Numerous researchers tout the potential therapeutic benefits from human embryonic stem cells. Critics object to the fact that, in order to obtain stem cells, the embryos must be destroyed. This article presents an overview of the conflicting ethical arguments in favor of and against embryonic stem cell research.

Basic Scientific Facts
The inner cell mass of the human blastocyst consists of undifferentiated cells known as stem cells. These cells are pluripotent, that is, they have the potential to develop into any type of human tissue. The objective of embryonic stem cell research is to extract these cells and coax them into developing in such a way that they can be used to repair or replace damaged tissues and organs. In the course of extraction, the blastocyst is destroyed. (Technically, stem cells are extracted from blastocysts rather than from embryos, since the term "embryo" applies to a later stage of development, but in the debate over stem cell research, the term "embryonic stem cells" seems to be preferred.)

Some commentators, including a few bioethicists, believe that blastocysts are persons with full rights of personhood. Indeed, others believe that personhood begins at the moment of conception, when the egg is fertilized by the sperm, either naturally or through in vitro fertilization.

Kant's Categorical Imperative
There are two major schools of thought in moral philosophy - deontological and consequentialist. The deontological approach is exemplified by Immanuel Kant's principle of the Categorical Imperative, which says that persons must be treated as ends rather than as means. This leads to the belief that individuals fhave certain inalienable rights, as embodied in the famous statement in the Declaration of Independence that all people are "endowed by their Creator with certain unalienable [sic] rights, that among these are life, liberty and the pursuit of happiness." In practice, this means that a person's life cannot be sacrificed to achieve some greater good. (Among other things, this raises an interesting question about the morality of conscription during wartime.)
The View That Blastocysts Are Persons
Are human blastocysts covered by the Categorical Imperative? Do they have what ethicists call "rights of personhood"? Put simply, are they "persons"?

Some commentators, including a few bioethicists, believe that blastocysts are persons with full rights of personhood. Indeed, others believe that personhood begins at the moment of conception, when the egg is fertilized by the sperm, either naturally or through in vitro fertilization.

For example, Richard Doerflinger, Deputy Director of the Secretariat for Pro-Life Activities, United States Conference of Catholic Bishops, testified before Congress in 2004: Every human life, from the first moment of existence until natural death, deserves our respect and protection. Human life has intrinsic dignity, not only a relative or instrumental value; thus every living member of the human species, including the human embryo, must be treated with the respect due to a human person. [emphasis in original]

Edmund Pellegrino, M.D., Professor Emeritus of Medicine and Medical Ethics at the Center for Clinical Medical Ethics at Georgetown University, and the new chair (2005) of President Bush's Council on Bioethics, similarly told President Clinton's National Bioethics Advisory Committee:

In the Roman Catholic view [which Pellegrino shares], human life is a continuum from the one cell stage to death. At every stage, human life has dignity and merits protection. Upon conception, the biological and ontological individuality of a human being is established. Human development unfolds in an orderly way, and each stage of that development must be treated as an end in itself, not as a means to other ends, however useful they might be to others.

If blastocysts are "persons," then four questions arise. First, is it ethical to create blastocysts solely for the purpose of destroying them in order to obtain stem cells? Those who subscribe to the deontological way of thinking and who regard blastocysts as persons clearly say "no."

The second question that arises if blastocysts are considered persons concerns the fact that, during the process of in vitro fertilization (IVF), many extra embryos are created that will not be implanted into the uterus and allowed to mature.

Is it ethical to destroy these so-called "spare embryos" to obtain stem cells? In a 1999 report, President Clinton's bioethics commission, called the National Bioethics Advisory Commission (NBAC), said yes. (For the commission's full report, see

This position might be justified on the basis that, having accepted the practice of IVF, society has approved the inherent practice of creating spare embryos that will never be born and, therefore, these embryos can be destroyed to legitimate further research objectives. Moreover, deriving stem cells from spare embryos at least permits them to be used for some socially useful purpose. However, President Clinton's advisory commission did not regard blastocysts as full persons, but "a form of human life." Commentators who believe that blastocysts and spare embryos are persons reject the Clinton commission's reasoning. They argue that destroying spare embryos for research is still sacrificing human life and, therefore, that it violates Kant's Categorical Imperative. The United States Conference of Catholic Bishops, for instance, states: One wrong choice does not justify an additional wrong choice to kill them for research, much less a choice to make taxpayers support such destruction. The idea of experimenting on human beings because they may die anyway poses a grave threat to convicted prisoners, terminally ill patients, and others.

Moreover, they maintain that spare embryos will not necessarily be destroyed in the end; instead, they may be "adopted" or donated to other infertile couples. It is worth noting that President Clinton took no action on his bioethics commission's conclusion that it was ethical to obtain stem cells from spare embryos.

The third question is whether it is ethically permissible to use existing stem cell lines for research. These stem cell lines were created by destroying blastocysts; if blastocysts are persons, then destroying them to create stem cell lines might seem to violate the Categorical Imperative. Some deontological commentators argue that, since the blastocysts that gave rise to existing stem cell lines have been destroyed in the past and there is nothing that can be done to reverse this, it is ethically acceptable to use the resulting stem cells lines for research so long as no new cell lines are created. This is the position adopted by President Bush in 2001.

Others object that it is unethical to use existing stem cell lines because to do so represents an endorsement of the earlier act of destroying human life. As one Catholic bishop observed, "allowing for research with existing stem cell lines does not avoid moral complicity in the destruction of human life." A similar argument has been made against the use of scientific information obtained by Nazi doctors during the course of experiments on concentration camp inmates and other victims, even though some of the information obtained is still regarded as among the best data available on certain medical conditions such as hypothermia.

The final question if blastocysts are considered persons concerns the possibility that, in the future, a blastocyst-like entity could be deliberately fashioned so that it could never progress to being born. This might be accomplished by genetically knocking out the blastocyst's ability to form crucial extra-embryonic membranes or certain vital organ systems. Could such a non-viable, quasi-embryo be used for research? On the one hand, since the genetically modified blastocyst could never become a person, it may be said not to possess rights of personhood, including the right not to be destroyed for purposes of research. But some hard-line deontological advocateds take the view that deliberately creating non-viable blastocysts is itself morally impermissible.

The View That Blastocysts Are Not Persons
Some deontological commentators, while accepting the Categorical Imperative, believe that blastocysts are not persons with rights of personhood, but just a collection of undifferentiated mammalian cells. These commentators believe that personhood begins at a later stage of development: upon the development of the structure known as the "primitive streak" (around the 14th day after initial cell division); upon implantation in the uterine wall;when the fetus attains viability (the ability to survive outside the womb);or at birth.

Others adopt a sort of middle ground — they draw a distinction between using blastocysts left over from IVF that will never become human beings and the creation of embryos expressly for the purpose of destroying them to obtain stem cells, believing that only the former is ethically permissible.

Other ethicists who accept the Categorical Imperative but reject the notion that blastocysts are persons say that it is impossible to identify a specific point at which what starts out as a blastocyst becomes a person. Instead, they think of blastocysts as being near one end of a continuum, with full personhood at the other end. These proponents refer to blastocysts as "potential human life"; President Bush's Council on Bioethics calls them "nascent" or "developing" human life. (For the Council of Bioethics' report on stem cell research, see pcbe_final_version_monitoring_stem_cell_research.pdf.)

The notion that blastocysts reside on some sort of continuum of human life can lead to two opposite conclusions, however. One is that, although blastocysts are not full-fledged human beings, by virtue of residing on a continuum of human life, it would be wrong to destroy them for purposes of stem cell research. This was the position adopted by President Bush's Council on Bioethics, which echoed Kant's Categorical Imperative when it stated that "it is morally wrong to exploit and destroy developing human life, even for good reason." (The council ended up recommending establishing a four-year moratorium on both publicly- and privately-funded embryonic stem cell research to allow time for "further democratic deliberation.")

The Slippery Slope Argument
The other conclusion that might follow from the belief that blastocysts are on a continuum of human life is that, although we cannot pinpoint a position on this continuum at which full-fledged human life begins, it is somewhere beyond the stage of development of a blastocyst and, therefore, blastocysts can be destroyed for purposes of stem cell research. This approach leads to a so-called "slippery slope" problem, however: If we cannot tell when human life begins, but it is ethical to destroy blastocysts, what is to prevent us from destroying other entities along this continuum of human life, so long as we halt somewhere short of full-fledged human life, which lies at the other end of the spectrum? In other words, if we can injure or destroy blastocysts for research purposes, why not early-stage embryos, or later-stage embryos, or fetuses, or even children (since they are not fully-developed persons), and so on?

In moral discourse, there are only two ways to respond to a slippery-slope argument. One way is to concede that there is no stopping once we start down the slippery slope, and acknowledge that it is OK to harm or destroy entities short of full-fledged human life so long as it is in pursuit of a sufficiently compelling research goal. But this could appear to sanction a number of morally repellant practices, such as performing potentially dangerous medical experiments on persons with diminished mental or physical capacity because they are not fully functional human beings. The other way to deal with a slippery slope argument is to try to halt the slide down the slope by severing the slope at some point, maintaining that there is a certain point along the slope beyond which entities differ in morally significant ways. But it was the very inability to identify a point at which human biological entities can be treated differently from full-fledged persons that started us down the slippery slope to begin with.

In any event, most ethicists who reject the idea that blastocysts are persons still regard them as morally different from mouse blastocysts or other collections of living cells. As President Clinton's commission stated: "We believe that most Americans agree that human embryos should be respected as a form of human life." By virtue of their human connection, they support the belief that human blastocysts have symbolic value and, therefore, should not be treated cavalierly. For example, blastocysts (or their residuum after stem cells are removed) should be discarded with respect, rather than, say, flushed down a toilet. Most commentators who believe that human blastocysts, while not persons or entitled to the rights of personhood, deserve respect, take the view that it is respectful to conduct stem cell research using stem cells obtained by destroying the blastocysts, so long as the residual cellular material is disposed of properly.

The other great moral theory besides deontology is consequentialism. Rather than believing in moral absolutes such as Kant's Categorical Imperative, consequentialists hold that the rightness or wrongness of an action depends on its outcome: An action is ethical if it produces greater benefit than harm. This approach is familiar as cost/benefit analysis, which is frequently employed to determine the correctness of a medical or scientific course of behavior.

Under a consequentialist approach, society would identify and place a value on the costs of destroying blastocysts for purposes of stem cell research, including, for example, the risk of finding ourselves on a slippery slope if we cannot identify a clear developmental demarcation line for personhood. Society also has to carefully consider the potential benefits from embryonic stem cell research, such as whether it in fact will yield important medical treatments and, if so, how soon.

We also have to determine whether there are alternatives to obtaining stem cells from blastocysts, such as from adult stem cells that would yield similar benefits at lower cost, including lower ethical and symbolic costs. Another possibility is that stem cells can be obtained from blastocysts without destroying them. Once all this information is in hand, consequentialists believe that reasonable people can balance costs and benefits and reach an ethically acceptable conclusion about how to behave.

An example of this type of cost/benefit balancing is the approach taken by President Clinton's bioethics advisory commission, NBAC. NBAC declined to endorse a policy of creating blastocysts solely to be destroyed for research, on the basis that the symbolic and slippery-slope costs were too great, and the benefits too small in view of available alternatives, such as the use of blastocysts remaining after infertility treatments. At the same time, NBAC endorsed stem cell research involving discarded blastocysts only under conditions in which it is believed that the potential benefits would exceed the anticipated costs, namely, "when there is good reason to believe that this destruction is necessary to develop cures for life-threatening or severely debilitating diseases and when appropriate protections and oversight are in place in order to prevent abuse."

Who Should Decide?
A separate issue from the moral status of blastocysts is who should decide their fate. Some commentators believe that the persons who furnish the eggs and sperm that become the blastocyst should be permitted to decide whether or not the blastocyst can be used for stem cell research and, if so, under what conditions. The leading proponent of this view is Professor John Robertson. In a 2001 article, he points out that courts generally allow parents embarking on IVF to decide ahead of time what will happen to extra embryos, including decisions about whether they are to be stored, discarded, donated to another couple or used for research. Robertson recognizes, however, that complications arise if no prior agreement has been made, if couples divorce and one party changes his or her mind, or if donor gametes or surrogates are used. For example, who should decide what happens to extra embryos following IVF if the egg or sperm is donated: the gamete donor or the gestational mother? Interestingly, the National Institutes of Health in 1999 issued draft guidelines that would refuse to permit anyone to determine the fate of extra embryos in advance of the IVF procedure.

An alternative to allowing gamete donors or parents to decide what happens to spare embryos is to place decision-making responsibility on the physician, for example, the infertility doctor, or to create some sort of shared decision-making process in which physicians play a formal role. Given the importance of informed consent in medical ethics, it is unlikely that we would allow infertility doctors to conduct research on blastocysts against the express wishes of parents or donors. As a practical matter, therefore, if physicians were given a formal role in embryo decision-making, it is likely to consist of giving them a veto over decisions by parents or donors to donate blastocysts for research purposes. This might be justified on the basis that physicians should not be compelled to engage in behaviors that offend their conscience, similar to the principle that physicians should not be compelled to participate in abortions or physician-assisted suicide if they find these actions morally repugnant. But at the least, physicians should be required to notify potential donors and parents of their position in advance, so that the donors and patients can obtain services from physicians whose views are compatible with their own beliefs.

A third decision-making candidate is the stem cell researcher. Giving researchers primary decision-making authority might be rationalized on the basis that, given their medical and scientific expertise, they are in the best position to comprehend and balance the associated costs and benefits. But experience with research run amok, such as the infamous Tuskegee syphilis experiments, along with the strong opposition that some people have to embryonic stem cell research, makes it unlikely that stem cell researchers would be allowed to proceed completely on their own, without external limitations or guidance.

Another potential source of rules governing human embryonic stem cell research is the government. For example, President Bush has limited the types of embryo research that can be conducted with federal funds. In addition, the Food and Drug Administration has taken the position that blastocysts created through ooplasmic transfer (in which cellular material containing mitochondrial DNA is transferred from one egg to another in order to improve the chances of a successful pregnancy) are "biologics" over which the agency has regulatory authority under the Federal Food, Drug, and Cosmetic Act. On the plus side of allowing the government - that is, legislatures, executive officials and courts - to decide whether and under what circumstances embryonic stem cell research should be permitted is the fact that at least some of these decision-makers are elected or otherwise accountable to some degree to the public. But the danger is that they can reflect extreme, unpopular or minority viewpoints, and that their decisions, such as those by the Supreme Court, may be difficult to reverse.

Finally, we can defer to bioethicists to tell us what is right and wrong. They are in a position to think carefully through the opposing arguments and reach a reasoned conclusion. But bioethicists are self-proclaimed experts. They typically lack any special training or certification, and they may have hidden political or moral agendas.

Ultimately, we are all free to hold whatever views we wish on embryonic stem cell research. No one is suggesting that opponents of this research be forced to undergo it or to take advantage of whatever benefits it eventually might yield. The question instead is whether, given this opposition, public money should be spent on such research, and whether the opponents should be able to stop others from engaging in this research.