Complexity in international society: theorising fragmentation and linkages in primary and secondary institutions

This article seeks to contribute to theorising the institutional structure of international society by exploring synergies between complex systems thinking and the English School theory of International Relations (IR). Suggesting that the English School already embraces key conceptual insights from complexity theory, most notably relational and adaptive systems thinking, it reconfigures international society as a complex social system. To further advance the English School’s research programme on international institutions, the article introduces the notion of “law-governed emergence” and distils two effects it has on global institutional ordering practices: fragmentation and clustering. These moves help to establish complexity as a fundamental structural condition of institutional ordering at the global level, and to provide a basis for taking steps toward better understanding the nature and significance of institutional interconnections in a globalised international society.


Introduction
The uptake of complexity theory in the discipline of International Relations (IR) has been steady but slow. First attempts to incorporate insights from complexity science into international systems thinking were made in the 1990s but failed to generate a sustained and systematic research programme. In an effort to encourage a more systematic engagement, a number of recent contributions have sought to reconfigure debates and conceptual resources to build a more solid foundation for dialogue between complexity theory and IR theory (Bousquet & Curtis, 2011;Kavalski, 2007). Pointing to the pervasive and ever-growing randomness and uncertainty of international life, these scholars see an opportunity in complexity approaches to enhance current theoretical frameworks for the study of global politics.
Taking up this challenge, this article explores how complexity theory can help to advance the English School's approach to IR theorising and, in particular, its account of international society's institutional structure. Once on the margins of the field, English School theory has seen a revival since the turn of the millennia, and it now maintains a thriving research programme centred around societal order and shared norms, rules and institutions at the global level. Drawing on sociology, history, and political theory, its methodological approach to theorising international relations offers a valuable resource for studying the normative dynamics and institutional structure of world politics that is different from US-led mainstream IR theory. 1 The claim of this article is two-fold. Firstly, and more generally, I suggest that English School theory is inherently open to complexity thinking. This openness springs from its methodological orientation. Proceeding from the basic assumption that international society is a dynamic social construct, English School scholars have privileged constitutive theorising over linear causality, historical contingency over presentism, and relational over essentialist ontology. In doing so, English School scholarship embraces and applies, though somewhat implicitly, a number of conceptual insights from complexity theory that are deemed valuable for advancing the study of international relations (Kavalski 2007;Bousquet and Curtis 2011): open and adaptive systems thinking, historical process tracing, self-organisation, and multilevel interactions.
Secondly, and more specifically, I argue that incorporating insights from complexity theory can help to further develop the English School's account of international institutions. While some progress has been made in understanding the reciprocal relationship between different types and levels of institutional structures (i.e. primary and secondary institutions), current English School scholarship has not fully engaged with concepts, such as fragmentation and linkages, that have been key to explaining complex governance arrangements in different issues areas. Drawing more explicitly on these concepts, I suggest, can help English School scholars to improve their understanding of the dynamics and interconnections within and among international society's different institutional ordering practices.
The article is divided into three sections. The first section offers a necessarily brief overview of complexity theory in IR, introducing definitions and setting out key debates. The second section focuses on two conceptual insights from complexity theory -relational and adaptative systems thinking -and shows how they have featured into the English School's approach to theorising the composition and evolution of the international system. Here, I demonstrate how the School's approach to the study of international relations has been built around a socio-historical understanding that emphasises changes in both the basic units of the international system and the deep-seated normative structures that drive shifts in system structures over time. Recognising that current English School scholarship does not exhaust the analytical value and potential of complexity thinking, the third section considers how current debates about the institutional structure of international society can be further advanced. After setting out the English School's conceptual distinction between primary and secondary institutions, I introduce the notion of "law-governed emergence" and distil two effects it has on global institutional ordering practices: fragmentation and clustering. The article concludes with a brief summary, pointing to some of the normative implications of complexity thinking for English School theorising.

Complexity theory in International Relations: a brief overview
Complexity theory has become a broad field of study, and there exists no clear and widely accepted definition. Rather than a unified theory that can be holistically applied (Walby 2007, p. 35), complexity theory involves a number of concepts and approaches that have been developed in response to a particular problem: how to make sense of systems (both physical and social) that defy the logic of general laws, predictable behaviours, linear relationships, and the proportionality between cause and effect. Accordingly, it has become common practice to define complexity theory in terms of the subject it seeks to study: complex systems.
Following a recent definition, a complex system is an "open system (…) that includes multiple elements (units) of various types intricately interconnected with one another and operating at various levels" (Orsini et al 2019: 3). These systems, so the argument goes, need to be approached in distinct ways, because they display certain unique characteristics -that is, they evolve "at the edge of chaos" (Lewin 1992, Waldrop 1992Holland 1995), where unexpected patters, events, and outcomes are the product of self-organisation and emergent properties (Orsini et al 2019: 3-4), rather than external shocks or large-scale structural transformations (Kauffmann 1993). The ontological features of these systems, then, have epistemological consequences. Analytically, complex systems are more than complicated, for they cannot be broken down into their individual parts (Morin 1990). Because the systemic whole is different than the sum of its parts (Jervis 1997), the dominant scientific paradigm built around notions of causality and linear relationships is of limited value. In the social sciences, complexity theory has thus been convincingly associated with critical (or philosophical) realism and sociological naturalism (Reed and Harvey 1992), though different versions of complexity thinking continue to enlist a variety of epistemological approaches.
Building on these insights, I define complexity theory as a cognitive toolkit and associated research strategies explicitly designed to make sense of systems, both physical and social, in which structures, properties, processes, and outcomes arise from interactions among the elements of the system. This definition is consciously broad, aiming to capture the diversity of disciplinary and methodological approaches associated with complex system thinking. It also decouples complexity theory from a specific list of basic system features such as self-organisation and emergence, recognising that complexity theory can and should be applied to a broad range of systems marked by various characteristics and properties (and combinations thereof).
The discipline of IR has had a patchy relationship with complexity theory, marked by continues punctual interventions rather than systematic engagement (e.g. Albert, Cederman, & Wendt, 2010;Hoffmann & Riley, 2002). This is surprising, given that social, economic, and technological developments associated with globalisation have turned complexity into "a structural condition of world politics" that "provides the ontology behind challenging current research questions" (Haas 2019: 5, in Orsini et al). While traces of complexity thinking can be found in the early international systems theories of Morton  and Oran Young (1968), it was not until the late 1990s that IR researcher started to pay explicit attention to the phenomenon of complexity (e.g. Axelrod 1997, Rosenau 1990). Most notably, Robert Jervis (1997) observed how certain system effects transformed the environment in which policy makers operate, pointing to issues and governance problems that arise from complex interconnections among social, economic, and political developments.
Today, much of the complexity agenda in IR is focused on exploring the dynamic relationships among international institutions (Haas 2019: 7, in Orsini et al). Expanding webs of cooperation in diverse issue areas, ranging from refugee protection (Betts, 2010;, to climate change (Abbott, 2012), to intellectual property rights (Helfer, 2009), have produced a multitude of institutional arrangements that partially overlap and are not hierarchically ordered. So instead of focusing on discrete institutions, as early liberal regime theorists did, IR scholars have shifted the focus to the global governance architecture, understood as 'the overarching system of public and private institutions that are valid or active in a given issue area of world politics' (Biermann et al 2009: 15). Because the international systems lack centralised authority, many institutional elements of these governance systems evolved independently, covering different geographical regions and issue areas, and display different degrees of formalisation. They also frequently overlap in the sense that many issue areas and actors are within reach of more than one institutional arrangement. For example, the global institutional framework that governs international investment now involves around 3.000 bilateral treaties, lacking an overarching multilateral institutional framework that integrates these arrangements (Johnston and Trebilcock 2013: 622).
These fragmentation dynamics have sparked rich conceptual innovations that seek to categorise and compare the nature and structure of institutional complexes (e.g. Orsini et al 2013, Biermann et al 2009. Typically discussed under the banners of "regime complexity" and "orchestration" (Haas 2019: 7, in Orsini et al 2019), IR scholars have focused on the interconnections and linkages (e.g. Young 1996) between individual institutions to understand the opportunities they create for governance innovations and sophisticated divisions of labour (e.g. Gehring and Faude 2014), as well as the negative effects of fragmentation dynamics (e.g. Zürn and Faude 2013). This work has also been very valuable in establishing the empirical relevance of complexity theorising: for example, by showing how specific institutions strategically respond to growing institutional proliferation by developing resources and re-defining organizational structures (e.g. Betts 2009) The effects and governance of climate change have been a critical driver behind the integration of complexity theory into IR. Most obviously, the governance of climate change is marked by an array of multilateral treaties, thereby displaying the classical characteristics of a fragmented global governance architecture (Biermann et al 2009: 18). Moreover, at the heart of the problem of climate governance lies the recognition that human and non-human (ecological) systems are deeply interwoven (Kavalski 2011), producing emergent effects that cannot be traced back to one single system. This makes climate change an extremely complex phenomenon that generates unexpected non-linear societal and political events (Campbell 2009) that often defy traditional modes of inquiry.
While the bulk of complexity analysis in IR has focused on the meta-level of institutional complexes, aiming to make sense of the pattern and effects of functional interconnections, a number of constructivists have zoomed in on the nature of the linkages that connect institutions. Peter Haas' (2013, Haas and Stevens 2017) work is exemplary of this approach. Proceeding from the assumption that the boundaries and nature of complex issues are socially constructed, Haas (2019: 7, in Orsini at el) argues that the processes through which connections among institutions are formed, sustained, and modified can only be made intelligible by reference to the shared normative understandings in which they are embedded. This is an important insight, as it connects complexity theory to IR approaches that emphasise the role of shared norms, rules, and principles for the organisation of international systems. It is here where the English School approach to IR theorising enters the picture.

Tracing complexity in the English School's research programme
What broadly unifies English School scholarship is the core belief that international relations are not merely about power politics, fixed preferences and conflicting national interests, but also about identities and shared norms, rules, and institutions that order international life. 2 As such, English School theory shares a number of theoretical assumptions and cognate research goals with IR constructivism (Reus-Smit, Christian, 2009, p. 58): the focus on the cultural bases of state identity; the rule-governed nature of state-systems; the different forms of organising life under anarchy; and an intersubjective reading of the international world, where socially constructed institutions such as diplomacy, international law and sovereignty constitute agents' identities and interests and 'can exist only in virtue of certain intersubjective understandings and expectations' (Wendt, 1992, p. 412).
The English School's macro-sociological approach to theorising international affairs is perhaps best reflected in its key concept: international society. According to Bull and Watson's (1984, p. 1) seminal definition, an international society exists when, "a group of states (or, more generally, a group of independent political communities) which not merely form a system, in the sense that the behaviour of each is a necessary factor in the calculation for the others, but also have established by dialogue and consent common rules and institutions for the conduct of their relations, and recognize their common interest in maintaining these arrangements." Understanding and theorising the distinct nature, emergence, and transformation of the deep-seated normative structures that constitute international society has been one of the defining features of the English School literature (Clark, 2009;Holsti, 2004). I will say more about those societal ordering practices, and how insights from complexity theory can help to further their study, at a later stage. For now, I will focus on showing how the English School approach to IR theorising displays quite a few of the traits that are central to complexity theory.

Relational and processual systems thinking
Systems thinking lies at the heart of complexity theory. At the simplest level, it presupposes that the elements under study cannot be considered independently from each other but are somehow connected through dynamic feedback processes and relationships, thereby forming a system. For classical sociological systems thinkers such as Durkheim and Parsons, those feedback processes would help to establish some kind of stability in the system. As Walby (2007, p. 456) notes, "equilibrium was the norm to which a system would return if there were small a small deviation." While complex systems theorists do not deny the existence of equilibriums and stable relationships within systems, they stress the way in which those feedback processes contribute to the evolution of a system beyond equilibrium (e.g. Arthur 1994). On this view, the components of a system are entangled in complex micro-macro relationships that produce outcomes and configurations that defy causal analysis and path-dependence models (e.g. Kauffmann 1993, Waldrop 1992. English School theory is essentially concerned with the system level, as exemplified by the concept of international society. The explicit focus on the system level sets the English School apart from other sociological approaches to the study of IR. Whereas constructivists, perhaps with the notable exceptions of Wendt (1999) and Reus-Smit (1999), have focused on the location, function and transformation of specific norms, the English School is largely concerned with "the way in which things fit together" (Hurrell, 2001, p. 489).
Understanding the international system in societal terms comes with a relational and processual approach to systemic thinking that stresses dynamic flux in both the units and boundaries of the international system. Here, the English School follows precisely the historical sociology that Bousquet and Curtis (2011, p. 49) identify as one of the perquisites for complexity theorising in IRthat is, a "processual ontology that privileges 'becoming' over 'being', dynamic flux over stable essence." Although the bulk of historical English School scholarship has been primarily concerned with the evolution of the society of states, its framework clearly rejects an essentialist ontology of social units. Barry Buzan and Richard Little (2000), for example, have developed a theoretical approach to the historical analysis of the international system that emphasises dynamics in both the interactions among the units of the systems (process) and the resources that spread throughout the system (interaction capacity). Whereas the former relates to dynamics in what units do when they interact (e.g. changes in trade, political recognition, war), the latter is concerned with dynamics in the capacities that define what units can do (e.g. changes in transportation, communication, and weapons technologies) (Buzan and Little 2000, pp. 79-84). The result is a world historical perspective on international systems that introduces the idea of turning-points, such as the transformation from agrarian empires, chiefdoms, and nomadic empires to nation states, to develop a chronological account of how the international system began and evolved. This and other work (Watson, 1992;Wight, 1977) reinforces the claim that the dynamics of global social systems, and specific configurations of units and ordering structures within them, have always been contingent and subject to change.
To get to grips with the more current systemic processes beyond the nation state associated with processes of globalisation, English School theory has begun to explore more systematically the concept of world society (Buzan, 2004;Weinert, 2017;Williams, 2005). Focused on cosmopolitan norms and institutions arising from the inter-human domain of international relations, the concept of world society has been explicitly designed to capture what Bull (1977, p. 269) called the "totality of global social interaction" that includes "all parts of the human community." Bull did not flesh out the concept in detail, and there remains a good deal to be resolved in terms of rendering the concept of world society precise. Yet, it is clear that world society encapsulates the values, institutions, relationships, and organizational processes that emerge from the interaction between non-state actors, including civil society, supranational organisations, and other transnational actors that operate beyond and below rigid, territorially bound hierarchical state authority structures. Put simply, whereas states are the main actors in international society, world society involves institutions, processes, and normative arrangements that originate from interactions among non-state actors. Here, a clear resonance can be found with ideas of decentralized networks, bottom-up processes, and forms of selforganisation frequently highlighted by complexity theory. Looking more closely to complexity theory and its terminology and concepts could provide a rich resource for English School theorists to further carve out the processes of order formation and governance within the still underexploited domain of world society.

Adaptive systems: membership dynamics and the social construction of boundaries
The processual notion of social units also carries forward into the School's understanding of the boundaries of international society. Whereas traditional systemic IR accounts (e.g. Waltz 1979) have worked under the assumption that the international system is essentially closed, consisting of a few interacting parts, English School theory has always depicted international society as an open social system with boundaries that shift over time -an approach neatly reflected in Bull and Watson's (1984) classical account of the expansion of international society. The 'expansion narrative' put forward by Bull and Watson is largely historical, telling the story of how colonialization and decolonization shaped the world according to European blueprints (Buzan 2014, p. 45). It is also a Eurocentric narrative, as Complexity, Governance &Networks -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts andTheories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 Bull (1984, p. 123) himself seems to concede at some point. Yet, read in conjunction with more recent theoretical English School work on international social structures, it offers some important conceptual insights into how open systems evolve.
According to the English School's perspective, the dynamics that shape system boundaries in international relations are essentially normative, socially constructed through the interaction of political entities. The idea is that who is inside and who is outside international society matters, which places the focus on questions of membership in international society and the criteria for obtaining it. After all, international society is a club of clear participants (i.e. sovereign states) that have exclusive access to certain rights and institutions. The society of states that began to emerge in 15 th century Europe, for example, is recognised as a distinct social system with boundaries, because it involved a number of rules, norms and institutionalised ordering practices, such as the development of a common body of international law and rules around managing the balance of power, that were specific to the relations among European states (e.g. Keene's 2002).
While the terminology of historical English School scholarship does not always fit easily with the more abstract conceptual language of complex systems thinking, it does cast light on the dynamic, socially constructed nature of system boundaries in international relations. Barry Buzan's (2004) structural work offers further insight into the processes through which international society has expanded. Building on Wendt's (1999) three cultures of anarchy, Buzan (2004, pp. 139-158) identifies three mechanisms through which social structures are internalised: coercion, calculation, and belief. His model is, of course, an ideal type. In practice, system structures are internalised through a complex mixture of those mechanisms. However, by formalising social systems thinking in international relations in terms of mechanisms of internalisation, Buzan's scheme offers a concrete toolkit for investigating two key questions: how and why social systems are shared, to what degree, and with what kind of social opposition?
The emergence of regional normative orders is another area in which membership dynamics shape the formation of system boundaries. In an attempt to get to grips with regional variation in international ordering practices, English School writers have recently introduced the notion of "regional international society" (Schouenborg, 2012;Stivachtis, 2015;Stivachtis & Webber, 2011). Driven by the rise of regionally confined orders and governance arrangements, those accounts highlight how international norms and institutions assume different meanings and forms in different regional contexts. This is an interesting insight for IR systems thinking, because of the way in which it brings the notion of sub-systems into the picture, and the ways in which they are distinct from, but interact with, the overall international system in which they are embedded. It is important to understand here that while the boundaries of those systems are somewhat wedded to geographical context, membership in regional international societies and their distinct normative orders is ultimately defined through shared membership norms (Thomas, 2017).
Before moving on, a few general remarks on how complex adaptive (CAS) thinking can improve international society theorising seem to be in order. Like complexity theory in general, CAS consists of a number of approaches and concepts rather than a unified theoretical framework; figuring out exactly which of those approaches can be coherently aligned with and applied to the evolution of international society ought to be key for developing the English School as complex IR theory. The most obvious entry point here seems to be the notion of co-evolution. Populated by biologist Stuart Kauffmann (1993), the idea of co-evolution is that as one system evolves, it necessarily changes the structure of the other system with which it interacts. As he (1993, p. 208) explains with regards to the interaction between species and environments: "Fitness landscapes change because the environment changes. And the fitness landscape of one species changes because the other species that form its niche themselves adapt on their own fitness landscapes. Bat and frog, predator and prey, coevolve. Each adaptive move by the bats deforms the landscape of the frogs." Complexity, Governance & Networks -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts and Theories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 Of course, these principles may only apply metaphorically to English School theory -after all, international society is a social construct and not a biological system. Yet, as noted above, international society has evolved through processes quite familiar to co-evolutionary analysis, with normative developments within non-Western regional systems changing and evolving based on the interaction with the European society of states and with the environment in which they are embedded.
While the idea of co-evolution is, in principle, compatible with and holds significant analytical potential for both historical and more contemporary English School scholarship, there are some limits to the incorporation of CAS into its research programme. For example, whereas some CAS scholarship starts from the assumptions that social order is not always possible, nor is it necessarily desirable (Reed and Harvey 1994, p. 390), English School theorists' principal concern from the outset has been to show that order under conditions of international anarchy is possible. This is not to say that the differences cannot be overcome -in fact, it would be interesting to see how the dissipative CAS paradigm and its emphasis on periodic chaos and radical transformation can be reconciled with the School's account of order -but there are methodological issues that need addressing.
The above overview of systems thinking in English School theory is necessarily crude and simplified, but it hopefully shows the affinities between its approach and complexity theory. The next section seeks to harvest some of those synergies by looking at how claims about fragmentation and non-linear processes of order making can be utilised to further advance the English School's current research programme on international institutions.

Advancing institutional theorising in the English School: from linear relationships to complexity and fragmentation
During the last fifteen years or so there has been a conscious move within the English School towards an emphasis on institutions as offering the most fruitful conceptual lens through which the character of order in the international society can be understood. Significant progress in identifying and organising the different types of institutions that structure international social life has been made, but the School is still a long way from a fully developed institutional theory of international order. Looking to insights from complexity thinking could be one way of driving this project further. In what follows, I will briefly introduce the main conceptual distinctions and debates relating to institutional theorising in the English School and, subsequently, sketch out elements of a complexity inspired research agenda that focuses on patterns of institutional fragmentation and interconnections.

Taxonomies and debates
Building on Hedley Bull's (1977) idea that order in international society is maintained by a number of fundamental institutions, generations of English School writers have sought to elaborate and specify the nature, identity and function of the underlying institutional elements of international social systems. Though this has generated quite an extensive, and increasingly specialised, body of literature, it seems safe to say that Barry Buzan's 2004 book From International to World Society? has become the main touchstone for institutional debates within the English School.
Buzan carefully discusses the different, though frequently overlapping understandings identified by IR theorists to distil from them two different types of international institutions. The first, which he labels "primary institutions" 3 , are 'relatively fundamental and durable practices, that are rather evolved more than designed (…) and are constitutive of actors and their patterns of legitimate activity in relation to each other ' (2004, p. 167). These are the institutions referred to in English School theory. As historically evolved normative ordering structures, they arise from interaction among actors and we know them 'by their shared and principled understandings of desirable and acceptable forms of social behaviour' (Kratochwil & Ruggie, 1986, p. 764). There exists no definitive list of primary institutions. Bull (1977) listed five: international law, the balance of power, great power management, war, and diplomacy. Other accounts have introduced sovereignty (Jackson, 2003;Wight, 1977), 3 The terms 'primary institutions' and 'fundamental institutions' are frequently used interchangeably in the literature. -Vol. 6, No 1 (2020) (Holsti 2004), and more recently, environmental stewardship (Falkner & Buzan, 2019) as potential candidates.

Complexity, Governance & Networks
Primary institutions, Buzan goes on to argue, can be distinguished from the kind of (secondary) institutions regime theorists typically refer to -that is, "an organisation or establishment founded for a specific purpose" such as the United Nations (UN), the World Trade Organization (WTO), international courts, or regional international organisations such as the European Union (EU) (Buzan 2004, p. 164). The distinction between the two types of institutions hinges primarily on the function they perform: the deeper layer of primary institutions he identifies is primarily associated with constitutive tasks such as establishing actors' roles and identities, while the more immediate, secondary level institutions are sites of regulatory practices and procedure. Moreover, whereas secondary institutions are associated with formalised governance arrangements, primary institutions are associated with more informal social practices.
The distinction between primary and secondary institutions has generated quite an extensive, and increasingly specialised, stream of research (Friedner Parrat, 2017;Schouenborg, 2011;Spandler, 2015). Discussions have primarily revolved around how primary institutions can be identified and what functions they perform. More recently, however, English School scholars have begun to question the relationship between the different types of institutions (Navari & Knudsen, 2018;Spandler, 2015). The main issue at stake here has been change in international society, and in particular the question of the relationship between primary and secondary institutions in this process. Traditionally, references to the concept of primary/secondary institutions have shared a top-down vision of change. That is, they tend to work on the assumption that primary institutions represent some more or less cohesive sets of norms, values and principles that manifest themselves in a number of corresponding formal rules and regimes. Although Buzan's original account seems to suggest that there is no one-way causal relationship between primary and secondary institutions, secondary institutions are essentially presented as 'rule-takers' from primary institutions, with a role that is focused almost exclusively on operationalising the principles and associated normative perspective of primary institutions. This in line with earlier constructivist scholarship, which posited a hierarchical, linear relationship in which constitutional structures defining criteria for membership and legitimate state action in international society constitute primary institutions, which in turn constitute the more issue specific secondary institutions (Reus-Smit, 1997).
The idea of embedding issue-specific regimes in overarching institutional arrangements that constitute international society's deeper-seated structures is not new. It has been identified by liberal regime scholars as one type of mechanisms through which institutions are linked (e.g. Young 1996: 2-3). That said, conceptual detail about these deep institutional structures and how exactly they relate to regimes is typically lacking. Using the English School's account of primary institutions can help to significantly improve the understanding of that mechanism, in particular in the context of climate governance. Above all, it could help to ground the "fragmented global [climate] governance architecture" (Biermann et al 2009) in an underlying account of international society's shared norms and values. Buzan and Falkner (2019) have made some important progress here by conceptualising environmental stewardship as a primary institution. This move enables them to tie together functionally fragmented and geographically dispersed institutional arrangements, by relating them to a "distinctive set global values" that international society as a whole holds about global environmentalism (Buzan and Falkner 2019: 132). Here, the English School offers real added-value to global environmental politics theory.

Introducing complexity: law-governed emergence
Coming at the problem of change in international society from the bottom-up, rather than topdown, a new wave of English School scholarship has proposed a reticular relationship between primary and secondary institutions (Navari & Knudsen, 2018;Spandler, 2015). The idea here is that primary institutions are not necessarily analytically prior to secondary institutions, and that the policies and operations of international organisations and regimes have reciprocal implications for the evolution of Complexity, Governance & Networks -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts and Theories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 international society's deeper-seated institutional ordering practices (see Figure 1). Building on the theoretical claim that actors are entangled in processes of constitution and regulation that always occur in parallel, this research highlights how the politics of international organisations such as the International Criminal Court or the UN Security Council frequently affect practices surrounding the balance of power and sovereignty, respectively. This argument links to complex systems thinking because it recognises cyclical paths, feedback loops and non-linearity in the relationship between different types of institutions.

Figure 1 the reciprocal relationship between international society's three institutional structures
Drawing more explicitly on complexity thinking could push this research agenda even further. In particular, it offers a way to consider how different secondary (or primary) institutions interact with each other, and how those interactions may produce effects that cannot be attributed to any specific institution. This agenda and opportunity springs from one of the core insights of complexity research: the idea that a system is not simply the sum of its parts, but is produced, altered and transformed by the interaction of its constituent parts. The conceptual challenge for English School theorists, then, is to make sense of an institutional structure whose nature, pattern and transformation cannot be explained in terms constitutional meta principles.
The place to start, I suggest, is with the notion of emergence. "Emergence" sits at the heart of the complexity research programme and there is a vast body of literature dedicated to spelling out both its conceptual properties and its application in various disciplines. It is beyond the scope of this article to offer an exhaustive review of this literature here; instead, I will briefly focus on what I believe is the most useful approach for English School theorists: "law-driven emergence." At the most basic level, the term "emergence" denotes "the arising of novel and coherent structures, patterns and properties during the process of self-organization in complex systems" (Goldstein 1999, p. 49). Crucially, for many complexity theorists, the process of "arising" is, at least in theory, not completely random, but unfolds according to a set of fundamental "laws" that set the boundary conditions within which new structures, patterns, and properties can arise. Holland (1998, p. 2), for example, uses the analogy of a chess game to show how "a small set of rules or laws can generate surprising complexity", suggesting that complexity in biological organisms is also governed by a small set of basic rules. In the same vein, Kauffmann (2000) has identified a salient organising force in the cosmos, which he calls "the fourth law of thermodynamics." What unifies these understandings of emergence, as Corning (2002, p. 25) nicely summarises, it the belief that "some underlying inherent force, agency, tendency, or 'law' (…) is said to determine the course of evolutionary processes."  -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts and Theories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 This perspective on emergence fits well with the English School's institutional account because of the way in which it allows for conceiving of institutional structures in terms of complex social constructs that are, at least to some extent, the result of unique, self-contained interactions among their components, while preserving some of the hierarchy and order assumptions that have been so central to their cognitive concerns. In this sense, the notion of "law-drive emergency" offers a via media between constitutive hierarchy and emergent institutional complexity. On this view, and staying true to the critical realist claim of constitutive effects, the rules and principles associated with higher order institutional levels constitute the background conditions in which lower order institutional levels emerge and evolve, while recognising that the actual process of emergence and evolution is a result of complex and often unpredictable interactions among actors and institutions. Some complexity theorists may rightly note that this approach runs the risk of treating emergence as an epiphenomenon. But it is, I believe, a necessary price to pay for incorporating complexity into the English School's theoretical structure.
If we follow the idea of "law-governed emergence," then the distinct character of international society, and the institutional processes and mechanisms by which it evolves, cannot be explained exclusively by resorting to a single source, principle or, in our case, institution. Instead, the dynamism of self-reproducing structures calls for putting the spotlight on the interplay between institutions and the normative consequences and social practices that follow from it. Put simply, if we take the claim that social system structures reproduce themselves from within themselves (autopesis) seriously (Teubner, 1992), then exploring dynamics and interconnections within and among institutions is key for theorising normative ordering dynamics within international society. In what follows, I will focus on two specific institutional consequences of emergence: fragmentation and clustering.

Fragmentation in primary institutions
As intuited earlier, the aspect of complexity that has been most relevant to the study of international institutions is the tendency towards the fragmentation of secondary institutions. This tendency includes the segmentation of spheres of regulative activities, each with its own role structure, norms, and obligations (e.g. Alter & Meunier, 2009). There is no reason to assume that primary institutions are not subject to similar fragmentation dynamics. Hints about how this fragmentation occurs at the level of primary institutions can be found in the regionalisation debate international society alluded to earlier. Looking at the institution of sovereignty, for example, Costa-Buranelli (2015, pp. 499-500) shows that although it exists at the global level, "the increasing regionalization of world politics and the consequent multiplication of interpretations of global institutions" have weakened the shared normative understanding underpinning it. This means that sovereignty is not necessarily a globally integrated primary institution that mandates a universally recognised course of action. Instead, sovereignty is subject to constant reframing and different interpretations, which often results in diverging sovereignty practices that are distinct to certain actors (or groups thereof).
Exploring fragmentation dynamics can be significant, because they are likely to produce much more fine-grained, nuanced understandings of the nature and internal structure of the many primary institutions. The easiest way to explain what I mean by this it to look briefly at the structural development of one of international society's key institutions, international law, where efforts at normative integration via notions of jus cogens and erga omnes co-occur with an increasing degree of normative fragmentation and competition.
Legal commentators have understood for decades that the modern international law is marked by uneven normative development, a process that not only involves the increasing diversification of issue areas, but also the admission of new constitutive members and participants. The International Law Commission paid tribute to this process by initiating a study group on the theme of 'fragmentation of international law'. Marti Koskenniemi (2006, p. 68), who finalised the landmark report, summarises the increasing disintegration of international law as follows: "What once appeared to be governed by "general international law" has become the field of operation for such specialist systems as "trade law", "human rights law", Complexity, Governance & Networks -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts and Theories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 "environmental law", "law of the sea", "European law" and even such exotic and highly specialized knowledge as "investment law" or "international refugee law" etc. -each possessing their own principles and institutions. The problem, as lawyers have seen it, is that such specialized law-making and institution-building tends to take place with relative ignorance of legislative and institutional activities in the adjoining fields and of the general principles and practices of international law." Here, we can see how "law-governed emergence" operates in practice. That is, although those free-standing regimes (secondary institutions) are in principle bound by the general rules of the primary institution in which they are embedded (international law), they have their own binding dispute settlement mechanism, essentially making and applying rules according to their own procedural norms. As Koskenniemi (2006, p. 4) observed, they are "interrelated wholes of primary and secondary rules, sometimes also referred to as 'systems' or 'subsystems' of rules that cover some particular problem differently from the way it would be covered under general law." The consequences for linear patterns of order making are exemplified by some of the inconsistent judgments and conflicting jurisprudence issued by different international courts, and the way in which this tends to undermine the value of precedent as the main "guarantor of certainty and equality of treatment" (Guillaume, 2011, p. 6). For example, in judging on whether the government of Serbia and Montenegro was responsible for act of violence conducted by irregular militias, the International Criminal Tribunal for the Former Yugoslavia revisited the International Court of Justice's (ICJ) ruling regarding state responsibility in the Nicaragua case, triggering a dispute among the two courts about the appropriate test for determining when states are responsible for the use of irregular force. The limitations those non-linear processes of law making impose on Article 59 of the ICJ statute for developing international public law in a coherent and systematic fashion are well known (Kratochwil, 2014, pp. 93-97).
Considering how and why primary institutions have become fragmented is one area for future research. The first task here is to conceptualise degrees of fragmentation. The regime complexity literature offers good points of departure. For example, Biermann et al (2009: 19-21) have distinguished between synergistic, cooperative, and conflictive types of fragmentation. Building on this typology could also help to get to grips with fragmentation dynamics in primary institutions. The second task is empirical. English School scholars need to develop tools for comparing fragmentations in different primary institutions. This would, for example, require network analysis to map out the network structure of primary institutions, by locating nodes and identifying links among different institutional arrangements. Such a method may sit uneasy with the English School's traditional methodological focus on historical, sociological, and normative inquiry, but it offers an interesting tool for expanding the scope of the School's research agenda.

Clustering primary institutions
Another consequence associated with emergence is institutional clustering. This has to do with the linkages primary institutions develop in a complex international society. Because norms and beliefs do not always line up so as to form a consistent overarching normative structure, there is good reason to assume that the interplay between primary institutions is more often than not characterised by resistance, contestation, and alteration. Williams (2015, p. 122) briefly points to the inherent tensions among primary institutions, by noting that "their constitutive roles introduce many of the tensions, dilemmas, contradictions and frictions of international relations, when competing and irreconcilable constitutive institutions pull us in different directions in the face of events and circumstances which the same institutions grant different levels of types of significance." In contemporary international society, conflicts and tensions between different primary institutions are perhaps most evident in our debates about humanitarian interventions, in which cosmopolitan moral appeals to human rights norms frequently rub-up against formalised Westphalian rules of non-intervention. NATO's intervention in Kosovo in the 1990s, which was deemed "illegal but justified" by the international legal community, perhaps stands as the clearest example of the way in which a fundamental institutional ordering practice such as sovereignty can be legitimately contested under appeal to human rights (Independent International Commission on Kosovo, 2000, p. 4).
The debate about humanitarian intervention -and the normative tensions between sovereignty and human rights norms that come with it -is a good example. Typically, the stalemate in those debates has been broken in favour of one institution, with some scholars privileging sovereignty and territorial integrity over the protection of individuals (Jackson, 2000), while others have advocated for the occasional suspension of non-intervention claims in the face of severe humanitarian emergencies (Wheeler, 2000). Privileging one primary institution over another when confronted with conflict is certainly an attractive option, not at least because it has helped to formulate a more or less coherent vision of order in international society. But it comes at the expense of considering the entanglements of, and relationships between, different primary institutions.
A different way to approach this is through the notion of institutional clustering. Building on Oran Young's (1996: 5-6) typology of institutional linkages, I define clustering as the result of combining two or more, analytically differentiable primary institutions into an institutional package. Clustering of primary institutions occurs when members of international society join together analytically distinct primary institutions for the purpose of resolving conflicts among fundamental social ordering principles and practices. The emergence of the Responsibility to Protect (R2P) doctrine set out in 2005 World Summit Outcome, which ascribes a responsibility to sovereign states to protect their populations from genocide, war crimes, crimes against humanity and ethnic cleansing, is case in point. Rather than having to choose between either the protection of human rights or upholding sovereignty when faced with these crimes, R2P indicates international society's effort to combine the two institutional practices -by making sovereignty conditional upon the ability and willingness of a state to protect its populations from severe human rights abuses. We may observe similar clustering dynamics between sovereignty and environmental stewardship in the future, given that the latter calls for "a global system perspective and coordinated rules of the game that transcend borders" (Buzan and Falkner 2019: 149).

Conclusion
The concepts and language of complexity theory speak directly to a number of concerns that are central to the widening and broadening of the interaction in social, economic, and political dynamics, scales and levels that characterise contemporary international relations. This article has sought to lay the groundwork for a systematic engagement between the English School of IR and complexity theory and, in particular, for an English School approach to complex systems thinking. The emphasis English School theory places on evolutionary change, the reflexivity of systems and boundaries, and relational social processes at the global level enables complex systems thinking to flourish. Harvesting those synergies and using ideas and concepts from complexity could not only open up new space for debate about the current transformation processes and dynamics that shape global international society, but also push English School scholars to re-think some of their more established models and assumptions.
Focusing on one specific strand of current English School theorising, the article has introduced the notion of fragmentation dynamics and applied it to the study of international institutions. If primary institutions are to play a significant role in exploring the normative framework of international society, then we need to improve our understanding of their different institutional compositions and internal structures. Here, the idea of fragmentation dynamics may open some critical analytical space. Consideration of decentralisation and localisation offers an alternative conceptualisation of the nature and structure of international society's fundamental ordering practices that stresses the inescapability of normative tensions and contradictions among them. Once we recognise bottom-up processes of emergence, fragmentation, and decentralised interaction dynamics become part and parcel of institutional English School thinking. Complexity, Governance & Networks -Vol. 6, No 1 (2020) Special Issue: Global Governance in Complex Times: Exploring New Concepts and Theories on Institutional Complexity, p. 94-108 DOI: http://dx.doi.org/10.20377/cgn-105 There are some more general implications of this for English School's intellectual structure that are potentially radical. While the conceptual developments advanced in the second half of this article have primarily been social-structural in the sense that they have focused on the formal dynamics between international society's institutional building-blocks, they also have normative consequences. By allowing for fragmentation and competition among primary institutions, complexity presents a fundamental challenge to those who presume some sort of normative consensus about the ethical content and moral purpose of international society's basic institutional ordering practices. If we accept the argument that even primary institutions evolve in non-linear ways and do not always line up coherently, then English School scholars need to address the way in which the values and moral principles inscribed in institutional practice emerge and transform. This connects complexity thinking to recent pluralist English School scholarship that treats ethical diversity and value conflict as both an empirical reality of international relations and a normatively desirable feature of the human condition (e.g. Williams 2015).