An action that is good in itself that has two effects–an intended and otherwise not reasonably attainable good effect, and an unintended yet foreseen evil effect–is licit, provided there is a due proportion between the intended good and the permitted evil. When there is a clash between the two universal norms of “do good” and “avoid evil,” the question arises as to whether the obligation to avoid evil requires one to abstain from a good action in order to prevent a foreseen but merely permitted concomitant evil effect. The answer is that one need not always abstain from a good action that has foreseen bad effects, depending on certain moral criteria identified in the principle of double effect.
Though five are listed here, some authors emphasize only four basic moral criteria (the fifth listed here further specifies the third criterion): The object of the act must not be intrinsically contradictory to one’s fundamental commitment to God and neighbor (including oneself), that is, it must be a good action judged by its moral object (in other words, the action must not be intrinsically evil); The direct intention of the agent must be to achieve the beneficial effects and to avoid the foreseen harmful effects as far as possible, that is, one must only indirectly intend the harm; The foreseen beneficial effects must not be achieved by the means of the foreseen harmful effects, and no other means of achieving those effects are available; The foreseen beneficial effects must be equal to or greater than the foreseen harmful effects (the proportionate judgment); The beneficial effects must follow from the action at least as immediately as do the harmful effects. Doctrine of Double Effect
he doctrine (or principle) of double effect is often invoked to explain the permissibility of an action that causes a serious harm, such as the death of a human being, as a side effect of promoting some good end. It is claimed that sometimes it is permissible to cause such a harm as a side effect (or “double effect”) of bringing about a good result even though it would not be permissible to cause such a harm as a means to bringing about the same good end. This reasoning is summarized with the claim that sometimes it is permissible to bring about as a merely foreseen side effect a harmful event that it would be impermissible to bring about intentionally. 1. Formulations of the principle of double effect
Thomas Aquinas is credited with introducing the principle of double effect in his discussion of the permissibility of self-defense in the Summa Theologica (II-II, Qu. 64, Art.7). Killing one’s assailant is justified, he argues, provided one does not intend to kill him. Aquinas observes that “Nothing hinders one act from having two effects, only one of which is intended, while the other is beside the intention. … Accordingly, the act of self-defense may have two effects: one, the saving of one’s life; the other, the slaying of the aggressor.” As Aquinas’s discussion continues, a justification is provided that rests on characterizing the defensive action as a means to a goal that is justified: “Therefore, this act, since one’s intention is to save one’s own life, is not unlawful, seeing that it is natural to everything to keep itself in being as far as possible.” However, Aquinas observes, the permissibility of self-defense is not unconditional: “And yet, though proceeding from a good intention, an act may be rendered unlawful if it be out of proportion to the end. Wherefore, if a man in self-defense uses more than necessary violence, it will be unlawful, whereas, if he repel force with moderation, his defense will be lawful.” Aquinas does not actually say that intending to kill the assailant as a means to self-defense would be prohibited.
The passage can be interpreted as formulating a prohibition on apportioning one’s efforts with killing as the only goal guiding one’s actions, which would lead one to act with greater viciousness than the goal of self-defense would allow. In contrast, Augustine had earlier maintained that killing in self-defense was not permissible, maintaining that “private self-defense can only proceed from some degree of inordinate self-love.” Later versions of the double effect principle all emphasize the distinction between causing a morally grave harm as a side effect of pursuing a good end and causing a harm as a means of pursuing a good end. We can summarize this by noting that for certain categories of morally grave actions, for example, causing the death of a human being, the principle of double effect combines a special permission for incidentally causing death for the sake of a good end (when it occurs as a side effect of one’s pursuit of that end) with a general prohibition on instrumentally causing death for the sake of a good end (when it occurs as part of one’s means to pursue that end). The prohibition is absolute in traditional Catholic applications of the principle.
Two traditional formulations appear below. The New Catholic Encyclopedia provides four conditions for the application of the principle of double effect: The act itself must be morally good or at least indifferent. The agent may not positively will the bad effect but may permit it. If he could attain the good effect without the bad effect he should do so. The bad effect is sometimes said to be indirectly voluntary. The good effect must flow from the action at least as immediately (in the order of causality, though not necessarily in the order of time) as the bad effect. In other words the good effect must be produced directly by the action, not by the bad effect. Otherwise the agent would be using a bad means to a good end, which is never allowed. The good effect must be sufficiently desirable to compensate for the allowing of the bad effect“ (p. 1021).
The conditions provided by Joseph Mangan include the explicit requirement that the bad effect not be intended: A person may licitly perform an action that he foresees will produce a good effect and a bad effect provided that four conditions are verified at one and the same time: that the action in itself from its very object be good or at least indifferent; that the good effect and not the evil effect be intended; that the good effect be not produced by means of the evil effect; that there be a proportionately grave reason for permitting the evil effect” (1949, p. 43). Double effect might also be part of a secular non-absolutist view according to which a justification adequate for causing a certain harm as a side effect might not be adequate for causing that harm as a means to the same good end under the same circumstances. Warren Quinn provides such a non-absolutist account that also recasts double effect as a distinction between direct and indirect agency. On his view, double effect “distinguishes between agency in which harm comes to some victims, at least in part, from the agent’s deliberately involving them in something in order to further his purpose precisely by way of their being so involved (agency in which they figure as intentional objects), and harmful agency in which either nothing is in that way intended for the victims or what is so intended does not contribute to their harm” (1989, p. 343).
Quinn explains that “direct agency requires neither that harm itself be useful nor that what is useful be causally connected in some especially close way with the harm it helps bring about” (1989, p. 344). He remarks that “some cases of harming that the doctrine intuitively speaks against are arguably not cases of intentional harming, precisely because neither the harm itself (nor anything itself causally very close to it) is intended” (1991, p. 511). On this view, the distinction between direct and indirect harmful agency is what underlies the moral significance of the distinction between intended and merely foreseen harms, but it need not align perfectly with it. 2. Applications
Many morally reflective people have been persuaded that something along the lines of double effect must be correct. No doubt this is because at least some of the examples cited as illustrations of DE have considerable intuitive appeal: The terror bomber aims to bring about civilian deaths in order to weaken the resolve of the enemy: when his bombs kill civilians this is a consequence that he intends. The tactical bomber aims at military targets while foreseeing that bombing such targets will cause civilian deaths. When his bombs kill civilians this is a foreseen but unintended consequence of his actions. Even if it is equally certain that the two bombers will cause the same number of civilian deaths, terror bombing is impermissible while tactical bombing is permissible. A doctor who intends to hasten the death of a terminally ill patient by injecting a large dose of morphine would act impermissibly because he intends to bring about the patient’s death.
However, a doctor who intended to relieve the patient’s pain with that same dose and merely foresaw the hastening of the patient’s death would act permissibly. (The mistaken assumption that the use of opioid drugs for pain relief tends to hasten death is discussed below in section 5.) A doctor who believed that abortion was wrong, even in order to save the mother’s life, might nevertheless consistently believe that it would be permissible to perform a hysterectomy on a pregnant woman with cancer. In carrying out the hysterectomy, the doctor would aim to save the woman’s life while merely foreseeing the death of the fetus. Performing an abortion, by contrast, would involve intending to kill the fetus as a means to saving the mother.
To kill a person whom you know to be plotting to kill you would be impermissible because it would be a case of intentional killing; however, to strike in self-defense against an aggressor is permissible, even if one foresees that the blow by which one defends oneself will be fatal.It would be wrong to throw someone into the path of a runaway trolley in order to stop it and keep it from hitting five people on the track ahead; that would involve intending harm to the one as a means of saving the five. But it would be permissible to divert a runaway trolley onto a track holding one and away from a track holding five: in that case one foresees the death of the one as a side effect of saving the five but one does not intend it.Sacrificing one’s own life in order to save the lives of others can be distinguished from suicide by characterizing the agent’s intention: a soldier who throws himself on a live grenade intends to shield others from its blast and merely foresees his own death; by contrast, a person who commits suicide intends to bring his or her own life to an end.