Introducing Liberalism in International Relations Theory

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Liberalism is a defining feature of modern democracy, illustrated by the prevalence of the term ‘liberal democracy’ as a way to describe countries with free and fair elections, rule of law and protected civil liberties. However, liberalism – when discussed within the realm of IR theory – has evolved into a distinct entity of its own. Liberalism contains a variety of concepts and arguments about how institutions, behaviours and economic connections contain and mitigate the violent power of states. When compared to realism, it adds more factors into our field of view – especially a consideration of citizens and international organisations. Most notably, liberalism has been the traditional foil of realism in IR theory as it offers a more optimistic world view, grounded in a different reading of history to that found in realist scholarship.

The basics of liberalism

Liberalism is based on the moral argument that ensuring the right of an individual person to life, liberty and property is the highest goal of government. Consequently, liberals emphasise the wellbeing of the individual as the fundamental building block of a just political system. A political system characterised by unchecked power, such as a monarchy or a dictatorship, cannot protect the life and liberty of its citizens. Therefore, the main concern of liberalism is to construct institutions that protect individual freedom by limiting and checking political power. While these are issues of domestic politics, the realm of IR is also important to liberals because a state’s activities abroad can have a strong influence on liberty at home. Liberals are particularly troubled by militaristic foreign policies. The primary concern is that war requires states to build up military power. This power can be used for fighting foreign states, but it can also be used to oppress its own citizens. For this reason, political systems rooted in liberalism often limit military power by such means as ensuring civilian control over the military.

Wars of territorial expansion, or imperialism – when states seek to build empires by taking territory overseas – are especially disturbing for liberals.   Not only do expansionist wars strengthen the state at the expense of the people, these wars also require long-term commitments to the military occupation and political control of foreign territory and peoples. Occupation and control require large bureaucracies that have an interest in maintaining or expanding the occupation of foreign territory. For liberals, therefore, the core problem is how to develop a political system that can allow states to protect themselves from foreign threats without subverting the individual liberty of its citizenry. The primary institutional check on power in liberal states is free and fair elections via which the people can remove their rulers from power, providing a fundamental check on the behaviour of the government. A second important limitation on political power is the division of political power among different branches and levels of government – such as a parliament/congress, an executive and a legal system. This allows for checks and balances in the use of power.

Democratic peace theory is perhaps the strongest contribution liberalism makes to IR theory. It asserts that democratic states are highly unlikely to go to war with one another. There is a two-part explanation for this phenomenon. First, democratic states are characterised by internal restraints on power, as described above. Second, democracies tend to see each other as legitimate and unthreatening and therefore have a higher capacity for cooperation with each other than they do with non-democracies. Statistical analysis and historical case studies provide strong support for democratic peace theory, but several issues continue to be debated. First, democracy is a relatively recent development in human history. This means there are few cases of democracies having the opportunity to fight one another. Second, we cannot be sure whether it is truly a ‘democratic’ peace or whether some other factors correlated with democracy are the source of peace – such as power, alliances, culture, economics and so on. A third point is that while democracies are unlikely to go to war with one another, some scholarship suggests that they are likely to be aggressive toward non-democracies – such as when the United States went to war with Iraq in 2003. Despite the debate, the possibility of a democratic peace gradually replacing a world of constant war – as described by realists – is an enduring and important facet of liberalism.

We currently live in an international system structured by the liberal world order built after the Second World War (1939–1945). The international institutions, organisations and norms (expected behaviours) of this world order are built on the same foundations as domestic liberal institutions and norms; the desire to restrain the violent power of states. Yet, power is more diluted and dispersed internationally than it is within states. For example, under international law, wars of aggression are prohibited. There is no international police force to enforce this law, but an aggressor knows that when breaking this law it risks considerable international backlash. For example, states – either individually or as part of a collective body like the United Nations – can impose economic sanctions or intervene militarily against the offending state. Furthermore, an aggressive state also risks missing out on the benefits of peace, such as the gains from international trade, foreign aid and diplomatic recognition.

The fullest account of the liberal world order is found in the work of Daniel Deudney and G. John Ikenberry (1999), who describe three interlocking factors:

First, international law and agreements are accompanied by international organisations to create an international system that goes significantly beyond one of just states. The archetypal example of such an organisation is the United Nations, which pools resources for common goals (such as ameliorating climate change), provides for near constant diplomacy between enemies and friends alike and gives all member states a voice in the international community.

Second, the spread of free trade and capitalism through the efforts of powerful liberal states and international organisations like the World Trade Organization, the International Monetary Fund and the World Bank creates an open, market-based, international economic system. This situation is mutually beneficial as a high level of trade between states decreases conflict and makes war less likely, since war would disrupt or cancel the benefits (profits) of trade. States with extensive trade ties are therefore strongly incentivised to maintain peaceful relations. By this calculation, war is not profitable, but detrimental to the state.

The third element of the liberal international order is international norms. Liberal norms favour international cooperation, human rights, democracy and rule of law. When a state takes actions contrary to these norms, they are subject to various types of costs. However, international norms are often contested because of the wide variation in values around the globe. Nevertheless, there are costs for violating liberal norms. The costs can be direct and immediate. For example, the European Union placed an arms sale embargo on China following its violent suppression of pro-democracy protesters in 1989. The embargo continues to this day. The costs can also be less direct, but equally as significant. For example, favourable views of the United States decreased significantly around the world following the 2003 invasion of Iraq because the invasion was undertaken unilaterally (outside established United Nations rules) in a move that was widely deemed illegitimate.

Most liberal scholarship today focuses on how international organisations foster cooperation by helping states overcome the incentive to escape from international agreements. This type of scholarship is commonly referred to as ‘neoliberal institutionalism’ – often shortened to just ‘neoliberalism’. This often causes confusion as neoliberalism is also a term used outside IR theory to describe a widespread economic ideology of deregulation, privatisation, low taxes, austerity (public spending cuts) and free trade. The essence of neoliberalism, when applied within IR, is that states can benefit significantly from cooperation if they trust one another to live up to their agreements. In situations where a state can gain from cheating and escape punishment, defection is likely. However, when a third party (such as an impartial international organisation) is able to monitor the behaviour of signatories to an agreement and provide information to both sides, the incentive to defect decreases and both sides can commit to cooperate. In these cases, all signatories to the agreement can benefit from absolute gains. Absolute gains refer to a general increase in welfare for all parties concerned – everyone benefits to some degree, though not necessarily equally. Liberal theorists argue that states care more about absolute gains than relative gains. Relative gains, which relate closely to realist accounts, describe a situation where a state measures its increase in welfare relative to other states and may shy away from any agreements that make a competitor stronger. By focusing on the more optimistic viewpoint of absolute gains and providing evidence of its existence via international organisations, liberals see a world where states will likely cooperate in any agreement where any increase in prosperity is probable.

Liberal theory and American imperialism

One of the more interesting illustrations of liberalism comes from the foreign policy of the United States during the early twentieth century. During this period, the United States was liberal, but according to the dominant historical narrative, also imperialistic (see Meiser 2015). So, there appears to be a contradiction. If we take a closer look we see that the United States was more restrained than commonly believed, particularly relative to other great powers of that era. One simple measure is the level of colonial territory it accrued compared to other great powers. By 1913, the United States claimed 310,000 square kilometres of colonial territory, compared to 2,360,000 for Belgium, 2,940,000 for Germany and 32,860,000 for the United Kingdom (Bairoch 1993, 83). In fact, the bulk of American colonial holdings was due to the annexation of the Philippines and Puerto Rico, which it inherited after defeating Spain in the Spanish-American War of 1898. The United States exhibited such restraint because, as suggested by liberal theory, its political structure limited expansionism. Examining US–Mexico relations during the early twentieth century helps illustrate the causes of this American restraint.

In the spring of 1914, the United States invaded the Mexican city of Veracruz because of a dispute over the detention of several American sailors in Mexico. However, US–Mexican relations were already troubled because of President Woodrow Wilson’s liberal belief that it was the duty of the United States to bring democracy to Mexico, which was a dictatorship. The initial objectives of the American war plan were to occupy Veracruz and neighbouring Tampico and then blockade the east coast of Mexico until American honour was vindicated – or a regime change occurred in Mexico. After American forces landed in Veracruz, senior military leaders and Wilson’s top diplomatic advisor in Mexico advocated an escalation of the political objectives to include occupation of Mexico City – there were also vocal proponents who advocated the full occupation of Mexico. Wilson did not actually follow any of the advice he received. Instead, he reduced his war aims, halted his forces at Veracruz and withdrew US forces within a few months. Wilson exercised restraint because of American public opposition, his own personal values, unified Mexican hostility and the military losses incurred in the fighting. International opinion also appears to have influenced Wilson’s thinking as anti-Americanism began to sweep through Latin America. As Arthur Link points out, ‘Altogether, it was an unhappy time for a President and a people who claimed the moral leadership of the world’ (Link 1956, 405).

By 1919, a pro-interventionist coalition developed in the United States built on frustration with President Wilson’s prior restraint and new fears over the Mexican Constitution of 1917, which gave the Mexican people ownership of all subsoil resources. This potentially endangered foreign ownership of mines and oilfields in Mexico. Interventionists wanted to turn Mexico into an American protectorate – or at least seize the Mexican oil fields. This coalition moved the country toward intervention while Wilson was distracted by peace negotiations in Europe and then bedridden by a stroke. The path to intervention was blocked only after Wilson recovered sufficiently to regain command of the policy agenda and sever the ties between the interventionists. Wilson had two main reasons for avoiding the more belligerent policy path. First, he saw the Houses of Congress (with the support of some members of the executive branch) attempting to determine the foreign policy of the United States, which Wilson viewed as uncon- stitutional. In the American system, the president has the authority to conduct foreign policy. His assertion of authority over foreign policy with Mexico was therefore a clear attempt to check the power of Congress in policymaking. Second, Wilson was determined to maintain a policy consistent with the norm of anti-imperialism, but also the norm of self-determination – the process by which a country determines its own statehood and chooses its own form of government. Both of these norms remain bedrocks of liberal theory today.

US relations with Mexico in this case show how institutional and normative domestic structures restrained the use of violent power. These institutional restraints can break down if the political culture of a society does not include a strong dose of liberal norms. For example, anti-statism (a belief that the power of the government should be limited) and anti-imperialism (a belief that conquest of foreign peoples is wrong) are liberal norms. A society infused by liberal norms has an added level of restraint above and beyond the purely institutional limitations on state power. A liberal citizenry will naturally oppose government actions that threaten individual liberty and choose represen-  tatives that will act on liberal preferences. The institutional separation of powers in the United States allowed Wilson to block the interventionist efforts of Congress and others. The liberal norm of anti-imperialism restrained American expansion through the mechanisms of public opinion and the personal values of the president of the United States. Institutions and norms worked symbiotically. International opinion put additional pressure on American political leaders due to increasing trade opportunities with Latin American countries throughout the early 1900s. Precisely as liberal theory details, the absolute gains and opportunities offered by trade, together with preferences for self-determination and non-interference, acted as a restraint on US expansionism toward Mexico in this most imperial of periods in world history.


A core argument of liberalism is that concentrations of unaccountable violent power are the fundamental threat to individual liberty and must be restrained. The primary means of restraining power are institutions and norms at both domestic and international level. At the international level institutions and organisations limit the power of states by fostering cooperation and providing a means for imposing costs on states that violate international agreements. Economic institutions are particularly effective at fostering cooperation because of the substantial benefits that can be derived from economic interdependence. Finally, liberal norms add a further limitation on the use of power by shaping our understanding of what types of behaviour are appropriate. Today, it is clear that liberalism is not a ‘utopian’ theory describing a dream world of peace and happiness as it was once accused of being. It provides a consistent rejoinder to realism, firmly rooted in evidence and a deep theoretical tradition.

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