Modal Logic: Study of reasoning about what must or might be the case, as well as what merely happens to be the case. The formalization of modal logic for the propositional calculus introduces special operators designating necessity and possibility (L and M). "It is necessary that p" (Lp) is interpreted to mean that p must be true in all possible worlds, and "It is possible that p" (Mp) that p is true in at least one possible world. On these interpretations,
Lp º ~M~p is tautologous.1
See also: Modal Logic: An Introduction by Brian F. Chellas
1. Philosophy Pages.
Lp º ~M~p is tautologous.1
See also: Modal Logic: An Introduction by Brian F. Chellas