Show Summary Details

Page of

PRINTED FROM the OXFORD RESEARCH ENCYCLOPEDIA, POLITICS ( (c) Oxford University Press USA, 2018. All Rights Reserved. Personal use only; commercial use is strictly prohibited. Please see applicable Privacy Policy and Legal Notice (for details see Privacy Policy and Legal Notice).

Subscriber: null; date: 20 January 2019

Theoretical Diversity in International Relations: Dominance, Pluralism, and Division

Summary and Keywords

The question of theoretical dominance has been the source of longstanding debates in the field of International Relations (IR). The folklore of the field tells of how realism fell from dominance and was replaced by liberalism in the 1990s. The systematic evidence, however, shows that neither theory was as dominant as many claimed. While the early period of postwar IR was dominated by realism, the past 35 years can be characterized by its plurality of theories. This plurality of theories, however, may not reflect a diverse field. Diversity denotes some degree of variation within an interacting community or system. Meaningful interactions between distinct research sects in IR appear to be very rare, as characterized by the so-called paradigm wars. Instead of a diverse field, IR may be characterized as insular, Balkanized sects that are hostile to differing theories and approaches.

Keywords: theoretical diversity, theoretical dominance, normal science, realism, liberalism, constructivism, paradigm wars, empirical international relations theory


Five distinct claims have frequently been echoed regarding theoretical diversity and dominance in the field of International Relations (IR). The first is that realism has been and remains the dominant, if not oppressive, paradigm. Steve Smith (2000, p. 379), for instance, claimed that the “approach that dominated the discipline of IR has, of course, been realism.” For Smith, not only does realism dominate, but it constitutes a form of “intellectual imperialism.” And like any imperial power, realism does not play nicely with its rivals. A second view maintains that liberalism—not realism—is the dominant and oppressive paradigm. Jennifer Sterling-Folker (2015, p. 46) argued that “as the discipline’s dominant discourse, liberalism delimits the boundaries of the theoretical ferment engaged by the rest of us.” Liberal IR theory, according to Sterling-Folker, “should be hailed as the subjugating, repressive discourse it is and has been for some time.” A third view casts the field as a duality between liberalism and realism. Joel Rosenthal (1995, p. 317) concluded that international relations over “the past fifty years is an unwitting and curious combination of [liberal and realist] approaches.” A fourth view is one of theoretical diversity, as indicated in The Oxford Handbook of International Relations, edited by Christian Reus-Smit and Duncan Snidal (2008). In the section on IR’s “Major Theoretical Perspectives,” at least one chapter is devoted to 11 distinct theories: realism, liberalism, Marxism, neo-liberal institutionalism, new liberalism, the English school, constructivism, critical theory, postmodernism, feminism, and eclectic theorizing. Fifth and finally, Maliniak, Oakes, Peterson, and Tierney (2011, p. 439) questioned the importance of any broad research paradigms in the study of IR. They reported that much of the research in IR does not “fit neatly within one of the major paradigms . . . the percentage of non-paradigmatic research has steadily increased, from 30% in 1980 to 50% in 2006.” This fifth view coincides with Katzenstein and Sil’s (2008) endorsement of eclectic problem-solving. These five diverging views of theoretical diversity in IR warrant a closer analysis of this question.

Since questions of theoretical diversity and dominance will define any discipline, they have fueled long-standing debates among philosophers of science. Perhaps the most famous exchanges regarding theoretical pluralism and diversity in scientific communities took place between Karl Popper and Thomas Kuhn. Imre Lakatos (1970, p. 93) noted how “the clash between Popper and Kuhn is not about a mere technical point in epistemology. It concerns our central intellectual values.” For Popper, theoretical diversity is essential for rational criticism and for advances in knowledge. Popper (1994, p. 143) emphasized how fruitful discovery in all fields, including social science, depends on keeping “the flow of ideas running from all tributaries.” In Popper’s view (1994, p. 35), the most effective way of expanding our knowledge is by frequent intellectual exchanges “between vastly different frameworks.” These exchanges may be “extremely difficult, and perhaps not quite so pleasant (though we may learn to enjoy it).” Popper viewed theoretical pluralism—his open society—as the driving force in the growth of knowledge.

Thomas Kuhn’s widely-read Structure of Scientific Revolutions posed many challenges to Popper’s theoretical pluralism. The debate has often been cast as one between Popper the libertarian vs. Kuhn the authoritarian (Fuller, 2004, pp. 8–9). Kuhn argued that efficient productivity of a scientific community requires a single, authoritative paradigm or theoretical framework. Normal science, Kuhn’s term for a research community dominated by one paradigm, is characterized by narrow theoretical rigidity. Kuhn (1970a, p. 24) noted that scientists typically do not “invent new theories [and] they are often intolerant of those invented by others . . . No part of the aim of normal science is to call forth new sorts of phenomena; indeed those that will not fit in the box are often not seen at all.” Kuhn’s concept of incommensurability reflects a scientific community that is unable—or unwilling—to engage with those outside the box—the dominant paradigm. Kuhn’s (1970a, pp. 64–65) normal science leads to “an immense restriction of the scientist’s vision and to a considerable resistance to paradigm change.” But, Kuhn added, “normal science leads to a detail of information and to a precision of the observation-theory match that could be achieved in no other way.” Normal science is a “highly cumulative enterprise” resulting in “the steady extension” of scientific knowledge (Kuhn, 1970a, p. 52). While Kuhn’s depiction of normal science can be narrow and limiting, even repressive and authoritarian, reliance on one paradigm may be the most efficient way to ensure progressive problem solving. It should also be noted that Kuhn studied the natural sciences and scoffed at any efforts to apply his ideas to the social sciences. However, this has not discouraged scholars of IR and other social sciences from appropriating ideas of normal science, in spite of Kuhn’s protestations (Walker, 2010, pp. 433–434).

In the study of IR, the Kuhn–Popper debate is played out over questions of realism and its dominance. Many still endorse Smith’s view that the theory of political realism constitutes, or once constituted, the dominant paradigm. Here, the discipline of IR is cast as a normal science, a regime ruled by the dominant paradigm of realism that ignores, if not suppresses, alternative theories and approaches. This fits Kuhn’s (1970a, p. 24) normal science as a practice where the dominant paradigm is hostile and intolerant toward anything that “does not fit in the box.” Others, as indicated by the Reus-Smit and Snidal (2008) edited volume, depict IR as a field with multiple theories. This view of IR corresponds to Popper’s open society of theoretical pluralism. Arguments over theoretical dominance have fueled the so-called “paradigm wars” that often restrict interparadigm dialogues in IR and may hamper progress (Lake, 2011; Ferguson, 2015). These “wars” or contending claims of theoretical dominance in IR represent a classic example of a long argument that is short on systematic evidence. This chapter will review the systematic evidence regarding theoretical dominance and diversity in IR with a special emphasis on data-based, empirical studies. We begin by distinguishing empirical theories like liberalism and realism from approaches like constructivism and game theory. We then turn to a review of the first two “great debates” in IR. These debates provide a general and stylized representation of the enduring contests for theoretical and methodological dominance of IR. Next we examine the systematic studies that seek to identify theoretical orientations of published research over the past fifty years. While the early period of postwar IR was dominated by realism, the past 35 years can only be characterized by a plurality of theories. This plurality of theories, however, may not reflect a diverse field. Diversity denotes some degree of variation within an interacting community or system. Meaningful interactions between distinct research sects in IR appear to be very rare. In the conclusion we speculate how the intensity and language of the so-called paradigm wars are a curious reflection of concepts central to the study of IR.

Distinguishing Empirical Theories From Approaches and Methods

Before addressing questions of theoretical dominance in IR, we must be explicit on how theory is defined and how theory is distinct from method or approach. More than 50 years ago Anatol Rapoport (1958) highlighted the “various meanings of theory” in the American Political Science Review. For a volume devoted to empirical theory of IR, we will restrict our use of theory to those which yield empirical, testable claims and predictions. But given the broad and multiple ways in which the term theory is being deployed in IR, some clarification is in order.

At its most basic level, theory provides a vision that simplifies. This aspect of theory can be gleaned from the Greek origins of the word. Related to the Greek theos for god, theory might be associated with divine order as well as mortal speculations about such an order. More simply, by combining theos (god) with oro (to see), theory might be translated as a mortal’s vision of or from god. Theory will reflect not only an ordered world view but an ideal, if not divine, world view. Theories are visions that help focus and organize the complexity of the world.

Kenneth Waltz (1979, p. 8) famously defined “theory as a picture, mentally formed, of a bounded realm or domain of activity . . . A theory indicates that some factors are more important than others and specifies relations among them.” A theory’s usefulness will be “judged by the explanatory and predictive powers of the theory.” For Waltz (1979, p. 17), “to proceed by looking for associations without at least some glimmering of a theory is like shooting a gun in the general direction of an invisible target.” Empirical theories in IR serve as essential guides for organizing and specifying claims regarding global politics. Along these lines, empirical theory can be thought of as a logically coherent intellectual contemplation that explains and simplifies a more complex whole by breaking it down into more manageable—and testable—questions.

While empirical theory helps us focus our visions and render testable claims about how the world may work, methods and approaches provide procedures to assess and evaluate these claims. In other words, a theoretical framework provides an idealized picture of one slice of the world for the researcher by identifying certain puzzles, possibilities, and expectations. A method or an approach—whether it be a formal deductive model, a historical case study, a large-n study, or a constructivist analysis—provides a way of pursuing answers to those questions. Approaches like constructivism and game theory are vacant without a theoretical framework or vision guiding their application. Even simple game-theoretic models, like the most basic hypothesis, could not be attempted without some theoretical insight as to actors, their supposed preferences, and key variables. To put it differently, game theory can be used to model the growing significance of the United Nations just as it can be used to model coercive diplomacy or the balance of power. In the first case, the model is informed by a liberal theoretical framework, while the second is informed by realism. All methods and approaches are contingent upon but distinct from empirical theory.

This restrictive definition is at odds with the current and ever-expanding uses of theory in IR. Methods, approaches, and schools of thought are frequently referred to as theories, as in the cases of constructivism and the English School in Reus-Smit and Snidal (2008). Constructivism is perhaps the most prominent approach that is frequently referred to as a theory. Many leading textbooks will focus on three major theories—realism, liberalism, and constructivism (see, for instance, Nau, 2017; Mingst & Arreguin-Toft, 2017). A few, however, have acknowledged how constructivism is an approach that can serve to complement different empirical theories. For instance, Finnemore and Sikkink (2001, p. 393) noted that “Constructivism is a different kind of theory from realism, liberalism, or Marxism and operates at a different level of abstraction. Constructivism is not a substantive theory or politics . . . Constructivism in this sense is similar to rational choice.” Constructivism as an approach rather than a theory becomes apparent when Stephen Walt (1998, p. 38, Figure 1) presents his “Post-Cold War Predictions” from three competing theories. While Walt considers constructivism a theory like realism and liberalism, the lack of any predictive capacity sets constructivism apart from substantive theories of IR. Realism, according to Walt, predicts a “resurgence of overt great power competition” in the post-Cold War world. Liberalism predicts “increased cooperation as liberal values, free markets, and international institutions spread.” Constructivism, on the other hand, is “agnostic because it cannot predict the content of ideas.” In short, an empirical theory of IR must yield rudimentary claims, expectations, and predictions that are amenable to some level of empirical scrutiny. From a broad vision of realism, basic claims regarding balancing, relative power, and the consequences of balances—or imbalances—of power can be discerned. From a broad vision of liberalism, claims regarding the importance of democracy, trade, and international organizations can be identified and empirically examined. Constructivism offers nothing like these claims. While extremely useful for understanding the role of ideas in global politics, constructivism is not a theory like realism, liberalism, Marxism, or other visions of how the world may work because it generates no unique and testable claims, predictions, or explanations. Chris Brown (2013, p. 490) makes the point succinctly: “Constructivism is not a theory of IR in the sense that liberalism and realism are theories of IR—rather, it is a set of dispositions towards social reality.” So equating constructivism with theories like realism and liberalism will confuse efforts to evaluate questions of theoretical diversity in IR.

The “Great” Debates Over Dominance and Diversity in IR

Discussions of diverse approaches in the discipline of IR typically begin with the two so-called great debates over theory and over method. These two debates, often oversimplified but still useful, represent enduring schisms in the discipline. These debates set the scene and the tone of subsequent polemics and are therefore worth revisiting. The “first debate” was between realism and liberalism—which was often and incorrectly referred to as idealism or utopianism. Many of the early classics of IR navigate this dichotomy between realism and liberalism (Carr, 1946; Morgenthau, 1948). In the mid-1960s Stanley Hoffmann (1965, p. 86) noted how international relations has been “a kind of permanent dialogue between Rousseau and Kant.” Hoffmann cast Rousseau as the realist. Realism can be traced from Thucydides, Machiavelli, and, arguably Rousseau and on to Morgenthau and Waltz in the 20th century. Realists emphasize the anarchic nature of the international system where states cannot be certain of their rivals’ intentions. As a result of this uncertainty in anarchy, “three general patterns of behavior result: fear, self-help, and power maximization” (Mearsheimer, 2001, p. 32). Liberalism offers a more optimistic and progressive view of world politics and can be traced back to the Enlightenment liberals like Thomas Paine and Immanuel Kant. Contrary to realists, liberal theorists posit that international peace and security will increase with democracy, free trade, and membership in international organizations. Russett and Oneal (2001) refer to this as the liberal or Kantian tripod of peace. Hoffmann’s permanent dialogue between realists and liberals constitute the so-called first debate in the study of IR.

The “second debate” in IR was one over the methods most appropriate for the study of world politics. This debate arose in the 1960s during the behavioral revolution, when traditional scholars felt threatened by what they saw as a new methodological, hegemonic force emerging. This second debate over “isms” pitted behavioralist methods against traditionalist methods. Behavioralism sought to discover general trends in world politics through systematic collection of empirical data across a large number of cases, rigorous hypothesis testing, and the use of scientific methods. Behavioralism’s rise as a leading method was challenged by traditional scholars like Hedley Bull. Bull (1966, p. 361) celebrated the classical “approach to theorizing that derives from philosophy, history, and law, and that is characterized above all by explicit reliance upon the exercise of judgment.” David Singer (1969), from the vanguard of the behaviorists, responded with a careful critique in his essay, “The Incompleat Theorist: Insight Without Evidence.” The Bull-Singer exchange brought focus to the second debate. While any meaningful overview of the Bull-Singer debate is beyond the scope and space of this chapter, one point is of particular relevance here.

The fierce and uncompromising positions maintained by both sides were distinctive aspects of the second debate. Set in the midst of the Cold War, the rivalry between the traditionalists and the scientifically-minded mimicked the conflict that both studied. In many ways, the second debate was the first “paradigm war” in the discipline of IR. Both sides envisioned the debate as one where the victor would certainly marginalize the vanquished. The outcome of this debate, Bull (1966, p. 377) noted in his conclusion, would determine the “hierarchy of academic priorities.” He warned how “the distinctive methods and aspirations” that these social scientists have brought to IR “are leading them down a false path, and to all appeals to follow them down it we should remain resolutely deaf.” Any effort to engage, to understand, or even to listen to the opposition would lead scholars “down a false path.” Ironically, much like Kuhn’s normal scientists, Bull called upon “classical” IR scholars to ignore or to demonstrate hostility toward opposing methods. Bull’s advice to remain resolutely deaf to opposing approaches has come to characterize subsequent debates in IR. These include the “Third Debate” over positivism and postpositivism (Lapid, 1989) as well as the ensuing debates involving constructivism, reflectivism, and feminism, among others. These divides are often reified by turning a deaf ear to any differing voices.

Realism and Its Theoretical Dominance, 1948–1970

By all accounts, the first debate ended with a unanimous victory for realism. In the years following World War II, realism dominated the field. Hans Morgenthau’s (1948) classic realist text, Politics Among Nations, enjoyed unparalleled popularity. The book underwent seven editions in Morgenthau’s lifetime and is still in print. William Scheuerman (2009, p. 102) noted that Morgenthau’s book was adopted in more classrooms in the 1950s than all other texts combined and it “singlehandedly initiated many generations of US international relations students into the field.” Stanley Hoffmann (1977, p. 44) concluded that “If our discipline has a founding father, it is Morgenthau.” And by corollary, if IR has a founding theory, it is realism. John Vasquez (1983) referred to Morgenthau’s work as a Kuhnian exemplar that would shape IR into a normal science that focused on testing realist hypotheses. When asked about the viability of alternative theories to neorealism—a systematic variation of Morgenthau’s realism, Kenneth Waltz (1998, p. 383) responded: “I wish there were. I just don’t know of any other theories.” For Waltz, realism is dominant and towers over all other theoretical frameworks in international relations. More recently, William Wohlforth (2008, p. 131) argued that “the academic study of international relations is a debate about realism. Realism provides a foil against which many other schools of thought define themselves and their contributions.” Discussions of theoretical diversity and dominance in IR will typically begin with some discussion of realism.

Rigorous and systematic evaluations of the scope and extent of this realist dominance have, however, been slow to emerge. Ole Waever (1998, p. 692) claimed that “articles on the history of the discipline, slowly growing in number, are usually not based on systematic research or clear methods. They are, at best, elegant restatements of ‘common knowledge’ of our past.” However, Waever added, “without looking systematically at the past, we tend to reproduce myths.” The first effort to systematically measure realism’s dominance in the field was Vasquez’s (1983) comprehensive study, The Power of Power Politics. Vasquez demonstrated how core realist concerns influenced concept formation, data-making efforts, hypothesis testing, and the vast majority of quantitative studies in IR. Vasquez (1983) drew his inferences from coding data-based works addressing international politics compiled by Jones and Singer (1972). He coded hypotheses from these articles as either realist or non-realist in their theoretical orientation. He identified realist hypotheses by three features recurrent in Morgenthau’s Politics Among Nations, namely, primacy of the state, a clear divide between domestic and international politics (i.e., order vs. anarchy), and the struggle for power. Relying on this dichotomous distribution, Vasquez reported that the realist paradigm has generated the overwhelming majority of hypotheses tested in data-based work. Indeed, more than 90% of data-based hypothesis testing published in IR up to 1970 were considered realist. He also claimed that realism has fared very poorly in explaining international politics. Realist hypotheses, according to Vasquez, have consistently failed to be empirically corroborated. Non-realist hypotheses, on the other hand, were more likely to be statistically significant.

Vasquez’s findings were widely discussed by a diverse group of scholars. The first edition was lauded by J. David Singer as “a very useful examination of our discipline’s intellectual history and development [that] will fill a major gap in the literature.” Perhaps the warmest reception came from non-quantitative scholars in Britain. From the London School of Economics, Michael Banks pronounced the book “an obvious classic.” In an extensive review article, Banks (1985) referred to Vasquez as “a scholar’s scholar, a source of authoritative reference.” Banks also claimed that Vasquez’s text may be “the most important single work to have emerged from the behavioural movement in international relations.” Vasquez’s findings were warmly embraced by those who sought to document realist dominance and oppression. For instance, Smith (2000) cited Vasquez as evidence to the “intellectual imperialism” perpetuated by realism. Banks (1990, p. 58) relied on Vasquez to support his claim that realism is “intellectually totalitarian” and ignores “the humanitarian breadth of the classic writers.” The view that a heavy reliance on realism leads IR scholars away from important ethical questions was made most prominently by Richard Ashley. The dominance of realist theory, according to Ashley (1986, p. 258), “neuters the critical faculties . . . limits rather than expands political discourse . . . [contributing to] an ideology that anticipates, legitimizes, and orients a totalitarian project of global proportions.”

The findings of Vasquez have been applied to the two so-called great debates in IR. First, on methodological grounds traced out in the second debate, these findings may be seen as a validation of Bull’s (1966, p. 377) claims that rigorous, scientific methods would lead scholars “down a false path.” Second, Banks, Smith, and others would often marshal Vasquez’s empirical findings to discredit the validity of realism and to potentially clear the way for other theoretical concerns. Sometimes scholars, like Smith and Banks, do both, with some logical inconsistency. They cite Vasquez’s empirical findings to critique both realist dominance and positivism without acknowledging the positivist, empirical foundations of Vasquez’s work.

In 1998 Vasquez published a second edition of The Power of Power Politics. This edition, however, did not update the exhaustive coding that characterized the first edition, which compiled hypotheses through the year of 1970. Instead, Vasquez looked to Waltz (1979) and other prominent post-1970 texts to demonstrate realism’s continued dominance of IR. In his second edition, Vasquez (1998, p. 183) reasserted that research over “the past fifteen to twenty years has convinced me more than ever of the tenacity of the [realist] paradigm’s grip on scholars, especially in the United States, and of the need to abandon it as a guide to both theory and practice.” While rich with insight on recent theoretical developments in the discipline, Vasquez’s systematic evidence of realism’s dominance concluded in 1970. Several subsequent studies demonstrate a marked decline in realism’s dominance in the years that followed 1970.

The Declining Importance of Realism and the Rise of Liberalism, 1971–2015

Walker and Morton (2005, 2016) extended Vasquez’s analysis of data-based articles in IR, examining the post-1970 period. Walker and Morton focused on data-based articles for several reasons. First, their findings would make the most fitting continuation and comparison to Vasquez’s findings. Second, with explicit, operationalized independent and dependent variables, coding the theoretical footings of articles can be completed with a higher degree of reliability. Third, the emphasis on data-based studies presents a most-likely case logic with realist theory. Many of the early data-making projects in IR, like the Correlates of War Project, revolved around measures of capabilities, alliances, militarized disputes, and war. Realism’s emphasis on states, power, conflict, arming, and alliances make data-based studies a most-likely population of cases for realist theory. If it could be shown that realism does not dominate data-based work in IR, it would be safe to conclude that realism does not dominate the field more broadly.

While Vasquez relied on a binary typology of realist versus non-realist articles, Walker and Morton (2005, 2016) expanded the typology to four theoretical possibilities: realist, liberal, three-cornered fights, and other (nonparadigmatic). When coding an article to be realist in its theoretical orientation, Walker and Morton adhered to the broad criteria set out by Vasquez: states, anarchy, and the struggle for power. As a result, articles employing variables on national material capabilities, weapons, arming, alliances, and coercive diplomacy were coded as realist. For their conceptualization of liberalism, Walker and Morton relied on Russett and Oneal’s (2001) triangle of the liberal peace composed of democracy, international trade, and international institutions. If studies explored the importance of democracy, trade, and international organizations as variables in international politics, they were coded as liberal. Walker and Morton’s third category, three-cornered fights, serves as a hybrid model where both realist and liberal claims will confront one another within the same article. Three-cornered fights, a term used by Imre Lakatos (1970), are studies whose central questions are rooted in contested conjectures from two theoretical frameworks and evaluated by one empirical test. A classic three-cornered fight would be when a study compares a realist independent variable like national capabilities to a liberal independent variable like democracy to the same dependent variable. Walker and Morton’s final category is a residual category that consists of data-based articles addressing issues such as Marxist-Leninist theory, dependency, terrorism, economic sanctions, foreign economic aid, diversionary theory, domestic politics—other than regime type—that shape foreign policies of states, and other questions that do not fit within the purviews of realism or liberalism.

In their original article, Walker and Morton (2005) coded 515 data-based articles published between 1970 and 2000. They selected their articles from the compilation of data-based research reported by Gibbs and Singer (1993). This compilation reports all the data-based studies in global politics from 1971 to 1991. For the post 1991 era, they coded articles from International Studies Quarterly, International Organization, Journal of Conflict Resolution, and World Politics. These four journals were selected using two criteria. First, they frequently publish data-based articles. Second, they were ranked most prominent journals in IR, according the Garand and Giles (2003). In their follow up, Walker and Morton (2016) relied exclusively on these four journals to identify and code 854 data-based articles from 2001–2015. From 1970–2015, Walker and Morton coded 1,369 data-based articles to discern their theoretical foundations.

Walker and Morton (2005) initially demonstrated a gradual decline in the percentage of articles informed by realist theory. Indeed, the years 1995–2000, the number of data-based liberal articles outnumbered realist articles for the first time. In these final years of the 20th century, liberal-informed data-based articles nearly twice as prominent as realist-informed articles, accounting for approximately 40% of articles published. Realist-informed articles approached 22% for the final years of the 20th century (Table 1).

Table 1. Theoretical Orientations of Data-Based Articles, 1970–2015 (Walker & Morton, 2016)








18 (48.64%)

9 (24.32%)

3 (8.1%)




29 (46.77%)

10 (16.12%)

8 (12.9%)

15 (24.19%)



37 (38.14%)

23 (23.71%)

12 (12.37%)

25 (25.77%)



30 (48.38%)

9 (14.06%)

10 (15.62%)

15 (23.43%)



36 (36%)

19 (19%)

13 (13%)

32 (32%)



34 (21.93%)

20 (12.90%)

61 (39.35%)

40 (25.80%)



22 (9.09%)

24 (9.92%)

83 (34.30%)

113 (46.69%)



21 (7.29%)

27 (9.37%)

131 (45.49%)

109 (37.85%)



39 (12.04%)

23 (7.10%)

164 (50.62%)

98 (30.25%)



266 (19.43%)

164 (11.98%)

485 (35.4%)

454 (33.2%)


Overall, the evidence presented by Walker and Morton’s two works indicates that realism is no longer the dominant theory in data-based articles. Instead, there is a healthy diversity of theoretical questions being tested by large-n data. Part of this transition away from a realist-dominant discipline is due to the rise of the democratic peace research program and other liberal concerns such as peace through trade and international organization. But the rise of studies in the residual/other category is also worth noting. Data-based studies that fall outside what Hoffmann termed the “permanent dialogue” between realism and liberalism have grown dramatically, increasing from 22 in the decade of the 1970s to more than 200 in the most recent ten year period. A large part of this is due to the increase in the absolute number of data-based articles published in IR. However, even proportionally, the number of non-realist and non-liberal data-based articles has increased dramatically. This evidence fails to support claims of a realist hegemony—or a liberal hegemony—in the study of IR. Instead, Walker and Morton reported that the data-based study of IR can be characterized by its diversity of theoretical questions. In the realm of data-based studies, long thought to be a bastion of realism, realist theory plays a diminishing role. Instead, a multitude of theoretical perspectives currently guide data-based research in IR.

Teaching, Research, and International Policy (TRIP) Project Findings

The TRIP Project represents the most comprehensive effort to study trends within the discipline. This project has compiled a wide array of survey data on attitudes of scholars of IR, as well as data collection on the types of research being published. The TRIP Project examined articles employing all methods and approaches published in the 12 leading journals from 1980 to 2007 (Maliniak et al., 2011). The project identified journals according to the impact factor reported by Garand and Giles (2003). They focus on both IR journals like International Studies Quarterly and leading political science journals that are not exclusively IR such as The American Political Science Review and the British Journal of Political Science. Their sample consists of 2,806 articles on IR, about 50% of all the articles published in these 12 journals over a 28-year period. TRIP categorized articles along six theoretical dimensions: Realist, Marxist, Liberal, Non-Paradigmatic, None, and Constructivist. In addition to identifying the theoretical orientation of journal articles along six categories, they also code for articles that pursue alternative explanations or rely on alternative paradigms, methodology, epistemology, time period, level-of-analysis, 18 possible issue areas, 15 regional foci, 33 possible substantive issues, and author’s affiliation (Peterson et al., 2013).

TRIP’s findings in regard to theoretical diversity in IR reflect those of Walker and Morton’s. TRIP also reported a steady increase in nonparadigmatic studies, or studies that fall outside the obvious paradigms. Evidence from the TRIP Project indicates that a great deal of the published articles in IR have been nonparadigmatic in that the authors do not advance, advocate, or are guided by realism, liberalism, or Marxism. Even within the American IR community, once thought to be a stronghold for realism and empiricism (Hoffmann, 1977), they report rampant theoretical diversity: “We find that there is considerable theoretical diversity within the American IR community and that diversity has grown over time . . . Indeed, the percentage of non-paradigmatic research has steadily increased, from 30% in 1980 to 50% in 2006” (Maliniak et al., 2011, p. 439). One concern with the TRIP typology is their inclusion of constructivism as a theory. As noted above, constructivism might be thought of as an approach rather than a distinct theory yielding concrete claims and predictions. Starting in the 1990s, Maliniak et al. (p. 445) reported a significant increase in the number of constructivist studies. With a constructivist approach applicable to both liberalism and realism (Barkin, 2003), the mounting number of constructivist articles may be drawn from studies that might otherwise be coded as liberal or realist.

TRIP’s findings on the diminished role of realism are particularly surprising, especially to those who envision a realist dominance. TRIP identified a smaller proportion of realist-informed articles compared to Walker and Morton (Maliniak et al., 2011, Figure 4). TRIP also reported the discrepancy between scholars’ perceptions of realist and liberal dominance in the literature and their coding of the literature. While scholars envisioned most research falling along realism, liberalism, and Marxism, the TRIP data on the theoretical orientations of articles did not bear this out. TRIP concluded that “realism does not have the hold on the field it often is thought to have and, perhaps more strikingly, our data suggest it never did” (Maliniak et al., 2011, p. 439). They go on to note that “research in the traditions of realism, liberalism, Marxism, and constructivism does not dominate the major peer-reviewed journals” (Maliniak et al., 2011, p. 460). While there are problems with a typology that equates constructivism with empirical theories, as noted above, the gist of TRIP’s findings challenge both historical narratives and current scholarly perceptions of the field.

While Walker and Morton’s studies of data-based articles indicate a greater emphasis on liberalism and realism than do the TRIP findings, this may be the result of different populations of articles. Large-n, data-based articles may be more constrained by existing data sets. And these data sets, like those found in the Correlates of War or the Polity Data, may be more likely to be influenced by the best-known theories of liberalism and realism. The NSF and other grant-giving entities often favor data-making proposals that are linked to larger theoretical frameworks. This makes the finding that 33% of data-based articles fall outside the domain of these theories an even greater testimony to theoretical diversity in the field. TRIP’s findings demonstrate an even higher proportion of articles that cannot be rooted to one of the leading theories. As a final point of emphasis, the findings of both TRIP and Walker and Morton suggest that there are wide-ranging and diverse theoretical movements afoot in the study of IR. This diversity is clear from the diverse publications in the leading journals. Claims of theoretical hegemony cannot be supported with the data at hand.


At the outset of this chapter, five views of dominance and diversity were discussed. The evidence reviewed here indicates that the theoretical visions guiding research in IR can be characterized as multiple and wide-ranging, along the lines presented by Reus-Smit and Snidal (2008). Realism is far from dominant. Liberalism is not dominant. Instead, an array of theoretical concerns are being explored and published across many different methods. Despite frequent references of a theoretical hegemon in the field, none can be detected.

These claims of theoretical and methodological pluralism, it should be noted, come exclusively from English language and largely American journals. Walker and Morton (2005, 2016) relied on data-based studies in four leading IR journals published in the United States. Maliniak et al. (2011) and the TRIP Project cast a wider net that included leading European based English-language journals like the Journal of Peace Research, British Journal of Political Science, and European Journal of International Relations. If multiple theories and methods are conspicuous in the narrows of Anglo-American IR, then recent moves toward a “Global IR,” one that recognizes non-Western theoretical and methodological approaches, may find its footing more readily (Acharya, 2016; Wemheuer-Vogelaar et al., 2016). Efforts to track the global dimensions and diversity of IR have recently been launched by the Global Pathways Project out of the Free University—Berlin. However, one final caveat regarding this supposed diversity in IR should be noted.

This plurality of theories and methods identified and discussed here may not signify a diverse field. Diversity denotes some degree of variation within an interacting community or system. Meaningful interactions between distinct research sects in IR appear to be very rare. These divides are often reified by remaining resolutely deaf, as Bull suggested, to the voices of those who differ in outlook or in approach. Indeed, Smith (2008, p. 726) argued that the so-called debates in the field can hardly be called debates since “the differing positions have simply ignored one another.” Similarly, Janice Bially Mattern (2008, p. 692) noted that IR has become a “collection of insular research communities; it is an (un)discipline . . . a cacophony of disconnected views of world politics.” In her presidential address to the International Studies Association, Margaret Hermann (1998, p. 606) depicted IR as “the Tower of Babel, filled with a cacophony of different voices—or, as some have implied, a set of tribes that are very territorial, sniping at those who come too close and preferring to be with those like them.” Instead of a diverse discipline, IR might be better characterized by indifference or hostility between various theoretical and methodological sects.

While many have noted this sectarianism and the paradigm wars that too often accompany it, few have offered compelling explanations for this phenomenon in IR. Walker (2010, p. 434) argued that this Balkanization of the discipline has been facilitated by a misapplication of Kuhnian normal science which “encourages hyper-specialized tribalism within subfields.” After all, Kuhn (1970b, p. 254) envisioned a scientific community as “an esoteric, isolated, and largely self-contained discipline . . . its own exclusive audience and judge.” Kuhn (1970a, pp. 150, 205) also acknowledged how the “the proponents of competing paradigms practice their trades in different worlds,” resembling “members of different language-culture communities.” This contributes to an ethos of incommensurability between different research communities in IR. Kuhn, however, influenced all the social sciences, but IR seems particularly divided and, at times, hostile. But the problems of Balkanization, paradigm wars, incommensurability seem to be driven by unique forces within IR as a discipline.

Peter Kristensen (2012, p. 32) pointed out how “It may be an occupational peculiarity” for IR scholars to become “skillful at identifying ever-widening internal divisions and acrimonious lines of opposition that inhibit dialogue and peaceful resolution of scholarly conflicts.” The “occupational peculiarity” may be rooted to the foundational concepts we study and how we build identities within research communities. Waever (1996, p. 172) rightly noted how “paradigms are really political groupings.” These political groupings, or tribes, tend to ape the political environment they study, albeit with a particular realist bent to it all. The system is anarchic and potentially threatening. Sovereign research communities compete for limited resources which come in the form of journal publications, career promotion, ISA panel slots, and general recognition. Like Kuhn’s paradigm communities, these research communities often have their own language, interests, and governing structures, and they have become their own audience and judge. They also cast a critical and suspicious, if not threatened, eye on all rival communities. Their greatest fear, drawn from balance of power logic, is the rise of a hegemonic power or a universal monarchy that takes the form of one dominant theory. If one research community prevailed, according to this realist logic, it would be to the detriment of all others. A hegemonic theory in IR could do to its rivals what Athens did to Melos. To maintain their independence, research communities must remain defiant against any rivals. Finally, diversionary theory of war might also fit here. One way to rally the forces and forge a greater degree of group cohesion is to initiate a conflict, real or not, with an outside rival. By doing so, group members will rally around their flag and more in-group cohesion can be secured. In short, it is in each community’s interest to engage in turf battles and paradigm wars to maintain a cohesive identity. IR research sects may be merely projecting what they study onto the broader IR research community.

The lexicon of international conflict often manifests itself when IR scholars discuss questions of theoretical dominance and the lack of diversity among the so-called “isms.” Above, we cited Smith’s claims of “intellectual imperialism” of realism and Sterling-Folker’s liberalism’s “subjugating, repressive discourse,” and Banks’ view of the “intellectual totalitarianism” of realism. Discussions of paradigmatic divisions in IR will often rely on a language of sovereignty, conflict, and war. For instance, Waever (1996, pp. 169–170) referred to the “post-structuralist guerrilla war against the system.” He then goes on to discuss the possibility of a “rapprochement between reflectivists and rationalists,” which is due in part to the “deradicalisation of reflectivism.” Much of this narrative is driven by fear of dominance or hegemony, fear of marginalization, and the need to negotiate or fight over theoretical boundaries. All these fears are unjustified, given the multitude of theories gaining access to leading journals in IR. This theoretical pluralism provides us with the best opportunity to increase understandings of our increasingly complex world. Delusional fears of some rising hegemonic theory or approach will only sidetrack us from pursuing those understandings.

Moving from our currently divided discipline to one that is more diverse and integrated may be the next great challenge facing IR. I close with a couple of modest suggestions to help address this challenge. First, theories should be a source of puzzles for scholars to investigate, not the source of scholarly identity or tribal affiliation. Puzzles are more easily discussed, challenged, and discarded than are identities. Second, Kuhn’s concept of incommensurability, so often deployed to harden paradigmatic boundaries, must be questioned, if not dismissed. In philosophy of science, Popper has been a vehement critic of this doctrine. Popper (1970, p. 55) argued that much of the history of science can be characterized by a “constant and fruitful discussion between the competing and dominant theories.” Instead of remaining “resolutely deaf” to opposing approaches, Bull’s (1966, p. 377) exhortation during the second debate, IR scholars might open their ears to opposing voices We might return to the measured appreciation for multiple theories that E. H. Carr displayed during the first debate. In the midst of his near complete dismantling of utopian thought, Carr (1946, p. 93) made a plea for the importance of both theories: “any sound political thought must be based on elements of both utopia and reality.” While he envisioned the two operating at different planes, he never sought to dismiss utopian thought. Carr recognized the importance of different theories and approaches for sound political thought. With the myriad of different theories that characterize IR journal publications over the past 45 years, sincere engagement across theoretical and methodological divides is not only possible but such engagement will better prepare us to understand the immense and ever-changing complexities that characterize global politics.

Further Reading

Acharya, A. (2016). Advancing global IR: Challenges, contentions, and contributions. International Studies Review, 18, 4–15.Find this resource:

    Lake, D. (2011). Why “isms” are evil: Theory, epistemology, and academic sects as impediments to understanding progress. International Studies Quarterly, 55, 465–480.Find this resource:

      Maliniak, D., Oakes, A., Peterson, S., & Tierney, M. (2011). International relations in the US academy. International Studies Quarterly, 55, 437–464.Find this resource:

        Reus-Smit, C., & Snidal, D. (Eds.). (2008). The Oxford handbook of international relations. Oxford: Oxford University Press.Find this resource:

          Walker, T. (2010). The Perils of paradigm mentalities: Revisiting Kuhn, Lakatos, and Popper. Perspectives on Politics, 8, 433–451.Find this resource:


            Acharya, A. (2016). Advancing global IR: Challenges, contentions, and contributions. International Studies Review, 18, 4–15.Find this resource:

              Ashley, R. (1986). The poverty of neorealism. In R. Keohane (Eds.), Neorealism and its critics (pp. 255–300). New York: Columbia University Press.Find this resource:

                Baldwin, D. (1993). Neorealism and neoliberalism: The contemporary debate. New York: Columbia University Press.Find this resource:

                  Banks, M. (1985). Where are we now? Review of International Studies, 11, 215–233.Find this resource:

                    Banks, M. (1990). The international relations discipline: Asset or liability for conflict resolution? In J. Burton & F. Dukes (Eds.), Conflict: Readings in management and resolution (pp. 51–70). London: Macmillan.Find this resource:

                      Barkin, S. (2003). Realist constructivism. International Studies Review, 5, 325–342.Find this resource:

                        Brown, C. (2013). The poverty of grand theory. European Journal of International Relations, 19(3), 483–497.Find this resource:

                          Bull, H. (1966). International theory: The case for a classical approach. World Politics, 18, 361–377.Find this resource:

                            Carr, E. (1946/1964). The Twenty Years’ Crisis, 1919–1939. New York: Harper & Row.Find this resource:

                              Ferguson, Y. (2015). Diversity in IR theory: Pluralism as an opportunity for understanding global politics. International Studies Perspectives, 16, 3–12.Find this resource:

                                Finnemore, M., & Sikkink, K. (2001). Taking stock: The constructivist research program in international relations and comparative politics. Annual Review of Political Science, 4, 391–416.Find this resource:

                                  Fuller, S. (2004). Kuhn vs. Popper: The struggle for the soul of science. New York: Columbia University Press.Find this resource:

                                    Garand, J., & Giles, M. (2003). Journals in the discipline: A report on a new survey of American political scientists. PS: Political Science and Politics, 26(April), 293–308.Find this resource:

                                      Gibbs, B., & Singer, J. (1993). Empirical knowledge on world politics: A summary of quantitative research, 1970–1991. Westport, CT: Greenwood.Find this resource:

                                        Hermann, M. (1998). One field, many perspectives: Building the foundations for dialogue. International Studies Quarterly, 42, 605–624.Find this resource:

                                          Hoffmann, S. (1965). The state of war. New York: Praeger.Find this resource:

                                            Hoffmann, S. (1977). An American social science: International relations. Daedalus, 106, 41–60.Find this resource:

                                              Jones, S., & Singer, J. (1972). Beyond conjecture in international politics: Abstracts of data-based research. Itasca, IL: F. E. Peacock Publishers.Find this resource:

                                                Katzenstein, P., & Sil, R. (2008). Eclectic theorizing in the study and practice of international relations. In C. Reus-Smit & D. Snidal (Eds.), The Oxford handbook of international relation (pp. 109–130). Oxford: Oxford University Press.Find this resource:

                                                  Kegley, C. (1995). Controversies in international relations theory: Realism and the neoliberal challenge. New York: St. Martin’s Press.Find this resource:

                                                    Kristensen, P. (2012). Dividing discipline: Structures of communication in international relations. International Studies Review, 14, 32–50.Find this resource:

                                                      Kuhn, T. (1970a). The structure of scientific revolutions (2d ed., revised). Chicago: University of Chicago Press.Find this resource:

                                                        Kuhn, T. (1970b). Reflections on my critics. In I. Lakatos & A. Musgrave (Eds.), Criticism and the growth of knowledge (pp. 231–277). London: Cambridge University Press.Find this resource:

                                                          Lakatos, I. (1970). Falsification and the methodology of scientific research programs. In I. Lakatos & A. Musgrave (Eds.), Criticism and the growth of knowledge (pp. 91–196). London: Cambridge University Press.Find this resource:

                                                            Lake, D. (2011). Why “isms” are evil: Theory, epistemology, and academic sects as impediments to understanding progress. International Studies Quarterly, 55, 465–480.Find this resource:

                                                              Lapid, Y. (1989). The third debate: On the prospects of international theory in a post-positivist era. International Studies Quarterly, 33, 235–254.Find this resource:

                                                                Maliniak, D., Oakes, A., Peterson, S., & Tierney, M. (2011). International relations in the US academy. International Studies Quarterly, 55, 437–464.Find this resource:

                                                                  Mattern, J. (2008). The concept of power and the (un)discipline of international relations. In C. Reus-Smit & D. Snidal (Eds.), The Oxford handbook of international relations (pp. 691–698). Oxford: Oxford University Press.Find this resource:

                                                                    Mearsheimer, J. (2001). The tragedy of the great powers. New York: W. W. Norton.Find this resource:

                                                                      Mingst, K., & Arreguin-Toft, I. (2017). Essentials of international relations (7th ed.). New York: W. W. Norton.Find this resource:

                                                                        Morgenthau, H. (1948). Politics among nations: The pursuit of power and peace. Chicago: University of Chicago Press.Find this resource:

                                                                          Nau, H. (2017). Perspectives on international relations. Los Angeles: SAGE.Find this resource:

                                                                            Peterson, S., & Tierney, M. (2013). Codebook and users guide for TRIP article database. Revised in April (Unpublished). Retrieved from this resource:

                                                                              Popper, K. (1970). Normal science and its dangers. In I. Lakatos & A. Musgrave (Eds.), Criticism and the growth of knowledge (pp. 51–58). London: Cambridge University Press.Find this resource:

                                                                                Popper, K. (1994). The myth of the framework: In defence of science and rationality. Edited by M. A. Notturno. London: Routledge.Find this resource:

                                                                                  Rapoport, A. (1958). Various meanings of “theory.” American Political Science Review, 52, 972–988.Find this resource:

                                                                                    Reus-Smit, C., & Snidal, D. (Eds.). (2008). The Oxford handbook of international relations. Oxford: Oxford University Press.Find this resource:

                                                                                      Rosenthal, J. (1995). Rethinking the moral dimensions of foreign policy. In C. Kegley (Ed.), Controversies in international relations theory: Realism and the neoliberal challenge (pp. 317–330). New York: St. Martin’s.Find this resource:

                                                                                        Russett, B., & Oneal, J. (2001). Triangulating peace: Democracy, interdependence, and international organization. New York: W. W. Norton.Find this resource:

                                                                                          Scheuerman, W. (2009). Hans Morgenthau: Realism and beyond. Cambridge, U.K.: Polity.Find this resource:

                                                                                            Singer, J. D. (1969). The incompleat theorist: Insight without evidence. In J. Rosenau & K. Knorr (Eds.), Contending approaches to international politics (pp. 62–86). Princeton, NJ: Princeton University Press.Find this resource:

                                                                                              Smith, S. (2000). International relations: Still and American social science. British Journal of Politics and International Relations, 2, 374–402.Find this resource:

                                                                                                Smith, S. (2008). Six wishes for a more relevant discipline of international relations. In C. Reus-Smit & D. Snidal (Eds.), The Oxford handbook of international relations (pp. 725–732). Oxford: Oxford University Press.Find this resource:

                                                                                                  Sterling-Folker, J. (2015). All hail to the chief: Liberal IR theory in the New World Order. International Studies Perspectives, 16, 40–49.Find this resource:

                                                                                                    Vasquez, J. (1983). The power of power politics: A critique. New Brunswick, NJ: Rutgers University Press.Find this resource:

                                                                                                      Vasquez, J. (1998). The power of power politics: From classical realism to neotraditionalism (2d ed.). Cambridge, U.K.: Cambridge University Press.Find this resource:

                                                                                                        Wemheuer-Vogelaar, W., Bell, N., Moreles, M., & Tierney, J. (2016). The IR of the Beholder: Examining Global IR Using the 2014 TRIP Survey. International Studies Review, 18, 16–32.Find this resource:

                                                                                                          Waever, O. (1996). The rise and fall of the inter-paradigm debate. In S. Smith, K. Booth, & M. Zalewski (Eds.), International theory: Postivism and beyond (pp. 149–185). Cambridge, U.K.: Cambridge University Press.Find this resource:

                                                                                                            Waever, O. (1998). The sociology of a not so international discipline: American and European developments in international relations. International Organization, 52, 687–727.Find this resource:

                                                                                                              Walker, T. (2008). Two faces of liberalism: Kant, Paine, and the question of intervention. International Studies Quarterly, 52, 449–468.Find this resource:

                                                                                                                Walker, T. (2010). The perils of paradigm mentalities: Revisiting Kuhn, Lakatos, and Popper. Perspectives on Politics, 8, 433–451.Find this resource:

                                                                                                                  Walker, T., & Morton, J. (2005). Re-assessing the “power of power politics” thesis: Is realism still dominant? International Studies Review, 7, 341–356.Find this resource:

                                                                                                                    Walker, T., & Morton, J. (2016). TRIP ped up? Re-evaluating the TRIP project claims of theoretical diversity in IR. Paper presented at the Annual Meetings of the International Studies Association, Atlanta, GA, March 19.Find this resource:

                                                                                                                      Walt, S. (1998). One world, many theories. Foreign Policy, 110, 29–46.Find this resource:

                                                                                                                        Waltz, K. (1979). Theory of international politics. Reading, MA: Addison-Wesley.Find this resource:

                                                                                                                          Waltz, K. (1998). Interview with Ken Waltz: Conducted by Fred Halliday and Justin Rosenberg. Review of International Studies, 24, 371–386.Find this resource:

                                                                                                                            Wohlforth, W. (2008). Realism. In C. Reus-Smit & D. Snidal (Eds.), The Oxford handbook of international relations (pp. 131–149). Oxford: Oxford University Press.Find this resource: