Embryonic Issues

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January 22, 2007 1:00 PM

Embryonic Issues

To the Editor

Dear Professors Lee and George,

Thank you for responding to my letter, which took issue with points raised in your earlier NRO review of my book Challenging Nature. In your response, you continue to insist absolutely — as you have in numerous articles published on this topic — that a human embryo is a human being, while other clumps of human cells are something entirely different. Rather than continuing to debate this claim in prose, it is useful to take a more visual approach, as illustrated by comparing the two pictures below. Both show color-enhanced scanning electron micrographs of clumps of human cells. But before they were frozen for microscopy, one clump was a normal embryo, while the other was a bunch of embryonic stem cells. According to your logic, one clump was a human being, while the other was just a confined group of proteins, DNA, and other molecules. So tell me, Which one is which?

Perhaps you can’t tell the difference by external appearance alone (I certainly can’t). But even if you could look inside with the finest microscope, it almost certainly wouldn’t help because there is almost certainly no molecule, or combination of molecules, whose presence or absence distinguishes all human embryos from embryonic stem cells. At this point, you may retreat to your previous claim that only the real human embryo has “the epigenetic primordia for a functioning brain and nervous system.” I haven’t a clue what the term “epigenetic primordia” means since it has not been used (as far as I know) by any scientist in any of the hundreds of thousands of basic biological research articles published over the last decade.

I know this little exercise won’t change your mind; I present it simply for the benefit of more open-minded NRO readers. Indeed, it is pointless to debate scientific details when even simple words like “life” and “death” are interpreted by you in ways that are foreign to most practicing biologists. So instead, I would like to put to the test your ‘argument from authority’ claim, which holds that the embryo-is-a-human-being proposition “is a fact confirmed by contemporary embryology and attested to by the standard works in the field.” In fact, none of the standard texts you’ve quoted — or any other prominent biology textbook used at major nonsectarian universities — actually states that an “embryo” is a “human being?” (It won’t do to pretend that biologists use the term “human life” as a standard synonym for “human being.” Human cells growing and dividing indefinitely in petri dishes are fully alive — in biological terms — and fully human in their constituent parts, and yet you yourselves do not consider them to be human beings.)

Furthermore, if the embryo-is-a-human-being proposition really is “confirmed by contemporary embryology,” you might expect at least one of the 52 active professors in the two biology departments at the esteemed university where Professor George and I teach to acknowledge this supposedly confirmed “fact.” I challenge Professor George to identify one — just one — Princeton biology professor who shares this viewpoint. (As an incentive, if you can come up with one name, I will buy you both a case of wine from the same vineyard that produced the delightful bottle I shared with Professor George at a pleasant dinner some years ago.)

If your search for like-minded Princeton biologists comes up empty- handed, you might argue that the liberal or libertarian milieu of Ivy League science faculties discourages professors from expressing any truly-held conservative views. But, in fact, many unabashed, culturally conservative academics simply don’t agree with you either. One who takes exception is University of Chicago professor Leon Kass, the former chairman of President Bush’s Council on Bioethics, on which Professor George also sits. Kass has written, “I myself would agree that a blastocyst [an embryo that is 4 to 9 days post- fertilization] is not, in a full sense, a human being.” (Toward a More Natural Science, p.104). Not only is Professor Kass an accomplished scholar in the area of bioethics, he also holds both a medical degree and a Harvard Ph.D. in biochemistry. I assume, Professor George, that you’ve had many chances to persuade Professor Kass with your “careful argumentation and the presentation of the relevant biological facts,” and (as far as I can tell), you haven’t succeeded. Indeed, from my admittedly subjective point of view, it seems that most academic biologists, most nonsectarian bioethicists, most physicians, and most university-educated conservatives (forget about liberals and libertarians) don’t agree with you. So what gives. Are they all stupid, ignorant, or disingenuous?

As I stated in my previous letter, there is nothing — no fact or concept — that will ever make you budge from your belief in the unassailable truth of the view that an embryo is a human being. It is this form of absolutism that led me to brand you as fundamentalists, mocked in the title of your original book review. However, since I was not raised or educated in a strictly religious tradition, you could argue that I don’t really understand the difference between fundamentalists and non-fundamentalists. But there’s no need to take my word for it because the self-described practicing-Catholic and conservative pundit Andrew Sullivan reaches exactly the same conclusion about Professor George in his hard-hitting new book, The Conservative Soul. According to Sullivan, George and others who hold his extreme views are fundamentalists. Sullivan explains that “the fundamentalist does not tolerate a diversity of views. There is one truth; and all other pretenders are threats to it, or contradict it . . . Fundamentalists assert a central core idea and then contort or distort reality in order to make it fit their model.” In a world where life and death become entirely divorced from any connection to modern biological understanding, only faith remains. It is faith of a particular type, not science, that drives the belief that the embryo shown in one of the pictures above is a human being, while the other object is not. This sort of faith is not amenable to debate, which is why this will be my final word on the subject.

Lee M. Silver
Princeton University
Princeton, N.J.

Patrick Lee and Robert P. George respond: Lee Silver continues to bluster and spin in an effort to depict people who disagree with him as “fundamentalists” who rely on religious faith, rather than science, for their beliefs about matters of biological fact. It is Professor Silver himself, however, who refuses to face up to the scientific facts about human embryos.

The point at issue is whether human embryos are or are not human beings in the embryonic stage of their natural development. We say they are; Silver claims they are not. Here is another way of putting the question: Does the term “human embryo” refer to something distinct from a human being (in the way that terms like “alligator,” “cotton,” and “stone” — or even terms like “human liver” or “human fingernail” — refer to things distinct from human beings), or does it refer to a human being at a certain stage of development (in the way that terms like “infant,” “adolescent,” and “adult” refer to stages of development)?

Plainly, the complete human organism that is now you, the reader, was once an adolescent and before that an infant. Were you once an embryo? If Silver’s view is correct, the answer is “no.” But the truth is that the answer is “yes” — you were once an embryo, just as you were once an adolescent, a child, an infant, and a fetus. The human organism that is now you is the very same organism that began in the embryonic stage and developed by a gradual and gapless process of self-directed growth to the mature stage of a human being. By contrast, you were never a sperm cell or an ovum. The sperm cell and ovum whose union brought you into existence were genetically and functionally parts of other, larger organisms — your parents. But the organism — the new and distinct human individual — who was brought into existence by their union is the organism that is now reading these words.

It is the science of human embryology — not the Bible or any other religious text or authority — that tells us that human embryos are indeed what we say they are and what Silver denies that they are, namely, whole, living individuals of the species Homo sapiens. As complete human organisms, and not mere parts of larger organisms, embryos are radically unlike human gametes, somatic cells, organs, tissues, and the like. If provided with adequate nutrition and a suitable environment, and barring accident or disease, a human embryo will, by internally directing its own integral organic functioning, develop himself or herself from the embryonic into and through the fetal, infant, child, and adolescent stages, and into adulthood with his or her distinctness, unity, and identity fully intact. What happens in successful fertilization or cloning is the production of a new and distinct organism — a complete individual member of the species in the initial (embryonic) stage of its life. None of Lee Silver’s bluster and spin can make that decisive fact disappear.

Ignoring Arguments
The basis of Silver’s denial that human embryos are human beings is his remarkable claim that human embryos are equivalent to human embryonic stem cells. He argues that, since nobody believes that stem cells are human beings, no one should believe that embryos are human beings. But Silver’s premise is not only remarkable, it is indefensible. In a previous posting, we identified the errors in Silver’s attempt to defend it by reference to the possibility of tetraploid complementation. Silver has not made any effort to resuscitate his argument or respond to our refutation. We also observed that if Silver’s remarkable claim were true, other scientists — particularly human embryologists and stem cell scientists with greater expertise than Professor Silver — would confirm it. Why have they not? Silver’s answer is as remarkable as his claim itself. He asserts that scientists know the truth, but they are deliberately hiding it from the public for fear that if it were revealed people would demand new restrictions on stem-cell research. There is no polite way to say this: Professor Silver’s suggestion that there is a massive scientific deception or cover up is ridiculous.

Equally ridiculous, and grossly hypocritical, is Silver’s claim that we hold a position that is not amenable to debate. This series of exchanges with Professor Silver began when (in an article in Science and Technology News and in his book Challenging Nature) he accused us of basing our position that human embryos are human beings on a “hidden theology.” Silver claimed that our argument for this position depended on the proposition that a thing either is or is not a human being. In our October 3 NRO article, we provided a formal (and we believe decisive) refutation of the argument by which Silver proposed to show that we were implicitly relying on theology in our argument for the proposition that a human embryo is a human being; but Silver has provided no answer at all to that refutation. Moreover, in that same article we presented two additional philosophical arguments to support the proposition he claimed we were relying on theology to believe. But he has offered no reply whatsoever to those two arguments.

While consistently failing to engage the counterarguments we have advanced against him, Professor Silver did offer three arguments against the conclusion we draw, namely, that human embryos are living members of the species Homo sapiens — human beings in the embryonic stage of development. In our October 19 NRO article we analyzed each of these arguments and showed that each is unsound. But — like the argument we presented against his original charge of “hidden theology” — these arguments too have received no reply whatsoever. That is, Professor Silver has not even attempted to show that our arguments are defective. Nowhere does he even try to demonstrate that we have relied on a false premise or proceeded on the basis of an invalid inference.

Instead, Silver simply reprises his bald assertion that we hold our belief that human embryos are embryonic human beings on faith “entirely divorced from any connection to modern biological understanding.” Yet, we have presented a wealth of evidence, cited standard and authoritative scientific texts, and invited Silver to identify factual or logical errors in our arguments. Where he has attempted to do so, we have responded by identifying with specificity errors of fact and logic in his critique of our claims. We have offered extended and detailed arguments based on experience, science, and philosophy — at no point appealing to any authority save the authority of reason itself. We deal in the currency of reasons and arguments; Silver replies with name-calling and arm-chair psychoanalysis. But these antics cannot obscure the fact that Silver has simply left our arguments unrebutted. Presumably, if Silver had answers to our points he would supply them. As it is, he is reduced to the shabby tactic of labeling us “fundamentalists” and then — in perhaps the most amusing of his diversions — casting about for some authority to validate the charge. What authority does he come up with? To whom does he appeal as an expert to distinguish true Catholicism from fundamentalism? He invokes the authority of the polemicist blogger Andrew Sullivan. Res ipsa loquitur.

Deceptive Appearances
It also is surprising to find Professor Silver, of all people, responding to the barrage of biological evidence we have adduced, by appealing to appearances (albeit enhanced by extremely sophisticated magnification) in an effort to salvage his position. Of course, the fact that humans in the embryonic stage don’t look like humans at later developmental stages is simply irrelevant to the question whether they are in fact human beings at an early developmental stage. The fact that Joseph Merrick — the “Elephant man” — didn’t look like other human beings did not mean that he was something other than a human being. Yet, those who relied on appearances for their judgments could not grasp his humanity, prompting him to exclaim: “I am not an animal. I am a human being. I am a man.” Indeed, he was. By the same token, the fact that an embryo looks like certain non-embryonic clumps of cells does not mean that it is the same thing as a non-embryonic growth or cellular system or a collection of stem cells. To suppose otherwise is to imagine that a sleeping human being or a human being in a temporary or long-term coma is the same thing as a corpse, or that fool’s gold is gold, since they can appear to be identical before inquiry establishes that the sleeping or comatose human is alive and that the fool’s gold is actually pyrite.

But no one has ever asserted that embryos and certain non-embryonic entities or collections of cells are always visually distinguishable or that they are different kinds of things only if they are visually distinguishable. Everyone in this debate knows, and has assumed all along, that embryos at very early stages of their development and certain non-embryonic entities or collections of cells can look alike. Our proposition, fully supported by the standard authorities in human embryology (more on that in a moment), is that scientific inquiry — by observation of their manner of behavior and by genetic and epigenetic analysis — can distinguish them as radically different kinds of things.

Of course, we are assuming — on Professor Silver’s word — that what one of the two micrographs depicts is, in fact, not an embryo but a collection of stem cells. We further assume (for otherwise the case would not be interesting or constitute any sort of challenge) that what he describes as a “bunch of embryonic stem cells” is not, in fact, totipotent — that is, the cells do not constitute a complete, functioning human organism that, if provided with a suitable environment, will by an internally directed process develop itself towards the mature stage of a human individual. If what he describes as a “bunch of embryonic stem cells” were, in fact, a complete, functioning human organism generated asexually by, for example, some method of aggregating and manipulating stem cells, then it would be indistinguishable from an embryo for the simple reason that it is one — in the same way that a cloned human embryo is an embryo.

So, assuming that Professor Silver is accurately and fully describing the two micrographs and is not simply begging the question by offering depictions of two embryos generated by different means, then one micrograph depicts a developing human individual in the earliest stage of his or her natural development — an embryo — and the other depicts a collection of cells that merely visually resembles a developing human in the embryonic stage. Science here, as it does in so many other cases, shows that — and where — appearances and reality part ways. Application of scientific methods would enable a competent and properly equipped embryologist/teratologist to distinguish an actual embryo from a non-embryonic growth or cellular mass which merely visually resembles it.

But Professor Silver makes a further assertion. He claims, not just that the two look alike, but that, “Even if you could look inside with the finest microscope, it almost certainly wouldn’t help because there is almost certainly no molecule, or combination of molecules, whose presence or absence distinguishes all human embryos from embryonic stem cells.” But Professor is merely repeating a scientific error that we refuted in our October 19 article. If a group of stem cells is placed within the normal environment for the gestation of an embryo — a receptive uterus — they do not develop themselves toward maturity. By contrast, if a human embryo is placed within a receptive uterus it will internally coordinate several changes within itself to develop itself to the mature stage of a human organism. That means that the two (the group of stem cells vs. the human embryo) do differ in molecular arrangement, patterns of gene expression, and in one or more cytoplasmic factors. It is precisely these differences that are critically required for (and constitute corroborating evidence of) the radically different developmental trajectories of the two groups of cells (only one of which shows itself to be a unitary organism).

Consulting the Authorities
Next, Professor Silver says: “In fact, none of the standard texts you’ve quoted — or any other prominent biology textbook used at major nonsectarian universities — actually states that an ‘embryo’ is a ‘human being.’” In all of our writings on the embryo question we have made it clear — indeed, we have repeatedly, explicitly stated — that by “human being” we mean a whole member of the human species (at any stage of his or her development), or complete human organism (though perhaps at an immature stage). And it is a simple fact that the texts we quoted do teach that human embryos are whole living members of the species Homo sapiens and complete human organisms at the earliest stage of their development. Indeed, these texts identify the coming to be of the human organism — the human individual — with the coming to be of the zygote. Speaking of the zygote formed at fertilization, Keith Moore and T.V. N. Persaud say: “This highly specialized, totipotent cell marked the beginning of each of us as a unique individual” (p.16, emphasis supplied). Ronan O’Rahilly and Fabiola Mueller say that, at fertilization, “under ordinary circumstances, a new, genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte” (p. 8, emphasis supplied). And William Larsen says that the gametes “unite at fertilization to initiate the embryonic development of a new individual” (p.1). (Of course, that individual is not an individual spider or goat. Larsen is talking about a human individual. And he is not talking about a mere part of a human individual, like a bit of human tissue or a fingernail or liver. He is talking about a whole, albeit developmentally immature, human individual, viz., a human being.) Bruce Carlson, a distinguished professor of human embryology at the University of Michigan Michigan (a “non-sectarian university,” let us assure Professor Silver, since that kind of thing seems to matter so much to him) and author of a leading text, recently testified under oath as an expert witness in embryology in a case now pending. There he stated explicitly that human embryos are human beings: “the human being is created immediately after fertilization, and the maturation process and growth is a seamless continuum.” Can Professor Silver identify a human embryologist of the stature of Professor Carlson who is prepared to go under oath to contradict him?

In our October 3 NRO article, we began by speaking of “human beings in the embryonic stage of development.” In this same paragraph we said: “The complete human organism — the whole living member of the species Homo sapiens — that is, for example, you the reader, is the same human individual that at an earlier point in his or her life was an adolescent, a child, an infant, a fetus, an embryo.” This is precisely the teaching of Moore and Persaud, O’Rahilly and Mueller, Larsen, Carlson, and other leading human embryologists.

Keeping to the Scientific Question
We have also made it clear that the evaluative question of whether every human individual is a subject of rights is a distinct question from that of whether every human embryo is a human individual. Some philosophers have argued that not all human individuals, or human beings, are persons, and we have presented philosophical arguments to show why that position is mistaken. However, some people use the term “human being” as expressing an evaluative concept, synonymous with “person,” rather than as expressing a biological concept, synonymous with “human individual” or “whole member of the human species.” When Silver says that none of the texts we cited say that human embryos are human beings (or when he challenges us to find one of his Princeton biology colleagues who says that embryos are human beings) he is trading on this linguistic ambiguity and the understandable desire of scientific writers to steer clear of ethical or evaluative questions in describing facts.

But we have made clear that by “human being” we mean the biological reality of a whole, living individual of the human species. And on this the embryology textbook writers are perfectly in line with our view and offer Silver no support at all. The simple question of fact with respect to what the standard embryology texts say is whether they do or do not agree that human embryos, from the zygote stage on, are whole human organisms — whole (though immature) members of the human species. An examination of the short quotations given above, and the longer ones provided in our October 19 NRO article, shows that the standard embryology texts do unequivocally affirm that human embryos are whole human individuals, complete human organisms, individual members of the human species, “human beings” precisely as we have defined the term in our writings. It is what Robert Edwards meant when — speaking of the newly conceived Louise Brown — he straightforwardly and accurately described her as a “microscopic human being.” Writing years after her birth, he noted that the human individual that was by then scampering through the schoolyard was the very same human individual that he had observed in the petri dish: “She was beautiful then,” Edwards declared, “and she is beautiful now.” That embryo was not some pre-human creature that only later became Louise Brown. That was the embryonic Louise Brown — the same individual, the human being — who would a few years later scamper through the schoolyard.

Of course, we have also taken note of the fact that some supporters of abortion and embryo-destructive research acknowledge that human embryos are human beings, but deny that they are “persons,” i.e., individuals possessing inherent dignity and a right to life. Such people typically claim that human beings acquire dignity and rights only after coming into being (if they acquire them at all) and may cease possessing dignity and rights prior to dying. They maintain that some humans (embryos, fetuses, even infants) are not yet persons; others (human beings in permanent comas or those suffering from advanced dementias) are no longer persons; and still others (severely retarded individuals) were never, are not, and never will be persons. They identify “personhood” with possession of the immediately exercisable capacity for a certain level of cognitive functioning. So we have separately argued for the further proposition that every human being, irrespective of age, size, stage of development, or condition of dependency possesses inherent dignity and a right to life. The question whether all, or only some, human beings are “persons” is a philosophical one. In this respect, it is unlike the biological question of whether human embryos are human beings. So the arguments we (and others) advance in support of the proposition that all human beings are persons are philosophical, rather than biological, arguments. Even here, though, we do not appeal to religious faith or authority.

Changing His Mind
This takes us to Professor Silver’s attempt to use Dr. Leon Kass as an authority against our view. Silver rightly emphasizes Kass’s standing as an accomplished scholar in bioethics who holds both a medical degree and a Ph.D. from Harvard in biochemistry. He notes that Kass is the former chairman of the President’s Council on Bioethics and that one of us (Robert George) serves with him on the Council. Silver then quotes Kass as writing, “I myself would agree that a blastocyst [an embryo that is 4 to 9 days post-fertilization] is not, in a full sense, a human being.” Then Silver tauntingly goes in for what he thinks is the kill: “I assume, Professor George, that you’ve had many chances to persuade Professor Kass with your ‘careful argumentation and the relevant biological facts,” and (as far as I can tell), you haven’t succeeded.”

Well, let’s see about that.

We’re delighted that Professor Silver has chosen to bring Leon Kass into this discussion as an authority on the issue in dispute. Kass is a giant among bioethicists and a person whose knowledge of the relevant science is beyond dispute. Moreover, he is a scholar of the highest intellectual integrity: a man who carefully weighs facts and follows arguments wherever they lead — even when the conclusion they generate requires him to revise his position. The quotation Silver is trying to use against us is from an essay written by Kass 28 years ago and reprinted in his 1985 collection entitled Toward a More Natural Science. What Silver does not reveal — we hope it was because he was not aware of it, although that would be odd — is that when Kass republished the essay in 2002 (after his appointment as chairman of the President’s Council on Bioethics) in his widely distributed and much discussed book Life, Liberty, and the Defense of Dignity, he added the following sentence to the relevant paragraph: “One could go even further: the in vitro blastocyst is exactly what a human being is at that stage of human development. Only its extracorporeal location is different.”

On the crucial question of biological fact in this dispute, then, Kass turns out to be a witness for our position and against Silver’s. Even more embarrassingly for Professor Silver in view of his taunting claim that George had failed “to persuade Professor Kass with your ‘careful argumentation and the relevant biological facts,’” Kass has explained his reason for revising his text to include an affirmation of the humanity of the embryo. Writing to George, he said that the reason was “precisely because you persuaded me that my earlier formulation [that is, the one quoted so triumphantly by Silver] was inadequate.” Kass’s difference with us — a narrow but important one — is not on the science at all, but rather on the difficult philosophical question. Even here, though, his position is far closer to ours than to Silver’s. Unlike Silver, he believes that human embryos have a high moral status and deserve respect far above what is owed to stem cells, gametes, organs, fingernails, etc. And although he does not regard human beings in the embryonic stage as having moral status equal to that of newborns, he concedes that the question is indeed difficult, that important philosophical arguments for the opposing position have been made, and that he has less than complete confidence in his own position. For that reason, he has firmly, consistently, and publicly taken the view that we should not treat any stage of nascent human life — which, he holds, at all stages should elicit awe and respect — less well than it might deserve.

There is another bioethicist well known to Professor Silver who disagrees with us far more radically on the philosophical question but has asserted with respect to the biological question the very position we hold and Silver denies. In his book Writings on an Ethical Life, published in 2000, Peter Singer stated that the proposition that a human embryo is, as a matter of biological fact, a human being is not only true, but beyond doubt:

It is possible to give “human being” a precise meaning. We can use it as equivalent to “member of the species Homo sapiens.” Whether a being is a member of a given species is something that can be determined scientifically, by an examination of the nature of the chromosomes in the cells of living organisms. In this sense, there is no doubt that from the first moments of its existence an embryo conceived from human sperm and egg is a human being. (emphasis supplied)

Now we don’t know whether Singer continues to hold this view, though the scientific evidence in its support has only strengthened in the six years since he stated it with such certitude. (On the respects in which the evidence has grown even stronger, see Helen Pearson, “Developmental Biology: Your Destiny from Day One,” Nature, Vol. 418, Issue 6893, 2002. Nature, Professor Silver can be assured, is a “non-sectarian” scientific journal.) For purposes of our debate with Professor Silver, it doesn’t matter. For Professor Singer was then, as he is now, an atheist. He, like Silver, supports embryo-destructive research and abortion; indeed, he even goes so far as to say that infanticide can be morally justified. Unlike Silver, however, he is willing frankly to acknowledge the truth about these practices: they involve the deliberate killing of human beings. They are, to use the words of another candid supporter of abortion and embryo-destructive research, legal philosopher Ronald Dworkin, “choices for death.”

Conclusion
Let us conclude with a reply to Professor Silver’s allegation that we fail to identify a test by which our central claim about the embryo’s status as a complete and distinct organism can be verified or falsified. The test of whether a group of cells constitutes a single organism is whether they form a stable body and function as parts of a whole, self-developing, adaptive unit. Contrary to Professor Silver’s supposition, this test is clearly passed by a human embryo, and clearly failed by a group of stem cells. As we noted, if a human embryo is placed within its normal environment, namely, a receptive human uterus, then (barring accidents or disease) it will actively develop itself by a coordinated series of self-directed changes to the mature stage of a human organism. By contrast, if a group of stem cells is placed within a receptive uterus, this does not occur. The test of whether it is a whole (though immature) human organism is whether the direction of its growth (if it has one) is toward the mature stage of that type of organism. The human embryo clearly passes that test, but the group of stem cells fails it.

An embryo and a stem cell are not the same thing, any more than an adult human and a liver or stomach is the same thing. The embryo, like the adult, is a self-integrating whole, a complete member of the species at a certain developmental stage. The stem cell, like the liver, is merely a part. The human embryo, fetus, infant, child, adolescent, and adult differ not as to what they intrinsically are — they are human beings — but in respect of their age, size, stage of development, and condition of dependency.

Once that biological truth is firmly in view, one can then shift to the key ethical question: Do human beings possess inherent and equal dignity? Or does the dignity of a human being depend upon or vary with his or her age, size, stage of development, or condition of dependency? Our view, which we have defended in various writings, is that the dignity of human beings is inherent and that all of us, as members of the human family, are created equal.

— Patrick Lee is professor of bioethics at the Franciscan University of Steubenville. Robert P. George is McCormick Professor of Jurisprudence and director of the James Madison Program at Princeton University.

Lee's and George's second response

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October 19, 2006 8:39 AM

Silver Lining
A reply to Lee Silver.

By Patrick Lee & Robert P. George

We thank Professor Silver for his response . On the basis of this exchange, we are confident that readers will be able to judge whether Professor Silver’s claim that human embryos are something other than what we say they are, namely, human beings in the earliest stage of their natural development, can withstand scrutiny in light of the findings of modern embryological science.

Are Human Embryos Human Beings?
Silver claims that while many people believe that human embryos are human beings, what sets us apart is that we contend that this is a matter of scientific fact, rather than a proposition of faith. But we are scarcely set apart by this claim. On the contrary, our claim that the human being that is, say, you the reader, is the same determinate and enduring being — the same individual member of the species Homo sapiens — who at an earlier stage of his or her life was an adolescent, a child, an infant, a fetus, and an embryo, is a fact confirmed by contemporary embryology and attested to by the standard works in the field. (We mentioned several of these works in the essay to which Silver responds; he cites none in support of his position.) Terms such as human “adolescent,” “infant,” and “embryo” do not refer to beings of distinct kinds; rather, they refer to the same kind of being — a human being, an individual member of the species Homo sapiens — at different developmental stages. You were once an embryo, just as surely as you were once an adolescent, and before that a child. So that readers will be left in no doubt, let us quote a couple of the standard texts. Keith Moore and T.V.N. Persaud, in The Developing Human: Clinically Oriented Embryology, perhaps the most widely used of the embryology texts, make the following unambiguous statement about the beginning of a new and distinct human individual: “Human development begins at fertilization when a male gamete or sperm (spermatozoon) unites with a female gamete or oocyte (ovum) to form a single cell — a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual” (p.16, emphasis supplied). Ronan O’Rahilly and Fabiola Mueller, in their book Human Embryology and Teratology, say this: “Although life is a continuous process, fertilization (which, incidentally, is not a ‘moment’) is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte” (p. 8, emphasis supplied).

An even weaker point advanced by Silver is his complaint that we “have not budged” in our rejection of Ronald Bailey’s claim that embryos are analogous to skin cells or other somatic cells that can be used (it is assumed) in human cloning. People who recall our exchanges with Bailey on NRO know that our rejection of his proposed analogy has nothing to do with stubbornness. Rather, we showed by careful argumentation and the presentation of the relevant biological facts that somatic cells are analogous not to embryos — which are complete self-integrating organisms that are, as the standard scientific texts attest, new individuals of their species — but rather to gametes (sperm and egg) whose union can bring into existence a new and distinct individual in the embryonic stage of its development.

Parts and Wholes
Let us turn now to two key propositions in our argument that human embryos are human beings. Silver disputes these propositions. We said that human embryos are (embryonic) human beings because they are complete human organisms that “have an internal active disposition toward the mature stage of a human being.” Silver disputes this proposition. He claims that “we know that a single cell can separate from a 4- cell embryo and develop into a separate human baby (on rare natural occasions).” According to him, “Lee and George would argue that this cell has the ‘internal active disposition’ that makes it a human being.” But this would be inconsistent with our position that ES cells are not human beings because they lack such an active disposition to develop to maturity.

Silver here commits the error of confusing a part with a whole. When the cell is part of the whole multi-cellular organism, it lacks any disposition to develop on its own: for, if it is not split off, then it will continue to act in coordination with other cells along a trajectory toward the mature stage of development of the organism of which it is a part. If the splitting of the cell from the whole embryo results in a new embryo, this is a form of asexual reproduction, and an example of what evidently occurs in normal monozygotic twinning. So the fact that a single cell could be separated from a four-celled embryo and produce a second embryo is completely consistent with our position that embryonic-stem (ES) cells are not human beings because they lack this internal active disposition.

Developmental Trajectories
Silver then claims that “an internal active disposition” “is not a term that has any meaning in the context of cellular or molecular biology.” But this is mere bluster. The concept of a disposition or tendency is scarcely foreign to scientific contexts, where one speaks, for example, of the solubility of salt (sodium chloride) or of sugar (sucrose) and their variance in relation to temperature; for, solubility is a disposition, a tendency to do something in a given context. We added “internal” and “active” to distinguish it clearly from the (merely passive) capacity of something to be changed by being acted upon by an extrinsic agent. Thus, when biology books refer to the capacity for metabolism as being one of the marks of a living system, “capacity” refers to the same sort of thing we were referring to by the term “internal active disposition.” We could also have used the term “developmental trajectory” or “developmental program” to make the same point. An organism with a single developmental trajectory toward the mature stage of a human being is already a human being.

Moreover, dispositions or developmental trajectories in organisms have structural bases; that is, present in the organism are constituents and arrangements (organization) responsible for the active disposition or developmental trajectory. So, when Silver next claims, “If George and Lee want to claim otherwise [namely, that “internal active disposition” does have a meaning in the context of cellular and molecular biology] I’d like to know their perception of the molecular attributes that distinguish human being-cells from non-human-being, yet still fully viable and human cells” — we are happy to inform him. At the one-cell stage, comparing a zygote to, say, a stem cell, the one-celled embryo differs epigenetically from the stem cell (that is, while each has the complete genome there are differences in the activation or silencing of various genes).

But that is not all, for there are also differences with respect to several cytoplasmic factors. The embryo is such that, unlike a stem cell or any other somatic cell, its whole developmental program, both the epigenetic state of its DNA and various proteins and RNA factors in its cytoplasm (differences that are fully discernable at the molecular level) enable it to develop along a trajectory towards developmental maturity. At later stages of development, each of the cells of the embryo will differ from a separated stem cell or from other somatic cells — among other ways — in being modified by interaction with other cells within the embryo in such a manner as to contribute to homeostasis and the development of the organism as a whole. Therefore, “in the context of cellular and molecular biology,” a single-cell human being (i.e. a zygote) is distinct from any other viable human cell in terms of 1) its epigenetic state, 2) its pattern of gene activation, 3) its molecular composition, and 4) its subsequent pattern of development — all of which can be (and indeed are) easily determined by scientists without recourse to crystal balls, sacred texts, or articles of faith.

Are Embryonic Stem Cells Human Beings?
In an astonishingly misleading paragraph, Silver quotes from a quick summary given by a reporter from Science magazine about a meeting of scientists working on gene knockouts (a procedure in which, by a complicated process, a gene is deactivated — “knocked out” — in a mouse in order to discover what that gene’s normal function would be). Suspecting something fishy, we took the trouble to look. The scientists were examining how they could cooperate more effectively on an international level. In the past they had shared research data and materials in part by shipping mice that had been engineered with a certain gene knockout. Silver quotes the reporter summarizing their discussion as follows: “the participants agreed that it would be most economical to avoid trafficking in live mice and instead decided to maintain the knockouts as embryonic stem (ES) cells: clumps of tissue that can be frozen down and later grown up into full-fledged mice.” Professor Silver takes this as evidence that “[t]hose…who have worked only with early-stage mouse embryos” are more honest than scientists who work on human stem cells when speaking “about the relationship of embryos to stem cells.” In other words, Silver presents this quote as proof from authority that stem cells really are the moral equivalent of embryos (because they can somehow “by themselves” grow into embryos).

However, first, it is clear that the reporter is merely trying to summarize quickly the conclusions of a long meeting of stem-cell scientists; he is not attempting to select his words with exactitude, and much less is he addressing the issue in dispute between Professor Silver and ourselves. Silver is making much out of what is manifestly nothing more than a reporter’s shorthand manner of speaking. The article from Science is available online. We urge readers who are evaluating Silver’s arguments against our own to examine this article for themselves.

Moreover — and much more significantly — Silver fails to mention that the knockout procedure involves first knocking out a specific gene in mouse stem cells, then injecting those stem cells into an early mouse embryo, where the manipulated stem cells will be randomly incorporated into the body of the developing embryo. In some of the chimeric mice formed in this manner, the stem cells will contribute to the gonads, and therefore the germ cells produced by the mature animal will also lack the gene that was eliminated from the stem cells. In this case, by “back crossing” such “germ line deficient” mice (i.e., inter-breeding the male and female offspring of the mouse carrying the gene deletion), ultimately a mouse is produced that lacks the knocked out gene in all the cells of its body, and the phenotype that results from the loss of that gene’s action can be determined. The point the scientists were making was simply that it would be more economical and efficient to ship to other sites the manipulated stem cells rather than the mice with the gene knockouts, largely because many such knock-out mice are quite unhealthy, and therefore they are difficult to breed and expensive to maintain. When the scientists described the ES cells (or, more precisely, when the reporter recounted them as describing the ES cells as) “clumps of tissue that can be frozen down and later grown up into full-fledged mice,” it was understood — as part of the knockout procedure — that this later “growing up” process would involve injecting those ES cells into mouse embryos. Silver’s selective editing makes it appear that these scientists are asserting something they did not assert, and are speaking to an issue they did not address.

Professor Silver had argued in his book that aggregating mouse stem cells with mouse tetraploid embryos allowed the stem cells to develop “by themselves” into mature mice. We pointed out that the aggregation of the stem cells with tetraploid embryos (or embryo-like entities) does more than release an inner capacity in the stem cells. In fact, it generates a new and distinct organism, just as combining the nucleus of a somatic cell with an enucleated ovum (as in cloning) generates a new organism — in both cases, an embryonic member of the mouse (or other) species in question. In his reply, Silver now says the following:

Furthermore, as I wrote in my book, human ES cells have already been differentiated into placenta. This means that, in theory, the requirement for a second source of cells to reconstitute an embryo may be nullified, and ES cells — all by their lonesome — could develop into a fetus and human baby. This discussion was conveniently left out of Lee and George's review.

This is supposed to show that stem cells really are equivalent to embryos because they can “by themselves,” or “all by their lonesome,” develop into mature members of their species. However, this argument is dubious at best, given that there is no evidence that an embryo could be generated by recombining ES-cells that have been “differentiated into placenta” with an undifferentiated ES cell, and there is sound scientific evidence to suggest embryos cannot be generated in this manner. In fact, the second article Silver cites in his book on this subject is much more cautious in its conclusions than Silver himself is. The authors write;

The human equivalent to trophoblast stem cells has not yet been derived, and it is likely that different growth factors will be required for their propagation.[note omitted] Although, in our current studies, BMP4 efficiently induced differentiation of human ES cells to trophoblast, these trophoblast cells propagated poorly, even in the continued presence of bFGF and fibroblast feeder layers (data not shown), suggesting that additional growth factors are required for their long-term proliferation. (Ren-He Xu, et al., “BMP4 initiates human embryonic stem cell differentiation to trophoblast,” Nature Bioetechnology 20 (December 2002), 1261-1264, at 1263)

Moreover, as partly recounted in Silver’s book, and more fully in the scholarly articles to which Silver refers, the stem cells (in the experiment Silver cites) by no means develop into embryos and fetuses without extrinsic causes in the form of external manipulations. No one denies or has denied that one can manipulate factors found in early stem cells and combined those factors with stem cells in such a way as to generate a new embryo. But just as combining factors from an ovum and a somatic cell to generate a new individual member of a species in the embryonic stage does not show that an ovum or a somatic cell used in the process was somehow already an embryo or its equivalent, the combining and manipulating of factors found in early stem cells does not show that a stem cell is an embryo or its equivalent. The fact that one can combine A (a stem cell) with B (another cell that is produced by a significant manipulation of a stem cell) to produce C, does not in the least prove that A or B were identical with C all along.

A Thing Either Is or Is Not a Human Being
The second proposition of ours that Silver contests, is that a thing either is or is not a human being, that is, that each human being came to be at once, not gradually. Readers will recall that our view is entirely consistent with the biological fact that fertilization is a process. Our point is that a new human being does not “partially” exist as the process unfolds. Rather, a new human being is what the process, if it reaches completion, brings into existence. (If fertilization fails, it is not correct to say that a “partial” human was brought into being, or that a human was “partially” brought into being.) Silver notes that we provided several arguments defending our position, but mentions only one, namely, in his words, “that it is simply commonsensical to most people.” He then notes that common sense is often mistaken, as “many examples from science demonstrate.”

Here again, however, what Silver says is highly misleading. First, in Silver’s article in Science and Theology News, he did not just claim that we presuppose the proposition that a being either is a human being or is not; rather, he claimed that it was a “hidden theological premise.” He even went so far as to allege — preposterously — that we adopted this premise from a literal interpretation of Genesis, according to which humans are made in God’s image, and God is absolute, so just as there cannot be a partial God, so there cannot be a partial human. His charge was that we were covertly injecting our “fundamentalist” Christian beliefs into secular-sounding arguments.

Of course, we pointed out that the inference we supposedly made starting from a teaching in Genesis was patently fallacious (i.e., God cannot be partial, humans are made in God’s image, therefore there cannot be partial humans — by the same reasoning one could infer that we must be omniscient, eternal, perfect, and so on). We then pointed out that the idea that human beings come to be at once was part of common sense; the point was to show (along with other arguments) that it was not a premise we had to take from the Bible or Church teaching: Since it is a commonsense idea, it is absurd to suppose that all those who make use of it are covertly smuggling in a literal reading of Genesis. Further, we made a point of stating expressly that just because this idea is part of common sense “doesn’t by itself prove it, but does provide support for it.”

After having given four reasons showing that no one has to appeal, openly or covertly, to revelation in order to hold this position (that something either is or is not a human being), we then moved on to a different task, namely, providing philosophical support for this position. We presented two distinct philosophical arguments. Silver offers no reply at all to either of these arguments. His only attack, and that a weak one, is on the single argument that we expressly said “doesn’t by itself prove” the position we were defending, but merely “provides support for it.”

In his book and article, Silver claims that the assumption that a thing either is or is not some kind of thing must be a hidden theological premise. But he now admits that it might have been adopted from common sense. Moreover, he now even admits that “[i]t is not surprising that so many philosophers have also held this position,” though he adds that, “[t]wo millennia ago, in the absence of modern scientific knowledge and biomedical technology, Aristotle would certainly have convinced me of its veracity.” Thus, Silver has implicitly abandoned the claim that this view depends on covert “fundamentalist” theological premises. But Silver’s attempt to discredit this view by tying it to a philosophical approach that has allegedly been falsified by modern science is equally misleading. First, he ignores the fact that we cited (to show, earlier, that this position was not a hidden theological premise) contemporary as well as ancient philosophers. (We specifically mentioned David Wiggins, Roderick Chisholm, Peter Van Inwagen, and E.J. Lowe, all recent or contemporary analytic philosophers.) Moreover — even if one disagrees with them — no one is likely to accuse any of them of naively following an outmoded, two millennia-old philosophical approach. Further, neither of the two philosophical arguments we presented to defend the proposition at the heart of the debate — arguments ignored by Silver — were lifted from ancient sources.

Daunted by Darwin?
Silver does present an argument against our position that a human being either is or is not — i.e., that there is no entity that is somehow between a human being and a non-human creature. Here is his argument:

The most serious challenge, of course, came from Darwin, whose theory of natural selection suggests that in the evolution of pre-human apes into human beings, there was no first human being. Instead, there appears to have been a continuum of evolutionary forms in a process during which no child was significantly different from its parents. The scientific implication is that some "things" might be in-between non-human and human.

But this argument is fallacious. Darwin proposes at least a partial explanation of the emergence of new species (whether it is a sufficient or complete explanation is another question, which we need not settle here). The idea is that some species evolved from other species, and that the human species evolved from lower animal species, at least with respect to the organic aspect of the human being (whether that is all there is to human nature is another question, which, again, we need not settle in the context of the current debate). But this does not show that there must have been some creatures which were in between humans and non-humans — creatures that were neither human nor non-human. It only shows that certain non-human animals evolved gradually (or perhaps not so gradually — the point is disputed among evolutionary biologists) to become more and more like humans until, at least partly through genetic mutations, the human species (as a distinct and identifiable species) emerged. Nothing in the Darwinian account suggests that there is or was a species that was neither human nor non-human — a species that was “in between” human and non-human.

In other words, if species B evolved from species A though an accumulation of minute genetic changes, that does nothing to show that the last entity just before the last genetic change which (wholly or in part) produced the new species B, must have been something that was partially B. Rather, that last entity prior to B was a non-B that was in a great many respects like a B.

Moreover, the addition of a minute genetic change could be — whether wholly or in part — responsible for a radical change in the properties possessed by a new being. It is entirely possible that an accumulation of minute changes to a system could together give rise to entirely new, emergent properties. There are numerous examples in the field of biology where minute changes in a gene (even the alteration of a single nucleotide) radically alter what the gene does, either completely eliminating its function (null mutations) or producing an entirely new function for the same DNA sequence (neomorphic mutations). In such cases, well-understood molecular events (i.e., DNA mutations) can give rise to emergent properties at the level of whole organisms. Small changes in the timing of key developmental events or in the structural organization of the brain could also produce radical differences in morphology or neurological function between closely related species. In other words, Darwin’s theory asserts that humans are descended from non-human animal species; Darwin’s theory does not say that those non-humans were or could in some way have been “partial” humans.

Embryos and Disorganized Growths
Next, Silver presents what he calls “another scientific challenge for Lee and George”: “If a perfectly normal human embryo is grown in a laboratory incubator, it can develop without any discontinuity into a teratoma.” We (Lee and George) would have to hold, he says, that during its first week in a petri dish, it is a human being. “But no one believes that an embryo-generated teratoma is a human being, even though it can be kept alive as a unique, integrated organism.” And this presents us with the problem: “So when during the continuous life of this organism did the human being suddenly disappear?”

Here Silver’s claims are deeply confused, as standard works of teratology, like the one we cited by O’Rahilly and Mueller, make clear. Even granting — for the sake of argument — that Silver has described the phenomenon accurately, there simply are no valid grounds for regarding — as Silver does — a teratoma as a unitary functioning organism, as opposed to a disorganized growth. Teratomas (unlike embryos) are not individuals of the species in the earliest stage of their development towards organismal maturity. Rather, teratomas are masses of cells, often containing some degree of sub-organismal order or organization (for example, hair, teeth, limb primordia), but lacking organismal wholeness, or indeed any unitary order at the level of a whole organism.

Embryos do not, however, by normal development, turn into teratomas. A “perfectly normal human embryo” cannot “turn into” a teratoma without an intervening event — the death of the embryo — that causes a radical discontinuity between the two. An embryo that dies, leaving physical remains in the form of a teratoma, is a distinct case from an embryo that develops to the fetal stage. Embryos literally turn into fetuses, just as adolescents turn into adults. There is no discontinuity; merely normal development. That is why we cannot say of an embryo and a teratoma what we can say of an embryo, fetus, infant, child, adolescent, and adult, namely, that they are the same entity or being at different developmental stages.

Silver’s argument is an effort to make something of the fact that an event may occur that irreversibly destroys an embryo’s capacity for self-organization and internally-driven growth in the direction of developmental maturity, leaving only a disorganized mass — a teratoma. If this happens, a tumor-like structure lacking the organization and capacity for self-directed development towards maturity as a member of the species is the physical remains of what was, before its death, a complete organism — a living member of the species in the embryonic stage. The teratoma is not continuous with the embryo, since a radical discontinuity — embryonic death — has occurred.

To simply return Silver’s challenge in a somewhat more familiar context; when a patient in a hospital dies, would Silver assert that “a perfectly normal human” develops “without any discontinuity” into a corpse? If a meaningful distinction between a patient and a corpse cannot be drawn (as Silver’s analysis seems to suggest) because the transition between the two states is “continuous,” are we required to view living and dead human bodies as the same, simply because the former seamlessly gives rise to the latter? This is, of course, absurd. Medical science routinely addresses the question of when a patient passes from life to death and medical research into this question continues to define the molecular and cellular correlates of death with greater and greater accuracy. The question of “when during the continuous life of this organism did the human being cease to exist?” can (and is) readily addressed by medical research, and does not present a significant intellectual or scientific challenge to our position.

Spontaneous Embryo Loss — What is Lost?
At the end of Silver’s reply there is a serious mischaracterization or misunderstanding of our position that must be corrected. Silver, and others, had argued that human embryos are not worthy of the full moral respect due to a human being because a high percentage of embryos formed in natural pregnancies fail to implant or spontaneously abort. To this we have at times presented, as a preliminary note to a detailed argument, the following point: “It is worth noting first, as the standard embryology texts point out, that many of these unsuccessful pregnancies are really due to incomplete fertilizations. So in many cases, what is lost is not actually a human embryo” (from Robert George’s Personal Statement in the Report of the President’s Council on Bioethics, on Human Cloning and Human Dignity, p.305).

In both his book and his reply on NRO, Silver misunderstands this to mean that we hold that all defects in fertilization — that is, malfunctions of various sorts in the fertilization process — result in entities that lack the active disposition to, or the developmental trajectory toward, the mature stage of a human being, and so are not actually human embryos. But after making the above point in his personal statement in the Report of the President’s Council on Bioethics on cloning, George went on to say:

“To be a complete human organism (a human being), the entity must have the epigenetic primordia for a functioning brain and nervous system, though a chromosomal defect might only prevent development to maximum functioning (in which case it would be a human being, though handicapped) (emphasis added). If fertilization is not complete, then what is developing is not an organism with the active capacity to develop itself to the mature (even if handicapped) state of a human.”

So our point has always been only that in some instances of “defective fertilizations” what results will lack the program for or developmental trajectory toward the mature stage of a human being, and so is not a human embryo. An embryonic human may certainly have the basic program or disposition orienting it toward the mature stage, but also have defects that prevent the full actualization of that program, as is the case with trisomy 21 and anencephalic infants.

Moreover, in his book Silver presents this merely preliminary note as if it were our main reply to the objection about so-called “embryo-wastage.” Our main replies to that argument, however, have always been that, first, the objection is simply a non sequitur, in fact a form of the naturalistic fallacy — that because something does occur in “nature” with predictable frequency then it must be morally acceptable when deliberately caused by human agency. Second, we have observed that historically, and in some places even today, the infant mortality rate has been very high, and so if this objection were sound, it would show that infanticide in such cultures would be morally acceptable, which (we hope Professor Silver would agree) is absurd.

Put us to the Test
Finally, at both the beginning and the end of his article (and in his book) Professor Silver claims that we have presented a position — that a human embryo is a human being — that is unscientific because it is unfalsifiable (that we cannot conceive of an experiment that would falsify it). We had rebutted objections that monozygotic twinning or formation of chimeras proves that a human individual does not begin at fertilization by pointing out that the conclusion simply does not follow: If monozygotic twinning occurs, evidently a new individual comes to be with the splitting of the original embryo; or, if two embryos combine to form a chimera, evidently either one absorbs the cells of the other or the two cease to be in the formation of a new multi-cellular organism. In his book, Silver labels our reply a “rationalization” and triumphantly claims, “Indeed, they have never described a test that could falsify the theory, which is why this is a matter of faith, not science.”

But again Professor Silver has gone off the rails. The test of whether a group of cells constitutes a single organism is empirically verifiable or falsifiable: that test is whether the cells form a stable body and function as parts of a whole, self-developing, adaptive unit. Again, one need only consult the standard texts. There is no scientific debate about this. It is certainly not a theological dogma or a merely scientific-sounding concept we have concocted. On the contrary, it is the test that has been in general use for years for determining whether an individual (at any developmental stage) remains alive or has died. In the life cycle of embryos that split or combine, there is, indisputably, a whole set of complex, coordinated activities performed by each of these embryos as a whole from day 1 to the day on which twinning or combination occurs (which may be as late as day 9, or, very rarely, even slightly later). This is empirical verification that a developing, single organism exists during that time. So there is a test for verification of the presence or absence of a unitary organism, and we have in our writings applied that test in a straightforward and uncontroversial way to early embryos. Where monozygotic twinning or combination occurs, the embryos prior to those events have clearly passed that test (see Helen Pearson, “Your Destiny, From Day One,” Nature 418 (2002), pp. 14-15). On the other hand, the test also can be failed, and in fact sometime is: In some cases where one thinks there might be a human being at the embryonic stage of development, it turns out that what is present is a teratoma or a complete hydatidiform mole, as evidenced by the lack of self-organization and internally directed growth towards organismal maturity. Thus, the test of whether a unitary organism is present is verifiable or falsifiable. Professor Silver simply ignores the evidence indicating its verification in the coming to be of human embryos at fertilization or monozygotic twinning.

— Patrick Lee is professor of bioethics at the Franciscan University of Steubenville. Robert P. George is McCormick Professor of Jurisprudence and director of the James Madison Program at Princeton University.

Silver's first response

source

October 19, 2006 8:14 AM

Human Issues

To the Editor

I thank my colleagues Patrick Lee and Robert George for the time and effort that they put into reading and critiquing my recently published book, Challenging Nature. Since I present a lengthy discussion of — and challenge to — their previously published views in the first half of my book, I was not surprised that they found much to criticize there. I am disappointed that they had nothing to say about the second half of my book, where I direct my fire at "New Age secularists [who] rail against genetically modified crops." I suspect that many NRO readers will find much to agree with in this portion of my writing (which elicited an enraged review in the American Scientist from the post-modern historian Nathaniel Comfort).

Before I respond to the main points of disagreement, I want readers to know that I wrote about leaders of the Catholic Church in the U.S. with the utmost respect. In describing my meeting with bishops who sit on the Committee on Science and Human Values of the U.S. Conference of Catholic Bishops, I wrote, “At the outset, I was impressed by their genuine inquisitiveness, their desire to understand the most recent advances in science, and their willingness to admit that important questions existed for which they had no answer.” As I have written, the thrust of my challenge to Lee and George was on scientific grounds, not theological ones.

Professors Lee and George think that human embryos are indisputably human beings. Millions of other people brought up in the Western religious tradition hold the same view, but what sets Lee and George apart is their claim that the “scientific facts” alone prove that human embryos are human beings. Lee and George have read and heard challenges to their claim by scientists, writers, theologians, and other academics. Most notable are the able arguments presented by Ron Bailey in a previous NRO debate. But Lee and George haven’t budged, and I doubt there is anything I can say or write that will ever make them budge. My perception of their attitude should make scientists suspicious because it suggests that Lee and George cannot conceive of an empirical experiment (with results that can be objectively verified) that would falsify their claim. If this is true, their claim is not a scientific one. If they’ve got an experiment, I’d like to hear the operational details.

Lee and George base their embryo-is-a-human-being claim mainly on two propositions. One is that a human embryo has an “internal active disposition for self-directed development toward the mature stage of a human.” Since we know that a single cell can separate from a four-cell embryo and develop into a separate human baby (on rare natural occasions), Lee and George would argue that this cell has the “internal active disposition” that makes it a human being. On the other hand, they argue that isolated embryonic stem (ES) cells are not human beings because they do not have this “internal active disposition.” But “internal active disposition” is not a term that has any meaning in the context of cellular or molecular biology. If George and Lee want to claim otherwise, I’d like to know their perception of the molecular attributes that distinguish human-being cells from non-human-being, yet still fully viable and human, cells.

Those of us who have worked only with early-stage mouse embryos (which are essentially identical in size and appearance to human embryos) don’t have the same qualms as colleagues in the human stem-cell field do when it comes to speaking honestly about the relationship of embryos to stem cells. In the summary of a meeting of mouse geneticists published in the journal Science, the reporter wrote, “the participants agreed that it would be most economical to avoid trafficking in live mice and instead decided to maintain the knockouts as embryonic stem (ES) cells: clumps of tissue that can be frozen down and later grown up into full-fledged mice” (Science 312: 1862-1866; June 30, 2006). Furthermore, as I wrote in my book, human ES cells have already been differentiated into placenta. This means that, in theory, the requirement for a second source of cells to reconstitute an embryo may be nullified, and ES cells — all by their lonesome — could develop into a fetus and human baby. This discussion was conveniently left out of Lee and George’s review. But, if theory becomes practice, and ES cells can be grown directly into a fetus, at what point during continuous development from a bunch of cells to a fetus does a human being instantly appear? Tell me what the molecular correlates are for such an event.

The second proposition that Lee and George use in their appeal to science has been simply stated on many occasions by Professor George: “a thing either is or is not a human being.” Lee and George provide several arguments in support of this proposition. One is that it is simply commonsensical to most people. I have no doubt that this observation is correct, but as many examples from science demonstrate, common sense is no predictor of truth. Furthermore, it is not surprising that so many philosophers have also held this position. Two millennia ago, in the absence of modern scientific knowledge and biomedical technology, Aristotle would certainly have convinced me of its veracity. Modern psychologists have evidence that normal human brains are hard-wired to categorize everything into distinct classes (including human beings and non-human beings).

Scientific knowledge challenges this instinct on many occasions. The most serious challenge, of course, came from Darwin, whose theory of natural selection suggests that in the evolution of pre-human apes into human beings, there was no first human being. Instead, there appears to have been a continuum of evolutionary forms in a process during which no child was significantly different from its parents. The scientific implication is that some “things” might be in-between non-human and human. An alternative suggested by Pope John Paul II is that while physical evolution was continuous, spiritual evolution was not. The pope specifically ruled out an appeal to science when he described this idea.

And here’s another scientific challenge for Lee and George. If a perfectly normal human embryo is grown in a laboratory incubator, it can develop without any discontinuity into a teratoma. According to Lee and George, during the first week in the petri dish, the embryo is a human being. But no one believes that an embryo-generated teratoma is a human being, even though it can be kept alive as a unique, integrated organism, and even though it is certainly not part of any other organism. So when during the continuous life of this organism did the human being suddenly disappear? Again, what molecular or cellular correlates would you expect to see at the moment of passing?

I would like to end this response with the telling of an episode that occurred while I was hiking through the jungle with my two sons and my wife in West Africa last summer. At what one point, my son walked past what looked like an eight-foot long yellow-greenish tree branch that had fallen onto the path. But the “branch” suddenly became animated and slithered off into the undergrowth. It was a snake of the Green Mamba species, our guide told us. “Is it dangerous?,” I asked. “It depends,” he said. “If the snake is able to deposit part of its spirit into the person, it will consume the person’s spirit and death will surely follow. However, if the snake’s spirit doesn’t make it across in the bite, the person will suffer no permanent harm.”

This was not a parable, it was cultural knowledge — an attempt by uneducated people to make sense out of the otherwise unexplainable observation that some people died while others recovered completely after a Green Mamba bite. I didn’t believe it, but I couldn’t disprove it. It failed to provide any predictions — it was not falsifiable and, therefore, it was not scientific.

Professor Lee and George have argued that embryos with wrong numbers of chromosomes are not really embryos because they do not have the capacity to develop into mature human beings. This is true for 90 percent of human embryos which have an extra copy of chromosome 21 (in particular), but ten percent do develop into human beings born with Down Syndrome. In these cases, according to Lee and George, we can tell in retrospect that the embryo must have been a human being as well.

Lee M. Silver
Princeton University
Princeton, N.J.

Editor's note: Come back to NRO tomorrow to Robert P. George and Patrick Lee's reply to Lee Silver's letter.

Fundamentalists? We?

source

October 3, 2006 12:00 AM

Fundamentalists? We?
Bad science, worse philosophy, and McCarthyite tactics in the human-embyro debate.

By Patrick Lee & Robert P. George

We have in many places argued for the humanity and fundamental dignity of human beings in the embryonic stage of development and all later stages. In defending embryonic human life, we have pointed out that every human adult was once an embryo, just as he or she was once an adolescent, and before that a child, and before that an infant, and before that a fetus. This is not a religious claim or a piece of metaphysical speculation. It is an empirical fact. The complete human organism — the whole living member of the species Homo sapiens — that is, for example, you the reader, is the same human individual that at an earlier point in his or her life was an adolescent, a child, an infant, a fetus, an embryo. From the embryonic stage forward, all you needed for your survival and continued growth towards adulthood along the continuum of human development was a suitable environment, adequate nutrition, and freedom from grave disease.

In short, we have argued — though it is fairer to say that we have pointed out, since the scientific facts are not in dispute — that human embryos do not differ in kind from (other) human beings; rather, they differ from other human beings merely in respect of their stage of development. Embryos, fetuses, infants, adolescents, and adults are not different kinds of being — the way a human, an elk, a spider, a cucumber, and an amoeba are different kinds of being. Embryos, fetuses, infants, adolescents, and adults are the same kind of being at different developmental stages.

Still, Lee Silver in “The Biotechnology Culture Clash,” published in Science and Theology News (July 18, 2006), and more fully in a new book entitled Challenging Nature, insists that our views about the humanity and dignity of the human embryo are grounded in religious beliefs. He accuses us of concocting a scientific sounding case against embryo-destructive research in an effort to impose our religious beliefs on others while evading the constitutional prohibition of laws respecting an establishment of religion.

So Now We’re Fundamentalist Theologians?
Silver says that the claim that human embryos are human beings at an early stage of development is “hidden theology.” This could mean two different things. First, as this claim is presented in the book, Silver asserts that we actually hold our position on the status of the human embryo on theological grounds. We are, he suggests, hiding this fact, manufacturing arguments that sound scientific, but are in reality merely a cover for our real, theological, and indeed, “fundamentalist” grounds.

To describe such a claim as an ad hominem argument is to exaggerate its standing. It is nothing more than ad hominem abuse. Silver knows that we are Catholics, and so he uses that fact to suggest that our real ground for believing that human embryos are human beings is Catholic doctrine. But here he has things exactly backwards. Our ground for believing that human embryos are human beings is the indisputable scientific fact that each human embryo is a complex, living, individual member of the human species. Although our claim does not rest on the authority of the Catholic Church, or any other religious body or tradition, we find the Church’s teaching against human embryo-killing credible precisely because it — unlike Silver’s contrary teaching — is in line with the embryological facts. If “fundamentalism” consists in obstinately clinging to a moral, religious, or political view in defiance of empirically demonstrable findings of science that falsify its premises, we are not the fundamentalists in this debate. It is Lee Silver himself who has fallen into a form of fundamentalism.

The biological fact that human embryos are human beings in the earliest stages of their natural development is, to say the least, inconvenient for Professor Silver. So he commits the very offense of which he accuses us and others who oppose his agenda. He hides his ideology under a veneer of science. But the veneer is easily pulled off and the truth exposed. Just examine any of the major embryology texts now in use in American medicine. What you will find is the teaching that a new human individual exists from the earliest embryonic stage forward. That individual is a complete, though, of course, developmentally immature, member of the human species, whose life — whether it lasts for nine minutes, nine days, nine years, or nine decades — is a human life.

The second thing Silver could mean by his “hidden theology” allegation is that our argument depends on an implicit theological premise, whether or not we are aware of it. In the bulk of his analysis, this seems to be Silver’s claim against us. It is a bold charge, and to support it, Silver would have to show that at least one of the premises of our argument is such that anyone asserting that premise must depend on religious faith for his presumed awareness of it. For example, if one could show that a person could advance a particular argument only if he presupposed that God is three persons in one being, or that God became man — propositions about the inner life of God or about his free choices, and so in principle not provable by reason unaided by faith — then it would follow that the argument depended on a theological premise. So, what religious dogma does Professor Silver find lurking in our premises? What is the unstated religiously dogmatic assumption of our argument? At what point are we “stealthy servants of God” (as Silver characterizes us on p. 116)? The hidden assumption, according to Silver, is the following: that a thing either is or is not a human being (though, curiously, on p. 83 Silver actually quotes Robert George openly asserting this supposedly “hidden” assumption).

According to Silver, “This assumption comes from an interpretation of Genesis by certain religious groups that strictly follow the Bible. Genesis 1:27 says, ‘God created man in His own image.’ And that is interpreted by some as meaning that God created man instantaneously. There can be no such thing as gradual creation because then you have partial man, and man would not be in the image of God. There is no such thing as a partial God. God is absolute.”

This is risible. First, the supposed theological argument grounding the key assumption does not even make sense. Formally, the argument would be: “God is not partial; humans are like God; therefore no humans are partial.” But by this argument pattern one could also conclude that humans must be uncreated, perfect, infinite, and eternal. Is it really likely that such nonsense would be the hidden inference bolstering our assertions?

Second, the idea that a thing either is or is not a human being is not a proposition about the inner life of God or about God’s free choices — propositions beyond the reach of reason unaided by faith. Why assume that a very straightforward proposition about human individuals is something knowable only by religious faith?

Third, many philosophers, both ancient and contemporary, some religious and some not religious (e.g., Aristotle, David Wiggins, Roderick Chisholm, Peter Van Inwagen, E. J. Lowe, and many others) have ably defended this proposition on philosophical grounds.

Fourth, this proposition is part of common sense (a fact that doesn’t by itself prove it, but does provide support for it). Most people believe that they persist through time, and so, by implication, that there is a profound difference between their becoming this or that (say, tall or tan), and their coming to be at all. If I am the same concrete being yesterday and today, then I exist completely at each time that I exist (though I constantly change by acquiring new qualities, changing in quantity, and so on). And if I exist wholly at each time that I exist, it follows that I came to be, that is, began to exist, at once and not gradually. Otherwise, during my coming to be I would exist partially, not wholly. Thus, as common sense would have it: there are degrees in various qualities and quantities, such as colors or sizes, but there are no degrees about whether an individual exists or not; either he exists (however developmentally immature or tiny) or he does not.

Finally, there are strong philosophical arguments in favor of this common sense view. The denial of it logically entails what is sometimes called “perdurantism,” or “the temporal parts view” — namely, that a person is only a series of events or experiences spread out in time, like a baseball game or a song. On this view, the temporal extent of a person is part of what he is, and at any one time he exists only partially, not fully. As a consequence, according to this view, “I today” and “I yesterday” refer not to the same concrete individual, but to different temporal phases of the whole series temporally extended.

Were You You Yesterday?
This view has several grave problems, two of which we will mention here. The first difficulty is that, according to this view, a human being (or any ultimate subject of existence) is the sum of time-slices suitably connected (say, by biological or psychological continuity). But what is a time-slice, and, how could time-slices give rise to a human organism’s (or any organism’s) extension through time? If the time-slice itself does not have temporal extent, then the addition of any number of time-slices to each other will not give rise to a temporally extended series — just as the addition of any number of unextended points will not produce an extended line. On the other hand, if the time-slice of a human being does have temporal extent, then no explanatory gain has been achieved by denying a persisting human being, since one will then (by necessity) have admitted that an individual as a whole can persist through at least some extent of time. But if one must admit persistence through time at one level, why not admit it at the level that common sense and explanatory practice seem to demand — that is, the lifetime of a human individual who persists through time?

A second problem with the temporal-parts view is that, in effect, it actually implies the complete denial of change. On the temporal-parts position, a particular object, such as a human being, is not wholly present at any given time. Rather, just as an object has spatial parts, so that at small portions of space only part of it is present, so (on the temporal parts view) each object has temporal parts. An object, for example an apple, has a part that is present at one time, say on Monday, and another part that is present at another time, say on Tuesday. The apple is composed of different temporal parts or stages. Thus, the apple is green at one temporal stage (Monday) and red at another temporal stage (Tuesday). But on this view it follows that in the strict sense there simply is no change. A flagpole that is green at one spatial part and red at another part does not involve any change; but by the same token, an apple that is green at one temporal part and red at another temporal part involves no change either. For real change to occur, the same subject must first be characterized in one way and then in another way.

But it is obvious that change does occur. Consequently, an object (a substance) is not just a series of events, but exists wholly at each time that it exists. When it comes to be, it must come to be at once (though, of course, once it comes into being it may, depending on the kind of substance it is, grow in size and proceed through various developmental phases towards maturity). Changes can precede this substantial coming to be, changes that dispose the future constituents of the substance more and more to that substantial change. For example, fertilization is a gradual process that results in the coming to be of a new organism. But the organism itself does not exist until the process is completed. Prior to the completion of this process it is not correct to say that the new organism partially exists. (It does not “partially exist” during the process.) When it comes into existence, it comes into existence as a whole organism. But the substantial change itself — the actual change from not existing to existing — must be at once.

Thus, both common sense and philosophical arguments provide strong support for the proposition that human beings cannot partially exist, that a human being either is or is not. It is ridiculous to claim — as Silver does — that this proposition is a hidden theological assumption. (Indeed, it would be ridiculous to classify it as a theological belief, as opposed to a philosophical one, even if it could be shown to be incorrect.)

Part and Whole: A Basic Distinction
In addition to claiming that our position is based on “hidden theology,” Silver presents an argument in the form of a reductio ad absurdum for his denial that early stage human embryos are embryonic human beings. He says: “Embryonic stem cells can develop into an actual person. So, based on the definition of the U.S. National Academy of Sciences, embryonic stem cells are equivalent to embryos. Yet based on the molecular signals that you give the cells, the cells can change from embryonic to nonembryonic and back to embryonic. You can do this easily.” But the first sentence just quoted from Silver is simply false. Embryonic stem cells are functionally parts of a complete organism; they are not themselves complete human organisms. (When separated from the whole human organism, they are no longer functioning parts of that organism; they become mere cells — fundamentally different from whole, though immature, members of the human species.)

A human embryo — precisely because it is a complete member of the human species — can develop towards maturity, given a suitable environment and adequate nutrition. The embryo possesses the genetic and epigenetic primordia and the active disposition for self-directed growth towards the next more-mature stage. But this is not true of a stem cell or even of a mass of stem cells. Like somatic cells that might be used in cloning, they possess merely a passive capacity to be subjected to various techniques of asexual reproduction and so become parts of a new human organism.

Silver bases his claim that “embryonic stem cells are equivalent to embryos” on the fact that mouse embryos can be generated from embryonic mouse stem cells and have all of their genetic makeup, and cell lineage, derived from those initial stem cells. A tetraploid embryo-like entity known, though controversially, as a tetraploid “embryo” (“tetraploid” meaning that the entity has four sets of chromosomes rather than the normal two sets) is developmentally defective, so it can give rise only to trophoblastic cells (precursors of the placenta and associated tissues) and not to the cells of the “embryo proper.” When combined with mouse ES cells (ones that have a normal number of chromosomes), these can produce a chimeric mouse in which the cell lineage of its placenta and associated tissues is derived from the tetraploid entity (or “embryo”), and the cell lineage of the mature embryo (the “embryo proper”) is derived from the ES cells. From this, Silver infers that ES cells can by themselves develop into the mature stage of the animal (see his book, p. 140) — “by themselves” in the sense that the DNA in all of the mature embryo’s cells is identical to that in the ES cells.

Since it is often argued that human embryos are human beings because they can “by themselves” develop into mature humans, it follows — on Silver’s argument — that embryos and stem cells are (ontologically and morally) equivalent. But since it is absurd to think that ES cells are human beings, it also is absurd (Silver’s argument continues) to think human embryos are human beings.

This argument is a descendent of an earlier, similar argument that embryos are morally equivalent to somatic cells (such as skin cells) because somatic cells can produce mature human beings by way of cloning via somatic cell nuclear transfer (SCNT). In SCNT the nucleus of a somatic cell is inserted into an enucleated ovum and they are caused to fuse by an electrical stimulus, the result (if all goes as planned) being a cloned embryo. It was argued (by Ronald Bailey, Peter Singer, and others) that since somatic cells are converted into embryos, and these grow into mature members of the relevant species, human embryos have no more exalted a status than ordinary somatic cells, such as skin cells. Some critics of this argument replied that the somatic cells cannot by themselves develop into mature humans, which is certainly true. The important point, though, is that the SCNT process makes use of the somatic cells to create entities of a different nature — using parts of human organisms (somatic cells) to make new complete human organisms at the embryonic stage of development.

Thus, in the context of SCNT cloning, somatic cells are analogous to sperm and oocytes (parts of whole organisms) rather than to embryos (which indeed are whole organisms). But Silver thinks production of a mature mouse by tetraploid complementation answers that reply: In this process, the more mature organism is derived directly from the ES cells, so the ES cells do (according to Silver) in some sense by themselves become whole embryos. He thinks this process shows that, just like embryos, ES cells also can develop into mature members of their species if they are just given a suitable environment.

Confusion over Tetraploid Complementation
However, this fundamentally misinterprets the results of tetraploid complementation. In addition, it repeats the mistake in the earlier argument. Tetraploid complementation does not show that the “entire embryo” can be derived from ES cells. The embryo (or embryo-like entity) generated from tetraploid complementation is a chimera, with parts derived from the original embryo that was induced to become tetraploid and parts derived from the ES cells. The placenta and other organs generated from the tetraploid cells are parts of the embryo. They are bodily organs that function only during embryonic life, but they are bodily organs none the less — analogous to baby teeth, which also function only during a portion of the animal-organism’s life cycle. The placenta is a vital organ of the embryo, and it is not directly made by the ES cells.

Moreover, in tetraploid complementation, the ES cells do not by themselves generate a mouse since they do not by internal self-direction develop into a mouse. So the ES cells are not mouse embryos or their equivalent, and never were. True, the mature mouse’s cell lineage is completely derived from the ES cells, but an analogous point is also true in SCNT cloning — the DNA of the mature mouse or sheep or other animal is identical to that of the donor somatic cell (although the cytoplasm from the enucleated ovum also has a determinative effect). The central point is that, just as in SCNT cloning, so here: the manipulation (in this case, the combining of the ES cells with the tetraploid entity or “embryo”) generates a new type of biological entity. This is demonstrated by the profoundly new type of behavior observed in the entity produced by the process or processes of tetraploid complementation. The manipulations involved do much more than merely release an inner capacity of the stem cells. The combining of the stem cells with the tetraploid embryo does not merely place these cells in an environment hospitable to the process of organismal development. Rather, it transforms them from functional parts to components of an actively developing whole organism. Or, more precisely expressed: the combining of the stem cells with the cells of the tetraploid embryo generates a new organism, an organism that is not a stem cell.

The tetraploid complementation procedure is simply a type of cloning. In the most common form of cloning — SCNT — a new organism is generated; it comes into being as an embryo which immediately begins actively developing itself into the more mature form of the whole organism it now is. Completely analogous to what occurs in tetraploid complementation, the new embryo in SCNT cloning has the same genetic code as the somatic cell. The combining of stem cells with a tetraploid embryo does to the mouse stem cells what fusing an enucleated ovum does to a somatic cell in SCNT, the procedure that generated Dolly the sheep and many other cloned mammals — namely, it produces a distinct, whole organism.

So a stem cell does not “become” an embryo (the way an embryo truly does become a fetus, an infant, a child, an adolescent, and an adult). Rather, many stem cells are used in a cloning process that, if successful, results in the production of a new and distinct organism. The proof that this results in an entirely new and distinct organism is that it has a radically different trajectory of growth.

Thus stem cells are not equivalent to embryos. They lack the defining feature of embryos, namely, the internal active disposition to develop themselves to the mature stage of the organism of the relevant species. If placed within an environment suitable for the development of human embryos, human stem cells do not do what embryos do. (The crucial fact that by themselves — that is, when not introduced into a pre-existing, albeit defective, tetraploid embryo — ES cells produce only disorganized masses of tissue, either embryoid bodies or teratomas, is conveniently ignored by Silver.) Only if human stem cells are joined with other factors so as to generate a distinct and whole organism in SCNT, or in the combining of stem cells with tetraploid embryo-like entities, does an embryo come to be.

Several passages in Silver’s book indicate that he regularly fails to see the significance of the distinction between a whole organism, on the one hand, and a tissue or part of an organism, on the other hand. Thus, he believes our argument is easily refuted by pointing out that a single human skin cell or a teratoma has the same genetic code as other (whole) members of the relevant species. But our argument has never been simply that human embryos are human beings because they have the full genetic code. Rather, we have always argued that their full genetic code, plus (and more importantly) their internal active disposition for self-directed development toward the mature stage of a human, show that they are what the standard embryology texts say they are, namely, distinct and whole (though immature) individuals of the human species.

Stem Cells Are Human Too?
Having assumed erroneously that one can convert a human stem cell into a human embryo and back again quite easily, Silver then says:

So then you can ask, ‘How many human beings are there in a dish of embryonic stem cells?’ If there are a million cells in the dish, and you separate all the cells, then you have a million human beings. But you can then put them back together to form a single organism. What happened to the 999,999 human beings? Robert George would say they all died.

He supposes that this is a decisive argument, but in truth it is a failure. The prospect of actually creating and then killing almost a million human embryos merely by separating cells is a figment of Silver’s imagination.

To the question, “How many human beings are there in a dish of embryonic stem cells” the answer is: none, for stem cells, like other somatic cells, are not human beings.

When Silver asserts next, “If there are a million cells in the dish, and you separate all the cells, then you have a million human beings,” this is simply incorrect. You must do much more than merely separate stem cells in order to generate embryos. Separating them will merely spread them apart. Like a somatic cell, a stem cell must be fused with something else that will transform it from a part into a whole in order to produce an embryo.

But suppose that a lab were successfully to produce a million clones from human embryonic stem cells. How many nascent human beings would you have? The answer is: a million. Of course, no one, to date, has managed to demonstrate success in cloning even a single human embryo, using the methods that succeeded (with much labor) in other mammals. The scenario Silver proposes (which involves producing a million clones in a short time) is not possible today, and perhaps will never be possible. It certainly cannot be “easily done.” Moreover, if tetraploid complementation were successfully performed on human stem cells, only one human organism would be generated from several stem cells, not one embryo per stem cell.

Conspiracy Theories
Silver’s errors in dealing with embryological science are nothing by comparison to the extraordinary charges he makes when he turns his attention to political matters. Silver claims to have uncovered an extremist right-wing conspiracy among academics and politicians. He asserts that there is a highly organized effort by “fundamentalists” to gain control over portions of our government and schools, in order to impose a narrow religion on all.

For example, Nigel Cameron is a Christian who claims to present pro-life arguments that can appeal to all people, whether religious or not. Silver first exposes Cameron’s Christianity, quoting from an article Cameron wrote extolling the merits of a theological understanding of medicine. Silver then says that Cameron is using “code words” to convey religious messages to Christians, codes that are not recognized as religious by unsuspecting seculars. He adds: “Cameron’s tactics are taken from the playbook of clever fundamentalists who feel impelled to instill their beliefs as soon as possible, not just in their own children, but in everyone else’s children as well” (p. 102). Again, Silver refers to pro-life intellectuals, including Robert George, as advocates of an ideology who put forth “scientific-sounding arguments to advance their case” (p. 112). He warns of the craftiness of fundamentalists who might lure scientists into arguing with each other: “And so fundamentalists often succeed in transforming a religious debate into a dispute among scientists”(p. 118). One must especially be careful to resist their secular-sounding slogans, which (again) are codes that usually only fundamentalists understand the true meaning of: “Theological terms and ideas are translated into secular-sounding code words and phrases. Sanctity is converted into dignity, the soul becomes life, and the biblical version of morality is presented as a secular bioethics” (p. 118).

Here Silver veers from bad science and even worse philosophy into sheer paranoia. He seems incapable of understanding that the issues about which he is writing are complex and difficult matters on which reasonable people can reasonably disagree. Instead, he assumes that anyone who does not share his opinions is a “fundamentalist” (or dupe of the “fundamentalists”) and is part of a sinister conspiracy to impose a theocracy.

Speaking of Robert George, Silver writes: “Almost certainly, George knows that his so-called ‘scientific evidence’ finds no acceptance among any secular, molecular, or modern developmental biology professor at any major research university” (p. 108). Yet a glance at any of the standard embryology textbooks rebuts this claim. See, for example, Bruce Carlson, Human Embryology and Developmental Biology (St. Louis: C.V. Mosby, 2004); William J. Larsen, Human Embryology, 3rd ed. (2001); Keith Moore and T.V.N. Persaud, The Developing Human, Clinically Oriented Embryology, 7th ed. (2003); and Ronan O’Rahilly and Fabiola Mueller, Human Embryology and Teratology, 3rd edition (2000).)

According to Silver, one should also be wary of conservative think tanks, since they are actually hot-beds of conspiracy: “Evangelical think tanks and lobbying groups proliferate with innocent-sounding names like the Center for Bioethics and Human Dignity, which is directed by the fundamentalist Nigel Cameron” (p. 118). (It would probably be useless to point out to Silver that Dr. Cameron is no fundamentalist, and does not direct the center in question.) Indeed, according to Silver, “The subterfuge is more subtle, but no less potent, in the academic realm. One particular secular-sounding word — natural — frequently infuses the arguments of diverse opponents of biotechnology” (p. 119). Here the entire philosophical tradition of “natural law” reasoning on ethics, whose roots predate Christianity by at least three centuries in the works of Aristotle, becomes a mere façade for the “fundamentalist” conspiracy.

In the end, Silver’s manner of arguing degenerates into a form of McCarthyism. He relentlessly uncovers the Christianity of various lawyers, political figures, writers, physicians, and academics, describing them as “stealthy servants of God.” On his list of Christian “fundamentalists” and individuals collaborating with them (some of whom are Jews) to impose Christian theological dogmas on the entire nation are: Johns Hopkins Medical School surgeon and President’s Council on Bioethics member Benjamin Carson, Oxford University legal philosopher John Finnis, Harvard Law School professor Mary Ann Glendon, Stanford University consulting professor and President’s Council on Bioethics member William Hurlbut, former President’s Council on Bioethics executive director Yuval Levin, and Johns Hopkins Medical School psychiatry professor and President’s Council on Bioethics member Paul McHugh. We wouldn’t be surprised to learn that Silver has a list of 205 card-carrying fundamentalists and their fellow-travelers. Perhaps he will ask others, “Are you now, or have you ever been, a member of the Christian religion?”

Losing It Completely
Going from the ridiculous to the bizarre, Silver extends his conspiracy theory to his fellow scientists. As we have observed, he insists that human embryonic stem cells are the equivalent of embryos because they are (he supposes) capable of developing into human babies. Why hasn’t the public been made aware of this remarkable “fact”? Because, he says, scientists have deliberately kept the public in ignorance: “stem cell scientists know this fact, but they have succeeded in hiding it from the public at-large.” Oh, those stealthy servants of science! There they are, in full knowledge of a key fact about embryonic stem cells, but deliberately covering it up lest the unenlightened masses become alarmed and start slapping new restrictions on legitimate research.

One can be forgiven for savoring the irony here. If, as Silver claims, stem cell scientists have deliberately concealed what they believe to be the truth about embryonic stem cells — namely, that they are equivalent to embryos — then he has established that embryonic stem cell scientists cannot be trusted to be honest with their fellow citizens about facts that might be politically inconvenient. If, on the other hand, what Silver alleges about his fellow scientists is false, then his own credibility collapses.

Silver’s real problem is that the proposition that the human embryo from the zygote stage forward is a distinct, complete (though immature) human being, identical with the child or adolescent which later everyone will recognize as possessing basic rights — that this proposition is fully supported by arguments open to people of all faiths, or of no faith at all. He resorts to name calling (“fundamentalists”), ad hominem abuse, and McCarthyite tactics to distract attention from the scientific facts and their logical implications. Those implications are inescapable once we accept the moral principle that all human beings are entitled to equal concern and respect.

Contrary to what Silver imagines, the great threat to embryo-destructive research is not that “fundamentalists” will take control of the United States government; it is that citizens of every faith, or of none at all, will acquaint themselves with what modern embryology has revealed about human embryogenesis and development.

— Patrick Lee is professor of bioethics at the Franciscan University of Steubenville. . Robert P. George is McCormick Professor of Jurisprudence and director of the James Madison Program at Princeton University.