  It would seem to be a simple matter to outfit a modal logic with the quantifiers \(\forall\) (all) and \(\exists\) (some). One would simply add the standard (or classical) rules for quantifiers to the principles of whichever propositional modal logic one chooses. However, adding quantifiers to modal logic involves a number of difficulties. Some of these are philosophical. For example, Quine (1953) has famously argued that quantifying into modal contexts is simply incoherent, a view that has spawned a gigantic literature. Quine’s complaints do not carry the weight they once did. See Barcan (1990) for a good summary, and note Kripke’s (2017) (written in the 60’s for a class with Quine) which provides a strong formal argument that there can be nothing wrong with “quantifying in”.