Full Idea
Vagueness is of great philosophical interest because it seems to be inconsistent with the view that every proposition is true or false.
Gist of Idea
Vagueness seems to be inconsistent with the view that every proposition is true or false
Source
Thomas Mautner (Penguin Dictionary of Philosophy [1996], p.585)
Book Reference
Mautner,Thomas: 'Dictionary of Philosophy' [Penguin 1997], p.585
A Reaction
This would explain why Williamson and Sorensen are keen to argue that vagueness is an epistemological (rather than ontological) problem. In ordinary English we are happy to say that p is 'sort of true' or 'fairly true'.