 Stephen Schiffer (2003, 204) denies that classical probability calculations apply in vague contexts. Suppose Donald is borderline old and borderline bald. According to Schiffer we should be just as confident in the conjunction ‘Donald is old and bald’ as in either conjunct. Adding conjuncts does not reduce confidence because we have a “vague partial belief” rather than the standard belief assumed by mathematicians developing probability theory. Schiffer offers a calculus for this vagueness-related propositional attitude. He crafts the rules for vague partial belief to provide a psychological solution to the sorites paradox.