Full Idea
Friends of metaphysical necessity would want to hold that when it is metaphysically necessary that p, there is no good sense of 'possible' (except, perhaps, an epistemic one) in which it is possible that not-p.
Clarification
'epistemic' possibility is possibility 'for all we know'
Gist of Idea
Metaphysical necessity says there is no possibility of falsehood
Source
Bob Hale (Absolute Necessities [1996], 2)
Book Reference
-: 'Philosophical Perspectives' [-], p.95
A Reaction
We might want to say which possible worlds this refers to (and presumably it won't just be in the actual world). The normal claim would refer to all possible worlds. Adding a '...provided that' clause moves it from absolute to relative necessity.