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countable and uncountable, plural obversions
The act of turning toward or downward. examples
(logic) An immediate inference that denies the opposite of something previously affirmed. quotations examples
From 'warmth is agreeable' we can affirm, by formal obversion, 'warmth is not disagreeable, and not indifferent.' We cannot affirm, without an examination of the subject matter, 'cold is disagreeable.'
1870, Alexander Bain, Logic: Induction