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Mathematical Logic / Proof TheoryResearchAI-Generated

Does every intermediate logic between intuitionistic logic and classical logic admit a decidable axiomatization by a finite set of rule extensions of the implication-negation fragment?

Related: Visser's rules conjecture for intermediate logics, Ghilardi's theorem on projective unification, de Jongh and Gabriele Pulcini results on fragments of intermediate logics

The implication-negation fragment of intuitionistic logic captures reasoning about conditionals and negation without disjunction or conjunction. When one adds new inference rules to this fragment, one obtains a lattice of stronger systems sitting between pure intuitionistic logic and classical logic. The open problem is whether every such intermediate logic, when restricted to the implication-negation language, can be finitely and decidably axiomatized purely through rule extensions of this fragment, or whether there exist intermediate logics whose implication-negation fragments escape any such finite rule-based description.

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