 The Analysis of Intensions. Lewis's possible world truth conditions are expressed in classical non-modal logic and, hence, they are to be interpreted by means of standard Tarskian semantics.  Thus, n-place predicates π are assigned extensions Eπ — in particular, for 1-place predicates, sets of individuals — as their semantic values, as described in the exposition in §1.2 above. However, given worldboundedness and the fact that predicate extensions are drawn not simply from the actual world but from all possible worlds, these extensions are able to serve as intensions in Lewis's theory. As in basic possible world semantics, intensional entities in general can be defined in terms of the basic ontology of the theory independent of the linguistic roles they can play as the intensions of predicates. And because individuals are worldbound, Lewis is able to simplify the definitions given in §1.3 by defining intensions as sets rather than functions: 