A speaker of (1) implies that she is uncertain whether (2), making this use of might “epistemic.” On the received view, the implication is semantic, but in this dissertation I argue that this implication is no more semantic than is the implication that a speaker of (2) believes John to be contagious.

(1) John might be contagious.

(2) John is contagious.

This follows from a new observation: unlike claims with explicitly epistemic locutions, those made with “epistemic” uses of might can be explained only with reference to non-epistemic facts. I conclude that they express a relation, not to relevant information, but instead to relevant circumstances, and that uncertainty is implied only because of how informed speakers contribute to conversations. This conclusion dissolves old puzzles about disagreements and reported beliefs involving propositions expressed with might, puzzles that have been hard for the received view to accommodate. The cost of these advantages is to explain why the circumstantial modality expressed by might is not inherently oriented towards the future, as has been claimed for other circumstantial modalities. But this claim turns out to be false. The correct characterization of the temporal differences reveals that the modality expressed by might relates to propositions whereas other modalities relate to events. Neither sort is epistemic.