Porism

PO'RISM, n. [Gr. acquisition, to gain, a passing, to pass.]
In geometry, a name given by ancient geometers to two classes of propositions. Euclid gave this name to propositions involved in others which he was investigating, and obtained without a direct view to their discovery. These he called acquisitions, but such propositions are now called corollaries. A porism is defined, "a proposition affirming the possibility of finding such conditions as will render a certain problem indeterminate or capable of innumerable solutions." It is not a theorem, nor a problem, or rather it includes both. It asserts that a certain problem may become indeterminate, and so far it partakes of the nature of a theorem, and in seeking to discover the conditions by which this may be effected, it partakes of the nature of a problem.

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