Key Assumptions of Liberalism in International Relations

For centuries, the dominant story about world politics was a grim one: states locked in a perpetual struggle for power, where cooperation was rare and war was always around the corner. Liberalism in international relations offers a strikingly different picture. It argues that the world is not condemned to conflict, that human beings and the societies they build can improve over time, and that states can find ways to work together for mutual gain. But this optimism is not naive hope. It rests on a set of carefully reasoned assumptions about who really shapes foreign policy, how state interests are formed, and why cooperation is possible even in a world without a global government. Understanding these underlying assumptions is the key to grasping why liberalism became one of the most influential frameworks in the study of global politics.

What liberalism assumes about world politics
Individuals and groups are the primary actors
Why this matters
State interests are dynamic, not fixed
Interests are shaped by domestic and international conditions
A concrete example
Mutual interests can sustain cooperation without coercion
The role of interdependence and institutions
The belief in human perfectibility and democracy
Democratic peace theory
The strengths and the criticisms

What liberalism assumes about world politics

Liberalism is not a single, rigid theory but a family of ideas that share a common foundation. At its heart, liberal thought rejects the realist claim that power and self-interest alone explain how states behave. Instead, it brings new factors into view, especially the role of individuals, citizens, and international organisations in shaping outcomes. As one widely used introductory text puts it, liberalism contains a variety of arguments about how institutions, behaviours, and economic connections can contain and mitigate the violent power of states.

The political scientist Andrew Moravcsik gave this tradition its most precise modern formulation. He argued that liberal theory can be restated through a few core assumptions, beginning with the idea that the fundamental actors in international politics are rational individuals and private groups who organise and exchange to promote their interests. This is what scholars call a “bottom-up” view of politics. Let us examine each of the major assumptions in turn.

Individuals and groups are the primary actors

For realists, the state is treated as a single, unified actor, like a billiard ball bouncing against others on a table. Liberalism rejects this. It assumes that the true building blocks of international politics are individuals and the social groups they form, such as businesses, political parties, civil society organisations, and interest groups.

According to Moravcsik’s account, the policies of states ultimately represent what individuals and groups within society actually want. The state does not have interests floating above its citizens. Rather, it acts as a kind of transmission belt, channelling the demands that come from below. This is why liberalism is described as having a “bottom-up” logic: foreign policy is rooted in domestic society, not handed down from some abstract national interest.

Why this matters

This assumption has powerful consequences. If individuals and groups shape state behaviour, then who holds power inside a country, which groups are organised, and what those groups want all become essential to explaining foreign policy. A government dominated by export-oriented industries may push hard for free trade agreements. A government responsive to farmers may resist them. The point is that the content of foreign policy cannot be understood without looking inside the state at the society it represents.

State interests are dynamic, not fixed

A second key assumption is that state interests are not permanent or pre-given. Realists tend to assume that every state wants the same basic things: security, survival, and power. Liberalism disagrees. It holds that what a state wants can change over time and can differ greatly from one state to another.

Moravcsik captures this with the idea that states act on the basis of “state preferences” derived from the demands of a subset of domestic individuals and social groups. Because the groups that influence a government can shift, and because their demands change, a state’s interests are dynamic. They can be self-regarding, focused narrowly on the state’s own advantage, or other-regarding, taking into account the welfare of other states and peoples.

This means liberalism does not assume that states are always selfish or always cooperative. The crucial insight is that preferences come first. A state must have what Moravcsik calls a “social purpose,” a perceived underlying stake in the matter at hand, before it will act at all in international affairs, whether to start a conflict or to begin cooperation.

Interests are shaped by domestic and international conditions

If state preferences are dynamic, what shapes them? Liberalism’s answer is that interests are formed by both domestic conditions and international conditions working together.

On the domestic side, factors such as political leadership, public opinion, economic structures, and social movements all push and pull on what a government decides to pursue abroad. On the international side, global economic trends, the presence of international institutions, and a state’s relationships with other countries all feed back into how it defines its goals.

A concrete example

Consider climate policy. A country’s decision to commit to reducing carbon emissions under an agreement like the Paris Agreement is rarely driven by a single factor. Domestically, it may be pushed by public health concerns over air pollution, by industries that see opportunity in renewable energy, and by an electorate that demands cleaner growth. Internationally, it may be shaped by pressure from trading partners and by the desire to be seen as a responsible global player. The final position reflects this interplay of forces inside and outside the country, exactly as liberal theory predicts.

This is also why liberalism stresses interdependence. The third of Moravcsik’s core assumptions is that the interdependent distribution of preferences among states shapes how each one behaves. No state forms its goals in isolation; each must consider the preferences of others, which may converge or clash, before deciding how to act.

Mutual interests can sustain cooperation without coercion

Perhaps the most distinctive liberal assumption is that cooperation is possible and durable even without a central authority forcing states to behave. In a world that is formally anarchic, meaning there is no global government above states, realists expect distrust and conflict. Liberals argue that shared and overlapping interests can hold cooperation together on their own.

An open educational text on the subject summarises the liberal position well: it is fundamentally optimistic about the potential for cooperation among states, holding that states can and do work together for mutual benefit. This cooperation is supported by international institutions, economic interdependence, and the spread of democratic governance.

The role of interdependence and institutions

This idea was developed powerfully by Robert Keohane and Joseph Nye through their concept of complex interdependence, introduced in the 1970s. They argued that as economic and social ties between countries deepen, the usefulness of military force declines and the influence of transnational and non-state actors rises. When countries are densely connected through trade, investment, and shared problems, the cost of conflict grows and the incentive to cooperate increases.

Climate change is often cited as a textbook case of this dynamic. No single nation can solve it alone, military power is largely irrelevant to the problem, and addressing it requires coordinated action across many channels of diplomacy, science, business, and civil society. International institutions help by setting shared rules, providing information, and building the trust that allows cooperation to last without anyone being coerced.

The belief in human perfectibility and democracy

Underlying all of these assumptions is a deeper philosophical conviction: that human beings and their societies are capable of improvement. Liberalism inherits the Enlightenment belief in progress. It holds that reason, education, and better institutions can gradually reduce violence and expand cooperation over time. This faith in perfectibility separates liberalism sharply from the realist view of a fixed and competitive human nature.

Closely tied to this is the liberal emphasis on democracy. Liberals argue that democratic states, accountable to their citizens and bound by the rule of law, are less likely to pursue aggressive foreign policies and more likely to cooperate peacefully with one another.

Democratic peace theory

This conviction crystallised into one of liberalism’s most famous and debated claims: democratic peace theory. The proposition holds that democracies rarely, if ever, go to war with each other. According to scholarly accounts, this idea is rooted in the work of the philosopher Immanuel Kant, who suggested that states governed as republics would tend toward peace.

Kant’s 1795 essay Perpetual Peace laid the philosophical groundwork. In it he envisioned a zone of peace among republics resting on three definitive articles: republican constitutions, a federation of free states, and a principle of universal hospitality among citizens of the world. Modern scholars, most notably Michael Doyle, revived these ideas to argue that liberal democracies do not wage war against one another.

Two explanations are usually offered. One is normative: democracies share values of compromise and peaceful dispute resolution that they extend to other democracies. The other is structural or institutional: democratic governments face checks such as elections, legislatures, and public opinion that make it harder to rush into war. From this perspective, the spread of democracy is seen as a pathway toward a more stable and cooperative world order.

The strengths and the criticisms

The great advantage of the liberal approach, in Moravcsik’s view, is that it provides a foundation for explaining a wide range of state behaviour, both conflict and cooperation, without assuming in advance which one will dominate. By grounding foreign policy in society, it offers a flexible and realistic account of why states do what they do.

Yet liberalism faces important criticisms. Realists charge that it underestimates the persistence of power politics and security competition. Critics also note that liberal theories can downplay the social fabric of international society. And democratic peace theory in particular has drawn sustained scrutiny: some scholars argue the historical evidence is contested, that definitions of “democracy” vary widely, and that the theory has at times been used to justify interventionist and even imperial foreign policies, a far cry from Kant’s original vision. These debates are part of what keeps liberalism a living, evolving tradition rather than a settled doctrine.

What do you think? If state interests really are shaped from the bottom up by domestic society, how much can a country’s foreign policy genuinely change when its government changes? And do you find the liberal faith in human perfectibility and cooperation convincing, or does the persistence of war suggest the realists have the stronger case?

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Table of Contents

What liberalism assumes about world politics 🔗

Individuals and groups are the primary actors 🔗

Why this matters 🔗

State interests are dynamic, not fixed 🔗

Interests are shaped by domestic and international conditions 🔗

A concrete example 🔗

Mutual interests can sustain cooperation without coercion 🔗

The role of interdependence and institutions 🔗

The belief in human perfectibility and democracy 🔗

Democratic peace theory 🔗

The strengths and the criticisms 🔗