Familiar questions about whether or how far to impose risks of harm for social benefit present a fundamental dilemma for contractualist moral theories. If contractualism allows objections by considering actual outcomes, it becomes difficult to justify the risks created by most public policy, leaving contractualism at odds with moral commonsense in much the way utilitarianism is. But if contractualism instead takes a fully form by considering only expected outcomes, it becomes unclear how it recommends something other than aggregative cost-benefit decision-making. (...) Focusing on T.M. Scanlon's version, this paper develops this basic choice of interpretation and recommends the ex ante version. The paper explains how contractualism is inconsistent with John Harsanyibad aggregationgood aggregation” that is both unavoidable and fully appropriate in public life. (shrink)