A holon (Greek: holos, "whole") is something that is simultaneously a whole and a part. The word was coined by Arthur Koestler in his book The Ghost in the Machine (1967, p. 48). Koestler was compelled by two observations in proposing the notion of the holon. The first observation was influenced by Nobel Prize winner Herbert Simon's parable of the two watchmakers, wherein Simon concludes that complex systems will evolve from simple systems much more rapidly if there are stable intermediate forms present in that evolutionary process than if they are not present. The second observation was made by Koestler himself in his analysis of hierarchies and stable intermediate forms in both living organisms and social organizations. He concluded that, although it is easy to identify sub-wholes or parts, wholes and parts in an absolute sense do not exist anywhere. Koestler proposed the word holon to describe the hybrid nature of sub-wholes and parts within in vivo systems. From this perspective, holons exist simultaneously as self-contained wholes in relation to their sub-ordinate parts, and dependent parts when considered from the inverse direction.
Koestler also points out that holons are autonomous, self-reliant units that possess a degree of independence and handle contingencies without asking higher authorities for instructions. These holons are also simultaneously subject to control from one or more of these higher authorities. The first property ensures that holons are stable forms that are able to withstand disturbances, while the latter property signifies that they are intermediate forms, providing a context for the proper functionality for the larger whole.
Finally, Koestler defines a holarchy as a hierarchy of self-regulating holons that function first as autonomous wholes in supra-ordination to their parts, secondly as dependent parts in sub- ordination to controls on higher levels, and thirdly in coordination with their local environment.
A holon is a system (or phenomenon) which is an evolving self-organizing dissipative structure, composed of other holons, whose structures exist at a balance point between chaos and order. It is maintained by the throughput of matter-energy and information-entropy connected to other holons and is simultaneously a whole in and itself at the same time being nested within another holon and so is a part of something much larger than itself. Holons range in size from the smallest subatomic particles and strings, all the way up to the multiverse, comprising many universes. Individual humans, their societies and their cultures are intermediate level holons, created by the interaction of forces working upon us both top-down and bottom-up. On a non-physical level, words, ideas, sounds, emotions—everything that can be identified—is simultaneously part of something, and can be viewed as having parts of its own, similar to sign in regard of semiotics.
Since a holon is embedded in larger wholes, it is influenced by and influences these larger wholes. And since a holon also contains subsystems, or parts, it is similarly influenced by and influences these parts. Information flows bidirectionally between smaller and larger systems as well as rhizomatic contagion. When this bidirectionality of information flow and understanding of role is compromised, for whatever reason, the system begins to break down: wholes no longer recognize their dependence on their subsidiary parts, and parts no longer recognize the organizing authority of the wholes. Cancer may be understood as such a breakdown in the biological realm.
A hierarchy of holons is called a holarchy. The holarchic model can be seen as an attempt to modify and modernise perceptions of natural hierarchy.
Ken Wilber comments that the test of holon hierarchy (e.g. holarchy) is that if a type of holon is removed from existence, then all other holons of which it formed a part must necessarily cease to exist too. Thus an atom is of a lower standing in the hierarchy than a molecule, because if you removed all molecules, atoms could still exist, whereas if you removed all atoms, molecules, in a strict sense would cease to exist. Wilber's concept is known as the doctrine of the fundamental and the significant. A hydrogen atom is more fundamental than an ant, but an ant is more significant.
The doctrine of the fundamental and the significant are contrasted by the radical rhizome oriented pragmatics of Deleuze and Guattari, and other continental philosophy.
Types of holons
An individual holon possesses a dominant monad; that is, it possesses a definable "I-ness". An individual holon is discrete, self-contained, and also demonstrates the quality of agency, or self-directed behavior. The individual holon, although a discrete and self-contained is made up of parts; in the case of a human, examples of these parts would include the heart, lungs, liver, brain, spleen, etc. When a human exercises agency, taking a step to the left, for example, the entire holon, including the constituent parts, moves together as one unit.
A social holon does not possess a dominant monad; it possesses only a definable "we-ness", as it is a collective made up of individual holons. In addition, rather than possessing discrete agency, a social holon possesses what is defined as nexus agency. An illustration of nexus agency is best described by a flock of geese. Each goose is an individual holon, the flock makes up a social holon. Although the flock moves as one unit when flying, and it is "directed" by the choices of the lead goose, the flock itself is not mandated to follow that lead goose. Another way to consider this would be collective activity that has the potential for independent internal activity at any given moment.
The concept of the holon is used in environmental philosophy, ecology and human ecology. Ecosystems are often seen as holons within one or many holarchies. Holons are seen as open subsystems of systems of higher order, with a continuum from the cell to the ecosphere.
Philosophy of history
In the philosophy of history, a holon is a historical event that makes other historical events inevitable. A holon is a controversial concept, in that some reject the inevitability of any historical event. A special category of holon is technology, which implies a perspective on how technologies have the potential to dictate history.
Psychology and Human Development
Holonics is a generic term in psychology that refers specifically to the theory of spiral dynamics. In this context it refers to the development of cultural value systems which are discrete in themselves (memes) and also part of a larger value system ("memeplex"). A simple characterisation which is familiar to some is Maslow's hierarchy of needs in which a basic value system is "I must eat", which once satisfied remains, but is added to with "I want friends".