Emergence

In the so-called sciences of complexity (e.g., non-linear dynamics, theoretical biology, complex adaptive systems, artificial life, artificial intelligence, cognitive science), “complex” phenomena, such as the appearance of life on Earth, the evolution of new species, or the structure of cognitive thought, are often considered as instances of some emergent higher-order structure that may be explained by the lower-level dynamics generating the collective behaviour or emergent property of the system in question. Thus the old idea of emergent evolution (cf. Blitz 1992) has recently attracted much attention and created new interest in the level-structure of the universe.[1]

Typically, people describe emergence as the phenomenon where global behaviour arises from the interactions between de local parts of the system. In most literature there is nothing more than this vague description. Conceptual constructs such as ‘whole before its parts’ (i.e. to consider an explanation in terms of the global behaviour more important than explaining how the system works in terms of local behaviour) and ‘Gestalt’ (i.e. a configuration or pattern of elements so unified as a whole that it cannot be described merely as a sum of its parts), which resemble emergence, can be found in western thought since the time of ancient Greeks. However, ‘whole before its parts’ and ‘Gestalt’ refer to a pre-given coherent entity, whereas emergence is not pre-given but a dynamical construct arising over time. The concept of emergence was hotly debated and mainly used against reductionism, which stated that a system can be reduced to the sum of its parts. Emergence refers to two important characteristics: a global behaviour that arises from the interactions of the local parts, and that global behaviour cannot be traced back to the individual parts.

A second movement, called neo-emergence or complexity theory, tries to address the lack of understanding emergence. Four different schools exist:

• Complex adaptive systems theory: macro-level patterns arising from interacting agents
• Nonlinear dynamical systems theory and Chaos theory, which promulgates the central concept of attractors, i.e. a specific behaviour to which the system evolves
• The synergetics school, which initiated, among others, the study of emergence in physical systems. They describe the idea of an order parameter that influences which macro-level coherent phenomena a system exhibits
• Far-from-equilibrium thermodynamics, which was introduced by Ilya Prigogine and which refers to emergent phenomena as dissipative structures arising at far-from-equilibrium conditions

A system exhibits emergence when there are coherent emergents at the macro-level that dynamically arise from the interactions between the parts at the micro-level. Such emergents are novel w.r.t. the individual parts of the system.

Emergent is the result of a process of emergence: properties, behaviour, structure, patterns, while the level is a point of view. The micro-macro effect: the global behaviour of the system (i.e. the emergent) is a result from the interactions between the individual entities of the system. Radical Novelty: The global behaviour is novel w.r.t. the individual behaviours at the micro-level, i.e. the individuals at the micro-level have no explicit representation of the global behaviour. In terms of reductionism this is formulated as: the macro-level emergents are not reducible to the micro-level parts of the system (= non-reductionism). ‘neither predictable nor deducible from’. Radical novelty arises because the collective behaviour is not readily understood from the behaviour of the parts. The collective behaviour is, however, implicitly contained in the behaviour of the parts if they are studied in the context in which they are found. Emergent properties cannot be studied by physically taking a system apart and looking at the parts (=reductionism). They can, however, be studied by looking at each of the parts in the context of the system as a whole. Coherence refers to a logical and consistent correlation of parts. Emergents appear as integrated wholes that tend to maintain some sense of identity over time. Correlations between components are needed to reach a coherent whole. Interacting parts are necessary and paralelism is not enough for the emergents to arise. The system must be dynamical as the emergents arise as the system evolves over time as a new kind of behaviour that eventually becomes possible: there is an appearance of new attractors in ddynamical systems (bifurcations). Decentralised control Two way link between the micro and the macro: micro $\rightarrow$ macro is emergence, while the high-level emergent properties have causal effects on the lower level (downward causation).
Robustness and Flexibility since no single entity have information about the emergents, no single entity can be a cause of failure: the loss of function is gradual with respect to damage.

References

[1] Bass & Emmeche “On emergnce and explanation”

[2] Wolf & Holvoet “Emergence Versus Self-organisation: Different Concepts but Promising When Combined”