Main Page | See live article | Alphabetical index


Self-organization refers to a process in which the internal organization of a system, normally an open system, increases automatically without being guided or managed by an outside source.

Table of contents
1 Introduction
2 History of the idea
3 Examples
4 References and links


The most robust and unambiguous examples of self-organizing systems are from physics, where the concept was first noted. Self-organization is also relevant in chemistry, where it has often been taken as being synonymous with self-assembly. The concept of self-organization is central to the description of biological systems, from the subcellular to the ecosystem level. There are also cited examples of "self-organizing" behaviour found in the literature of many other disciplines, both in the sciences and the social sciences such as economics anthropology. Self-organization has also been observed in mathematical systems such as cellular automata.

Sometimes the notion of self-organization is conflated with that of the related concept of emergence. Properly defined, however, there may be instances of self-organization without emergence and emergence without self-organization, and it is not clear from the literature that the phenomenon are the same. The link between emergence and self-organization remains an active research question.

History of the idea

The idea that the dynamics of a system can tend, by themselves, to make it more orderly, has a long history. One of the first statements of this idea is Descartes, in the fifth part of his Discourse on Method, where he presents it hypothetically. Descartes further elaborated on the idea at great length in a book called Le Monde which was never published.

The ancient atomists (among others) had argued that a designing intelligence was unnecessary, but they generally argued that given enough time and space and matter, organization is bound to happen at some point, but not that there would be any tendency for this to happen. What Descartes introduced was the idea that the ordinary laws of nature tend to produce organization. (For related history, see Avram Vartanian, From Descartes to Diderot.)

Starting with the 18th century naturalistss, there was a movement to try to understand the "universal laws or form" in order to explain the observed forms of living organisms. Because of its association with Lamarckism, these theories fell into disrepute until the early 20th century, where pioneers like D'Arcy Wentworth Thompson rescued it. The modern understanding is that there are indeed universal laws (coming from physics and chemistry) governing growth and form in biological systems.

More modernly, the term "self-organizing" seems to have been introduced in 1947 by psychiatrist and engineer, W. Ross Ashby. Self-organization as a word and concept was used by those associated with general systems theory in the 1960s, but was really taken up by physicists and people working on complex systems in the 1970s and 1980s, which is when it become much more widely used in the literature. (When queried with the keyword self-organ*, Dissertation Abstracts finds nothing before 1954, and only four total before 1970. There were 17 in the years 1971--1980; 126 in 1981--1990; and 593 in 1991--2000.)


The following list expands on the self-organization found in different disciplines. As the list grows, it becomes increasingly difficult to determine whether these phenomena are all fundamentally the same process, or the same label applied to several different processes. Self-organization, despite its intuitive simplicity as a concept, has proven notoriously difficult to define and pin down formally or mathematically.

It should also be noted that, the farther a phenomenon is removed from physics, the more controversial the idea of self-organization as understood by physicists becomes. Also, even when self-organization is clearly present, attempts at explaining it through physics or statistics are usually criticized as reductionistic. See holism, reductionism, emergence.

Similarly, when ideas about self-organization originate in, say, biology or social science, the farther one tries to take the concept into chemistry, physics or mathematics, the more resistance is encountered, usually on the grounds that it implies direction in fundamental physical processes. See teleology.

Self-organization in physics

There are several broad classes of physical processes that can be described as self-organization. Such examples from physics include:

  1. structural (order-disorder, first-order) phase transitions, such as
    1. spontaneous magnetization, crystallization (see crystal growth, and liquid crystal, in the classical domain and
    2. the laser, superconductivity and Bose-Einstein condensation, in the quantum domain (but with macroscopic manifestations).
  2. stationary thermodynamic systems away from equilibrium. The theory of dissipative structures was developed to unify the understanding of these phenomena, which include
    1. turbulence and convection (e.g., Bénard cells) in fluid dynamics,
    2. structure formation in astrophysics and cosmology (including star formation, galaxy formation)
    3. reaction-diffusion systems, such as oscillating chemical reactions.
  3. second-order phase transitions, associated with "critical points" at which the system exhibits scale-invariant structures (see fractal). Examples of these include:
    1. critical opalescence of fluids at the critical point
    2. percolation in random media
  4. self-organizing dynamical systems: complex systems made up of small, simple units connected to each other usually exhibit self-organization.
    1. The theory of self-organized criticality (SOC) claims that whenever such a system is open or dissipative, it exhibits critical (scale-invariant) behaviour similar to the static systems associated with second-order phase transitions.
    2. Examples include avalanches, earthquakes, forest fires, traffic jams, blackoutss in electric networks, size of cities, size of companies, mass extinctions. The theory of SOC has been more or less successfully applied to at least these systems.
    3. This is related to the self-organization of cellular automata.

It is sometimes debated whether static systems deserve the label of "self-organizing".

Self-organization vs. entropy

The idea of self-organization challenges the earlier, doctrine of ever-decreasing order which was based on philosophical generalization from the second law of thermodynamics. However, at the microscopic level, the two need not be in contradiction: it is possible for a closed system to gain macroscopic order whilst increasing its overall entropy, or for a system to reduce its entropy by interacting with external systems. More technically, some the system's degrees of freedom can become more ordered, even as the overall entropy increases. In many cases of biological self-assembly, for instance, the increasing organization of large molecules is more than compensated for by the increasing entropy of small molecules, especially water.

Since isolated systems cannot decrease their entropy, only open systems can exhibit self-organization. It is the flow of matter and energy through the system that allows the system to self-organize, and to exchange entropy with the environment. This is the basis of the theory of dissipative systems. Also, self-organization can only occur far away from thermodynamic equilibrium.

Self-organization in chemistry

Self-organization in chemistry includes:

  1. self-assembly
  2. reaction-diffusion systems and oscillating chemical reactions
  3. autocatalytic networks (see: autocatalytic set)

Self-organization in biology

The following is an incomplete list of the diverse phenomena which have been described as "self-organizing" in biology.

  1. formation of lipid bilayer membranes,
  2. homeostasis (the self-maintaining nature of systems from the cell to the whole organism)
  3. the creation of structures by social animals, such as social insects (bees, ants, termites), and many mammals
  4. morphogenesis, or how the living organism develops and grows. See also embryology.
  5. flocking behaviour (such as the formation of flocks by birds, schools of fish, etc.)
  6. The origin of life itself from self-organizing chemical systems, in the theories of hypercycles and autocatalytic networks.

Self-organization in mathematics and computer science

As mentioned above, phenomenon from mathematics and computer science such as cellular automata, random graphs, and some instances of evolutionary computation and artificial life exhibit features of self-organization.

In particular the theory of random graphs has been used as a justification for self-organization as a general principle of complex systems.

Self-organization in human society

The self-organizing behaviour of social animals and the self-organization of simple mathematical structures both suggest that self-organization should be expected in human society. Tell-tale signs of self-organization are usually statistical properties shared with self-organizing physical systems (see Zipf's law, power law, Pareto principle).

Examples abound in sociology, economics and anthropology.

In collective intelligence

Non-thermodynamic concepts of entropy and self-organization have been explored by many theorists. Cliff Joslyn and colleagues and their so-called "global brain" projects, and Marvin Minsky's "Society of Mind" idea, are examples of applications of these principles - see collective intelligence.

Donella Meadows, who codified twelve leverage points that a self-organizing system could exploit to organize itself, was one of a school of theorists who saw human creativity as part of a general process of adapting human lifeways to the planet and taking humans out of conflict with natural processes. See Gaia philosophy, deep ecology, ecology movement and Green movement for similar self-organizing ideals.

References and links

See also



In alphabetical order

Technical works

In chronological order

External links

Sources used in article