 The discussion so far may suggest that whether the notion of transworld identity (that an object exists in more than one world) is problematic depends solely on whether one adopts an account of possible worlds as concrete entities such as Lewis’s (in which case it is) or an account of possible worlds as abstract entities such as Plantinga’s (in which case it is not). However, matters are not so simple, for a variety of reasons (to be discussed in Sections 3–5 below).