1. Quantified modal logic of necessity because it collapses if essence is withdrawn. 2. These can be made precise using epistemic modal logic ; see for details. 3. Kripke has made influential and original contributions to logic, especially modal logic . 4. Lewis'own development of multiple modal logics is a case in point. 5. Monadic Boolean algebras also have an important connection to modal logic . 6. For example, Modal logic has undergone a major development that also modifies rhetoric. 7. Which precisely captures the semantics of two boxes in modal logic . 8. Van Benthem is known for his research in the area of modal logic . 9. The prerequisite for understanding modal logic is first order ( symbolic ) logic. 10. For example, they have been developed for quantificational and modal logics as well.