EntityQ840226· pop 9· linked from 40 articlesnormal modal logicSign in to saveset of modal formulas containing all propositional tautologies and all instances of the Kripke schema ◻(A→B)→(◻A→◻B) and closed under modus ponens and necessitationConnectionspartially ordered setEntitylogicEntityequivalence relationEntitytautologyEntitymodal logicEntitymodus ponensEntityClarence Irving LewisEntitypreorderEntitydeontic logicEntityupward directed setEntityepistemic modal logicEntityKripke semanticsEntityweak orderingEntityprovability logicEntityclassical modal logicEntityS5EntityCategoriesModal logic