The epistemic conception of vagueness

• Stoic logicians?
• Late 1980s and early 1990s - Roy Sorensen and Paul Horwich
• Timothy Williamson

Arguments for

Argument from T-schema

No sentence that says something is neither true nor false.

1. u says that p
2. It is not the case that: u is true or u is false.
3. If u says that p, then u is true iff p
4. If u says that p, then u is false iff ¬p
5. u is true iff p (MP 1,3)
6. u is false iff ¬p (MP 1,3)
7. It is not the case that: p or u is false. (Substitution 2,5)
8. It is not the case that: p or ¬p (Substitution 6,7)
9. ¬p and ¬¬p (De Morgan 8)

Margin of error

Higher order vagueness

Objections

If vague concepts really do have sharp boundaries, what determines where those boundaries lie?

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