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Full Idea
One reason for wanting a three-valued logic is to act as a basis of a theory of presupposition.
Gist of Idea
Three-valued logic is useful for a theory of presupposition
Source
Edwin D. Mares (Negation [2014], 3.1)
Book Ref
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.185
A Reaction
[He cites Strawson 1950] The point is that you can get a result when the presupposition does not apply, as in talk of the 'present King of France'.
| 8942 | Lukasiewicz's L3 logic has three truth-values, T, F and I (for 'indeterminate') [Lukasiewicz, by Fisher] |
| 14263 | Strong Kleene disjunction just needs one true disjunct; Weak needs the other to have some value [Fine,K] |
| 21602 | Many-valued logics don't solve vagueness; its presence at the meta-level is ignored [Williamson] |
| 18787 | Three-valued logic is useful for a theory of presupposition [Mares] |
| 8943 | Three-valued logic says excluded middle and non-contradition are not tautologies [Fisher] |
| 16335 | In Strong Kleene logic a disjunction just needs one disjunct to be true [Halbach] |
| 16334 | In Weak Kleene logic there are 'gaps', neither true nor false if one component lacks a truth value [Halbach] |