Full Idea
We need an explanation of what worlds are that makes clear why being true at all of them should be necessary and sufficient for being necessary (and true at one of them suffices for being possible).
Gist of Idea
What are these worlds, that being true in all of them makes something necessary?
Source
Bob Hale (Necessary Beings [2013], 03.3.2)
Book Reference
Hale,Bob: 'Necessary Beings' [OUP 2013], p.71
A Reaction
Hale is introducing combinatorial accounts of worlds, as one possible answer to this. Hale observes that all the worlds might be identical to our world. It is always assumed that the worlds are hugely varied. But maybe worlds are constrained.