Saint Thomas Aquinas and the Quandary of Technical Progress

The following paper was presented at St. Matthew’s Church, Oakville, on January 28, 2012, for the Communio Circle of the Diocese of Hamilton in honour of the Feast of St. Thomas Aquinas:


Saint Thomas Aquinas (1223-1274) was one of the greatest figures, if not the greatest figure, during the period of scholasticism in the 13th century. His greatest work, the Summa Theologica, often just called the Summa, was a compendium of the whole of theology. We can identify at least three characteristics of Thomas’ moral theology, as represented in the Summa: 1) that our journey in search of happiness leads us to seek God; 2) the way of the theological virtues renders God present to us; and 3) that the evangelical law of the Gospel is not something externally imposed but rather a dynamic inner principle of moral living. Although Thomas is known for integrating Aristotle into Christian theology, his primary sources were the Scriptures and the Church Fathers. According to Thomas, it is the grace of the Holy Spirit that enables us to make an interior act that is good. It follows that Thomas placed more importance on virtues than natural law, and more emphasis on the Beatitudes than the Ten Commandments (Bohr 66-77). Thus, it was Saint Thomas’ systematization of moral theology that established the place of the virtues in classic Catholic theology (Bohr 203). The theologian Servais Pinckaers wrote in his Sources of Christian Ethics that “St. Thomas’ moral system was therefore one of virtues and gifts. It dealt with sin only as the negation of virtue and saw legal precepts and obligations as aids to virtue”.

One of the ways the virtue ethics of Saint Thomas continues to influence Catholic moral theology can be found in the contemporary use of the principle of double effect, which was derived from his treatment of self-defense in the Summa.

The Legacy of Question 64. on Justice and Murder

Within the Second Part of the Second Part of the Summa Theologica, in the section on murder within the section on justice there is a question about self-defense, that is, “Whether it is lawful to kill a man in self-defense?” (Summa Theologica II-II, Q. 64, Art.7) Thomas writes, “Nothing hinders one act from having two effects, only one of which is intended, while the other is beside the intention. Now moral acts take their species according to what is intended, and not according to what is beside the intention, since this is accidental as explained above (43, 3; I-II, 12, 1). Accordingly 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.” This is the basis for what would later be called the principle of double effect. What follows in the text provides qualifications on the basic principle. (See handout.) The contemporary need to consider double effect arose primarily with the development of medical techniques that caused unintended harm as they saved lives.

Double Effect and Conscience

In their widely studied book Health Care Ethics: A Theological Analysis, Benedict M. Ashley, O.P. and Kevin D. O’Rourke, O.P. introduce the principle of double-effect in the situation when a person judging with a correct conscience may find that their action results in undesirable side-effects along with the intended effect.. In doing so they try to avoid what they call moral “purism” or “rigorism,” which would be the case if the moral agent insisted that all actions must be performed with only good effects and without any foreseen harmful effects. They say that such a standard would make it nearly impossible to act at all and may even result in sins of omission when one neglects one’s moral responsibilities to other for the sake of one’s own moral purity. To avoid rigorism and still act in a morally responsible manner, they present the principle of double effect as a way to form a good conscience when judging an act that is foreseen to be both beneficial and harmful. They provide five conditions for the application of the principle of double effect:

  1. The directly intended object of the act must not be intrinsically opposed to one’s commitment to God and neighbour, which means that the object must be good, not evil.
  2. The intention of the agent must be to achieve the beneficial effects and to avoid the foreseen harmful effects as much as possible.
  3. The foreseen positive effects must not be achieved by means of the foreseen negative effects and be not achievable without them.
  4. The foreseen positive effects must be equal to or greater than the foreseen negative effects.
  5. The positive effects must follow from the action at least as immediately as the negative effects (191).

They point out that the fourth condition ensures that one actually intends the positive effects, which seems to address the concern of the moral rigorism. Yet they point out that this condition is sometimes framed as “the good must outweigh the evil effect,” which they caution can lead to an unacceptable proportionalist justification for committing a intrinsically evil act for the sake of the perceived benefits (191-192). In fact, without the preceding conditions that ensure a good object and good direct intention, the principle of doubt effect would collapse into proportionalism of a utilitarian fashion. Thus, we can say that the principle of double effect articulated by Ashley and O’Rouke is consistent with and supports the traditional Catholic understanding of moral-decision making based upon a correct and certain conscience.

As a common application of the principle of double effect, Ashley and O’Rouke, provide the example an operation to remove the cancerous uterus of a pregnant woman that will also kill her unborn child. The physician rightly decides that the operation is morally permissible because:

  1. the first condition is meet by the direct intention to save the woman’s life,
  2. the second condition is met insofar as the child would saved if possible,
  3. the third condition is met by the fact that the removal of the cancer is the means to save the woman’s life, not the death of the child,
  4. the fourth condition is met by the life of the mother being equal to the life of the child,
  5. and the fifth condition is met by the child being removed along with the uterus, as opposed to the child being killed before removing the uterus (Fifth Edition 55).

However, it can be shown that the first condition of the principle of double effect is the essential one, that is, that the direct intention must be good, and that the other four conditions are ways of ensuring that the first is being met in any particular case. Ashley and O’Rourke describe the principle of well-informed conscience as the “work of the virtue of prudence enlightened by faith” (183). They propose that someone engaged in making an ethical decision is obliged to:

  1. Inform themselves about both the facts and the relevant ethical norms;
  2. Make a morally certain judgment of conscience based on this information;
  3. Act according to this well-informed conscience; and
  4. Accept responsibility for one’s actions (183).

They also explain that a well-informed conscience requires information based upon one’s own experience as well as from various experts and that it requires guidance that only God can provide us (183). Yet they acknowledge that there is no guarantee that someone who acts in accordance with these moral obligations will achieve their goal in a morally acceptable manner. They state that goals are not accomplished by good intentions but by taking practical steps. Here their discussion takes on the form of the traditional three-font principle of object, circumstances and end. As an illustration they describe a person who is caring for a patient. The object is bandaging the patient’s wound, the circumstances include the hospital setting during the day shift and the end is the love of God and neigbour. In this illustration there are no extenuating circumstances that might alter the morality of the action taken. While the circumstances can make a morally bad action worse and can make a morally good action better, they cannot turn a morally bad action into a good one. As far as we can ascertain, this care giver is judging and acting with a correct conscience (189-190). As we will see, however, the introduction of technological ambivalence complicates assessment of the circumstances.

Unintended Negative Effects

In the 1920s, Thomas Midgley, an American engineer, discovered that internal combustion engines run more smoothly when tetraethyl lead is added to gasoline. At that time lead was already being used to make water pipes for homes and in the manufacture of household paints. In the 1950s, researchers discovered that lead causes nervous system and kidney damage in adults and causes developmental defects in children. In the 1960s, governments began banning use of lead in water pipes. Most new piping installations were using copper by that time anyway. Yet lead solder was still used to join these copper pipes. Lead solder was not banned until some years later. The use of lead paint in schools was restricted around this time. However, most governments did not ban its use in paint until the 1970s. Governments did not require the manufacture of car engines that use unleaded gasoline until the late 1970s. When I was a teenager in the 1980s I remember there being both leaded and unleaded gasoline pumps. I also remember learning about the toxic effects of leaded gasoline and feeling uneasy while filling up my vehicle with it. Prior to learning about the toxic effects, I had no qualms about using leaded gasoline. However, once I knew about the facts, it pained my conscience. I would stand there at the pump and tell myself that I had no choice. Moreover, I had good intentions. I used the vehicle to go good things like pick up groceries for my mother and I helped out my father by driving my brother to places like school. Hence, I concluded that it was not morally wrong for me to use leaded gasoline. Nevertheless, it was a great relief for my conscience when my parents purchased a new vehicle that used unleaded gasoline. Since that time I have learned more about the complexities of moral decision-making. When I now look back at my use of leaded gasoline I have to ask myself some hard questions: Did I act in good conscience? Did I really have no choice? Was my use of the technology an evil act? Was it sinful? These are the same questions I ask myself today when I try to exercise my conscience and ponder my use of other technologies in light of what I now know about their unintended negative effects. As an engineer, I also wonder about the moral culpability of technical experts like Thomas Midgley. Since that time I stood perplexed at the pump I have also learned about the moral principle of double effect and the technological principle of ambivalence. Yet over the years I have not come across a single work in philosophy or moral theology that takes into account how conscience, double effect and ambivalence might come together when making moral decisions about our use of technologies.

The Principle of Technological Ambivalence

In The Technological Bluff, Jacques Ellul introduces the concept of technological ambivalence by trying to explain that technical progress has made moral decision making more complicated than many philosophers and moral theologians realize. In his previous works he has tried to demonstrate that technique has good and bad effects. Yet people assume that his point is that technique can be used for good or bad ends depending upon the use one makes of it. A typical illustration put forward by those who do not understand his point is that a knife can be used to peel an apple or to kill one’s neigbour. Assuming non-mitigating circumstances, we assume that peeling an apple with a knife is a good object with good intentions and that the stabbing one’s neighbour with that same knife is a bad object with evil intentions. Ellul would agree with this moral analysis concerning these objects, circumstances and ends. Nevertheless, he points out that, in light of technical progress, this is now a simplistic view. It assumes that the technique, that is, the means, is morally neutral with regards to use. However, with technical progress we have created a new kind of means that has both positive and negative effects regardless of use (35). He insists that technical progress is neither good, nor bad, nor neutral. Rather it is ambivalent, that is, both good and bad (37). Therefore, I suggest that we must come to appreciate that technical progress has irrevocably changed the circumstances of moral decision-making.

Ellul characterizes technological ambivalence by making the following five observations about technical progress:

  1. All technical progress has a price (i.e. technological tradeoff).
  2. Technical progress raises more and greater problems than it solves (i.e. drawbacks).
  3. The harmful effects of technical progress are inseparable from its benefits.
  4. Technical progress has a number of unforeseen effects.
  5. The positive results of technical progress are immediate while the negative effects are long term (and only become apparent with experience).

Ellul makes these claims having performed extensive research into the actual effects of new technologies as opposed to their intended effects. His studies include the psychological price paid by workers who undergo industrialization (41-43), the problems of arms proliferation and the disposal of waste raised by the development of nuclear energy (48-49), the inseparability between congestion and the increased use of automobiles (57), and the unforeseen effects of thalidomide and DDT (65).

Many of Ellul’s examples may seem dated to us. We may even assume that technical progress itself has, or someday will, enable us to avoid these problems and predict effects before products go to market. Yet this is simply not case. There is no evidence that concerns of this nature have decreased in the past fifty years. Edward Tenner, in his book Why Things Bite Back: Technology and the Revenge of Unintended Consequences, demonstrates that ambivalence is still very much with us. In fact, it continues to be the reality with the development of antibiotics , whereby antibiotics first invented in the 1950s caused the development of more resistant strains of bacteria that spurred the development of even stronger antibiotics that in turn have caused even more resilient and lethal bacteria to attack us today (58-61). Tenner calls this the “revenge effect” (5). Although I do not agree with his anthropomorphization of the phenomenon, his analysis of ambivalence is very thorough. He basically picks up where Ellul left off by discovering other areas of technical progress that continue demonstrate how new technologies generate more problems than what they originally solved. One of his more interesting ones involves changes in office work whereby the replacement of the typewriter and filing cabinet by the computer has resulted in a number of chronic problems such as repetitive strain injuries that were avoided when secretaries used to have to use various motions to type and had to get up from their chairs to file their work in folders (161-183).

Ambivalence and Moral Decision-Making

At first glance it would appear that ambivalence does not impact upon our application of the principle of double effect when making a moral decision in good conscience. After all, the principle emphasizes foreseen effects while ambivalence highlights unforeseen effects. However, when we take Ellul’s observation that the positive results of technical progress are immediate while the negative effects are long term, it means that time and time again a new technology is introduced to solve a problem but it is only after its use has become common place that its negative effects become apparent. As a result, we must expect the unexpected. In other words, we must see the obligation to be informed as described by Ashley and O’Rouke not simply to mean that we inform ourselves the first time we use a technology but we must continue to keep ourselves informed about previously unknown negative effects. Once negative effects become apparent we must re-evaluate the conditions of double-effect in light of these new circumstances. The first condition of double effect should not change, for presumably the object of the act has not changed and remains good. However, the second condition is altered somewhat. Although one’s intention to achieve the benefits presumably has not changed, in light of ambivalence and the inseparability of the harmful effects from its benefits, it may no longer be possible to avoid the now foreseen harmful effects. As for the third condition, it is clear that the positive effects are not achievable without the negative effects. However, in light of ambivalence and price of technical progress, it may be more difficult to rationalize that the positive effects are not achieved by means of the now foreseen negative effects. As far as the technology is concerned, there is no such thing as a “side-effect.” The use of a technology to solve a problem always results in multiple effects. It is our intentionality that determines which ones are direct and which ones are indirect. Sometimes a technology is developed with one purpose in mind but once a “side-effect” becomes apparent it is then sold to solve another problem. One of the most famous cases of this double-use of technology occurred when Pfizer Pharmaceuticals was doing trials on a heart medication for men. After the trials a number of the men asked if they could receive further samples of the drug. When it was discovered that a “side-effect” was an increase in erections, the company re-marketed the drug as Viagra. As for the fourth condition, here is where the ambivalence exerts the greatest challenge to the consideration of double effect in Catholic moral theology.

The fourth condition of double effect states that the foreseen positive effects must be equal to or greater than the foreseen negative effects. However, in light of ambivalence and the consideration that technical progress raises more and greater problems than it solves, this will likely no longer be the case once unforeseen effects are discovered. When I learned that lead causes nervous system and kidney damage in adults and causes developmental defects in children, the circumstances of driving a car that used leaded gasoline changed for me. This in turn changed the certainty of the proximate moral truth that I was doing no harm to others while driving my car. It is true that the harm was not intended. However, I was still faced with a moral dilemma. Should I continue to drive even though there were now foreseen negative effects? At the time, I exercised my practical reason to judge that I had no choice but to continue driving my parents’ vehicle. I made it their responsibility to purchase a new vehicle that used unleaded fuel. Today I own my own car. It uses unleaded fuel. However, I now know that emissions from my car exhaust contribute to the death of thousands of Canadians each year who suffer from asthma. Moreover, my car emissions may also be contributing to global warning. These are most definitely greater problems than I use my car to solve. As a result, I now have to consider the object of the act of using my car before I turn the ignition key. In order to maintain a good conscience, at the very least I must avoid using my car for frivolous purposes. In our technological society, we face these kinds of circumstances everyday. Many of us choose to believe, like I did when I was a teenager, that we have no choice but to use our technologies. We may also choose to believe that these moral problems will be solved through government regulation. However, as we have seen it took the Canadian government almost thirty years to phase out the use of leaded fuels. We may be able rely on our government to regulate the harmful effects of technologies in the long term, but what are we supposed to do in the meantime. In order to avoid an erroneous conscience should we not take matters into our own hands and limit our use of the technology when we learn of its unforeseen “side-effects”?  I think we should. I think it is morally irresponsible to rely on government regulation. The fact is that racing cars are exempted from the Canadian ban on leaded fuels. If you are a fan of racing car competitions, you should consider whether this is a frivolous use of the technique and re-evaluate your support of the sport. We may also be tempted to rely on the professionals who use these products to make these decisions for us. However, painters continued to use leaded paint for years after the negative effects became known and I’m sure many plumbers decided to use up their stash of lead solder even after lead pipes were replaced by copper pipes. I also suspect that many dentists used up their stock of lead filing after they learned of the negative effects and may even have continued to purchase it right up until it was banned. We certainly cannot rely on the developers of new technologies to have the foresight to ask themselves about the negative effects of their inventions.

In the 1930s, Thomas Midgley developed Freon, a non-toxic and nonflammable gas that could be used in refrigerators, air-conditioners and aerosol cans. At the time he addressed people’s concerns about its safety by demonstrating its apparent harmlessness. He would fill his lungs with the vapour, exhale it and extinguish a candle. Decades later, the destruction of the ozone layer was traced to Freon and similar chlorofluorocarbons. We will never know why he did not think about where these inert cases would go when they were released into the atmosphere. CFCs are banned inCanadabut they are still used in old equipment and in many other countries where they cannot afford the safer alternatives.

Since we cannot be assured the developers of technologies to make moral decisions about their use, we must take moral responsibility for our use of technologies into our own hands. As we have seen, however, we can no longer rely solely on the principle of double effect to inform our conscience.

What Would Thomas Do?

Technical progress does not simply introduce hazardous technologies; it introduces new kinds of technologies. When Thomas Aquinas formulated what became known as the principle of double effect he was dealing with the issue killing in self-defense. The object is disarming the aggressor and the intention is the preservation of one’s own life, not the death of the other. The circumstances include conflict between two people, one who is acting aggressively towards another, not combat between two soldiers of opposing armies. If the person under attack picks up a knife, he or she is exercising practical reason in making a moral judgment. He or she is also exercising practical reason to solve the practical problem of wheedling the knife to achieve his or her goal. Such is the nature of the use of practical technologies like knifes and other tools. However, with technical progress, our technologies are changed from being practical tools that we command in our hands to technical devices that we try to control with our minds. I suspect that Thomas would conclude that practical tools are neutral insofar as we can guide them with our intentions and we can develop proximate moral truth concerning their use based upon our own experience. In the case of technical devices, we must rely on the scientific research of others to discover the unintended negative effects. In swallowing a pill there is no way to exercise skill in order to avoid the negative side-effects of the drug. (It is interesting to note that pharmikon was the ancient Greek word for both medicine and poison.) The use of technical devices and techniques requires us to exercise our technical reason to minimize side-effects and our practical reason to make a moral judgment in good conscience. However, we may feel that we have no choice but to use a technology we have discovered is unintentionally harmful and may be creating greater problems than the ones we use it to solve. Hence, we may be tempted to raise our arms in despair. We may even consider our current situation of runaway technical “progress” as absurd for it seems undermine our intentionality and agency. This was the conclusion of Ivan Illich, who took responsibility for his own health by opting out of the health care system.

What would Thomas do if he learned of an unforeseen negative effect from a technical device that he had become dependent upon for his day-to-day living? Perhaps he would consider Question 64 Article 7 where he states that:

“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. 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, because according to the jurists [Cap. Significasti, De Homicid. volunt. vel casual.], ‘it is lawful to repel force by force, provided one does not exceed the limits of a blameless defense.’” When we use a technology that has positive immediate effects but causes greater problems for the common good than it solves for the individual in the long-term, is its continued use out of proportion to the intended end? While Thomas may agree with this application of Question 64 Article 7 to our current circumstances, he may just as well say that he never intended that his defense of self-defense be used to grapple with the quandary of technical progress.

I will not propose to know the mind of Thomas. However, I suspect that he would not fall into despair. He would maintain his hope in Jesus Christ. Nevertheless, while we are living in eschatological times as we await the Second Coming, this must not become our Christian cop out. (There is a play showing inToronto about ecological disaster and the Christians are portrayed as doing nothing because they believe that Jesus will save them.)

In his encyclical Veritas in caritate, “On Integral Human Development In Charity and Truth,” Pope Benedict writes:

“Technology, viewed in itself, is ambivalent. If on the one hand, some today would be inclined to entrust the entire process of development to technology, on the other hand we are witnessing an upsurge of ideologies that deny in toto the very value of development, viewing it as radically anti-human and merely a source of degradation. This leads to a rejection, not only of the distorted and unjust way in which progress is sometimes directed, but also of scientific discoveries themselves, which, if well used, could serve as an opportunity of growth for all. The idea of a world without development indicates a lack of trust in man and in God. It is therefore a serious mistake to undervalue human capacity to exercise control over the deviations of development or to overlook the fact that man is constitutionally oriented towards “being more”. Idealizing technical progress, or contemplating the utopia of a return to humanity’s original natural state, are two contrasting ways of detaching progress from its moral evaluation and hence from our responsibility.” (14)

Pope Benedict insists that there is a third-way between the utopian ideology of salvation by technology and the romantic ideology of the complete rejection of technology. He also explains that:

“The key to development is a mind capable of thinking in technological terms and grasping the fully human meaning of human activities, within the context of the holistic meaning of the individual’s being. Even when we work through satellites or through remote electronic impulses, our actions always remain human, an expression of our responsible freedom. Technology is highly attractive because it draws us out of our physical limitations and broadens our horizon. But human freedom is authentic only when it responds to the fascination of technology with decisions that are the fruit of moral responsibility. Hence the pressing need for formation in an ethically responsible use of technology. Moving beyond the fascination that technology exerts, we must reappropriate the true meaning of freedom, which is not an intoxication with total autonomy, but a response to the call of being, beginning with our own personal being. ” (70)

The Pope also insists that actions by remote control and through communications networks are still human work. In other words, whether we are solving practical problems with our skilful agency or technical problems by way of push-button causality, we may be caught in a machine-like environment but we are not machines. We are human beings who must take responsibility for our free actions. We may not be able to control unforeseen negative effects or control society’s use of technologies that have proven to be harmful. Yet we can exercise our agency in making informed moral decision about our use of technologies and try to limit our use of ones we know have harmful effects. When it comes to double effect, the primary moral question concerns how to use a technology; when it comes to ambivalence, the primary moral question is how much to use a technology.


Since the Reformation we have seen that Catholic theologians have tended to be open to the use of reason and embrace culture while Protestant theologians have tended to be suspicious of reason and more likely to turn to biblical revelation for answers to our contemporary problems. This confidence in reason was evident at the Second Vatican Council in the document Gaudium et spes. By associating the dignity of the intellect, truth and wisdom with progress made in technological development, Catholics may be somewhat blinded to the need for a reassessment of our use of practical reason in today’s technological environment. In this regard, we can learn much from the analysis of Protestants like Jacques Ellul without adopting their exclusively biblical approach to moral theology. We can also draw upon our tradition of personalism for the sake of culture and integrate our concerns for the dignity of the human person with concerns about the technological systems we have created for meeting needs like health care, transportation and communication. Yet I say we can and must find ways to form our conscience to take into account both the moral principle of double effect and the technological principle of ambivalence.

Thomas insisted that good intentions are essential. However, he also pointed out that they are not enough. We must maintain intentionality as our primary moral consideration while taking into account technological ambivalence without allowing our decisions to be solely determined by the unintended consequences of technical progress. In order to act in good conscience, we cannot ignore what might be called the “cumulative proportionality” of the unintended negative effects produced by our use of a technology in combination with thousands of other users. As we look more closely at the teaching of Thomas for guidance in our present situation, I suggest that we do well to recall that the problem of self-defense was taken up under his broader concern for justice.

For example, when someone claims the principle of double effect to justify their use of a technology, I suspect that Thomas would try to determine by what authority they act? Even if we justify our actions as individuals, we still need to take into account how cumulative negative effects may constitute social injustice, especially when those who benefit are different from those who are harmed. In the same way that moral theologians in the past turned to Question 64 Article 7 to develop the principle of double effect to deal with moral dilemmas arising from our use of medical procedures, perhaps its time for moral theologians to turn to Thomas once again and take another look at how he might help us deal with the quandary of technical progress.

Works Cited

Ashley, Benedict M. and Kevin D. O’Rourke. Health Care Ethics: A Theological Analysis. Fourth Edition. Washington: Georgetown University Press, 1997.

Aquinas, Thomas. Summa Theologica.

Pope Benedict XVI. Caritas in veritate. Encyclical Letter on Integral Human Development in Charity and Truth. <>, 2009.

Bohr, David. Catholic Moral Tradition.Huntington: Our Sunday Visitor, Inc., 1999.

Ellul, Jacques. The Technological Bluff. Trans. Geoffrey W. Bromiley.Grand Rapids: William B. Eerdmans Publishing Company, 1990.

Gaudium et spes. Pastoral Constitution on the Church in the Modern World. <>, 1965.

Tenner, Edward. Why Things Bite Back: Technology and the Revenge of Unintended Consequences.New York: Alfred A. Knopf, 1996.


Creative Commons License
This work, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
This entry was posted in Paper, Talk. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *


You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>