On Twitter, Damon Linker politely took me to task for, in my response to a post of his, ignoring the “substance” of that post. I believe by that he meant his explanation of his own views of fetal life, as opposed to the critique of Ross Douthat that I objected to.

Well, that post wasn’t about Linker’s own position, but rather about his peculiar way of responding to Ross Douthat. But okay—since you asked!—here goes. Linker writes,

Even if my wife and I could know every time a fertilized egg fails to implant and then sloughs off when she menstruates, we still would never be moved to mourn the death of a being with intrinsic moral worth. The same holds for fertilized eggs that slough off because a sexually active woman is using an IUD — or, for that matter, because a woman is breastfeeding in the first several months after giving birth. All of these activities lead to the “death” of what really is, at that pre-implanted stage, a clump of cells that is destined not to develop into anything at all.

Nine months after successful implantation, things are very different. I would even say categorically — ontologically — different. How is this possible? I have no idea. All I know is that nearly all of us are convinced that a newborn baby is a person, a creature with intrinsic dignity, worth, and a right to life that the liberal state is duty bound and justly empowered to protect — and yet also convinced that although this same creature possessed the same genetic code from the moment of fertilization, it was somehow of relative moral insignificance in those first few hours and days of microscopic life.

I would very much like to know Linker’s evidence for the claim that “nearly all of us are convinced that … this … creature … was somehow of relative moral insignificance in those first few hours and days of microscopic life.” Nearly all? But let’s continue:

Between those moments (conception and birth) lies a developmental continuum that confounds any and every effort at strictly rational systematization. An abortion at six weeks is worse than one at four weeks. Eight weeks is worse than six. Twelve is worse than 10. And so forth, as we approach fetal viability — at which point, what was once a medical procedure with minimal moral import becomes a matter of murder.

First of all, and especially in light of my critique of Linker’s critique of Douthat, I want to say that this identification of fetal viability as the point at which a fetus becomes a person entitled to legal protection is a big step, and one that I’m sure earns Linker plenty of condemnation from the pro-abortion world. And the criticisms I am now going to offer should not be seen as ignoring that step or diminishing its significance. But do I have some concerns about Linker’s line of argument? I do.

The first is that, while Linker’s view is often described as a “gradualist” one, and while morally that may be true, in legal terms it’s not gradualist at all: it’s totally binary, all or nothing. In this account, before viability the taking of a fetal life is legally nugatory; after viability it’s murder. This is a big jump in any circumstances, but especially worrisome given the success of prenatal medicine in pushing viability earlier and earlier. So whether a woman has done something of no legal interest or something of the greatest possible legal significance can change within a year. This is to make legal judgment—and the status of a human creature under the law—dependent to a disturbing degree on medical technology.

Moreover, Linker’s judgment about the “moral worth” of pre-viability fetuses is pretty shaky as well. There’s nothing wrong with that as a matter of personal feeling, though (as I suggested earlier) I’m not convinced that his personal feelings about zygotes—his moral intuitions about them—are as universal as he claims that they are. And that’s a problem with his case, because he grounds his entire approach to the legal status of fetuses in those feelings and intuitions. If almost everyone does share those intuitions, then maybe that will work as a matter of practical jurisprudence; but ethically it’s pretty dubious. After all, it hasn’t been that long since widespread intuitions about the “moral worth” of black people led to catastrophic evil. (And the leftovers of those intuitions are still poisonous for black people in America today.)

I appreciate, and even value, the general point that underlies Linker’s argument: that sometimes our laws have to be based on fallible and not especially consistent moral intuitions; that ad hoc reasoning is sometimes the best that we have; that the attempt to impose absolute consistency on our laws and jurisprudence is almost necessarily quixotic and prone to the generation of unintended consequences, because, as the adage rightly goes, hard cases make bad law. But I think our track record as a species—and more particularly as Americans—suggests that rough-and-ready moral intuitions do very little to protect the weak, the powerless, the despised. We need stronger and (yes) more consistent legal and moral stuff to protect those who cannot protect themselves.

Alan Jacobs is a Distinguished Professor of the Humanities in the Honors Program at Baylor University in Waco, Texas, and the author most recently of The Book of Common Prayer: A Biography.