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MPA 8300
Leadership Ethics






















































































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"[To] do this to the right person, to the right extent, at the right time,
with the right motive, and in the right way,
that is not for every one nor is it easy;
wherefore goodness is both rare and laudable and noble."
(Aristotle, Ethics II.9)


The principle of double effect aims to provide specific guidelines for determining when it is ethically permissible for a human being to engage in conduct in pursuit of a good end with full knowledge that the conduct will also bring about bad results.  Although there has been much substantive disagreement concerning the precise formulation of this principle, the principle of double effect generally states that, in cases where an agent contemplates conduct that has both good effects and bad effects, the course of conduct selected is ethically permissible only if it is not wrong in itself and if it does not require that one directly intend the bad result.

Historically, the principle of double effect is rooted in the medieval natural law tradition, especially in the thought of Thomas Aquinas (1225?-1274).  For generations, the principle of double effect was largely confined to discussions by Roman Catholic moral theologians.  But, in recent decades, the principle has begun to figure prominently in the discussion of ethicists as well as that of a broad range of contemporary philosophers who are interested in both ethical theory and applied ethics because this principle has many applications to ethically complex cases in which an agent cannot achieve a particular desired good result without also bringing about some clearly bad result.

Understood in this way, the principle of double effect "perfects" natural law theory as is evident in American jurisprudence.  While murder is "unnatural" and, hence, unethical, there are four degrees of murder that can be assigned to such actions and different punishments are meted out for each degree.  Only first degree murder, which assumes premeditated conduct, merits the death penalty in some jurisdictions.

The content of the principle of double effect...

Classical formulations of the principle of double effect require that four conditions be met if the conduct in question is to be ethically permissible.  First: the action contemplated by the agent be in itself either ethically good or ethically indifferent (the principle of respect for the agent's autonomy).  Second: that the evil consequence not be directly intended by the agent (the principle of nonmalfeasance).  Third: the good result not be a direct causal result of the evil result (the principle of beneficence).  Fourth: the good result must be "proportionate to" the evil result (the principle of justice).

Of these four conditions, the first two are general rules of ethics.  A human being is never allowed to engage in ethically bad conduct.  Nor may one ever positively will a bad effect of an action, even though the act would otherwise be lawful.  The classical example involves a censor of books or movies who is allowed to read obscene literature or preview obscene movies (like a parent deciding about what books or movies a teenager may read or watch).  However, the censor may not engage in this conduct for the purpose of taking deliberate pleasure in the unethical thoughts arising as a consequence of reading the literature or previewing a movie, although this individual must necessarily permit these thoughts to enter his mind.  The third and fourth conditions, the principles of beneficence and justice, pertain specifically to the principle of the double effect.

Each of these four conditions has, however, been a matter of considerable controversy.

The first condition requires some criterion independent of an evaluation of consequences in order to determine the ethical character of the proposed action. Objecting to this requirement are those ethicists who believe that the ethical character of conduct is exhaustively determined by the nature of its consequences (e.g., utilitarian ethics).

The second condition assumes a sharp distinction can be drawn between directly intending a result and merely foreseeing it.  The principle of nonmalfeasance has been the subject of considerable debate.  Some ethicists argue that, if an agent recognizes a certain consequence will inevitably follow from a contemplated action then, in performing the action, the agent must be intending the consequence.  Other ethicists argue, however, that those who defend the principle have failed to delineate any practicable criterion delineating the "intended" from the "foreseen."  Human beings are not omniscient, these ethicists argue.  Defenders typically respond by pointing to the implicit recognition of the ethical significance of this distinction in the ethical conduct of ordinary human beings.

The third condition writes into the principle of double effect the "Pauline principle," that is, "One should never do evil so that good may come."  Reflect, for example, upon the debate raging about stem cell research.  Is the intentional destruction of a fertilized ovum acceptable because it may assist researchers to find cures for dreadful and debilitating diseases?  Again, ethicists who reject the view that conduct can have an ethical character independent of its consequences find this condition unacceptable.

The fourth condition introduces the notion of proportionality into deliberation which, many ethicists believe, undercuts the ethical absolutism presupposed by the first condition. Although the first three conditions have a decidedly anticonsequentialist (and, antiutilitarian) character, the fourth could appear to embrace consequentialist reasoning.  Defenders of the principle of justice attempt to accommodate the consequentialist character of the fourth condition while ensuring that it does not render the more complex features of the principle irrelevant.

Applying the principle of double effect...

Supporters of the principle of double effect argue that, in situations which a "double effect" follows from one's conduct and where all four conditions are met, the conduct under consideration by the agent is ethically permissible despite the bad result.  As a consequence of this line of reasoning, the principle of double effect has played a significant role in the discussion of many difficult ethical questions.

The most prominent applications are found in medical ethics, where the principle figures prominently in attempts to distinguish among permissible and impermissible procedures in a range of cases.  These include:

  • Palliative care, euthanasia, and physician-assisted suicide
  • Birth control pills
  • Bioethics, nonprofessional bioethics, euthanasia, genetics

Should a pain-killing drug be administered to a person suffering intense, unendurable pain?  A physician may prescribe and a nurse may administer doses of morphine that are large enough to ease the pain but will also hasten death.  Conduct aimed at relieving pain is ethically legitimate in itself because the patient's death was not intended nor was it the means by which the pain was to be relieved.

Consider the case where a pregnancy may need to be terminated in order to preserve the life of the mother.  The principle of double effect is alleged to allow the removal of a life-threatening cancerous uterus, even though this procedure will bring the death of a fetus, on the grounds that in this case the death of the fetus is not "directly" intended.  The principle of double effect disallows cases, however, in which a craniotomy (the crushing of the fetus's skull) is required to preserve a pregnant woman's life, on the grounds that here a genuine evil, the death of the fetus, is "directly" intended.  There is significant disagreement, even among those ethicists who accept the principle, about the cogency of this application.  Some argue, by emphasizing the fourth criterion of "proportionality," that the greater value attaching to the pregnant woman's life makes even craniotomy ethically acceptable.  Other ethicists fail to see a significant difference between the merely "foreseen" death of the fetus in the cancerous uterus case and the "directly" intended death in the craniotomy case.

Still other ethicists argue that the mother's willingness to sacrifice her life for the sake of her child, as is the case of St. Gianna Beretta Molla, reflects a character fully grounded in the philosophical (or "natural") virtue of courage and the theological (or "cardinal") virtue of love.  Consider the application of the principle of double effect in a similar case.  A pregnant woman bearing a nonviable fetus, for example, may be found to have a cancerous womb that will cause her death if it is not excised as soon as possible.  The operation of hysterectomy is ethically lawful, for this operation is permissible in itself as a normal means of saving the woman's life.  She does not positively will the death of her child, but permits it as an unavoidable evil.  Both the benefit to her health and the death of her child follow from the surgery with equal directness or immediacy in the order of causality, although the death of the child is prior in the order of time.  The woman's chance of restoration to health (the good effect) is sufficiently desirable to compensate for the death of the fetus (the bad effect), which most likely probably not survive even if the operation were not performed.

However, were the woman suffering from kidney disease, heart trouble, or tuberculosis, which would be easier to care for if she were relieved of the pregnancy, it would be unethical to perform an abortion.  The reason?  In this case the third condition for the proper use of the principle of the double effect is lacking.  The relief to the woman comes as an effect of the abortion, not directly as an effect of the surgery.  Hence, a bad means would be employed to produce a good end.

The principle of double effect can be applied to questions about defending oneself.  For example, St. Thomas may have visualized this principle it when he argued in the Summa theologiae (2a2ae, 64.7) that a person may kill an unjust aggressor when this is necessary to save his own life.  That is, a defensive action to impede an unjust attack upon one's life may also result in the attacker's death.  However, the intention was not to kill the attacker but to stop the attack.  Had the intention to be to kill the attacker, killing the attacker would be unethical.  However, the attacker's death is not the means by which the individual saved one's life; successfully stopping the attack is.  One difficulty in the application of the principle of double effect to this case, however, is that it seems to lack the third condition, since the preservation of one's own life seems to follow from the killing of the aggressor.  Hence, theologians would argue in this case that God gives permission to the victim to protect oneself, if necessary, by a direct slaying of the unjust assailant.

The principle of the double effect also applies to waging modern warfare, in particular, on protecting civilian life in time of war.

Consider the following situation which confronted President Harry S. Truman.  A nation may launch an air attack on an important military objective of the enemy even though a comparatively small number of noncombatants are killed.  This evil effect is compensated for by the great benefit gained through the destruction of the target.  This would not be true, however, if the number of noncombatants slain in the attack were out of proportion to the benefits gained, as is clear from the fourth condition, namely, the principle of justice.  Furthermore, if the direct purpose of the attack was to kill a large number of noncombatants so that the enemy's morale would be broken down and they would sue for peace, the attack was be unethical because the third condition for the lawful use of the principle of double effect (the principle of nonmalfeasance) would not be fulfilled because a nation would be using a bad means to obtain a good end.

Cases applying the principle of double effect tend to be stated in the abstract.  But, people frequently apply the principle of double effect in the ordinary affairs of human life largely unaware of the principle's four speculative requirements and relying on common sense instead.

Consider the following examples of physical evils such as danger to life and bodily welfare that are ordinarily tolerated because of the good outcome that is envisioned:

  • an aviator who tests planes in order to improve aeronautic equipment but may crash and die as a result;
  • the doctor who treats patients affected with contagious diseases and may become infected himself;
  • the policeman who attempts to capture an armed criminal and, in the process, may be killed;
  • the fireman who responds to a three-alarm fire and may die as a result of fighting the fire; and,
  • the priest who ministers to lepers and may become leprous himself.

All of these actions are ethical using the principle of the double effect because the bad effect that these agents may incur to their own life or health is overweighed by the good effect their conduct confers upon society.


Aristotle. (1958). Nicomachean ethics (W. D. Ross, Trans.) In J. D. Kaplan (Ed.), The pocket Aristotle (pp. 158-274). New York: Washington Square Press.