January 2025 Print

The Principle of Double Effect and Bioethics

By Fr. Ian Andrew Palko, SSPX

Every few years when the election cycle gears up in the United States, Catholics are presented with candidates for office who typically do not embrace all of what a fully-Catholic citizenry would demand. Often this is on matters of abortion, in-vitro fertilization, defense of the family, or even the proper relation of the church and state. Imperfect though these candidates are, one commonly hears that he ought to choose the “lesser of two evils” especially when one candidate seems particularly bad.

While this is presented in a less-than-proper manner—even the Apostle condemns the doing of evil that good may come from it¹ and Natural Law would condemn the willful choice of any evil qua evil—there is obviously something true standing behind this advice. Man’s will is made to choose between goods, not between good and evil, but rarely is he presented with a choice purely between two good things with no disadvantage intervening.

Almost every choice a man will make has some effects which could be considered “evil” in the way St. Augustine understood it. For this Doctor of the Church evil has no real existence in itself, but is the absence of some good which ought to exist.² It is not evil that a man cannot fly, because it does not belong to his nature to be able to do so. It is evil when he lacks a certain quality he ought to have. This could be a physical evil such as the lack of an arm due to an accident or defect, or it could be a moral evil, when something such as the virtue of Prudence, which he ought to have, is lacking. The lack of such a virtue to the degree he ought to possess it will be due to his own willful choice. When the will intervenes to culpably prevent the accomplishment of a good, or to seek an object evil, there is moral evil or sin.

Many morally good actions that humans engage in have mixed effects, some good and some evil. By this is not meant morally good or evil actions, but effects men perceive to be harmful, such as the loss of a limb, or even death. If moral evils were part of good effects, this would mean good actions involve sins. Rather, here “evil” effects mean the “lack of a due good”.

For example, one who is undergoing treatment for cancer often will receive chemotherapy agents or radiation, which are, effectively, poisons. Their use has a good effect (i.e., to destroy the cancerous cells), but also an evil effect (i.e., the damage and destruction of healthy tissue). Other examples will frequently reference medical procedures, but such mixed effects are not exclusive to medicine.

In such cases, ethicists and moral theologians speak of the indirect voluntary or the principle of double effect (even when there are multiple effects). It is called the “indirect voluntary” because one chooses one action with its good effect, while indirectly accepting another evil effect. While even Aristotle speaks of this concept in his Nicomachean Ethics,³ modern expositions reference St. Thomas Aquinas’ words on killing in self-defense as the source of these principles.⁴

St. Thomas explains that an action may have an evil and good effect, and that killing in self-defense when one’s life is threatened can be morally justified when one intends to preserve his life (and not to kill another), and there is a just proportion, or in other words, his life is truly imminently threatened. He also, however, explains that

The act of self-defense may have two effects, one is the saving of one’s life, the other is the slaying of the aggressor. Therefore this act, since one’s intention is to save one’s own life, is not unlawful … [a]nd 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.⁵

In answering the objections, St. Thomas also explains that intrinsically evil actions cannot be done that good flow from them. Killing is not intrinsically evil, while murder (i.e. intentional unjust killing of an innocent) is. On the other hand, while murder is a greater sin than adultery, nevertheless, because adultery is intrinsically evil it is never permitted, even if some perceived good, including the preservation of one’s life, should flow from it.⁶ Thus a St. Maria Goretti would prefer death (and that he who tried to cause her to sin would be guilty of murder) over committing a sin to preserve her own life and prevent him from committing the sin of murder. Evil could not be done that good flow from it, and in avoiding evil, she won a crown of martyrdom for purity.

Principles of Double Effect

From St. Thomas’ theology and the development of those who follow his system of morality, one can identify four main criteria in whether an action with a double effect is permissible to do:

1. The action must be morally good or at least morally neutral: Any action which is inherently evil can never be done;
2. The good effect must be the primary thing intended, and the evil effect merely tolerated and not intended in any way, and steps taken to avoid this evil effect as much as reasonably possible;
3. The evil effect must not be the means to obtain the good effect, as this would de facto be to do evil that good come from it, contrary to the Natural Law and Rom. 3:8;
4. There must be a just proportion between the good achieved and evil tolerated.

Each of these points bears further explanation.

To the first point, when judging if an action is morally good, neutral, or evil, one does not look at the intentions of those acting or circumstances, but the moral object. The moral object is that result which an action tends towards by its very nature. There are no truly neutral actions once the circumstances or intentions enter into the picture, as these will take something morally neutral and make it evil or good. If the moral object is evil, no circumstances or intentions can absolve it of this evil, even if a true ignorance could absolve someone of guilt for doing this evil.

For example, to provide a patient in a hospital with water tends, of its nature, towards hydration. This is a morally good or neutral act. On the other hand, to borrow St. Thomas’ example, an act like adultery always tends towards an injustice and violation of the moral law, and so is inherently or intrinsically evil. No circumstances or intentions can vitiate this evil and make adultery a morally good act, no matter how much good flow from this action.

So, in order to consider doing an action that could have an unintended evil effect, one must first determine that the act, in itself, is not evil.

To the second point, now one can begin to consider one of the other two factors in what makes an action morally good or evil: intention. Because one’s action will produce both good and evil effects, one must intend to seek the good effect, and also intend to prevent the evil effects. Included in this is the obligation, after the action, to try to work against the evil effect. If one intends the evil effect, then he wishes evil, and that is sinful.

Similarly, to the third point, the evil effect cannot be the cause of the good effect one desires. Seeing the horror that is abortion, some have been gone to the extreme of undertaking extra-judicial killings of abortionists. The evil effect (the death of the doctor) is the cause of the prevention of more abortions. Even if this may save more lives in the long run, one cannot do evil that good may result.

Finally, the good obtained must significantly exceed the evil suffered. It is not enough that the action results in a slightly better good result, because the evil effect causes harm, and this harm must be repaired. It is not enough that some good result. An leg crushed in an accident which must be amputated means the terrible loss of one’s integrity, but for the benefit of the whole body to live. A far more significant good is obtained by the physical evil of the amputation. On the other hand, the perceived psychological benefit of mutilating one’s body in the situation of Body Dysmorphia, certainly does not exceed the evil effect caused.

This notion, though, can even be extended beyond such examples. St. Thomas Aquinas speaks about this in the change of any rules or laws, indicating that change itself causes a harm that must be repaired by a notably great good to be obtained from this change.⁷ This is, in fact, just an application of the principle of double effect.

Nevertheless, it is worthwhile to ask questions to determine if an actions good effect sufficiently exceeds its bad effect. One can ask

1. How evil is the evil effect?
2. How closely tied to the good effect is the evil effect?
3. How certain is it that the evil effect will eventuate?
4. Does the person acting have a special duty to prevent the evil effect?

In each of these cases, the lesser the evil, the more distant from the good effect and unlikely it is, and the less one has a duty to prevent the evil, the more likely the good exceeds the evil effect sufficiently.

Double Effect in the Sciences

Physical sciences do not require researchers or practitioners to be skilled in ethics beyond those involved in publishing papers and academic honesty. Experiments and research rarely involve deleterious and beneficial effects that need to be considered in planning such work. In the applied sciences, however, such as engineering and medicine, experiments and procedures, such as treatments, are much more likely to have good and bad effects which require a moral or ethical analysis, and possibly the employing of the principles of double effect.

Medicine, in particular, involves the development of treatments that will have direct impacts on human beings, causing potential benefits (a good effect) or harms (an evil effect), so much so that a code of ethics and oath to keep this code, commonly called the Hippocratic Oath, was pledged in some form by physicians from at least the third century B.C. in the West.

While the original oath did not contain the classic principle attributed of primum non nocere—“first, do no harm”—such a principle is easily derived from the spirit of the oath, and is more explicitly contained in the Epidemics.⁸ Non-Western cultures had similar principles, making it clear that these principles are not specifically religious, but rather flow from the Natural Law, and are closely related to double effect principles. Practically, in trying to treat the sick, develop cures for diseases, and help manage incurable or terminal diseases, there will be mixed effects, so the principle of double effect must be employed and understood.

As the variety of treatments, and the more intimate knowledge of biochemistry and genetics has developed, the use of this principle has become even more necessary, and yet, even a half-century ago, Catholic bioethicists and scientists, such Joseph M. Boyle, were already seeing the abandonment of this principle, at least by a lack of understanding of its importance and a lack of concern to maintain it.⁹

For example, in recent years several countries have approved of euthanasia under the guise of being “compassionate” towards those suffering from a seemingly terminal illness. The Natural Law, however, sees suicide or murder as a moral evil, thus the euphemisms used cannot escape the fact that such killing to relieve pain is doing a greater evil that a lesser good may result. It is the intention doing of harm that a false perceived good (the relief of suffering) is obtained. In fact, as a Catholic knows, euthanasia, willfully sought, as a grave sin, trades the end of temporal suffering in this life for an eternity of suffering in the next.

The relief of suffering is not an evil thing, but a good thing, so where it can be accomplished, even in the dying, without causing a greater harm (e.g. death), it should be offered. Because such pain relief comes with the risk of causing death, a careful balance between the risk of an evil effect and the good effect is necessary, and so the principle of double effect needs to be applied. In 2004, for instance, the same Dr. Boyle addressed this careful balance from a Catholic and Natural Law perspective, trying to demonstrate the limits of such pain relief and when the risk of causing death could be tolerated, and when it could not.¹⁰

As has been discussed in these pages and also on the SSPX Podcast, certain medical treatments, even when they can save one from death, may not be morally permissible because the evil effects cannot be tolerated.

Organ donation, by example, often runs into this restriction, because in many cases the organs must be taken from those not yet dead in order that they will be viable in the new host, and this causes the death of the donor. Since one cannot kill someone to harvest their organs, even if it will bring an extended life to someone else, using the principle of double effect and the metrics provided above, such donations are not morally permissible. However, certain donations or procedures may be acceptable or praiseworthy in certain situations.

Even in medical research there is need to consider double effect. It is not uncommon for doctors to propose theoretical treatments that are morally unacceptable, such as the use of fetal-derived stem-cells. These cell lines are harvested from children killed in abortion or produced as “excess” embryos during in-vitro fertilization procedures, thus causing the death of a child to obtain a cell line. Double effect principles obviously hold these processes as immoral, but questions can arise on the use of treatments that are otherwise morally acceptable except that testing was performed on these cell lines. Such was part of the debate on the use of certain vaccinations, many of which are not produced from such cell lines (and so are produced morally), but were incidentally tested for efficacy or safety on immorally-obtained cell lines.

Here the world needs good doctors and scholars well-formed in the Natural Law and Catholic bioethics to help guide research in the correct direction where useful, but also for the discovery of moral treatments. Researchers and physicians already well-grounded in Catholic bioethics are the best chance the world has to restore faith in medicine, and also re-establish the medical sciences on solid moral framework.

The Role of the Parish Priest in Medical Decisions

Nevertheless, even if all were in good order, questions will arise regarding less-routine medical procedures, chronic or terminal diseases, end-of-life care, or high-risk pregnancy. Expert help is needed to understand the moral limits of treatment. Also, it is often necessary to understand when such treatments are morally obligatory or may be optional extraordinary means that someone is permitted to refuse.

Today, with doctors and other medical practitioners frequently failing to appreciate basic truths about reality—holding the mutability of gender, denying the purpose of marriage, refusing to see the psychological disease in unnatural vice, and even failing to see the need to protect innocent life from conception to natural death—a Catholic cannot merely rely on the fact that a medical procedure is available or recommended by a doctor (even sometimes a Catholic doctor). Instead, the advice of moral experts is frequently needed.

This is also the case where, on account of the distrust in modern medicine, alternative therapies or the refusal of common procedures is contemplated. The Church distinguishes between ordinary means to preserve health and life, which are of obligation, and extraordinary means, which may be used, but do not oblige. Too frequently, the refusal of common medical procedures, or the use of alternative therapies have their own moral character which is not always positive. The distrust of the modern zeitgeist—which has some justification—frequently sees traditional Catholics embracing alternative therapies. While some of these provide great benefits, frequently others are contrary to reason, or even derive from a neo-pagan gnostic spirit which foundations are not only opposed to reason and good science, but to the principles of the Faith.

For example, while home births with a doula or midwife are certainly morally acceptable in themselves, there may be high-risk situations in which refusing ordinary medical intervention would be immoral by putting mother and child at unreasonable and unnecessary risk.

Many simple moral questions can be answered by reference to catechetical knowledge and the use of reason. Beyond this, however, there may be need to understand finer points of the moral doctrine of the Church or of the Natural Law, or what constitutes the ordinary or extraordinary means of treatment. Here the parish priest should be a resource for the faithful, presenting questions and concerns to him, seeking advice and directives.

This said, while all priests are trained in moral theology and Natural Law ethics, not all priests are experts on these subjects. When more complex bioethics, new procedures, or questions which have not been settled by the Church or addressed by many bioethicists or theologians arise, even priests must sometimes take advice. Ordination confers certain powers and places an indelible mark on a man’s soul but does not confer a doctoral degree or infused knowledge.

Certain priests, whether by means of higher-level education, or simply by deep study of bioethics, find themselves consultants for other priests when the principles or their application are not clear. Thus, the faithful may expect immediate answers from a priest to a complex moral problem, but good priests will know their limits and may refuse an immediate directive (outside of an emergency) and take time to consult more experienced or expert priests to obtain a reliable answer.

The application, whether by a parish priest or moral expert, is still an act of the virtue of Prudence, in which one tries to apply principles in view of the ultimate goal of the salvation of souls, using reason. As such, in certain cases, absolute certainty is impossible, and a priest can only provide moral certainty. Moral certainty is the kind of assurance where no reasonable doubt remains, even if it is possible to be wrong. In such a case, based on the best evidence at present, the advice one receives can be followed without risk of being culpable of sin in following it, even if it is wrong. This is particularly the case in the application of double effect. While on points of clear principles all well-trained priests will agree, on more rare edge cases, even solidly orthodox priests who are experts may come to different conclusions.

In such cases, where different moral experts disagree, the Church has made clear that the priest cannot bind the conscience of the faithful to his particular opinion. If there are well-established orthodox alternatives, one may legitimately follow these without fear of sin, even if it later is determined this action was not morally permissible.

Conclusion

The need for more priests is frequently spoken of from the standpoint of the Sacraments, but part of the role that the priest plays is also to help guide the faithful so as to remain on the straight path. Solid, holy men, well-formed in the Church’s moral theology are essential to this task. So too, however, is the modern world in need of well-formed laymen in medicine and other fields who can help to restore Christian moral principles to these fields.

Endnotes

¹ Rom. 3.8.

² St. Augustine. Enchiridion, ch. 11.

³ Cf. Aristotle. Nicomachean Ethics, bk. 5.

⁴ St. Thomas Aquinas. Summa Theologica, II:II, q. 64, a.7.

⁵ Ibid.

⁶ St. Thomas Aquinas. Summa Theologica. I:II, q. 97, a. 2, ad. 4.

⁷ St. Thomas Aquinas. Summa Theologica. I:II, q. 97, a. 2.

⁸ Hippocrates. Epidemics., I.11.

⁹ Boyle, Joseph M. “Towards an understanding of double effect.” Ethics, 90 (1980): 527-538.

¹⁰ Cf. Boyle, Joseph M. “Medical Ethics and Double effect: The Case of Terminal Sedation.” Theoretical Medicine and Bioethics, 25 (2004): 51-60.