Full Idea
The context-sensitivity of 'knows' is a function of contextual restrictions on the domain of quantification.
Gist of Idea
Knowing is context-sensitive because the domain of quantification varies
Source
report of David Lewis (Elusive Knowledge [1996]) by Stewart Cohen - Contextualism Defended p.68
Book Reference
'Contemporary Debates in Epistemology', ed/tr. Steup,M/Sosa,E [Blackwell 2005], p.68
A Reaction
I think the shifting 'domain of quantification' is one of the most interesting features of ordinary talk. Or, more plainly. 'what are you actually talking about?' is the key question in any fruitful dialogue. Sophisticated speakers tacitly shift domain.