International politics often looks like a contest of strength. Governments build armies, defend borders and compete for influence. War dominates the headlines, while diplomacy can appear slow, fragile and frustrating.
Liberalism offers a different way of understanding this world. It asks how countries can build lasting cooperation even when they disagree, distrust one another and have no world government to settle their disputes.
Its central insight is that power matters, but so do political institutions, economic relationships and the people whose interests shape government policy. Peace is possible, although it has to be organised and maintained.
What does liberalism mean in International Relations?
In International Relations, liberalism is a family of theories about how states behave and why they cooperate or fight. It is broader than support for a particular political party or an economic policy.
Liberal approaches look inside countries as well as at relations between them. Who holds political power? Which interests influence decisions? How accountable are leaders? These questions help explain why governments facing similar international circumstances might pursue very different foreign policies.
Andrew Moravcsik’s influential account places the relationship between states and society at the centre of liberal theory. A country’s interests emerge from its domestic and transnational social environment; they cannot simply be assumed from its military strength or position on the map. Andrew Moravcsik, Taking Preferences Seriously.
Imagine two neighbouring countries discussing a trade agreement. Exporters might support it, industries facing foreign competition might oppose it, and voters might worry about jobs or standards. The eventual negotiating position reflects political choices about whose interests count.
This makes liberalism useful for understanding disagreement as well as cooperation.
Democracy and the possibility of peace
One of the best-known liberal arguments is the democratic peace theory: established liberal democracies rarely fight wars against one another.
The proposed explanations include public accountability, constraints on executive power and expectations that disagreements can be settled through negotiation. Leaders may find it harder to justify war against another government they regard as legitimate.
The qualification matters. This is principally a claim about relations between democracies, rather than a claim that democracies are peaceful towards everyone. Michael Doyle’s work explores precisely this tension: liberal states can maintain peace among themselves while remaining suspicious of, or aggressive towards, non-liberal states. Michael Doyle, Liberal Internationalism: Peace, War and Democracy.
Nor does an observed pattern settle every question about its cause. Researchers must consider whether democracy itself explains peace, or whether alliances, economic conditions and other influences help account for it.
Democratic peace is therefore a serious argument to examine, rather than a promise that holding elections automatically removes the danger of war.
Trade and economic interdependence
A second liberal argument concerns economic interdependence.
When countries depend on each other for markets, investment and supplies, conflict becomes more costly. War can damage the relationships that sustain jobs, businesses and public revenues. This creates incentives to negotiate.
Research by John Oneal and Bruce Russett found that democracy, economic interdependence and international organisations were associated with a lower probability of militarised disputes across their historical dataset. Their study also found that some realist factors mattered, suggesting these explanations can complement one another. Oneal and Russett, The Kantian Peace.
Yet dependence can also create vulnerability. Consider a hypothetical country relying on a single foreign supplier for essential fuel. That relationship gives both sides reasons to preserve trade, but it may also give the supplier political leverage.
The practical question is therefore how interdependence is structured. Are its benefits broadly shared? Can either side exploit the other’s dependence? Do governments believe the relationship will remain reliable?
Trade can support peace without guaranteeing it.
Why international institutions matter
The institutional strand commonly discussed alongside liberalism asks how rules and organisations help countries cooperate.
International politics operates under anarchy, meaning there is no overarching world government. The term does not mean that everything is chaotic. It means that states must organise cooperation without a single authority standing above them.
Institutions can provide regular meetings, shared information and procedures for handling disputes. They can make commitments easier to assess and give governments reasons to consider the consequences of breaking agreements.
G. John Ikenberry describes international institutions as central tools in liberal internationalism’s efforts to build cooperative order and enable peaceful change. Ikenberry, Liberalism, Institutional Statecraft, and International Order.
For example, two countries sharing a river might establish a joint body to monitor water levels and negotiate its use. Neither has to abandon its national interests. Cooperation gives both a more predictable way to pursue them.
Liberal institutionalism makes that reasoning central: governments can benefit from arrangements that reduce uncertainty and support repeated cooperation.
Where the liberal model faces criticism
The strongest criticism is that cooperation remains vulnerable to power politics.
A realist would ask what happens when a government believes its survival is at stake. Economic benefits and diplomatic procedures may become secondary to military security. Institutions may struggle when powerful members refuse to accept limits.
A further criticism concerns inequality. An agreement can produce an overall economic benefit while distributing its rewards unfairly. People who bear the costs may have little reason to support an international arrangement that others celebrate.
There is also a difficult distinction between explaining international politics and advocating liberal internationalism. A theory about the effects of democracy does not, by itself, justify using force to impose democracy elsewhere.
Any political project claiming to defend freedom must confront the consequences of its methods. Respect for rights loses credibility when it is applied selectively.
Peace requires political work
Liberalism’s lasting contribution is to explain how cooperation can become possible and durable.
It directs attention towards accountable government, relationships across borders and institutions that help manage disagreement. It also reminds us that foreign policy begins within society: leaders make choices shaped by the people and interests they represent.
My assessment is that liberalism is most persuasive when treated as a conditional argument. Cooperation becomes more likely when governments have compatible interests, credible commitments and reasons to value a continuing relationship. Those conditions can weaken, and rebuilding them takes work.
Peace requires more than goodwill. It needs arrangements that make restraint worthwhile, allow disputes to be heard and give people a meaningful stake in cooperation.
That is the challenge liberalism puts before International Relations: understanding how countries can live together when neither trust nor agreement can be taken for granted.
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