Why does utilitarianism seem so unlikely a basis for noncombatant immunity? Two features of utilitarianism account for this. The first is that utilitarian morality has a goal, the promotion of overall well-being. Noncombatant immunity, however, is a constraint on action. It places limits on how people can pursue their goals. The second feature is that utilitarians have vigorously opposed what they saw as rigid, tradition-bound moralities that consist of useless, often harmful taboos. This feature can easily express itself as hostility toward the idea that rules and principles play an important role in morality. Rules, however, play many important roles in human life. Social life as we know it would be impossible if there were not a set of well-known, widely accepted rules. We could not function if we were unable to generally trust people to tell the truth and keep agreements most of the time. Having explicit rules about these and other actions helps to sustain the necessary level of predictable behavior.

Most moral rules are not absolute. We recognize that violations of them are sometimes permissible. There are times when killing, stealing, lying, breaking promises, etc. are the right thing to do. (Strictly, of course, a permissible exception is not a violation.) One reason why there are permissible exceptions is that it is hard to fashion general rules that work in all cases because we cannot anticipate all the conditions we will face in the future.