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date: 20 April 2024

Complexity and Quantum in International Relationsfree

Complexity and Quantum in International Relationsfree

  • Greta Fowler SnyderGreta Fowler SnyderWilliams College
  •  and Andre HuiAndre HuiWilliams College


Even as work in the natural sciences has shown the Newtonian understanding of the world to be faulty, Newtonianism still pervades the field of International Relations (IR). Moved by the challenges to Newtonianism emanating from various fields, IR scholars have turned to complexity theory or quantum physics for an alternative onto-epistemological basis on which to build a post-Newtonian IR. This article provides researchers with a map that allows them to not only better see and navigate the differences within both complexity and quantum theory and the IR work that draws from each, but also to recognize the similarities across these bodies of work. Complexity theory highlights and engages systems (biological, social, meteorological, technological, and more) characterized by emergence, self-organization, nonlinearity, unpredictability, openness, and adaptation—systems that are fundamentally different from the self-regulating mechanic systems that comprise the Newtonian world. Complexity-grounded IR research, following complexity research more generally, falls into one of two categories. Through “restricted complexity” approaches, researchers use simulation or modeling to derive knowledge about the dynamics of complex social and political systems and the effect of different kinds of interventions. Researchers who take “general complexity” approaches, by contrast, stress the openness and entwinement of complex systems as well as unpredictability that is not exclusively the result of epistemological limitations; they offer critical re-theorizations of phenomena central to IR while also using qualitative methods to demonstrate how complexity-informed understandings can improve various kinds of practices. “Restricted complexity” seems to have gained the most traction in IR, but overall, complexity has had limited uptake. Quantum physics reveals a world with ineluctable randomness, in which measurement is creative rather than reflective, and where objects shift form and seem to be connected in ways that are strange from a Newtonian perspective. IR research that builds from a quantum base tends to draw from one of two categories of quantum physical interpretation—the “Copenhagen Interpretation” or pan-psychism—though more exist. Unlike the complexity IR community, the quantum IR community is ecumenical; given the deep ongoing debates about quantum mechanics and its meaning, embracing different ways of “quantizing” IR makes sense. Most quantum IR work to date stresses the utility of the conceptual tools that quantum physics provides us to rethink a wide variety of socio-political phenomena and hedges on questions of the nature of reality, even as the major theoretical tracts on quantum social science take strong ontological stances. Developing critiques and alternative positive visions for IR on the basis of either complexity theory or quantum work has been an important first step in enabling a post-Newtonian IR. To advance their agenda, however, the critics of Newtonian IR should start engaging each other and carefully interrogate the relationship between different strands of complexity and quantum theory. There are a number of key points of overlap between the work in the general complexity strand and the Copenhagen Interpretation–inspired philosophy of agential realism, and as of 2022 there exists only one major effort to bring these strands of quantum and complexity together to found a post–Newtonian IR. A coordinated post-Newtonian challenge that brings complexity-grounded IR scholars together with quantum-grounded IR scholars under a common banner may be necessary to wake IR from what Emilian Kavalski calls its “deep Newtonian slumber.” The pay-off, post–Newtonian IR scholars argue, will be a deeper understanding of, as well as more effective and ethical engagement with and in, a non-Newtonian world.


  • Ethics
  • International Relations Theory
  • Qualitative Political Methodology
  • Quantitative Political Methodology

In the work that became a cornerstone of modern Western scientific philosophy and practice, Isaac Newton painted a portrait of the universe as composed of discrete objects operating in mechanistic ways. Newtonianism—an intellectual paradigm that springs from Newton’s ideas (Louth, 2011)—provides the default ontological, epistemological, and ethical assumptions for much of the work in Western international relations (IR) that lays claim to being “scientific.”1 The reach of Newtonianism in IR becomes surprising, however, when one learns that its core tenets have been attacked from multiple angles not just by science skeptics, but also by true believers who hail from fields including physics, biology, and chemistry, among others. If Newtonian assumptions about the nature of the universe are faulty as leading natural scientists have claimed, and Newtonian assumptions are pervasive in IR, then we are forced to ask: Is IR offering a (somewhat? largely? fundamentally?) misleading picture of the world?2

The revolutionary findings of natural science-based critics of Newtonianism must be taken seriously by IR scholars, regardless of how difficult the epistemological and ethical questions they raise are (and they are difficult). A growing number of what might be called “post-Newtonian” IR scholars do just this, seeking to shift IR onto scientifically firmer ground.3 At the time of writing in 2022, nearly all post–Newtonian IR scholars look either to a body of work known as complexity theory or to a body of work known as quantum theory to ground their work.

There are surely a number of reasons why scholars have focused solely on one of these post-Newtonian foundations to the exclusion of the other—one is sufficient for the purposes of the scholar; lack of awareness of the other; the difficulty of coming to grips with yet another challenging set of ideas emanating from very different disciplines; the difficulty of trying to assess competing ideas about what the empirical findings emanating from quantum and complexity research mean theoretically, philosophically, and what they imply methodologically; the difficulty of determining how work from one foundation relates to work from the other. But it’s also worth noting that complexity and quantum have been portrayed as incongruous by those who are at the forefront of post–Newtonian IR scholarship (Wendt, 2015, p. 147). While specific strands of complexity theory have rightly been criticized for remaining Newtonian in certain fundamental respects and thus are indeed at odds with quantum ontologies, other strands of complexity theory entail a thoroughgoing rejection of Newtonianism and overlap with specific quantum strands. Understanding complexity and quantum as fundamentally incompatible is misleading -- or at the very least premature -- and it weakens the post-Newtonian challenge.

This article provides researchers with a map that allows them to not only better see and navigate the differences within both complexity and quantum theory and the IR work that draws from each, but also to recognize the similarities across these bodies of work. Going through either complexity or quantum has been a necessary first step in developing a post-Newtonian IR. But to advance their agenda, quantum and complexity IR scholars should more carefully interrogate the relationship between complexity and quantum and engage each other. Are they working with the same ontological assumptions? Toward the same (epistemological and ethical) end? Do they alight on the same methodologies? To what extent and in what ways can their work build on each other’s? What is their vision of the future of IR? The differences between (at least some) complexity and quantum IR pale in comparison to their differences with Newtonian IR—and largely unappreciated commonalities may make such camps well-suited to join forces in an effort to move the discipline’s center of gravity.

Section one provides an outline of the key features of the Newtonian paradigm that complexity and quantum theory challenge. Complexity theory is explained in section two; following the major dividing line within complexity research generally, complexity-based IR research hews either to a “restricted” or “general” complexity view.4 A brief overview of the revolution that is quantum mechanics and philosophies associated with it is offered in the third section, along with a review of quantum-based IR work that is organized by ontological and philosophical commitments. The fourth section puts complexity and quantum philosophies in conversation, and discusses in detail one promising initial effort to bring the two together to build a post-Newtonian foundation for IR.

“The . . . Yardstick Against Which the Value of International Relations Research Is Often Measured”: Newtonianism Defined

Newtonianism starts with the ontological assertion that the universe is composed of discrete entities in an empty background of space and time (Kurki, 2020, p. 44). These discrete entities move in ways that are invariant across time and space, or according to “universal” laws. In Newtonianism, these universal laws hold beyond the specific physical bodies Newton centered, serving as the basis for the assumptions that (a) phenomena will behave linearly (in keeping with Newton’s second law, which asserts proportionality between force/cause and motion/effect) and (b) the whole can be understood by summation (in keeping with Newton’s third law, which suggests change in motion can be understood as the sum of total of forces acting on the entity). The core metaphor of the Newtonian paradigm—the universe as a well-ordered machine—thus emerges. The world and beyond is oriented toward order and equilibrium; actions of bodies within it are deterministic and predictable.

Epistemologically, Newtonianism holds that we humans are capable of knowing the definitive properties of discrete entities and the laws that entities obey in their interaction with one another. This knowledge is born of experience combined with a capacity for reason that gives us access to the deep structure of the universe (Kurki, 2020, p. 27; Louth, 2011, p. 72). Precise measurement and careful adherence to proper method produces objective knowledge. Different measurement tools (if properly constructed, calibrated, and employed) applied to understand the same aspect of the same phenomenon will produce the same findings because the properties and behavior of entities are independent of the tools used to measure them. Objects can be measured without being affected by the measurement. The universe is solvable; her mysteries give way to human understanding in the form of parsimonious laws.

Understanding the epistemology of Newtonianism brings its ethics into focus. Because we are capable of objective knowledge, we should strive for it. Because we are capable of understanding the deep structure of the universe, we should seek out universal laws. And armed with this knowledge, we humans—particularly privileged and efficacious actors because of our capacity for knowing and doing based on the knowing—can and should manipulate entities in the world to serve our (moral) ends (Kurki, 2020, p. 4).

We see Newtonianism’s mark on International Relations, then, in work that does one or more of the following:

“Prioritize[s] ‘humans’ and their interactions as the core subject matter of IR” (Kurki, 2020, p. 17).

“Privilege[s] the study of ‘things’ (such as states, individuals) against ‘backgrounds’ (material resources, environment)” (Kurki, 2020, p. 17).

“Reduce[s] ‘relations’ to ‘interactions’ of things (international relations, transnational relations, networks of ‘nodes’)” (Kurki, 2020, p. 17).

Aims to uncover “fundamental laws” of politics and/or society that are timeless, universal in their reach, elegant in their simplicity.

Suggests that knowledge produced through proper procedure is objective and independent of the researcher and measurement apparatus.

Encourages actors to wield this knowledge of deterministic dynamics to exercise control over the present and over the future.

“The World Is Not a Machine, for Better or for Worse”: Complexity Theory and International Relations

Complexity Theory is an umbrella term for a heterogenous body of thought that emphasizes the importance of systems thinking and the difference that complexity (understood in a specific sense defined below) makes when it comes to understanding systems (Orsini et al., 2020, p. 1012). It emerged from the study of widely varying phenomena, including weather systems (the mathematician-meteorologist Edward Lorenz; Sokol, 2019), nonequilibrium thermodynamics (the chemist Ilya Prigogine [1997]), human cells (the biologist Stuart Kauffman (1996)), and capitalist markets (the economist Brian Arthur (2014)). From the small to large, human to nonhuman, scientists have repeatedly found a complexity that challenges the relatively simplistic Newtonian view of the world.

There are deep disagreements among complexity scholars about the essential attributes of systems that are labeled “complex.” Researchers across the complexity spectrum (Holland, 2014), however, agree that complex systems are characterized by5

The ability to self-organize. Elements in a complex system can order themselves without the influence of a central control, according to rules that spontaneously emerge from interactions among these elements.

Emergent properties. Complex systems possess properties that cannot be inferred simply by looking at the constituent elements of those systems.

Nonlinear behavior. Relatively minor changes in or to a complex system can result in major changes in the entire system’s trajectory.

Unpredictability. Self-organization, nonlinearity, and the difficulty of definitively knowing the key variables of complex systems are reasons that complex systems act unpredictably.

A significant subset of complexity researchers (Byrne & Callaghan, 2013; Smith & Jenks, 2013; Urry, 2005) also cites the following features as definitive:

Openness. Complex systems exchange energy, information, and materials with their external environment. They are both dependent on this flow and vulnerable to it.

Adaptivity. The survival of complex systems in the context of an ever-changing environment requires adaptation, which is facilitated in part by the capacity to self-(re-)organize.6 This characteristic, along with openness, adds to system unpredictability.

Complexity theory calls a number of the key elements of the Newtonian imaginary into question. Against the idea of a machine-like universe, in the world of complexity, systems are not a mere sum of their parts; they are different than the sum of their parts, with emergent system-level properties that sometimes act to inhibit or change the properties of the parts. Further, the picture of the universe as composed of discrete objects that enter interactions with one another is challenged by the de facto interwovenness of complex systems; as political scientist Neil E. Harrison puts it, the definition of boundaries in the study of complex systems “is a convenience used to assist human analysis” (2007, p. 2). Like the systems themselves, cause and effect are not readily separable. “The idea of a recursive loop . . . obliges us to break our classical ideas of product → producer, and of cause → effect,” says philosopher Edgar Morin. “Causes produce effects that are necessary for their own causation” (Morin, 2007, p. 14). Moreover, we cannot talk about universal laws; the same cause may not have the same effect in the same system at two different points in time. And sometimes cause is not proportional to effect as Newtonians posits it will be. The complex universe, then, is defined by flux and unsettledness rather than self-regulation and order.

Not all strands of complexity theory, however, call the Newtonian imaginary into question in the same way or to the same extent. One of the most significant rifts within the work done under the banner of complexity can be found in regard to whether complex systems are rightly understood as deterministic or not. Chaos theory—which some (Manson, 2001) consider a branch of complexity theory while others portray as a precursor (Bousquet & Curtis, 2011)—illuminates systems that are deterministic but unpredictable.7 They are unpredictable because the researcher cannot exhaustively know the systems’ initial state and because small variations have major consequences over large time scales; chaos, then, refers to “apparent disorder and unpredictability” (Morin, 2007, p. 8). Other complexity thinkers suggest that “the more we know about our universe”—it’s irreversibility and instability—“the more difficult it becomes to believe in determinism” (Prigogine, 1997, p. 155).8 On this view, complex systems are determined inasmuch as the range of future possibilities are limited by its past and present. But they are not deterministic: initial conditions will not allow the observer to know and predict the future, and not just because of the limitations of her knowledge.9 The inability to predict is in part a function of what the political theorist William Connolly calls “onto-unknowns.” “Real creativity,” Connolly claims, “may be triggered by the excitation of ‘teleodynamic searching processes’ in [self-organizing] complex processes, whereby a new formation arises out of a disturbance without being entirely caused by it” (2013, p. 15).

The debate about whether complex systems are deterministic has significant epistemological and methodological implications, among others, but further thorny questions are raised by the issue of how to understand emergence. What Morin calls a “restricted” view of complexity emphasizes emergence in complex systems as “the result . . . of interactions at a simpler level” (Byrne & Callaghan, 2013, p. 41). This approach enables a science of complexity anchored by modeling and simulation. In this science of complexity, stylized versions of systems of interest are created and abstracted from a more complicated context, and different intuitions and interventions are tested, enabling (advocates say) both an understanding of fundamental dynamics of systems of interest and the ability to effectively manipulate complex systems in the world. Explaining why he dubs this understanding of complex systems “restricted,” Morin says, “to some extent, [the researcher working in a restricted complexity vein] recognizes complexity, but by decomplexifying it” (2007, p. 10).

Restricted complexity decomplexifies complexity by ignoring that emergence can be the result not only of interactions of “parts” at a lower level, but also “of interactions at “higher levels” and/or across levels (Byrne & Callaghan, 2013, p. 45). It follows then that it also decomplexifies complexity by way of closure: even if a simulation, for instance, situates a system of interest in an environment that affects it, even if it builds in interconnections with other systems, this environment and these interconnections are necessarily “decomplexified.” A general view of complexity acknowledges the multiple sources of emergence as well as the importance of contextualization and attention to systems’ interconnections.10 General complexity requires analyses that honor the complex relation between part and whole, the interdependence of systems, and what Morin calls “the principle of ecology of action”: action escapes the “will and intention of that which created it” by “entering into interactions and multiple feedbacks” (Morin, 2007, p. 25).

Complex International Relations

The same variation and rifts that characterize complexity theory more generally have been imported into IR work that is informed by complexity theory. After a discussion of IR work that is grounded in a restricted view of complexity, we look at exemplary work that proceeds from a general complexity view.

Restricted Complexity in International Relations

Work that employs agent-based modeling (ABM) deserves pride of place in any discussion of IR scholarship that takes a restricted approach to complexity. In an article for the Annual Review of Political Science, de Marchi and Page observe that for most, “ABMs are synonymous with complexity” (de Marchi & Page, 2014, p. 2), though in fact they are but one methodology that can be deployed to understand complex systems. Most agent-based models consist of four key components: autonomous agents, an environment, interaction rules, and time. A computational engine “runs” the model by simulating the interactions between agents in an environment, showing how system behavior develops or how different changes to the system play out. Agent-based models allow researchers to study the interaction of diverse entities across different domains (and “spillover effects” between domains), to appreciate adaptation and its effect, to identify the important role of space in political outcomes, and to link behavioral rules to aggregate patterns or emergent properties (de Marchi & Page, 2014). Through these simulations, ABM advocates claim, we can generate intuitions, test established theories, explore the sensitivities of a theory to particular assumptions, predict outcomes, and see how different policy options might play out. Though ABM is part of the broader complexity science paradigm, Cioffi-Revilla (2017) notes that ABMs can be applied without complexity concepts; indeed, he notes, “few IR ABMs make extensive use of insights and understanding provided by complexity science.”

ABM has been used to illuminate a wide variety of phenomena of interest to IR scholars, and Cioffi-Revilla (2017) offers a comprehensive overview of the use of ABMs in IR, identifying “polity formation, foreign policy decision making, conflict and polity dynamics, transnational terrorism, politics of international trade, international cooperation, alliances, norms, and effects of climate change” as areas of study. Among the first and best-known work in this area of IR is Robert Axelrod’s bargaining simulation (Axelrod, 1984). Examining repetitive competitive interactions between autonomous rule-based actors, Axelrod shows cooperation (in particular, “tit-for-tat”) to be a better long-term strategy than betrayal, and argues that evolution selects for it. An unexpected outcome (cooperation in a world of egoists), then, is shown not to be random. Zooming in on an area not highlighted by Cioffi-Revilla—forced migration—scholars have built ABMs with the intention of predicting displacement events, refugee movement, and refugee destinations. Others ABMs have examined how humanitarian assistance policy affects the health and safety of refugee communities; and how a distribution center location may affect conflict between refugees and nonrefugees. The authors of a 2020 review on the use of ABM in forced migration research find the approach promising, and call for

expand[ing] the breadth of modeling beyond those of movement and prediction in order to answer the challenges posed by contextualized, place/time specific research questions, increased demands by theorists and policymakers to test our data and assumptions, and the wide variety of data being collected globally.

In addition to ABM, approaches associated with chaos theory, such as nonlinear dynamic modeling, have been imported into IR. Alvin Saperstein is perhaps the most prominent name associated with application of nonlinear dynamic modeling to politics (Kiel, 2000). In an article in Nature, Saperstein maintained the relevance of chaotic processes to arms races, suggesting that war should be seen as a “breakdown in predictability: a situation in which small perturbations of initial conditions . . . lead to large unforeseen changes in the solutions to the dynamical equations of the model” (Saperstein, 1984, p. 303). Wolfson et al. (1992) further elaborate on the nonlinear dynamics of international conflict. IR scholars have also asserted chaos’ applicability to regional stability (Kiel & Elliott, 1997), decision-making during international crises (Richards, 1990), and variation in conflict trajectories (Wolfson et al., 1992). Kiel (2000) offers an overview of nonlinear techniques and models in political science and public administration.

General Complexity in International Relations

A general complexity view, on the other hand, has been taken up by IR scholars for whom “a truly systemic approach to IR looks more like comparative politics than economics” (Donnelly, 2019). While James N. Rosenau’s (1990) Turbulence in World Politics highlights the utility of the conceptual vocabulary of complexity for shifting our perception of the international system, Robert Jervis’ (1998) System Effects constitutes the first deep and wide-ranging engagement with complexity thinking. Jervis asserts the limitations of dominant modes of “systems thinking” in IR (especially Kenneth Waltz’s realist model) and explains how an understanding of true “system effects” might improve actors’ engagement in a complex system interconnected with other complex systems. “With so many forces responding to each other,” Jervis (1998, p. 260) writes, “unintended consequences abound and the direct path to a goal often takes one in a quite different direction.” And yet, human actors do have methods to which they can turn to enable the realization of their goals, including constraining other actors, reducing environmental uncertainty, and enacting multiple interventions (see Boulton, 2010, for further ideas about how a general complexity perspective can inform policy-making). Some use knowledge of complex systems to argue for a particular approach in a particular area, as Parfitt (2006) does when he argues that complexity-associated participatory approaches to development should be combined in “creative tension” with top-down approaches. Others see “complexity-infused” perspectives already being put to work; De Coning (2018), for instance, offers the pragmatic turn in peacebuilding—which he calls “adaptive peacebuilding”—as an example of action which reflects a growing understanding of the nature of complexity, while Bousquet (2008) talks about the incorporation of complexity thinking into military operations.

Following Jervis, a number of scholars have sought to retheorize what they variously refer to as the global system, international system, or international space as itself a complex adaptive system (Cudworth & Hobden, 2013; Deuchars, 2010). Others have focused the historical development of international relations and its key elements (like the emergence of global institutions [Modelski, 1996], the state [Chinen, 2014], and institutional resilience [Root, 2013]), or phenomena like globalization (Urry, 2002; Walby, 2009).

While most IR scholars who approach their phenomenon of interest—whether that be the international state system, the international political economic system (Oatley, 2019), the humanitarian aid community (Seybolt, 2009), or terrorist networks (Bousquet, 2012)—from a general complexity perspective attend to the entwinement of social, economic, and political systems, Cudworth and Hobden (2013) further stress that it is vital to see the international system and systems within it as embedded in/interconnected with “nonhuman” systems as well. They develop a posthuman complex framework for the study of international relations, as others have called for (Bousquet, 2015; Kavalski, 2015a; Pereira & Saramago, 2020). Posthumanist complexity frameworks highlight natural and technological systems’ ability to act and affect human systems and designs. Indeed, it is worth noting that international environmental politics scholars were among the first to turn to complexity because they saw that human systems were open to non-human ones (and vice versa) and it gave them a framework for talking about the interaction of the “natural” and the “social” (Orsini et al., 2020, p. 1012). Emilian Kavalski, one of the proponents of the posthumanist approach, suggests that “one of the greatest ontological boons of a complexified IR,” writes, would be “the recognition of the ‘totality’ of human and non-human interactions in global life” (2015a, p. 257).

All of the work cited above offers methodological lessons, but sociologist David S. Byrne has arguably done the most concentrated work on the methodological entailments of general complexity. He maintains that qualitative comparative analysis is particularly useful when it comes to understanding phenomena via a general complexity framework (Byrne, 2005, 2013; Byrne & Callaghan, 2013, p. 201). Though qualitative approaches are dominant in IR work that takes a general complexity view, quantitative/computational methods are also represented. Root argues that network analysis—a set of techniques that allows for the visualization of relations among actors and analysis of emergent structure—is a key tool for studying complex systems. Using network analysis, for instance, Rakhyun E. Kim (2013) shows multilateral environmental agreements to be a self-organizing system with dynamic structure.

Critical engagement with IR work in the restricted complexity vein is another area of general complexity IR research. Some authors have suggested ways that restricted complexity approaches like ABM might be improved in light of these criticisms (Byrne & Callaghan, 2013). Other critics, however, are more dismissive of modeling and simulation. Members of this latter group claim that building a simulation on unproblematic assumptions is impossible, because actors simply cannot know the relevant agents, features of the environment, or behavioral rules. The simplification that is essential to the simulation is also pinpointed as a problem: “In politics, actors—whether states, IGOs, NGOs, terrorist cells, or voters—have expectations that are more than the simple rule models posited for complex adaptive agents” (Earnest & Rosenau, 2007, p. 158). Critics take issue with the way certain kinds of cross-level interactions and their emergent results are excluded (Byrne & Callaghan, 2013). Moreover, while simulations may examine interactions between systems and environment, they may still fail to accurately capture the openness of systems and the implications of this openness (Malaina, 2015); part of the lesson of generalized complexity is that outcomes are affected by physically, temporally, and conceptually “distant” systems and action between and within them. Finally, the “real creativity” of complex systems, generalized complexity, critics say, cannot be programed into a simulation.

Ideas from complexity theory like path dependence and positive feedback (Pierson, 2004) have become broadly accepted and highly influential in IR (Ma, 2007). Yet even as complexity-informed ideas hold weight—and assessments of the turn to complexity thinking argue that complexity has made a significant contribution to understanding change (Gunitsky, 2013; Lehmann, 2012)—only a fraction of articles in the fields of IR, political science, government and law, and public administration had complexity in their titles, abstracts, or keywords (Orsini et al., 2020, p. 1020). In their 2011 article, Antoine Bousquet and Simon Curtis lamented that complexity theory “continues to stubbornly remain on the margins of IR” (Bousquet & Curtis, 2011, p. 44); this seems just as true in 2022.

“Things Do Not Behave in Any Way That We Can Understand From Our Experience of the Everyday World”: Quantum Theory and IR

Though the quantum revolution in physics was catalyzed by the study of the molecular and submolecular levels, quantum mechanics is now recognized as the superior description of physical reality for all scales (Barad, 2007, p. 85; Gribbin, 1984, p. 92). Quantum mechanics, anchored by a mathematical formulism known as the Schrödinger equation, describes the aggregate behavior of particles with astonishing accuracy and is responsible for advances in many fields from computing to cosmology. And yet, even as the math “works,” physicists are deeply divided about what the math means.11 Adding strangeness on top of uncertainty, seminal experiments in quantum physics reveal a world in which phenomena like light and matter seem to transmogrify from one form (particle) to another (wave), a world in which objects seem to be in two places at once, a world in which two objects seem to instantaneously affect each other across large distances.

So what does the math of quantum physics tell us, and what does it not? Whereas in the Newtonian world an observer needs only a few data points to understand an object moving through space, an infinite collection of numbers are needed to understand object behavior in the quantum world. These “wave functions” are themselves deterministic, changing predictably over time. What they tell us, however, is not what a particular dynamic variable will definitively be upon measurement, but instead the probability of obtaining certain results upon measurement (Newton, 2004). Highlighting the major point of consensus in a sharply contested field, physicist Adam Becker writes that “the one thing that absolutely everyone agrees on . . . is that the outcomes of quantum physics experiments have an element of randomness” (Becker, 2018, p. 257). In quantum mechanics, the state (in a classic sense) and behavior of quantum objects cannot be known.

The randomness that appears in quantum physical experiments raises a long list of questions. Are probabilities the best we can do because of the nature of the world (physical reality isn’t deterministic) or because of incomplete knowledge (as a result of practical limitations with measurement or epistemological limitations, like we just don’t yet have the right theory)? How do we understand the relationship between experimenter, apparatus, measurement, and outcome? How/why do we get x particular value upon measurement? And what, if anything, can we say we “know” about the world outside of the confines of an experiment? Quantum philosophies that stake claims about the ontological and epistemological entailments and implications of quantum mechanics have proliferated. Here, we highlight only those that have exerted a significant influence on IR. But it’s important to be clear at the outset that quantum IR has by no means exhausted the array of possible quantum ontologies and/or epistemologies from which they could draw (Becker, 2018; Faye & Jaksland, 2021; Wendt, 2015).

Most work in quantum IR draws inspiration from what is referred to as the “Copenhagen Interpretation”—the understanding of quantum mechanics that is held by the majority of physicists as well (Barad, 2007, pp. 286–287; Becker, 2018).12 The Copenhagen Interpretation refers to the philosophies of major figures associated with the Institute for Theoretical Physics in Copenhagen, the most important incubator for quantum physics in the period of its emergence. Among these figures, Niels Bohr’s philosophy-physics has been particularly important.13 Bohr maintained that the relationship between the measurement apparatus and the object being observed is creative rather than reflective as in Newtonianism. Properties, then, can only be said to be knowable in an “objective” sense in the context of particular material experimental arrangements. Outside of experiments that measure a particle, for instance, we can’t say we objectively know a particle’s state or behavior as we can if we work with a Newtonian view. Further, inasmuch as the only information we can truly say we “know” in an objective sense is context-dependent, we may not be able to achieve complete objective descriptions of objects. While experiments allow us to definitively describe aspects of a particle, like, for instance, position or momentum, Bohr says there are certain variables—called “complementary variables”—that cannot be simultaneously measured. One apparatus is needed to measure position; another apparatus, incompatible with the first, is needed to measure momentum. The “contexts” that allow us to objectively know complementary variables are mutually exclusive, so the variables cannot be “known” simultaneously.

While some IR scholars work directly with the ideas of Bohr, more turn to Karen Barad’s retheorization of Bohr’s philosophy-physics. Barad, a professor of feminist studies, philosophy, and the history of consciousness who also holds a PhD in theoretical particle physics and quantum field theory, offers an idiosyncratic reading of Bohr that takes him to be making ontological claims: beyond engaging with the questions of what we can say we know and what can be known, Barad says, Bohr is saying something about the nature of the world.14 Barad suggests that Bohr poses a radical challenge to the Newtonian idea that the world is composed of discrete objects that we humans stand apart from and measure. We can’t objectively know particular variables outside of particular experimental arrangements because objects themselves don’t have determinate form outside of experimental arrangements. It is through the act of measurement that objects become discrete and properties determinate. Barad posits “phenomena” as ontologically prior to objects and measuring subjects; reality of course exists outside of measurement, but it is via intra-action (definitionally within phenomena) that subject and object become distinct. Apparatuses (always both material and ideational) and measurement are integral in establishing the split by which this separation occurs. Barad maintains over and against Bohr that humans are not the only agents or “actants” taking measurements; hence they use the language of “measuring agencies” rather than human subjects. Indeed, the formation we call “human” is made and remade in the act of “measurement.” The creativity of the act of measurement is not simply in its allowing for objective knowledge, but in actually making discrete objects; the uncertainty inherent in quantum physics, the instability, is a function of a world in which phenomena—that which gives rise to discrete objects—are perpetually in flux.

The second major quantum philosophy that has influenced IR is pan-psychism. This view posits that all matter is “minded” (i.e., conscious in some way). In moving from an indeterminate state represented by the superposition of possibilities calculated using the Schrödinger equation (the “wave function”) to a single realized possibility (when the wave function “collapses”), matter “chooses.” Understanding matter as minded explains quantum physicists’ finding that matter takes a particular determinate form only when measured and that the specific form it takes is strictly unpredictable; it confronts the idea of a deterministic world with one in which even “inanimate” matter exercises freedom.

Quantum IR

Like IR work that embraces complexity theory, the various works that fall under quantum IR take up the quantum challenge in slightly different ways: different works take up different understandings of the implications of quantum physics, and they make different claims regarding the ontological status of their favored interpretation.

Most quantum IR scholars who have been attracted to the Copenhagen Interpretation hedge on the question of the nature of reality (Murphy, 2020, pp. 38–39), refusing to take a position even when drawing from work that does make strong ontological claims (Zanotti, 2018, p. 1). Instead, they prefer to focus on the analytic utility and political benefits that can come of thinking within or from a quantum paradigm. Murphy (2020) maintains that concepts from quantum physics (and, implicitly, the understandings of such concepts offered to us by the Copenhagen Interpretation) can be useful to IR scholars, enabling them new purchase on difficult questions or helping them to raise questions or problems impossible to think or see via the Newtonian paradigm. Demonstrating this, Murphy suggests that seeing the border in terms of wave/particle duality can be useful for critical border studies, incorporating the observer effect can enhance critical ethnography, and entanglement can be used to deepen assemblage thinking.

James Der Derian—one of the major figures pushing for a quantum turn via his Project Q (Sydney, 2019)— leverages the thoughts of Bohr, Heisenberg, and Einstein on words, images, numbers, and predictions to demonstrate the potential utility of a quantum approach to war (Der Derian, 2013). While his specific ontological commitments are not made explicit, Der Derian suggests that quantum technologies (quantum computing, quantum sensors, quantum cryptography, etc.) are transforming the world in a way that necessitates a quantum IR approach (Der Derian, 2019; Der Derian & Wendt, 2020, p. 402, 2022; though see Smith, 2020, for a dissenting view). Yet other thinkers draw upon the Copenhagen Interpretation because they see particular phenomena—money (Orrell, 2020) or markets (Murphy, 2021) for instance, as having quantum properties.

Laura Zanotti (2018) asks how international relations scholarship and political practice needs to be rethought if we adopt Barad’s agential realism as our ontological foundation. Her argument is that an “entangled imaginary” offers a particular ethical orientation, encouraging us to affirm the ontological and ethical primacy of practices rather than universal theories and abstract rules, and to adopt a stance of caution, modesty, and responsibility (though see Hamilton (2017) for a critical take on the turn to an entanglement-based ethics generally and Prügl (2020) for a feminist critique of Zanotti’s ethical theory specifically). While Zanotti bypasses the question of the ontological truth of Barad’s agential realism, she notes that “If we start from a relational ontology, the question of whether quantum is ‘real’ or ‘metaphorical’ may be a mute one. The real and the discursive are entangled, provisional, and causally relevant” (Zanotti, 2020, p. 191); if seeing and treating the world as quantum changes the world, then can we say the world has a “nature”? Recent interlocutors have argued that Zanotti’s ideas have particular value in relation to issues of war, temporality, and positionality (McIntosh, 2020) and in conversation with affect theory (Yıldız-Alanbay, 2020).

Many (Allan, 2018; Kessler, 2018; Michel, 2018) see neutrality on the question of ontological truth and an approach that stresses the epistemological value of thinking “as if x {insert world politics, the global economy, etc.} were quantum” as valuable, especially physicists and philosophers of physics themselves are deeply divided on the ontological and epistemological implications of quantum mechanics. Alexander Wendt, however, makes a strong realist claim for the quantum ontology he espouses because it is “too elegant not to be true” (2015, p. 35), uniting findings across disciplines and helping to resolve major issues within social science. Wendt endorses a pan-psychist ontology, and maintains that like the minded matter of which it is composed, human minds and society are quantum. Human brains are entangled by the virtue of language, social structures are superpositions of shared mental states, and the state is a holographic organism (defined as one in which the whole [the collectively conscious state] is enfolded into its parts [individuals]). This quantum ontology, Wendt argues, provides a re-conceptualization of the physical basis for attributing conscious, intentional states to our fellow human beings, opens up new avenues for thinking about agency, and requires us to see “social facts” anew.

Wendt’s quantum ontology has been taken up by a number of scholars in IR. Chengxin Pan (2020) goes back to the work of Bohr to flesh out Wendt’s vision of this state, and argues that we should think of international relations more generally as quantum holographic. Other scholars have used the ontology Wendt champions to understand “the emerging reality of the new ‘Silk Roads’” (Fierke & Antonio-Alfonso, 2018) and traumatic political memory (Fierke & Mackay, 2020), and maintained it provides a tool for intervening in settler-state onto-epistemology and thus advancing decolonization (Bowman, 2021).

While work in quantum physics and the philosophy of physics is multinodal, quantum-informed IR mirrors complexity-informed IR in that it is largely bifurcated, with most work drawing from either the quantum ontological vision offered by Wendt or that offered by Barad. Books employing each ontology have garnered attention in the form of dedicated symposia (International Theory 14:1 and Millennium 49:1); both have inspired curiosity and criticism. But Wendt’s Quantum Mind has been met with particularly vigorous skepticism (Erskine et al., 2022). Given the prominence of Wendt himself in the field of IR (Teaching, Research, and International Policy, 2017) and thus the relative visibility of his understanding of quantum IR, these critical reactions could have a dampening effect on the relatively young and fragile quantum IR project.

Bringing Quantum and Complexity Together?

As noted in the introduction, some have emphasized the tension between complexity and quantum theories, and the work that draws from each. This tension does exist. Chaos theory portrays even apparently chaotic systems as deterministic; the quantum world has an ineliminable randomness at its core. Morin talks of restricted complexity as a hybrid “formed between the principles of traditional science and the advances towards its hereafter” (Morin, 2007, p. 10), Wendt says that “complexity theory ‘ultimately embod[ies the] classical ontology’” (2015, p. 147) that is upended by quantum mechanics.

But while there are strands of complexity theory that are incompatible with strands of quantum theory, this does not mean that complexity theory as a whole is incompatible with quantum theory as a whole. In fact, there are resonances across particular areas in these two different fields, and these deserve attention and exploration. To date, “those who have championed complexity theory have had only a ‘fleeting’ engagement with quantum theory” (Wendt, 2015, p. 147) and vice versa. Quantum and complexity advocates in IR—despite their shared dis-ease with Newtonianism—operate in relative silos, unaware of the overlaps between at least some work in each field and the potential for joining forces in the effort to move IR away from its Newtonian foundations. This final section encourages this conversation by noting the historical and conceptual connections between these bodies of thought. It ends with one example of IR work that draws from both complexity and quantum theory and thus could serve as a useful touchstone for those who want to unite camps dedicated to the project of a post-Newtonian IR.

Historical Connections

Even a cursory examination of the intellectual histories of quantum and complexity shows connections between these bodies of work. As Orsini notes, “the recognition and articulation of complexity are rooted in early twentieth century quantum physics” (Orsini et al., 2020, p. 1012). Morin (2007, p. 21), in telling the history of complexity theory, maintains that de facto complexity (in the general sense) was introduced by two revolutions: one being the creation of interdisciplinary fields like ecology in the mid-20th century, the other being the late 19th-century revolution in the understanding of the physics at the most micro and most macro scales that introduce indeterminism and methods to deal with it. Given these accounts of the origins of complexity, it is unsurprising that major complexity theorists like Murray Gell-Mann—one of the co-founders of the Santa Fe Institute, was also a Nobel Laureate in Physics for his contributions and discoveries concerning the classification of elementary particles and their interactions.15 His popular book, The Quark and the Jaguar: Adventures in the Simple and the Complex (1994), brings discussion of quantum physics and complex systems together.

Similarities Between Complexity and Quantum

These accounts of the history of complexity and the presence of the same person(s?) at the forefront of both fields suggest that there is a basis for the conversation between complexity and quantum IR scholars, and give reason to believe there is at least some compatibility. The below analysis identifies important points of overlap between general complexity work and Barad’s agential realism:

First, at least some thinkers working in a general complexity vein insist that complex systems are unpredictable in principle—but even they argue that history nonetheless matters in that it bounds the range of the possible at a given moment. This is consonant with quantum mechanics. Quantum mechanics can tell you the likelihood of different outcomes being observed upon measurement; while some outcomes are much more likely than others, no one can say which exact one will be observed.

Second, just as agential realism maintains that discrete entities do not preexist measurement but instead are produced as distinct through the act, a general complexity view emphasizes that boundaries are imposed. One part can “belong” to multiple systems, the system isn’t sharply separated from the environment. Thus, Morin writes:

it is thus necessary to recognize the inseparability of the separable, at the historical and social levels, as it has been recognized at the microphysical level . . . Even more, one arrives to the idea that everything that is separated is at the same time inseparable.

(Morin, 2007, p. 20)

Third, because agential realism and general complexity (Bousquet & Curtis, 2011, p. 48) recognize the malleability of matter and meaning, the focus of both is on process, and knowledge must be both historicized and contextualized.

Fourth, beyond sharing the thought that the physical, biochemical, psychic, and social have a common ontology, agential realism and some working in a general complexity vein insist on a posthuman science and ethics. We must see and respect the efficacy of nonhuman actants.

Fifth, Barad and figures associated with general complexity (Cudworth & Hobden, 2013; Kavalski, 2020; Malaina, 2015) insist that we are part of the world we study, and that we cannot but have effects, which become causes, when we do study it. There is no outside or neutral position, and we are responsible for the “cuts” that we make in reality via our analysis and its effects. We never merely reflect; we are always implicated in (re-)creation.

Do certain strands of complexity and quantum offer a similar ontology? Point to a similar methodology? Imply a similar ethics? These questions should be further explored—and more connections between strands pursued—in an effort to strengthen the post-Newtonian challenge.

A Promising Start

Some are already doing this work (Albert & Bathon, 2020; Cudworth et al., 2017; Katzenstein & Seybert, 2018). In particular, we want to highlight Milja Kurki’s (2020) International Relations in a Relational Universe, an effort to develop a relationalist vision for IR (Donnelly, 2019; Kavalski, 2020) that mines both quantum and complexity theory. Though Kurki herself doesn’t explicitly promote the work as an integration of ideas from quantum and complexity theory, providing a concrete example of such an integration may be one of the book’s greatest contributions.

In order to bring complexity and quantum together, Kurki employs the frame of “cosmology.” Cosmology refers to the always in-process image of the universe formed via interaction between human and nonhuman and held by both (Kurki, 2020, p. 15). Cosmology is a productive frame for bringing quantum and complexity—what Gell-Mann signifies with the quark and the jaguar, but we may also signify with the atom and the universe—together because it “addresses both observation and theorization of the very large-scale structure of the universe and the theorization and observation of the very small-scale structure of the universe” (Kurki, 2020, p. 42) and requires we analyze the “whole of the cosmos together, not simply parts of it” (Kurki, 2020, p. 60). For Kurki, “putting [complexity-grounded and quantum-grounded analyses] in the conversational frame of relational cosmology” enables us to better “defend and develop” them (Kurki, 2020, p. 13).

Via a “relational cosmology,” Kurki provokes us to “think against usual ‘relationism’ in IR which privileges the study of things against backgrounds, reduces relations to interactions, and prioritizes humans and their interactions” (Kurki, 2020, p. 17). She calls on us to see that which we have taken to be entities as processes that intra-act to create complexity and organization (Kurki, 2020, p. 73), and the universe as a whole as “a network of relations evolving in time” (Kurki, 2020, p. 63). Concretely, this requires an IR that is posthumanist (she suggests “planetary” as a potentially fruitful terminological alternative to “international” or “global”), that is attentive to its situatedness and careful of its effects, that is aware that change changes, and that thinks about how to rethink (and revise in practice) valued forms like democracy in light of this new perspective.

Kurki thus uses what Mathias Albert and Felix Maximilian Bathon (2020) note are complementary aspects of quantum and complexity theory to develop a foundational vision intended to re-orient IR generally.16 As one concrete example of an attempt to synthesize quantum and complexity, then, this text has the potential to jump-start a conversation between camps that have long been separately criticizing Newtonian IR. This conversation should ask whether this is a successful synthesis, whether it needs revision, whether it can be further developed, and what it means for the study of different political phenomena. But if this conversation enables critics to at the very least agree that certain aspects of complexity and quantum strands are compatible, then they may be able to go beyond offering separate anti-Newtonian challenges to putting forward a common positive alternative.

Toward a Post-Newtonian IR

Those who have criticized Newtonian physics maintain that it can be useful even if it’s not “true” in the sense in which those working within it understand truth.17 But we also know that at least sometimes the Newtonian framework is not useful—it gives us an inaccurate picture of the world, it prevents us from seeing important aspects of the world, it pre-empts certain questions about what and how we can know and what our responsibilities are, it sends us down the wrong path. Hence Fishel et al. write, “trying to write from within [Newtonian] IR, we find ourselves prisoners in our own vocations. We are speechless, or even worse, cannot find words to represent the world and those within it” (Fishel et al., 2018). The proliferation of post-Newtonian challenges to scientific IR call for a reckoning: Newtonian assumptions simply cannot be the unthought default any more.

Beyond criticism, however, enabling this reckoning also requires discussions about and across various post-Newtonian foundations. Two bodies of work that have provided footholds for those who have sought to push IR in a post-Newtonian direction were outlined in this article. The above shows some strands within complexity and quantum theory are relatively congenial, and this suggests there should be a conversation between those who have pursued visions of a quantum and complex IR. Just as it is important to ask where and in what way these visions converge, however, advocates of a post-Newtonian IR should ask where the tensions between even the most congenial versions of quantum and complexity are and whether aspects of these “foundations” are irreconcilable. To what extent and in what ways, for instance, is Cudworth and Hobden’s Posthuman International Relations compatible with Zanotti’s Ontological Entanglements? How do Murphy’s ideas about the way quantum work might be used in IR compare with the methodological conclusions of Byrne? Are there overlaps between Byrne and Callaghan’s complex social science and Wendt’s quantum social science? We should also ask whether and how lack of cohesion of post-Newtonian visions matters, and what to do in light of our answers.

Quantum and complexity are but two entryways to envisioning an IR that isn’t deeply rooted in a paradigm now seen as less accurate than others, but they are paths that are likely to be most inviting and most comfortable to those who have been trained to pursue knowledge through a Western version of science. It’s important, however, to end by encouraging those who arrive at a post-Newtonian perspective through these doors to carefully and humbly engage with ways of doing IR grounded in other cosmologies that never centered humans, that always foregrounded relationality, and that continually rejected mastery. We share the hope that these conversations will lead to a more pluriversal IR (Acharya, 2014; Kurki, 2020, p. 174).



  • 1. A 2017 study of the extent to which positivism (a descendant of Newton’s scientific vision) is practiced in US IR, authors found that “the bulk of IR studies and teaching practices in the US” embeds positivist epistemological and methodological commitments (Eun, 2017). While “58% of all articles published in the major journals were ‘positivist’ in 1980,” by 2006, “that number had climbed to almost 90%” (Eun, 2017, p. 595). This commitment to positivism in the United States is significant for IR at large, given the “enduring and powerful influence of the American scholarly community on . . . the field” (Eun, 2017, p. 595). Alexander Wendt also speaks of the prevalence of Newtonianism in IR in the second decade of the 21st century, saying,

    we currently give [Newtonian methods training] to almost all graduate students in the human sciences. What this does is not just teach them to use specialized statistical tools, important although that is. It also hard wires their brains—our brains—to “see” a mostly invisible social world as if it were full of classical objects and “mechanisms.” The bias in our training is clearest on the positivist side, [but] we do see a clear footprint [in interpretivists’ work as well]. (2022, pp. 205–206)

  • 2. Beyond faulty representations and incorrect conclusions, Wendt raises the important question of whether we are in fact manifesting a Newtonian-seeming world because we (and this “we” goes beyond researchers) learn and operate with Newtonian assumptions (2022, p. 207; see also Barad, 2007; Smith, 2004; Zanotti, 2018).

  • 3. The label “post-Newtonian” refers to those scholars who continue to work with and in Western scientific frameworks and traditions, despite their critical orientation toward Western science’s dominant (Newtonian) paradigm.

  • 4. This structuring device distinguishes our overview from recent overviews of complexity-based IR work that are organized by topic (Janzwood & Piereder, 2020; Kavalski, 2015b).

  • 5. Manson (2001) helpfully distinguishes between three types of complexity research: algorithmic, deterministic, and aggregate. We will not discuss “algorithmic” complexity research, for as Manson says, it makes relatively “ancillary” (Manson, 2001, p. 406) contributions to complexity theory overall.

  • 6. Adaptation of both the system as a whole as well as its parts, which can themselves be understood as whole systems.

  • 7. In a really excellent overview of concepts in chaos and complexity theory, Rickles et al. helpfully explain the relation and distinction between chaos and complexity:

    Chaos is the generation of complicated, aperiodic, seemingly random behaviour from the iteration of a simple rule . . . Complexity is the generation of rich, collective dynamical behaviour from simple interactions between large numbers of subunits. Chaotic systems are not necessarily complex, and complex systems are not necessarily chaotic. (2007, p. 934)

    They also note that

    Complex systems are built up from very large numbers of mutually interacting subunits (that are often composites them-selves) whose repeated interactions result in rich, collective behaviour that feeds back into the behaviour of the individual parts. Chaotic systems can have very few interacting subunits.

  • 8. To add further complication, Prigogine distinguishes between catastrophe theory, which he says is deterministic, and the “Sciences of Chaos,” which he claims to be nondeterministic (Guerra, 1996). Others portray chaos theory as deterministic. Classification issues aside, the important point is that some complexity theorists see and treat complex systems as deterministic, and others suggest that complexity is by nature nondeterministic.

  • 9. Recent work suggests that a world that is unpredictable in principle can still be a deterministic world (Sartenaer, 2015). While agreeing with this argument would change whether some think of complex systems as deterministic, it wouldn’t change the fact that these camps are still split over whether they are unpredictable in practice or in principle—and that each view has different epistemological and methodological implications.

  • 10. Many critics of restricted complexity stand with theoretical biologist Robert Rosen who took the view that “no amount of studying simple systems can help us understand complex ones” (Lane, 2018, p. 4)—and they would likely agree with Rosen that those systems that are simulable are, by definition, not complex.

  • 11. Indeed, even the math itself is not uncontested, as David Bohm developed a formalism to describe the quantum world which is mathematically equivalent (i.e., produces the same outcomes) to the formalism that is employed by most (the “Schrödinger equation”).

  • 12. While a recent popular book on quantum physics by Becker (2018) highlights counterviews to and itself strongly criticizes the Copenhagen Interpretation, it’s worth noting that a review in the American Journal of Physics suggests that book deeply misrepresents the Copenhagen Interpretation (Fuchs, 2019).

  • 13. Another major figure associated with Copenhagen is Bohr’s student, Warner Heisenberg; Heisenberg’s uncertainty principle—which asserts that measurement introduces a disturbance that prevents us from knowing properties definitively—is one of the most well-known ideas to come out of the quantum revolution, and one (very prominent) way of explaining why the probability distribution the Schrödinger equation gives us is all we can know. We don’t elaborate on Heisenberg here, however, because Heisenberg ultimately acceded to Bohr’s understanding of the problem (Barad, 2007, p. 19)—that the issue is not one of disturbance but rather the “possibilities of definition” of the variables in question (Barad, 2007, p. 305).

  • 14. The degree to which Barad faithfully represents Bohr’s views has been questioned by some (Faye & Jaksland, 2021).

  • 15. The Santa Fe Institute is a nonprofit theoretical research institute located in Santa Fe, New Mexico that is dedicated to the study of complex systems and to promoting complexity theory as an interdisciplinary field.

  • 16. Albert and Bathon offer a reading of the complementarities between the social theory of Niklas Luhmann and quantum social science. While this reading helps us start to see the points of overlap between complexity and quantum work, it’s worth noting that Luhmann’s theory is but one social theoretical “take” on complexity theory, and one that strongly privileges humans and human communication. Albert and Bathon say that quantum theory brings a focus on physicality and the nonhuman lacking in (complex) systems theory; but nonhumans and the physical are part of the complex systems-inspired political theory of Erika Cudworth and Stephen Hobden (2013). They note that a look at the relationship between complexity outside of this instance of systems theory (i.e., Luhmann’s) and quantum theory is beyond the scope of their article; this was the animating goal for this article.

  • 17. As Wendt puts it,

    just as quantum physics did not invalidate classical physics for all purposes, so quantum social science would not wholly invalidate classical either . . . one can imagine that the more predictable social environments are, the more useful classical approximations will be. (2022, p. 200)