[Mathematics, Psychology] (1) [mathematics] Every doctrine, either true or false, excludes other possibilities when, in fact, the determination of whether a doctrine is true or false is not yet able to be determined. The excluded third represents other possibilities. If a given interval contains an unlimited sequence of numbers, we can find within the interval at least one arbitrarily small interval containing an unlimited sequence of numbers from the primary sequence. This presupposes that we know whether a sub-interval, contains a limited or unlimited sequence of numbers from the primary sequence. (2) [psychology] Since people, tasks, and organizational environment vary, techniques of supervision will be most effective if appropriately varied." (3) [psychology] The formation of constitutive functions, and the nature of constituted formations are difficult to specify, and this requires incite to make studies of the organizing factors of a system situated in its environment. Reconsideration of the nature of complex clinical strata (mixed states, atypical forms, schizophrenia) provides a better realization of the effect of the psychotherapies, and a better understanding of the integrated role of the diverse tools of knowledge. Serves as a general explanation of the possible effect of ago-antagonistic actions, and to show that the function of a system cannot be reduced to the sum of the diverse functional invariants. also known as the Principle of Excluded Middle
(1) Billing, J. (1949) The principle of the excluded third and the Bolzano-Weierstrass lemma. Arkiv för Matematik. 1(1), 59
(2) Koontz, H. and O’Donnell, C. (1968), Principles of Management, 4th ed., McGraw-Hill.
(3) Marchais, P. (2005), D'un concept opératoire controversé: Le tiers-inclus, opérateur d'intégration. Annales Médico-Psychologiques. 163(1),58-64.