Talk of two or more people sharing responsibility for an outcome is very common. As I shall try to show, it can also be very misleading. I am concerned here with moral responsibility only and not with legal responsibility. I am concerned, too, only with what may be called retrospective responsibility (responsibility for past occurrences) and not with prospective responsibility (responsibility for future occurrences). And I am concerned only with the ascription of responsibility to individuals. It is doubtless true that we sometimes ascribe responsibility — even retrospective moral responsibility — to groups or collections of individuals. Some philosophers believe that all such ascription of responsibility can be reduced to the ascription of responsibility to individuals in the collection(s) at issue. Others believe otherwise. I am concerned here with none of this, although it is true that, when the question of sharing responsibility for an outcome arises, it does so primarily in the context of an outcome to which several individuals have contributed (or omitted to contribute).
