Article adapted from episode content.
Our culture is presently locked in an argument over two questions whose answers will shape the lives of our children and grandchildren for decades to come. The first is the question of truth: Is moral truth real and knowable, or is it merely a matter of preference, like choosing chocolate ice cream over vanilla? The second, bound up with the first, concerns human value: What makes a human being valuable in the first place? Are we valuable for what we can do—our immediately exercisable capacities—or because of the kind of beings we are, possessing a nature that, as Christians, we recognize bears the image of our Maker? These questions drive our debates over abortion, and a great deal else besides, from transhumanism to the meaning of marriage.
It is tempting for pro-life advocates to keep the conversation at street level, and most of the time that is exactly where it belongs. But ideas have pedigrees. The arguments your neighbor repeats, often without much critical reflection, frequently began in the academic ivory tower. If we hope to answer them persuasively, we do well to understand them in their strongest form. And among the thoughtful philosophers defending abortion rights today, few are more capable than Kate Greasley of Oxford, whose book Arguments About Abortion deserves a careful and fair-minded reply. I disagree with her conclusions, but she is a serious interlocutor, and a winsome one, and that is precisely why she is worth engaging.
Common Ground: The Failure of the Bodily-Autonomy Argument
Let me begin where Greasley is right, because she is right about something many abortion-rights advocates get wrong. She rejects the bodily-autonomy argument. Many advocates claim that even if the unborn is a human being, a woman has the right to control her own body and may therefore refuse to let a dependent child make use of it. Greasley, having examined the most sophisticated versions of this argument—including Judith Jarvis Thomson’s famous violinist analogy—concludes that it does not work. Her reasoning is sound: you cannot get from an alleged right to withhold support to an alleged right to intentionally kill an innocent human person. If the unborn are human persons, then they too have a right to life, and no appeal to bodily autonomy does anything to dislodge it. I think she is exactly right, and it is refreshing to see a defender of abortion say so plainly.
Having set bodily autonomy aside, Greasley locates the debate where it belongs: on the status of the unborn. Here she makes an important concession. She agrees that the unborn are human—she does not pretend they are mere tissue. What she denies is that they are persons. And so she frames the decisive question: When does morally relevant personhood begin? Her answer is that it does not begin at conception, and she offers several arguments to show that it cannot.
Three Arguments Against Conception
Greasley contends that locating personhood at conception leads to absurd conclusions, and she gives three examples. First, she argues that if a two-celled embryo were a full person, we should mourn its loss as much as—or more than—the death of a ten-year-old child. Second, she observes that miscarriage would then represent the single greatest human tragedy in the world, since millions occur each year, and we would be obligated to pour billions into preventing it. Third, she offers the now-famous burning-lab scenario: if a research building were ablaze and you could rescue either a thousand frozen embryos or a single six-year-old girl, the logic of equal personhood would oblige you to save the embryos and let the girl burn. Yet our intuitions, she notes, run decisively the other way.
These are clever arguments, but none of them succeeds. Consider the appeal to grief. My feelings about something do not change what it is. Suppose it were true that I would grieve the death of one of my own children more than the miscarriage of an embryo. Suppose, further, that I would grieve the death of my own child more than I would grieve the deaths of six thousand children lost to malnutrition today in countries I will never visit. It simply does not follow that those distant children are less human or less valuable than my own. Proximity and attachment shape our emotions; they do not determine the worth of the one who dies.
The miscarriage argument fares no better. Miscarriage is indeed a tragedy, but there is a world of difference between a death that nature spontaneously brings about and a death we deliberately cause. That nature triggers spontaneous miscarriages does not show that the embryos who die are not human, nor does it license us to kill them intentionally. Earthquakes claim hundreds of thousands of lives in the developing world; no one concludes from this that those victims were not human, or that murder is therefore permissible.
Finally, the burning-lab scenario trades on a confusion. As the philosopher Christopher Kaczor has pointed out, we all have an equal right to life, but we do not have an equal right to be rescued. If I am in a burning building and save my own child rather than a stranger, it hardly follows that the stranger is less human or less valuable. That I save one human being over others tells us nothing about the moral status of those I could not save. The scenario tugs at our intuitions, but it does no philosophical work against the humanity of the embryo. It is worth noticing, too, what Greasley has not done. She has not engaged the scientific literature establishing that a human being’s life begins at conception, nor has she explained how, on her own view, we can account for human equality. She has instead tried to reduce the pro-life position to absurdity, and the reduction does not hold.
Does Human DNA Even Matter?
Greasley anticipates a reply. Why, she asks, should merely possessing human DNA entitle a zygote to a right to life? To insist on it, she suggests, is mere speciesism—an arbitrary preference for our own kind. And she presses the point with a striking thought experiment. Imagine a transgenic spectrum: take an ape and replace its genes, one by one, with human genes. At some point the creature would carry more human DNA than ape DNA. At what point would it suddenly become a human being? Surely we would not say that swapping genes had transformed an ape into a human. Therefore, she concludes, merely having human DNA cannot be what makes us special.
This argument misconstrues the pro-life position. We do not claim that humans are valuable strictly because they possess human DNA, as though the molecule itself were sacred. DNA is a characteristic of the kind of being we are; it is not the ground of our worth. The real claim is this: human beings have value and a right to life because they possess a particular kind of nature—a rational nature that, on the Christian view, bears the image of God. To turn an ape into a human would require not the mere replacement of parts but a substantial change of nature; the ape would have to cease being one kind of thing and begin being another. Swapping genes does not accomplish that.
The distinction comes into sharp focus when we compare an amoeba with a human embryo. The amoeba will never be self-aware, and never rational, because such capacities are simply not in its nature. The human embryo, by contrast, is rational by nature; it needs only time and the proper environment to develop what it already is. The amoeba lacks rationality because of the kind of thing it is. The embryo is not yet exercising rationality simply because it is young. That difference—between a lack rooted in nature and a lack rooted in immaturity—is precisely what Greasley’s argument overlooks.
The Charge of Arbitrariness
Pro-life advocates often point out that the traits abortion-rights philosophers select as the basis for personhood—self-awareness, the capacity to feel pain, the ability to value one’s existence over time—appear arbitrary. Worse, they generate troubling results. If self-awareness grounds the right to life, then a person in a coma would seem to forfeit it. If the capacity to feel pain is decisive, then those who feel more pain would be more valuable than those who feel less. Greasley grants that these criteria do look arbitrary. But rather than repair the problem, she responds with a counter-charge: pro-lifers, she says, have their own arbitrariness to answer for, because conception is not a sharp threshold but a process, and we cannot say precisely where along that process a human being comes to be.
Notice what has happened. Greasley has not refuted the accusation that her own position is arbitrary; she has merely replied that ours is arbitrary too. That is like being pulled over for speeding and protesting that other drivers were speeding as well. The fact that someone else may be in the wrong does nothing to justify one’s own position. And in any case, the claim that conception is a fuzzy process does not refute the pro-life argument. Even if the transition takes some hours to complete, a vague edge does not erase the real difference between an entity that is not yet a human organism and one that is.
What Grounds Human Equality
Beneath this entire debate lie two rival accounts of human value. The first is what we may call the performance view: you are not intrinsically valuable but only functionally valuable, and what gives you a right to life is your present ability to exercise certain traits. The second is the endowment view, which I hold: what matters is not which traits you can presently exercise but that you were endowed by your Creator with intrinsic value belonging to your very nature, whether you ever exercise those traits or not.
The endowment view makes sense of convictions we already hold. A child who never learns to speak is not therefore less of a person; he has simply failed to flourish according to his nature, and we rightly regard that as a tragedy and labor to remedy it—something we would never do for a rock, which by nature does not speak at all. This view fits naturally with the substance view of the human person: living things maintain their identity through time and change. A puppy that loses a leg is still a puppy. I am the same human being after losing an arm or an eye as before, because no such loss changes what I fundamentally am. And if that is so, then I am the same being now that I was at the one-cell stage. My capacities have grown; my nature has not changed. If I am intrinsically valuable today, I was intrinsically valuable then.
Kate Greasley is a serious and gracious thinker, and her book merits engagement rather than dismissal. But her central contention—that the unborn are human and yet not persons—cannot bear the weight she places upon it. Strip away the thought experiments, and the question returns to where it began: not what we can presently do, but the kind of beings we are. On that question, the unborn stand with the rest of us.