Liberalism in International Relations
- Edmarverson A. Santos
- 2 days ago
- 19 min read
Introduction
Liberalism in International Relations is a broad theoretical tradition that explains international politics by looking beyond the distribution of military and economic capabilities among states. Liberal approaches give analytical weight to domestic political institutions, societal interests, economic relationships, transnational interactions, and, in several strands of the tradition, international institutions. They do not assume that conflict disappears or that power becomes irrelevant. Their distinctive claim is that states operating under similar international constraints may behave differently because they represent different preferences, face different domestic pressures, and participate in different economic and institutional relationships.
This separates liberal theory from approaches that locate most of their explanatory power at the systemic level. Structural realism, for example, emphasizes international anarchy and the distribution of capabilities as major constraints on state behavior (Waltz, 1979). Liberal theory also asks how the preferences pursued by governments are formed. In one influential formulation, those preferences arise partly from relations between states and the societies they represent, making domestic interests and political representation relevant to explanations of international outcomes (Moravcsik, 1997). Material power remains consequential, but it does not by itself determine the objectives governments pursue.
Liberalism is not a single theory with a universally accepted taxonomy. Some accounts place democratic peace, commercial interdependence, and international institutions within a wider liberal tradition. Preference-based liberal theory, by contrast, gives particular causal importance to state–society relations and the formation of state preferences. Neoliberal institutionalism generally begins at a different point, asking how states with existing interests can sustain cooperation despite anarchy, uncertainty, and incentives to defect (Keohane, 1984; Moravcsik, 1997). These approaches overlap historically and analytically, but they do not rely on the same causal mechanism.
The intellectual origins of liberal international thought predate modern political science. Immanuel Kant's 1795 account of republican government, a federation of free states, and cosmopolitan right became an important reference point for later arguments about peace and international order (Kant, 1795). Twentieth-century liberal internationalists placed greater emphasis on collective security, international law, and organized cooperation, while later scholarship converted several liberal propositions into empirical research programs. These included the democratic or liberal peace, commercial interdependence, complex interdependence, and institutional explanations of cooperation (Doyle, 1983a; Keohane and Nye, 1977; Keohane, 1984; Oneal and Russett, 1999).
None of these arguments establishes a general law of peaceful international politics. The democratic peace proposition concerns relations between democratic states rather than a claim that democracies are consistently pacific toward all other states (Doyle, 1983a; Oneal and Russett, 1999). Economic interdependence can increase the prospective costs of conflict, yet its effects depend on expectations, asymmetries, and the strategic value of the relationship. International institutions can reduce uncertainty, facilitate reciprocity, and support repeated cooperation without eliminating conflicts of interest or unequal power (Keohane and Nye, 1977; Keohane, 1984). Liberal theory is strongest when these mechanisms are treated as conditional explanations of state behavior rather than as evidence that international politics naturally progresses toward cooperation.
1. What Liberalism in International Relations Explains
Liberal theory directs attention to sources of international behavior that cannot be inferred from material capabilities alone. States differ in the social interests they represent, the political institutions through which those interests gain influence, the economic relationships in which they participate, and the forms of international cooperation available to them. Liberal explanations consequently ask why governments exposed to similar external pressures can pursue different objectives or respond differently to comparable constraints (Moravcsik, 1997).
The terminology requires care because several distinct traditions use the language of liberalism. Liberal political philosophy addresses questions of liberty, rights, legitimate authority, and political order. Liberal internationalism refers more directly to programs for organizing international relations through institutions, rules, diplomacy, and forms of international cooperation. Liberal IR theory seeks causal explanations of international behavior. Economic neoliberalism and neoliberal institutionalism in International Relations are also separate concepts and should not be treated as interchangeable merely because they share the same label.
There is no universally accepted taxonomy of liberal IR theory. Broad classifications commonly place democratic or republican peace, commercial interdependence, and international institutions within the liberal tradition (Ikenberry, 2009). Moravcsik's formulation is more specific: liberal theory begins with individuals and social groups, political representation, and the state preferences produced through state–society relations. Within that framework, he distinguishes ideational liberalism, commercial liberalism, and republican liberalism according to the types of social preferences and representative structures shaping state behavior (Moravcsik, 1997). Institutionalism can then be analyzed separately as a theory concerned primarily with strategic interaction among states whose preferences have already been formed. These different classifications share an underlying problem: explaining why states operating within the same decentralized international system exhibit persistent variation in their interests, relationships, and willingness to cooperate.
2. From Kant to Liberal Internationalism
The intellectual ancestry of liberal international theory developed through several traditions rather than through a continuous progression toward contemporary political science. Arguments about representative government, commerce, international law, arbitration, and international organization emerged in different historical settings and often had explicitly normative purposes. Later IR scholarship converted some of these propositions into theories that could be examined comparatively and empirically (Ikenberry, 2009).
Political representation raised the possibility that the internal organization of states might affect decisions about war and peace. Commercial arguments suggested that cross-border exchange could change the costs associated with conflict, while proposals for arbitration and permanent institutions sought alternatives to the unilateral settlement of international disputes. These ideas did not originally form a single liberal research program, and their authors differed substantially over sovereignty, power, international authority, and the sources of peaceful order.
Modern liberal theory should consequently be distinguished from its intellectual predecessors. Kant was not a democratic peace theorist in the contemporary empirical sense, just as interwar internationalists did not collectively articulate the later theories of complex interdependence or neoliberal institutionalism. Their importance lies partly in identifying problems that subsequent scholarship reformulated: whether domestic political arrangements influence war, whether economic relations constrain conflict, and whether institutions can alter patterns of interstate behavior.
2.1 Kant, Republican Government, and Peace
Immanuel Kant's 1795 essay Toward Perpetual Peace: A Philosophical Sketch became one of the most important philosophical reference points for later liberal thinking about international order. His account connected three dimensions of peaceful political organization: republican constitutions within states, a federation of free states, and cosmopolitan right governing specified relations between individuals and foreign political communities (Kant, 1795). These elements belonged to a broader normative argument about the conditions of perpetual peace rather than to a statistical theory of democratic behavior.
Kant's republican argument centered on consent and the distribution of the costs of war. Under a republican constitution, citizens whose lives and resources would be affected by war would have to consent to undertaking it. Kant expected this requirement to make decisions for war more difficult than under political arrangements in which rulers could initiate conflict without personally bearing comparable burdens (Kant, 1795). His concept of republicanism should not be treated as identical to contemporary definitions or measurements of democracy.
Later liberal scholarship drew renewed attention to the connection between domestic political organization and international peace, but the modern democratic peace proposition represents a substantial theoretical and empirical reformulation. Kant's international thought also included interstate and cosmopolitan dimensions, so reducing his argument to a claim about regime type removes much of its original structure. His lasting importance for liberal IR theory lies in linking domestic institutions, relations among states, and cross-border interaction within a single account of the conditions under which peaceful relations might become more durable.
2.2 Interwar Liberal Internationalism
The First World War intensified demands for institutional changes to international politics. In his Fourteen Points address of January 1918, Woodrow Wilson advocated, among other proposals, more open diplomatic agreements, reductions in economic barriers, lower levels of national armaments, and the creation of a general association of nations (Wilson, 1918). The Covenant of the League of Nations subsequently established a permanent international organization whose provisions addressed arms reduction, respect for territorial integrity, procedures for the peaceful settlement of disputes, and collective measures against covenant-breaking states (Covenant of the League of Nations, 1919, Arts. 8, 10, 12–16).
Wilson was a prominent political advocate of the new order, but interwar internationalism cannot be reduced to Wilsonian diplomacy. Norman Angell, Alfred Zimmern, James T. Shotwell, international lawyers, peace organizations, and other scholars and political actors advanced different arguments concerning commerce, collective security, international organization, and the prevention of war. Their positions were neither theoretically uniform nor consistently opposed to considerations of national interest and power. The category later called “idealism” concealed substantial disagreements within interwar internationalist thought.
The crises of the 1930s exposed the weakness of the collective-security arrangements that had emerged after the First World War. Japanese expansion in Manchuria, Italy's invasion of Ethiopia, the rise of revisionist powers in Europe, and the eventual outbreak of the Second World War demonstrated the inability of existing institutions to prevent major aggression. E. H. Carr's The Twenty Years' Crisis criticized what he regarded as the utopian tendencies of interwar political thought and became an influential reference point for later realist scholarship (Carr, 1939). The familiar disciplinary account of a clearly defined first “great debate” between idealists and realists is more doubtful. Historical research has shown that this binary was constructed retrospectively and simplifies a much less orderly set of intellectual disagreements (Wilson, 1998).
3. Domestic Politics and State Preferences
Preference-based liberal theory changes the starting point of international analysis by asking where state objectives come from. Governments cannot always be assumed to value the same outcomes simply because they occupy comparable positions in the international system. Societies differ in their economic structures, political conflicts, identities, and institutional arrangements, and those differences can shape what governments seek internationally (Moravcsik, 1997).
Moravcsik's formulation begins with individuals and social groups pursuing material and ideational interests. Political institutions shape which interests gain effective representation and how social demands are translated into state preferences. Firms seeking access to foreign markets, industries exposed to international competition, voters concerned about security or economic welfare, and politically organized social groups can influence foreign policy, but their importance varies by issue and by the institutions through which political representation occurs. Liberal analysis consequently does not assume that “society” speaks with a single voice.
Domestic preference formation also operates within external constraints. Political institutions mediate competing social demands, while other states' preferences, bargaining positions, economic relationships, and material capabilities affect which objectives can actually be achieved. A government may strongly prefer an outcome that the surrounding international environment places beyond its reach. The analytical contribution of liberal theory is to distinguish the preferences states bring into international bargaining from the strategic interaction that follows, helping explain why governments facing similar external pressures can still pursue markedly different policies.
4. Democracy and the Liberal Peace
Democratic peace theory is one of the most extensively studied empirical programs associated with liberal International Relations. Its strongest proposition is dyadic: jointly democratic states have displayed a substantially lower incidence of interstate war with one another than other pairs of states. Doyle's revival of Kantian liberal arguments helped place this pattern at the center of modern IR research, followed by quantitative studies testing it across broader sets of states and conflicts (Doyle, 1983a; Maoz and Russett, 1993).
The proposition does not imply that democratic governments are generally pacific. Liberal states have fought wars, intervened abroad, and used force against nonliberal states, a distinction already central to Doyle's account of the liberal peace (Doyle, 1983b). Monadic claims about whether democracies are individually less conflict-prone must consequently be separated from the better-known claim concerning relations between democratic pairs.
Research on the democratic peace has moved well beyond identifying a correlation. Scholars have investigated domestic institutions, political norms, strategic interests, economic relationships, and methodological explanations for the observed pattern. Recent sensitivity analysis has found the negative association between joint democracy and conflict resistant to substantial unobserved confounding, although the mechanisms producing that association remain contested (Imai and Lo, 2021).
4.1 How Democratic Peace Is Explained
Institutional explanations focus on constraints affecting democratic leaders. Political competition, accountability, opposition, and institutional checks can increase the costs of pursuing unsuccessful or unpopular conflicts and make mobilization for war politically demanding. Such constraints may reduce incentives for escalation when both governments operate under comparable forms of political accountability (Maoz and Russett, 1993).
Normative accounts emphasize expectations generated by domestic practices of political competition and dispute settlement. Democratic systems normally recognize legitimate opposition and rely on bargaining rather than violence to settle struggles over political authority. Some democratic peace theorists argue that governments may extend these expectations to other democracies, making compromise more credible within democratic dyads (Maoz and Russett, 1993).
Neither explanation follows automatically from the empirical finding. Democratic institutions differ considerably, publics can support war, and executives may possess broad authority over foreign policy. Norms are also difficult to separate empirically from shared interests and institutional constraints. Theories of democratic peace must explain how regime characteristics affect decisions during actual disputes rather than treating democracy itself as a sufficient cause of peaceful behavior.
4.2 Evidence and Disputes over Democratic Peace
Evidence for an association between joint democracy and reduced interstate conflict is substantial, particularly for severe conflict and war, but both measurement and causal interpretation remain disputed. Results depend partly on how researchers classify political regimes, distinguish war from lower-level militarized disputes, and define the relevant universe of states and dyads. Earlier historical periods present an additional difficulty because democratic pairs were relatively uncommon (Maoz and Russett, 1993; Russett and Oneal, 2001).
Alternative explanations have focused on common strategic interests, alliances, economic development, international position, and other characteristics that may correlate with democracy. Layne (1994) questioned the causal weight assigned to democratic institutions through historical cases, while Rosato (2003) challenged both institutional and normative mechanisms. These critiques produced extensive responses and did not end the empirical research program.
More recent work has strengthened the case that the observed association cannot easily be dismissed as the product of conventional confounding alone. Imai and Lo (2021), using nonparametric sensitivity analysis, found that explaining away the relationship would require unusually strong unobserved confounding. That result does not establish one particular liberal mechanism. The democratic peace remains analytically significant precisely because evidence for the pattern is stronger than agreement about why it occurs.
5. Economic Interdependence and Commercial Peace
Commercial liberalism examines how international economic relationships affect the incentives of states and domestic groups. Trade can make military conflict more costly by placing valuable exchange and market access at risk, while firms and social groups benefiting from commerce may acquire interests in preserving stable relations (Polachek, 1980; Moravcsik, 1997). Empirical liberal-peace research has consequently treated economic interdependence as one possible constraint on interstate conflict (Russett and Oneal, 2001).
Commerce does not remove strategic rivalry. Governments may accept substantial economic losses when security, territory, political survival, or other objectives carry greater value. Economic interests are also distributed unevenly inside states, so the same international relationship may create constituencies favoring continued exchange and others demanding protection, confrontation, or disengagement.
Interdependence is better understood as a condition affecting political choices than as an independent guarantee of peace. Its consequences depend on how valuable a relationship is, which alternatives are available, how dependence is distributed between the parties, and what governments expect to happen to economic relations in the future.
5.1 Trade, Expectations, and the Costs of Conflict
A central commercial-peace mechanism concerns the opportunity costs of military conflict. States deriving substantial benefits from bilateral exchange can lose trade, market access, and future commercial opportunities when political disputes escalate into war. Higher expected economic losses can increase incentives to seek negotiated settlements, although they need not outweigh other strategic objectives (Polachek, 1980).
Existing trade levels reveal only part of that calculation. Copeland's trade-expectations theory argues that highly dependent states respond differently according to their expectations about future access to economically important markets. Positive expectations can reinforce the pacifying effects of interdependence; fears that access will deteriorate can make dependence appear strategically dangerous (Copeland, 1996).
The argument helps explain why extensive commerce can coexist with serious political rivalry. Interdependence may discourage violence when governments expect a profitable relationship to continue, yet restraint can weaken when leaders anticipate exclusion or believe dependence will leave them increasingly vulnerable. Commercial peace is conditional on expectations and strategic circumstances, not simply on the volume of trade.
5.2 Complex Interdependence and Unequal Dependence
Keohane and Nye expanded the study of interdependence beyond bilateral commerce. Complex interdependence describes relationships characterized by multiple channels connecting societies, no permanent hierarchy in which military security necessarily dominates every issue, and circumstances in which military force has limited usefulness for resolving many disputes between the states concerned (Keohane and Nye, 1977).
These channels include conventional diplomacy as well as relations among government agencies and interactions involving firms, organizations, and other transnational actors. Different issues may also generate different distributions of influence. A state with superior military capabilities does not automatically possess equivalent bargaining advantages in finance, trade, energy, environmental negotiations, or other specialized domains. Complex interdependence was proposed as an analytical model for particular relationships, not as a description of international politics as a whole.
Dependence can also be unequal. Keohane and Nye distinguished sensitivity to external change from vulnerability resulting from a lack of acceptable alternatives, allowing asymmetrical interdependence to become a source of bargaining power (Keohane and Nye, 1977). Farrell and Newman (2019) later showed how states occupying privileged positions within global economic networks may exploit those structures for coercive purposes. Interdependence can thus support cooperation while simultaneously creating political leverage and strategic vulnerability.
6. International Institutions and Cooperation
Neoliberal institutionalism asks how cooperation can persist among self-interested states in a decentralized international system. It does not require the disappearance of anarchy or assume that governments share identical interests. The analytical problem arises when states can gain from cooperation but face uncertainty about one another's behavior, concerns about compliance, and difficulties coordinating agreements without a central authority capable of enforcing them reliably (Keohane, 1984).
Institutions can alter these conditions without replacing states as the principal decision-makers. International regimes may establish principles, norms, rules, and decision-making procedures around which expectations converge, while formal organizations can provide more permanent structures for negotiation and administration (Krasner, 1982). Reporting, monitoring, consultation, and agreed procedures may reduce information problems and make departures from commitments easier to identify.
Repeated interaction can change incentives as well. Institutions may lower the transaction costs of negotiating successive agreements, connect present conduct to future cooperation, and facilitate reciprocal responses to compliance or defection. Axelrod and Keohane (1985) showed that prospects for cooperation under anarchy depend partly on expectations about future interaction, reciprocity, issue linkages, and the institutional setting within which governments bargain.
Institutional effects remain bounded by state interests and power. Design and outcomes are influenced by the preferences and bargaining resources of participating governments, and institutions cannot manufacture cooperation where the underlying conflict is too severe for mutually acceptable agreement. Rules may structure negotiations without eliminating disputes over who receives the benefits or bears the costs.
The institutionalist claim is consequently narrower than the proposition that organizations overcome power politics. Where governments possess overlapping interests, institutions can change information, incentives, and the consequences of repeated interaction in ways that help cooperation persist (Keohane, 1984). Their explanatory importance lies in showing why similar distributions of material power need not always produce identical patterns of interstate cooperation.
7. Liberalism vs Realism
Comparisons between liberalism and realism often reduce the disagreement to cooperation versus conflict. That is too crude. Realist theories allow for cooperation, while liberal theories recognize rivalry, coercion, and war. One of the most influential contrasts concerns which variables receive explanatory priority: international structure and material capabilities on one side, and domestic preferences, political institutions, economic relations, or institutionalized cooperation on the other.
Realism is itself internally diverse. Classical realism, structural realism, and neoclassical realism differ in important respects, while offensive and defensive realism developed largely as competing variants within the structural-realist tradition. The comparison with liberalism must consequently identify the realist theory involved rather than attributing every systemic argument to realism as a whole (Waltz, 1979).
Many contemporary liberal theories also recognize constraints created by power and international structure. Their distinctive contribution is to identify additional sources of variation. Governments occupying comparable strategic positions may value different outcomes because their domestic constituencies, economic interests, political institutions, and external relationships differ. Liberalism and realism thus overlap on some problems while offering different accounts of where state behavior originates.
7.1 Liberalism and Structural Realism
Structural realism provides the clearest systemic comparison. Waltz's theory explains recurrent features of international politics through anarchy and the distribution of capabilities, deliberately abstracting from much of the internal variation among states (Waltz, 1979). Domestic institutions and ideologies may affect foreign policy, but they are not the principal variables in a structural explanation of international outcomes.
Preference-based liberal theory reverses the analytical sequence. Rather than assuming that state objectives can be treated as given for systemic analysis, it asks how those objectives are formed. Social interests and the institutions of political representation shape state preferences, which subsequently interact with those of other governments (Moravcsik, 1997). Similar external pressures can thus produce different policies when states seek different outcomes.
The contrast is one of explanatory emphasis rather than mutually exclusive subject matter. Structural realism is designed to identify constraints generated by relative capabilities and the organization of the international system. Liberal theories become particularly useful when variation in preferences, institutions, or economic relationships helps explain behavior that systemic position alone leaves indeterminate.
7.2 Relative Gains and Institutional Cooperation
The neorealist–neoliberal institutionalist debate narrowed earlier differences because both approaches frequently modeled rational states pursuing their interests under anarchy. Disagreement centered on the obstacles to cooperation and the degree to which institutions could mitigate uncertainty, opportunism, and distributional conflict (Baldwin, 1993).
Relative gains became a central realist concern. A government may hesitate to accept a mutually beneficial agreement when another state receives substantially larger gains that could later strengthen its political or military position (Grieco, 1988). The intensity of that concern varies with strategic circumstances. Where gains can readily be converted into capabilities and the parties view one another as security competitors, relative position becomes more consequential than it is in relationships carrying limited security externalities (Powell, 1991).
Institutionalists give greater weight to conditions under which absolute gains remain politically achievable. Information, monitoring, reciprocity, and repeated interaction can reduce some barriers to cooperation when interests overlap (Keohane, 1984). This was a specific debate between closely related rationalist theories, not a complete definition of either realism or liberalism.
8. The Scope and Limits of Liberal Explanations
Liberal theories are most useful when treated as distinct causal explanations rather than as a single prediction of increasingly peaceful international politics. Democratic peace, preference formation, commercial interdependence, and institutional cooperation operate through different mechanisms. Evidence supporting one mechanism cannot simply be transferred to the others.
Their effects also depend on identifiable conditions. Political representation can transmit preferences for confrontation as well as cooperation because liberal theory does not assume that social interests are inherently pacific (Moravcsik, 1997). Economic ties can restrain conflict while generating vulnerabilities, and institutions are more capable of facilitating agreements where governments already possess some compatible interests than of resolving fundamental disputes over security or political survival (Keohane, 1984).
Methodological problems further complicate claims of causation. Associations between institutions, commerce, democracy, and cooperation may reflect factors that also influence which states enter those relationships. Democratic-peace research illustrates the difficulty particularly well: the empirical association between joint democracy and lower conflict remains substantial, yet scholars continue to test whether unobserved characteristics could account for it. Recent sensitivity analysis suggests that unusually strong confounding would be required to eliminate the observed relationship, without resolving which causal mechanism is decisive (Imai and Lo, 2021).
The appropriate test for liberal explanation is consequently comparative. A strong liberal argument must show that preferences, domestic institutions, interdependence, or international rules account for meaningful variation beyond what structural incentives alone predict. Continued warfare or coercion does not by itself invalidate liberal theory; the relevant question is whether the proposed liberal mechanism operates under the conditions specified by the theory.
9. Liberal Theory and the Liberal International Order
Liberal IR theory should not be equated with what scholars describe as the liberal international order. The concept itself is contested: accounts differ over its geographical scope, institutional components, historical starting point, degree of liberalism, and dependence on American power. Much of the influential literature initially described a U.S.-led Western order constructed after 1945 rather than a uniformly liberal global system (Deudney and Ikenberry, 1999; Ikenberry, 2001).
Within that Western order, the United States possessed exceptional economic and military preponderance relative to its allies and exercised substantial influence over postwar economic and security arrangements. Bretton Woods institutions, the General Agreement on Tariffs and Trade, and American alliance systems developed alongside increasing economic openness and institutionalized cooperation. The wider international system remained strategically bipolar during the Cold War and included communist states, nonaligned states, colonial empires undergoing dissolution, and newly independent states whose relationship to the Western order varied considerably.
The United Nations also requires separate treatment. It formed part of the broader post-1945 international architecture and embodied rules and institutions of near-universal aspiration, but it was not simply another component of the U.S.-led Western economic and alliance system. Its Security Council institutionalized a privileged position for five permanent members, including both the United States and the Soviet Union, illustrating how postwar institutional design combined multilateral rules with explicit great-power hierarchy.
Liberal and realist interpretations capture different features of these arrangements. Ikenberry argues that institutions can allow powerful states to make commitments more credible, exercise strategic restraint, and create orders that are more durable than purely coercive settlements (Ikenberry, 2001). Realist criticism places greater weight on underlying power and common interests and questions how much independent influence institutions retain when major states' interests diverge sharply (Mearsheimer, 1994/95). The postwar order is consequently better understood as a historical configuration in which power, institutions, economic relationships, alliances, and domestic political support interacted rather than as straightforward confirmation of a single theory.
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Conclusion
Liberal theories in International Relations explain why international behavior cannot always be derived from anarchy and material capabilities alone. State preferences emerge from different social and political settings; economic relationships alter incentives and vulnerabilities; regime characteristics can influence relations between governments; and institutions can change the conditions under which repeated cooperation occurs.
Their explanatory force is conditional. No single liberal mechanism establishes that international politics moves steadily toward peace, and the strongest liberal research programs specify the circumstances under which domestic preferences, interdependence, democracy, or institutions affect state choices. This conditional character is a theoretical strength when it produces testable explanations rather than assumptions about political progress.
Liberalism remains central to International Relations because it identifies sources of variation that purely systemic accounts cannot always capture. Its enduring contribution is not a prediction that power politics will disappear, but an explanation of how political representation, economic relationships, and institutional arrangements can change the interests states pursue, the constraints they encounter, and the ways in which power is exercised.
References
Axelrod, R. and Keohane, R.O. (1985) ‘Achieving cooperation under anarchy: strategies and institutions’, World Politics, 38(1), pp. 226–254.
Baldwin, D.A. (ed.) (1993) Neorealism and Neoliberalism: The Contemporary Debate. New York: Columbia University Press.
Carr, E.H. (1939) The Twenty Years’ Crisis, 1919–1939: An Introduction to the Study of International Relations. London: Macmillan.
Copeland, D.C. (1996) ‘Economic interdependence and war: a theory of trade expectations’, International Security, 20(4), pp. 5–41.
Covenant of the League of Nations (1919) adopted in Paris on 28 April 1919; incorporated as Part I of the Treaty of Versailles, signed 28 June 1919; entered into force 10 January 1920. League of Nations Official Journal, 1st year, No. 1, February 1920, p. 3. Available at: https://history.state.gov/historicaldocuments/frus1919Parisv13/ch10subch1 (Accessed: 5 August 2026).
Deudney, D. and Ikenberry, G.J. (1999) ‘The nature and sources of liberal international order’, Review of International Studies, 25(2), pp. 179–196.
Doyle, M.W. (1983a) ‘Kant, liberal legacies, and foreign affairs’, Philosophy & Public Affairs, 12(3), pp. 205–235.
Doyle, M.W. (1983b) ‘Kant, liberal legacies, and foreign affairs, Part 2’, Philosophy & Public Affairs, 12(4), pp. 323–353.
Farrell, H. and Newman, A.L. (2019) ‘Weaponized interdependence: how global economic networks shape state coercion’, International Security, 44(1), pp. 42–79.
Grieco, J.M. (1988) ‘Anarchy and the limits of cooperation: a realist critique of the newest liberal institutionalism’, International Organization, 42(3), pp. 485–507.
Ikenberry, G.J. (2001) After Victory: Institutions, Strategic Restraint, and the Rebuilding of Order after Major Wars. Princeton, NJ: Princeton University Press.
Ikenberry, G.J. (2009) ‘Liberalism in a realist world: international relations as an American scholarly tradition’, International Studies, 46(1–2), pp. 203–219.
Imai, K. and Lo, J. (2021) ‘Robustness of empirical evidence for the democratic peace: a nonparametric sensitivity analysis’, International Organization, 75(3), pp. 901–919.
Kant, I. (1795) Zum ewigen Frieden: Ein philosophischer Entwurf. Königsberg: Friedrich Nicolovius.
Keohane, R.O. (1984) After Hegemony: Cooperation and Discord in the World Political Economy. Princeton, NJ: Princeton University Press.
Keohane, R.O. and Nye, J.S. Jr. (1977) Power and Interdependence: World Politics in Transition. Boston, MA: Little, Brown.
Krasner, S.D. (1982) ‘Structural causes and regime consequences: regimes as intervening variables’, International Organization, 36(2), pp. 185–205.
Layne, C. (1994) ‘Kant or cant: the myth of the democratic peace’, International Security, 19(2), pp. 5–49.
Maoz, Z. and Russett, B. (1993) ‘Normative and structural causes of democratic peace, 1946–1986’, American Political Science Review, 87(3), pp. 624–638.
Mearsheimer, J.J. (1994/95) ‘The false promise of international institutions’, International Security, 19(3), pp. 5–49.
Moravcsik, A. (1997) ‘Taking preferences seriously: a liberal theory of international politics’, International Organization, 51(4), pp. 513–553.
Oneal, J.R. and Russett, B. (1999) ‘The Kantian peace: the Pacific benefits of democracy, interdependence, and international organizations, 1885–1992’, World Politics, 52(1), pp. 1–37.
Polachek, S.W. (1980) ‘Conflict and trade’, Journal of Conflict Resolution, 24(1), pp. 55–78.
Powell, R. (1991) ‘Absolute and relative gains in international relations theory’, American Political Science Review, 85(4), pp. 1303–1320.
Rosato, S. (2003) ‘The flawed logic of democratic peace theory’, American Political Science Review, 97(4), pp. 585–602.
Russett, B.M. and Oneal, J.R. (2001) Triangulating Peace: Democracy, Interdependence, and International Organizations. New York: W.W. Norton.
Waltz, K.N. (1979) Theory of International Politics. Reading, MA: Addison-Wesley.
Wilson, P. (1998) ‘The myth of the “First Great Debate”’, Review of International Studies, 24(5), pp. 1–16.
Wilson, W. (1918) ‘Address of the President of the United States delivered at a joint session of the two Houses of Congress’, 8 January 1918, Papers Relating to the Foreign Relations of the United States, 1918, Supplement 1, The World War, Volume I. Washington, DC: U.S. Department of State. Available at: https://history.state.gov/historicaldocuments/frus1918Supp01v01/d5 (Accessed: 8 August 2026).
