obversion

[ ob-vur-zhuh n, -shuh n ]
/ ɒbˈvɜr ʒən, -ʃən /

noun

an act or instance of obverting.
something that is obverted.
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. 2019

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