Abstract
I motivate and briefly sketch a linguistic theory of vagueness, on which
the notion of indeterminacy is understood in terms of the conventions of
language: a sentence is indeterminate iff the conventions of language
either forbid asserting it and forbid asserting its negation, under the
circumstances, or permit asserting either. I then consider an objection
that purports to show that if this theory (or, as far as I can see, any
other theory of vagueness that deserved the label "linguistic"
were true, there would be no such thing as indeterminacy. I respond to
this objection by arguing on independent grounds against its main premise,
the widely-accepted claim that if it is indeterminate whether P,
no human being knows whether P. I defend an alternative view
according to which, when it is indeterminate whether P, it is
often also indeterminate whether we know that P.