Circumstantial and Temporal Dependence in Counterfactual Modals

“Counterfactual” readings of might/could have were previously analyzed using metaphysical modal bases. This paper presents examples and scenarios where the assumptions of such a branching-time semantics are not met, because there are facts at the base world and time which exclude the complement of the modal being true or becoming true. Additional arguments show that counterfactual readings are context-dependent. These data motivate an analysis using a circumstantial (or factual) modal base, which refers to a contextdependent set of facts about the base world and time. The semantics is formulated in a version of the premise semantics for modality.