Sometimes we cannot benefit one person without harming, or failing to help, another; and where the cost to the other would be serious – where, for example, he would die – a substantial moral question is raised: would the benefit justify the harm? Some moralists would answer this question by balancing the good against the evil. But others deny that consequences are the only things of moral relevance. To them it also matters whether the harm comes from action, for example, from killing someone, or from inaction, for example, from not saving someone. They hold that for some good ends we might properly allow a certain evil to befall someone, even though we could not actively bring that evil about. Some people also see moral significance in the distinction between what we intend as a means or an end and what we merely foresee will result incidentally from our choice. They hold that in some situations we might properly bring about a certain evil if it were merely foreseen but not if it were intended.

Those who find these distinctions morally relevant think that a benefit sufficient to justify harmful choices of one sort may fail to justify choices no more harmful, but of the other sort. In the case of the distinction between the intentional and the merely foreseen, this view is central to what is usually called the Doctrine of Double Effect (DDE).