 In the interpretation of modal discourse recourse is often made to the idea of “identity across possible worlds”. If modal discourse is interpreted in this way it becomes natural to regard a statement ascribing a modal property to an individual as asserting the identity of that individual across worlds: “Sarah might have been a millionaire”, on this view, asserts that there is a possible world in which an individual identical with Sarah is a millionaire. “Sarah could not have been a millionaire” asserts that in any world in which an individual identical with Sarah exists that individual is not a millionaire.