Full Idea
The supervaluationist view of vagueness is that 'tall' comes out true or false on all the ways in which we can make 'tall' precise. There is a gap for borderline cases, but 'tall or not-tall' is still true wherever you draw a boundary.
Gist of Idea
Supervaluationism keeps true-or-false where precision can be produced, but not otherwise
Source
R Keefe / P Smith (Intro: Theories of Vagueness [1997], §1)
Book Reference
'Vagueness: a Reader', ed/tr. Keefe,R /Smith,P [MIT 1999], p.7
A Reaction
[Kit Fine is the spokesperson for this; it preserves classical logic, but not semantics] This doesn't seem to solve the problem of vagueness, but it does (sort of) save the principle of excluded middle.