EntityQ210841· pop 40· linked from 394 articlesmodal logicSign in to saveformal logic able to express concepts such as necessity, possibility, provability, obligation, knowledge etc.Connectionsfirst-order logicEntityArthur PriorEntityphilosophyEntityaxiomEntityQ455Entitypropositional calculusEntityDe Morgan's lawsEntityDavid LewisEntitypossible worldEntitymany-valued logicEntityClarence Irving LewisEntitydualityEntitydeontic logicEntityepistemic modal logicEntitythree-state logicEntitysubjunctive possibilityEntitymethod of analytic tableauxEntityclosure operatorEntityStrict conditionalEntitydynamic logicEntityCategoriesLogicMathematical logicModal logicPhilosophical logicSemantics