Full Idea
Non-linguistic objects, properties, and states of affairs cannot be indeterminate because they cannot have determinate truth-values either. No cloud is indeterminate, just as no cloud is either determinately true or determinately false.
Gist of Idea
Non-linguistic things cannot be indeterminate, because they don't have truth-values at all
Source
Katherine Hawley (How Things Persist [2001], 4.1)
Book Reference
Hawley,Katherine: 'How Things Persist' [OUP 2004], p.102
A Reaction
If vagueness must be linguistic, this means animals can never experience it, which I doubt. Presumably 'this is a cloud' is only made vague by the vagueness of the object, rather than by the vagueness of the sentence?