Full Idea
The apparatus of possible worlds has (I hope) been very useful as far as the set-theoretic model-theory of quantified modal logic is concerned, but has encouraged philosophical pseudo-problems and misleading pictures.
Clarification
'Modal logic' involves possibility and necessity
Gist of Idea
Possible worlds are useful in set theory, but can be very misleading elsewhere
Source
Saul A. Kripke (Naming and Necessity notes and addenda [1972], note 15)
Book Reference
Kripke,Saul: 'Naming and Necessity' [Blackwell 1980], p.48
A Reaction
This is presumably a swipe at David Lewis, who claims possible worlds are real. The fact that the originator of possible worlds sees them as unproblematic doesn't mean they are. Fine if they are a game, but if they assert truth, they need a metaphysics.