San Diego Law Review

Document Type



Under what conditions is it morally permissible to kill someone in order to save your own life—or the life of another who is threatened? There seem to be clear cases. Threatened by an assailant who is trying to kill you for no good reason, you may use lethal force if necessary to save yourself from death or serious injury from the assailant’s attack. Threatened with death in the form of an onrushing runaway truck, you may not save yourself by using a bystander or imposing on a bystander in a way that inflicts severe harm on her. In a justly celebrated essay, Judith Thomson notes that it is permissible to kill a “Villainous Aggressor” when necessary to save oneself from grievous harm, but adds that the evil intent —and thus culpability—of the Villainous Aggressor is not a necessary condition for justified self-defense. She suggests that if we remove the elements of evil intent and culpability, and imagine an “Innocent Aggressor” whose actions pose a threat of causing one grave physical harm, one gets a similar moral permission to kill in self-defense. Moreover, if we remove the element of agency altogether, and imagine an “Innocent Threat,” whose bodily movements pose a threat of inflicting grave physical harm on one, but who is not at fault in any way for posing this threat, and is not doing anything at all, one gets a similar moral permission to kill in self-defense. Still, Thomson asserts, the differences between Villainous Aggressor, Innocent Aggressor, and Innocent Threat make “no moral difference”—to the permissibility of self-defense. Hence, according to Thomson, “it is permissible for you to proceed in Innocent Threat just as in Villainous Aggressor and Innocent Aggressor.” Pondering these suggestions, she proposes, “I fancy we overrate the role of fault in many areas of moral theory.”