The debate over “harvesting” stem cells from human embryos has forced policy makers to think about a question that they would rather avoid: When does a new human being begin?

Of course, this is a question that policy makers should have been thinking about in the context of the debate over abortion. They were relieved of that task by the Supreme Court’s misbegotten decision to legalize abortion by judicial fiat. This time no court will let them off the hook.

President Bush has reasserted the ban on federal funding of destructive embryo research, while permitting funding of research involving cell lines derived from embryos destroyed for research purposes during the Clinton years and in the early months of the Bush administration. I and many other pro-life advocates have been critical of the permissive aspect of the President’s decision. It has not, however, satisfied proponents of embryonic stem cell research. Senator Arlen Specter and others in Congress have vowed to come forward with legislation to undo President Bush’s restrictions.

I expect that we will soon see a revival of the so-called compromise proposal floated during the run-up to the President’s announcement of his decision by Senator William Frist—the highly respected and generally pro-life senator from Tennessee who happens also to be an eminent physician. Frist’s idea is to ban the funding of research involving the creation of embryos for stem cell harvesting or other destructive research, while permitting the deliberate destruction of “spare” embryos that come into being as a result of in vitro fertilization efforts (which typically produce more embryos than are desired for implantation). The argument is: If they will be disposed of anyway, why not make good use of them by dismembering them and obtaining their stem cells?

The trouble with the Frist proposal is that it assumes, on the one hand, that embryos are human beings and therefore should not be brought into being for purposes of destructive research—no matter how great the possible scientific and medical benefits; yet, by allowing destructive research on human embryos taken from IVF clinics, it also appears to assume that embryos are not human beings.

Now, defenders of the Frist proposal insist that it does not treat embryos as non-human beings; it simply seeks to find something to salvage from the unfortunate fact that many of these tiny human beings have no real prospects in life. No matter what we do, they will either be frozen or discarded. We therefore do them no real harm—and thus no moral wrong—in dismembering them to obtain their stem cells.

But this defense of the proposal cannot be sustained. We would, I hope, never permit or fund the harvesting of organs from retarded human infants, demented or terminally ill patients, or even death row prisoners. It wouldn’t matter that death was expected in five months, five weeks, five days, or five minutes. Nor would it matter that a dying patient, for example, was unconscious, even permanently unconscious, as a result of a coma or the administration of palliative drugs. Nor would we factor into our deliberation any consideration of the promise of what science or medicine could do with the organs. We wouldn’t tolerate killing for purposes of harvesting body parts because it is inconsistent with the inherent dignity of human beings—even human beings on the verge of certain death, indeed, even criminals about to be executed.

Of course, my Princeton colleague Peter Singer and other outright utilitarians deny that there is a principle of inherent human dignity that stands as an absolute bar to killing some people for the sake of a putative “greater good.” So they typically see no moral reason not to dismember living embryos for their stem cells. By the same token, they see no moral reason not to kill human beings at any stage of maturity when, as they suppose can happen, some calculus of utility tips the scales in that direction. Hence, Singer’s notorious defense of infanticide of handicapped newborns where killing would enable the parents to try again for a healthier child.

Senator Frist and those supporting his proposal rightly do not want to embrace utilitarianism. So they must face the question: Are embryos, or are they not, human beings?

What is a human being? He or she is a whole, living member of the species homo sapiens. Plainly gametes (sperm cells and ova) are not human beings. They are parts of other human beings. They lack the epigenetic primordia for internally directed growth and maturation as a distinct, complete, self-integrating, human organism. The same is true of somatic cells (such as skin cells), even though such cells can provide the genetic material necessary to bring into existence by cloning a new and distinct human being.

Modern science shows that human embryos, by contrast, are whole, living members of the human species, who (unless prevented from doing so) are actively developing themselves to the next more mature stage along the continuum of development of a single, unitary human organism. They are capable of directing from within their own integral organic functioning and development into and through the fetal, infant, child, and adolescent stages of life and ultimately into adulthood as, in each case, determinate, enduring whole human beings.

It is not that a human embryo merely has the potential to “become a life” or “become a human being.” He or she (for sex is determined at the beginning of life) is already a living human being. His or her potential is precisely to mature as the kind of being he or she already is, viz., a human being. In this crucial respect, the embryo is like the fetus, infant, child, and adolescent.

A useful way of putting the decisive question is to ask whether you or I or any other adult was ever an embryo. Certainly you or I were never a sperm or ovum. Although we came into being by virtue of the union of these gametes, conception was an event marked by what some philosophers call “substantial change.” A sperm cell which was part of the father and not a distinct self-integrating organism, and an egg cell, which was part of the mother and, again, not a distinct, self-integrating organism, united to bring into being a distinct, self-integrating organism that is organically part of neither the father nor the mother. From the very beginning, whether conceived within the mother’s body or in a petri dish in an IVF laboratory, the new human being has his or her own genetic constitution, different from that of the mother or father, and the same DNA sequence that he or she will have in every cell of his or her fully developed body.

The being that is now you or I is the same being that was once an adolescent, and before that a toddler, and before that an infant, and before that a fetus, and before that an embryo. To have destroyed the being that is you or me at any of these stages would have been to destroy you or me.

In the current debate, the question whether a human embryo is a human being is usually ignored or evaded. When it has been faced, the arguments advanced for denying that embryos are human beings have been astonishingly weak. (Understandably, proponents of destructive embryo research have tried to shift the focus to its potential benefits.) Some commentators say that human embryos don’t “look like” human beings. The answer is that they look exactly like the human beings they are, that is, human beings in the embryonic stage of their existence. You and I once looked like that. Others try to make something of the fact that embryos are tiny, or very immature, or dependent for full development upon implantation. Senator Orrin Hatch—whose defection on the stem cell issue was a great blow to the pro-life cause—has gone so far as to make the location of an embryo—in a dish or refrigeration unit rather than in a mother’s womb—determinative of its moral status. But anybody who gives the matter some thought should recoil from the idea that factors such as size, stage of development, location, and state of dependency can be a basis for denying rights to human beings.

Then there is the claim that the argument for the human status of the early embryo depends on controversial religious premises about “ensoulment.” It does not. The question is not about embryos’ eternal destiny. That is a religious matter. (One on which the Catholic Church, by the way, has no official position.) The question is whether embryos are or are not whole, living members of the species homo sapiens; whether they are or are not distinct, self-integrating organisms with the capacity for active self-development and maturation as human beings; whether the organism that is now you or me is or is not the same organism—the same being—that at an earlier point in its biography was an embryo, just as it was a fetus, an infant, a child, and an adolescent.

There is no need for those of us who oppose embryo destruction to appeal to religion. The science will do just fine. (If anything, the theological judgment that the early embryo is already “ensouled” follows from the fact—established by science—that it is a human being; not the other way round.) We would be very pleased if those on the other side would agree that the scientific facts about when new human beings begin should determine the question whether government should fund research requiring their deliberate destruction.

Reason magazine science writer Ronald Bailey, to his credit, has at least made the effort to present a scientific case on the other side. He argues that the possibility of cloning human beings from ordinary somatic cells, such as the skin cells millions of which each of us rubs or washes off our bodies on any given day, means that human embryos are no different in moral worth from such cells. Bailey’s argument fails, though, because his analogy between somatic cells and human embryos is doubly false. First, the “potential” of somatic cells is merely that something can be done to them so that their constituent DNA molecules can be used to generate a new human being (precisely in the form of a human embryo, by the way). By contrast, embryonic human beings already possess the active capacity to develop themselves to further stages of maturity of the kind of organism each already is, retaining intact their distinctness and identity. Second, somatic cells are, like sperm cells and ova, parts of other, larger organisms. They are not, and human embryos are, distinct, self-integrating organisms internally directing their own growth and maturation.

An even more esoteric argument denies that the early embryo is a human individual because of the possibility of monozygotic (i.e., identical) twinning. Up until the point at which twinning can no longer occur, what exists, some have asserted, is not yet an individual, but only a mass of cells—each cell totipotent (i.e., capable of becoming a complete individual) and (the argument runs) independent of the others.

If at this early stage a cell or cells is detached from the whole then what is detached can indeed become a distinct organism with the full potential to develop to maturity. But it is simply fallacious to infer from this fact that before detachment the cells within the human embryo constitute merely an unintegrated, and thus incidental, mass. Just as separated parts of a flatworm have the potential to become a whole flatworm when isolated from the present whole of which they are part, separated parts of the embryo at the earliest stage of development before specialization by the cells has progressed very far, can become whole and distinct embryonic human beings. No one supposes that the possibility of producing separate flatworms by dividing a single creature means that flatworms that could be separated, but have not been, are anything other than unitary individual organisms. Similarly, it is wrong to suppose that the totipotency of the early embryo means that it is other than a distinct, unitary, complex, actively self-integrating human organism—a human being.

My friend and co-author Patrick Lee has pointed out that even at the earliest stages of the embryo’s life its cells manifest significant specialization and differentiation:

From the very beginning, even at the zygote stage, the cells of this new organism are cytoplasmically and positionally differentiated. In mammals, even in the unfertilized ovum, there is already an “animal” pole (from which the nervous system and eyes develop) and a “vegetal” pole (from which the future “lower” organs and the gut develop). After the first cleavage, the cell coming from the “animal” pole is probably the primordium of the nervous system and the other senses, and the cell coming from the “vegetal” pole is probably the primordium of the digestive system. Moreover, the relative position of a cell from the very beginning (that is, from the first cleavage) does make a difference in how it functions. Again, most (identical) twinning occurs at the blastocyst stage, in which there clearly is a differentiation of the inner cell mass and the trophoblast that surrounds it (from which the placenta develops).

Lee goes on to observe that if the individual cells within the human embryo prior to twinning were each independent of the others, as the argument under consideration presupposes, then each would be expected to develop on its own. But that is not what happens.

Instead, these allegedly independent, non-communicating cells regularly function together to develop into a single, more mature member of the human species. This fact shows that interaction is taking place between the cells within the zona pellucida, restraining them from individually developing as whole organisms and directing each of them to function as a relevant part of a single, whole organism continuous with the zygote. Thus, prior to an extrinsic division of the cells of the embryo, these cells together do constitute a single organism, and twinning is a phenomenon biologically equivalent to cloning.

The last refuge of those who are bent on justifying destructive research on embryonic human beings, but wish to avoid the collapse into utilitarianism, is to claim that human beings in the embryonic stage, while possessing “some” value, are not yet “persons” with rights. This, apparently, was the position of President Clinton’s National Bioethics Advisory Committee, under the chairmanship of Princeton’s former president Harold Shapiro. It will not do. You and I are essentially human, physical organisms. In other words, we do not “have” organisms that we (considered as conscious and desiring agents) possess and use; rather, we are rational-animal organisms. Therefore we—that is, the persons we are—come to be precisely as and when the animal-organisms we are come to be. One does not become a person only sometime after one comes to be. The human person is a bodily entity—not a mere consciousness inhabiting and using a body—so all human beings, including embryonic human beings, retarded human beings, and frail, demented, and dying human beings, are “persons” whose rights deserve respect and protection.

The concept of the “human non-person”—a human being whose life can be deliberately destroyed, or who can be mutilated or enslaved, to serve the interests of others—richly deserves the ignominy in which it has come to be held. Let us not accept the devil’s bargain of reviving it in return for the hope of scientific advances or for any other reason.