Full Idea
It is not reduction (of modality) but regimentation that the possible-worlds framework provides - a procedure for representing modal discourse, using primitive modal notions, in a way that helps reveal its structure.
Gist of Idea
Possible worlds don't reduce modality, they regiment it to reveal its structure
Source
Robert C. Stalnaker (Mere Possibilities [2012], 1.2)
Book Reference
Stalnaker,Robert C.: 'Mere Possibilities' [Princeton 2012], p.11
A Reaction
I think this is exactly my view. All discussion of the ontology of possible worlds is irrelevant. They no more exist than variables in logic exist. They're good when they clarify, but dubious when they over-simplify.
Related Ideas
Idea 16438 Necessity and possibility are fundamental, and there can be no reductive analysis of them [Stalnaker]
Idea 16445 I think of worlds as cells (rather than points) in logical space [Stalnaker]