We present a propositional logic %which can be used to reason about the
uncertainty of events, where the uncertainty is modeled by a set of probability
measures assigning an interval of probability to each event. We give a sound
and complete axiomatization for the logic, and show that the satisfiability
problem is NP-complete, no harder than satisfiability for propositional logic.Comment: A preliminary version of this paper appeared in Proc. of the 17th
Conference on Uncertainty in AI, 200