Full Idea
There are three main views of vagueness: the Epistemic view says we talk precisely, but don't know what we talk precisely about; the Semantic view is that it is loose talk, or semantic indecision; the Ontic view says it is part of how the world is.
Gist of Idea
Vagueness is either in our knowledge, in our talk, or in reality
Source
Katherine Hawley (How Things Persist [2001], 4.1)
Book Reference
Hawley,Katherine: 'How Things Persist' [OUP 2004], p.101
A Reaction
[My summary of two paragraphs] She associates Williamson with the first view, Lewis with the second, and Van Inwagen with the third.