# classical modal logic

> modal logic containing the duality axiom schema ◊A↔¬◻¬A as well as the deduction rule A↔B ⊢ ◻A↔◻B

**Wikidata**: [Q5128344](https://www.wikidata.org/wiki/Q5128344)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Classical_modal_logic)  
**Source**: https://4ort.xyz/entity/classical-modal-logic