The Principle of Double Effect: The Conditions of Bringing About Evil

THE PRINCIPLE OF DOUBLE EFFECT is the principle that ought to be applied in fulfilling the moral injunction of doing good as far as one can, and avoiding evil as far as one can. Specifically, the principle of double effect relates to the latter half of the basic moral equation: avoiding evil as far as one can. It is applicable in those cases, actually quite frequent, where good or at least not evil acts have consequences beyond those acts, unintended but foreseeable, that may be evil or that may have good mixed with evil. When are such good or at least not evil acts, which have these foreseen undesirable effects, permissible, and when not?

If we were to apply the rule that no good that has any foreseeable, yet unintended evil consequence can be done, we would be crippled. We could not get into our car and drive to the grocery store to pick up milk for our family's breakfast because it is a foreseeable, though unintended consequence, that we might run over some pedestrian along the way. We could not enjoy beurre blanc on our vegetables or scallops because it is a foreseeable though unintended consequence that such a wine and butter sauce would increase our weight and affect our cholesterol and, albeit remotely, lead to heart disease and possible death.

Are scallops with beurre blanc sauce to be shunned because
it is foreseeable that consuming them contributes
to heart disease and eventual death?

The principle of double effect helps us draw the line when confronting these decisions, and we use it almost instinctively. It helps, however, to be cognizant of the principle because it is a very helpful tool in addressing some of the more difficult moral questions in controversial areas such as those we confront at the edge of technology in bioethics, in self-defense, and in war.**

The principle of double effect requires that there be four conditions, all of which must be met, before an act may be performed that has both good and evil effects:

• First, the intended act must be good or at least permissible (i.e., not evil).
• Second, the good effect of the intended act must follow from that intended act as immediately as the evil effect. The analysis here is causal not temporal, meaning that the evil effect either has to be caused by the good effect or the evil effect and good effect have to arise simultaneously as a result of the intended act. In other words, the good effect must not be caused by the evil effect.*
• The evil effect must not be intended, or willed; rather it should not be desired, and, at best, it is simply permitted or tolerated, and perhaps even regretted or not desired, as an unavoidable consequence that follows from or comes with the good;
• There must be a proportionate and sufficient reason, associated with the intended good and its good effect, for permitting or tolerating the evil effect.
  

The last requirement, that of proportionate reason, is the most subtle, and the most difficult in practice to weigh. It is in this area in particular where prudence is most essential. It is this area also where the inexactness of the moral answer is most felt. As we have discussed before, inexactness is not the same as lack of knowledge. There are, however, some general principles that guide us in assessing whether under any given circumstance a proportionate reason exists for doing a good or at least permissible act, intending a good effect, yet foreseeing that an evil effect either arises in conjunction with the good effect or is caused by the good effect.

• The greater the evil effect, the greater the reason for permitting it needs to be. There has to be a serious reason for allowing a foreseeable evil to happen as a result of one of our acts, even if unintended.
• If the unintended evil effect would probably happen whether or not we performed our act, then a lesser reason for acting is required.
• A greater reason is required to permit an unintended evil effect from occurring if foregoing the the act would definitely and effectively prevent the evil effect from happening.
• The probability of the evil effect occurring must be taken into consideration. If the unintended evil effect may only possibly occur, then a lesser reason is required than if the unintended evil effect is certain to occur.
• If the actor is under a prior duty to prevent the unintended evil effect, then a greater reason is required to permit the unintended evil effect.
• If the actor has two ways of obtaining the intended good effect, one of which results in the unintended evil effect, and the other which does not result in the unintended evil effect, he must opt for the way without the unintended evil effect, as there no reason then to justify taking the course of action that results in unintended evil.
  

Our next blog posting will address common criticisms against the principle of double effect, and responses to those criticisms from the perspective of traditional ethics.

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*If the good effect followed from the evil effect, then one would be intending the evil effect as a means of bringing about the good effect. But it is axiomatic that the end does not justify the means. This is basic: St. Paul condemns those who would argue that one ought to do evil so that good may come. (cf. Rom. 3:8) (faciamus mala ut veniant bona quorum damnatio iusta est) (ποιήσωμεν τὰ κακὰ, ἵνα ἔλθῃ τὰ ἀγαθά; ὧν τὸ κρίμα ἔνδικόν ἐστιν). Because it is mentioned by St. Paul, this principle is sometimes referred to as the Pauline principle. Cf. William Penn, Some Fruits of Solitude (London: S. T. Freemantle, 1900), 122. ("To do evil, that good may come of it, is for bunglers in politics as well as morals.")
**I rely heavily on Oderberg, MT, 88-96, for this discussion on PDE (Principle of Double Effect).