Teoria das Relações Internacionais (Resumão)


Classical Realism

Classical realism is a philosophical tradition that sees international politics as a perpetual struggle for power and resources in a world of scarcity. The state or political community, not the individual or economic class, is the primary unit of analysis in classical realism. Classical realists wrote over the course of some three millennia and for vastly different purposes. Moreover, it is incorrect to say that all classical realists identified human nature as the root cause of conflict in history.

Some, such as Niccolò Machiavelli, Hans J. Morgenthau, and Reinhold Niebuhr, saw human nature, specifically human being’s inherent lust for power or sin, as the root cause of warfare (the so-called “evil” tradition).

Others, such as Thomas Hobbes, Arnold Wolfers, John Herz, and Raymond Aron, saw anarchy, the absence of a universal sovereign or worldwide government, as the permissive cause war (the so-called “tragic” tradition).

Yet others, such as Thucydides, Winston Churchill, Henry Kissinger, George Kennan, and E. H. Carr, stressed the combination of human nature, anarchy, and the ambitions of individual statesmen as the root causes of warfare.

All classical realists created their theories through induction, not deduction. The notion of a balance-of-power is one the major themes in classical realism. Please note, that modern IR theorists coined the term “classical realism” to distinguish the writings of Thucydides, Machiavelli, Morgenthau, and others, from the structural or neorealism of Kenneth Waltz and his followers.

Classical Liberalism

Classical liberalism is a philosophical tradition that emphasizes the ability of human reason to create a world of peace and harmony. Thus, this school presents a fundamentally optimistic view of human history, in contrast to the pessimistic view presented by classical realism. Classical liberalism was largely an outgrowth of the Age of Enlightenment in late seventeenth and eighteenth century Western Europe (although Hugo Grotius wrote in the sixteenth century). In general, adherents of classical liberalism (a.k.a., idealism) hold that the international system tends strongly toward peace and cooperation among states. Classical liberals identified different mechanisms for this trend:

  1. economic interdependence among states resulting from free trade (i.e., economic liberalism);
  2. transnational ties among individuals and privately organized interest groups within society (i.e., transnational liberalism);
  3. the emergence of a “pacific union” of states with republican or liberal democratic political systems (i.e., Kantian liberalism);
  4. the emergence of a society of states bound by common rules, customs, and norms (i.e. Groatian tradition);
  5. the creation of formal international organizations and collective security mechanisms (i.e., Wilsonian internationalism).

To classical liberals, warfare is not the result of the anarchic nature of the international system, but rather the result of human folly or the defective political systems of individual states. The carnage of World War I (1914-18) and the Twenty Years’ Crisis (1919-39) largely discredited the several variants of classical liberalism. Nonetheless, neoliberal institutionalism and the modern literature on the democratic peace are the intellectual descendants of classical liberalism.


Marxism is a school of thought inspired by the writings of Karl Marx, and refined by V. I. Lenin and others. Marxism identifies the causes of war as class conflict especially conflict between and within the capitalist class. Class, not the state or the individual, is the major unit of analysis in Marxist theory. Marxism presents a dialectical conception of human history: contradictions inherent in each historical epoch eventually lead to the rise of a new dominant class. The bourgeoisie or capitalist class dominates the era of capitalism, according to Marx. This era of capitalism will inevitably produce a proletarian, or working class, revolution. An era of socialism will follow, in which workers own the means of production. Eventually, there will be a classless, communist society in which the state, historically a tool of the bourgeoisie, will wither away. A number of contemporary theorists have drawn on Marxist insights and categories of analysis, particularly in the study of on imperialism, dependency, and the world capitalist system.


Balance-of-power theory

The balance-of-power is a major concept in classical realism and in contemporary realism. In general, balance-of-power theory holds that an extreme concentration of material power in the hands of single state or attempts by a state to conquer a region will provoke countervailing actions. These countervailing actions, called balancing, can take the form of alliance formation (external balancing) or efforts by individual states to increase their own relative power, generally through arms racing and military innovation (internal balancing). While balancing does not always operate efficiency to prevent the outbreak of war, it does help to maintain the stability of relations among states in the long-term. Two variants of balance-of-power theory are important in Political Science:

  • Classical Realist Balance-of-power theory: Classical realists, such as Morgenthau, Gulick, Kissinger, and Carr, saw the balance-of-power as a system consciously created by the great powers of the day. The balance-of-power functions most effectively when alliances are fluid, when they are easily formed or broken based on expediency, regardless of values, religion, history, or form of government. Occasionally a single state plays a balancer role, shifting its support to oppose whatever state or alliance is strongest. From the wars of Louis XIV (1688-1714) until World War II (1939-45), Great Britain played the role of balancer in Western Europe. The United States has played a similar role in Western Europe since World War I (1914-18). Classical realist balance-of-power theory holds that major war is less likely in a multipolar international system with fluid alliances among the great powers. Conversely, major war is more likely in bipolar international systems or in multipolar systems with rigid great power alliances. Note, that classical balance-of-power theory is an inductive theory. Morgenthau, Gulick, and others developed the theory by drawing upon their reading of modern European diplomatic history. Major criticisms of the theory centered on its relevance to the non-European world and the difficulties of measuring power.
  • Neorealist Balance-of-power theory: Kenneth Waltz sought to recast balance-of-power theory as a deductive framework by drawing upon microeconomic theory. Unlike the classical realists, Waltz sees the balance-of-power as a naturally recurring equilibrium, not a system consciously created by the great powers. Neorealist balance-of-power theory focuses on two enduring structural features of the international system—anarchy and polarity. In contrast to the classical realist variant, neorealist balance-of-power theory holds that bipolar systems are less likely to experience major wars than multipolar systems. Under multipolarity, great powers balance by forming alliances. However, this raises the risk of major war through miscalculation of other’s resolve; fear of abandonment by allies; incentives to neglect military spending; and incentives to pass the cost of mutual defense on to other states (buck-passing). By contrast, bipolarity is more stable because each great power recognizes that the other is the only serious threat to its survival. Since the addition or defection of weaker allies has little impact on the systemic balance-of-power, the great powers can rely on internal balancing. At the same time, each great power knows that because there are only two of them, each must block the other throughout the world. Major criticisms of neorealist balance-of-power theory include a static conception of power, an inability to explain international change, an inattention to the role of international institutions and non-state actors, and the contradictory explanation for bipolar stability.

Balance-of-threat theory

Balance-of-power theory is a refinement of neorealist balance-of-power theory developed by Stephen M. Walt in the mid-1980s. Walt, a former student of Waltz, contends that states balance against threat, not aggregate levels of material power. Threat is a composite of

  1. a state’s aggregate power;
  2. its geographic proximity;
  3. its offensive military capabilities;
  4. the perceived aggressive intentions of its leaders

Balance-of-threat theory holds that states facing an external threat will generally balance against the state or coalition posing the threat. In general, states prefer not to bandwagon that is to form alliances with the threatening state or coalition, since doing so often places their long-term security in jeopardy. Weak and isolated states, however, may have no alternative but to bandwagon with stronger aggressors to avoid absorption. NOTE: Balance-of-threat theory is a variant of defensive realism because it assumes that the international system does not generally provide incentives for aggression and expansion.

Complex Interdependence Theory

Robert Keohane and Joseph S. Nye, Jr. coined the term ‘complex interdependence’ in reference to various, complex transnational connections (interdependencies) between states and societies. Interdependence theorists .note that such relations, particularly economic ones, have increased since World War II. Conversely, the incidences of military force and power balancing among advanced industrialized states have decreased during the same period. Writing in the late 1970s (in the aftermath of the United States’ withdrawal from the Vietnam War and the 1973 OPEC oil embargo), Keohane and Nye argued that the decline of military force as a policy tool and the increase in economic and other forms of interdependence should increase the probability of cooperation among states. One can see the complex interdependence framework as an attempt to synthesize elements of realist and liberal thought. Finally, anticipating problems of cheating and relative gains raised by realists, interdependence theorists introduced the concept of ‘regimes’ to mitigate anarchy and facilitate cooperation. Here one can see that complex interdependence theory was the precursor to neoliberal institutionalism.

Constructivism (a.k.a. social constructivism)

Constructivism is a broad school of thought that emphasizes the impact of ideas, identities, norms, and culture in world politics. Constructivists downplay material variables, such as the relative distribution of power or levels of trade between states, and instead focus on shared understandings and norms. For example, instead of taking the “state” for granted and assuming that it simply seeks to survive, as realists and liberals do, constructivists regard the interests and identities of states as the highly malleable product of specific historical processes. Constructivists focus on the capacity and will of people to take a deliberate attitude towards the world and to lend it significance. This capacity leads to certain social facts that depend on human agreement that those facts do exist and which typically require human institutions to sustain their existence. John Gerard Ruggie writes, “Social facts include money, property rights, sovereignty, marriage, football, and Valentine’s Day, in contrast to such brute observational facts as rivers, mountains, population size, bombs, bullets, and gravity, which exist whether or not that there is agreement that they do.” Constructivism is especially attentive to sources of international change. In the 1990s, constructivism largely replaced Marxism as the major radical perspective in IR. Stephen Walt, a leading [defensive] realist observes: “The end of the Cold War played an important role in legitimating constructivist theories because realism and liberalism both failed to anticipate this event and had some trouble explaining it. Constructivists had an explanation: Specifically, former [Soviet] president Mikhail Gorbachev revolutionized Soviet foreign policy because he embraced new ideas such as “common security.” There is no single constructivist theory of international relations and constructivists disagree among themselves about ontology and methodology. Prominent constructivist IR scholars include Ted Hopf, Nicholas Onuf, Thomas Risse, and Alexander Wendt. I would also place various cultural theories of foreign policy in the constructivist camp.

Contemporary Realism (a.k.a., structural realism)

This is an umbrella term that I use for the post-1980 realist research program in its entirety. The year 1979 saw the publication of Kenneth Waltz’s Theory of International Politics, which many IR scholars (both self-described realists and non-realists) saw as a clean break with the classical realism of Hans Morgenthau, E.H. Carr, Arnold Wolfers, and Henry Kissinger. In general, contemporary realism emphasizes the influence of anarchy and uncertainty in the international system rather than the assumption of innate conflict or other innate characteristics of human nature. All variants of contemporary realism begin with the assumption that the international system—that is anarchy and the relative distribution of material power among the states that comprise the system—shape the broad parameters of international outcomes and the likely foreign policies of individual states. There are several different sub-schools or sub-research programs within the contemporary realist research program:

  • Defensive realism
  • Offensive realism
  • Neoclassical realism
  • Hegemonic realism (e.g., hegemonic, power transition and long cycle theories, etc.)

Defensive Realism

Defensive realism is an umbrella term for several theories of international politics and foreign policy that build upon Robert Jervis’s writings on the security dilemma and to a lesser extent upon Kenneth Waltz’s balance-of-power theory (neorealism). Defensive realism holds that the international system provides incentives for expansion only under certain conditions. The security dilemma causes states to worry about one another’s future intentions and relative power. Pairs of states may pursue purely security seeking strategies, but inadvertently generate spirals of mutual hostility or conflict. States often, although not always, pursue expansionist policies because their leaders mistakenly believe that aggression is the only way to make their state secure. Defensive realism predicts great variation in internationally driven expansion and suggests that states ought to generally pursue moderate strategies as the best route to security. Under most circumstances, the stronger states in the international system should pursue military, diplomatic, and foreign economic policies that communicate restraint. Examples of defensive realism include: offense-defense theory, balance-of-power theory, balance-of-threat theory, and domestic mobilization theories.

Democratic Peace Thesis (a.k.a., liberal peace)

The democratic peace thesis is the empirical observation that, since 1815, pairs of democratic states have rarely gone to war with each other. This is not to say that democratic states are less war prone. Rather, the claim is that pairings of democracies enjoy inherently more peaceful relations than other regime pairings (i.e., democracy versus non-democracy and non-democracy versus non-democracy). The democratic peace literature finds its inspiration in Immanuel Kant’s 1795 essay, “Toward Perpetual Peace.” Strictly speaking, the claim that democracies do not fight democracies is a proposition or hypothesis, not a theory. There is no single theory of the democratic peace. Rather, there are several different theories that claim a causal relationship between a state’s domestic political system and ideology and its likelihood to go war with states with identical or similar domestic systems. Since the 1960s, the democratic peace has emerged as major body of theory within neoliberalism. Criticisms of the democratic peace literature include: the subjective and elastic definitions of democracy, a tendency to test democratic peace hypotheses against weak realist alternatives, incomplete data sets, omitted variable bias, and over-determination in case studies.

Hegemonic Theory (a.k.a., power preponderance or hegemonic stability theory)

Hegemonic theory is a variant of structural realism that holds that the international system is most stable when one state enjoys a preponderance of power. Concentrations of power decrease the likelihood of major war, whereas a more even distribution of power among the first and second ranked states increases the likelihood of major war. At any given time, the distribution of territory, material resources, and privileges within the international system reflects the interests of the most powerful state, generally the victor in the last major war. The core hypothesis of hegemonic theory is that the probability of major war is highest when the power of the rising challenger roughly matches that of the dominant state. According to the theory, the rising challenger, not the declining hegemon, is more likely to initiate a major war to receive the status and rewards denied by the existing international system. Hegemonic theory is closely related to (although not identical to) power transitional theory. Two points are worth noting. First, hegemonic theory is not necessarily inconsistent with neorealist balance-of-power theory, since the two theories purport to explain slightly different phenomena and focus on different structural attributes of the international system. Second, the term “hegemonic stability theory” originated in the international political economy (IPE) literature and entails a very different conception of hegemony. In the security studies literature, however, hegemonic theory is generally associated with Robert Gilpin, although William C. Wohlforth, Stephen Brooks, Randall Schweller, and others have made important contributions.


Thomas Risse writes, “Institutionalism as a theoretical approach can be differentiated from other approaches in international relations in terms of the substantive claim that institutions matter, that is, that they exert clearly identifiable and independent effects on political life.” Institutionalism is not a theory per se. Rather it is a broad category that encompasses many different theories, not all of which share the same assumptions or even the same ontology. [See neoliberal institutionalism]

Neoclassical Realism

Neoclassical realism refers to a diverse set of contemporary realist theories that seek to explain the specific foreign policy decisions of major states, not broad patterns of international behavior or systemic outcomes. Neoclassical realist theories are theories of foreign policy. Some critics of neorealism contend that Waltz’s quest for parsimony sacrificed much of the practical wisdom and policy relevance found in the classical realist writings of Morgenthau, Carr, Wolfers, and others. As a response, a number of younger scholars have sought a synthesis of classical realist thought with neorealist rigor. In an influential 1998 review essay in World Politics, Gideon Rose, the managing editor of Foreign Affairs, coined the term “neoclassical realism” to describe the work of these scholars. Please note: neoclassical realism is more of a methodological approach than a distinct variant of realist theory. Indeed, two of the authors that Rose cites as being neoclassical realists, Fareed Zakaria and Thomas Christensen, explicitly situate their work in the offensive realism/defensive realism debate. Another neoclassical realist, William Wohlforth, sees his work as extension of hegemonic theory. Neoclassical realists are interested in theorizing, as well as in policy and diplomatic history. They eschew a mono-causal focus on domestic or systemic variables, in favor of richer historical narratives.

Neoliberalism (a.k.a., Contemporary Liberalism)

Neoliberalism is a branch of liberalism that emphasizes the influence of democracy, free trade, and international institutions in promoting international cooperation and economic prosperity, rather than ability of human reason. Neoliberalism, which emerged in the aftermath of World War II, rejects the classical liberal (or idealist) notion that there is an automatic harmony of interests among individuals or states. One can think of neoliberalism as a research program that encompasses several different strands of theories:

  • The democratic peace (or liberal peace) thesis
  • Neoliberal institutionalism (see below)
  • Complex interdependence theory (see above)
  • Economic liberalism (globalization theory)

Neoliberal Institutionalism (a.k.a., Liberal Institutionalism or Regime Theory)

Neoliberal institutionalism is a branch of contemporary liberalism that focuses on the role of international institutions in facilitating mutually beneficial cooperation among states. International institutions are “persistent and connected sets of rules (formal or informal) that prescribe behavioral roles, constrain activity, and shape expectations.” Institutions can range from formal international organizations, such as the United Nations, the International Monetary Fund, and NATO, to more informal agreements such as the Law of the Seas Convention and the Kyoto Protocol. Neoliberal institutionalists believe that realists overstate the potential for international conflict and suggest that there are countervailing forces, such as repeated interactions, that propel states toward cooperation. They regard anarchy as the absence of a mechanism above the levels of states to enforce agreements and they regard cheating as the greatest threat to cooperation. One weakness of neoliberal institutionalism is the absence of a baseline of expectations against which to judge its claims. Institutionalist hypotheses are difficult to test because the theory says little about how much international cooperation to expect in the absence of institutions. Another major criticism is the tendency of the theory’s proponents to study over-determined cases of international cooperation. Neoliberal institutionalism is mainly associated with the writings of Robert O. Keohane and his disciples.

Neoliberal-Neorealist Debate

This was a major debate between proponents of neoliberal institutionalism and neorealism (specifically Waltz’s balance-of-power theory) that dominated the IR sub field of political science from the mid-1980s to the mid-1990s. The debate centered largely on whether anarchy compels states to be more concerned with securing absolute gains or relative gains. In other words, do states seek to be rich and powerful or do they seek to be richer and more powerful than everybody else? This question had broad implications for the likelihood of cooperation and conflict among states across a range of issue areas in security and international political economy. However, it is easy to exaggerate the level of disagreement between the two schools. Neorealists never claimed that mutually beneficial international cooperation was impossible, that international politics is a purely zero-sum game, or that states never relied on institutions. For their part, neoliberal institutionalists never claimed that international cooperation was ubiquitous or easy to achieve. Rather, as Robert Jervis, a leading defensive realist, notes, “Neoliberalism does not see more cooperation than does realism; rather, neoliberalism believes that there is more unrealized or potential cooperation than does realism, the schools of thought disagree about how much conflict in world politics is unnecessary or avoidable in the sense that actors failing to agree even though their preferences overlap.

Neorealism (a.k.a., Structural realism)

Neorealism is a generic term used alternately in reference to:

  • The specific balance-of-power theory developed by Kenneth Waltz in Theory of International Politics (New York: Addison Wesley, 1979), see above;
  • A broad family of realist theories that emphasizes the anarchic nature of the international system and the relative distribution of power among states as the permissive causes of war, rather than an assumption of innate conflict or human nature (e.g., Professor Eichenberg’s definition from his version of PS 51; also see contemporary realism above);
  • A branch of realism that seeks to explain international political outcomes (e.g. phenomena resulting from the interaction of two or more states) but not the foreign policy behavior of individual states.

Richard Ashley, a critic of realism, coined the term “neo-realism” in 1983, specifically in reference to Waltz’s Theory of International Politics.

Offense-Defense Theory

Offense-defense theory is a term for several theories that link the severity of the security dilemma, and therefore the likelihood of war, to the types of military technology available to actors and the ease of conquest. In his classic article, “Cooperation under the Security Dilemma,” Robert Jervis argued that the security dilemma is most severe and the international system is less stable when offensive weapons systems enjoy an advantage over defensive weapons systems. By contrast, when the defense is more potent, status quo actors find it easier to adopt compatible security policies, and the pernicious effects of the security dilemma are greatly diminished. The relative advantage of offensive or defensive weapons systems is called the “offense-defense balance.” The extent to which actors can differentiate between offensive weapons and defensive weapons is called “offense-defense differentiation.” Although different theorists offer competing definitions and measurements of the offense-defense balance, Jervis referred to the modalities of battlefield conquest: military tactics, strategy, technology, and a state’s geography. Thomas Christensen and Jack Snyder, Sean Lynn-Jones, Stephen Van Evera, Charles Glaser and Chaim Kaufmann, and others have refined and expanded Jervis’s original conception of the offense-defense balance. All versions of offense-defense theory see nuclear weapons (and particularly secure, second-strike nuclear arsenals) as the ultimate defense-dominant weapons system. Offense-defense theory is one variant of defensive realism. Nonetheless, offense-defense theory is controversial even among self-described realists, because of the difficulty in defining and objectively measuring the theory’s explanatory variable—the offense-defense balance. Please note that offense-defense theory and offensive realism are not the same.

Offensive Realism

Offensive realism is an umbrella term for several theories of international politics and foreign policy that give analytical primacy to the hostile and unforgiving nature of the international system as the cause of conflict. Like defensive realism, some variants of offensive realism build upon and depart from Kenneth Waltz’s neorealism. Offensive realism holds that anarchy provides strong incentives for expansion. All states strive to maximize their relative power because only the strongest states can guarantee their survival. They pursue expansionist policies when and where the benefits of doing so outweigh the costs. States face the ever-present threat that other states will use force to harm or conquer them. This compels them to improve their relative power positions through arms build-ups, unilateral diplomacy, mercantile (or even autarkic) foreign economic policies, and opportunistic expansion. Ultimately every state in the international system strives to become a regional hegemon – a state that enjoys a preponderance of military, economic, and potential power in its part of the globe. Offensive realists however, disagree over the historical prevalence of hegemonic regional systems and the likely responses of weaker states to a would-be regional hegemon (e.g., balancing or bandwagoning).

Power Transition Theory

Created by the late A.F.K. Organski and originally published in his textbook, World Politics, power transition theory describes international politics as a hierarchy with:

  • a “dominant” state or system leader, which enjoys the largest proportion of power resources (population, productivity, and political capacity meaning coherence and stability);
  • great powers,” a collection of potential rivals to the dominant state and who share in the tasks of maintaining the system and controlling the allocation of power resources;
  • “middle powers” of regional significance similar to the dominant state, but unable to challenge the dominant state or the system structure,
  • “small powers,” a category that encompasses all other states in the international system.

War is most likely, of longest duration, and greatest magnitude, when a challenger to the dominant power enters into approximate parity with the dominant state and is dissatisfied with the existing system. Similarly, alliances are most stable when the parties to the alliance are satisfied with the system structure. There are further nuances to the theory: for instance, the sources of power transition vary in their volatility, population change being the least volatile and political capacity (defined as the ability of the government to control resources internal to the country) the most volatile.


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