Encyclopedia of Bioethics: Vol 2

Crowe, Raymond R. 1984. Electroconvulsive TherapyA Cur-rent Perspective. New England Journal of Medicine 311(3):163-167.Culver, Charles M.; Ferrell, Richard B.; and Green, Ronald M.1980. ECT and Special Problems of Informed Consent.American Journal of Psychiatry 137: 586-591.Gert, Bernard; Culver, Charles M.; and Clouser, K. Danner.1997. Bioethics: A Return to Fundamentals. New York: Oxford.Group for the Advancement of Psychiatry. Committee on Medi-cal Education. 1990. A Casebook in Psychiatric Ethics. NewYork: Brunner/Mazel.Heshe, Joergen, and Roeder, Erick. 1976. ElectroconvulsiveTherapy in Denmark. British Journal of Psychiatry 128:241-245.Kesey, Ken. 1962. One Flew over the Cuckoos Nest. New York:New American Library.Merskey, Harold. 1991. Ethical Aspects of the Physical Manipula-tion of the Brain. In Psychiatric Ethics, 3rd edition, ed. SidneyBloch and Paul Chodoff. Oxford: Oxford University Press.Ottosson, Jan-Otto. 1985. Use and Misuse of ElectroconvulsiveTreatment. Biological Psychiatry 20(9): 933-946.Smith, Daniel. 2001. Shock and Disbelief. Atlantic 287(2):79-90.Strayhorn, Joseph M., Jr. 1982. Foundations of ClinicalPsychia-try. Chicago: Year Book Medical Publishers.Taylor, John R.; Tompkins, Rachel; Demers, Renee; and Ander-son, Dale. 1982. Electroconvulsive Therapy and MemoryDysfunction: Is There Evidence for Prolonged Defects? Bio-logical Psychiatry 17(10): 1169-1193.Willner, Paul. 1985. Depression: APsychobiologicalSynthesis. NewYork: Wiley.EMBRYO AND FETUS I. Development from Fertilization to BirthII. Embryo ResearchIII. Stem Cell Research and TherapyIV. Religious PerspectivesI. DEVELOPMENT FROMFERTILIZATION TO BIRTHThe ethical relevance of studying human developmentappears when one asks which stages of the human life cycleembody significant ethical concerns. Between birth anddeath, the human organism is a person, equipped with thefull measure of basic human rights. This much is not reallycontroversial, and the debate primarily concerns the prenatalphase of development. Do human rights accrue to theunborn all at once, for instance at fertilization? Do theyinstead arise in a gradual manner, based on the variousprogressive steps through which the prenatal human organ-ism acquires significant person-like properties? Besides per-sonal rights, are there other ethically-significant values andproperties that would justify a respectful treatment of em-bryos and fetuses? An understanding of prenatal develop-ment is a necessary, albeit in no way sufficient, condition foraddressing these issues successfully.To understand the basic biology of any sexually repro-ducing organism, one needs to grasp the primary concept ofthe life cycle. The life cycle of humans includes fertilization,cleavage, gastrulation, organogenesis, fetal development,birth, child development and puberty, gametogenesis andagain fertilization. It is through the germ-line that the lifecycle persists from generation to generation. On the otherhand, the somatic cells (which comprise all the cells of thefetus, child, and adult that are not directly involved inreproduction) belong to an inherently mortal entity, thehuman organism, whose fate is senescence and death. Oneturn of the life cycle defines one generation. Fertilization andbirth define the beginning and end of the prenatal phase ofdevelopment, which is comprised of two stages: embryonicand fetal.The embryonic phase initiates with fertilization, themeeting of the male (sperm) and female (oocyte) gametes,giving rise to the zygote. At fertilization, a new, diploidgenome arises from the combination of the two haploidgenomes included in the gametes. The zygote divides severaltimes (cleavage stage) to form a blastocyst. The cells of theblastocyst, called blastomeres, are separated into two parts:an outer layer, called the trophoblast, that eventually contrib-utes to the placenta; and an inner cell mass that contributesto the future embryo. About six days after fertilization, theblastocyst attaches to the endometrium (the epithelial liningof the uterus). This marks the beginning of pregnancy andfurther development depends on intricate biochemical ex-changes with the womans body. While the trophoblastinvades the uterine wall, the inner cell mass undergoesfurther stepwise differentiation processes that lead to theformation of the embryonic epiblast (the precursor of theactual human individual) and several extraembryonic struc-tures (Figure 1). The embryo then undergoes gastrulation,the process that starts with the formation of the primitivestreak. This is the crucial developmental step, common to all

animals but the most primitive invertebrates, by which thethree basic germ layers of the embryo are formed. These arecalled ectoderm, mesoderm, and endoderm.From the third to the eighth week, the process oforganogenesis involves the differentiation of the three germlayers into specific tissues and primordial organs. The earli-est stage in organogenesis is called neurulation and startswhen a specific area of ectoderm turns into the primordiumof the nervous system. During organogenesis, many genesthat are crucial to development are activated, and complexcelltocell signals insure the proper differentiation of vari-ous cell types, as well as the movement and migration of cellsto their proper places in the developing embryo. For somecell types, this involves long-range navigation. For instance,the gamete precursors must travel from their initial positionnear the yolk sac to the primordial gonads.At the end of the embryonic phase, many importantorgan systems are in place, at least in rudimentary form. Thefetal phase is characterized by further differentiation andmaturation of tissues and organs, as well as considerablegrowth, especially towards the end of pregnancy. In the latefetal phase, the nervous system undergoes an acceleration ofsynapse formation and maturation of the brain, which isincreasingly sensitive to outside cues. This process continueswell after birth.Specific Developmental Stages in DetailEspecially in early development, specific developmentalprocesses seem more meaningful than others in the ethicaldebate about the moral status of human prenatal life. Theseare described in more detail.GAMETOGENESIS AND FERTILIZATION. The embryo isusually defined as coming into existence at fertilization andbecoming a fetus when organogenesis is completed (eightweeks after fertilization). These borders are not sharplydefined. The definition of an embryo thus cannot avoidbeing operational and context-dependent. The term conceptusis useful to denote any entity resulting from fertilization,when no reference to a more specific stage is intended. Anadditional complication results from the significant overlapbetween the final stages of female gametogenesis, fertiliza-tion, and initial cleavage.Gametogenesis involves a special type of cell divisioncalled meiosis. When primordial germ cells (which arediploidi.e., they have two complete sets of chromosomes)enter meiosis, their DNA is duplicated so that there are nowfour copies of each type of chromosome (a condition calledtetraploidy). In the first meiotic division, there are geneticexchanges within each group of homologous chromosomes,which then separate into diploid daughter cells. In thesecond meiotic division, there is no further round of DNAduplication. Each chromosome in a pair is allotted to aseparate daughter cell, now haploid. Each primordial germcell thus gives rise to four daughter haploid cells.In the male, all four cells resulting from meiosis ulti-mately become functional spermatozoa. In contrast, in thefemale, only one of the daughter cells becomes an oocyte, theother three cells are discarded as polar bodies. In addition,female meiosis is not completed until after fertilization hasoccurred. During each ovarian cycle of the sexually maturefemale, one oocyte progresses partially through meiosis butis arrested in the middle of the second meiotic division at thetime it is discharged from the mature ovarian follicle into theoviduct. If the oocyte is fertilized, meiosis is completed.Within the newly fertilized egg, the male and female pronucleiundergo a protracted migration towards each other, whileDNA is duplicated within both. Thereafter, both nuclearenvelopes disappear and the chromosomes derived from themale and female gamete are involved in the first cleavagedivision. Thus the first genuine diploid nucleus is observedat the two-cell stage only (30 hours after initial contact ofsperm and oocyte). While fertilization usually occurs close tothe ovary, the conceptus is gently nudged towards theuterus, a voyage lasting about five days.Both through recombination of gene segments duringthe first meiotic division, and through random assortment ofhomologous chromosomes in gametes, genetic novelty isgenerated. In other words, gametes are genetically distinctivein relation to their diploid progenitors and do not simplyreflect the genetic structure of their parent organism. In asense, gametes are distinctive individuals in relation to theorganism that produces them. Fertilization creates geneticnovelty of a different sort, by combining two independentpaternal genomes. The zygote is genetically distinctive be-cause it represents the meeting of two independent parentallineages. Thus genetic novelty appears twice per turn of thehuman life cycle.CLEAVAGE, PLURIPOTENTIALITY, AND TWINNING. Dur-ing cleavage, the zygote divides into smaller embryonic cells.At the 16-cell stage, the embryo is called a morula and a firstdifferentiation into two cell types is initiated. The trophoblastis the cell layer that will soon connect with the uterine wall,whereas the inner cell mass includes the cells of the later stageembryo. At the blastocyst stage, a central cavity (blastocoel)is formed. If a blastomere is removed from the inner cell

FIGURE 1Derivation of Tissues in Human Embryos

Epiblast

EXTRAEMBRYONICTISSUES

- Cytotrophoblast

source: Gilbert, 2000.

mass of a blastocyst (as, for instance, in preimplantationdiagnosis), the blastocyst is still able to produce a completelate embryo and fetus. This illustrates a fundamental princi-ple called regulation, or regulative development. Within theearly embryo, cell fates are not definitely fixed but largelydepend on interactions with neighboring cells, so thatdevelopment adjusts to the presence or absence of specificenvironmental cues. The molecular basis and the genesresponsible for these cues are increasingly well known.At the blastocyst stage, the inner mass cells are pluripotent(i.e., they have developmental plasticity) and are able toparticipate in the formation of most cell types of the adultorganism, as shown for instance by experiments with cul-tured immortalized blastomeres, called embryonic stemcells. Recent research does suggest that individual blastomeresacquire some degree of molecular specificity quite early.However, this inherent bias that tends to drive everyblastomere towards a specific cellular fate can easily beoverridden at this stage.Around day 6, the blastocyst has hatched from thesurrounding zona pellucida (the outer envelope of theovum) and is ready for implantation. As it attaches to theendometrium, two distinctive layers appear in the inner cellmass. The ventral layer (hypoblast) contributes to the primi-tive yolk sac. The dorsal layer soon differentiates between theembryonic epiblast that will contribute to the embryotobe, and the amniotic ectoderm lining the newly appearingamniotic cavity (day 78). This twolayered structure iscalled the embryonic disk. All this happens as the blastocystburrows deeper into the uterus wall and the trophoblastcomes into close contact with maternal blood vessels. Thetrophoblast also produces human chorionic gonadotropin(hCG), which is the substance detected in pregnancy testsand is essential to the maintenance of pregnancy. Abnormalconceptuses are very common until that stage and areeliminated, usually without detectable signs of pregnancy.Inversely, fertilization occasionally results in a hydatidiformmole. This structure consists of trophoblastic tissue andtherefore mimics the early events of pregnancy (hCG isproduced), without their being any actual embryonic tissuepresent.The term pre-embryo was often used to mark theembryonic stages described so far. This term is sometimesshunned in contemporary discourse, as it has been suspected

to be a semantic trick to downgrade the standing of the veryearly embryo. Yet even writers like Richard A. McCormickbelonging to the Catholic tradition, sets great store by themoral standing of the earliest forms of prenatal develop-ment, have expressed doubts about the validity of thissuspicion (1991). More importantly, doing away with theterm preembryo does not solve the two underlyingconceptual problems that this term addresses. The firstensues from the cellular genealogy linking the zygote to thelater stage embryo and fetus. Only a small part of the veryearly embryo is an actual precursor to the late embryo, fetus,and born child. Whatever terminology one wishes to use, noaccount of early development can avoid sentences such asthis, written by Thomas W. Sadler in 2000, [t]he inner cellmass gives rise to tissues of the embryo proper, or terms suchas the embryotobe. This is an inescapable consequence ofthe fact that the late embryo includes only a small subset ofall the cells that originate with the zygote and blastocyst(Figure 1 shows the complex genealogy of embryonic andextraembryonic tissues in human development). The secondproblem arises from the fact that the early embryo has adegree of freedom as regards its final numerical identity.Until about 12 days after fertilization, twinning can occur.In other words, until that stage, a single embryo still has thepotential to divide in two embryos, ultimately developinginto two separate persons. Therefore there is no intrinsiconetoone relationship between the zygote and the lateembryo, as there is between the late embryo, the fetus, andthe born human.GASTRULATION. Gastrulation begins with a wave of cellu-lar movements that start at the tail end of the embryo andextend progressively forward. Future endoderm and mesodermcells slip inside the embryonic disk through a groove calledthe primitive streak (day 14). The anterior end of the streakis called the node. Of the cells that migrate inside the streak,some form the endoderm and others will lie atop theendoderm and form the mesoderm. Finally, those cells thatremain in their initial position on the surface of the embry-onic disk become the ectoderm. Gastrulation sets the overallorganization of the embryo in a definitive way. The mainaxes (anteriorposterior, leftright) are defined under thecontrol of two central signaling centers: the node (which isthe equivalent of the organizer discovered by embryologistsworking on frog and chick embryos) and the anteriorvisceral endoderm.Recent data from molecular genetics have partiallyuncovered the molecular basis of axis determination. Thedetermination of the anteriorposterior axis involves theHOX genes, a set of four gene complexes. Since HOX geneslocated at the front end of a HOX complex are expressedat the front end of the embryo, the arrangement of thevarious genes within each complex remarkably reflects theplace at which they are expressed in the embryo along theanteriorposterior axis. The four HOX complexes thusprovide four genetic images of the lengthwise arrangementof embryonic structures. The leftright asymmetry of theembryo (and thus of the future body plan) is thought tooriginate with specific cells in the node. In a way that is notfully understood, these cells induce a cascade of proteinsignals that is different on the left and right side of theembryo. This results in the synthesis of controlling factorsthat are laterally restricted. It is supposed that these control-ling factors and other factors direct the development ofasymmetric organs accordingly.Through gastrulation, the embryo arises as a definedentity endowed with a much higher level of organic unitythan at any stage before. The laying down of the headtotail axis and other defined spatial features, as well as the lossof pluripotentiality in many cell lineages, mark the begin-ning of a single individual human organism and thusprovide one of the first important dimensions of the onto-logical continuity typical of the born human.LATER DEVELOPMENTAL STEPS. In the initial step inorganogenesis, the midline axial section of mesodermthenotochordinstructs the overlying ectoderm to turn intothe neural plaque. This structure soon wraps around to formthe primitive neural tube, out of which the central nervoussystem will eventually grow. By the beginning of the fetalperiod (eighth week), the rudiments of the heart, blood andblood vessels, the major segments of the skeleton andassociated muscle groups, the limbs, and many other struc-tures are in place. It is noteworthy that although theprimordial nervous system is one of the earliest organsystems to emerge in development, it takes the longest timeto mature. Synaptogenesis (the formation of contacts be-tween nerve cells) starts on a grand scale only late inpregnancy and continues well after birth. This is importantto keep in mind when interpreting early movements of thefetus, visualized more and more accurately by ultrasonography.These movements reflect the maturation of local neuromus-cular structures and are not due to significant brain func-tion, since there is no brain in the sense of the later, muchmore developed anatomic and functional structure called bythat name. This is different later in pregnancy, when fetalmovement is more reactive to the environment and when itbecomes arguably legitimate to interpret it as behavior,insofar as it reflects the increased functional capabilities ofthe central nervous system. Finally, the concept of viabilitybasically reflects the ability of fetal lungs and kidneys to

support extrauterine life, which is impossible before thetwenty-second week.As mentioned before, the differentiation and migrationof early gametes also occurs during the embryonic phase.This separation of the germ cell lineage from all other celllineages marks a bifurcation in the life cycle. Unlike somaticcells, gamete precursors have a chance of becoming gametesand participating in fertilization, thus contributing to thenext generation. In a way, the germ cell lineage is eternalthrough successive turns of the life cycle, whereas the rest ofthe embryo, the sum total of somatic cells, is inherently mortal.Extracorporeal EmbryosScience fiction fantasies about the artificial uterus notwith-standing, only the very first stages of human developmentcan occur outside the female body. Since 1978, in vitrofertilization followed by embryo transfer has been a com-mon treatment of fertility problems. The growth of ovarianfollicles is stimulated by the administration of gonadotropins.Oocytes are then collected by laparoscopy and placed in anappropriate culture medium. Sperm is added and cleavageoccurs in culture until the blastocyst is transferred in the uterus.With in vitro fertilization, the early embryo becamemuch more accessible to human intervention, and this hasraised ethically perplexing possibilities. Interventional re-search on early embryos has become possible, raising thequestion of whether it is ethical to produce human embryosfor research purposes, or whether research should be done, ifat all, only on spare embryos. These occur when someembryos are no longer needed for fertility treatment, eventhough they resulted from in vitro fertilization performedwith therapeutic intent. Additionally, progress in genetictesting techniques using very small amounts of DNA hasmade preimplantation diagnosis of genetic abnormalitiespossible. Single blastomeres are removed from in vitroblastocysts, their DNA amplified by polymerase chain reac-tion (PCR), and subjected to genetic tests with appropriateDNA probes. (Thanks to regulative development, the miss-ing blastomere is soon compensated for.) In this way,embryos can be screened for certain genetic defects and onlythose free of defects chosen for embryo transfer. Thisprocedure is sometimes suspected of being eugenic, and thecontroversy around it has led to it being outlawed in certaincountries including Germany and Switzerland.Developmental Steps and Moral StatusThe biological processes around fertilization and early em-bryonic development are often accorded considerable rele-vance in ethical debates, making a detailed description ofthese processes necessary. This descriptive effort, however, isnot based on the belief that the facts speak for themselves.They emphatically do not. In fact, many ethical controver-sies about the ethics of in vitro fertilization, embryo research,therapeutic cloning, abortion and the like, are less aboutethics in the strict sense as they are about expressing diver-gent interpretations of biology. The marshalling of biologi-cal fact to support apodictic statements of moral statusinvolves many, usually unspoken, bridge principles. Theseprinciples involve highly complex notions, such as unity,individuality, potentiality, and continuity. It is a commonmisconception that these theoretical concepts constitutestable, common-sense notions that are merely applied tobiological entities and processes. In actuality, these conceptsare themselves given new meanings and qualifications in thevery process of using them to make sense of biological facts.Between the realm of ontological categories and the empiri-cal domain of biology, there is a two-way street.It is often said that human life begins at fertilization.Strictly speaking, this statement is meaningless. Human lifedoes not begin at any point of the human life cycle; it persiststhrough successive generations. The ethically relevant ques-tion to ask is at what stage a human individual is firstendowed with important ethical value and correlative rightsagainst harm. The difficulty is that no particular step standsforth as a self-evident developmental marker, both becausedevelopmental events that appear as sharp discontinuitiesturn out to be protracted processes upon closer scrutiny (forinstance, fertilization is a process, not an instantaneousevent), and because the highlighting of one developmentalprocess over another necessarily involves more or less plausi-ble philosophical assumptions.Three different concepts of individuality appear to berelevant: genomic individuality as established troughfertilization; numerical identity, defined once twinning is nolonger possible; identity of the self, as sustained by a functionalcentral nervous system.Fertilization is important because it newly connects twoparental lineages that were independent until then. Themeeting of sperm and oocyte gives rise to a uniquely noveldiploid genome that is not subject to further change. It willbe the genome of the future person or persons arising fromthis particular fertilization. This fact is often misinterpretedaccording to a hylomorphic interpretation of the genome,where the latter becomes the formal cause of the futurehuman being (Mauron). (Hylomorphism is the aristotelianand scholastic teaching that concrete objects, especially

living things, result from a combination of form [morphe]and substance [hyle].) This interpretation suggests the no-tion that fertilization is the single crucial step, since the newgenome appears at that point. This interpretation fails, notonly because of the inherent conceptual problems of thehylomorphic view, but also because there exist biologicalfacts such as twinning and genetic mosaicism that show thatthere is little connection between genomic individuality assuch and personal identity. Monozygotic or identical twinsare separate persons, even though they share the samegenome, that originated from the same fertilization. Thisshows that genomic individuality does not provide any basisfor the most essential property of personal identity, namelynumerical identity through time. To be one and sameperson through changes in ones biography is an essentialingredient of any workable concept of the person, and thebiological basis for this property does not originate beforegastrulation. In fact, much of the organic singularity andcoordinated functioning as one organism (rather than sev-eral potential organisms) is established only at that stage.However, one may want a richer interpretation of thisbasic criterion of personal identity. Having a biography ofones own is not just being the same individual throughtime, but also experiencing a continuity of mental states,which is linked to an at least minimally-functioning centralnervous system. In fact, nothing is more central to themodern conception of the self than the functional persist-ence of a central nervous system that provides the materialsubstrate of an individual subjective biography. For thisbiographical, or subjective, identity, it is difficult to quote adefinitive starting point. It is plausible to place it in latepregnancy, when the earliest possibility of a continuing selfseems to be given, but there is no absolute certainty inthis claim.ConclusionEthical reasoning on this topic often shows a commonpattern: one takes moral concepts that belong touncontroversial persons (such as grown humans) and tries toapply them backwards to the fetus and embryo. However,importing intuitions pertaining to the ethics of personalrights and interests onto various forms of prenatal life isincreasingly fraught with conceptual difficulties as one movestowards earlier stages. Indeed, the most perplexing problemin bridging human developmental biology and statements ofmoral standing is perhaps that traditional moral categoriestend to be all-or-none concepts (either one is a person ornot, and if so, one is equal in basic rights to all persons),whereas developmental biology shows mostly gradual changeand tends to resolve what appear to be discrete borders intocontinuities. One obvious and popular answer to this quan-dary is to make ethical standing a gradually increasingproperty of the developing human organism. On the otherhand, one may query the underlying assumption that thereis a one-dimensional measure of ethical concern. Furtherreflection may benefit from a recognition that ethical con-cerns about human prenatal life are multidimensional, andsometimes qualitatively, not just quantitatively, differentfrom the person-centered systems of ethical values and duties.ALEXANDRE MAURONSEE ALSO: Abortion: Medical Perspectives; Alcoholism andOther Drugs in a Public Health Context; Cloning; Death,Definition and Determination of: Criteria for Death; Femi-nism; Infants; Infanticide; Maternal-Fetal Relationship; MoralStatus; Reproductive Technologies: Ethical Issues; and otherEmbryo and Fetus subentriesBIBLIOGRAPHYFord, Norman M. 1988. When Did I Begin? Conception of theHuman Individual in History, Philosophy and Science. Cam-bridge, Eng.: Cambridge University Press.Gilbert, Scott F. 2000. Developmental Biology, 6th edition.Sunderland, MA: Sinauer Associates.Green, Ronald M. 2001. The Human Embryo Research Debates:Bioethics in the Vortex of Controversy. Oxford: Oxford Univer-sity Press.Mauron, Alex. 2001. Is the Genome the Secular Equivalent ofthe Soul? Science 291: 831-832.McCormick, Richard A. 1991. Who or What Is the Preembryo?Kennedy Institute of Ethics Journal 1: 1-15.Robertson, John A. 1991. What We May Do with thePreembryos: A Response to Richard A. McCormick. KennedyInstitute of Ethics Journal 1: 293-302.Sadler, Thomas W. 2000. Langmans Embryology, 8th edition.Baltimore, MD: Lippincott Williams & Wilkins.INTERNET RESOURCESGilbert, Scott F. 2000. When Does Human Life Begin?Website to accompany Developmental Biology, 6th edition.Available from .II. EMBRYO RESEARCHIn previous editions of this encyclopedia, the topic ofembryo research was included within the entry on fetalresearch. However, during the latter part of the twentiethcentury the issues arising from research involving in vitrofertilized embryos became sharply distinguished from issuesin research with already-implanted fetuses. Moreover, new

technologies such as the development of embryonic stemcells and the possibility of human cloning raised new ethicalconcerns in relation to research involving human embryos.This entry will address the history of human embryoresearch, public policy on embryo research in the UnitedStates and internationally, moral considerations, particu-larly the debate on the moral status of the human embryo,and the relevance of ethical distinctions that have beenproposed, such as the distinction between research use ofsurplus embryos versus embryos created specifically forresearch.The Research SubjectScientifically the product of conception is called an embryountil eight weeks of gestational age, when the name changesto fetus. However, contemporary discussions of embryoresearch customarily restrict the term embryo to the earlieststages of human development before implantation in theuterus occurs. This terminology is supported by the U.S.federal regulations on fetal research, which define the fetus asthe product of conception from implantation until deliv-ery, thus excluding non-implanted embryos from the regu-lations (45 CFR 46.202).In practical terms the embryo as subject of research isthe embryo in the laboratory, generally the result of in vitrofertilization (IVF), but possibly developed by other means,for example, through flushing naturally-fertilized eggs fromthe fallopian tube, or through somatic cell nuclear transfer(SCNT) of a body cell into an enucleated egg, a type ofcloning procedure.A variety of terms has been proposed for the embryo assubject of research:the preembryo,the preimplantation embryo,the embryo ex utero,the early embryo.In this entry the simple term embryo will be used, with theunderstanding that it refers to the embryo in the laboratorythat has not undergone transfer to a woman. Some com-mentators maintain that only embryos resulting from fertili-zation of eggs by sperm are properly called embryos. Thisquestion will be addressed in later sections when it isrelevant.Early History of Embryo ResearchUntil the 1990s most research involving human embryoswas directed toward improving the chances for pregnancy inlaboratory-assisted conception. These investigations, in turn,were based on many years of research with animal models,where virtually all research in the United States has beensupported with federal funding. It was hoped that proce-dures developed in animal studies could later be applied tohuman reproduction and embryology, especially to theunderstanding and alleviation of human infertility.Attempts at laboratory fertilization of human oocytes(precursor eggs) showed some promise as early as 1944 in thework of American obstetrician-gynecologist John Rock andscientist Miriam Menkin. From that time until the birth ofthe first child conceived through IVF in 1978, variousapproaches were tried in order to achieve a pregnancy andlive birth. The work of Robert Edwards, British reproduc-tive endocrinologist, culminated in the birth of LouiseBrown after he collaborated with Patrick Steptoe, an obste-trician who utilized laporoscopy for viewing and recoveringa mature ovarian follicle containing an oocyte capable offertilization.According to embryologist Jonathan Van Blerkom,most current methods used in laboratory-based treatment ofinfertility have evolved from those used by Edwards andSteptoe and their predecessors. According to Van Blerkom,this work established the basic science foundation of clini-cal IVF (p. 9). Without these four decades of research onfertilizing oocytes, accompanied by study of the early cleav-age and development of fertilized eggs or zygotes, the clinicalpractice of IVF, which is an almost universally acceptedprimary treatment for infertility, would not exist.U.S. Funding and Regulation ofEmbryo ResearchIn 1975 the U.S. National Commission for the Protectionof Human Subjects recommended guidelines for federalfunding of research involving human fetuses, but stipulatedthat these guidelines did not cover research on IVF or onembryos resulting from IVF. It proposed that an EthicalAdvisory Board be appointed to review such protocols, andthis recommendation was incorporated into federal regula-tions. In 1978 an Ethics Advisory Board (EAB) was ap-pointed to recommend a policy on federal funding forresearch involving IVF.In its 1979 report the EAB concluded that research onIVF was ethically acceptable for federal funding under theseconditions: that all federally funded research is directedtoward establishing the safety and efficacy of IVF; allgametes used to develop embryos in research protocols areprovided by married couples; and no embryos are preservedin the laboratory beyond fourteen days of development. TheEABs rationale was based on two main points. First, it

would be irresponsible to offer clinical IVF without doingthe studies necessary to insure its safety and efficacy. Second,given the high rate of embryo loss in natural procreation, asimilar rate of loss could be tolerated for the goal ofeventually achieving pregnancies and births.The EAB did not distinguish between embryos createdfor research purposes and embryos remaining from infertilitytreatment. In fact, the board implied that at times it mightbe necessary to create embryos with no intent to transferthem to a woman. For the sake of safety, the results of newtypes of procedures would have to be studied in the labora-tory before the procedures were offered clinically. It wouldbe unethical to transfer to a woman the embryos resultingfrom unvalidated novel procedures.The EAB report elicited an outpouring of letters oppos-ing embryo research, and its recommendations were neverimplemented. When the EAB charter expired in 1980, asubsequent board was not appointed, thus leaving no bodyto review proposals for federal funding of IVF and embryoresearch. This situation effectively created a moratorium onfederal funding in the United States, though it did not affectresearch that was privately funded.Public Policy in Other CountriesIt is not possible to review all legislation and policy recom-mendations throughout the world, but two early initiativesare of particular interest. They come from countries thatshare a common law tradition with the United States,Australia (Victoria), and the United Kingdom.AUSTRALIA (VICTORIA). The earliest comprehensive legis-lation on reproductive technologies was enacted in the Stateof Victoria, Australia in 1984. The Infertility (MedicalProcedures) Act addressed embryo research by prohibitingresearch that might damage the embryo or make it unfit forimplantation. This prohibition appeared to outlaw any IVFor embryo research that was not directed toward benefitingeach individual embryo.In 1986 the review committee established by the actreceived a proposal for research on the microinjection of asingle sperm into an egg. In their application the investiga-tors suggested a novel approach for circumventing theprohibition on embryo research. They proposed to examinethe egg after the sperm had penetrated it, but before thegenetic contributions of the sperm and egg had fused at thestage known as syngamy. Arguing that fertilization was notcompleted until syngamy had occurred, researchers claimedthat the law did not apply until the time of syngamy, thusgiving them approximately twenty-two hours after spermpenetration for conducting their studies.Since the review committee was uncertain as to whetherthe 1984 act allowed this interpretation, it recommendedthat the act be amended to clarify that research was permissi-ble if it ended by the time of syngamy, even if the researchdestroyed the embryos potential for implantation. The actwas amended according to this recommendation in 1987.UNITED KINGDOM. The issue of the regulation of reproduc-tive technologies and embryo research was particularly press-ing in the United Kingdom because of the publicity given tothe birth of Louise Brown in England in 1978. The WarnockCommittee was appointed to study the matter, and its 1984report recommended national regulation of assisted repro-duction. It also recommended that research on embryosresulting from IVF be permitted up to the fourteenth dayafter fertilization, under the jurisdiction of a licensing body.Based on the Warnock Report, the Human Fertilisationand Embryology Act (HFE Act) of 1990 commissioned astanding body, the Human Fertilisation and EmbryologyAuthority (HFEA), to develop standards for licensing clini-cal facilities and research protocols, and mechanisms forauditing and oversight. Initially research protocols wererestricted to the study of infertility, the causes of congenitaldiseases, and the detection of gene or chromosome abnor-malities in embryos.Since its establishment in 1991 the HFEA has ad-dressed new types of procedures and research through publicconsultation processes as well as the advice of experts. If amatter was beyond the scope of authority of the HFEA, itwas referred to Parliament. In January 2001 Parliamentextended the HFE Act to permit embryo research directed atincreasing knowledge about treatments for serious diseases.This provision would allow the HFEA to issue licenses forresearch on embryonic stem cells, including stem cellsderived from blastocysts resulting from somatic cell nuclearreplacement (SCNR). However, the Pro-Life Alliance broughta challenge to this provision, arguing that the HFE Actapplied only to embryos resulting from the fertilization ofeggs by sperm. Despite a Court of Appeal ruling against thePro-Life Alliance, in June 2002 the House of Lords agreed tohear a final appeal of the case. In March 2003 the House ofLords ruled that the HFE Act applied to all types of embryos,and hence the HFEA had authority over research withembryos created by nuclear transfer as well as embryosresulting from fertilization by sperm.The U.S. Human Embryo Research PanelAfter nearly twenty years of moratorium on federal fundingof research involving IVF, the U.S. Congress in 1993revoked the requirement of EAB review. Through the

National Institutes of Health (NIH) Revitalization Act of1993, Congress explicitly permitted the NIH to fund re-search on assisted reproductive technologies with the goal ofimproving the understanding and treatment of infertility.Since research on IVF includes the study of IVF-fertilized embryos, the research authorized by Congressincluded research involving human embryos. Recognizingthe controversial issues raised by this research, NIH decidedto conduct an examination of ethical issues before fundingany research proposals. Consequently, the Director of NIHappointed the Human Embryo Research Panel (HERP) toprovide advice and recommendations.In developing its position and recommendations, thepanel focused on two distinct sources of guidance: view-points on the moral status of the early human embryo, andethical standards governing research involving human sub-jects. It considered a wide range of possible views on themoral status of the embryo, from the position that fullhuman personhood is attained at fertilization, to the argu-ment that personhood requires self-consciousness and is notattained until after birth. In the end, all nineteen members ofthe panel agreed to the following statement:Although the preimplantation embryo warrantsserious moral consideration as a developing formof human life, it does not have the same moralstatus as an infant or child. (Human EmbryoResearch Panel, p. x)This conclusion implied that the preimplantation em-bryo is not a full human subject and thus is not a fullyprotectable human being. As a result, some research thatmight be destructive to the embryo could be acceptable forfederal funding. But the panel also asserted that the humanembryo warrants serious moral consideration, requiringthat it be treated differently from mere human cells oranimal embryos. The panel proposed restrictions on embryoresearch that would express such moral consideration, forexample, that human embryos be used in research only as alast resort, that the number of embryos used be carefullylimited, and that embryos not be allowed to develop longerthan required by a specific research protocol, and in no caselonger than fourteen days of development.In applying the ethical standards governing researchinvolving human subjects, panel members invoked thecriteria used by Institutional Review Boards (IRBs) inapproving research protocols. Donors of eggs, sperm, orembryos were to be informed of the specific goals, proce-dures, and risks of research projects. Risks to donors, par-ticularly egg donors, were to be minimized. Eggs for researchcould be donated only by women who were undergoingdiagnostic or therapeutic procedures where egg retrievalwould present little additional risk.The most controversial issue facing the panel was thequestion of whether human oocytes could be fertilized solelyfor research purposes. The panel decided to allow suchfertilization only under very special circumstances, mostparticularly, if certain research by its very nature could nototherwise be conducted. For example, research on thelaboratory maturation of human oocytes, which could elimi-nate the need for egg donors as well as infertile women to besubjected to high levels of hormonal stimulation, requiresstudy as to whether such oocytes can be successfully fertilized.The panels limited acceptance of the fertilization ofoocytes for research purposes aroused strong criticism, andPresident Bill Clinton immediately announced his opposition.The Aftermath in the United Statesand BeyondDespite President Clintons directive that NIH not fundresearch involving the creation of embryos, most types ofresearch on IVF and human embryos were still eligible forfederal funding. However, in its next appropriations billCongress reversed its previous stance and prohibited NIHfrom funding any research that might involve damaging ordestroying human embryos. In 2003 this prohibition wasstill in effect.During the 1990s scientific advances raised new ques-tions regarding research with human embryos. In 1998 thefirst embryonic stem cell lines were developed from the innercell mass of human blastocysts, and at the same time, similarstem cell lines were produced from the germ cell tissue ofaborted fetuses. Deriving stem cells from blastocysts wasclearly prohibited for federal funding. However, the deriva-tion of stem cells from the tissue of aborted fetuses waseligible for federal funding under previous legislation (U.S.Public Law 10343, Manier).Another discovery was the successful cloning of avariety of nonhuman animals from adult cells, beginningwith the cloning of the sheep Dolly in 1997. Research onhuman cloning arguably involves research on human em-bryos. These embryos are produced by transfer of somaticcell nuclei into enucleated oocytes, rather than throughfertilization of eggs by sperm, yet their development andpotential appear to be similar to those of fertilized eggs. Thuscloning research raises similar ethical questions.The day after the announcement of the cloning ofDolly, President Clinton instructed the National BioethicsAdvisory Commission (NBAC) to undertake a thoroughreview of the technology and to report within ninety days.

Given this short deadline, it is understandable that NBAChad to focus on issues specific to the cloning process. Inparticular, NBAC decided to not revisit ... the issuessurrounding embryo research, since the topic had recentlyreceived careful attention by a National Institutes of Healthpanel, the Administration, and Congress (Shapiro).In contrast, when the Presidents Council on Bioethicsappointed by President George W. Bush issued its report oncloning in 2002, it called for a broader debate on the entiretopic of human embryo research. The ten-member majorityof the council wanted cloning discussed in the propercontext of embryo research in general and not just that ofcloning (p. 133). Both the majority and minority reportscall attention to the fact that human embryo research of alltypes remains essentially unregulated in the private sector,with the minority noting that it seems inappropriate to haltpromising embryo research in one arena (cloned embryos)while it proceeds essentially unregulated in others (p. 143).In the United States, public policy at the national levelis focused on what types of research are eligible for publicfunding. There is essentially no regulation of research in theprivate sector. This situation contrasts sharply with that ofmost other countries, where laws apply to all research,regardless of the funding source.As of April 2003, Germany, Austria, and Ireland pro-hibit embryo research unless intended to benefit the individ-ual embryo subject. Germany does allow some importationof established stem cell lines for research. France prohibitsany embryo research that would harm the embryo. How-ever, in January 2002 the French assembly passed a bill that,if enacted, would permit research using surplus embryosoriginally created for reproductive purposes. Sweden allowsresearch on surplus embryos up to day fourteen, includingresearch on deriving stem cell lines. Creating IVF embryossolely for research is prohibited, but creating embryos throughnuclear transfer is not mentioned in Swedish law and thushas an uncertain legal status. The United Kingdom arguablyhas the most permissive policies on embryo research withinthe European Union. It explicitly sanctions the granting oflicenses to create embryos, including cloned embryos, forspecific research projects.Because of the diverse views and policies of its memberstates, the European Union has taken an intermediateposition, providing support for research on surplus embryosin countries where that is permitted, but discouraging thecreation of embryos for research. In April 2003 the Euro-pean parliament voted for a ban on cloning or otherwisecreating embryos for stem cell research. However, thisdecision becomes law only if approved by all fifteen memberstates of the European Union.In May 2002 the Assisted Human Reproduction Actwas introduced into the Canadian Parliament. The actprohibits the creation of a human clone for any purpose. Italso prohibits the creation of an IVF embryo for researchpurposes with the exception of improving or providinginstruction in assisted reproduction procedures. In April2003 the bill was in its third reading in the House ofCommons.In some non-Western countries, embryo research isproceeding with few restrictions. Chinese laboratories areforging ahead with cloning research to develop stem cells.Though Chinese scientists have been slow to publish theirwork, they may well be ahead of their Western counterparts(Leggett and Regalado). India has developed a number ofinternationally recognized stem cell lines, and scientists aredeveloping additional lines. Dr. Firuza Parikh, Director ofReliance Life Sciences in Bombay, links their success to theabsence of cultural and political opposition to embryoresearch (Lakshmi).The Moral Status of the Early EmbryoIn contrast to China and India, most Western countries aredeeply divided over ethical issues related to embryo research.Does the embryo merit full protectability from the momentof fertilization, or does it gradually attain full protectabilityas it moves through a series of developmental stages? Iffertilization is not the point of greatest moral significance, isthere some later developmental marker beyond which em-bryo research ought not be conducted?FERTILIZATION. Fertilization of egg by sperm marks theinitiation of a new and unique genotype, that of a humanbeing distinct from either of its progenitors. The zygote orfertilized egg not only contains the plan or blueprint for anew human being, but it has the potential within itself todevelop into that human being.Based on these facts, many would argue that the zygoteis a full human being from the moment it comes intoexistence. This view would preclude any research that mightbe harmful or destructive to an embryo, unless intended tobe therapeutic for that embryo or to improve its chances forimplantation. This position has received able defense incontemporary terms by opponents of embryo research (Mc-Carthy and Moraczewski).It is possible to hold this position while acknowledgingthat fertilization is a process rather than an instantaneousevent, and hence that the new human life begins only whenthe process of fertilization is completed. At least two possiblecandidates marking the completion of fertilization havebeen suggested. The first is the time of syngamy, when the

chromosomes from the male and female gametes unite toform the genotype of the embryo. Since syngamy is notcompleted until about twenty-four hours after the spermpenetrates the egg, this view would allow some study of theearly development of the embryo.A second proposal maintains that the embryo does notbegin its life as a new human being until the regulation of itsdevelopment switches from oocyte genes to embryonicgenes. In 1988 Peter Braude and colleagues showed that thisoccurs at the six- to eight-cell stage, approximately two daysafter penetration of egg by sperm. Arguably the embryobegins its own life distinct from that of the oocyte at the timethat its own internal regulatory mechanism begins to func-tion. This interpretation would allow investigation of ques-tions such as why a large proportion of embryos are arrestedin their development during the earliest cell divisions (VanBlerkom).Such variant views of the process of fertilization do notcounter the claim that the human being begins its life atfertilization. Rather, they provide differing interpretationsas to what constitutes fertilization, under the assumptionthat the formation or activation of the unique genotype ofthe new organism is the crucial event.IMPLANTATION. Implantation is the process by which theembryo imbeds itself in the uterine wall and begins to takenourishment from the woman, thus marking the beginningof pregnancy. It is at this time that the U.S. federal regula-tions define the product of conception as a fetus, and theresearch regulations begin to apply (45 CFR 46.201207).From a moral point of view, some have argued that theIVF embryo lacks the potential to develop into a humanbeing as long as it is simply maintained in culture in thelaboratory. Only those embryos that are transferred towomen and that implant successfully acquire the potentialfor development. This type of argument has been utilized bypoliticians like U.S. Senator Orrin Hatch, who supportsome forms of embryo research while they take pro-lifepositions in relation to abortion. In his testimony to aCongressional subcommittee in July 2001, Hatch stated, Ibelieve that a humans life begins in the womb, not in a petridish or refrigerator.This view can be linked to a philosophic distinctionbetween possible persons, entities that could possibly developinto persons if certain actions were taken with respect tothem, and potential persons, entities that will develop intopersons in the normal course of events unless somethinghappens or is done to interrupt that development. Theembryo in the laboratory or freezer is a possible person thatmight develop into a person if action were taken to transfer itto a uterus. The already-implanted embryo or fetus is apotential person that, under normal circumstances, willcontinue to develop into a person. Proponents of thisdistinction argue that while we may have a moral obligationnot to interfere with the development of a potential person,we do not have a similar obligation to bring every possibleperson into existence (Singer and Dawson; Tauer 1997a).PRIMITIVE STREAK. In the late twentieth century, scholarswere faced with biological data about early embryonicdevelopment that led to new perspectives on the ontologicaland moral status of the early embryo. Particularly within theCatholic tradition, writers such as Norman Ford, JohnMahoney, Richard McCormick, and Karl Rahner developedarguments questioning whether the zygote or early embryois a full human being or human person. Their argumentsappealed to the following points:1. Twinning of the embryo is possible until implanta-tion, and at least through the morula stage, severalembryos may aggregate (recombine) to form oneembryo. Thus the embryo lacks developmentalindividuation at this early stage. Philosophic ar-guments that rely on the continuity of per-sonal identity and religious arguments based onensoulment must deal with the phenomena oftwinning and recombination, which occur naturallyand can also be induced scientifically.2. Until the blastocyst stage at approximately five daysafter fertilization, the cells of the embryo aretotipotent or completely undifferentiated. Each cellhas the capacity to differentiate into any of the cellor tissue types of the fetus, or more likely, not tobecome part of the fetus at all but rather to formplacental and other extra-embryonic tissues. Theearly embryo is a collection of undifferentiated cellsrather than an organized individual.3. At approximately fourteen days after fertilization, theprimitive streak appears, the groove along themidline of the embryonic disk that establishes in theembryo its cranio-caudal (head-to-tail) and left-rightaxes. The primitive streak marks the beginning ofthe differentiation of cells into the various tissuesand organs of the human body, and thus initiatesthe development of the embryo proper (the cellsthat will become the fetus) as an organized, unifiedentity. The primitive streak is also the precursor ofthe neural system.In normal procreation, during the period betweenfertilization and the completion of implantation alarge proportion of embryos (generally estimated atover 50%) are discarded naturally. Karl Rahnerargues that it is implausible that such a largenumber of human beings could come into existence

and disappear without anyones knowing about it.Others have argued that given natures prodigalitywith human embryos, it ought to be morallyacceptable to allow similar types of embryonic lossesin research as part of the effort to achieve healthypregnancies.These sorts of arguments have been utilized in publicpolicy debates since 1978, and the appearance of the primi-tive streak has come to be accepted internationally as amarker carrying moral significance. The prohibition ofembryo research after fourteen days of development isalmost universally accepted.Opponents of embryo research have responded toclaims that the early embryo is not yet a full human being.These commentators find arguments based on twinning andrecombination, totipotency of cells, and embryo loss to beunpersuasive (Ashley; Ashley and Moraczewski; Mirkes). Inits 2002 report on cloning, the majority members of the U.S.Presidents Council on Bioethics questioned the significanceof the primitive streak as a moral marker, stating:Because the embryos human and individual ge-netic identity is present from the start, nothingthat happens later ... at fourteen days or anyother timeis responsible for suddenly conferringa novel human individuality or identity. (p. 97)GASTRULATION AND NEURULATION. Some persons re-gard the initiation of the neural system or the presence ofbrain activity to be the most significant marker for thebeginning of the life of a human being. This view is based onthe belief that the brain is the essential organ underlying ourspecifically human capacities. It also represents an effort toidentify a criterion at the beginning of human life that isanalogous to the criterion of whole-brain death marking theend of life. For those who regard the presence of sentience asa necessary condition for personhood, the neural system issignificant since sentience is impossible in the absence of anyneural structures.While there is debate as to the stage at which brainactivity first occurs, it is certain that there is no brain activitybefore fourteen days of gestational age. The emergence ofthe primitive streak marks the very beginning of the devel-opment of the nervous system. If the presence of neuralstructures is the significant criterion for the beginning of ahuman life, then it might be permissible to extend embryoresearch slightly beyond fourteen days of development.Several possible cut-off points have been suggested. Bythe completion of gastrulation at about seventeen days, thethree germ layers of the embryo are in place, with cells ofeach layer committed to forming tissues and organs of one ofthree types. Subsequent neural development leads to thebeginning of closure of the neural tube around twenty-onedays, with the primitive nervous system in place by thecompletion of neurulation around twenty-eight days.However, given the widespread consensus that fourteendays of gestational age is a morally defensible boundary forembryo research, there has been limited discussion of ex-tending research to a later embryonic stage.Other Moral ConsiderationsThose who believe that the human embryo is a fullyprotectable human being have no choice but to opposeembryo research that could not ethically be performed oninfants or children. But those who maintain that the earlyembryo is not yet a full human being, still have to determinehow that embryo ought to be treated.Some have proposed severely restrictive criteria forembryo research. Norman Ford, after providing painstakingarguments to support the conclusion that the embryo can-not be a human individual until fourteen days after fertiliza-tion, acknowledges that he could be wrong. In his view, theCatholic Church is right to insist on the principle thathuman embryos should be treated as persons, even if theymay not be (2001, p. 160). In other words, as long as there isany degree of uncertainty regarding the moral status of theembryo, it must be absolutely inviolate.A more commonly held view is that the human embryohas an intermediate sort of moral status. While it is not afully protectable human being, it is not merely cells or tissue.Proponents of this view are generally willing to permit someembryo research with restrictions that acknowledge that theembryo is nascent human life or a developing form ofhuman life. Our ethical obligation toward the embryo isoften characterized as respect or profound respect.Proponents as well as opponents of embryo researchhave questioned the concept of respect as a guide for humanembryo research. John Robertson, an advocate of scientificfreedom with respect to embryo research, believes the notionof respect carries mainly symbolic significance. Hence itspractical ramifications are vague, potentially allowing a widerange of types of research. Daniel Callahan, in an essayopposing most embryo research, wonders how one showsrespect for a living being while intending to end its life andfuture potential, even if done for a good purpose such asresearch on infertility or disease.In an effort to express respect for the special status of thehuman embryo, public policy bodies have stipulated condi-tions for embryo research that are considerably more restric-tive than policies on research with human cells or animal

embryos. For example, research must have important scien-tific or medical goals and may involve human embryos onlywhen the research cannot be conducted in any other way.Research projects should be restricted to the smallest num-ber of embryos that is feasible, and for the shortest possibletime period. Careful records and security must be utilized toensure that no embryos are diverted for unapproved pur-poses and that none are sold.Bringing Embryos into Existencefor ResearchOne of the most contentious issues in embryo ethics is thequestion of whether it is ever justifiable to bring humanembryos into existence specifically for research purposes.Many would argue that research use of surplus embryosremaining after the completion of infertility treatment isethically acceptable, since these embryos are destined to bedestroyed in any case. At the same time, they may hold thatthe development of embryos for research purposes, so-calledresearch embryos, is not morally justified.The development of embryos for research purposes hasbeen characterized as a novel practice that requires particularjustification. Referring to embryos created through nuclearcell transfer, the Presidents Council on Bioethics in 2002claimed that such research creation of embryos wouldconstitute crossing a major moral boundary (p. 132). Yetdecades of research on human IVF beginning in the 1930srequired investigation of various methods of laboratoryfertilization, followed by study of cleaving fertilized eggs todetermine their normality before transfer to a woman waseven considered (Soupart and Strong; Edwards and Steptoe).Commentators agree that there is no ontological orintrinsic distinction between surplus embryos remainingafter infertility treatment and research embryos developedspecifically for study. Arguments that support a moraldistinction must identify other morally relevant factors. Theconcept of respect is often invoked, as is the notion of intent.Respect for the special status of the embryo seems torequire that embryos be treated as entities of intrinsic value.When embryos are created purely for research purposes, theybecome instruments for purposes that have nothing to dowith the embryos themselves. In Kantian terms, the embryosare used solely as means for the welfare of others rather thanas ends in themselves. The practice of creating researchembryos thus results in treating embryos as commodities,equivalent to mere cells or tissues.In contrast, the intent to procreate justifies the develop-ment of embryos in the laboratory. Even when a largenumber of eggs is fertilized in an IVF procedure, eachfertilized egg has an equal chance of being transferred to awoman and developing into a human being. Thus eachzygote is equally respected for its procreative potential.It is only because some of the embryos cannot betransferred (because of the decision of the progenitors, orbecause there simply are too many of them) that theybecome surplus embryos and are destined for destruction. Itis arguably permissible to derive some good from the inevita-ble destruction of these embryos by using them in research.In doing so, one may be said to be choosing the lesser evil.These arguments have been countered by a number ofconsiderations.It may be true that respect for the special status of thehuman embryo requires that it be treated differently frommere human tissue. But the concept of respect is vague andundetermined, so that a wide range of concrete interpreta-tions is plausible. The claim that respect precludes allcreation of research embryos gives heavy weight to oneinterpretation of the concept at the expense of any counter-vailing considerations. Research projects that include thedevelopment of embryos may promise significant benefitsfor relieving the suffering of living human beings. Thesebenefits could outweigh a particular interpretation of respect.While procreative intent may justify the creation ofembryos in the laboratory, it is plausible that other sorts ofpurposes could provide equally valid justifications. Thetreatment of infertility, an elective medical procedure, mayeven hold lesser moral significance than the development ofcures for life-threatening or significantly disabling diseasesand trauma outcomes. Hence such goals may also justify thecreation of embryos.Moreover, surplus embryos do not appear purely bychance. Clinicians frequently make a decision to fertilizelarge numbers of eggs in order to optimize the chances ofestablishing a pregnancy. The initial intent is not to giveevery zygote the opportunity for implantation, but to achieveone or more pregnancies and births, as desired by theprogenitors. A later decision to direct unused embryos toresearch cannot be justified by the principle of the lesser evil,since the existence of surplus embryos should have beenanticipated. This situation was deliberately caused and couldhave been avoided. Thus it is invalid to invoke the principleof the lesser evil to justify use of surplus embryos in research,while maintaining that any creation of research embryos isprohibited.ParthenogenesisA potentially non-controversial process for developing morulasand blastocysts for research is the activation of oocytes

without use of sperm or transfer of somatic cell nuclei. Suchactivation can be achieved through electrostimulation orchemicals in a process called parthenogenesis. The resultingcleaving eggs, called parthenotes, may develop much likenormal embryos at least to the blastocyst stage. Although nohuman parthenotes have progressed this far, in February2002 scientists announced that they had developed monkeyparthenote blastocysts and established stable stem cell linesfrom them (Cibelli, et al.).Scientists believe there is a profound and intrinsicbiological barrier that prevents mammalian parthenotesfrom developing to advanced fetal stages (Human EmbryoResearch Panel, p. 20). On this assumption, parthenogenicmorulas or blastocysts lack the intrinsic potential to becomehuman beings. If this potential is a defining aspect of thehuman embryo and the basis for its special moral status, thenhuman parthenotes are not human embryos and should notarouse the same sorts of moral concerns. Thus they may offeran attractive alternative for research.CAROL A. TAUERSEEALSO:Abortion:MedicalPerspectives;Children:Healthcareand Research Issues; Cloning; Feminism; Fetal Research;Infants; Infanticide; Maternal-Fetal Relationship; MoralStatus; Reproductive Technologies: Ethical Issues; ResearchPolicy: Risk and Vulnerable Groups; Research, Unethical;and other Embryo and Fetus subentriesBIBLIOGRAPHYAnnas, George J.; Caplan, Arthur; and Elias, Sherman. 1996.The Politics of Human-Embryo ResearchAvoiding EthicalGridlock. New England Journal of Medicine 334: 1329-1332.Ashley, Benedict. 1976. A Critique of the Theory of DelayedHominization. In An Ethical Evaluation ofFetal Experimenta-tion: An Interdisciplinary Study, ed. Donald G. McCarthy andAlbert S. Moraczewski. St. Louis, MO: Pope John XXIIIMedical-Moral Research and Education Center.Ashley, Benedict, and Moraczewski, Albert. 2001. Cloning,Aquinas, and the Embryonic Person. 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Survey on the National Regulations inthe European Union Regarding Research on Human Embryos.Available from .Hatch, Orrin G. 2001. Testimony Before the Senate Appropria-tions Committee Subcommittee on Labor-HHS-Stem CellResearch, July 18. Available from .Howard Hughes Medical Institute. 2002. A Global Struggle toDeal with Human ES Cells. Sidebar in Are Stem Cells theAnswer? Available from .Manier, Jeremy. U.S. Quietly OKs Fetal Stem Cell Work;Bush Allows Funding Despite Federal Limits on EmbryoWork. Chicago Tribune, July 7, 2002. Available from.

Osborn, Andrew. MEPs Vote Against Stem Cell Research. TheGuardian April 11, 2003. Available from .Presidents Council on Bioethics. 2002. Human Cloning andHuman Dignity: An Ethical Inquiry. Available from.United Kingdom. Human Fertilisation and Embryology Act1990 (amended 2001.) Available from .U.S. Public Law 103-43. 1993. The NIH Revitalization Act of1993. Part IIResearch on Transplantation of Fetal Tissue.Available from .III. STEM CELL RESEARCH ANDTHERAPYIn this entry we review the ethical and legal issues that arisein the context of stem cell research and therapy. Stem cellshave attracted both immense scientific interest and equalethical and legal concern because of their capacity to spe-cialize and become virtually any part of the organism intowhich they are introduced. Thus if introduced into the brainthey become brain cells, if into the cardiovascular systemthey become cells of that type and so on. They also appear tobe able to trigger cell regeneration and colonize damagedtissue effecting repair in situ. Thus if such cells are madecompatible with the genome of a host using cloning tech-niques they could in principle repair and regenerate dam-aged tissue and halt or even cure many diseases. This holdsout both great promise and causes great unease in equalmeasure. Here we examine both the scientific promise andthe extent to which ethical and legal safeguards may beappropriate.Ethical IssuesThe ethical aspects of human stem cell research raise a widevariety of important and controversial issues. Many of theseissues have to do with the different sources from which stemcells may be obtained. Stem cells are at present obtainedfrom adults, umbilical cord blood, and fetal and embryonictissue. Although there are widely differing views regardingthe ethics of sourcing stem cells in these ways, there is generalconsensus that embryos are the best source of stem cells fortherapeutic purposesa consensus that may of course changeas the science develops. If spare embryos or aborted fetusesmay be used as sources for stem cells, there is a furtherquestion: Should embryos or fetuses be deliberately pro-duced in order to be sources of stem cells, whether or notthey are also intended to survive stem cell harvesting andgrow into healthy adults?The European Group on Ethics in Science and NewTechnologies, which advises the European Commission, hashighlighted the womens rights issues involved in stem cellresearch. It is particularly worth bearing in mind thatwomen, as the most proximate sources of embryonic andfetal material and hence also of cord blood, may be underspecial pressures and indeed risks if these are to be thesources of stem cells.The issue of free and informed consent, both of donorsand recipients, raises special problems. Because embryos andfetuses can hardly consent to their role in sourcing stem cells,the question of who may give consent for the use of fetal orembryonic material is important, particularly because theusual basis for parental consent is hardly appropriate. Thisbasis involves a judgment about what is in the best interestsof the individual, and because, in most cases, the individualin question will not survive, the test is irrelevant (Harris,2002a). Competent risk-benefit assessment is vital, andparticular attention needs to be paid to appropriate ethicalstandards in the conduct of research on human subjects.Other issues concern the anonymity of the donors, thesecurity and safety of cell banks, and the confidentiality andprivacy of the genetic information and the tissue the bankscontain. Finally, there are issues of remuneration for thosetaking part and of the transport and security of human tissueand genetic material and information across borders bothwithin the European Union (EU) and worldwide. Whilethese issues are important, they are well understood inbiomedical ethics, and with the exception of the issue ofconsent, they do not raise special issues in connection withstem cell research and therapy (U.K. Human GeneticsCommission).Before considering the ethics of such use in detail, it isimportant to first explore the possible therapeutic andresearch uses of stem cells and also the imperatives forresearch and therapy.WHY EMBRYONIC STEM CELLS? Embryonic stem cellswere first grown in culture in February 1998 by James A.Thomson of the University of Wisconsin. In November ofthat year Thomson and his colleagues announced in thejournal Science that such human embryonic stem cellsformed a wide variety of recognizable tissues when trans-planted into mice. Roger A. Pedersen, writing in 1999,noted potential applications of these stem cells:Research on embryonic stem cells will ultimatelylead to techniques for generating cells that can beemployed in therapies, not just for heart attacks,but for many conditions in which tissue is damaged.If it were possible to control the differentiation ofhuman embryonic stem cells in culture the result-ing cells could potentially help repair damage

caused by congestive heart failure, Parkinsonsdisease, diabetes, and other afflictions. They couldprove especially valuable for treating conditionsaffecting the heart and the islets of the pancreas,which retain few or no stem cells in an adult and socannot renew themselves naturally.Stem cells, then, might eventually enable us to growtailor-made human organs. Furthermore, using cloningtechnology of the type that produced Dolly the sheep, theseorgans could be made individually compatible with theirdesignated recipients. In addition to tailor-made organs orparts of organs, such as heart valves, it may be possible to useembryonic stem cells to colonize damaged parts of the body,including the brain, and to promote the repair and regrowthof damaged tissue. These possibilities have long been theo-retically understood, but it is only now with the isolation ofhuman embryonic stem cells that their benefits are beingseriously considered.Stem cells for therapy. It is difficult to estimate howmany people might benefit from the products of stem cellresearch should it be permitted and prove fruitful. Mostsources agree that the most proximate use of human embry-onic stem cell therapy would for Parkinsons disease, acommon neurological disease that has a disastrous effect onthe quality of life of those afflicted with it. In the UnitedKingdom around 120,000 individuals have Parkinsons, andthe Parkinsons Disease Foundation estimates that the dis-ease affects between 1 million and 1.5 million Americans.Another source speculates that the true prevalence ofidiopathic Parkinsons disease in London may be around200 per 100,000 (Schrag, Ben-Shlomo, and Quinn). Untoldhuman misery and suffering could be stemmed if Parkinsonsdisease became treatable. If treatments become available forcongestive heart failure and diabetes, for example, and if, asmany believe, tailor-made transplant organs will eventuallybe possible, then literally millions of people worldwide willbe treated using stem cell therapy.When a possible new therapy holds out promise ofdramatic cures, caution is of course advised, if only todampen false hopes of an early treatment. For the sake of allthose awaiting therapy, however, it is equally important topursue the research that might lead to therapy with all vigor.To fail to do so would be to deny people who might benefitthe possibility of therapy.ImmortalityFinally we should note the possibility of therapies thatwould extend life, perhaps even to the point at whichhumans might become in some sense immortal. This,albeit futuristic dimension of stem cell research raises impor-tant issues that are worth serious consideration. Manyscientists now believe that death is not inevitable that thatthe process whereby cells seem to be programmed to age anddie is a contingent accident of human development whichcan in principle and perhaps in fact be reversed and part ofthat reversal may flow from the regenerative power of stemcells. Immortality has been discussed at length elsewhere butwe should, before turning to the ethics of stem cell researchand therapy note one important possible consequence of lifeextending procedures.Human Evolution and Species ProtectionHuman Embryonic Stem Cell research in general, but theimmortalizing properties of such research in particular raisesanother acute question. If we become substantially longerlived and healthier, and certainly if we transformed ourselvesfrom mortals into immortals we would have changedour fundamental nature. One of the common definingcharacteristics of a human being is our mortality. Indeed inEnglish we are mortalspersons; not immortals orGods, demi-gods or devils. Is there then any moral reason tostay as we are simply because it is as we are? Is theresomething sacrosanct about the human life form? Do wehave moral reasons against further evolution whether it isnatural Darwinian evolution, or evolution determined byconscious choice?One choice that may confront us is as to whether or notto attempt treatments that might enhance human function-ing, so-called enhancement therapies. For example it maybe that because of their regenerative capacities stem cellsinserted into the brain to repair damage might in a normalbrain have the effect of enhancing brain function. Again itwould be difficult if the therapies are proved safe in the caseof brain damaged patients to resist requests for their use asenhancement therapies. What after all could be unethicalabout improving brain function? We dont consider itunethical to choose schools on the basis of their (admittedlydoubtful) claims to achieve this, why would a more efficientmethod seem problematic?We should not of course attempt to change humannature for the worse and we must be very sure that in makingany modifications we would in fact be changing it for thebetter, and that we can do so safely, without unwanted side-effects. However if we could change the genome of humanbeings, say by adding a new manufactured and syntheticgene sequence which would protect us from most majordiseases and allow us to live on average twenty five per centlonger with a healthy life throughout our allotted time,

many would want to benefit from this. In high-incomecountries human beings now do live on average twenty fiveper cent longer than they did 100 years ago and this is usuallycited as an unmitigated advantage of progress. The point issometimes made that so long as humans continued to beable to procreate after any modifications, which changed ournature, we would still be, in the biological sense, members ofthe same species. But, the point is not whether we remainmembers of the same species in some narrow biological sensebut whether we have changed our nature and perhaps with itour conception of normal species functioning.THE ETHICS OF STEM CELL RESEARCH. Stem cell researchis of ethical significance for three major reasons:1. It will for the foreseeable future involve the use andsacrifice of human embryos.2. Because of the regenerative properties of stem cells,stem cell therapy may always be more thantherapeuticit may involve the enhancement ofhuman functioning and indeed the extension of thehuman lifespan.3. So-called therapeutic cloning, the use of cell nuclearreplacement to make the stem cells clones of thegenome of their intended recipient, involves thecreation of cloned pluripotent (cells that have thepower to become almost any part of the re-sulting organismhence pluri-potent)and possiblytotipotent cells (cells which have the power tobecome any part of the resulting organism includingthe whole organism), which some people findobjectionable.In other venues, John Harris has discussed in detail theethics of genetic enhancement (Harris, 1992, 1998a) andthe ethics of cloning (Harris, 1997, 1998b, 1999b). Thefocus of this entry, however, is on objections to the use ofembryos and fetuses as sources of stem cells.Because aborted fetuses and preimplantation embryosare currently the most promising sources of stem cells forresearch and therapeutic purposes, the recovery and use ofstem cells for current practical purposes seems to turncrucially on the moral status of the embryo and the fetus.There have, however, been a number of developments thatshow promise for the recovery and use of adult stem cells. Itwas reported in 2002 that Catherine Verfaillie and her groupat the University of Minnesota had successful isolated adultstem cells from bone marrow and that these seemed to havepluripotent properties (capable of development in manyways but not in all ways and not capable of becoming a newseparate creature), like most human embryonic stem cellshave. Simultaneously, Nature Online published a paper fromRon McKay at the U.S. National Institutes of Healthshowing the promise of embryo-derived cells in the treat-ment of Parkinsons disease.Such findings indicate the importance of pursuing bothlines of research in parallel. The dangers of abjuring embryoresearch in the hope that adult stem cells will be found to dothe job adequately is highly dangerous and problematic for anumber of reasons. First, it is not yet known whether adultcells will prove as good as embryonic cells for therapeuticpurposes; there is simply much more accumulated dataabout and much more therapeutic promise for embryonicstem cells. Second, it might turn out that adult cells will begood for some therapeutic purposes and embryonic stemcells for others. Third, whereas scientists have already dis-covered that virtually any gene in embryonic stem cells canbe modified or replaced, this has not yet been established tohold for adult stem cells. Finally, it would be an irresponsiblegamble with human lives to back one source of cells ratherthan another and to make people wait and possibly die whilewhat is still the less favored source of stem cells is furtherdeveloped. This means that the ethics of embryonic stemcells is still a vital and pressing problem and cannot for theforeseeable future be bypassed by a concentration on adultstem cells.RESOLVING THE ETHICS OF RECOVERING STEM CELLSFROM EMBRYOS. There are three more or less contentiousways of resolving the question of whether it is ethicallypermissible to use the embryo or the fetus as a source ofmaterial, including stem cells, for research and therapy. Thethree methods involve: (1) solving the vexing question of themoral status of the embryo; (2) invoking the principle ofwaste avoidance; and (3) showing that those who profess toaccord full moral status to the embryo either cannot consis-tently do so or do not in fact believe (despite what theyprofess) that it has that status. Regarding the first of these, itis difficult to determine whether there will ever be suffi-ciently convincing arguments available for this question tobe finally resolved in the sense of securing the agreement ofall rational beings to a particular view of the matter (Harris,1985, 1999a). Putting aside this contentious issue, then, theother two issues will be discussed below.The principle of waste avoidance. This widely sharedprinciple states th