> http://en.wikipedia.org/wiki/Emergence
>
> Definitions
> The concept behind the term has been in use since at least the time of
> Aristotle.[1] John Stuart Mill and Julian Huxley are just some of the
> historic luminaries who have written on the concept.
>
> The term "emergent" was coined by the pioneer psychologist G. H.
>
> Lewes, who wrote:
>
> "Every resultant is either a sum or a difference of the co-operant
> forces; their sum, when their directions are the same -- their
> difference, when their directions are contrary. Further, every
> resultant is clearly traceable in its components, because these are
> homogeneous and commensurable. It is otherwise with emergents, when,
> instead of adding measurable motion to measurable motion, or things of
> one kind to other individuals of their kind, there is a co-operation
> of things of unlike kinds. The emergent is unlike its components
> insofar as these are incommensurable, and it cannot be reduced to
> their sum or their difference." (Lewes 1875, p. 412)(Blitz 1992)
>
> Professor Jeffrey Goldstein in the School of Business at Adelphi
> University provides a current definition of emergence in the journal,
> Emergence.(Goldstein 1999). For Goldstein, emergence can be defined
> as: "the arising of novel and coherent structures, patterns and
> properties during the process of self-organization in complex
> systems."(Corning 2002)
>
> Goldstein's definition can be further elaborated to describe the
> qualities of this definition in more detail:
>
> "The common characteristics are: (1) radical novelty (features not
> previously observed in systems); (2) coherence or correlation (meaning
> integrated wholes that maintain themselves over some period of time);
> (3) A global or macro "level" (i.e. there is some property of
> "wholeness"); (4) it is the product of a dynamical process (it
> evolves); and (5) it is "ostensive" - it can be perceived. For good
> measure, Goldstein throws in supervenience -- downward
> causation." (Corning 2002)
>
> Strong vs. weak emergence
> Emergence may be generally divided into two perspectives, that of
> "weak emergence" and "strong emergence". Weak emergence describes new
> properties arising in systems as a result of the interactions at an
> elemental level. Emergence, in this case, is merely part of the
> language, or model that is needed to describe a system's behaviour.
>
> But if, on the other hand, systems can have qualities not directly
> traceable to the system's components, but rather to how those
> components interact, and one is willing to accept that a system
> supervenes on its components, then it is difficult to account for an
> emergent property's cause. These new qualities are irreducible to the
> system's constituent parts (Laughlin 2005). The whole is greater than
> the sum of its parts. This view of emergence is called strong
> emergence. Some fields in which strong emergence is more widely used
> include etiology, epistemology and ontology.
>
> Regarding strong emergence, Mark A. Bedau observes:
>
> "Although strong emergence is logically possible, it is uncomfortably
> like magic. How does an irreducible but supervenient downward causal
> power arise, since by definition it cannot be due to the aggregation
> of the micro-level potentialities? Such causal powers would be quite
> unlike anything within our scientific ken. This not only indicates how
> they will discomfort reasonable forms of materialism. Their
> mysteriousness will only heighten the traditional worry that emergence
> entails illegitimately getting something from nothing."(Bedau 1997)
>
> However, "the debate about whether or not the whole can be predicted
> from the properties of the parts misses the point. Wholes produce
> unique combined effects, but many of these effects may be co-
> determined by the context and the interactions between the whole and
> its environment(s)." (Corning 2002) Along that same thought, Arthur
> Koestler stated, "it is the synergistic effects produced by wholes
> that are the very cause of the evolution of complexity in nature" and
> used the metaphor of Janus to illustrate how the two perspectives
> (strong or holistic vs. weak or reductionistic) should be treated as
> perspectives, not exclusives, and should work together to address the
> issues of emergence.(Koestler 1969) Further,
>
> "The ability to reduce everything to simple fundamental laws does not
> imply the ability to start from those laws and reconstruct the
> universe..The constructionist hypothesis breaks down when confronted
> with the twin difficulties of scale and complexity. At each level of
> complexity entirely new properties appear. Psychology is not applied
> biology, nor is biology applied chemistry. We can now see that the
> whole becomes not merely more, but very different from the sum of its
> parts."(Anderson 1972)
>
> Objective or subjective quality
> The properties of complexity and organization of any system are
> considered by Crutchfield to be subjective qualities determined by the
> observer.
>
> "Defining structure and detecting the emergence of complexity in
> nature are inherently subjective, though essential, scientific
> activities. Despite the difficulties, these problems can be analysed
> in terms of how model-building observers infer from measurements the
> computational capabilities embedded in non-linear processes. An
> observer’s notion of what is ordered, what is random, and what is
> complex in its environment depends directly on its computational
> resources: the amount of raw measurement data, of memory, and of time
> available for estimation and inference. The discovery of structure in
> an environment depends more critically and subtly, though, on how
> those resources are organized. The descriptive power of the observer’s
> chosen (or implicit) computational model class, for example, can be an
> overwhelming determinant in finding regularity in data."(Crutchfield
> 1994)
>
> On the other hand, Peter Corning argues "Must the synergies be
> perceived/observed in order to qualify as emergent effects, as some
> theorists claim? Most emphatically not. The synergies associated with
> emergence are real and measurable, even if nobody is there to observe
> them." (Corning 2002)
>
> Emergence in philosophy
> In philosophy, emergence is often understood to be a much stronger
> claim about the etiology of a system's properties. An emergent
> property of a system, in this context, is one that is not a property
> of any component of that system, but is still a feature of the system
> as a whole. Nicolai Hartmann, one of the first modern philosophers to
> write on emergence, termed this categorial novum (new category).
>
> Emergent properties and processes
> An emergent behaviour or emergent property can appear when a number of
> simple entities (agents) operate in an environment, forming more
> complex behaviours as a collective. If emergence happens over
> disparate size scales, then the reason is usually a causal relation
> across different scales. In other words there is often a form of top-
> down feedback in systems with emergent properties. The processes from
> which emergent properties result may occur in either the observed or
> observing system, and can commonly be identified by their patterns of
> accumulating change, most generally called 'growth'. Why emergent
> behaviours occur include: intricate causal relations across different
> scales and feedback, known as interconnectivity. The emergent property
> itself may be either very predictable or unpredictable and
> unprecedented, and represent a new level of the system's evolution.
> The complex behaviour or properties are not a property of any single
> such entity, nor can they easily be predicted or deduced from
> behaviour in the lower-level entities: they are irreducible. No
> physical property of an individual molecule of air would lead one to
> think that a large collection of them will transmit sound. The shape
> and behaviour of a flock of birds[1] or shoal of fish are also good
> examples.
>
> One reason why emergent behaviour is hard to predict is that the
> number of interactions between components of a system increases
> combinatorially with the number of components, thus potentially
> allowing for many new and subtle types of behaviour to emerge. For
> example, the possible interactions between groups of molecules grows
> enormously with the number of molecules such that it is impossible for
> a computer to even count the number of arrangements for a system as
> small as 20 molecules.
>
> On the other hand, merely having a large number of interactions is not
> enough by itself to guarantee emergent behaviour; many of the
> interactions may be negligible or irrelevant, or may cancel each other
> out. In some cases, a large number of interactions can in fact work
> against the emergence of interesting behaviour, by creating a lot of
> "noise" to drown out any emerging "signal"; the emergent behaviour may
> need to be temporarily isolated from other interactions before it
> reaches enough critical mass to be self-supporting. Thus it is not
> just the sheer number of connections between components which
> encourages emergence; it is also how these connections are organised.
> A hierarchical organisation is one example that can generate emergent
> behaviour (a bureaucracy may behave in a way quite different from that
> of the individual humans in that bureaucracy); but perhaps more
> interestingly, emergent behaviour can also arise from more
> decentralized organisational structures, such as a marketplace. In
> some cases, the system has to reach a combined threshold of diversity,
> organisation, and connectivity before emergent behaviour appears.
>
> Unintended consequences and side effects are closely related to
> emergent properties. Luc Steels writes: "A component has a particular
> functionality but this is not recognizable as a subfunction of the
> global functionality. Instead a component implements a behaviour whose
> side effect contributes to the global functionality [...] Each
> behaviour has a side effect and the sum of the side effects gives the
> desired functionality" (Steels 1990). In other words, the global or
> macroscopic functionality of a system with "emergent functionality" is
> the sum of all "side effects", of all emergent properties and
> functionalities.
>
> Systems with emergent properties or emergent structures may appear to
> defy entropic principles and the second law of thermodynamics, because
> they form and increase order despite the lack of command and central
> control. This is possible because open systems can extract information
> and order out of the environment.
>
> Emergence helps to explain why the fallacy of division is a fallacy.
> According to an emergent perspective, intelligence emerges from the
> connections between neurons, and from this perspective it is not
> necessary to propose a "soul" to account for the fact that brains can
> be intelligent, even though the individual neurons of which they are
> made are not.
>
> Emergent structures in nature
> Emergent structures are patterns not created by a single event or
> rule. Nothing commands the system to form a pattern. Instead, the
> interaction of each part with its immediate surroundings causes a
> complex chain of processes leading to some order. One might conclude
> that emergent structures are more than the sum of their parts because
> the emergent order will not arise if the various parts are simply
> coexisting; the interaction of these parts is central. Emergent
> structures can be found in many natural phenomena, from the physical
> to the biological domain. For example, the shape of weather phenomena
> such as hurricanes are emergent structures.
>
> It is useful to distinguish three forms of emergent structures. A
> first-order emergent structure occurs as a result of shape
> interactions (for example, hydrogen bonds in water molecules lead to
> surface tension). A Second-order emergent structure involves shape
> interactions played out sequentially over time (for example, changing
> atmospheric conditions as a snowflake falls to the ground build upon
> and alter its form). Finally, a third-order emergent structure is a
> consequence of shape, time, and heritable instructions. For example,
> an organism's genetic code sets boundary conditions on the interaction
> of biological systems in space and time.
>
> Non-living, physical systems
> In physics, emergence is used to describe a property, law, or
> phenomenon which occurs at macroscopic scales (in space or time) but
> not at microscopic scales, despite the fact that a macroscopic system
> can be viewed as a very large ensemble of microscopic systems.
>
> An emergent property need not be more complicated than the underlying
> non-emergent properties which generate it. For instance, the laws of
> thermodynamics are remarkably simple, even if the laws which govern
> the interactions between component particles are complex. The term
> emergence in physics is thus used not to signify complexity, but
> rather to distinguish which laws and concepts apply to macroscopic
> scales, and which ones apply to microscopic scales.
>
> Some examples include:
>
> Colour: Elementary particles have no colour; it is only when they are
> arranged in atoms that they absorb or emit specific wavelengths of
> light and can thus be said to have a colour.
> Friction: Forces between elementary particles are conservative.
> However, friction emerges when considering more complex structures of
> matter, whose surfaces can convert mechanical energy into heat energy
> when rubbed against each other. Similar considerations apply to other
> emergent concepts in continuum mechanics such as viscosity,
> elasticity, tensile strength, etc.
> Classical mechanics: The laws of classical mechanics can be said to
> emerge as a limiting case from the rules of quantum mechanics applied
> to large enough masses. This may be puzzling, because quantum
> mechanics is generally thought of as more complicated than classical
> mechanics.
> Statistical mechanics was initially derived using the concept of a
> large enough ensemble that fluctuations about the most likely
> distribution can be all but ignored. However, small clusters do not
> exhibit sharp first order phase transitions such as melting, and at
> the boundary it is not possible to completely categorize the cluster
> as a liquid or solid, since these concepts are (without extra
> definitions) only applicable to macroscopic systems. Describing a
> system using statistical mechanics methods is much simpler than using
> a low-level atomistic approach.
> Patterned ground: the distinct, and often symmetrical geometric shapes
> formed by ground material in periglacial regions.
> Temperature is sometimes used as an example of an emergent macroscopic
> behaviour. In classical dynamics, a snapshot of the instantaneous
> momenta of a large number of particles at equilibrium is sufficient to
> find the average kinetic energy per degree of freedom which is
> proportional to the temperature. For a small number of particles the
> instantaneous momenta at a given time are not statistically sufficient
> to determine the temperature of the system. However, using the ergodic
> hypothesis, the temperature can still be obtained to arbitrary
> precision by further averaging the momenta over a long enough time.
>
> Convection in a fluid or gas is another example of emergent
> macroscopic behaviour that makes sense only when considering
> differentials of temperature. Convection cells, particularly Bénard
> cells, are an example of a self-organizing system (more specifically,
> a dissipative system) whose structure is determined both by the
> constraints of the system and by random perturbations: the possible
> realizations of the shape and size of the cells depends on the
> temperature gradient as well as the nature of the fluid and shape of
> the container, but which configurations are actually realized is due
> to random perturbations (thus these systems exhibit a form of symmetry
> breaking).
>
> In some theories of particle physics, even such basic structures as
> mass, space, and time are viewed as emergent phenomena, arising from
> more fundamental concepts such as the Higgs boson or strings. In some
> interpretations of quantum mechanics, the perception of a
> deterministic reality, in which all objects have a definite position,
> momentum, and so forth, is actually an emergent phenomenon, with the
> true state of matter being described instead by a wavefunction which
> need not have a single position or momentum. Most of the laws of
> physics themselves as we experience them today appear to have emerged
> during the course of time making emergence the most fundamental
> principle in the universe and raising the question of what might be
> the most fundamental law of physics from which all others emerged.
> Chemistry can in turn be viewed as an emergent property of the laws of
> physics. Biology (including biological evolution) can be viewed as an
> emergent property of the laws of chemistry. Finally, psychology could
> at least theoretically be understood as an emergent property of
> neurobiological laws.
>
> Living, biological systems
> Life is a major source of complexity, and evolution is the major
> principle or driving force behind life. In this view, evolution is the
> main reason for the growth of complexity in the natural world. If we
> speak of the emergence of complex living beings and life-forms, we
> refer therefore to processes of sudden changes in evolution.
>
> Flocking is a well-known behaviour in many animal species from
> swarming locusts to fish and birds. Emergent structures are a common
> strategy found in many animal groups: colonies of ants, mounds built
> by termites, swarms of bees, shoals/schools of fish, flocks of birds,
> and herds/packs of mammals.
>
> An example to consider in detail is an ant colony. The queen does not
> give direct orders and does not tell the ants what to do. Instead,
> each ant reacts to stimuli in the form of chemical scent from larvae,
> other ants, intruders, food and build up of waste, and leaves behind a
> chemical trail, which, in turn, provides a stimulus to other ants.
> Here each ant is an autonomous unit that reacts depending only on its
> local environment and the genetically encoded rules for its variety of
> ant. Despite the lack of centralized decision making, ant colonies
> exhibit complex behavior and have even been able to demonstrate the
> ability to solve geometric problems. For example, colonies routinely
> find the maximum distance from all colony entrances to dispose of dead
> bodies.
>
> A broader example of emergent properties in biology is the combination
> of individual atoms to form molecules such as polypeptide chains,
> which in turn fold and refold to form proteins. These proteins,
> assuming their functional status from their spatial conformation,
> interact together to achieve higher biological functions and
> eventually create - organelles, cells, tissues, organs, organ systems,
> organisms. Cascade phenotype reactions, as detailed in Chaos theory,
> may arise from individual genes mutating respective positioning.[4] In
> turn, all the biological communities in the world form the biosphere,
> where its human participants form societies, and the complex
> interactions of meta-social systems such as the stock market.
>
> Emergence in culture and engineering
> Emergent processes or behaviours can be seen in many places, such as
> traffic patterns, cities, political systems of governance, cabal and
> market-dominant minority phenomena in politics and economics,
> organizational phenomena in computer simulations and cellular
> automata.
>
> Economics
> The stock market is an example of emergence on a grand scale. As a
> whole it precisely regulates the relative security prices of companies
> across the world, yet it has no leader; there is no one entity which
> controls the workings of the entire market. Agents, or investors, have
> knowledge of only a limited number of companies within their
> portfolio, and must follow the regulatory rules of the market and
> analyse the transactions individually or in large groupings. Trends
> and patterns emerge which are studied intensively by technical
> analysts.
>
> World Wide Web
> The World Wide Web (WWW) is a popular example of a decentralized
> system exhibiting emergent properties. There is no central
> organization rationing the number of links, yet the number of links
> pointing to each page follows a power law in which a few pages are
> linked to many times and most pages are seldom linked to. A related
> property of the network of links in the world wide web is that almost
> any pair of pages can be connected to each other through a relatively
> short chain of links. Although relatively well known now, this
> property was initially unexpected in an unregulated network. It is
> shared with many other types of networks called small-world networks.
> [citation needed]
>
> Architecture and cities
> Emergent structures appear at many different levels of organization or
> as spontaneous order. Emergent self-organization appears frequently in
> cities where no planning or zoning entity predetermines the layout of
> the city. (Krugman 1996, pp. 9-29) The interdisciplinary study of
> emergent behaviors is not generally considered a homogeneous field,
> but divided across its application or problem domains.
>
> Often architects and landscapers will not design all the pathways of a
> complex of buildings. Instead they will let usage patterns emerge and
> then place pavement where pathways have become worn in.
>
> The on-course action and vehicle progression of the 2007 Urban
> Challenge could possibly be regarded as an example of cybernetic
> emergence. Patterns of road use, nondeterministic obstacle clearance
> times, etc. will work together to form a complex emergent pattern that
> can not be deterministically planned in advance.
>
> Mathematics
>
> A Möbius strip in mathematics demonstrates emergenceAlthough the above
> examples of emergence are often contentious, mathematics provides a
> rigorous basis for defining and demonstrating emergence. In Emergence
> is coupled to scope, not level, Alex Ryan shows that a Möbius strip
> has emergent properties (Ryan 2006). The Möbius strip is a one-sided,
> one-edged surface. Further, a Möbius strip can be constructed from a
> set of two-sided, three edged, triangular surfaces. Only the complete
> set of triangles is one-sided and one-edged: any subset does not share
> these properties. Therefore, the emergent property can be said to
> emerge precisely when the final piece of the Möbius strip is put in
> place. An emergent property is a spatially or temporally extended
> feature – it is coupled to a definite scope, and cannot be found in
> any component because the components are associated with a narrower
> scope.
>
> Pithily, emergent properties are those that are global, topological:
> properties of the whole.
>
> Language
> It has been argued that language, or at least language change, are
> emergence phenomena. While each speaker merely tries to reach his own
> communicative goals, he uses language in a particular way. If enough
> speakers behave in that way, language is changed (Keller 1994).
>
> Fads and beliefs
>  This article or section may contain original research or unverified
> claims.
> Please improve the article by adding references. See the talk page for
> details. (October 2007)
>
> An emergent concept (EC) is a slight variation on consensus reality
> that is accepted as plausible. The hallmarks of an emergent concept,
> as opposed to some categories of Internet memes/phenomena, urban
> myths, or the like, are that EC are increasingly accepted as truth or
> plausible, based upon other empirical or anecdotal evidence in the
> mind of the believer or society (in its subsets) as a whole.
>
> Emergence in political philosophy
>  This article or section may contain original research or unverified
> claims.
> Please improve the article by adding references. See the talk page for
> details. (September 2007)
>
> Economist and philosopher Friedrich Hayek wrote about emergence in the
> context of law, politics, and markets. His theories are most fully
> developed in Law, Legislation and Liberty, which sets out the
> difference between cosmos or "grown order" (that is, emergence), and
> taxis or "made order". Hayek dismisses philosophies that do not
> adequately recognize the emergent nature of society, and which
> describe it as the conscious creation of a rational agent (be it God,
> the Sovereign, or any kind of personified body politic, such as
> Hegel's state or Hobbes's leviathan). The most important social
> structures, including the laws ("nomos") governing the relations
> between individual persons, are emergent, according to Hayek. While
> the idea of laws and markets as emergent phenomena comes fairly
> naturally to an economist, and was indeed present in the works of
> early economists such as Bernard Mandeville, David Hume, and Adam
> Smith, Hayek traces the development of ideas based on spontaneous-
> order throughout the history of Western thought, occasionally going as
> far back as the presocratics. In this, he follows Karl Popper, who
> blamed the idea of the state as a made order on Plato in The Open
> Society and its Enemies.
>
> Emergence in organisational theory
> Emergence is referred to as the complex process whereby the right
> person or idea emerges exactly at the right moment. Just when a
> problem occurs or a necessity, the potential solutions also emerges