The anniversary of Roe v. Wade gives us an opportunity to reflect on the ways in which abortion is, contrary to the claims of that decision, a public issue. The Roe case was famously framed in terms of the concept of “privacy.” Both explicitly and implicitly, the question of abortion was judged by the court to be not a public matter. But what could this possibly mean?

Surely the first question at issue in deliberating about abortion is this: what is, in the case of surgical abortion, the fetus, or, in the case of chemical abortion, the embryo? What sort of being is it—a blob of tissue, as some activists claim? Or something else altogether?

The court declined to answer this question: “We need not resolve the difficult question of when life begins.” But Justice Blackmun then proceeded to suggest that the reason this question did not need settling was its unsettle-ability. Doctors, philosophers, and theologians have failed to reach consensus; ancient and medieval theorists subscribed to different theories. Thus did Blackmun imply that the answer to this question was private in the following sense: our answer is largely a matter of private opinion, of speculation.

Well, as the meme might say, I don’t always study biology, but when I do, I study modern biology! The “difficult question” is in fact answerable, if we look in the right place, and in a way that is entirely “public.” For our paradigmatic case of “public knowledge” is the case of scientific knowledge, knowledge that is public in its methods, in its convergence, and in its availability to all rational agents.

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What we find when we consult modern—not medieval!—embryologists and developmental biologists is, however, remarkable convergence on the answer to the “difficult question.” The experts in such fields show little doubt that the product of fertilization, or conception, is a single-celled but nevertheless whole, internally unified, living organism of the species Homo sapiens, an entity possessed within itself—in reality, him or herself, for sex is already specified—of the genetic and epigenetic information necessary for that young human being to grow and develop to the next stages of human life. Put another way, it is a matter of science that the lives of human beings—when not a product of monozygotic twinning or cloning—begin at conception.

So the Court’s supposition that this question could only be answered by private speculation was radically misleading; it was a foundational error in its entire approach.

Of course, no moral issue is ever settled entirely by recourse to mere facts, even facts as important as those just discussed. Moral norms must be articulated for guidance in response to the facts, and here again a distinction between public and private is possible. Some norms are thought to be available only to those of, for example, a particular tradition of revelation, outside of which the norm is bound to be unjustified or even unintelligible.

Well, what is the norm that renders abortion impermissible? Clearly, it is the norm against killing: you and I are owed a form of respect that is simply incompatible with being killed for reasons such as the inconvenience we cause, our gender, or whether we are wanted by another. But what grounds that immunity?

A reasonable answer is this: you and I are beings of a profoundly special sort. We are both rational, capable of reasoned reflection, and free, capable of choices not determined by anything other than the very making of the choice itself. Our possession of those two powers can be said to be the foundation for our dignity. This entitles us always to be treated as an end in ourselves, never as a disposable means that can be eliminated for the sake of another’s good.

Killing a being like you or me is thus radically contrary to the dignity that we possess, as it would be in relation to any other being like us in the relevant respect: like us, that is, in possessing the powers of reason and freedom. But what kind of being is that?

It is, we should hold, any being that possesses by its nature the capacity to develop itself to the point of being able to engage in acts of reason or choice. Not a being that has developed to the point of being able to reason and choose, but one whose nature it is eventually to be able to reason and choose.

Now, no being comes to be able to actively exercise such powers unless it has them from the beginning of its existence. Something not possessing these powers as radical potentialities simply could not develop them. And so we—you and I and all other beings like us—must have had these powers from the moment we came into existence. And accordingly, since we came into existence at conception (or slightly later if we are an identical twin), we possessed these radical powers right from the beginning.

Thus, we can judge that the norm against killing, grounded as it is on respect for a creature’s dignity, protects all human beings, born and unborn, against attacks on their lives.

This claim is one available to natural human reason. Of course, some traditions of revelation consistently teach this claim; that is, if anything, evidence for the truth of the tradition. And some such traditions provide theological complements to the basic norm, giving us further insight, for example, into the nature of human dignity by tracing the resemblances between creatures with dignity and their divine creator. But the core thought—that we, and beings like us, possess a dignity that entitles us to moral respect—is far from a matter of private faith or morality. On the contrary, it is robustly public.

Still, the fact that, as a matter of morality, abortion is clearly public, in both its “is” premise and its “ought” premise, does not settle the question of law. And here too we have a possible contrast between the private and the public, a contrast drawn on in Roe and by its subsequent defenders.

What is the nature of that contrast? It is at least threefold. We can, first, contrast the private with the public when the conduct in question affects only oneself. Such acts are neither interpersonal in nature nor have predictably interpersonal consequences, and they can be reasonably considered private from the standpoint of the law, which is predominantly concerned with matters of justice. But abortion always involves a minimum of two: it is interpersonal, and not private.

Second, there are some acts that are, though interpersonal, matters of mutual consent. They can be considered private, and are thus not a matter for law. Injustice is always done against the unwilling, and so consent vitiates claims of injustice. But here again abortion fails the test of privacy, for abortion is always done without the consent of the human being who suffers most from it, the unborn child.

Third, we might say of some admittedly wrong, and interpersonal matter, that it is private in the sense that its lack of gravity shields it from being reasonably considered a matter for legislation. “Don’t make a federal case of it,” we say, when the wrong done is slight, and correcting it by means of the law would perhaps do more harm than good.

But no act of killing is ever like this. And here we see perhaps the most significant way in which abortion is truly a public matter. What is “the public”? It is, first and foremost, that having to do with us, as a community, bound together with whatever bonds shape us as this community: the bonds of family, the bonds of political principle, or, at the farthest, but in some ways most important, reaches, the bonds of a shared humanity.

Yet all these bonds are sundered by abortion, as by all killing, which excises a member of the community right out of existence. Abortion says to the child, you are hereby eliminated from all the communities to which you rightly belong, including the vast community of the human. What more public act could there be? And what could be more grievous to our continuing aspiration to form, maintain, and cause to prosper the communities to which we belong?

Abortion thus is, and will remain, not just a public act and a public issue, but, for all those concerned with the human community, the most grievous of public tragedies.