Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun The process of obverting or the condition so resulting.
- noun Logic Inference of the obverse of a proposition.
from The Century Dictionary.
- noun The act of obverting or turning toward some person or thing, or toward a position regarded as the front.
- noun In logic, same as
conversion , or the transposition of the subject and predicate of a proposition. - noun In logic:
- noun The taking of the contranominal of the inverse.
from the GNU version of the Collaborative International Dictionary of English.
- noun The act of turning toward or downward.
- noun (Logic) The act of immediate inference, by which we deny the opposite of anything which has been affirmed. This is also described as “immediate inference by privative conception.”
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun The act of turning
toward ordownward . - noun logic An
immediate inference that denies theopposite of something previouslyaffirmed .
Etymologies
from Wiktionary, Creative Commons Attribution/Share-Alike License
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Examples
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These are the theory of the syllogism and the doctrines of contraposition and obversion.
The Traditional Square of Opposition Parsons, Terence 2006
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It turns out that Strawson's revision of truth conditions does preserve the principles of SQUARE (these can easily be checked by cases), [27] but not the additional conversion principles of [SQUARE], and also not the traditional principles of contraposition or obversion.
The Traditional Square of Opposition Parsons, Terence 2006
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A similar thing happened with the principle of obversion.
The Traditional Square of Opposition Parsons, Terence 2006
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Hence, since _The sky is blue_ becomes by obversion, _The sky is not not-blue_, we may also infer _The sky is not red_, etc.
Logic Deductive and Inductive Carveth Read 1889
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Similarly, _No men are wise_, being by obversion equivalent to _All men are not-wise_, is incompatible with _Some men are wise_, by the same principle of Contradiction.
Logic Deductive and Inductive Carveth Read 1889
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Excluded Middle, 'not-wise' is to be affirmed; and _Some men are not-wise_, is by obversion equivalent to _Some men are not wise_.
Logic Deductive and Inductive Carveth Read 1889
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If it be true that _All men are wise_, it is false that _Some men are not wise_ (equivalent by obversion to _Some men are not-wise_); or else, since the 'Some men' are included in the
Logic Deductive and Inductive Carveth Read 1889
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Similarly, if it be false that _No men are wise_, which by obversion is equivalent to _All men are not-wise_, then it is true at least that
Logic Deductive and Inductive Carveth Read 1889
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Take any universal affirmative proposition; convert it by obversion
Logic Deductive and Inductive Carveth Read 1889
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Still, given any proposition in the form _A is either B or C_, we can state the propositions that give the sense of obversion, conversion, etc., thus:
Logic Deductive and Inductive Carveth Read 1889
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