Belief revision revised

Abstract

I outline a novel counterexample to the principle ofbelief revision, Anticipation: if both learning 𝑒 andlearning not-𝑒 would render belief in 𝑝 unjustified, youcannot now be justified in believing 𝑝. If I am right,not only is the leading theory of belief revision false, soare various recently proposed weakenings. I develop anddefend a new theory that correctly predicts the failuresof Anticipation I argue for, predicated on the simpleidea that one is justified in ruling out possibility just incase that possibility is sufficiently improbable.