Definitions for obversionɒbˈvɜr ʒən, -ʃən
This page provides all possible meanings and translations of the word obversion
Random House Webster's College Dictionary
ob•ver•sionɒbˈvɜr ʒən, -ʃən(n.)
an act or instance of obverting.
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; < LL
the act of turning toward or downward
the act of immediate inference, by which we deny the opposite of anything which has been affirmed; as, all men are mortal; then, by obversion, no men are immortal. This is also described as "immediate inference by privative conception."
In traditional logic, obversion is a "type of immediate inference in which from a given proposition another proposition is inferred whose subject is the same as the original subject, whose predicate is the contradictory of the original predicate, and whose quality is affirmative if the original proposition's quality was negative and vice versa". The quality of the inferred categorical proposition is changed but the truth value is equivalent to the original proposition. The immediately inferred proposition is termed the "obverse" of the original proposition, and is a valid form of inference for all types of categorical propositions. In a universal affirmative and a universal negative proposition the subject term and the predicate term are both replaced by their complements: The universal affirmative is obverted to a universal negative. The universal negative is obverted to a universal affirmative. In the particular affirmative the quantity of the subject term remains unchanged, but the predicate term of the inferred proposition negates the complement of the predicate term of the original proposition. The particular affirmative is obverted to a particular negative.
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