There exists a superintuitionistic propositional logic where $\neg p \vee \neg \neg p$ is a theorem, but $p \vee \neg p$ is not a theorem. It is called the logic of the weak excluded middle. That raises the question, is there a superintuitionistic propositional logic where $\neg \neg p \vee \neg \neg \neg p$ is a theorem, but $\neg p \vee \neg \neg p$ is not a theorem? Of course, the question can be generalized by adding more negation signs.
2026-03-26 13:57:17.1774533437
Logic of the even weaker excluded middle
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No - perhaps surprisingly, intuitionistic logic does prove triple negation elimination $$\neg\neg\neg p\equiv \neg p.$$ So this collapses the "LEM-hierarchy" right at the second level.