Full Idea
I identify propositions with certain properties - namely, with those that are instantiated only by entire possible worlds. Then if properties generally are the sets of their instances, a proposition is a set of possible worlds.
Gist of Idea
A proposition is a set of entire possible worlds which instantiate a particular property
Source
David Lewis (On the Plurality of Worlds [1986], 1.5)
Book Reference
Lewis,David: 'On the Plurality of Worlds' [Blackwell 2001], p.53
A Reaction
I don't get this. How can the proposition that tomatoes are edible be an entire set of possible worlds? The proposition seems to be about tomatoes, and nothing else. Should we talk of 'possibilities', rather than of 'possible worlds'?