great-power rivalry today.

Kautilya and the realism of the Arthashastra

Realist thinking was not limited to the West. Around the fourth century BCE, Kautilya, also known as Chanakya, served as adviser to Chandragupta Maurya and composed the Arthashastra, a detailed manual on statecraft, economy, diplomacy, and war. The scholar Roger Boesche described Kautilya as the first great political realist, placing him alongside Machiavelli and Morgenthau in the realist canon.

What makes the Arthashastra so striking is how closely it parallels Western realist texts on power and national interest. For Kautilya, relations between states were fundamentally relations of conflict, and a ruler had to rely on strength because the international environment offered no guarantees of safety. Some scholars place him in the school of offensive realism, since he favoured power maximisation over mere defence.

The Mandala theory and Saptanga

Kautilya’s Mandala theory imagined interstate politics as a series of concentric circles. An immediate neighbour was a likely rival, while a state lying beyond that neighbour was a potential ally, producing the logic that the enemy of my enemy is my friend. The theory stressed power, national interest, strategic alliances, and the primacy of security, the same priorities that modern realists emphasise.

His Saptanga theory described the state as an organism made up of seven elements or limbs, with the king at the centre. These elements served as a way to measure a state’s overall power before deciding whether to pursue war or peace. To manage relations with rival states, Kautilya laid out tools such as Sama (conciliation), Dana (gifts), Danda (force), and Bheda (division), along with a six-fold strategy of foreign policy. These ideas remain part of how scholars analyse India’s strategic culture and its gradual shift from post-independence idealism to strategic pragmatism.

Machiavelli and the survival of the state

Moving to Renaissance Italy, Niccolò Machiavelli sharpened the realist focus on power as the key to a ruler’s success. His most famous work, The Prince, written in the early sixteenth century, reads almost like a guidebook for leaders on how to gain and hold power in a dangerous world.

Machiavelli’s central contribution was the argument that a ruler must be willing to act immorally when the security of the state demands it. Politics, in his view, has its own rules separate from private morality. A leader who clings to ethical ideals at the cost of practical necessity will lose power and endanger the state. This pragmatic, sometimes ruthless, approach is why his name became a byword for cunning statecraft and why he is treated as a foundational realist thinker.

Hobbes and the state of nature

The English philosopher Thomas Hobbes added a powerful theoretical foundation in the seventeenth century with his book Leviathan. Writing during a period of civil war, Hobbes imagined what life would be like without any central authority. In this “state of nature,” with no government to keep order, life would collapse into a war of all against all, where fear and competition dominate every interaction.

Realists take this idea and apply it directly to international politics. Just as individuals in the state of nature lack a common authority, states in the international system have no world government above them. This anarchic environment forces each state to look after its own security and survival, because no one else will. Hobbes therefore supplies the logic of anarchy that explains why even peaceful states must prepare for conflict, and his influence on realist thought is so deep that later realists have been described as offering a restatement of the Hobbesian view of politics.

E.H. Carr and the intersection of power and morality

The transition from these classical foundations to a modern academic discipline owes a great deal to E.H. Carr. His 1939 book, The Twenty Years’ Crisis, was published on the eve of the Second World War and delivered a sharp critique of the idealism that had dominated thinking between the wars.

Realism against utopianism

Carr contrasted what he called utopianism with realism. The utopians, he argued, focused on what international politics ought to be, placing their faith in moral ideals, reason, and institutions like the League of Nations. Realists, by contrast, paid attention to facts, national interests, and the actual role of power. Carr believed the failure to take power seriously had left the democracies unprepared for the rise of aggressive revisionist states.

Carr identified three forms of power in international politics: military power, economic power, and power over opinion. Yet his position was more subtle than pure realism. He warned that realism on its own offers nothing but a naked struggle for power that makes any kind of international society impossible. Effective politics, he concluded, requires an uneasy compromise between power and morality, between reality and utopia. This refusal to abandon morality entirely is what makes Carr a bridge between the harsh realism of his predecessors and later, more systematic theories.

From classical realism to its modern form

The thinker who pulled these threads into a coherent academic framework was Hans Morgenthau. His book Politics Among Nations argued that politics is governed by objective laws rooted in human nature, and that the national interest, defined as power, is the proper guide for state behaviour. Morgenthau explicitly drew on earlier classical thinkers like Thucydides and Machiavelli, and is often called the father of modern classical realism.

Classical realism is not without critics. Liberals point to the growing importance of institutions and cooperation, while constructivists argue that state interests and identities are socially constructed rather than fixed by nature. The claim that human nature is permanently power-seeking is, after all, a philosophical assumption rather than a proven fact. Even so, the tradition remains influential, and analysts frequently return to realist frameworks when explaining contemporary great-power competition and conflict.

What do you think? If human nature really is the root cause of international conflict, can institutions and diplomacy ever produce lasting peace, or only temporary pauses in the struggle for power? And looking at Kautilya’s Mandala theory alongside Thucydides and Machiavelli, do you think realism is a universal truth about politics, or simply a recurring response to dangerous times?

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Table of Contents

What classical realism actually claims 🔗

Thucydides and the logic of power politics 🔗

The Melian dialogue 🔗

Kautilya and the realism of the Arthashastra 🔗

The Mandala theory and Saptanga 🔗

Machiavelli and the survival of the state 🔗

Hobbes and the state of nature 🔗

E.H. Carr and the intersection of power and morality 🔗

Realism against utopianism 🔗

From classical realism to its modern form 🔗