An archaic type of mathematical proposition whose historical purpose is not entirely known. In modern usage, the term "porism" is used instead of "theorem" for a small number of results for historical reasons.

See also Axiom, Lemma, Postulate, Poncelet's Porism, Principle, Steiner's Porism, Theorem

Po"rism (?), n. [Gr. a thing procured, a deduction from a demonstration, fr. to bring, provide: cf. F. porisme.]

1. Geom.

A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of innumerable solutions.

Playfair.

2. Gr. Geom.

A corollary.

Brande & C.

Three books of porisms of Euclid have been lost, but several attempts to determine the nature of these propositions and to restore them have been made by modern geometers.

 

© Webster 1913.