Regular modal logic

In modal logic, a '''regular modal logic''' is a modal logic containing (as axiom or theorem) the duality of the modal operators:

<math>\Diamond A \leftrightarrow \lnot\Box\lnot A</math>

and closed under the rule

<math>\frac{(A\land B)\to C}{(\Box A\land\Box B)\to\Box C}.</math>

Every normal modal logic is regular, and every regular modal logic is classical.

== References == *Chellas, Brian. ''Modal Logic: An Introduction''. Cambridge University Press, 1980.

Category:Logic Category:Modal logic

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