evaluating theories - kenneth waltz

8/2/2019 Evaluating Theories - Kenneth Waltz

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American Political Science Review Vol. 91, No.4 December 1997

E v a lu a t i n g T h e o r i e sKENNETH N. WALTZ University of California, Berkeleyjohn Vasquez claims tofollow Imre Lakatos but distortshis criteriafor judging theoriesand evaluatingresearch programs. Vasquez claims that facts observed can falsify a theory by showing that itspredictions are wrong.He fails to consider thepuzzles posed by the interdependence of theoryand fact.He places all realists in a singleparadigm despite the divergent assumptions of traditional and structuralrealists. In contrast to Vasquez, I argue that explanation, not prediction, is the ultimate criterion of goodtheory, that a theory can be validated only by working back and forth between its implications and anuncertain state of affairs that we take to be the reality against which theory is tested, and that the results oftests are alwaysproblematic.Hvingpreviously covered the criticisms JohnVasquez makes (see especially Waltz 1979,1986), I respond to his article reluctantly. Oneis, however, always tempted to try again.Following Lakatos (1970), albeit shakily, in movingfrom paradigms to theories to research programs,Vasquez says he places theories in a single paradigm ifthey "share certain fundamental assumptions" (p. 900).He thereupon lumps old and new realists together inone realist paradigm. This is odd since, as he recog-nizes, old and new realists work from different basicassumptions. Believing that states strive for ever morepower, Hans Morgenthau took power to be an end initself. In contrast, I built structural theory on theassumption that survival is the goal of states and thatpower is one of the means to that end. Politicalscientists generally work from two different paradigms:one behavioral, the other systemic. Old realists seecauses as running directly from states to the outcomestheir actions produce. New realists see states forming astructure by their interactions and then being stronglyaffected by the structure their interactions haveformed. Old realists account for political outcomesmainly by analyzing differences among states; newrealists show why states tend to become like units asthey try to coexist in a self-help system, with behaviorsand outcomes explained by differences in the positionsof states as well as by their internal characteristics (seeWaltz 1990). If the term "paradigm" means anything atall, it cannot accommodate such fundamental differ-ences.Vasquez puts old and new realists in the same potbecause he misunderstands realists. He makes oddstatements about what paradigms do because he mis-understands paradigms. He believes that paradigmseasily generate a family of theories (p. 900). Paradigmsare apparently like sausage machines: Tum the crank,and theories come out. Yet no one in any field is ableto generate theories easily or even to say how to goabout creating them.Vasquez finds lots of realist theories because hedefines theories loosely as "inter-related propositionspurporting to explain behavior" (footnote 3). If inter-Kenneth N. Waltz is Ford Professor of Political Science, Emeritus,University of California, Berkeley, CA 94720-1950.The author is grateful to Karen Ruth Adams for her assistance.

relating propositions were all it took to make theories,then, of course, we would have many of them. I can,however, think of any number of propositions purport-ing to explain something that would not qualify astheories by any useful definition of the term. I definetheory as a picture, mentally formed, of a boundedrealm or domain of activity. A theory depicts theorganization of a realm and the connections among itsparts. The infinite materials of any realm can beorganized in endlessly different ways. Reality is com-plex; theory is simple. By simplification, theories laybare the essential elements in play and indicate neces-sary relations of cause and interdependency-or sug-gest where to look for them (see Waltz 1979, 1-13).Vasquez, following his definition, finds many theories;I find few.Vasquez's belief that theories are plentiful and easyto produce reflects the positivist tradition that perme-ates American political science. At the extreme, posi-tivists believe that reality can be apprehended directly,without benefit of theory. Reality is whatever wedirectly observe. In a more moderate version of posi-tivism, theory is but one step removed from reality, isarrived at largely by induction, is rather easy to con-struct, and is fairly easy to test. In their book oninterdependence, Keohane and Nye provide a clearexample when they "argue that complex interdepen-dence sometimes comes closer to reality than doesrealism" (1989, 23). Yet, if we knew what reality is,theory would serve no purpose. Statements such as"parsimony is a judgment ... about the nature of theworld: it is assumed to be simple," neatly express theidea that theory does little more than mirror reality(King, Keohane, and Verba 1994, 20)Faced with an infinite number of "facts" one mustwonder, however, which ones are to be taken aspertinent when trying to explain something. As themolecular biologist Gunther Stent has put it: "Realityis constructed by the mind ... the recognition of struc-tures is nothing else than the selective destruction ofinformation" (1973, EI7). Scientists and philosophersof science refer to facts as being "theory laden" and totheory and fact as being "interdependent." "Everyfact," as Goethe nicely put it, "is already a theory."Theory, rather than being a mirror in which reality isreflected, is an instrument to be used in attempting toexplain a circumscribed part of a reality of whose true

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Evaluating Theories December 1997dimensions we can never be sure. The instrument is ofno use if it does little more than ape the complexity ofthe world. To say that a "theory should be just ascomplicated as all our evidence suggests" (King, Keo-hane, and Verba 1994, 20) amounts to a renunciationof science from Galileo onward.Because of the interdependence of theory and fact,the construction and testing of theories is a moreproblematic task than most political scientists havethought. Understanding this, Lakatos rejected "dog-matic falsification" in favor of judging theories by thefruitfulness of the research programs they may spawn.Following Lakatos, Vasquez faults the realist paradigmfor what he takes to be the regressive quality of itsresearch program. Forsaking Lakatos, he then adducesevidence that in his view falsifies balance-of-powertheory in its structural-realist form. I shall considerboth claims.I disagree with Lakatos on some points, but not onhis rejection of the notion that tests can falsify theories.To explain why falsification won't do, I all too brieflymention two problems. First, proving something falserequires proving something else true. Yet the factsagainst which we test theories are themselves problem-atic. As Lakatos rightly says, in italics, "theories are notonly equally unprovable, ... they are also equally undis-provable" (1970, 103; cf. Harris 1970, 353). Amongnatural scientists, falsification is a little used method(Bochenski 1965, 109; cf. Harris 1970). Social scientistsshould think about why this is so.Second, citing Popper (1959), Vasquez insists that"paradigms" should specify the evidence that woulddisprove them and criticizes realism for not doing so(p. 905). In contrast, Lakatos observes that "the mostadmired scientific theories simply fail to forbid anyobservable state of affairs" (1970, 100, his italics). This istrue for many reasons. Lakatos himself points out thatwe always evaluate theories with a ceteris paribusclause implied, and we can never be sure that it holds.To express the same thought in different words, scien-tific theories deal in idealizations. If the results ofscientific experiments are carried to enough decimalpoints, hypotheses inferred from theories are alwaysproved wrong. As the Nobel Laureate in physics,Steven Weinberg, puts it: "There is no theory that isnot contradicted by some experiment" (1992, 93).Ernst Nagel (1961, 460-6, 505-9) expressed a similarthought when he pointed out that social-science pre-dictions fail because social scientists do not deal inidealizations. It is because falsification is untenablethat Lakatos proposes that we evaluate theories by thefruitfulness of their research programs. Ultimately, heconcludes, as others had earlier, that a theory isoverthrown only by a better theory (p. 119; cf. Conant1947,48).Despite claiming to follow Lakatos's advice to eval-uate theories through their research programs,Vasquez emphasizes what he takes to be evidencefalsifying balance-of-power theory. According to him,the historian Paul Schroeder (1994) has presented"devastating evidence" against it. One must under-stand, however, what a theory claims to explain before

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FIGURE 1

International Structure

t tInteracting Units

attempting to test it. Early in his piece, Schroeder (p.109) draws a picture of neorealism's logic. All of hisarrows run in one direction, from the system down-ward. Realizing that many people have trouble under-standing theory, I drew a few pictures myself. Figure 1depicts one of them (Waltz 1979, 40). Structural theoryemphasizes that causation runs from structures tostates and from states to structure. It also explains,among other things, why balances of power recurrentlyform. Schroeder rejects structural theory because itfails to account for the motives of statesmen. Yet, asWilliam Graham Sumner wrote: "Motives from whichmen act have nothing at all to do with the conse-quences of their action" ([1911] 1968, 212). I would say"little" rather than "nothing," but the point is clear,and structural theory explains why it holds. WhatVasquez takes to be Schroeder's "devastating evi-dence" turns out to be a melange of irrelevant diplo-matic lore. Like Vasquez, Schroeder ignores the basicinjunction that theories be judged bywhat they claim toexplain. Moreover, both fail to notice that Mor-genthau's understanding of balances of power differsfundamentally from mine. For Morgenthau, balancesare intended and must be sought by the statesmen whoproduce them. For me, balances are produced whetheror not intended. Schroeder's "evidence" may apply toMorgenthau's ideas about balances of power; it doesnot apply to mine. This again shows how misleading itis to place all realists in a single paradigm.Vasquez and Schroeder note that power is often outof balance. Is structural theory invalidated because theactions of states sometimes fail to bring their systeminto balance? In answering this question, it is helpful tothink of similar problems in economics. Classical eco-nomic theory holds that, in the absence of governmen-tal intervention, competitive economies tend towardequilibrium at full employment of the factors of pro-duction. Yet one rarely finds an economy in equilib-rium. Further, theory leads one to expect that compe-tition will lead to a similarity of products as well as ofprices. Illustrating the result, Harold Hotelling (1929)pointed out that autos, furniture, cider, churches, andpolitical parties become much like one another. But atendency toward the sameness of products may not beapparent at a given moment, for a competitor maysuccessfully outflank its rivals by offering a design thatbreaks the mold. Do economies in disequilibrium andvariations in product design cast doubt on hypothesesinferred from theories of competition? Hardly. Eco-nomic theory predicts strong and persistent tendencies


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American Political Science Review Vol. 91, No.4rather than particular states or conditions. Similarly, nocontradiction exists between saying that international-political systems tend strongly toward balance but areseldom in balance.Vasquez's attempt to apply Lakatos's ideas aboutresearch programs to balance-of-power theory is asunsuccessful as his attempt to adduce evidence thatwould falsify it. Lakatos defines a series of theories asprogressive "if each new theory has some excess em-pirical content over its predecessor, that is, if it predictssome novel, hitherto unexpected facts" (1970, 116).Newtonian science is a wonderful example of a pro-gressive series of theories, incorporating the same basicassumptions about the universe in theories coveringsuccessively more phenomena. Classical economics,able to explain the working of national and of interna-tional economies as well, is another example. In inter-national politics, where can one find such a use offundamental concepts to develop theories coveringever more phenomena? Vasquez claims to find several,but his claim rests sometimes on placing in a singlerealist program work that belongs in different ones, andsometimes on taking work done when applying atheory as being the creation of a new one.One cannot judge the fertility of a research programby evaluating work done outside of it. Vasquez takesRandall Schweller's (1994) essay on bandwagoning aswork done within the realist paradigm and argues thatit provides an example of its degeneration. Schweller,however, sets out to show that the central theory ofneorealism is wrong. He rejects neorealism's assump-tions about power as a means and survival as the goalof states in favor of Morgenthau's assumption thatstates seek ever more power. He claims to show thatbandwagoning ismore common than balancing, believ-ing that if it is, then neorealist theory fails. Schwellerand I work within different research programs. Thequestion therefore shifts from the quality of the pro-gram to whether his claims about bandwagoning inval-idate structural theory.Structural theory assumes that the dominant goal ofstates is security, since to pursue whatever other goalsthey may have, they first must survive. Bandwagoningand balancing by the logic of the theory are oppositeresponses of security-seeking states to their situations.States concerned for their security value relative gainsover absolute ones. At the extremes, however, withvery secure or very insecure states, the quest forabsolute gains may prevail over the quest for relativeones. Very weak states cannot make themselves secureby their own efforts. Whatever the risks, their mainchance may be to jump on a bandwagon pulled bystronger states. Other states may have a choice be-tween joining a stronger state and balancing against it,and they may make the wrong one. States sometimesblunder when trying to respond sensibly to both inter-nal and external pressures. Morgenthau once com-pared a statesman not believing in the balance ofpower to a scientist not believing in the law of gravity.Laws can be broken, but breaking them risks punish-ment. One who violates the law of gravity by steppingfrom a nineteenth-story window will suffer instant and

condign punishment. A state that bandwagons whenthe situation calls for balancing runs risks, as Mussoli-ni's Italy discovered after it jumped on Hitler's band-wagon, although in international politics punishmentmay not be swift and sure. By joining the stronger side,Italy became Germany's junior partner, and Mussolinilost control of his policy. Bandwagoning by some statesstrengthened Germany and encouraged Hitler to fur-ther conquest. Only balancing in the middle and later1930s could have stopped him. Various states, includ-ing Italy, paid a great price for their failure to balanceearlier. Theory does not direct the policies of states; itdoes describe their expected consequences.States' actions are not determined by structure.Rather, as I have said before, structures shape andshove; they encourage states to do some things and torefrain from doing others. Because states coexist in aself-help system, they are free to do any fool thing theycare to, but they are likely to be rewarded for behaviorthat is responsive to structural pressures and punishedfor behavior that is not.Vasquez requires that theories predict, since predic-tion seems to make falsification possible. He thereforeseizes upon Schweller's claim that bandwagoning ismore common than balancing. Whether this looks likefalsifying evidence depends on what is predicted. Likeclassical economic theory, balance-of-power theorydoes not say that a system will be in equilibrium mostor even much of the time. Instead, it predicts that, willynilly, balances will form over time. That, Vasquezwould no doubt say, is not much of a prediction. YetCharles Kegley (1993, 139) has sensibly remarked thatif a multipolar system emerges from the present unipo-lar one, realism will be vindicated. Seldom in interna-tional politics do signs of vindication appear so quickly.Multipolarity is developing before our eyes: To all butthe myopic, it can already be seen on the horizon.Moreover, it is emerging in accordance with the bal-ancing imperative.

In the light of structural theory, unipolarity appearsas the least stable of international configurations. Un-likely though it is, a dominant power may behave withmoderation, restraint, and forbearance. Even if it does,however, weaker states will worry about its futurebehavior. America's founding fathers warned againstthe perils of power in the absence of checks andbalances. Is unbalanced power less of a danger ininternational than in national politics? Some countrieswill not want to bet that it is. As nature abhors avacuum, so international politics abhors unbalancedpower. Faced by unbalanced power, states try to in-crease their own strength or they ally with others tobring the international distribution of power into bal-ance. The reactions of other states to the drive fordominance of Charles I of Spain, of Louis XIV andNapoleon Bonaparte of France, of Wilhelm II andAdolph Hitler of Germany, illustrate the point.Will the preponderant power of the United Stateselicit similar reactions? Unbalanced power, whoeverwields it, is a potential danger to others. The powerfulstate may, and the United States does, think of itself asacting for the sake of peace, justice, and well-being in

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Evaluating Theories December llJlJ7the world. These terms, however, will be defined to theliking of the powerful, which may conflict with thepreferences and interests of others. The powerful statewill at times act in ways that appear arbitrary and highhanded to others, who will smart under the unfairtreatment they believe they are receiving. Some of theweaker states in the system will therefore act to restorea balance and thus move the system back to bi- ormultipolarity. China and Japan are doing so now.In international politics, overwhelming power repelsand leads others to balance against it. Stephen Walt(1987, viii, 5, 21, 263-5) has offered a reformulation ofbalance-of-power theory, believing that states balancenot against power but against threat. Vasquez seesWalt's "refinement" as placing a semantic patch on theoriginal theory in an attempt to rescue it from falsifyingevidence. I would agree if I took Walt's reformulationto be the correction of a concept that increases theexplanatory power of a defective theory and makes itmore precise. Changing the concepts of a theory,however, makes an old theory into a new one that hasto be evaluated in its own right. I see "balance ofthreat" not as the name of a new theory but as part ofa description of how makers of foreign policy thinkwhen making alliance decisions. Theory is an instru-ment. The empirical material on which it is to be usedis not found in the instrument; it has to be adduced bythe person using it. Walt makes this clear when hedescribes "threat" as one of the "factors that statesmenconsider when deciding with whom to ally" (p. 21). Inmoving from international-political theory to foreign-policy application one has to consider such matters asstatesmen's assessments of threats, but they do notthereby become part of the theory. Forcing moreempirical content into a theory would truly amount toa "regressive theory shift." It would turn a generaltheory into a particular explanation. Vasquez, andWalt, have unfortunately taken the imaginative appli-cation of a theory to be the creation of a new one.Vasquez makes a similar mistake in his appraisal ofChristensen's and Snyder's (1990) essay, "Chain Gangsand Passed Bucks." "The authors," according toVasquez, "find a gap in Waltz's explanation [of Euro-pean diplomacy preceding World War II] and try tocorrect it by bringing in a variable from Jervis" (p. 906).However good or bad my brief explanation of whathappened in Europe prior to World War II may be(Waltz 1979,164-70), an explanation isnot a theory. Atheory does not provide an account of what has hap-pened or of what may happen. Just as a hammerbecomes a useful tool when nails and wood are avail-able, so a theory becomes useful in devising an expla-nation of events when combined with informationabout them.The question is not what should be included in anaccount of foreign policies but what can be included ina theory of international politics. A theory is not amere collection of variables. If a "gap" is found in atheory, it cannot be plugged by adding a "variable" toit. To add to a theory something that one believes hasbeen omitted requires showing how it can take its placeas one element of a coherent and effective theory. If

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that were easy to do, we would be blessed with a wealthof strong and comprehensive theories.I conclude by emphasizing a few points about thetesting of theories. A theory's ability to explain ismoreimportant than its ability to predict. At least StevenWeinberg and many others think so. Believing thatscientists will one day come up with a final theory, hewrites that even then we will not be able "to predicteverything or even very much," but, he adds, wewill beable to understand why things "work the way they do"(1992, 45; cf. Toulmin 1961, 36-8). Success in explain-ing, not in predicting, is the ultimate criterion of goodtheory. Theories of evolution, after all, predict nothingin particular.Vasquez makes the testing of theories seem easy byadopting a positivist standard: Does the observationmade correspond with a theory's prediction? His adop-tion of such a standard is shown by his crisp assertionthat the failure of states to balance "in the periodbefore World War II ... should be taken as falsifyingevidence" (p. 906). Yet what is to be taken as evidencefor or against a theory is always in question. Someattempts to balance were made in the prewar years, buta balance formed, so to speak, only in the end. Shoulddelay in completing a balance be taken as evidencecontradicting balance-of-power theory? One may notbe able to answer the question decisively. Testingtheories is an uncertain business. In this case, however,one should certainly remember that the theory beingtested explains the process of balancing as well aspredicting that balances recurrently form. The theorycannot say how long the process will take.The title of Errol Harris's (1970) book, Hypothesisand Perception, implies a criticism of Popper's claimthat a critical test of a hypothesis, if flunked, falsifies atheory once and for all. As Harris suggests, our per-ceptions count; the results of tests require interpreta-tion. Evaluating a theory requires working back andforth between the implications of the theory and anuncertain state of affairs that we take to be the realityagainst which the theory is tested. Whether or notevents in the 1930s tend to validate or to falsify myversion of balance-of-power theory depends as muchon how one interprets the theory as on what happened.However thorough the evaluation of a theory, we cannever say for sure that the theory is true. All the more,then, we should test a theory in all of the ways we canthink of-by trying to falsify and to confirm it, byseeing whether things work in the way the theorysuggests, and by comparing events in arenas of similarstructure to see if they follow similar patterns. Wein-berg suggests yet another way. "The most importantthing for the progress of physics," he writes, "is not thedecision that a theory is true, but the decision that it isworth taking seriously" (1992, 103). The structuraltheory set forth in my Theory of International Politics atleast passes that test.REFERENCESBochenski, J.M. 1965. The Methods of Contemporary Thought, trans.Peter Caws. Dordrecht: D. Reidel Publishing.


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American Political Science Review Vol. 91, NO.4Christensen, Thomas J., and Jack Snyder. 1990. "Chain Gangs andPassed Bucks: Predicting Alliance Patterns in Multipolarity."International Organization 44(Spring):137-68.Conant, James B. 1947. On Understanding Science. New Haven, CT:Yale University Press.Harris, Errol E. 1970.Hypothesis and Perception. London: Allen andUnwin.Hotelling, Harold. 1929. "Stability in Competition." Economic Jour-naI39(March):41-57.Kegley, Charles W., Jr. 1993. "The Neoidealist Moment in Interna-tional Studies? Realist Myths and the New International Reali-ties." International Studies Quarterly 37(June):131-46.Keohane, Robert 0., and Joseph S. Nye. 1989. Power and Interde-pendence, 2d ed. New York: Harper Collins.King, Gary, Robert Keohane, and Sidney Verba. 1994. DesigningSocial Inquiry: Scientific Inference in Qualitative Research. Prince-ton, NJ: Princeton University Press.Lakatos, Imre. 1970. "Falsification and the Methodology of ScientificResearch Programmes." In Criticism and the Growth of Knowledge,ed. Imre Lakatos and Alan Musgrave. Cambridge: CambridgeUniversity Press.Nagel, Ernst. 1961. The Structure of Science: Problems in the Logic ofSCientificExplanation. New York: Harcourt, Brace and World.Popper, Karl R. 1959. The Logic of Scientific Discovery. London:Hutchinson.Schroeder, Paul. 1994. "Historical Reality vs. Neo-Realist Theory."International Security 19(5ummer):108-48.

Schweller, Randall L. 1994. "Bandwagoning for Profit: Bringing theRevisionist State Back In." International Security 19(5ummer):72-107.Stent, Gunther S. 1973. "Shakespeare and DNA." New York Times,January 28, sec. E.Sumner, William Graham. [1911]1968. "War." In War: StudiesfromPsychology, Sociology, Anthropology, ed. Leon Bramson andGeorge W. Goethals. New York: Basic Books.Toulmin, Stephen. 1961. Foresight and Understanding: An Enquiryinto the Aims of Science. New York: Harper and Row.Vasquez, John A. 1997. "The Realist Paradigm and Degenerativeversus Progressive Research Programs: An Appraisal of Neotra-ditional Research on Waltz's Balancing Proposition." AmericanPolitical Science Review 91(December):899-912.Walt, Stephen M. 1987. The Originsof Alliances. Ithaca, NY: CornellUniversity Press.Waltz, Kenneth N. 1979. Theory of International Politics. New York:McGraw Hill.Waltz, Kenneth N. 1986. "Reflections on Theory of InternationalPolitics: Response to My Critics." In Neorealism and Its Critics, ed.Robert O. Keohane. New York: Columbia University Press.Waltz, Kenneth N. 1990. "Realist Thought and Neorealist Theory."Journal of International Affairs 44(Spring/Summer):21-37.Waltz, Kenneth N. 1993. "The Emerging Structure of InternationalPolitics." International Security 17(Fall):44-79.Weinberg, Steven. 1992. Dreams of a Final Theory. New York:Pantheon Books.

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evaluating theories - kenneth waltz

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