Full Idea
The need to add a note of necessity to 'all black crows are black' could be met by a generalisation over classes (what belongs to sets x and y belongs to y), or maybe be quantifying over possible particulars.
Gist of Idea
Necessity could be just generalisation over classes, or (maybe) quantifying over possibilia
Source
Willard Quine (On Multiplying Entities [1974], p.262)
Book Reference
Quine,Willard: 'Ways of Paradox and other essays' [Harvard 1976], p.262
A Reaction
He dislikes the second strategy because 'unactualized particulars are an obscure and troublesome lot'. The second is the strategy of Lewis. I think necessity starts to creep back in as soon as you ask WHY a generalisation holds true.