Full Idea
The fundamental problem is that in world theory, what passes for necessity is in effect just a bunch of parallel 'contingencies'.
Gist of Idea
Possible worlds don't explain necessity, because they are a bunch of parallel contingencies
Source
Michael Jubien (Possibility [2009], 3.2)
Book Reference
Jubien,Michael: 'Possibility' [OUP 2009], p.75
A Reaction
Jubien's general complaint is that there is no connection between the possible worlds and the actual world, so they are irrelevant, but this is a nicely different point - that lots of contingent worlds can't add up to necessity. Nice.