Liberal international relations (IR) theory is related to, but distinct from, the utopianism of the interwar period. The utopians believed that war could be eliminated either by perfecting man or by perfecting government. The roots of modern liberal international relations theory can be traced back farther than utopianism to Immanuel Kant’s essay Perpetual Peace (1795) (and arguably farther; see Kant 2003 under Immanuel Kant). In that essay Kant provided three “definitive conditions” for perpetual peace, each of which became a dominant strain of post–World War II liberal IR theory. Neoliberal institutionalism (also called “neoliberalism” or “institutional liberalism”) emphasizes the importance of international institutions (Kant’s “federation of free states”) in maintaining peace. Commercial liberalism emphasizes the importance of economic interdependence and free trade (Kant’s “universal hospitality”) in maintaining peace. Democratic peace theory argues that democracies rarely, if ever, go to war with each other, and thus an executive accountable to the people or the parliament is important to maintain peace (Kant’s call for all states to have “republican constitutions”). There are other forms of liberal IR theory that are not explicitly dealt with in this article, such as functionalism and neofunctionalism, for example. For the purposes of a broad overview of the theory, only the predominant strains of liberal IR theory are included. Earlier generations of scholars refer to liberalism as “idealism.” More recent scholarship uses “idealism” to refer to “utopianism” or even “constructivism.” However, all postwar liberal theories share a few basic concepts that allow them to be called “liberal”: (1) states are the primary actors in the international system, but they are not unitary—domestic politics matters; (2) there are factors beyond capabilities that constrain state behavior; and (3) states’ interests are multiple and changing. The key concepts found in liberal theory are absolute gains, international institutions, free trade, and democracy. International law is also important in liberal IR theory as it is seen as forming a major constraint on state behavior. Particular international institutions are also important in the development of liberal IR theory, but they are not explicitly dealt with in this article. Liberal IR theory is a particularly Western-focused theory that deals with the advantages, limitations, and exportability of typically Western forms of government. Thus, American and English sources dominate this article. It could be argued that the “English school” belongs here, but the placement of the English school in solely a realist, liberal, or constructivist framework could be considered quite controversial, as its locus within IR theory is contested. Therefore, the English school is dealt with in the “International Relations Theory” article, and more extensively in the “International Society” article.
This section contains overviews of liberal IR theory as a whole, as well as particularly important aspects of liberal IR theory. Snyder 2004 provides the most basic overview of liberal theory and contrasts it with realism and constructivism. Williams, et al. 2006 is an excellent collection of excerpts from major liberal works, though it is not limited to liberal theory. For an in-depth discussion of liberalism, accessible for the undergraduate, see Richardson 2001. Doyle 1986 provides an article-length overview of liberal theory and its influence on foreign affairs. Moravcsik 1997 is a lengthy discussion of what liberal theory is, and in it Moravcsik differentiates liberal theory from “neoliberal theory.” Putnam 1988 shows that both domestic politics and international politics affect policy outcomes. Milner 1991 effectively justifies liberal theory by arguing that the basic assumption of an anarchic international system is flawed. Oye 1986 is an edited volume that contains the work of major scholars on how cooperation under anarchy, a lynchpin of liberal IR theory, is possible.
Doyle, Michael W. “Liberalism and World Politics.” American Political Science Review 80.4 (December 1986): 1151–1169.
An accessible and heavily cited work from one of the originators of modern liberal theory. Doyle examines Schumpeter, Machiavelli, and Kant and finds that liberal states are somehow different in foreign affairs. He argues that there is both liberal pacifism and liberal imperialism, and that they are rooted in different conceptions of man versus the state. Provides a good overview of liberal theory.
Milner, Helen. “The Assumption of Anarchy in International Politics: A Critique.” Review of International Studies 17.1 (January 1991): 67–85.
Argues that the basic realist assumption of anarchy is flawed. Examines different conceptions of anarchy to show that there is disagreement among realists on the very definition of the term; then questions the realist separation of domestic and international politics.
Moravcsik, Andrew. “Taking Preferences Seriously: A Liberal Theory of International Relations.” International Organization 51.4 (September 1997): 513–553.
Moravcsik formulates a theory that is different from both utopianism and the (neoliberal) institutionalism of Robert Keohane. Starts from the position that domestic factors shape international relations. Important to any understanding of liberal theory. For the advanced undergraduate or above. Cited by nearly a thousand other articles and books.
Oye, Kenneth A., ed. Cooperation under Anarchy. Princeton, NJ: Princeton University Press, 1986.
An edited volume devoted to explaining how cooperation can occur even in anarchic situations. Some of the most eminent names in the field contribute chapters, including Robert Jervis, Duncan Snidel, Charles Lipson, Stephen Van Evera, and Robert Axelrod and Robert Keohane.
Putnam, Robert D. “Diplomacy and Domestic Politics: The Logic of Two-Level Games.” International Organization 42.3 (June 1988): 427–460.
A wide-ranging discussion of the relationship between domestic and international politics. Putnam uses a range of cases to show just how linked the domestic and international “games” really are. Incredibly influential article, cited by over 3,500 other sources.
Richardson, James. Contending Liberalisms in World Politics: Ideology and Power. Boulder, CO: Lynne Rienner, 2001.
A history and overview of liberal theories within IR. Richardson critiques neoliberalism from a liberal standpoint and argues for a less destructive liberal foreign policy. Somewhat obscure, but a useful text for anyone studying liberal theory.
Snyder, Jack. “One World, Rival Theories.” Foreign Policy 145 (November/December 2004): 52–62.
An update on a similarly named 1998 Foreign Policy article by Stephen Walt. Snyder provides his take on the basic principles of liberalism and compares them to the basic principles of the other major schools of thought in international relations theory. Perfect brief overview of both liberalism and international relations theory in general.
Williams, Phil, Donald M. Goldstein, and Jay M. Shafritz, eds. Classic Readings and Contemporary Debates in International Relations. Belmont, CA: Wadsworth, 2006.
Not limited to liberalism. An anthology of edited selections from major theoretical works, including works by Doyle, Keohane, Wilson, Claude, Hoffman, and many others listed in this article. An excellent one-stop shop for an overview of liberalisms of all stripes.
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