1 The Characteristics of Complexity
Complexity theory is a way of seeing the world that is flourishing in a variety of disciplines in the sciences and the arts. As complex systems are âusually associated with living thingsâ,1 complexity theory is deployed to explore a diverse range of phenomena from the creation of life to the aggregation of the slime mould, from the organisation of business corporations to the reshuffling of carbon atoms in a sea urchin embryo.2 Complexity theory can be applied âto cosmic, galactic, stellar, planetary, chemical, biological, and social systemsâ.3 It is widely applicable because the principles of complexity apply to systems, not to the content of those systems: âWhat matters are the relationships, not the content matter.â4 The modelling of complex systems applies to the relationships between component parts, not to the physical manifestation of the parts themselves.5 This is why the sciences of complexity are ânomadicâ; they are applicable in various fields.6
Given that the study of complexity theory is concerned with the identification and investigation of complex systems, it is worth first clarifying the meaning of âsystemâ. The word may be misleading due to its familiar connotations of mechanistic order and regularity. Labelling a sophisticated phenomenon (such as weather patterns, ecosystems or the human brain) a complex âsystemâ can imply that the phenomenon is structured by some kind of predetermined plan. We need to be clear about the difference between a âsystemâ and a âcomplex systemâ. Not all systems are complex; some may be simply complicated. Adrian Mackenzie explicitly warns against the âgeneralityâ of complexity theory, arguing that:
The generalisation of complexity into a world-view turns thought in circles on itself. It becomes a movement that goes nowhere because it encounters no obstacles and takes no risks: âeverything is complexâ.7
While it is possible to use complexity theory as a way of seeing the world across many disciplines and areas of life, it does not follow that all systems encountered must be complex. The chief difference between a generic idea of âsystemâ and a complex system is the systemâs method of organisation. The primary understanding of a system is: âa whole composed of parts in orderly arrangement according to some scheme or planâ.8 However a complex systemâs âorderly arrangementâ does not derive from a predetermined scheme or plan: it is ordered by the unpredictable interaction of its parts. These interactions must be dynamic, because a complex system is made up of elements that exert influences upon each other and, in the process, effect changes in themselves and others.9 The importance of interactions to a systemâs complexity cannot be overstated. In fact, âthe lack of dependence on any feedback or interactions between objects will make the overall system non-complexâ.10
In its simplest form, then, a non-complex system is a grouping of related parts, ideas, or phenomena, which are organised by some kind of scheme or plan. By contrast, a complex system is identifiable by its unique organising pattern. Complex systems are self-organising, dynamic, evolving networks that operate without any centralised control. They are organised spontaneously and are composed of ongoing interactions between different parts. Despite being part of a complex system, these interacting parts may behave in quite simple ways: simple interactions can produce more complex behaviours and structures.11 It is these interactions â sometimes simple, yet also unpredictable, diverse and numerous â which constitute the system itself, and the phenomena that emerge from these exchanges enable the system to continue developing.
This concept of âemergenceâ is the reason why complexity theory privileges the interactions of a systemâs elements, as it is not in the parts but in their relationships that the systemâs complexity emerges: âcomponents of a system through their interaction âspontaneouslyâ develop collective properties or patternsâ.12 Although emerging from a complex systemâs micro-dynamics, emergent phenomena cannot be reducible to them.13 This emergence is related to the systemâs ability to spontaneously produce order out of chaotic and disorganised behavioural states. Complex systems can vary from stable to increasingly disordered phases. When a system becomes highly disordered, it enters a phase called âbounded instabilityâ or âthe edge of chaosâ.14 At such points, a system is far more likely to produce new, creative phenomena and behaviours that may drastically change the system or parts of it. The chaotic state thus generates new forms of order.
The 13 Characteristics of a Complex System
The following characteristics of complex systems provide the foundation of complexity theoryâs key concepts, upon which this book is built. As well as offering a guide to the key characteristics of complexity incorporated throughout, these characteristics also function as a standalone list that will be applicable for readers wishing to utilise complexity theory in their own studies or fields. It offers a base for developing a working understanding of complex systems. These characteristics build on Paul Cilliersâ formative list, which has been influential in complexity studies.15
1 Complex systems are composed of many parts, elements, agents, or individuals (these may include living and non-living things). In this way a complex system can be thought of as âdecentralisedâ or distributed across its component parts.
2 A complex system is generated by a specific type of interactivity: the parts must interact in what Cilliers calls âdynamicâ and ârichâ ways â in other words, the systemâs parts influence and are influenced by each other. The interaction is usually localised, and may comprise communication between individuals, groups and the environment.16
3 The interactions â and system patterns more broadly â are nonlinear. Their behaviour can appear unpredictable and consequences of the systemâs interactions can be disproportionate.
4 A complex system is sustained by positive (turbulent) and negative (stabilising) feedback. In essence, the systemâs interactions or output feed back into the system, creating interaction loops. Both positive and negative feedback are necessary for the system. Positive feedback âgenerally promotes changes in a systemâ,17 and can also be referred to as turbulence or perturbation. Negative feedback is behaviour that works to counteract turbulence experienced by a system.18
5 Complex systems are open â which means they interact with their environment. This makes it very difficult to define the systemâs borders. What we identify as belonging to the system or to the systemâs context is dependent upon the objectives and perspectives of the researcher.19 An examination of any complex system is thus also a âform of worldmakingâ.20 The system is inevitably a âconceptual constructionâ or a model that is similar to but not the same as the reality it models.21
6 Complex systems require instability to survive. In fact, although such systems can behave in ordered, semi-ordered, or highly disordered ways, a certain point between organisation and chaos is understood to be the most productive and beneficial for the system. Complex systems can âachieve a âpoisedâ state near the boundary between order and chaos, a state which optimises the complexity of tasks the systems can perform and simultaneously optimises evolvabilityâ.22 This liminal state is called either âthe edge of chaosâ or âbounded instabilityâ.23
7 A system has a history. The past is co-responsible with the present for the systemâs behaviour.
8 Every element or part within a system is ignorant of the behaviour of the system as a whole. An individual only understands the system insofar as they understand their local interactions. The complexity of the system is not produced by any individualâs knowledge or design but as a result of the interactions between elements or parts.
9 A complex system is multilayered, comprising many levels or scales of interaction. A systemâs levels can be understood spatially and temporally â they indicate both the size and age of the system.24 This complex âhierarchyâ of levels can run from atoms to molecules, tissues to organisms, populations to communities.25 This enables multiple perspectives on a system: from a macrocosmic view to a microcosmic or local perspective, to anywhere between âthe molecular and the macroâ.26 A systemâs levels are therefore conceptualised through the observerâs proximity to the system. The field of neurobiology provides a us...