Full Idea
The thesis that propositions are sets of possible worlds is one of the two leading accounts of the nature of propositions. The other leading account endorses structured propositions.
Gist of Idea
Propositions are standardly treated as possible worlds, or as structured
Source
Trenton Merricks (Propositions [2015], Intro)
Book Reference
Merricks,Trenton: 'Propositions' [OUP 2015], p.-3
A Reaction
Merricks sets out to reject both main views. I take the idea that propositions actually are sets of possible worlds to be ridiculous (though they may offer a way of modelling them). The idea that they have no structure at all strikes me as odd.