Full Idea
In the world theory, what passes for 'necessity' is just a bunch of parallel 'contingencies'. The theory provides no basis for understanding why these contingencies repeat unremittingly across the board (while others do not).
Gist of Idea
Possible worlds just give parallel contingencies, with no explanation at all of necessity
Source
Michael Jubien (Analyzing Modality [2007], 1)
Book Reference
'Oxford Studies in Metaphysics vol.3', ed/tr. Zimmerman,Dean W. [OUP 2007], p.105