The paper investigates 3-valued logics, where the truth values “true” and “insignificant” are distinguished, the latter value being a neutral element both for conjunction and disjunction. The obtained logic system is called stable logic since it is stable against loosing or missing information. Relationships to other non-classical logics are outlined: Bočvar logic, relevant logics, Hałkowska’s nonsense logic, Girard’s linear logic. Sequent calculi are defined for stable logic, their soundness and completeness being investigated. The corresponding algebraic framework is defined.
Reviewer: N.Curteanu (Iaşi)