Full Idea
Imagination can be made to look cognitively worthless. Once we recall its fallible but vital role in evaluating counterfactual conditionals, we should be more open to the idea that it plays such a role in evaluating claims of possibility and necessity.
Gist of Idea
Imagination is important, in evaluating possibility and necessity, via counterfactuals
Source
Timothy Williamson (Modal Logic within Counterfactual Logic [2010], 6)
Book Reference
'Modality', ed/tr. Hale,B/Hoffman,A [OUP 2010], p.96
A Reaction
I take this to be a really important idea, because it establishes the importance of imagination within the formal framework of modern analytic philosopher (rather than in the whimsy of poets and dreamers).