trichotomy (philosophy)

Important trichotomies discussed by Aquinas include the causal principles (agent, patient, act), the potencies for the intellect (imagination, cogitative power, and memory and reminiscence), and the acts of the intellect (concept, judgment, reasoning), with all of those rooted in Aristotle; also the transcendentals of being (unity, truth, goodness) and the requisites of the beautiful (wholeness, harmony, radiance).

Kant expounded a table of judgments involving four three-way alternatives, in regard to (1) Quantity, (2) Quality, (3) Relation, (4) Modality, and, based thereupon, a table of four categories, named by the terms just listed, and each with three subcategories. Kant also adapted the Thomistic acts of intellect in his trichotomy of higher cognition—(a) understanding, (b) judgment, (c) reason—which he correlated with his adaptation in the soul's capacities—(a) cognitive faculties, (b) feeling of pleasure or displeasure, and (c) faculty of desireKant, Immanuel, The Critique of Judgment, 2007 edition, Cosimo Classics, pp. 10-11.—of Tetens's trichotomy of feeling, understanding, and will.Teo, Thomas (2005), The critique of psychology: from Kant to postcolonial theory, p. 43. In his Logic (113) Kant notes that all "polytomy are empirical" and "cannot be taught in logic".Kant I., (1800), [https://books.google.com/books?id=PCxAAAAAIAAJ&q=trichotomy Logic] (Logik), tr. J. Richardson London, 1819, p.209. In preparation he states "A division into two members goes under the appelation of dichotomy; but it, when consisting of more than two, takes the name of poytomy".

Hegel held that a thing's or idea's internal contradiction leads in a dialectical process to a new synthesis that makes better sense of the contradiction. The process is sometimes described as thesis, antithesis, synthesis. It is instanced across a pattern of trichotomies (e.g. being-nothingness-becoming, immediate-mediate-concrete, abstract-negative-concrete); such trichotomies are not just three-way classificatory divisions; they involve trios of elements functionally interrelated in a process. They are often called triads (but 'triad' does not have that as a fixed sense in philosophy generally).

Charles Sanders Peirce built his philosophy on trichotomies and triadic relations and processes, and framed the "Reduction Thesis" that every predicate is essentially either monadic (quality), dyadic (relation of reaction or resistance), or triadic (representational relation), and never genuinely and irreducibly tetradic or larger.

• Balanced ternary
• Dichotomy
• Epistemological pluralism
• Rule of three (writing)
• Trilemma
• Trinity
• Tripartite motto

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Category:Classification systems

Category:3 (number)

§The list of trichotomies featuring different philosophers was initially influenced by Herb O. Buckland's List which was placed on the Wikipedia years ago but subsequently removed because a complaint was raised about credit not being given to the original author. The original list is here: https://www.threesology.org/3s-poster-5.php. Credit needs to be given where it is due.