Abstract
Geoffrey Rose’s prevention paradox points to a tension between two prima facie plausible moral principles: that we should save the greater number and that weshould save the most at risk. This paper argues that a novel moral theory, ex-ante contractualism, captures our intuitions in many prevention paradox cases, regardless of our interpretation of probability claims. However, it goes on to show that it might be impossible to square ex-ante contractualism with all of our moral intuitions. It concludes that even if ex-ante contractualism cannot furnish an entire ethics of risk, it does identify important considerations for any such theory.