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4. Formal Logic / E. Nonclassical Logics / 3. Many-Valued Logic

[logic using further values in addition to 'true' and 'false']

7 ideas
Lukasiewicz's L3 logic has three truth-values, T, F and I (for 'indeterminate') [Lukasiewicz, by Fisher]
Strong Kleene disjunction just needs one true disjunct; Weak needs the other to have some value [Fine,K]
Many-valued logics don't solve vagueness; its presence at the meta-level is ignored [Williamson]
Three-valued logic is useful for a theory of presupposition [Mares]
Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher]
In Strong Kleene logic a disjunction just needs one disjunct to be true [Halbach]
In Weak Kleene logic there are 'gaps', neither true nor false if one component lacks a truth value [Halbach]