Coherence

The problem remains to define what "coherence" precisely means: mere consistency is clearly not sufficient, since any collection of unrelated facts is logically consistent. In addition, coherence requires connection and mutual support of the different beliefs. Since learning is based on the strengthening of associations, ideas that do not connect to existing knowledge simply cannot be learnt. Connection means some kind of a semantic or associative relationship, so that information about one idea also gives you some information about the other. An idea can furthermore support another idea by providing an explanation, evidence or arguments why the latter idea should be true. The preference for consistency can be motivated by the theory of cognitive dissonance, which states that people tend to reject ideas that contradict what they already believe. More generally, it follows from the fact that a fit individual must be able to make clear-cut decisions. Mutually contradictory rules will create a situation of confusion or hesitation, which is likely to diminish the chances for survival.

Coherence as a criterion of truth is emphasized by the epistemology of constructivism, which is espoused by most cyberneticists, and emphasized in "second-order" cybernetics (von Foerster, 1996) and the theory of autopoiesis (Maturana & Varela, 1992). According to this philosophy, knowledge is not a passive mapping of outside objects (the reflection-correspondence view), but an active construction by the subject. That construction is not supposed to reflect an objective reality, but to help the subject adapt or "fit in" to the world which it subjectively experiences.

This means that the subject will try to build models which are coherent with the models which it already possesses, or which it receives through the senses or through communication with others. Since models are only compared with other models, the lack of access to exterior reality no longer constitutes an obstacle to further development. In such an epistemology, knowledge is not justified or "true" because of its correspondence with an outside reality, but because of its coherence with other pieces of knowledge (Rescher, 1973; Thagard, 1989).

References:

• Maturana H. R., & Varela F. J. (1992). The Tree of Knowledge: The Biological Roots of Understanding, (rev. ed.), (Shambhala, Boston).
• Rescher N. (1973) The Coherence Theory of Truth, London, Oxford University Press.
• Thagard, P. (1989) Explanatory Coherence. Behavioral and Brain Sciences 12: 435-467.
• von Foerster H. (1996) Cybernetics of Cybernetics (2nd edition). (Future Systems, Minneapolis)