Full Idea
Most theorists agree that possible worlds semantics cannot provide an analysis of modal concepts which is an eliminative reduction, but it can still provide an explanation of the meanings of modal expressions.
Gist of Idea
Possible world semantics may not reduce modality, but it can explain it
Source
Robert C. Stalnaker (Mere Possibilities [2012], 2.2)
Book Reference
Stalnaker,Robert C.: 'Mere Possibilities' [Princeton 2012], p.30
A Reaction
Stalnaker cites Kit Fine for the view that there is no reduction of modality, which Fine takes to be primitive. Stalnaker defends the semantics, while denying the reduction which Lewis thought possible.