In truth-functional propositional logic, any proposition that is neither a tautology nor a contradiction, i.e. neither inherently true or inherently false. Hence it is any proposition that is sometimes true and sometimes false, depending on its interpretation.

For example A and B is a contingency. It can be true or false depending on the values of A and B.

Contingency (the primary control on the nature of systematic change)

In the context of systems theory, contingency is the process by which once a feature has developed, it becomes more likely for a system to adapt this feature or produce a secondary adaptation than it is to replace it through innovation. In simple terms this means that change acts upon what is already there. This simple (in fact absolutely obvious) rule of process behavior can be applied to aid in modeling or interpreting any form of systematic change, and therefore everything from sports rules to the development of legal systems.

Biological evolution is the most extensively studied form of systematic change (with the possible exception of Economic change), and is the field where these processes were first modeled. Stephen Jay Gould has discussed these processes extensively, his classic example is the pentadactile limb; all complex vertebrates that developed from amphibians have five fingered/toed limbs. Five is not optimum, it is simply that once this trend had developed it gained genetic inertia. Thus in the case of the panda, where a developing a sixth finger was desireable, an extra finger was developed from a bone within the hand. Pandas are therefore pentadactile plus rather than truly hexadactile.

However, biological evolution is extremely specific, and governed by the processes of speciation and sexual reproduction that do not affect systematic change in a sociological context. The keyboard you are sitting at to read this node is a perfect example of technological contingency and was also discussed by Gould. The QWERTY layout of keys is far from optimal, and was initially developed in the 19th century for specific reasons relating to the development of a functional mechanical typewriter. In a mechanical typewriter, where the keyboard did not face the paper, this layout was chosen to slow typists down. Once this adaptation was accepted and commonly used it gained developmental inertia (incumbancy). This prevented new, designed letter layouts from becoming established and followed onto computers where no such layout was necessary or sensible.

Contingency can therefore be used to interpret most forms of change, and it is enlightening to think in terms of what effects this has. Because of contingency, all changing systems tend towards increasing complexity. In the case of soccer rules, the offside rule becomes ever more complicated in order to accommodate changes in the game rather than more fundamental changes in the nature of the pitch (such as changing the size of the goal mouth). Or in the case of the legal system, each new case with a subtly different situation serves to act as a precedent, clarifying the terms of the law with contingencies. Or the (bizarre) Imperial system of weights and measures derived from day to day terms in the Medieval period and results in modern children learning their twelve times table. A further fact of contingency is that change tends to act on pre-existing features producing a completely new adaptation rather than innovating without raw material. For example, insect wings are believed to have developed from cooling fins. When insects increased in size due to a change in the oxygen levels of the atmosphere the aerodynamic potential of these fins allowed them to be used for aviation. It is because of this process that adaptionist-style interpretations of biological processes make little sense without the historical context: The question “why did evolution give us two nipples?” is meaningless unless you think of the contingency of fetal development.

If we accept contingency as a process then all changes tend towards increasing complexity, and that within any system you can never go back without initating revolutionary change; there will never be a true revolution because we’re stuck with the adaptations we already have.

Con*tin"gen*cy (?), n,; pl. Contingencies (#). [Cf. F. contingence.]


Union or connection; the state of touching or contact.

"Point of contingency."

J. Gregory.


The quality or state of being contingent or casual; the possibility of coming to pass.

Aristotle says we are not to build certain rules on the contingency of human actions. South.


An event which may or may not occur; that which is possible or probable; a fortuitous event; a chance.

The remarkable position of the queen rendering her death a most important contingency. Hallam.


An adjunct or accessory.


5. Law

A certain possible event that may or may not happen, by which, when happening, some particular title may be affected.

Syn. -- Casualty; accident; chance.


© Webster 1913.

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