Philosophy Lexicon of Arguments

Multi-valued logic: a logic that assumes more than the two classical truth values true and false. There are trivalent logics with possibility or indeterminacy as a third value. For tetravalent logics there are e.g. ¼ or ¾ as additional values that introduce a gradation in the rating. In the case of infinite-valued logics, the truth values can be interpreted as probability values.
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I 195
Multi-valued Logic / Geach: There is often a truth value X, that both p and ~ p have - problem: Then also p.~ p has the value X: (simultaneous assertion of p and ~ p) correctly: "it is just as likely that it will rain tomorrow, as it is likely that will not rain tomorrow"- but "it’s raining" and "it is not raining" can not have the same truth value, because then "it’s raining and it’s not raining" also has the same truth value - because the latter must be f.

Gea I
P.T. Geach
Logic Matters Oxford 1972

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Ed. Martin Schulz, access date 2017-05-28