  All the previously mentioned accounts of possible worlds are actualist in the sense that they take actual existence and existence simpliciter to coincide. One of the most developed nominalistic accounts of possible worlds, that of David Lewis, is not actualist but possibilist: according to Lewis to exist simpliciter is one thing and to be actual is another. For Lewis ‘actual’ is an indexical predicate so that from the point of view of each world only that world is actual and none of the others are. Thus, unlike Plantinga, Adams, and Stalnaker, Lewis does not take every possible world to exist actually.