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Assessing Kenneth Waltz's Theory of International Politics: the challenge of parsimony
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“The devil is in the details”, as the saying goes.        

Structural realism’s founder Kenneth Waltz seemed to have particularly valued this phrase as he rigorously applied it when he authored his seminal book. Theory of International Politics (hereinafter referred to as TIP) published in 1979, is indeed characterized by a constant search for simplicity that probably makes of it one of the most parsimonious theories of International Relations. This quest for parsimony is at the heart of some of the main lines of both positive and negative critiques faced by the essay.       

The methodological value of the book though, even if it is not immune from criticisms, appears to be its most unanimously acknowledged element. The work undertaken by Waltz in Chapter 1 on the meaning of theory, and the thorough identification of the limitations of previous efforts to create a theory of international politics (chapters 2, 3, 4) are arguably widely recognized as a strong contribution of the book (Wivel, 2013).       
However, the theory itself has been the centre of the biggest debate in International Relations of the past three decades. Positing that anarchy is the ordering principle of the international sphere and that all the states are functionally alike and interested in their own survival, it argues that states have little choice but to rely on themselves and balance each other in order to maintain their position.  What is fundamentally new, as outlined above, is the unprecedented theoretical simplification this view entails. In Waltz’s world there are only two variables: an independent one (anarchy, i.e. the structure) and a dependent one (the distribution of capabilities across the units).                    

But what relevance does such a simple conceptual framework have for actual international politics? What real explanatory power a two-variable explanation may have? Can it be simple without being simplistic? Does it allow for the generation of infinite substantive explanations or is it too systemic to be applicable to the empirics?

The question I will hence try to address in this essay is whether the parsimony of Waltz’s theory allows it to elucidate world’s politics or, on the contrary, has a deleterious obscuring effect on our understanding of it.         
To that end, I will first take care not to use the wrong assessment criteria and not to assess TIP on grounds it is not seeking to explain. I will therefore clarify the fact that Waltz does not pretend to explain every feature of international politics but rather seeks to identify their transhistorical structure. Second, historical investigations will show that he does not succeed in this attempt to find the structure due to the overly rigid nature of his theory. Third, I will show that TIPs work of parsimony had nevertheless a very virtuous effect on our understanding of actual international politics in an indirect manner: the renewal of the IR discipline it triggered.    

Overall, I will argue that, paradoxically, Waltz’s simplifying approach, which sets up the possibility of a universal applicability, undermines its prospects as a viable approach to international history but that it is precisely what constitutes its formidable generative impact on IR scholarship.       


First, if one wants to assess TIP’s relevance to actual international politics, one has to clarify what Waltz’s pretensions really are. Tellingly, this is the first thing he himself does when responding to Keohane, Ruggie, Ashley, and Cox in “A Response to my Critics” (Waltz, 1986). As I will try to show below, if Theory is to be attacked for containing “little of substance on actual international politics,” we have to keep in mind that being low on theoretical “substance” is precisely the aim of the author: it is precisely from this “spare” structure (as he calls it itself; Waltz, 1986), seen as the constant and universal pattern of international that he intends to derive infinite explanations. We should, therefore, first figure out which are the irrelevant and relevant criteria to assess such a theory.

Let us start with what Waltz is really trying to do. The general point of chapters 1 to 4 (Waltz, 1979) is to demonstrate analytical priority to devise a structural theory. It is the conclusion of chapter 4: necessary because certain things keep occurring (even though states (units) change throughout the centuries). As he makes it clear in a later piece: “since variations in unit level causes do not correspond to variations in observed outcomes one has to believe that some causes are located at the structural level of international politics as well” (Waltz K., 1990).

Discussing this analytical priority is beyond the scope of that essay and I shall therefore take it as a given. Suffice it to underline that such a view is based on the rejection of reductionism (which are by definition inductive, moving from a unit-level perspective to the system (international relations). Also in line with his emphasis on parsimoniousness, according to Waltz, “structures never tell us all that we want to know. Instead, they tell us ‘a small number of big and important things (Waltz, 1986). Structural realist’s theory stands therefore for helping one to comprehend the general trend of things.

What this means for this essay’s investigation is that the accurate device to assess TIP’s relevance to actual international politics is by no mean its applicability to any unit-level historical event. For instance, it does not seek to be able to explain every single foreign policy state individual strategy, nor does it aim at accurately describing the complexity of world politics.

A few more things are worth noting regarding the appropriate ground on which to judge TIP. Firstly, as highlighted by Keohane (1986), this theory is by nature unfalsifiable, by virtue of being not rooted in the empirics, being deductive as opposed to inductive, and more importantly, because the structure is not “fully generative” (Waltz, 1986) and therefore exert only an influence and not a constraint on units. Secondly, it would make little sense to challenge the validity of Waltz’s assumptions, as he is not claiming they are valid, but useful.  According to him, assumptions are in fact “radical simplifications of the world, and they are useful only because as such” (Waltz, 1990). Thirdly, as a result, all the theoretical attempts made by other scholars to make his structural model more complex were rejected by Waltz. Thus, scholars like Ruggie (who critiqued the “truncated” character of the structure and proposed to take into account the changing patterns of sovereignty [Ruggie, 1986]), and Sorensen (2009) would have expanded the structure to make it more sensitive to domestic changes. 

Different attempts of that kind were discarded by Waltz for being “reductionists”, or not being sufficiently important to be part of the few “big and important things” that constitute the structure. Many have then highlighted the circular nature of Waltz’s line of defense. In his various response papers (such as “A response to my critics” (1986) or “Evaluating theories” (1997)) he often merely repeated is his original positions (Wivel, 2013).

An “internal” assessment of TIP’s relevance to international politics, i.e. a critique that would try to demonstrate theoretically the lacking character of the structure proposed by Waltz, or to logically nullify it, is therefore unfitted to the nature of Waltz’s theory. It seems that one should take it as a whole.           

What is a relevant criterion then?  To find it, looking in little more details to Waltz’s defense is enlightening. When, in “Continuity and Transformation in the World Orders” (1986), Ruggie criticizes the incomplete nature of structural realism’s structure and calls for additional elements to be accounted for, Waltz responds along two major lines. First, he repeats that the structure ought to be simple, parsimonious, as the only way to avoid the “slippery slope towards reductionism” and unit-level explanations. Second, when led to justify why his view of the simple structure is the right one, he states that it is because it “remains strikingly constant”. “We can look farther afield, he adds, for example to the China of the warring states.”
This seems to finally point toward a valid assessment criterion based on the following question: is neorealist's structure really “strikingly constant” across time and space? Indeed, TIP does not seek to explain everything but claims to have identified the universally applicable structure of international politics. Waltz theory’s explanatory power thus rests on the validity of this claim. In other words, the question whether his parsimonious model allows elucidating world politics has to be assessed through a broad historical investigation of it[1].


This investigation should include the major features and consequences of the neo-realist view of the structure, such as anarchy, polar systems and balance of power.

As for anarchy, the authoritative historical study led by Lake (2009) has well shown that much of the international history has been one of hierarchical relations between powerful states’ building order and weaker states submitting to it in exchange for “services” such as order, security, and governance. It has taken different forms, includingr spheres of influence, empires, tributary systems, hegemonic orders, and patron-client relations. 

As far as polar systems are concerned, the discrepancy between theory and history is even more striking.  Waltz, who is very big on accounting for the dynamics behind the bipolar Cold War system (Chapter 7 of TIP) and on contrasting bipolar and multipolar systems, never foresaw the emergence a unipolar system, which eventually happened after 1991 (Wivel, 2013)[2].

More generally, several thorough historical surveys on the balance of power came to the similar conclusions. In Balance of Power: Theory and Practice in the 21st Century, Paul, Wirtz, and Fortmann (2004) concluded that “few social science theory can be said to be universally valid … the balance of power is not exception.” The exact same argument is made in The Realism Reader (Elman and Jensen, 2013).

Even period-based approaches seem to nullify Waltz’s claim of a constant and universal international structure. Diplomatic historian Paul Shroeder (1994, 1992, 2010) published a number of historical comprehensive studies showing that, even over the period when structural realist’s principles were supposed to be successfully applicable (the whole Westphalian era from 1648 to 1945), Waltz’s model fails to fit in the historical events (unless selectively taken to suit the model) and the study of this period evidences “inextricably intertwined quests for order”.         

Hence, it is rather clear that due to its too high parsimony (as underlined by Humphreys, 2006[3]) TIP’s claims to universality fall (Wivel, 2013). Buzan and Little (2009) summed it up that way:  “As Cox asserted, for example, Waltz’s attempt to achieve theoretical clarity comes at the cost of an ‘unconvincing mode of historical understanding’.”


But is it to say that TIP (and its simplicity) did not make any contribution to our understanding of actual international politics, or worse, that its simplistic nature had nothing but an obscuring impact? Surely, it is not the case, if we look Waltz’s contribution from another perspective: that of the discipline of IR.          

No one can deny that TIP deeply reshaped the terms of the debate in IR (Wivel, 2013) and engendered major development in that field. Not only did it enrich the realist tradition but it allowed liberals to work with new concepts, even which they derived different predictions from it (Trubowitz, 2015). Its unprecedented parsimony plays a crucial role in this seminal effect. As Buzan and Little put it, “his work still survives as a focal point for the field primarily because he expresses his position in such clear and unequivocal terms (Ibid.).” More, “most of the major theoretical advances made in the field over the last 30 years have come about as the result of theorists attempting to either challenge or qualify Waltz’s theoretical stance.”

In sum, if one adopts a scientific or critical realist meta-theoretical approach, TIP’s indirect impact on our ability to understand actual international relations has been massive.

Is “Theory of International Politics contains little of substance on actual international politics” a valid point to make?            

What stems from this analysis –in which I paid a particular attention not to evaluate the discussed theory by alien criteria and therefore not to blame it for not being able to explain all the complexities of international politics– can be summarised as follows. The parsimony of Waltz’s work prevented its claim to have established a universal framework of explanation, valid across time and space. Its applicability to history is therefore limited and its relevance to actual international relations is partial. In a sense, Waltz’s parsimony gamble has been lost. Indeed, by creating a deductive, unfalsifiable, purely theoretical model, based on unproven assumptions, he had two options: either he had discovered an infinite source of explanations of international politics, either he got the story wrong. But Theory of International Politicss relevance for actual international relations is to be found elsewhere. Its very parsimony made of it the most valuable “methodological” tool for IR scholarship of the last three decades of IR research.         

As Kratochvil provocatively puts it “errors have their advantages.” 

Nathanaël Chouraqui is enrolled in an MSc. in International Relations at the London School of Economics and Political Science and simultaneously pursuing an LLB at the Sorbonne Law School. He holds a B.A. in Government obtained at Sciences Po, Aix. Mr. Chouraqui is also  Head of the Research Team of the LSE Near Eastern Studies Society (LSE NESS) and President and co-founder of the European Forum of Middle Eastern Studies Society (EFMESS). He previously worked for the Ministry of Foreign Affairs of France as an intern an economic analyst. 



Buzan, B. and Little, R. (2009). Waltz and World History: The Paradox of Parsimony. International Relations, 23(3), pp.446-463.


Dunne, T., Kurki, M. and Smith, S. (2007). International relations theories. Oxford: Oxford University Press.


Elman, C. and Jensen, M. (2013.). Realism reader.


Humphreys, A. (2006). Kenneth Waltz and the Limits of Explanatory Theory In International Relations.


Keohane, R. (1986). Neorealism and its critics. New York: Columbia University Press.

Keohane, R. (1986) Theory of World Politics Structural Realism and Beyond. In: R. Keohane, ed., Neorealism and its critics, 1st ed. Columbia University Press.

Kratochwil, F. (1984). Errors have their advantage. International Organization, 38(02), p.305.

Lake, D. (2009). Hierarchy in international relations. Ithaca, NY: Cornell University Press.

Paul, T., Wirtz, J. and Fortmann, M. (2004). Balance of power. Stanford, Calif.: Stanford University Press.

Ruggie, J. (1986). Continuity and Transformation in the World Politics: Toward a Neorealist Synthesis. In: R. Keohane, ed., Neorealism and its critics, 1st ed. Columbia University Press.

Schroeder, P. (1992). Did the Vienna Settlement Rest on a Balance of Power?. The American Historical Review, 97(3), p.683.

Schroeder, P. (1994). Historical Reality vs. Neo-Realist Theory. International Security, 19(1), p.108.

Shroeder, P. (2010). 'Not even for the Seventeenth and Eighteenth Centuries: Power and Order in the Early Modern Era'. In: E. May and R. Rosecrance, ed., History and neorealism, 1st ed.

Sorensen, G. (2009). `Big and Important Things' in IR: Structural Realism and the Neglect of Changes in Statehood. International Relations, 23(2), pp.223-239.

Waltz, K. (1979). Theory of international politics. Reading, Mass.: Addison-Wesley Pub. Co.

Waltz, K. (1986) Reflections on Theory of International Politics: A Response to My Critics. In: R. Keohane, ed., Neorealism and its critics, 1st ed. Columbia University Press.

Waltz, K. (1990). Nuclear Myths and Political Realities. The American Political Science Review, 84(3), p.731.

Waltz, K. (1997). Evaluating Theories. The American Political Science Review, 91(4), p.913.

Waltz, K. (2000). Structural Realism after the Cold War. International Security, 25(1), pp.5-41.

Wivel, A. (2013). The politics of international theory: reading Waltz 979 as a classic. In: Classics of International Relations: Essays in Criticisms and Appreciation, 1st ed. Taylor and Francis.

[1] Of course, Waltz’s theory remains infalsifiable and we will therefore not be able to find an unquestionable evidence of its validity or invalidity. But a historical broad assessment should enable us to estimate the ability of the theory to be applied transhistorically and therefore its explanatory power.

[2] The only answer given by Waltz to this situation is that, citing his own theory, such a system cannot last. “As nature abhors a vacuum, so international politics abhor unbalanced power” (Waltz 2000).

[3] “...the primary problem that Waltz faces when attempting to apply his theory to specific empirical problems in international relations is the limited logic of the theory.”

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