Modal expressions—expressions like ‘must’ and ‘can’—figure importantly in our ability to think and talk about things that are non-actual: people who are not actual (e.g., ‘There could have been a Tom Collins’1), events that did not happen (e.g., ‘He could have been spreading rumors’), ways in which events that happen do not happen (e.g., ‘Rome could have been built in a day’), etc. These expres...