Antiperistasis

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Antiperistasis, in philosophy, is a general term for various processes, real or contrived, referring to the interaction of two opposite qualities, one whereof, by its opposition excites and heightens the force of the other. Historically, this explanation was applied to numerous phenomena, from the interaction of quick lime with cold water, to the origin of thunder and lightning.

This term is Greek, άντιπερίστασὶς, formed of άντί (contra, "against") and περίστασις ("standing around"); q.d. resistance against anything that surrounds or besets another. It was usually defined as, "the opposition of a contrary quality, whereby the quality it opposes becomes heightened, or intended; or the action whereby a body attacked by another, collects itself, and becomes stronger by such opposition; or an intension of the activity of one quality, by the opposition of another."

It was using this explanation that academic philosophers claimed that cold, on many occasions, increases a body's degree of heat, and dryness that of moisture. Thus, it was said, that quick lime (Ca O) was apparently set ablaze when doused with cold water. It was also the understood reason for why water, such as that in wells, was warmer in winter than in summer. And to the same cause was owed that thunder and lightning originate up in the sky, where it is continuously cold.

Peripatetic philosophers, those followers of Aristotle, made extensive use of the principle of antiperistasis. According to such authors, "'Tis necessary that Cold and Heat be both of them endued with a self-invigorating Power, which each may exert when surrounded by its contrary; and thereby prevent their mutual Destruction. Thus it is supposed that in Summer, the Cold expelled from the Earth and Water by the Sun's scorching Beams, retires to the middle Region of the Air, and there defends itself against the Heat of the superior and inferior. And thus, also, in Summer, when the Air is about us in sultry hot, we find that Cellars and Vaults have the opposite Quality: so in Winter, when the external Air freezes the Lakes and Rivers, the internal Air, in the same Vaults and Cellars, becomes the Sanctuary of Heat; and Water, fresh drawn out of deeper Wells and Springs, in a cold Season, not only feels warm, but manifestly smokes." Robert Boyle examined the doctrine thoroughy in his history of cold.

Other examples used by the patrons of antiperistasis included the aphoristical saying of Hippocrates, "the viscera are hottest in the winter"; and the production of hail in the upper atmosphere, believed to occur only in the summer due to the increased heat of the sun.