obversion

[ ob-vur-zhuhn, -shuhn ]

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.”

Word History and Origins

Origin of obversion¹

1840–50; < Late Latin obversiōn- (stem of obversiō ) a turning toward, equivalent to obvers ( us ) ( obverse ) + -iōn- -ion

Example Sentences

Dr. Bain calls this Material Obversion because it cannot be practised safely without reference to the matter of the proposition.

From Project Gutenberg

In this it differs from Obversion, Conversion, and Contraposition, each of which stands for one process.

From Project Gutenberg

Define Obversion and Inversion, and apply these processes also to the above three propositions.

From Project Gutenberg

A further process, known as Contraposition or Conversion by Negation, consists of conversion following on obversion.

From Project Gutenberg