Full Idea
If 'Italy is a large country' lacks a truth value, then so too, presumably, does 'Italy is not a large country'. But 'Italy is or is not a large country' is true, on the supervaluationist account, because it is a truth of classical propositional logic.
Gist of Idea
If 'Italy is large' lacks truth, so must 'Italy is not large'; but classical logic says it's large or it isn't
Source
Leon Horsten (The Tarskian Turn [2011], 06.2)
Book Reference
Horsten,Leon: 'The Tarskian Turn' [MIT 2011], p.72
A Reaction
See also Idea 15363. He cites Fine 1975.
Related Idea
Idea 15363 In the supervaluationist account, disjunctions are not determined by their disjuncts [Horsten]