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| turtoni... |
 Posted: Sat Jun 21, 2008 4:25 pm |
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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 |
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