Moral Uncertainty for Deontologists

Defenders of deontological constraints in normative ethics face a challenge: how should an agent decide what to do when she is uncertain whether some course of action would violate a constraint? One common response to this challenge proposes a threshold principle on which it is subjectively permissible to act iff the agent’s credence that her action would be constraint-violating is below some threshold t. But the threshold approach seems arbitrary and unmotivated: where does the threshold come from, and why should it take any one value rather than another? Threshold views also seem to violate “ought” agglomeration, since a pair of actions each of which is below the threshold for acceptable moral risk can, in combination, exceed that threshold. In this paper, I argue that stochastic dominance reasoning can vindicate and lend rigor to the threshold approach: given characteristically deontological assumptions about the moral value of acts, it turns out that morally safe options will stochastically dominate morally risky alternatives when and only when the likelihood that the risky option violates a moral constraint is greater than some precisely definable threshold (in the simplest case, .5). The stochastic dominance approach also allows a principled, albeit intuitively imperfect, response to the agglomeration problem. Thus, I argue, deontologists are better equipped than many critics have supposed to address the problems of decision-making under uncertainty.