Full Idea
Any notion of necessity must carry with it a corresponding notion of impossibility, …but it can make a difference which one of them presents itself first and more naturally.
Gist of Idea
Necessity implies possibility, but in experience it matters which comes first
Source
Bernard Williams (Practical Necessity [1982], p.127)
Book Reference
Williams,Bernard: 'Moral Luck: Papers 1973-1980' [CUP 1981], p.127
A Reaction
I like this because it connects modality with experience, rather than with formal logic. It seems right that in life we immediately see either a necessity or an impossibility, and inferring the other case is an afterthought.