obversion

[ob-vur-zhuh n, -shuh n]
noun
  1. an act or instance of obverting.
  2. something that is obverted.
  3. Logic. a form of inference in which a negative proposition is obtained from an affirmative, or vice versa, as “None of us is immortal” is obtained by obversion from “All of us are mortal.”

Origin of obversion

1840–50; < Late Latin obversiōn- (stem of obversiō) a turning toward, equivalent to obvers(us) (see obverse) + -iōn- -ion
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for obversion

Historical Examples of obversion