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David Boonin is an associate professor of Philosophy at the University of Colorado at Boulder. In his book, In Defense of Abortion, Boonin attempts to argue from premises that pro-lifers accept to show that abortion is morally permissible.

Boonin is unique among pro-choice writers because he’s willing to meet pro-lifers where they are at and grant that the unborn are human persons. He talks about how he has several pictures of his son Eli in his office. He describes a few of them and how Eli was a different age in each. He then explains, “Through all of the remarkable changes that these pictures preserve, he remains unmistakably the same little boy.”1 The last photo he describes was a sonogram taken of Eli weeks before his son was born. He muses, 

“There is no doubt in my mind that this picture, too, shows the same little boy at a very early stage in his physical development. And there is no question that the position I defend in this book entails that it would have been morally permissible to end his life at this point.” 2

It is a chilling admission but it’s also somewhat refreshing to hear such brutal honesty. Boonin is a serious, careful thinker, and his arguments deserve to be engaged with.

In this article, I will first summarize the five chapters of the book. In the second half, I will show four weaknesses I see with his book.


Chapter 1

Boonin explains that there are two questions that are generally asked about abortion: “Is it moral or immoral?” and “should it be legal or illegal?” He writes, 

“In principle, these are importantly distinct questions. There are actions such as jaywalking, which we may think to be justifiably illegal and yet not immoral, and there are actions, such as adultery, which we may think to be immoral and yet not justifiably illegal.” 3

For everyone to get on board with abortion, it would have to be shown to be morally justified. If it is seen as on par with murder, it is no surprise that people would be calling for it to be criminalized. Boonin defines an action as morally permissible “if no one has a valid claim against my doing it, that doing it violates nobody’s moral rights.”4 His thesis is that the fetus has no valid claims against the woman having an abortion because even though it is a human like his son through every stage of development, that is not enough to endow him or her with rights.

To show this, he uses a method called reflective equilibrium.

“We begin by accepting, at least provisionally, our moral intuitions about a variety of types of actions, giving more initial weight to those which seem especially clear or forceful. We then attempt to develop a credible moral theory that would serve to unify and underwrite these various judgments.”5

He sees this as the exact approach used by critics of abortion when they attempt to show that if abortion is allowed in one case, it could lead down a slippery slope to killing infants in similar circumstances.

Chapter 2

Boonin takes on the conception criterion that pro-lifers put forward as grounding a fetus’ right to life. He explains that all such arguments stem from the idea that “you and I have this right, and that we are related to human fetuses in important ways in which we are not related to dogs, trees, ecosystems, and other possible objects of moral concern.”6 He places the burden of proof on the pro-lifer to show what the salient similarities are, then moves to critiquing the various attempts. There are dozens of examples but for the sake of space, I will focus on one that addresses a very common pro-life argument.

Boonin tackles the parsimony argument which points to the fact that from fetus to adult, we are all members of the species homo sapiens. He rightly points out though that merely saying someone is a human being is not the same as saying they have a right to life. The second half needs justification. What a pro-lifer would do then is point to ten individuals that both he and the pro-choicer agree have a right to life and ask what they all have in common. The answer is: their humanity. Boonin rejects this, however, on several grounds. First, “species membership in itself does not provide a satisfactory explanation for the consensus that both sides of the abortion debate will reach in the case of the ten individuals you have selected.”7 He puts forward a hypothetical scenario where a DNA test comes back from one individual and reveals that he is an alien from another planet. He argues, 

“No matter what our views on abortion, it is extremely difficult to believe that this discovery would make us think it any more permissible to kill him. He has all the same properties we thought he had before; he simply got them from alien parents instead of human ones.”

Secondly, he asks about the individual who is human but gets into an accident and has their higher brain functions destroyed. It might be possible to criticize the idea of removing him from life support but he considers the claim that they have the same right to life as we do as controversial at best. These two hypothetical situations he believes undermine the parsimony objection.

Chapter 3

This chapter consists of two parts. The first is an attempt to rebut arguments which claim fetuses have human rights at other early stages of development, such as implantation, when the baby has human form, fetal movement, quickening, and initial brain activity. 

Boonin lays out his argument for when he thinks human fetuses acquire the right to life: the stage where cortical brain activity is present. He writes, 

“organized cortical brain activity refers to electrical activity in the cerebral cortex of the sort that produces recognizable EEG readings… there is no evidence to suggest that this occurs prior to approximately the 25th week of gestation, and ample evidence to suggest that it does begin to occur sometime between the 25th and 32nd week. If the onset of such activity marks the point at which the fetus acquires the right to life, then the vast majority of abortions do not involve the death of an individual with a right to life.”9

Why is cortical brain activity so important? Because at this point, the human fetus has a brain which gives it the potential for a desire not to have its life terminated. This sets the fetus apart from a cow or a pig whose brains never have that potential.

Chapter 4

Here, Boonin switches gears. He grants that the fetus has a right to life at every stage for the sake of argument. However, he uses Judith Jarvis Thomson’s violinist argument to show that abortion is still permissible even if they have a right to life. The argument goes like this: 

One morning, you wake up in a hospital and find yourself attached by tubes to a violinist. The violinist is suffering from a fatal kidney disease and he needs a blood transfusion to stay alive. The Society of Music Lovers checked medical records and found out you were the right blood type. You are apologized to for the inconvenience, but also told that if you unplug yourself from him, he will die. But cheer up. In nine months, he will be able to survive without the use of your blood and you can go on your happy way!10 

Most people would say that in this case, you are morally justified in unplugging yourself. But then argue Thomson and Boonin, that shows that someone’s right to life does not trump your right to have control over who uses your body. If it is a violation of bodily autonomy for the violinist to use your body against your will, then it is a violation of bodily autonomy for the fetus to use the woman’s body against her will. Boonin summaries the point: 

“Once it becomes clear that the right to life does not include or entail the right to life support, that is, it becomes clear that it is not enough for the critic of abortion to establish that the fetus has a right to life…”11

He believes there are three avenues open to the pro-life side to attack this argument. 1) Find a morally relevant difference between the two scenarios. 2) We could just accept that it is morally impermissible for the woman to unplug herself from the violinist. 3) Or we can reject the authority of analogy.

Chapter 5

Finally, 5 Boonin tackles non-rights-based arguments. These include the golden rule argument, the culture of death argument, the pro-life feminist argument, and the uncertainty argument. 

Boonin has written an impressive book. It has certainly made me have to think hard about some of the arguments I have taken for granted as successful. From here I want to evaluate some of the key claims his book makes.


Boonin and I agree on a number of points.

1) There is continuity in who the human is through all stages of development. 

2) Saying something is immoral is not the same as saying it should be illegal.

3) Murder is something that is immoral and should be illegal.

4) It needs to be established that abortion is tantamount to murder. Pro-lifers consider murder to be the unjustified killing of an innocent person. 

The biggest weakness I found in Boonin’s writing is that he often overlooked key pieces of pro-life arguments. Without them, his rebuttals worked. With them, his rebuttals fell apart. First, I want to look at his take on the parsimony objection. What Boonin misses is that the parsimony argument is about proving that all humans are persons, and therefore have rights.

Let’s go back to Boonin’s scenario of the ten people in the room. Let’s add in another factor. They are ten years old, twenty years old, thirty years old, all the way up to a hundred. Is the ten-year-old less a person than the twenty-year-old? And is the twenty-year-old less a person than the thirty-year-old? Based on what Boonin has written I am confident he would say no. But this would reveal something. Boonin would be admitting that personhood is not based on age. So what’s something that they all do share that we could ground personhood, and therefore rights in? Catholic apologist Trent Horn gives a simple answer, 

“Since all human beings differ in size, intelligence, skin color, gender, and physical ability, we must ground human equality in the one thing that is truly equal about all of us: our human nature. Otherwise, if a person’s right to life is based on a property that comes in degrees… then the right to life would come in degrees.”12

What is so special about human nature though to pro-lifers? It’s that being part of the human species makes you of a rational kind. Following Boethius, we would say a person is an “individual substance with a rational nature.” What this means is that a particular being is a person, or has basic rights, if it is a member of a rational kind.13 Boonin’s illustration with the alien suggests that he worries the parsimony argument leads to speciesism, but in no way are we saying only humans are of rational kinds. Alien groups could be too, and that would also make them persons worthy of the right to life. As for the coma patient whose higher brain function is destroyed, that doesn’t change that he has a  human nature. He is still of a rational kind, even if he is not currently exercising that capacity, and that makes him a person. That should give him the same right to life as us. 

With this established, it is easy to critique Boonin’s cortical brain activity from a number of angles. The question we should ask is, why have earlier fetuses not acquired cortical brain activity? Because they are not at that stage of development. Why are they not at that stage of development? Because they are not the right age. It raises a question, too. As Stephanie Gray argues, “Why should those of us who are older have a right to kill those who are younger?”14 Especially when it can be shown that age itself is insufficient for determining personhood.  Boonin attempts to answer that such an age objection makes sense based on the fact that a human fetus acquires cortical brain activity at 25-32 weeks. 

Also, the idea of grounding our rights in having desires leads to absurdities. Newborn infants do not have the desire not to have their life terminated. But we don’t say it’s all right to kill them. So why is it okay in the case of the unborn? Here, Boonin has anticipated such a response. In his book, he defends a distinction between two types of desires, occurrent and dispositional. He writes,

 “A desire of yours is an occurrent desire if it is one that you are consciously entertaining…. A desire of yours is dispositional if it is a desire that you do have right now even if you are not thinking about it at just this moment.”15

So perhaps he could argue that even if the newborn does not have an occurrent desire to not be killed, he or she does have a dispositional one. That sets it apart from the unborn. Here, I would want to ask Boonin a set of questions. It might seem like a bit of a rabbit trail, but bear with me. Is a single cell amoeba rational? Boonin would probably answer no. I would then follow up by asking why it’s not a rational being. The answer would be because it does not have a brain. (You can bet he would probably again point out that neither does the unborn for the first few weeks.) But then I would press and ask if the amoeba would ever develop a brain. Anyone with a little knowledge of biology would know that the answer is no. But then as Gray argues, 

“wouldn’t it be correct to say, an amoeba isn’t rational because of what it is? Namely, that it’s not within its nature to be a rational creature?… And doesn’t that answer tell us why amoebas aren’t people but human embryos are?… an amoeba isn’t rational because of what it is. But… a human embryo isn’t rational because of how old she is. One can’t ever think. The other can’t think yet– because of her age…. Since we’ve established the pre-born are humans, then shouldn’t they get the same rights as you or me, regardless of their age?”16

Moreover, a little reflection shows that dispositional desires are hardly necessary for grounding the right to life. Francis Beckwith gives the example of a slave who has been thoroughly brainwashed to the point where he loves being a slave and does not have any desire to be freed. Would we honestly say that he is not being wronged by being in slavery just because he doesn’t desire to be free?17 Boonin here might respond with another distinction between ideal and actual desires. In an ideal situation, the slave (and newborn) would desire their freedom and right to life. But then he’s already given up his own criteria for grounding human rights. Now he’s grounding both the slave and the newborn child’s rights in the fact that they are the sort of being that should desire these things. Becwkith argues, 

“Then, it is not desire that grounds the right to life, but the nature of the sort of being that would have this correct desire if it had not been indoctrinated, or will have this correct desire when it reaches a certain level of maturity and it is functioning properly.”18

So grounding human rights in personal nature is still the most parsimonious approach.

But that brings us to the violinist argument. When I first heard this argument, it threw me. I am definitely a pro-lifer who would tell the person who got plugged into the violinist that they are not required to use their body to keep that person alive. And of course, that led me to wonder, as the argument is meant too, “How then can I tell a woman she’s required to be plugged into a baby for nine months just to keep it alive? If human rights isn’t a solid enough foundation to grant that to a violinist, why is it enough to grant it to the unborn?”

But this made me in turn start thinking about what we expect of parents in general. Scott B. Rae asks us to imagine a scenario where you and your spouse have a four-month-old baby in your house.

The baby has not been sleeping for more than a couple of hours at any one time, and both of you are exhausted and desperately need a break. So you decide to take a two week vacation, just the two of you. But instead of making arrangements for the baby, you prepare enough bottles of formula for two weeks and you stack two week’s worth of diapers in the nursery. You then kiss your baby goodbye and leave. Upon your return, who do you think would be there to “greet” you? Angry neighbors, incensed relatives, Child Protective Services, and the police — all of those, and possibly others, would be very interested to see you on your return.“19

Chances are you’d be arrested for child negligence, maybe even infanticide because the baby died before anyone found him or her. What this tells us is that if you’re a parent, your child has the right to expect you to look after his or her basic needs. Even when it puts a strain on you that you’d rather not have.

That seems to be a large difference between the violinist and the unborn baby. There are no parental obligations to the violinist. Boonin acknowledges this but says “But it will count against the good samaritan argument only if these obligations are generated by the mere fact of the biological relation between them.”20 The biological connection is certainly part of it. But there are other considerations. 

One is the responsibility factor. All the woman who woke up plugged into the violinist did was go to bed. That is not an action that leads naturally to her situation. Having sex on the other hand does naturally lead to pregnancy. Thus the woman engaged in activity that created a life that is dependent on her.21 Second, there is the fact that no one besides the woman could provide the baby what they needed at the earliest stages of their life. 

Boonin counters this first point by saying that you might be responsible for the fetus’ existence, but you are not responsible for the fact that it is needy.22 That much is true. The baby is needy because that is the nature of the fetus at that stage of development. But let’s go back to the scenario of the couple who abandons their child so that they can take a vacation. Sure, they are responsible for the baby’s existence. But they’re not responsible for the fact that it needs them to stay home with it to survive. Are they justified in leaving the baby home alone even though it dies?

Boonin does not like analogies such as this. He thinks they beg the question. We’ve already decided that newborns have the right to life. Meanwhile, whether the unborn do is the very question being raised.23 But hasn’t he already granted that very point and is trying show that abortion is still justified anyway? Moreover, as Beckwith points out, this charge of question-begging would ultimately undermine his and Thompson’s case because they all “present uncontroversial examples… to extract from them principles that may be applied in the controversial question of justifying abortion if the unborn is a person.”24 I am simply using analogy to show the logical outcome of their principle that I detect. After all, ideas have consequences.

A second counter Boonin raises is that the woman consented to being a parent by carrying the child to term, giving birth, and taking a child home with her. But he does not believe that a woman engaging in sex is the same as her agreeing to get pregnant.25 This is tied to the bodily autonomy arguments. And he might be right about that. But it’s also true that you don’t have to consent to have someone in your care before you’re legally responsible for them. Mary Anne Warren makes this point well:

“… the appeal to the right to control one’s body, which is generally construed as a property right, is at best a rather feeble argument for the permissibility of abortion. Mere ownership does not give me the right to kill innocent people whom I find on my property, and indeed I am apt to be held responsible if such people injure themselves while on my property. It is equally unclear that I have a right to expel an innocent person from my property when I know that doing so will result in their death.”26

Let’s go back one last time to the parents who leave their baby home alone. You’re a neighbor who they asked to come by and feed the cats once a day. The first day you come over, you find the baby alone and starving and in need of a change. You could say, “Well, I consented to watching the house. That’s not the same as consenting to looking after this abandoned baby.” But if it was discovered that you also abandoned the baby, you’d likely be in just as much legal trouble as the parents. If this is true for someone who isn’t a parent, how much more should it be true for a parent? For these reasons, I don’t find his defense of the violinist argument compelling enough to prove it is okay for a parent to kill their child even though they’re a human person.

In the last chapter, Boonin addresses an issue that deserves mention: the uncertainty argument. Since are uncertain about the moral status of the fetus, some argue, shouldn’t we err on the side of not killing them? Boonin says 

“The basic structure of the argument from uncertainty is clear. The argument conjoins the claim that we are uncertain about the moral status of abortion with a principle designed to govern the moral choices made under such conditions of uncertainty. What is less clear, however, is just what, precisely, the principle appealed to is meant to say.”27

He suggests three ways this could be taken. His first attempt to state the principle comes closest to what pro-lifers are saying. “It would be so terrible to accept the belief that abortion is permissible if it turned out to be mistaken, that even the most remote chance that the belief is mistaken is enough to render the risk involved in accepting the belief itself unacceptable.”28 Apologists will often offer this scenario to illustrate the point. Suppose you’re out hunting with a friend. You both go in separate directions to find your prey. A while later, you hear rustling in the bush. You are not sure if it’s your friend or an animal. What would you do in that case? Shoot first and ask questions later? Or make sure your friend’s life wasn’t at stake? I think most people who aren’t considered anti-social would answer the latter. Why? Because in general, we believe human life is worth protecting from intentional and even accidental killing.

Boonin thinks this argument doesn’t work because it produces implications even a pro-lifer wouldn’t accept. He writes, 

“The disaster avoidance version of this argument, for example, depends on the claim that as long as we are not literally certain that an act is morally permissible, we must accept that claim that it is morally impermissible.”29

Again though, Boonin is not taking the argument seriously enough. The uncertainty argument is usually played when the proponent of abortion claims it’s either not a person, or not a human being. They may just throw up their hands and say, we are not sure if it’s a person, or human. That is when we would bring out the hunter analogy. Some of the people Boonin quotes state the principle of that story quite clearly. Pope John Paul II said, “What is at stake is so important that, from the standpoint of moral obligation, the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo.” There are definitely other situations where the right course of action is less clear, as Boonin alludes to. But when it comes to human life, our moral intuitions, and our human rights documents say to side with preserving human life. Boonin’s rebuttal does not adequately address this. 


In this article, I began by summarizing David Boonin’s arguments. I then analyzed them. He gave a valiant effort to meet the critics of abortion halfway, and discuss these issues based on terms they would accept. However, often, he was mistaken about what some of the arguments are. Moreover, his criteria for what grounds human rights lead to certain absurd conclusions. His violinist argument does not provide sufficient grounds for abortion. For those reasons, his defense of abortion does not work. 


  1. David Boonin, A Defense of Abortion (Cambridge EN: Cambridge University Press, 2003), xiii.
  2. Boonin, A Defense of Abortion, xiv.
  3.  Boonin, A Defense of Abortion, 4.
  4. Boonin, A Defense of Abortion, 5.
  5. Boonin, A Defense of Abortion, 10.
  6. Boonin, A Defense of Abortion, 19.
  7. Boonin, A Defense of Abortion, 22.
  8. Boonin, A Defense of Abortion, 23.
  9. Boonin, A Defense of Abortion, 115.
  10. Boonin, A Defense of Abortion, 135.
  11. Boonin, A Defense of Abortion, 137.
  12. Trent Horn, Persuasive Pro-Life: How to Talk about our Culture’s Toughest Issue (El Cajun, CA: Catholic Answers Press, 2014), 129.
  13. Horn, Persuasive Pro-Life, 129-130.
  14. Stephanie Gray, Love Unleashes Life: Abortion and the Art of Communicating Truth (Toronto, ON: Life Cycle Books, 2015). 48.
  15. Boonin, A Defense of Abortion, 122.
  16.  Gray, Love Unleashes Life, 49.
  17. Francis J. Becwkith, Defending Life: A Moral and Legal Case Against Abortion Choice (Cambridge: Cambridge University, 2007), 148.
  18. Beckwith, Defending Life, 149.
  19. Scott B. Rae, Introducing Christian Ethics: A Short Guide to Making Moral Choices (Grand Rapids: Zondervan, 2016), 76.
  20.  Boonin, A Defense of Abortion, 234. 
  21. Scott Klussendorf, The Case for Life: Equipping Christians to Engage the Culture (Wheaton, IL: Crossway Books, 2009), 189.
  22. Boonin, A Defense of Abortion, 173.
  23. Boonin, A Defense of Abortion, 168.
  24. Boonin, A Defense of Abortion, 185.
  25. Boonin, A Defense of Abortion, 166-167.
  26. Quoted in Horn, Persuasive Pro-life, 157.
  27.  Boonin, A Defense of Abortion, 311.
  28.  Boonin, A Defense of Abortion, 312.
  29.  Boonin, A Defense of Abortion, 314.
  30. Quoted in Boonin’s, In Defense of Abortion, 311.

Born in Vancouver, B.C., Chris has been married to Amy for 3 years. He has a BA in Religious Studies (Youth Leadership), and an MA in Theological Studies (Apologetics). He enjoys acting, evangelism, and debates.

The views and opinions expressed in these articles are those of the author and do not necessarily reflect the official position of Human Defense Initiative.