  Communication facilitates coordination, but coordination might fail if
there's too much uncertainty. I discuss a scenario in which vagueness-driven
uncertainty undermines the possibility of publicly sharing a belief. I then
show that asserting an epistemic modal sentence, 'Might p', can reveal the
speaker's uncertainty, and that this may improve the chances of coordination
despite the lack of a common epistemic ground. This provides a game-theoretic
rationale for epistemic modality. The account draws on a standard relational
semantics for epistemic modality, Stalnaker's theory of assertion as
informative update, and a Bayesian framework for reasoning under uncertainty.
