Dear PD essay authors for whom I have an email address:

What your compelling short essay fails to address is the widespread sense of contamination by any sort of causal connection to evil. Our historical and contemporary sense of wrong stretches from unmindful causal connection at one end (a sword in the middle ages became a deodand – literally, a thing that must be given over to God – if it happened to fall and kill somebody) to the very refined homing in on intention that one finds in the writings of Grisez and Finnis.

An example of our continuing sense of causal contamination: we don’t feel very bad about negligence that happens not to cause any harm, but we would feel far worse about the same sort of negligence if by chance it killed someone. Indeed, we would feel terrible if we caused a death wholly by accident, without any carelessness at all on our part. Consider an Orthodox example: in the Divine Liturgy, one prays for forgiveness for all one’s transgressions “voluntary and involuntary.”

I submit that this sense of contamination by causal connection is a deep-seated part of the human psyche. Modern moral philosophy and moral theology, of course, do not justify this sense of (moral?) contamination by a merely causal connection to evil. But it must be addressed rather than just ignored. Otherwise, you are asking people to violate a deep sense of wrongfulness, making them more blasé about apparent wrongdoing in the future.

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Would you pooh-pooh a person’s hesitation to use HEK293 cells if they had been derived from tissue taken by Dr. Mengele in Nazi concentration camps? Wouldn’t it be healthy and good to have those qualms, even though there is no danger of the Nazis reconstituting concentration camps with another Dr. Mengele? (Of course, there is such a danger via one’s apparent approval of abortion, but that is not the point of this comment.)

— Richard Stith

Dear Richard,

Thanks very much for your thoughtful message. I understand that many people have strong feelings of moral repugnance in relation to the vaccines. This makes sense, given that abortion is a grave evil and that each of the vaccines has a connection (albeit extremely indirect and remote) to a past abortion.

Nevertheless, the presence or absence of moral repugnance is not sufficient to guide action. Particularly on very complex matters like this one, it’s necessary to assess and critically evaluate our feelings of moral repugnance, which (like all feelings) need to be educated and are not always an accurate indicator of reality. We should not aim to desensitize ourselves, but rather to educate our feelings of moral repugnance and direct them to their proper object—in this case, the abortion and the use of fetal tissue without proper consent or due respect for the dignity of the dead child. But because these evils are in the past and are not perpetuated by the current use of HEK 293, moral repugnance at the vaccines themselves is misplaced. My answer would be the same if the cell line were derived from the tissue of someone killed in a Nazi concentration camp.

The presence or absence of moral repugnance is not sufficient to guide action.


Not long ago, many good people felt a strong sense of moral repugnance at the idea of interracial marriage, a repugnance that was entirely unfounded. Likewise, when organ transplantation was first proposed, many people found this idea morally repugnant as well. Concerns about treating the mortal remains of human beings with dignity give those feelings some basis (unlike the repugnance at interracial marriage, which is the product of prejudice and has no rational basis at all). Still, once our feelings are educated through a rational evaluation of the moral issues at stake, we realize that there is no affront to human dignity in organ transplantation, presuming it is carried out with proper consent and that the donor is already dead when the organs are removed.

The book Alive, about the survivors of a plane crash in the Andes, recounts how, in order to avoid starvation, many ended up eating the flesh of those who had died in the crash. We rightfully feel repugnance at this, because it is almost always the case that eating the flesh of another human (even if that person is already dead) involves a failure to treat that person’s mortal remains with due respect and is an affront to human dignity. However, it seems to me that in a case where this is the only way for people to survive, eating human flesh is not wrong— indeed, it might even be morally obligatory, given the duty to use the legitimate means at one’s disposal to preserve one’s own life.

The moral frameworks of cooperation in evil and appropriation of the fruits of evil can help us evaluate the moral repugnance that we reasonably feel when our actions have some connection to past, present, or future evil.

The cooperation-with-evil framework is about determining when it is permissible to contribute to someone else’s present or future evildoing. Formal cooperation in evil, in which one shares in the evildoer’s intention, is always morally wrong. Material cooperation in evil, in which one someone facilitates the evil without sharing in the evil intention—as when, for instance, we invest in index funds supporting companies that donate to Planned Parenthood, without intending to facilitate abortions—may or may not be permissible, depending on how proximate and direct our connection is to the evil, and on whether or not we have a proportionately serious reason to engage in the action despite the fact that it unintentionally contributes to others’ evildoing. In cases of material cooperation, it is also necessary to avoid scandal by ensuring that others do not reasonably infer from your actions that you actually approve of the evil that you are knowingly but unintentionally facilitating, by making clear your opposition to the evil and seeking to work against it to the extent possible.

Strictly speaking, however, the cooperation-with-evil framework does not apply to the case of the COVID vaccines, because the evils we are concerned about occurred in the past, and nothing that we do now can change what happened. Some worry that the willingness to use the vaccines despite their connection to these past evils indirectly perpetuates the practice of using aborted fetal tissue to make new cell lines, by showing that consumers are willing to use products made with the help of these cell lines. I’m not convinced by this claim, given that the cell lines are immortal and that for scientific purposes there are huge advantages to using established cell lines with well-known properties. In other words, continuing to use an established cell line like HEK 293 on balance is actually most likely to reduce the demand for the creation of new fetal cell lines.

In this regard, it’s important to note the crucial difference between using fetal cell lines, which reproduce indefinitely, and the direct use of fetal tissue or human embryos in research. The latter does perpetuate these unethical research practices and indirectly contribute to more abortions and embryo destruction by creating ongoing demand for new tissue or embryos, but the former does not. At any rate, even if it were true that willingness to use the vaccines in some way encourages the practice of using fetal tissue to create cell lines, it would do so in an extremely small, indirect, and remote way.

A better framework for assessing the permissibility of taking the COVID vaccines is the appropriation framework, which considers the conditions under which it is morally permissible to benefit from past evil. According to this framework—developed by Cathleen Kaveny and widely accepted among ethicists—appropriating the fruits of past evil while approving of that evil involves ratification of the evil and is always wrong, just like formal cooperation. But appropriation can be problematic even when there is no ratification of the past evil, because benefitting from evil involves a risk of corrupting our character by desensitizing us to that evil and/or weakening our opposition to it. Thus, proportionate reasons are necessary in order to accept these risks of character corruption that are involved in benefiting from evil. We are also obligated to make a conscious effort to avoid these risks by renewing our opposition to the evil and taking steps, when possible, to prevent similar evils from happening in the future.

In the case of the vaccines, the existence of proportionate reasons is obvious, given the crucial importance of widespread vaccination in order to achieve herd immunity, which is the only thing that will enable everyone—including the vulnerable, who may not be able to receive the vaccine for health reasons—to resume normal social and economic life. Still, as the appropriation framework indicates, it is important to renew one’s opposition to the evil of abortion and to continue to make efforts to put an end to abortion. Those who can do so should also lobby for an end to the direct use of aborted fetal tissue in research and push for the development of protocols to obtain fetal tissue ethically from spontaneous miscarriages, nonviable pre-term births, etc., with proper consent from the child’s parents.

— Melissa Moschella

Thank you, Melissa, for your well considered response. Although I think it useful as a quick rule of thumb in new situations, I agree with you that our sense of repugnance should not go unquestioned. And there is nothing in your reasoning or conclusions with which I disagree. Our repugnance can be erroneous, even sinful, in the case of interracial marriage, and so it should be educated. And, for what it’s worth, my wife and I have each received two doses of the Moderna vaccine (and, having then waited two more weeks, we are breathing a little easier).

Nevertheless, I would like to raise three points of caution here.

First, it is important that erroneous repugnance be overcome by proper moral education, not by a sense that scruples shouldn’t really matter much when a strong self- or social interest is at stake. I don’t think an understanding of this difference can be taken for granted in today’s society and today’s media. In communicating that the vaccines are permissible, it is important that one avoid phrases and sentences that can be taken out of context to imply that one should overlook morality when push comes to shove. I would think it also advisable to mention that (insofar as one’s duties to oneself and one’s neighbors permit) going beyond the call of duty is admirable rather than reprehensible. That is to say, it could be that refusing to be vaccinated with a tainted vaccine, even a permissible vaccine, would be an admirable witness for life in our current circumstances. The good of our neighbors and of society goes beyond physical well-being and health. The need to send a pro-life message is greater than ever at this time. That should figure into any measure of what the Common Good requires in our day. All this seems to me in line with what the US Catholic bishops have said.

In communicating that the vaccines are permissible, it is important that one avoid phrases and sentences that can be taken out of context to imply that one should overlook morality when push comes to shove.


Second, I don’t think that our natural repugnance at causing evil or to being associated with something that has caused harm or evil is likely to go away with proper education. It lies too deep. Might you not agree that it was better not to put the thirty pieces of silver back into the temple treasury? Moreover, causal contamination is an intuition that is constantly being renewed. We don’t drive carefully in order not to hit someone negligently. We drive carefully simply in order to not hit someone. Period. Hitting someone is the evil we are seeking to avoid, habituating ourselves to avoid. It is only after the fact, when the question of punishment or damages comes up, that we turn to examine our own subjective mental state at the time of the accident. And, frankly, we would not object very strongly to a rule of mild strict liability here, e.g., to a rule that required us to pay some damages simply for causing harm (even without any moral culpability on our part). Interestingly, the common response to such a situation would be an attempt at the sort of moral education that you appear to recommend, Melissa: we would seek to comfort the devastated driver with these words, “Hey, it wasn’t your fault!” The driver would probably respond something like this, “I know, but I was the driver.” (A passenger who had witnessed the whole accident would not feel nearly as bad.)

Third, I think there is something true about our root intuition of causal contamination here. A sword that has killed has acquired a downside. Whenever we cause harm, we learn that our personal existence, our life, has a downside. The life we live has costs, namely, the unavoidable as well as the culpable harms that we cause. Just as we want to leave a legacy of good results, not just of good intentions, I submit that we want to leave a legacy of minimal harm, not just of minimal culpability.

— Richard Stith

Dear Richard,

I agree that our natural moral repugnance to causing evil or being associated with something that has caused evil is unlikely to go away. Indeed, I don’t think that it should go away (except in cases where our repugnance is sinful). Rather, one of the key concerns about appropriation of the fruits of evil is that it could lead to a corruption of moral character by desensitizing us to the past evil from which we are benefitting and making us think at least subconsciously that perhaps it wasn’t such a big deal after all.

That sort of desensitization is something that we have an obligation to guard against whenever we benefit from past evil, be it living on land unjustly taken from Native Americans, making use of medical knowledge obtained through Nazi experimentation, or using products like vaccines—or the multitude of other products lining the shelves of our grocery stores and pharmacies—that were made with the help of abortion-derived cell lines. Part of the way that we do that is by making sure to remind ourselves of that past injustice and recommit ourselves to stopping or preventing similar injustices now or in the future. In that regard, I think that a consideration of what is likely to be the most effective use of limited resources to fight the injustice is important: wouldn’t direct efforts to restrict abortion, to address the underlying causes that lead women to seek abortions, to support women in crisis pregnancies, or to lobby for more ethical research practices be much more effective than objecting to a vaccine that has only an extremely remote connection to a past abortion?

Regarding your points about causal contamination: on the one hand, it’s not clear that the case of the driver is a good analogy to the case of vaccination, because (as I already argued) being vaccinated is not causing (even remotely or indirectly) anyone’s death. But of course your point in bringing up this case was a more basic one about the fact that we feel responsible for evils with which we are causally connected. In the case of the non-negligent driver who hits someone, I think that the guilt is largely a function of the fact that we always know we could have been more careful, even if we were driving safely. What counts as negligence depends on what we consider to be reasonably safe driving. Nonetheless, it’s still not unreasonable to recognize that perhaps being slightly more attentive or driving just a bit more slowly might have prevented the accident. At any rate, the guilt a driver naturally feels in this situation still, like all moral feelings, needs to be educated; fostering that guilt when in fact one was not negligent is unreasonable.

At a deeper level, to feel that we are responsible for all of the effects of our actions—even those effects that are not reasonably foreseen or that we take steps to avoid—seems to me ultimately to be a matter of wanting to have a level of control over the outcomes of one’s actions that is proper to God, not to human beings. As creatures, we are called never to will evil directly, and to use our best lights to act in ways that promote human well-being and avoid doing harm, in accordance with our particular vocations, commitments and obligations. Beyond that, we are called to trust that God in his providence will take care of the rest.

A final thought: it seems unreasonable to me that so much concern is being expressed regarding the use of HEK 293 in the development, production, or testing of the COVID vaccines (and so much repugnance felt in this regard), when almost no one seems to have significant moral qualms or feel strong moral repugnance about buying and using other pharmaceutical products, processed foods, and beauty products, the vast majority of which were probably developed and/or tested using HEK 293 cells. Yet for the most part, refraining from buying or using such products would, unlike refusing vaccination, in no way endanger others or undermine the common good. Thus, while I agree that witnessing to the pro-life message is indeed an important and crucial contribution to the common good, I believe that there are countless ways to do so that would involve no indirect harms to others and be much more direct and effective than refusing vaccination.

— Melissa Moschella