Last Updated on April 9, 2021

The standard pro-life argument against the legalization of abortion is based on the premise that fetuses are persons, combined with the widely held view that it should be illegal to kill persons. Since abortions kill fetuses, it follows that abortions should be illegal. Roughly speaking, the standard pro-life argument can be given in syllogistic form as follows:

1. Fetuses are persons.
2. It should be illegal to kill a person.
3. Abortion kills a fetus.
4. [from 1 and 2] Therefore, it should be illegal to kill a fetus.
5. [from 3 and 4] Therefore, abortion should be illegal.

The argument here is clearly valid. Yet many people (pro-choicers) disagree with the conclusion. Therefore, the debate between pro-lifers and pro-choicers must revolve around the truth of some of the premises. The majority of the abortion debate seems to revolve around premise 1, whether the fetus is a person. These debates often involve complex philosophical questions regarding  consciousness, sentience, vagueness, etc. and scientific questions regarding when certain features become present in the fetus. While these disputes are important, I fear they may be practically irresolvable. Fortunately, I think progress can be made in the abortion debate (in favor of the pro-choice position) by sidestepping these disputes. For the sake of argument, I’m willing to grant premise 1 of the pro-life argument, that fetuses are persons. I’m also willing to grant premise 3 as well (even though some pro-choicers argue that abortions do not kill fetuses; they merely result in the death of fetuses).

Because I reject the conclusion of this argument and because I have granted premise 1 and premise 3, I must reject premise 2 of this argument. I think a good argument can be given to show that premise 2 is false in the case of abortion. By “good” argument, I mean an argument based on principles that cohere with our shared considered intuitions better than principles supporting any pro-life conclusion. More specifically, I believe that premise 2 can be shown to be false from intuitions that even most pro-lifers hold. If I am correct, then most pro-lifers should reject the pro-life position (assuming they are pro-life because of arguments similar to the standard pro-life argument given above).

Reformulating Premise 2

Now, as it stands, premise 2 is clearly untenable if given a conclusive formulation, because there are plenty of exceptions to its conclusive form: killing a person in order to prevent that person from killing someone else (defense), killing a person with their consent to relieve them of extreme suffering, killing a person to relieve them of extreme suffering even if they are unable to communicate their consent, killing enemies during war, etc. So premise 2 clearly needs to be modified in order to not produce a strawman pro-life argument. Does this mean that premise 2 should be modified to include all exceptions? E.g. should premise 2 say, “It should be illegal to perform any action that involves killing a person unless it is killing in self-defense or killing to relieve someone of extreme suffering or killing in war or…“? There are a few reasons why we shouldn’t do this. Firstly, there could in principle be an unbounded number of exceptions to any conclusive formulation of premise 2 and I don’t think we should ever be confident that we have accounted for all of them. Secondly, and more importantly, we should avoid a conclusive formulation because – if the principle has not accounted for all exceptions – this allows a pro-choicer to technically refute the argument given against abortion without actually defending abortion from the argument given. For example, imagine a pro-choicer rejected the conclusion of the above argument by noting an exception to premise 2, namely that it should be legal to kill someone with their consent to relieve them of extreme suffering. While this technically refutes the argument given against abortion (by showing the argument to be unsound), it does nothing to actually defend abortion from the argument given, because abortion is never done with the fetus’s consent.

Instead, I believe the appropriate modification for premise 2 is to formulate it, not as a conclusive principle with a list of exceptions, but rather as a prima-facie principle. By “prima facie” principle, I mean that premise 2 entails we should outlaw any action that involves killing unless one can show an overriding principle that explains why that specific action should be legal. I borrow the definition of “prima facie” as it is used in legal contexts where it refers to “a lawsuit or criminal prosecution in which the evidence before trial is sufficient to prove the case unless there is substantial contradictory evidence presented at trial” (famous philosopher W.D. Ross appealed to prima facie duties in his moral framework). Formulated in this fashion, the pro-choicer can only technically refute the argument by actually defending abortion, since one would need to provide some positive principle or reason that applies to abortion which overrides the prima-facie principle against legalizing killing. So premise 2 should be formulated as follows:

• Anti-Killing Principle (AKP): there is prima-facie reason to outlaw any action that kills a person.

Now this is clearly acceptable. Pro-choice advocates should also accept this. To deny that there is prima-facie reason to outlaw killing would be a huge bullet to bite. However, accepting AKP doesn’t commit one to the pro-life position because AKP merely establishes a prima-facie, rather than conclusive, reason to outlaw killing. The pro-choice advocate should grant AKP but argue for a defeater of AKP that justifies the legalization of abortion. When I say “defeater” for a principle, I simply mean a further principle that overrides the original principle in certain specified contexts (see the SEP article on defeasible reasoning). This is what I will argue in this post. More specifically, I will argue that AKP is defeated by another principle in the case of abortion. And I will do so by appeal to intuitions accepted by the majority of pro-lifers.

Bodily Integrity

My argument is basically an extension of Judith Jarvis Thomson’s famous violinist thought experiment in “A Defense of Abortion“. Thomson asks us to imagine that you wake up and find that you’ve been kidnapped with your kidney’s hooked up to a famous violinist’s circulatory system. The violinist has a fatal kidney ailment and your kidneys are needed to extract poisons from his blood. The violinist will fully recover in nine months so long as you do not prematurely disconnect. Thomson here is mainly concerned with the moral permissibility of disconnecting from the violinist and of abortions. However, this thought experiment can also be used to show that abortions should be legal (quite apart from whether they are morally permissible). It seems that it should be legal to disconnect from the violinist in this thought experiment because the violinist, while he is a person with a right to life, does not have the right to use your body. Likewise, we should also conclude that abortions should be legal because the fetus, while it is a person with a right to life, does not have the right to use the mother’s body.

While such an example may seem fantastical, McFall v. Shimp was an actual court case concerning whether to force someone to donate bodily tissue to save someone else’s life. Because of a rare bone marrow disease, Robert McFall required a bone marrow transfusion in order to avoid certain death. The only available match for the transfusion was McFall’s cousin David Shimp. Unfortunately for McFall, Shimp refused to undergo the procedure, which prompted McFall to sue his cousin in an effort to force him to donate his bone marrow. The court ultimately ruled that Shimp had the right to refuse the transfusion. Judge John P. Flaherty Jr. stated “The common law has consistently held to a rule which provides that one human being is under no legal compulsion to give aid or to take action to save another human being or to rescue…To do so would defeat the sanctity of the individual, and would impose a rule which would know no limits, and one could not imagine where the line would be drawn.” I think the court’s decision here lines up with most of our intuitions (including – I would assume – most pro-lifers). Shimp should be legally allowed to refuse the bone marrow transfusion because McFall, while he is a person with a right to life, does not have the right to use Shimp’s body. Likewise, we should also conclude that abortions should be legal because the fetus, while it is a person with a right to life, does not have the right to use the mother’s body.

Now, there are a few points of disanalogy between pregnancies and the violinist thought experiment and the McFall v. Shimp case. For one, the McFall v. Shimp case doesn’t actually involve any “disconnecting” like abortion does, but I think our intuitions would remain undisturbed if we imagine that Shimp woke up and found himself attached to a machine without his consent to initiate the bone marrow transfusion. Secondly, the violinist is an unknown stranger, whereas the fetus is the offspring of the mother, and a pro-lifer might say that parents have special obligations to their offspring. However, I think this worry can be accommodated by imaging that you wake up to find yourself hooked up to your infant son instead of a violinist. Call this Blood Transfusion 1:

Blood Transfusion 1: imagine that you wake up and find that you’ve been kidnapped and hooked up to your infant son’s circulatory system. Your son has a fatal kidney ailment and your kidneys are needed to extract poisons from his blood. He will fully recover in nine months so long as you do not prematurely disconnect. Should you be legally allowed to disconnect?

I think most people, including most pro-lifers, would agree that you should be legally allowed to disconnect in Blood Transfusion 1. So, while most people accept the Anti-Killing Principle (AKP), most also accept a separate principle that defeats AKP in certain cases. Call this the Bodily Integrity Principle. The pro-choicer, then, can accept the following two claims to explain why abortion should be legal:

• Anti-Killing Principle (AKP): there is prima-facie reason to outlaw any action that involves an agent killing another person.
• Bodily Integrity Principle (BIP): the reason given by the Anti-Killing Principle is prima-facie defeated when the action involves the agent preventing serious infringements to their bodily integrity which kills a person whose life relies on such infringements.

I say that the Bodily Integrity Principle merely prima-facie defeats AKP to allow for the possibility that it might not defeat AKP in all contexts. Now, there are two possible responses from pro-lifers. Firstly, Pro-lifers can deny BIP. But very few pro-lifers take this response. Almost everyone thinks you should have the right to disconnect from the violinist, to refrain from assisting Shimp, and to disconnect in Blood Transfusion 1. In other words, almost everyone accepts the prima-facie importance of bodily integrity as outlined in BIP. The second possible response by pro-lifers is to grant BIP, but provide some further principle that actually defeats BIP in the case of abortion. I will focus on this response in this post since it is the more common response. I will argue that this response fails, which means that if one should be legally allowed to disconnect in Blood Transfusion 1, then one should also be legally allowed to abort a pregnancy (since the BIP would permit one to disconnect in both cases).

Responsibility

As stated earlier, most pro-lifers accept the Bodily Integrity Principle but argue that, while it applies in cases such as Blood Transfusion 1, it does not apply to the case of abortion. The most cited distinction between abortion and cases like Blood Transfusion 1 is the responsibility of the agent. The vast majority of pregnancies are the result of women engaging in consensual intercourse with the foreseeable consequence of pregnancy, which means women are responsible for their pregnancies in most cases (I will concede to the pro-lifer that this is sufficient to constitute responsibility). However, in the violinist thought experiment, you are not responsible for the violinist being dependent on your body, and Shimp is not responsible for McFall being dependent on him either. Note that, according to this argument, the pro-lifer should grant that pregnant women should be allowed to receive abortions for pregnancies due to rape (indeed, most pro-choicers and pro-lifers support legalizing abortions for pregnancies due to rape). However, according to this argument, the pro-lifer is committed to saying that one should not be allowed to disconnect in Blood Transfusion 1 if one is responsible for the infant being in their needy conditions. This is a far more controversial claim. Consider the following modification of the Blood Transfusion case:

Blood Transfusion 2: imagine that you voluntarily decide to coat the interior of your home with a dangerous brand of paint that has the foreseeable consequence of causing a fatal kidney ailment in your infant son which will make him require blood transfusions from yourself. Your son consequently develops the ailment and is in need of a blood transfusion. You wake up and find that you’ve been kidnapped and hooked up to his circulatory system. He will fully recover in nine months so long as you do not prematurely disconnect. Should you be legally allowed to disconnect?

The pro-lifer who uses the responsibility objection to morally distinguish aborting pregnancies due to consensual sex and disconnecting in Blood Transfusion 1 must argue that you should not be legally allowed to disconnect in Blood Transfusion 2 (since you would be responsible in this case). This means that the pro-lifer accepts a separate principle that defeats the Bodily Integrity Principle in certain cases. Call this principle the Responsibility Principle. Thus, pro-lifers can accept the following claims:

• Anti-Killing Principle (AKP): there is prima-facie reason to outlaw any action that involves an agent killing another person.
• Bodily Integrity Principle (BIP): the reason given by the Anti-Killing Principle is prima-facie defeated when the action involves the agent preventing serious infringements to their bodily integrity which kills a person whose life relies on such infringements.
• Responsibility Principle (RP): the defeater given by the Bodily Integrity Principle is itself prima-facie defeated when the agent performed a voluntary decision that had the foreseeable consequence of causing the needy person to depend on such infringements.

The pro-lifer grants that one should be legally allowed to disconnect in Blood Transfusion 1 because of the Bodily Integrity Principle, yet maintains that one should not be legally allowed to disconnect in Blood Transfusion 2 because of the Responsibility Principle. Similarly, such pro-lifers can grant that mothers should be legally allowed to abort pregnancies due to rape because of the Bodily Integrity Principle, yet maintain that mothers should not be legally allowed to perform abortions for pregnancies due to consensual intercourse because of the Responsibility Principle.

One pro-choice response is to simply reject the Responsibility Principle. Judith Thomson does just this in her paper. After all, is it really plausible that you should not be legally allowed to disconnect in Blood Transfusion 2? While this might be an acceptable response for pro-choicers, I don’t believe it’s a suitable response for my purposes here. Recall that my goal is to show that the Anti-Killing Principle is defeated in the case of abortion by appeal to intuitions accepted by the majority of pro-lifers. Thus, I think a more suitable pro-choice response is to grant the Responsibility Principle and grant that one should not be allowed to disconnect in Blood Transfusion 2 (which grants a lot to the pro-life argument). Despite these concessions, I will argue that one can maintain that abortions should be legal because of some other principle that defeats the Responsibility Principle in the case of abortions.

Deprivation

I believe that the Responsibility Principle, while it has prima-facie force, does not apply in the case of abortion (even for pregnancies that are due to consensual intercourse). Namely, the Responsibility Principle does not apply because the agent’s voluntary action that makes them responsible – i.e. consensual intercourse – does not result in the deprivation of life. A similar argument was given by David Boonin in his paper “A defense of “A Defense of Abortion”: On the responsibility objection to Thomson’s argument“.

I grant that a woman who becomes pregnant due to consensual intercourse is causally responsible for the fetus being dependent on her body, but I deny that she is responsible in the relevant sense for the fetus’s circumstances. What do I mean by “in the relevant sense”? Typically, to say that an action makes an agent responsible for a victim’s needy circumstances implies that, if not for the agent’s action, the victim would have continued their life without being in those needy circumstances. This describes Blood Transfusion 2. The hidden assumption is that if you never coated your home with the toxic paint, then the infant’s life could have continued just fine without him being in need of a blood transfusion. This hidden assumption explains why it might seem intuitive to pro-lifers that you should not be legally allowed to disconnect: by (a) coating the home and (b) disconnecting the blood transfusion, these combined actions deprive the infant of a life that he would have otherwise had. However, this kind of deprivation is not applicable to abortion. The fetus would not have had any life (let alone a good life) had the woman not conceived it. Whereas the combined action of (a) coating the home and (b) disconnecting the blood transfusion deprives the infant of a life that he might have otherwise had, the combined action of (a) conceiving a fetus and (b) aborting the pregnancy does not deprive the fetus of a life that it might have otherwise had. Therefore, the woman should be allowed to abort the fetus. To illustrate the importance of deprivation, consider another variation of the blood transfusion thought experiment:

Blood Transfusion 3: imagine that your infant son has a fatal kidney ailment through no fault of your own. He requires a series of blood transfusions in order to live which requires you to remain connected to him for the next nine months. If you do not connect immediately, he will die within an hour. You voluntarily decide to connect and commence the transfusions. One day passes. Should you be legally allowed to disconnect at this point?

I think most would agree that you absolutely should be legally allowed to disconnect. Technically, you are causally “responsible” for your son’s predicament because, had you not initially connected, he wouldn’t be in this needy condition. However, you are not responsible in the relevant sense because, had you not initially connected, he wouldn’t even be alive (remember, he would have died within an hour if you didn’t connect). Thus, even though your initial voluntary action makes you causally responsible for your son’s predicament, it does not follow that you should be legally forced to remain connected. You should be legally allowed to disconnect because this would not deprive him of a life that he would have had without the initial connection. Likewise, the pro-choicer can grant that a pregnant woman is causally responsible for putting the fetus in their dependent predicament. However, she is not responsible in the relevant sense because, had she never conceived the fetus, the fetus wouldn’t even be alive. Thus, even though a woman’s initial consensual intercourse makes her causally responsible for the fetus being in its predicament, it does not follow that she should be forced to remain connected to the fetus. She should be legally allowed to disconnect because this would not deprive the fetus of a life that it would have had without the initial intercourse.

So, on this pro-choice argument, the Responsibility Principle, while it has prima-facie force, is defeated by another principle in the case of abortion. Call this the Lack of Deprivation Principle. The pro-choice argument I’m giving accepts the following four claims:

• Anti-Killing Principle (AKP): there is prima-facie reason to outlaw any action that involves an agent killing another person.
• Bodily Integrity Principle (BIP): the reason given by the Anti-Killing Principle is prima-facie defeated when the action involves the agent preventing serious infringements to their bodily integrity which kills a person whose life relies on such infringements.
• Responsibility Principle (RP): the defeater given by the Bodily Integrity Principle is itself prima-facie defeated when the agent performed a voluntary decision that had the foreseeable consequence of causing the needy person to depend on such infringements.
• Lack of Deprivation Principle (LDP): the defeater given by the Responsibility Principle is itself prima-facie defeated when the needy person would not have been alive if not for the agent’s initial voluntary decision.

On this pro-choice argument, in very rough terms, while responsibility typically trumps bodily integrity, the lack of deprivation trumps responsibility in the case of pregnancies. The fact that consensual intercourse makes women technically responsible for the pregnancy is irrelevant because this consensual intercourse doesn’t deprive the fetus of a life that they would have otherwise had. Because responsibility is irrelevant, we ought to treat pregnancies due to rape the same as we treat pregnancies due to consensual intercourse. Therefore, because respect for bodily integrity demands the legalization of abortions for pregnancies due to rape (as most pro-lifers agree), respect for bodily integrity also demands the legalization of abortions for pregnancies due to consensual intercourse. We should be pro-choice.

Some Responses

Does the argument support legal infanticide or intentionally letting one’s child die? Outside of extreme conditions (e.g. the fetus needs someone’s kidney to live), no. If I gave absolute importance to bodily integrity, then the argument would support infanticide, or at least intentionally letting one’s child die (because preventing an infant from dying requires expending some bodily resources, e.g. caloric resources). However, the Bodily Integrity Principle does not give absolute importance to bodily integrity. The principle gives bodily integrity the same importance that is given by most pro-lifers. Most pro-lifers would recognize that forcing a mother to donate an organ to save her infant’s life would be a serious infringement and therefore impermissible, whereas forcing a mother to seek a responsible caretaker for her infant (if she refuses to care for the child herself) is a non-serious infringement and is therefore permissible. Because the Bodily Integrity Principle only concerns serious infringements to their bodily integrity, the argument is not committed to supporting infanticide.

Does the argument imply that parents should not be legally forced to provide financial support? No. Again, if I gave absolute importance to bodily integrity, then my argument would be committed to denying that parents should be forced to provide financial support (because acquiring the financial resources to pay the child support requires expending some bodily resources, e.g. caloric resources). But my argument does not give absolute importance to bodily integrity. Again, my argument relies on giving bodily integrity the same importance that is given by most pro-lifers. Most pro-lifers recognize that there is a morally relevant distinction between, say, forcing a father to provide child support and forcing a father to donate an organ to save their child. The latter would be a serious infringement and therefore impermissible, but the former would be a non-serious infringement and is therefore permissible. Because the Bodily Integrity Principle only concerns serious infringements to their bodily integrity, the argument does not imply that parents should not be legally forced to pay child support.

How do we know that undergoing pregnancy and giving birth counts as a serious infringement? I believe most reasonable people, including most pro-lifers, already agree that pregnancy and giving birth are serious infringements to bodily integrity. As mentioned earlier, most pro-lifers believe a woman should be legally allowed to abort pregnancies due to rape. However, most people, even most pro-choicers, do not believe that a mother should be legally allowed to let her infant die if the child was conceived out of rape. The difference between these two intuitions (which most pro-lifers and most pro-choicers share) must lie in the fact that pregnancy and giving birth constitute serious infringements to bodily integrity (whereas expending resources to prevent an infant’s death is only a non-serious infringement).

Does the argument imply that pregnant mothers should be legally allowed to consume dangerous substances (e.g. drugs, alcohol, poisons, etc.) that cause pain to the fetus or stunt its development after birth? No, my argument only appeals to bodily integrity to defeat the Anti-Killing Principle. In other words, bodily integrity only allows one to perform an action that kills someone else. It doesn’t necessarily allow one to cause suffering to someone. Now, one might ask how one can be allowed to kill someone while not being allowed to cause unnecessary suffering. This is a good question, but I don’t think it’s a question that my argument needs to answer. Most people (including most pro-lifers) already accept that bodily integrity can allow killing a being without accepting that it allows causing unnecessary suffering. For example, even most pro-lifers accept that abortions should be legally allowed for pregnancies due to rape. However, does this mean most pro-lifers are committed to believing that the pregnant mother should be legally allowed to consume dangerous substances during pregnancies due to rape? Of course not! Even pro-lifers can agree that there is a morally relevant distinction between using bodily integrity to allow killing a being and using bodily integrity to allow causing suffering. My argument appeals to this distinction that even pro-lifers already accept. Thus, my argument is not committed to legalizing the consumption of dangerous substances during pregnancy.

Does this argument support legalizing late-term abortions? Not necessarily. Again, my argument relies on giving bodily integrity the same importance that is given by most pro-lifers. Most pro-lifers believe that bodily integrity supports legalizing abortion for pregnancies due to rape. However, most pro-lifers (probably) do not support legalizing late-term abortion for pregnancies due to rape. Assuming this distinction is sustainable, my argument is not committed either way to whether late-term abortions should be legal. Of course, there might be independent reasons for denying that this distinction can be sustained, but my argument does not take a stand either way on the issue.

Why accept this argument? Like most arguments in applied ethics, my argument rests on intuitions. I believe my argument should be accepted because it coheres with the shared intuitions of most people, including most pro-lifers. It does this in two ways. Firstly, accepting my argument does not lead to extremely unintuitive conclusions. For example, as shown earlier, the argument is not committed to supporting late-term abortions, financial negligence, infanticide, or fetal abuse. It also accounts for the wrongness of killing and the importance of responsibility that most pro-lifers find to be important. Secondly, rejecting my argument requires either (a) rejecting the prima-facie force of the Bodily Integrity Principle and the Lack of Deprivation Principle, or (b) granting the prima-facie force of these principles, but maintaining that they are defeated by some other reason or principle. Both lead to unacceptable conclusions:

• Let’s say one rejects either the prima-facie force of the Bodily Integrity Principle or the Lack of Deprivation Principle. This leads to the unintuitive conclusion that one should not be allowed to disconnect in either Blood Transfusion 1 or Blood Transfusion 3 (or both). Thus, this option is unacceptable.
• Let’s say one accepts the prima-facie force of both the Bodily Integrity Principle and the Lack of Deprivation Principle, but deny that they apply to abortion because of some further defeater(s). These further defeaters should be based on principles which themselves cohere with our shared intuitions. I don’t believe that such principles can be provided. Until such principles are provided, this option is also unacceptable.

Useful Papers

• Judith Jarvis Thomson (1971). “A defense of abortion“
• David Boonin (1997). “A defense of “A Defense of Abortion”: On the responsibility objection to Thomson’s argument“