I am working on a side-project to understand game theory where the utility functions can change, using modal logic. In the course of doing this, I came up against the question: is there any use for a modality that takes two arguments? Modal logic is a logic with an operator of type Prop → Prop. There are, of course, many modal logics that take an additional argument; for example, the epistemic modalities are used to describe when various agents know various things, and usually are given as ...
