Perhaps as many as half of all the products of human fertilization fail to implant in the mother’s womb. Yet many pro-life thinkers, myself included, believe that a human embryo is a human person, entitled to the same moral respect as are other living members of the species, members we see walking and talking and interacting in our daily lives. This moral respect is, we hold, certainly incompatible with the deliberate taking of human life for the sake of scientific benefits for other members of the species.

Can a pro-life thinker, however, hold this position and acknowledge the very high rate of embryo loss that occurs at the earliest stages of pregnancy? A contrary argument might proceed in one of two ways. A first style of argument would suggest that we could only maintain our pro-embryo view if we were also willing to acknowledge natural embryo loss as among the worst tragedies of our day, a tragedy calling for a massive increase of aid to embryos whose lives are jeopardized by this phenomenon. Yet few, if any, pro-lifers are willing to take this step.

A second style of argument would hold that the phenomenon of natural embryo loss is inconsistent with embryonic humanity and personhood. This argument is most often made using religious premises: Could an omnipotent and benevolent God permit the death of so many young and innocent human beings? Or is the fact that these deaths are divinely permitted not evidence for the non-humanity, and non-personhood, of these early embryos?

Both arguments are flawed; neither gives the pro-life defender of the embryo good reason to rethink her position, a position that is based firmly on the results of contemporary embryology and developmental biology. Embryo science, as Robert P. George and I show in our book Embryo: A Defense of Human Life, tells us unequivocally that each of us came to be at fertilization, when a male sperm penetrated a female oocyte; at that time, there was a new, whole, living individual member of the human species, biologically distinct from his or her parents (for sex is, at this point, already determined) and possessed within itself of the genetic and epigenetic primordia necessary for being the executive of its own growth and development to the more mature stages of human existence. (Technically this is only true for the vast majority of us, as some of us came into being as a result of monozygotic twinning, and some of us could come to be as a result of human cloning.)

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Of course, the fact that each of us came from the fertilization of a human egg by a human sperm does not mean that each act of fertilization resulted in a human being. As standard embryology textbooks point out, many of the unsuccessful pregnancies at issue are actually due to failures or defects in the process of fertilization. As a result, what is lost in many cases is not a human embryo. For example, a defect in fertilization resulting from the penetration of an ovum by two or more sperm may give rise not to an embryo but to a hydatidiform mole. To be a complete human organism (a human being), an entity must have the epigenetic primordia for a functioning brain and nervous system; that is, it must, in virtue of what it already biologically is, be able to develop the natural capacities of a human being. So the numbers involved in natural embryo loss are, in all likelihood, not as high, and perhaps not nearly as high, as those who raise the objection sometimes suggest.

Nevertheless, we are willing to grant that there are a high number of losses early in pregnancy that really do involve the premature death of young human beings. So what, given that admission, can one say in response to the two arguments?

My first response is, I think, essential to keep in mind in the debates over embryo-destructive research and abortion. As a matter of political morality, it is the state’s first task to protect all human beings within its borders from aggression and attack. While the state also must promote the positive well-being of its members, this task must be guided by political prudence, and requires difficult choices over the use of finite resources. There is no political obligation to promote every aspect of the well being of every member of the state to the maximum degree. But a state that permits violence against its citizens (much less a state that encourages and funds such violence) radically fails in its primary mission as a state. Thus, our response to the phenomenon of natural embryo loss must always bear in mind that such loss involves no killing, whereas embryo-destructive research and abortion manifestly do.

This response clearly bears in a special way on the first argument which claimed that natural embryo loss should be viewed as our day’s overwhelming tragedy, demanding a massive increase of resources to prevent it. Given that promotion of the well-being of a state’s members is still an important task, albeit not the first task, of the state, is it then, as the argument suggests, hypocritical that pro-lifers do not identify embryo loss as the most pressing issue of our time?

Some preliminary points: First, it is not as if nothing is done to prevent early embryo loss. Would-be parents are encouraged to get proper nutrition, to give up smoking, and to stop drinking, and to get some exercise. Scientists study early embryo loss to determine what other factors, such as hormonal disruptions, might be at work, with a view to correcting these problems if possible. Second, it is not as if there is one pathology or disease that is responsible for all incidents of early embryo loss. This makes analogies to a single disease that wipes out a corresponding number of adults highly inapt. “Early embryo loss” does not pick out a single class of cases that can be uniquely dealt with by means of a narrowly focused strategy.

And finally, of course, early embryo loss strikes in the vast majority of cases before a woman knows or even suspects that she has conceived; moreover, there is only a very narrow window within which pregnancy could be diagnosed and steps taken to prevent embryonic death. There is no practical way in which screening for both pregnancy and concurrent risk could be done on a large scale without, among other things, vast interference with privacy, and vast, and inefficient, expenditure of money, even if, contrary to fact, there were some one condition that was being diagnosed and treated.

Consider, by contrast, what would be the case were we to discover that a large number of early pregnancies spontaneously terminate due to a particular vitamin deficiency. Does anyone doubt that the medical profession—and not just those in that profession who self-identify as “pro-life”—would immediately go on the offensive to ensure a higher level of awareness and compliance with the newly discovered nutritional needs? And yet, even in that case there would be a limit to what could be done, consistent with a reasonable concern for privacy and autonomy, to make sure that the vitamin was being taken by all potentially expecting mothers.

These reasons suggest that it is not at all unreasonable, given competing claims, finite resources, and the various practical problems just described, for states, the medical profession, and pro-lifers generally, to accept early embryo loss as an unfortunate fact of nature for which only limited ameliorating steps can be taken. By contrast, the problem of deliberate destruction of the early embryo, which can only be accomplished when the embryo is in vitro, or by the deliberate ingestion of abortifacient drugs, can much more easily be addressed, and is required by the nature of a state that provides equal protection to all members of the human species within its borders.

What, then, of the second argument? The argument is an inversion of the traditional argument from evil, which seeks to show that the benevolent and omnipotent God must not exist. But as that traditional argument makes clear, the problem of evil is much more pervasive than the phenomenon of embryo loss, encompassing, among other things, a historically high infant mortality rate (comparable at some times and places to the rate of embryo loss), disease, sin, suffering, and so on. And, as traditional responses to the problem of evil have made clear, God’s ways are not ours, and His justifications not, except in those cases where He has communicated them to us, clear or available to us.

Those convinced of the humanity and equal worth of embryonic human beings can acknowledge these truths, and maintain faith in the proposition that God allows no evil without reason, yet continue to believe, as consistent with the strongest moral arguments available, that deliberate destruction of any human being is always morally wrong. And they can hold fast to the claim that this, unlike spontaneous embryo loss in early pregnancy, is a wrong that the state legitimately seeks to prevent as a matter of fairness and justice for its most developmentally immature members.