Most debates over the morality of abortion premise their entire analysis on a single metaphysical question: is the fetus a human "person" endowed with a right to life from the moment of conception? Standard anti-abortion arguments assume that once fetal personhood is granted, the moral impermissibility of abortion follows immediately. Following Judith Jarvis Thomson’s seminal paper, "A Defense of Abortion" (Philosophy & Public Affairs, 1971), and David Boonin’s rigorous formalization in A Defense of Abortion (Cambridge University Press, 2003), I argue that this inference is logically invalid. Even if we grant, for the sake of argument, that a zygote or fetus is a full moral person from conception, abortion remains morally permissible in the vast majority of cases because the right to life does not include or entail a right to the continued, non-consensual use of another person’s body and internal organs.
To isolate the relationship between the right to life and the right to another's body, consider Thomson’s celebrated thought experiment:
"You wake up in the morning and find yourself back to back in bed with an unconscious violinist. A famous unconscious violinist. He has been found to have a fatal kidney ailment, and the Society of Music Lovers has canvassed all the available medical records and found that you alone have the right blood type to help. They have therefore kidnapped you, and last night the violinist's circulatory system was plugged into yours, so that your kidneys can be used to extract poisons from his blood as well as your own. The director of the hospital now tells you, 'Look, we're sorry the Society of Music Lovers did this to you—we would never have permitted it if we had known. But still, they did it, and the violinist now is plugged into you. To unplug you would be to kill him. But never mind, it's only for nine months. By then he will have recovered from his ailment, and can safely be unplugged from you.'"
Is it morally incumbent on you to accede to this situation? Undoubtedly it would be very nice of you if you did—a great kindness. But do you have to accede to it? What if it wasn't nine months, but nine years, or still longer? What if the director says, "Tough luck, I agree, but you may not unplug yourself because all persons have a right to life, and violinists are persons, and the right to life outweighs your right to decide what happens in and to your body"? As Thomson notes, this claim is outrageous. Why? Because having a right to life does not guarantee having either a right to be given the use of or a right to be allowed continued use of another person’s body—even if one needs it for life itself.
To see why "the right to life" cannot mean "the right to be given the bare minimum one needs for continued life," Thomson offers a second case: suppose you have a fatal illness and the only thing that will save your life is the touch of Henry Fonda’s cool hand on your feverish brow. Even though it would be frightfully nice of him to fly in from the West Coast to touch your forehead, you have no right against him that he should do so, and his refusal to do so does not violate your right to life or constitute murder. When you unplug yourself from the violinist, you are not violating his right to life; you are merely depriving him of something—the continued use of your kidneys—to which he never had a right in the first place.
The most common objection to the Violinist analogy is that it only applies to pregnancies resulting from rape (since you were kidnapped). Critics argue that in the vast majority of abortions in the United States, pregnancy results from voluntary sexual intercourse: because the woman knew that pregnancy was a foreseeable risk of sex, she is "causally responsible" for the fetus's presence and has tacitly consented to let the fetus use her body.
Both Thomson and David Boonin demonstrate that this objection conflates foreseeing a risk with granting a moral right to one's body. First, as Boonin establishes in Chapter 4 of A Defense of Abortion, tacit consent can only occur when one voluntarily participates in a convention whose explicit purpose is to transfer a right (such as leaving money on a restaurant table). Engaging in sexual intimacy—especially while actively using contraception to prevent conception—is the exact opposite of consenting to pregnancy.
Second, foreseeing that a voluntary action might result in another person becoming dependent on you does not grant that person a right to your body. Thomson illustrates this with a cascade of parallel scenarios:
Finally, critics argue that even if a fetus does not have a strict right to the mother's body, refusing to sustain a dependent life is callous and indecent. Here Thomson introduces the vital distinction between the Good Samaritan and the Minimally Decent Samaritan. In the biblical parable, the priest and the Levite were not Minimally Decent Samaritans because they refused to lift a finger even when doing so cost them almost nothing. The Good Samaritan, by contrast, went out of his way and assumed significant personal cost to help a stranger.
However, human pregnancy is not a trivial inconvenience; gestation and childbirth restructure every physiological system of a woman's body, carrying substantial risks of gestational diabetes, preeclampsia, hemorrhage, permanent pelvic floor injury, and maternal mortality, followed by decades of profound personal and socioeconomic transformation. In no other legal or moral domain in the United States do we compel any citizen—including biological fathers or mothers of born children—to act as a Good Samaritan by surrendering their bone marrow, blood, or kidneys to keep their child alive (McFall v. Shimp, 1978). Carrying an unwanted pregnancy to term is an act of moral supererogation (heroic generosity), not a baseline moral duty; therefore, declining to do so in the majority of US abortions is not immoral.
The opponent relies on Judith Jarvis Thomson’s famous Violinist thought experiment and David Boonin’s defense of it to argue that even if the fetus is a full moral person with a right to life, abortion is permissible as a refusal of bodily support. While Thomson’s argument is ingenious, philosophers Francis J. Beckwith (Defending Life: A Moral and Legal Case Against Abortion Choice, Cambridge University Press, 2007), Patrick Lee and Robert P. George (Body-Self Dualism in Contemporary Ethics and Politics, 2008), and Stephen Schwarz (The Moral Question of Abortion) have demonstrated that the Violinist analogy collapses when applied to the vast majority of abortions in the United States. Specifically, Thomson’s argument fails on four independent grounds: (1) the distinction between intentional killing and merely letting die, (2) causal responsibility for dependency, (3) special parental obligations toward offspring, and (4) natural biological teleology vs. artificial kidnapping.
In the Violinist scenario, the violinist is already suffering from a fatal pathology (renal failure), and you simply unplug the tubes connecting your kidneys to his circulatory system; he then dies of his underlying kidney disease. You do not stab, poison, or dismember the violinist. As philosopher Philippa Foot established in "The Problem of Abortion and the Doctrine of the Double Effect" (1967), our entire moral and legal order distinguishes between the negative duty not to kill (refraining from initiating a lethal causal sequence against a person) and the positive duty to save (intervening to rescue someone from an existing threat).
Standard abortion procedures in the United States are not "unplugging" a sick stranger:
Because the negative duty not to actively kill an innocent person is vastly more stringent than the positive duty to provide organ donation (which is why Henry Fonda may decline to fly across the country, yet may not shoot a sick patient), Thomson’s analogy fails at the threshold.
The opponent invokes Thomson’s "Burglar" and "People-Seeds" analogies (along with Boonin’s critique of tacit consent) to argue that voluntary sexual intercourse does not make parents responsible for sustaining the fetus. However, as Jeff McMahan (2002) and Francis Beckwith (2007) point out, the responsibility objection does not rely on the legal fiction of "tacit consent." Instead, it relies on a foundational principle of tort and moral justice: Moral Responsibility for Foreseeable Need.
If you voluntarily engage in an activity that carries a known, intrinsic risk of placing an innocent person in a state of mortal peril and radical dependency upon you—where nobody else in the universe can rescue them—you incur a strict duty to sustain them until they can be safely transferred to another caregiver. Consider two counter-analogies from the philosophical literature:
Furthermore, Thomson treats the relationship between a pregnant woman and her unborn child as if they were two strangers who collided in the night, akin to the court case McFall v. Shimp (which involved adult cousins and an invasive surgical extraction of bone marrow). In fact, our law and morality universally recognize that biological parents hold special positive duties to their offspring that they do not hold toward strangers. If a father and mother snowed-in at a remote cabin for nine months refuse to feed their newborn—even if the mother must breastfeed the infant with her own body because no formula is available—they are guilty of child neglect and homicide.
Finally, as Patrick Lee and Robert P. George demonstrate, kidnapping a citizen and surgically splicing their kidneys to a violinist violates the natural teleology of the kidneys (whose biological function is to filter your own blood). By contrast, the human uterus is the only organ in the human body whose entire biological function is to nourish and shelter a developing human embryo. Providing an unborn child with its natural intrauterine shelter for nine months is therefore ordinary parental care, not extraordinary medical heroism.
