Ethics of Embryonic Stem Cells
http://www.100md.com
《新英格兰医药杂志》
To the Editor: In his Perspective article on "embryo ethics," Sandel (July 15 issue)1 argues that "although every oak tree was once an acorn, it does not follow that acorns are oak trees, or that I should treat the loss of an acorn . . . as the same kind of loss as the death of an oak tree. . . . Despite their developmental continuity, acorns and oak trees are different kinds of things." Sandel is right to imply that the debate over the justice of destroying human embryos in biomedical research turns on the question of whether embryos are different in kind from human beings. People do ascribe dignity and intrinsic worth to human beings precisely because of the kind of entity they are, not because of accidental qualities — that is, qualities that some human beings possess and others do not or that some possess to a higher degree than others. That is why we consider even severely retarded persons or persons in a long-term coma to be equal in dignity and fundamental rights to other persons. We would never countenance killing them in order to benefit others by, for example, harvesting their vital organs.
The flaw in Sandel's argument is that human embryos differ from other human beings not in the kind of entity they are, but in their stage of development. A human embryo is a human being in the embryonic stage, just as an infant or an adolescent is a human being in the infant or adolescent stage. In fact, every adult was once an embryo, just as he or she was once an adolescent, a child, an infant, and a fetus.
What about Sandel's analogy? It collapses the moment one considers why we value mature oak trees and feel a sense of loss at their destruction. Contrast that with why we value human beings. We value oak trees because of certain accidental qualities, such as their magnificence (a certain grandeur that has taken perhaps several decades to achieve). If oak trees were valuable by virtue of the kind of entity they are, then it would follow that it is just as unfortunate to lose an acorn as it is to lose an oak tree. But oak trees and acorns are not equally valuable, because the basis for our valuing the trees is not the kind of entity they are but rather those accidental characteristics (e.g., the magnificence that comes only with maturity) by which they differ from acorns and members of the species at early developmental stages, such as saplings.
People typically regard oak saplings as no more valuable than acorns. Forest managers regularly destroy saplings to maintain the health of mature trees, and no one regrets their loss or gives the matter a moment's thought. If we valued oaks (as we value humans) by virtue of the kind of entity they are and not by virtue of accidental qualities, we would regard their deaths in the way we regard the deaths of children — the precise equivalent to saplings in Sandel's analogy. No decent person believes that children — even severely retarded children — may legitimately be killed in order to provide vital organs for adults. Yet anyone who credits Sandel's analogy will have abandoned the intelligible basis of this belief.
Robert P. George, J.D., D.Phil.
Princeton University
Princeton, NJ 08540
Patrick Lee, Ph.D.
Franciscan University of Steubenville
Steubenville, OH 43953
References
Sandel MJ. Embryo ethics -- the moral logic of stem-cell research. N Engl J Med 2004;351:207-209.
To the Editor: Sandel has pointed out that there is no defining moment in the development of a human being from the stage of a zygote to birth. He proposes that "the fact that every person began life as an embryo does not prove that embryos are persons." And yet, what is an embryo if not a human at an early stage of life? Sandel states that "human life develops by degrees." What degrees? What marks the transition from one degree to another? If an embryo is not a person, when does a person become a person? Rather than being logically rigorous in his arguments, Sandel relies on rationalization. But please do not confuse rationalization with ratio (Latin for reason). Chief among these rationalizations is his contention that if we allow a practice to occur, it must not be immoral — if it was immoral, we would never allow it. The folly of such circular reasoning should be obvious to even the most committed proponents of this potentially promising research.
G. Neal Kay, M.D.
University of Alabama at Birmingham
Birmingham, AL 35294
To the Editor: Sandel's use of the analogy of acorns and sequoias suggests that he places human embryonic life on a quantitative scale that includes plants and animals. It is obvious to everyone that every human adult was once an embryo and that an embryo that is destroyed does not become an adult, although it had the potential to do so. So why do we think that an embryo deserves only a "certain respect," and why don't we treat it with even greater respect than we treat an adult, because of its exquisite vulnerability and its unimaginable potential to live into adulthood and enhance even our own lives? Maybe it is a lack of imagination on the part of scientists in general, or maybe it is the tendency that society has to undervalue and exploit its vulnerable and dependent members. Clinicians, however, surely must see the paradox of sacrificing a new person's life in its simplest expression in an attempt to cure disease.
Patrick M. Pullicino, M.D.
New Jersey Medical School
Newark, NJ 07103
pullic@umdnj.edu
To the Editor: Sandel presents a clear understanding of the issues regarding stem-cell research. However, the analogy between acorns and oak trees as "different kinds of things" and human embryos and human beings as different kinds of things fails as an argument. Do we really wish to elevate sentience as the final benchmark? And when do experience and consciousness "make higher claims still"? Where does this leave the severely demented person with Alzheimer's disease or the severely handicapped child? At what point do we say human life developing "by degrees" can be dubbed fully human, with all the inalienable rights thereto?
What need is there to treat an embryo with respect if it is different in kind and less than a "full human being"? Does not the embryo possess all the genetic stuff of full humanness?
Yes, natural procreation does entail the loss of some embryos for every successful birth, but this is natural, whereas the intent with stem-cell research is purposeful and humanly directed, and therein lies the rub.
Ross E. Anderson, M.D.
Allina Medical Clinic–Shoreview
Shoreview, MN 55126
To the Editor: Sandel provides a thoughtful philosophical overview of the current policy dilemma concerning embryo ethics. The most helpful approach, however, may involve addressing the psychology underlying the stem-cell controversy — most important, the perennial fear of new technology.
Seen in this light, embryo ethics is a novel permutation of a very old motif. Anesthesia was once decried as immoral because it contravened God's will for women to suffer during labor, and in vitro fertilization was initially assailed as a dehumanizing slippery slope.
The fundamental fears underlying such claims may be resolved without directly affirming or denying the values they represent. In fact, that is how responsible physicians attend to the concerns of patients whose private values may differ from their own. Opponents of stem-cell research seem to sense, from precedent, that it is inevitable. By listening tolerantly to all angles of input, we ease the anxieties aroused by such a sense of inevitability. And by restraining the impulse to make value judgments, we keep each new wave of technology tension in proper historical perspective.
Christian P. Erickson, M.D.
Loma Linda University Medical Center
Redlands, CA 92373
christianerickson@alumni.duke.edu
To the Editor: In his Perspective article on research involving embryonic stem cells, the ethical distinction that McHugh (July 15 issue)1 makes between a human zygote and "clonote" is useful only if an embryonic clone is fated to die before birth from severe epigenetic problems. If these problems are eventually overcome, a zygote produced by in vitro fertilization and a clonote produced by somatic-cell nuclear transfer should be treated identically. The purpose of their creation would be immaterial. Without uterine implantation at an early embryonic stage, neither could develop into a viable fetus, making it ethically justifiable to extract stem cells from either.
The same moral logic also compels the granting of special status to an implanted human embryo, whether it originates as a zygote or as a clonote. Furthermore, any child born should be afforded equal rights, regardless of its reproductive origins.
However, even if the epigenetic problems of reproductive cloning were resolved, substantial psychological and social risks would remain.2 These alone would make it unethical to use reproductive cloning to create a genetic replica of another human being.
Stephen E. Levick, M.D.
University of Pennsylvania School of Medicine
Philadelphia, PA 19104
s.levick@worldnet.att.net
References
McHugh PR. Zygote and "clonote" -- the ethical use of embryonic stem cells. N Engl J Med 2004;351:209-211.
Levick SE. Clone being: exploring the psychological and social dimensions. Lanham: Md.: Rowman & Littlefield, 2004.
Dr. Sandel replies: Erickson speculates that some people oppose stem-cell research because they fear new technology. Whether or not this is true, the principled arguments they offer are worth taking seriously. The controversy cannot be resolved, as Erickson suggests, "by restraining the impulse to make value judgments." As the other letters reflect, the debate over embryonic stem-cell research cannot be decided without addressing the moral status of the embryo.
Anderson argues that the embryo possesses "all the genetic stuff of full humanness." But the same could be said of a human skin cell. And yet no one would argue that a skin cell is a person or that destroying it is tantamount to murder. Pullicino writes that "every human adult was once an embryo" and that "an embryo that is destroyed does not become an adult, although it had the potential to do so." But it is also true that every human being originated with an egg and a sperm, and that an egg or a sperm that is destroyed does not realize its potential to become a human being. Would Pullicino therefore attribute personhood to eggs and sperm? He might reply that most eggs and sperm do not develop into human beings. But neither do most fertilized ova.
Kay points out, rightly, that allowing a practice to occur does not make it moral. But I did not defend embryonic stem-cell research on the grounds that it occurs. Perhaps he is referring to my observation that U.S. fertility clinics are permitted to create and discard excess embryos. But the point of the analogy to in vitro fertilization was simply to show that those who would ban embryonic stem-cell research should also seek to ban all infertility treatments that create and destroy excess embryos.
George and Lee write that the developmental continuity between blastocysts and human beings proves that embryos and persons are the same "kind of entity" and therefore are morally equivalent. My article sought to refute this argument by analogy: all oak trees were once acorns, but this does not prove that acorns are oaks or that the loss of an acorn is as tragic as the destruction of an oak. George and Lee reply by insisting that acorns and oaks are the same kind of entity; we value the oak tree more only because it happens to be magnificent, which is an "accidental," not an essential, characteristic. Respect for human life, they argue, should be irrespective of such accidental traits as magnificence, maturity, or developmental stage. Even accepting their quaint metaphysical distinction between essential and accidental traits, what makes them so confident about which is which? Isn't it in the nature of an oak tree to be magnificent? If so, we should regard the acorn as a potential oak. And isn't the fact that we develop within and are born of a biologic mother an essential characteristic of human beings? If so, we should regard the preimplantation embryo not as a person but as a potential human life.
Michael J. Sandel, D.Phil.
Harvard University
Cambridge, MA 02138
Dr. McHugh replies: Levick and I agree on much, such as opposing reproductive cloning. But I do think the distinction in nature between in vitro fertilization and somatic-cell nuclear transfer has ethical weight for the reasons I mentioned. It is true, at the moment, that only when it is implanted in a uterus can a zygote become a viable fetus. But, surely, we have here just another "problem." We can at least imagine a way to "eventually overcome" it, just as Levick imagines us overcoming the "severe epigenetic problems" rendering the clonote, at the moment, nonviable. Efforts at solving either of these "problems" would not gain my support nor, I presume, Levick's. So I am back to contending, as I did in my article, that we should use zygotes for babies, clonotes for cells.
Paul McHugh, M.D.
Johns Hopkins University School of Medicine
Baltimore, MD 21205
The flaw in Sandel's argument is that human embryos differ from other human beings not in the kind of entity they are, but in their stage of development. A human embryo is a human being in the embryonic stage, just as an infant or an adolescent is a human being in the infant or adolescent stage. In fact, every adult was once an embryo, just as he or she was once an adolescent, a child, an infant, and a fetus.
What about Sandel's analogy? It collapses the moment one considers why we value mature oak trees and feel a sense of loss at their destruction. Contrast that with why we value human beings. We value oak trees because of certain accidental qualities, such as their magnificence (a certain grandeur that has taken perhaps several decades to achieve). If oak trees were valuable by virtue of the kind of entity they are, then it would follow that it is just as unfortunate to lose an acorn as it is to lose an oak tree. But oak trees and acorns are not equally valuable, because the basis for our valuing the trees is not the kind of entity they are but rather those accidental characteristics (e.g., the magnificence that comes only with maturity) by which they differ from acorns and members of the species at early developmental stages, such as saplings.
People typically regard oak saplings as no more valuable than acorns. Forest managers regularly destroy saplings to maintain the health of mature trees, and no one regrets their loss or gives the matter a moment's thought. If we valued oaks (as we value humans) by virtue of the kind of entity they are and not by virtue of accidental qualities, we would regard their deaths in the way we regard the deaths of children — the precise equivalent to saplings in Sandel's analogy. No decent person believes that children — even severely retarded children — may legitimately be killed in order to provide vital organs for adults. Yet anyone who credits Sandel's analogy will have abandoned the intelligible basis of this belief.
Robert P. George, J.D., D.Phil.
Princeton University
Princeton, NJ 08540
Patrick Lee, Ph.D.
Franciscan University of Steubenville
Steubenville, OH 43953
References
Sandel MJ. Embryo ethics -- the moral logic of stem-cell research. N Engl J Med 2004;351:207-209.
To the Editor: Sandel has pointed out that there is no defining moment in the development of a human being from the stage of a zygote to birth. He proposes that "the fact that every person began life as an embryo does not prove that embryos are persons." And yet, what is an embryo if not a human at an early stage of life? Sandel states that "human life develops by degrees." What degrees? What marks the transition from one degree to another? If an embryo is not a person, when does a person become a person? Rather than being logically rigorous in his arguments, Sandel relies on rationalization. But please do not confuse rationalization with ratio (Latin for reason). Chief among these rationalizations is his contention that if we allow a practice to occur, it must not be immoral — if it was immoral, we would never allow it. The folly of such circular reasoning should be obvious to even the most committed proponents of this potentially promising research.
G. Neal Kay, M.D.
University of Alabama at Birmingham
Birmingham, AL 35294
To the Editor: Sandel's use of the analogy of acorns and sequoias suggests that he places human embryonic life on a quantitative scale that includes plants and animals. It is obvious to everyone that every human adult was once an embryo and that an embryo that is destroyed does not become an adult, although it had the potential to do so. So why do we think that an embryo deserves only a "certain respect," and why don't we treat it with even greater respect than we treat an adult, because of its exquisite vulnerability and its unimaginable potential to live into adulthood and enhance even our own lives? Maybe it is a lack of imagination on the part of scientists in general, or maybe it is the tendency that society has to undervalue and exploit its vulnerable and dependent members. Clinicians, however, surely must see the paradox of sacrificing a new person's life in its simplest expression in an attempt to cure disease.
Patrick M. Pullicino, M.D.
New Jersey Medical School
Newark, NJ 07103
pullic@umdnj.edu
To the Editor: Sandel presents a clear understanding of the issues regarding stem-cell research. However, the analogy between acorns and oak trees as "different kinds of things" and human embryos and human beings as different kinds of things fails as an argument. Do we really wish to elevate sentience as the final benchmark? And when do experience and consciousness "make higher claims still"? Where does this leave the severely demented person with Alzheimer's disease or the severely handicapped child? At what point do we say human life developing "by degrees" can be dubbed fully human, with all the inalienable rights thereto?
What need is there to treat an embryo with respect if it is different in kind and less than a "full human being"? Does not the embryo possess all the genetic stuff of full humanness?
Yes, natural procreation does entail the loss of some embryos for every successful birth, but this is natural, whereas the intent with stem-cell research is purposeful and humanly directed, and therein lies the rub.
Ross E. Anderson, M.D.
Allina Medical Clinic–Shoreview
Shoreview, MN 55126
To the Editor: Sandel provides a thoughtful philosophical overview of the current policy dilemma concerning embryo ethics. The most helpful approach, however, may involve addressing the psychology underlying the stem-cell controversy — most important, the perennial fear of new technology.
Seen in this light, embryo ethics is a novel permutation of a very old motif. Anesthesia was once decried as immoral because it contravened God's will for women to suffer during labor, and in vitro fertilization was initially assailed as a dehumanizing slippery slope.
The fundamental fears underlying such claims may be resolved without directly affirming or denying the values they represent. In fact, that is how responsible physicians attend to the concerns of patients whose private values may differ from their own. Opponents of stem-cell research seem to sense, from precedent, that it is inevitable. By listening tolerantly to all angles of input, we ease the anxieties aroused by such a sense of inevitability. And by restraining the impulse to make value judgments, we keep each new wave of technology tension in proper historical perspective.
Christian P. Erickson, M.D.
Loma Linda University Medical Center
Redlands, CA 92373
christianerickson@alumni.duke.edu
To the Editor: In his Perspective article on research involving embryonic stem cells, the ethical distinction that McHugh (July 15 issue)1 makes between a human zygote and "clonote" is useful only if an embryonic clone is fated to die before birth from severe epigenetic problems. If these problems are eventually overcome, a zygote produced by in vitro fertilization and a clonote produced by somatic-cell nuclear transfer should be treated identically. The purpose of their creation would be immaterial. Without uterine implantation at an early embryonic stage, neither could develop into a viable fetus, making it ethically justifiable to extract stem cells from either.
The same moral logic also compels the granting of special status to an implanted human embryo, whether it originates as a zygote or as a clonote. Furthermore, any child born should be afforded equal rights, regardless of its reproductive origins.
However, even if the epigenetic problems of reproductive cloning were resolved, substantial psychological and social risks would remain.2 These alone would make it unethical to use reproductive cloning to create a genetic replica of another human being.
Stephen E. Levick, M.D.
University of Pennsylvania School of Medicine
Philadelphia, PA 19104
s.levick@worldnet.att.net
References
McHugh PR. Zygote and "clonote" -- the ethical use of embryonic stem cells. N Engl J Med 2004;351:209-211.
Levick SE. Clone being: exploring the psychological and social dimensions. Lanham: Md.: Rowman & Littlefield, 2004.
Dr. Sandel replies: Erickson speculates that some people oppose stem-cell research because they fear new technology. Whether or not this is true, the principled arguments they offer are worth taking seriously. The controversy cannot be resolved, as Erickson suggests, "by restraining the impulse to make value judgments." As the other letters reflect, the debate over embryonic stem-cell research cannot be decided without addressing the moral status of the embryo.
Anderson argues that the embryo possesses "all the genetic stuff of full humanness." But the same could be said of a human skin cell. And yet no one would argue that a skin cell is a person or that destroying it is tantamount to murder. Pullicino writes that "every human adult was once an embryo" and that "an embryo that is destroyed does not become an adult, although it had the potential to do so." But it is also true that every human being originated with an egg and a sperm, and that an egg or a sperm that is destroyed does not realize its potential to become a human being. Would Pullicino therefore attribute personhood to eggs and sperm? He might reply that most eggs and sperm do not develop into human beings. But neither do most fertilized ova.
Kay points out, rightly, that allowing a practice to occur does not make it moral. But I did not defend embryonic stem-cell research on the grounds that it occurs. Perhaps he is referring to my observation that U.S. fertility clinics are permitted to create and discard excess embryos. But the point of the analogy to in vitro fertilization was simply to show that those who would ban embryonic stem-cell research should also seek to ban all infertility treatments that create and destroy excess embryos.
George and Lee write that the developmental continuity between blastocysts and human beings proves that embryos and persons are the same "kind of entity" and therefore are morally equivalent. My article sought to refute this argument by analogy: all oak trees were once acorns, but this does not prove that acorns are oaks or that the loss of an acorn is as tragic as the destruction of an oak. George and Lee reply by insisting that acorns and oaks are the same kind of entity; we value the oak tree more only because it happens to be magnificent, which is an "accidental," not an essential, characteristic. Respect for human life, they argue, should be irrespective of such accidental traits as magnificence, maturity, or developmental stage. Even accepting their quaint metaphysical distinction between essential and accidental traits, what makes them so confident about which is which? Isn't it in the nature of an oak tree to be magnificent? If so, we should regard the acorn as a potential oak. And isn't the fact that we develop within and are born of a biologic mother an essential characteristic of human beings? If so, we should regard the preimplantation embryo not as a person but as a potential human life.
Michael J. Sandel, D.Phil.
Harvard University
Cambridge, MA 02138
Dr. McHugh replies: Levick and I agree on much, such as opposing reproductive cloning. But I do think the distinction in nature between in vitro fertilization and somatic-cell nuclear transfer has ethical weight for the reasons I mentioned. It is true, at the moment, that only when it is implanted in a uterus can a zygote become a viable fetus. But, surely, we have here just another "problem." We can at least imagine a way to "eventually overcome" it, just as Levick imagines us overcoming the "severe epigenetic problems" rendering the clonote, at the moment, nonviable. Efforts at solving either of these "problems" would not gain my support nor, I presume, Levick's. So I am back to contending, as I did in my article, that we should use zygotes for babies, clonotes for cells.
Paul McHugh, M.D.
Johns Hopkins University School of Medicine
Baltimore, MD 21205