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|Necessity de re||Berka I 145
Def need / necessary / Tarski / Lukasiewicz: NMNp = NCpNp - "it is necessary that p" means "it is not true that if p, then not-p." We can claim of a statement "a" that it is necessary iff its own negation is not included in it.
Logic, Semantics, Metamathematics: Papers from 1923-38 Indianapolis 1983
K. Berka/L. Kreiser
Logik Texte Berlin 1983