[Paleopsych] Walter Glannon: Genes, Embryos, and Future People

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Walter Glannon: Genes, Embryos, and Future People
Bioethics, 02699702, Jul98, Vol. 12, Issue 3

ABSTRACT: Testing embryonic cells for genetic abnormalities gives us the
capacity to predict whether and to what extent people will exist with
disease and disability. Moreover, the freezing of embryos for long
periods of time enables us to alter the length of a normal human
lifespan. After highlighting the shortcomings of somatic-cell gene
therapy and germ-line genetic alteration, I argue that the testing and
selective termination of genetically defective embryos is the only
medically and morally defensible way to prevent the existence of people
with severe disability, pain and suffering that make their lives not
worth living for them on the whole. In addition, I consider the possible
harmful effects on children born from frozen embryos after the deaths of
their biological parents, or when their parents are at an advanced age.
I also explore whether embryos have moral status and whether the
prospects for disease-preventing genetic alteration can justify
long-term cryopreservation of embryos.


Recent advances in reproductive biotechnology have given us the ability
to intervene in the process of human biological development from embryos
to people. One type of intervention is the testing of embryos for
genetic defects that cause disease, which enables us to choose between
allowing these embryos to result in disabled people or selectively
terminating their further development. Alternatively, in the foreseeable
future it may become possible to prevent disease by correcting a
mutation in embryonic cells or by inserting a normal gene into these
cells. It even may become possible to manipulate genes in such a way as
to enhance people's normal cognitive and physical functioning. Still
another form of intervention in the development of a human organism is
the freezing of an embryo in liquid nitrogen to postpone the birth of a
person who subsequently will come into existence from that embryo. All
of these interventions give us considerable control over how many people
will exist, when people will come into existence, and what sort of
people there will be.

I shall explore the moral implications of these technologies and argue
that we are morally required to intervene in the process of biological
development of human organisms by testing and selectively terminating
embryos with genetic defects that cause people to exist with severe
disease and disability. As a matter of beneficence, we have a duty to
prevent avoidable pain and suffering in the people we bring into
existence. As a matter of justice, we have a duty not to cause people to
exist with cognitive and physical disabilities that will limit their
opportunities for achieving a decent minimum level of lifetime
well-being. Each of these claims is motivated by the following moral
asymmetry thesis: we do not have a moral duty to bring people into
existence with good lives; but we do have a moral duty to prevent the
existence of people who would experience so much pain and suffering as
to make their lives not worth living for them on the whole.(n1)
Furthermore, in deciding whether to keep embryos frozen for long periods
of time, we have to consider the psychological impact on children born
from these embryos after the deaths of their biological parents, or when
their parents are at an advanced age. In addition, we must consider
whether we can justify keeping genetically defective embryos frozen
until the time when inserting a missing gene or correcting a mutant gene
become feasible practices.


The moral asymmetry thesis that I articulated above rests on three
notions. The first is the person-affecting principle, which says that a
person is benefited or harmed when her interests in what happens to her
are satisfied or defeated.(n2) Once a person exists, she has an interest
in not experiencing pain and suffering and thus can be harmed if she
experiences these over the course of her lifetime. The second notion is
the impersonal comparative principle, which says that, other things
being equal, it is worse to cause a person to exist if it would be
possible to cause a different, better-off, person to exist instead.(n3)
It involves a comparison, not between the existence and non-existence of
one person, but rather between two distinct lives of two distinct
people. On the impersonal comparative principle, we evaluate two
potential lives of two potential people who do not yet exist, while on
the person-affecting principle we evaluate the life of one person who
already exists. Yet we can appeal to both principles to support the
claim that we are morally required to prevent the existence of people
with lives that on balance are not worth living. That is, we prevent
harm to the individuals we cause to exist by fulfilling their interest
in not having to experience pain and suffering, and we avoid adding to
the total amount of suffering in the world.(n4) The third notion on
which the moral asymmetry thesis rests is the metaphysical relation
between embryos and persons.

'Person' is a psychological concept, while 'human organism' is a
biological concept. A human organism, in the form of a single-celled
zygote, begins to exist at around the time of conception, when male and
female gametes fuse.(n5) Thereafterr, the zygote develops into a
multi-celled embryo, a presentient fetus, a sentient fetus, and then the
body and brain of a person. The zygote, embryo, fetus, and person are
distinct but biologically related stages in the development of a human
organism. Up to about 14 days after fertilization there is the
possibility of monozygotic twinning of the fused gametes. When it
occurs, twinning causes two genetically identical but numerically
distinct individual organisms to exist from the original zygote, and
these subsequently develop into two distinct persons with distinct
psychological properties. A person begins to exist when the fetal stage
of the organism develops the structure and function of the brain
necessary to generate and support consciousness and mental life. This is
when the fetus becomes sentient, at around 23-24 weeks of gestation.
Because the structure and function of the organism's brain which
generate and support the psychological properties essential to
personhood develop gradually, persons come into existence gradually. The
zygotic, embryonic, and presentient fetal stages of the organism are
related to the person who develops from them to the extent that they all
have the same DNA in their cells and that the psychological properties
of the person causally depend on the biological properties of the
organism. But because a person's essential psychological properties are
distinct from, and emerge later than, the biological properties that
define these other stages in the development of an organism, a person is
neither identical with any one of these stages nor with the organism
itself.(n6) The embryo or presentient fetus is a potential person, not
in the sense that it becomes a person, which implies numerical identity,
but only in the sense that it has the potential to develop the
biological structures and functions necessary to generate the
consciousness and mental life constitutive of personhood.(n7)

The metaphysical distinction between human organisms and persons has
significant implications for the manipulation of genes in embryonic
cells. The manipulation of one or more genes in these cells would not
disrupt the identity of the organism, provided that its basic structure
and function remained intact. Yet it would determine the identity of a
different person. For, as Robert Elliot has pointed out, even slight
changes to the biological properties of an organism at the zygotic or
embryonic stage would cause different psychological properties to
develop and thus select between which of a number of different people
would come into existence.(n8) However, once an embryo has developed
into a child with consciousness and mental life, genetic manipulation of
its body's cells is more likely to be identity-preserving of personhood
than identity-determining, since it already has developed a set of
psychological properties. If this is correct, then the earlier genetic
manipulation occurs in the development of a human organism, the more
likely it is to determine that distinct people come into existence from

On the plausible assumptions that only beings with interests can be
harmed by the defeat of those interests, that having interests
presupposes sentience, and that only late-stage fetuses and persons are
sentient, it is morally permissible to terminate a human organism at an
early stage of development. The termination affects no one who has
interests. One might object that having interests does not presuppose
sentience. For example, it may be said that future people, who do not
yet exist and are not sentient, have an interest not to live in a
polluted environment.(n9) But the core concept at issue here is harm,
and harm consists in the defeat of particular interests of identifiable
persons who already exist and can experience the defeat of these
interests. Terminating the development of a human organism at the
embryonic stage does not kill a person but only prevents a person from
coming into existence. There is no one who could be harmed because there
is no identifiable individual with particular interests who exists at
that time.

Similar reasoning underwrites the claims that we do not have a moral
duty to bring people into existence, and that bringing someone into
existence by itself does not benefit her, however good her life may be.
We cannot say that being caused to exist is better for a person than she
otherwise would have been, since otherwise she would not have existed.
Put differently, there is no one who is caused to exist; rather, we make
it the case that someone exists. Derek Parfit argues that the relation
between existence and non-existence does not meet the 'Full Comparative
Requirement', which says that we benefit someone only if we do what will
be better for him.(n10) While causing someone to exist may be good for
him, it cannot make him better off, since nonexistence is morally
neutral and therefore neither good nor bad. We do not have a moral duty
to benefit persons by bringing them into existence, because we benefit
persons by satisfying their interests, and it is difficult to see how
non-existing persons could have an interest in being caused to exist.

However, while it is morally neutral to cause a person to exist with a
life that on balance is good, it is morally wrong to bring a person into
existence with a life that on balance is bad because of severe pain and
suffering. For in this case there is someone who actually experiences
pain and suffering and who is harmed by being caused to exist in such a
condition. And since it is not morally neutral but wrong, we have a
moral duty to prevent the existence of a person who would have such a
life. Yet there is an air of paradox about the idea that, although we do
not benefit people by bringing them into existence with lives that are
good on the whole, we harm people by causing them to exist with
restricted lives that are bad on the whole.(n11) Presumably, we harm
someone by causing them to exist with a disability because we make them
worse off than they otherwise would have been. But if they did not exist
with the disability, then they would not have existed at all. Insofar as
a person's life is worth living on the whole, being brought into
existence with a cognitive or physical disability cannot be worse for
her, because if we terminated the development of the embryo containing
the gene that caused the disability, then she would not exist. This is a
variant of what Parfit has called the 'Non-Identity Problem'.(n12)

Jonathan Glover has devised a strategy to sidestep the Non-Identity
Problem. Instead of trying to draw a comparison between the existence
and non-existence of one identifiable individual, Glover maintains that
the relevant comparison is between two distinct lives of two distinct
people. It is 'impersonal' in the sense that 'harm can be done even
though identifiable people are no worse off than they otherwise would
have been'.(n13) Glover uses the following example to illustrate the
impersonal comparative principle. Imagine that a factory emits a
chemical that causes babies to be born blind. On the Non-Identity
Problem, they are not made worse off than they otherwise would have
been, since their lives are worth living and otherwise they would not
have existed. But 'what we should say here is, not that the pollution
made the blind children worse off than they would have been otherwise,
but instead that their condition is worse than the condition of the
other children who would have been born in the absence of the
pollution.'(n14) The choice is between bringing different people into
existence, while retaining the same number of people who will
exist.(n15) Both person-affecting and impersonal harm principles give us
reasons to bring a normal child into existence rather than a diseased or
disabled one. We prevent actual people from experiencing pain and
suffering and thereby avoid defeating their interest in having healthy
lives, and we avoid adding to the total amount of suffering in the

In some genetically caused diseases, severe cognitive and physical
disability may make people's lives so restricted that they are not worth
living. By definition, these lives fall outside the scope of the
Non-Identity Problem. When we can predict that a disease would involve
so much disability, pain, and suffering as to make life not worth living
on the whole, we are morally required to prevent the existence of people
who would have the disease. Or, if we do cause people to exist with such
a disease, then we are morally required to either cure them or alleviate
the severity of their symptoms, insofar as we are able. The first
scenario that I described pertains to the impersonal sense of harm and
potential persons, while the second pertains to the personal sense of
harm and actual persons. One suggests genetic testing and selective
termination of defective embryos as the appropriate strategy to prevent
harm. The other suggests that the appropriate strategy to prevent or
compensate for harm would be gene therapy or some other form of genetic
alteration. A person is a further stage of development of the same human
organism of which the embryo is an earlier stage. In this sense, embryos
are potential persons, and failing to terminate a genetically defective
embryo can cause harm by allowing it to develop into a diseased or
disabled person.(n16) Because gene therapy is not yet feasible for most
diseases, genetic testing and selective termination of genetically
defective embryos appears to be the only medically effective and morally
defensible way to prevent the sort of harm at issue. Before defending
this claim, however, we should examine the different forms of genetic
intervention and assess their medical and moral significance.


There are three basic types of genetic alteration. (n17) Gene therapy
consists in the correction or addition of genes in the somatic (body)
cells of a person to treat a disease the person already has, where the
aim of treatment is to cure the disease or alleviate its symptoms. By
contrast, genetic alteration of germ cells (gametes; sperm and egg) at
the zygotic or embryonic stage of the human organism prevents diseased
persons from coming into existence. It is therefore mistaken to call
this form of genetic manipulation 'therapy,' because when the gametes
are altered, there are no existing persons who might benefit from this
act.(n18) 'Therapy' implies that there is a disease to be treated or
cured, and it is not zygotes or embryos but rather persons or late-term
fetuses who are diseased. Defective genes in embryonic cells may be the
causes of diseases, but the diseases do not manifest themselves until
the organism has developed into a fetus or person. Unlike somatic-cell
gene therapy, which preserves the identity of already existing persons
who are treated, germ-line genetic alteration determines the identity of
the person who would come into existence from the embryo in which a
defective gene is corrected or replaced by a normal one. The
intervention takes place before the process of cell differentiation and
the development of tissues and bodily organs has begun, and thus
determines that a biologically and psychologically distinct individual
will come into existence from the one who would have come into existence
from the same embryo had the defective gene not been corrected or
replaced. Genetic enhancement involves non-therapeutic alteration of
genes aimed at improving cognitive and physical functioning which
already are at or above the normal level for persons.

The three types of genetic alteration which I have mentioned are to be
distinguished further from selective termination of embryos after
genetic testing has revealed the presence of disease-causing genes, or
markers for these genes, in the cells of embryos. (n19) Like germ-line
genetic alteration, germ-line genetic testing and termination is not a
therapeutic but a preventive strategy designed to avoid the existence of
individuals who would be severely disabled and have restricted lives.
Let us now further explore the four types of genetic intervention at the
embryonic stage of development of a human organism.

Somatic-cell gene therapy is not yet feasible for treating the majority
of genetically caused diseases. This is because gene therapy is
primarily relevant to single-gene disorders, and chromosomal disorders
such as Down syndrome involve large segments of DNA which are not
amenable to treatment. Moreover, the single-gene disorders that might be
amenable to gene therapy are recessive rather than dominant disorders.
Recessive disorders, where a single copy of the normal gene is
sufficient for one to function within the normal cognitive and physical
range for persons, may be treatable because inserting one copy of a
normal gene into someone with a double dose of the defective gene may be
enough to raise that individual's functioning or health up to the normal
range. Dominant disorders, by contrast, result even when the affected
person has only a single copy of the defective gene. These disorders
might be prevented or cured by correcting the mutation within the gene.
Presently, however, it is not possible to correct a mutation but only to
insert an additional normal copy of a gene into cells, and therefore
only recessive disorders can be treated through genetic intervention.

In theory, a recessive disorder like cystic fibrosis (CF) could be
treated by inserting a normal gene into the relevant cells so that the
pancreas produced the necessary enzymes for food absorption, as well as
to ensure proper function of the glands in the lining of the bronchial
tubes. Similarly, in hemophiliacs, who are unable to produce normal
amounts of a factor necessary for blood clotting, the missing gene could
be delivered through injections. In practice, though, what has plagued
the efforts of gene therapy to cure people of diseases, or at least
effectively treat their symptoms, is the lack of suitable vectors to
deliver therapeutic genes into human cells and maintain them in working
order. Viral vectors have been the method used to date, specifically
adenoviruses and retroviruses, which slice copies of their genes
permanently into the chromosomes of the cells they enter. Yet this
method has been largely unsuccessful because the stripped-down viruses
that have been used do not provide a stable platform for the genes to
operate efficiently. Some of these viruses are not large enough to carry
a full human gene and its switches, while others may provoke an adverse
response by the immune system. Work on hemophiliacs, children with
severe combined immunodeficiency disease (SCID), and familial
hypercholesterolemia has shown some promise. But for the majority of
genetically based diseases, gene therapy is not yet an effective cure or

Germ-line genetic alteration initially may seem more attractive than
gene therapy. Manipulation or replacement of genetic abnormalities in
germ cells at the zygotic or embryonic stage after in vitro
fertilization (IVF) would correct a defect before it could manifest
itself as a disease in an existing person. This type of alteration would
affect the resulting cells in the process of differentiation and in turn
the germ line of the person who develops from the embryo. The altered
genes would then be passed on to future generations of the person's
offspring. But it is questionable whether germ-line genetic manipulation
would be desirable from an evolutionary perspective. Some degree of
genetic mutation is necessary for species to adapt to changing
environmental circumstances, and some genetic disorders confer benefits
on certain populations. For example, the gene for sickle-cell anemia
provides greater resistance to malaria. Altering a gene or genes at the
germ line to correct one disorder may only lead to other disorders. This
also raises the question of whether we have a duty to prevent passing on
unforeseeable consequences of germ-line alteration to future
generations, which is morally significant for two reasons. First, people
existing in the future might be adversely affected by a policy to which
they did not consent. Second, it would be extremely difficult to
determine whether the benefits of such a policy would outweigh its
harms, in which case it may be morally preferable to err on the side of
caution and prevent such a policy from being implemented. In sum, there
may be both medical and moral reasons against germ-line genetic

Genetic enhancement is a non-therapeutic form of genetic intervention
which aims to raise cognitive and physical capacities above the normal
range of functioning for persons. But to the extent that people's actual
cognitive and physical functioning enable them to achieve a decent
minimum level of well-being, there are no compelling medical or moral
reasons for genetic enhancement. Indeed, some would say that there are
compelling reasons for prohibiting it. Insofar as genetic enhancement
aimed at something over and above disease prevention and health
promotion, it would threaten to introduce a program of positive eugenics
which would unjustly discriminate against certain groups of people who
are moderately disabled and whose lives, though somewhat restricted, are
nonetheless worth living. I will return to the eugenics question in the
last part of the next section.

My analysis of the different forms of genetic alteration and the problem
of their feasibility supports my earlier claim that genetic testing and
selective termination of embryos with defective genes that cause people
to exist with severe pain and suffering is the only medically effective
and morally defensible way to prevent this state of affairs from
obtaining. It will be instructive to cite some specific diseases that
recommend such a preventive measure.


Present biotechnology allows us to test embryonic cells for genetic
abnormalities that lead directly to severe early-onset disorders, like
Tay-Sachs disease, Hurler syndrome, Lesch-Nyhan syndrome, and Canavan's
disease, as well as late-onset disorders like Huntington's disease.(n21)
We also can test embryos for genes that predispose people to chronic and
ultimately fatal conditions like coronary heart disease and cancer.
Genetic mutations play a causal role in many diseases by altering a
crucial enzyme or other protein. The alteration may occur in differing
degrees, depending on the extent of interaction between genes and the
environment. In the specific diseases I mentioned above, though,
environment plays little or no causal role in their occurrence. Either
the defective gene necessarily causes the disease, or else it has a very
high probability of causing it (95% with the Huntington's gene).

In Tay-Sachs, for instance, babies appear quite normal at birth. But in
the first year of life their nervous systems degenerate, and they
usually die by the time they reach 3 or 4. This disease is caused by the
presence of two copies of an abnormal gene, or mutant allele, at a
particular site on one of the 23 chromosome pairs. Tay-Sachs is an
autosomal recessive disorder, which effectively means that the child
inherits one mutant allele from each parent. Through the fusion of the
gametes in the zygote that develops into the embryo, fetus, and person,
the parents transmit the disease to their child.

Ideally, we would use gene therapy by inserting an additional normal
copy of the defective gene into the relevant cells and thus cure the
disease. But Tay-Sachs, like most recessive (and dominant) disorders,
has not proven amenable to therapy. Alternatively, we can test and
selectively terminate embryos with genes that cause this or other
severely disabling diseases, preventing these diseases by preventing the
existence of the people who would have them. This practice can be
justified on two grounds. Beneficence requires that we not harm people
by causing them to experience pain and suffering over the balance of
their lives. In addition, justice requires that we not deny severely
disabled people the same opportunities for achieving a good life as are
open to others who are healthy or have only moderate cognitive or
physical disabilities.(n22) Arguably, the justice requirement will apply
to only a small number of people, since the idea of equal opportunity
for a good life implies a certain number of years to undertake and
complete projects for a decent minimum level of wellbeing, and most
people with severe early-onset genetically caused diseases have
relatively short lifespans. Perhaps this is not the case with a disease
like CF, where people afflicted often live for 30 years or more. But I
do not believe that this genetically caused disease is so severely
disabling and painful that we can justifiably prevent the lives of the
persons who would have it. Considerations of justice matter; but what
matters more than ensuring equal opportunity for achieving a good life
is preventing avoidable severe pain and suffering that people actually
experience once they exist. These are what make lives not worth living
on the whole. Indeed, it is often the severe pain and suffering
associated with disabilities which preclude people from having the
opportunities to achieve a decent minimum level of lifetime well-being.

Testing of embryonic cells for genetic abnormalities may be done by
extracting cells from preimplantation IVF embryos. To produce
extracorporeal IVF embryos for this type of testing, fertility drugs
such as Clomid or Pergonal can be given to a woman to induce
superovulation and in turn produce a number of eggs that can be
recovered for fertilization with sperm. One advantage of producing
multiple embryos is that, if genetic abnormalities are detected in any
one of the embryos, then it can be selectively terminated and another,
normal, embryo can be implanted in the woman's uterus. This would enable
parents to have a normal child instead of a disabled one and to avoid
any burdens that such a child might have on them or, if they have other
children, the rest of the family. Significantly, the capacity to produce
multiple IVF embryos is largely what grounds the impersonal harm
principle, since at least two embryos must be available for a parent or
parents to choose to bring a normal child into existence instead of a
disabled one.

Another attractive feature of this method, as Robert Edwards explains,
is that 'identifying embryos with genetic abnormalities would offer an
alternative to amniocentesis during the second trimester of pregnancy,
and the 'abortion' in vitro of a defective preimplantation embryo . . .
would be infinitely preferable to abortion in vivo at twenty weeks of
pregnancy or thereabouts as the results of amniocentesis are
obtained'.(n23) Testing preimplantation IVF embryos for genetic
abnormalities would be preferable to testing fetal cells for these
abnormalities by amniocentesis or chorionic villus sampling because,
unlike these invasive procedures, it would not be painful to the
pregnant woman and would avoid certain medical risks. Specifically,
putting a needle into the uterus to extract cells from either the
amniotic fluid or embryonic membrane triggers a miscarriage once in
every 50 to 100 pregnancies. Moreover, villus sampling may cause limb
deformities in the fetus.

Terminating the development of one embryo and implanting a different
embryo would mean that the life of one potential person was not allowed
to become actual and that the life of a different potential person
became actual instead. Thesame number of people would exist, but they
would be different people. Yet whether one or a different potential
person is allowed to exist does not matter morally. Rather, what matters
morally is preventing avoidable pain and suffering that actual people
will have to experience. And to the extent that an embryo containing a
disease-causing gene will result in severe pain and suffering in the
person who develops from it, we are morally required to prevent the
disease, pain, and suffering by terminating the development of that
embryo. What must be emphasized, however, is that the moral requirement
to terminate embryos and thereby prevent certain people from coming into
existence pertains only to those people who would have severe, not just
moderately severe, diseases. Only severe diseases make people's lives
not worth living on the whole.

One consequence of not preventing genetically defective embryos from
resulting in severely diseased or disabled persons is that a child
caused to exist in such a condition could file a tort of wrongful life
against his parents.(n24) Or, if the child is cognitively or physically
unable to do so, a different person could file a tort on the child's
behalf. Suppose that a boy has Duchenne muscular dystrophy, a recessive
disorder traceable to a genetic defect on the X chromosome which
adversely affects the dystrophin protein. This defect causes muscles to
begin weakening at age 3 and subsequent respiratory failure, which gives
children afflicted with the disease an average life expectancy of 16-20
years. If the boy's mother knew that she was a carrier of the defect and
that there was a 50% chance of transmitting it to her son, was able to
abort the embryo containing the defect, yet allowed the child to be born
from that embryo, then the boy could claim that his parents acted in
reckless disregard of his welfare, wronged and harmed him, and
accordingly owe him compensation for causing him to exist with a
condition that defeats his right and interest in having a life that is
not severely restricted. The person-affecting principle would ground the
child's claim against his parents.

There would not be grounds for a tort of wrongful life, however, if the
child claimed that genetic intervention other than testing and
termination at the embryonic stage of development, such as adding a
normal copy of the dystrophin gene, would have made a significant
difference between the quality of life he actually experiences and what
he might have experienced otherwise. For at the time of the
intervention, there would not have been any identifiable individual to
be benefited or harmed. Genetic alteration at such an early stage of
development of the organism would have resulted in a completely
different set of biological and psychological properties that would have
belonged to a different person. So the child only could claim that the
wrong or harm was committed by not terminating the defective embryo from
which he developed, not by failing to add a normal copy of the gene.
Gene therapy involving somatic cells at an early age after birth also
would entail different subsequent biological and psychological
properties as the child's life unfolded. Arguably, however, these would
not be so radically different from the properties possessed before the
therapy that they would be of a different person, since presumably the
child who receives the therapy already has a fairly developed biological
and psychological life. Although some of his properties would have
changed, intuitively there would be enough biological and psychological
continuity before and after the therapy to say that the child cured of
CF or SCID by gene therapy would remain the same individual. If such a
child's parents had access to affordable gene therapy that could cure
his disease or treat the symptoms associated with it, but failed to seek
such treatment, then perhaps the child could claim that his parents
harmed or wronged him by defeating his interest in being cured of or
treated for a disease that was amenable to gene therapy. But to the
extent that the child already exists with a condition for which his
parents are not completely responsible, strictly speaking this case
would involve something other than the standard notion of wrongful life.

The cases that I have just discussed involve physical disability. More
difficult to assess would be gene therapy to correct severe cognitive
disability at a fairly early stage of a person's life. This could have a
significant effect on subsequent psychological properties that arguably
would be those of a different person from the one who underwent
cognitive gene therapy for the affected brain cells at an earlier time,
given that the brain generates and supports the consciousness and other
psychological properties necessary for personhood and personal identity
through time. The medical prospects for cognitive gene therapy are even
less promising than they are for physical gene therapy, and the moral
implications of such therapy are so complex that I cannot address them
adequately here. Nevertheless, cognitive and physical disability may
very well have different relative weights in determining personal
identity through time, as well as in determining whether or to what
extent people can be harmed.

I have claimed that the diseases that morally require us to prevent the
existence of people who would have them must be so severely disabling
that they make their lives not worth living on the whole. This is not
the case with moderately severe genetic disorders like Down syndrome,
where, although there is some cognitive and physical impairment, the
lives of people with this disorder can be fulfilling and thus very much
worth living. So there would be no moral grounds for preventing the
existence of people with Down syndrome. But there would be no moral
requirement to bring them into existence either, given that existence is
morally neutral and entails no requirement to cause people to exist with
good lives.

A further distinction must be drawn between early-onset genetic
disorders of the sort I have been discussing, which affect people from
birth or early childhood, and late-onset genetic disorders, like
Huntington's disease, which do not affect people until the adult stage
of their lives. The onset of symptoms in people afflicted with
Huntington's may range anywhere from age 30 to 50, and these include
progressive loss of muscle control and dementia. Generally, they die
within 15 years after onset. Prior to this time, they usually have
normal lives with comparatively high levels of cognitive and physical
functioning for a considerable number of years. In trying to determine
whether people's lives are worth living on the whole, we should do so by
evaluating the quality of their lives in terms of all the stages of
their lives. But the radical difference in cognitive and physical
functioning before and after the onset of symptoms in diseases like
Huntington's makes it difficult to assess overall quality of life for
the people who have them.

With severe adult-onset diseases, perhaps the most plausible way to
measure lifetime quality is to weigh the level of normal functioning per
year lived against the level of disability per year lived and arrive at
an average level of well-being for the person's entire lifespan.(n25) On
this view, the earlier the onset of symptoms in the person's life, the
longer the period of time between onset and death, and the more severe
the disability, pain, and suffering associated with the disease, the
stronger the reason will be for saying that the person's life is not
worth living on the whole. Correspondingly, there will be a stronger
reason for preventing that life by terminating the embryo with the gene
that causes the disease. Thus, for a person afflicted with the
degenerative physical and cognitive symptoms of Huntington's disease at
age 30, the severity of the pain and suffering he experiences in his
last 15 years may be bad enough to outweigh the normal functioning he
had in his first 30 years and average out to a level of lifetime
well-being which falls below the decent minimum. This in turn may lead
us to conclude that his life is not worth living on the whole for him
and that, if we could have foreseen this through genetic testing of the
embryo from which he developed, then we should have terminated the
embryo and thereby prevented him from existing.

Or consider a more controversial variant of the same case. Suppose that
genetic testing could predict that symptoms would not manifest
themselves until age 50. One might claim that the pain and suffering
caused by the disease in the last 10 or 15 years of the person's life
would be so severe as to outweigh the good 50 years and thus make the
person's average lifetime well-being fall below the decent minimum.
Although it would be difficult to sustain, here too there may be a
principled reason for terminating an embryo with the Huntington's gene.
It may weigh the decision in favor of preventing the existence of a
person who would have the disease over causing him to exist with a life
that has a wretched last stage. Alternatively, one could take the view
that, with adult-onset diseases, it is the victim's responsibility to
decide whether to go on living beyond a certain point. This is
consistent with the conviction that the value of a life is determined
subjectively by the person whose life it is. But whether this view were
to figure in any way in public policy would depend, among other things,
on the legal climate in which the afflicted person was living.(n26)

Pain and suffering in the last stage or years of a person's life must be
weighed against the achievements afforded by normal cognitive and
physical functioning in earlier stages. Fifty years of normal
functioning should be enough for a person to complete many of the
projects in his life plan and make for a life that is worth living. If
so, then the fact that a person loses his normal functioning at age 50
by itself is not enough to support the claim that on balance his life is
not worth living and that he should not have been allowed to come into
existence. Indeed, some people have lives of thirty years that are full
of achievements. A shorter life can be very well worth living. But if
the pain and suffering in one's last years are severe enough, and if the
number of these years is large enough, then this may weigh the decision
in favor of preventing the person from coming into existence. The
experience of severe pain and suffering, more so than what it implies
about limited opportunities for achievement, grounds the claims that a
person's life on balance is not worth living for him and that it is
morally wrong to cause a person to exist with such a life.

Two objections might be raised against the claim that people with severe
disease or disability should not be brought into existence. Disabilities
rights advocates might argue that intervention in the form of testing
and selectively terminating genetically defective embryos would reduce
the number of people with disabilities. Consequently, public support for
persons who already have disabilities would erode. It would lead to a
devaluation of the lives of the disabled and to discrimination against
them. To rebut this objection, we can appeal to Allen Buchanan's point
that 'it is not the people with disabilities which we devalue, it is the
disabilities'.(n27) Buchanan further says 'we devalue disabilities
because we value the opportunities and welfare of the people who have
them -- and it is because we value people, all people, that we care
about limitations on their welfare and opportunities. We also know that
disabilities, as such, diminish opportunities and welfare, even when
they are not so severe that the lives of those who have them are not
worth living'.(n28) The underlying rationale for this position is that
it is a matter of justice, not only beneficence, that we remove or
prevent limitations on an individual's opportunities for a decent life.
But the second passage cited from Buchanan leaves open the possibility
that it is morally permissible to terminate embryos with genetic defects
that would lead to people having lives with limited opportunities that
are nonetheless worth living. Against Buchanan, I believe that we should
terminate only those embryos with genetic defects that manifest
themselves in severe disabilities that make life on balance not worth

Still, we have to weigh the relative importance of cognitive and
physical functioning for different people in assessing quality of life.
Suppose it were discovered that the adult-onset motor neuron disease
amyelotrophic lateral sclerosis (ALS) had a genetic cause and that the
disease could be prevented only by terminating embryos whose cells
contained the defective gene. The case of the brilliant theoretical
physicist Stephen Hawking illustrates that a person can suffer from a
severe physical disability as a symptom of ALS for well over the balance
of his life yet maintain a high level of cognitive functioning which
makes life for him very much worth living. It would be difficult to
adduce reasons for preventing such a life from coming into existence,
despite the fact that ALS is a severely disabling disease. On the other
hand, for people who value physical functioning very highly (e.g.
athletes, dancers), severe physical disability may lead them to judge
that on balance their lives are not worth living, even if their normal
cognitive functioning remains intact. Granted, people can adapt their
preferences and life plans to adult-onset disabilities and the limited
opportunities they entail. But it is not so easy to do this if one has
to endure constant pain and suffering over a considerable period of
time. Furthermore, in the case of someone like Hawking, if the pain
associated with the physical disability were so severe that it adversely
affected his cognitive functioning, then we might consider whether he
would believe that his well-being was at a level high enough for him to
judge that his life was worth living.

A second objection to my view is that any form of genetic intervention
is motivated by the desire to improve the human species through
selection. This amounts to a program of positive eugenics, which would
lead to a repeat of the inhumane treatment of people and a violation of
their intrinsic worth which have occurred in recent history.(n29) To
this objection, we can respond by saying that the aim of any medically
and morally defensible form of genetic intervention should not be to
enhance people's genotype or phenotypic traits, but only to ensure that
the people we do cause to exist have normal, or close to normal,
cognitive and physical functioning over the balance of their lives. In
preventing the existence of people with severe disability, we are not
aiming to enhance or improve lives that already are, or would be, at a
decent minimum level of well-being, but only to ensure that the people
we do bring into existence will not fall well below this level. This
accords with the moral asymmetry thesis. We have no moral duty to bring
people into existence with good lives. But if we do bring people into
existence, we have a moral duty to ensure that their lives do not
contain so much pain and suffering as to be not worth living for them on
the whole.

The negative eugenics I am defending has affinities with what Philip
Kitcher calls 'utopian eugenics'.(n30) This involves a policy
guaranteeing that people have reproductive freedom in choosing which
embryos they allow to develop and subsequently the people they bring
into existence. Their choices must be free of any socially coercive
pressure to prevent people from existing for economic reasons or
perfectionist ideals. Provided that genetic testing and selective
termination of defective embryos are practiced in order to prevent
extreme pain and suffering in people, not to enhance their cognitive and
physical capacities above the normal range, and that reproductive
technologies like IVF and genetic testing are affordable and accessible
to all, utopian eugenics is a morally justifiable policy.


Another practice made possible by reproductive biotechnology is the
storing of frozen embryos in 'embryo banks' of liquid nitrogen. One
attractive feature of this type of cryopreservation is that a woman
could decide to preserve an embryo produced by IVF from her egg and a
man's sperm in such a bank in order to pursue a career and later have
the embryo implanted in her uterus for pregnancy and birth. Assuming
that long-term storage does not entail a risk of genetic mutation in
embryonic cells, she could undertake a later pregnancy without fear of
birth defects regardless of her age because the embryo fertilized at the
earlier time would be biologically optimal. Moreover, if genetic testing
determines that an embryo has a genetic abnormality that likely will
result in a severely diseased or disabled person, then storing multiple
IVF embryos gives parents the choice to terminate the defective embryo
and implant a normal one instead. In addition, cryopreservation of
embryos for an extended period of time may make any genetic mutations
they contain correctable by the insertion of normal copies of the
relevant genes, if such a technique becomes feasible in the near future.
This would determine the identity of the person brought into existence
free from disease, who would replace the diseased individual who would
have existed instead from the same embryo without the altered or
additional gene. But it is worth repeating that it is not whether
genetic alteration or therapy is identity-determining or
identity-preserving which is morally significant, but rather the sort of
experience the persons who are brought into existence will have.

There are reasons to be wary of freezing and storing embryos for long
periods of time, however. It is unknown whether this process might
entail genetic mutations in embryonic cells which might result in
disease and premature death in the individuals who come into existence
in this way. Also, IVF and cryopreservation of embryos make it possible
for a person resulting from such an embryo to have three distinct
mothers: (1) the genetic, or biological mother, whose gamete contributes
23 chromosomes to the embryo and determines many of the subsequent
biological and psychological properties of the child who develops from
the embryo; (2) the gestational mother, in whose uterus the embryo is
implanted and who gives birth to the child; and (3) the social mother
who raises and cares for the child. The social mother is perhaps the
most important of the three with respect to the child's interests, since
she is the one who cares for the child when it has the requisite
psychological properties for interests, rights, and a biographical self.
To the extent that only individuals with interests and rights can be
harmed, and these interests and rights can be affected directly by the
social mother, she can directly affect the welfare of the child. But the
relationship between a child and its biological parents can have a
significant psychological impact on the child as well.

If an embryo is frozen and not implanted until many years after
fertilization, then it is possible for a child to be born from that
embryo and come into existence after the deaths of its biological
parents. Even assuming that there are no known genetic abnormalities in
the embryo, the prospect of being born after the deaths of its
biological parents may have harmful effects on the child's psychological
identity, its sense of self. A mature self ordinarily will have a
relationship with its biological parents which involves more than mere
knowledge of who they are. There may be an even greater sense of harm to
a child resulting from an embryo stored for a considerable period of
time. Earlier, I said that storing embryos could allow a woman to pursue
a professional career before having a child. But suppose that a woman's
egg, fertilized when she was 30, is frozen and not implanted in her
still normally functioning uterus (or that of a surrogate mother) until
she is 60.(n31) She becomes pregnant and decides to bring the pregnancy
to term. The increasing likelihood of disease with age may mean that the
child or adolescent born from this pregnancy would have the burden of
caring for her mother or both parents before she was emotionally mature
enough to do so. It also would be an obstacle to her own emotional
development as a person and thus have a deleterious effect on her
overall well-being. With these issues in mind, it will be instructive to
consider a well-known legal case in the United States involving frozen

In December 1988, seven embryos produced in vitro from the gametes of
Mary Sue Davis and Junior Lewis Davis were placed in cryogenic storage
for possible future implantation.(n32) In February 1989, the couple
filed for divorce, at which time the question arose as to whether the
right of Mrs. Davis (then remarried as Mrs. Stowe) to become a mother
outweighed Mr. Davis' right not to become a father. Arguing in Mr.
Davis' favor, John Robertson concluded that the right to avoid
biological offspring should have priority over the right to reproduce
using frozen embryos.(n33) While Robertson's argument is persuasive as
far as it goes, it pays insufficient attention to the interests of the
future children who may be produced from these embryos. More
specifically, it does not adequately consider how long-term
cryopreservation of embryos may adversely affect the well-being of
children born from embryos implanted in surrogate mothers after the
deaths of their biological parents, or if children are born when their
biological parents are at an advanced age.

These points underscore some of the disturbing implications of what
amounts to altering the normal lifespan of a human organism and the
normal reproductive cycle. In particular, it forces us to ask whether we
have a moral obligation to impose some time limit after which frozen
embryos should not be implanted. Indeed, the Human Fertilization and
Embryo Act of 1991 in the United Kingdom stipulated a five-year limit on
the storage of frozen embryos, after which time they were to be
destroyed. Even if time limits on storage resolve the problems involving
the length of a biological lifespan and the reproductive cycle, the
question remains as to whether disposing of embryos is morally

Bonnie Steinbock maintains that it matters whether we think that embryos
should be preserved because of their symbolic value or because they have
a right to life. The import of this question derives from a distinction
she draws between moral status and moral value.(n34) Moral status is
limited to beings with interests of their own, that is, sentient, aware,
beings. Moral value concerns the symbolic value of entities, even if
they lack moral status. The debate in the United Kingdom may be taken
either from the point of view of moral status or from that of moral
value. If, as the Church maintains, embryos have moral status and
rights, then it is impermissible to deliberately destroy them. But if
they lack moral status, then we still can discuss whether respecting
them as symbols of human life is consistent with destroying them.(n35)
By Steinbock's lights, destroying embryos is as respectful of human life
as is keeping them frozen for long periods, and this understanding of
moral value seems plausible.

Nevertheless, the possibility that deletion of defective genes and
insertion of normal genes in embryonic cells will become feasible in the
near future may provide a reason for keeping embryos in frozen storage.
This would be the case if parents wanted to have a normal child at some
point not too late in their lives and were able to produce only one
viable but genetically abnormal embryo from their gametes. Yet if they
were able to produce multiple embryos and none of them was genetically
abnormal, then, given that there is no moral obligation to bring people
into existence, there would be no corresponding moral obligation to
preserve any of these embryos on the basis of their presumed moral

I have examined two aspects of reproductive biotechnology -- genetic
testing and selective termination of defective embryos, and long-term
cryopreservation of embryos -- and have explored the ethical
implications of each. In the first case, I have argued that we are
morally required to terminate the development of embryos with genetic
defects that cause severe disease or disability in people who develop
from them. The moral justification for this view is that it is wrong to
cause people to exist when the avoidable pain and suffering they
experience make their lives not worth living on the whole. This claim is
motivated by both the person-affecting and impersonal harm principles.
If we cause these people to exist with severe disease and disability,
then we defeat their interest in living without pain and suffering. Or,
if we are considering whether to cause people to exist, then it is
better, other things being equal, to prevent the existence of a person
with severe cognitive and physical disability and instead bring into
existence a person with normal cognitive and physical functioning. By
doing so, we avoid gratuitously adding to the total amount of suffering
in the world. In addition, considerations of justice support this
position, because it means that people will not come into existence with
a condition that will severely limit their opportunities for achieving a
decent minimum level of lifetime well-being. Consistent with the idea of
negative eugenics, we should prevent the existence of people who would
have severe disease and disability, not in order to raise the average
level of people's cognitive and physical functioning, but rather to
prevent the pain and suffering that make people's lives not worth living
on the whole. The aim of negative eugenics is disease prevention and
health promotion, not enhancement of normal capacities.

With respect to long-term cryopreservation of embryos, I have cited
reasons for not preserving embryos for too long when it entails harmful
psychological effects on a child born after the deaths of its biological
parents, or when its parents are at an advanced age. However, if genetic
technology develops in the near future to the point of making it
feasible to correct genetic defects at the embryonic stage of
development, then this may provide medical and moral grounds for
preserving them. Such genetic alteration would mean that a biologically
and psychologically different person would come into existence from the
person who would have come into existence without genetic alteration to
the embryo. Yet what matters morally is not who comes into existence,
but that if we decide to bring a person into existence, we ensure,
insofar as we can, that they not experience severe pain and suffering
over the balance of their lives.

In time, recessive genetic disorders may become amenable to somatic-cell
gene therapy. Perhaps both recessive and dominant disorders will be
prevented by germ-line genetic alteration at an early stage of a
developing human organism. The latter would have profound medical and
moral implications for the evolution of genetic mutation in the human
species as well as for our obligations to generations in the distant
future. But the genetic technology we presently have already gives us
considerable power to determine which people will exist and the sorts of
lives they will have in the near future.(n36)

(n1) This thesis derives from Jan Narveson's claim that we do not have a
moral duty to make happy people, but only to make people happy. He
argues that the benefit of an act is the good it brings to already
existing people and does not include the good of people who come into
existence as a result of the act. See 'Utilitarianism and New
Generations', Mind 76 (1967), pp. 62-72, and 'Moral Problems of
Population', Monist 57 (1973), pp. 62-86. John Broome and Adam Morton
discuss different aspects of the moral asymmetry thesis in 'The Value of
A Person', Proceedings of the Aristotelian Society, Supplementary Volume
68 (1994), pp. 167-98.

(n2) Here I follow the definition of harm given by Joel Feinberg in Harm
to Others (New York, Oxford University Press, 1984), pp. 102-4, and
Allen Buchanan and Dan Brock in Deciding for Others: The Ethics of
Surrogate Decision Making (New York, Cambridge University Press, 1989),
pp. 162-9. Broome, ibid., Derek Parfit, Reasons and Persons (Oxford,
Clarendon Press, 1984), Part IV, and John Harris, Wonderwoman and
Superman: The Ethics of Human Biotechnology (Oxford, Oxford University
Press, 1992), p. 89, define personal harm in comparative terms. That is,
a person is harmed when she is made worse off than she would have been
otherwise. I avoid using the comparative sense of harm in considering
whether being caused to exist with disabilities harms people, because
these people would not exist without the disabilities they have, and a
coherent comparison can be made only between two states of existence.
The comparative sense of harm can be invoked only insofar as people
exist and have interests. Otherwise, we should use an impersonal sense
of harm, comparing two distinct potential lives of two distinct
potential people.

(n3) Parfit defends this principle in Reasons and Persons, Ch. 18, and
'Comments', Ethics 96 (1986), pp. 858 ff., as does Jonathan Glover,
'Future People, Disability, and Screening', in Peter Laslett and James
Fishkin, eds. Justice Between Age Groups and Generations (New Haven,
Yale University Press, 1992), pp. 127-43.

(n4) This idea is discussed by Parfit, Reasons and Persons, and Harris,
Wonderwoman and Superman, p. 90.

(n5) See Michael Lockwood, 'When Does A Life Begin?', in Lockwood, ed.,
Moral Dilemmas in Modern Medicine (Oxford, Oxford University Press,
1985), pp. 9-31, Norman M. Ford, When Did I Begin? (Cambridge, Cambridge
University Press, 1988), pp. 97 ff., Stephen Buckle, Karen Dawson, and
Peter Singer, 'The Syngamy Debate: When Precisely Does A Human Life
Begin?', in Singer et al., eds., Embryo Experimentation (Cambridge,
Cambridge University Press, 1990), Ch. 19, Harris, pp. 61-5, and Jeff
McMahan, 'The Metaphysics of Brain Death', Bioethics 9 (1995), pp.

(n6) McMahan draws a similar distinction between persons and human
organisms in 'The Metaphysics of Brain Death', as does Robert Elliot in
'Identity and the Ethics of Gene Therapy', Bioethics 7 (1993), pp.
27-40, and 'Genetic Therapy, Person-Regarding Reasons and the
Determination of Identity', Bioethics 11 (1997), pp. 151-60. Compare
these accounts with that of Ingmar Persson, who draws a three-fold
distinction between a conceptus, a human being, and a person in 'Genetic
Therapy, Identity and the Person-Regarding Reasons', Bioethics 9 (1995),
pp. 16-31. For a defense of the view that we are essentially human
animals, see Eric Olson, The Human Animal: Personal Identity Without
Psychology (Oxford, Clarendon Press, 1996), and 'Was I Ever A Fetus?',
Philosophy and Phenomenological Research 57 (1997), pp. 43-59.

(n7) In Causing Death and Saving Lives (Harmondsworth, Penguin, 1977),
Glover says that a fetus is a potential person (p. 122), and Harris
holds that embryos are potential persons, or 'pre-persons' (p. 58).
Buckle subtly discusses the difference between the potential to become
and the potential to produce in 'Arguing from Potential', Bioethics 2
(1988), pp. 227 ff. Reprinted in Singer et al., Ch. 9.

(n8) Elliot, 'Identity and the Ethics of Gene therapy', and 'Genetic
Therapy, Person-Regarding Reasons and the Determination of Identity'.
McMahan explores the implications of the differences between genetic
techniques that are identity-determining and those that are
identity-preserving in 'Cognitive Disability, Misfortune, and Justice',
Philosophy & Public Affairs 25 (1996), pp. 3-35.

(n9) Tom Regan first argued for this position in 'Feinberg on What Sorts
of Beings Can Have Rights', Southern Journal of Philosophy 14 (1976),
pp. 485-98.

(n10) Reasons and Persons, pp. 488-9.

(n11) In 'The Paradox of Future Individuals', Philosophy &Public Affairs
11 (1982), pp. 93-112, Gregory Kavka defines a restricted life as 'one
that is significantly deficient in one or more of the major respects
that generally make human lives valuable and worth living' (p. 105). Yet
Kavka says further that 'restricted lives typically will be worth
living, on the whole, for those who live them' (p. 105). When I say that
life is or is not worth living for a person, I mean it in the subjective
rather than objective sense, or, what it is like for the person who
lives it. McMahan offers insightful discussions of this and related
issues in 'Cognitive Disability, Misfortune, and Justice', and 'Wrongful
Life: Paradoxes in the Morality of Causing People to Exist', in Jules
Coleman and Christopher Morris, eds., Rational Commitment and Social
Justice: Essays for Gregory Kavka (Cambridge, Cambridge University
Press, forthcoming).

(n12) Reasons and Persons, Ch. 16, and 'Comments', pp. 854-62. Others
who address this problem include McMahan, 'Cognitive Disability' and
'Wrongful Life', Kavka, 'The Paradox of Future Individuals', James
Woodward, 'The Non-Identity Problem', Ethics 96 (1986), pp. 804-31,
Matthew Hanser, 'Harming Future People', Philosophy &Public Affairs 19
(Winter 1990), pp. 47-70, and David Heyd, Genethics: Moral Issues in the
Creation of People (Berkeley, University of California Press, 1992),
Chs. 4, 6. Robert Adams first articulated the Non-Identity Problem in
'Existence, Self-Interest, and the Problem of Evil', Nous 13, (1979),
pp. 65-76.

(n13) 'Future People, Disability, and Screening', p. 141.

(n14) Ibid., p. 142.

(n15) I assume that the same number of people will exist in the
different outcomes. This avoids complications involving different
numbers of people and having to determine which group is better or worse
off than others. See Parfit's discussion of 'Same People Choices', 'Same
Number Choices', and 'Different Number Choices' in Reasons and Persons,
pp. 356 ff. See also Hanser, 'Harming Future People', and Heyd,

(n16) Helga Kuhse and Peter Singer claim that 'we can, of course, damage
the embryo in such a way as to cause harm to the sentient being it will
become, if it lives, but if it never becomes a sentient being, the
embryo has not been harmed'. See 'Individuals, Humans, and Persons: The
Issue of Moral Status', in Embryo Experimentation, p. 82. Furthermore,
Harris maintains that 'harm done at the pre-person (embryo) stage will
be harm done to the actual person she becomes. It is a form of
delayed-action wrongdoing'. Wonderwoman and Superman, p. 153. I believe
that persons can be harmed or wronged by what we do or fail to do to
embryos even if embryos do not strictly speaking become persons.

(n17) Patricia Baird provides an excellent overview of these issues in
'Altering Human Genes: Social, Ethical, and Legal Implications',
Perspectives in Biology and Medicine 37 (1994), pp. 566-75. See also
Leroy Walters and Julie Gage Palmer, The Ethics of Human Gene Therapy
(New York, Oxford University Press, 1997).

(n18) Elliot and Persson fail to recognize this in their respective uses
of 'gene therapy'.

(n19) The diseases I discuss involve genetic defects in the nuclei of
cells. Genes in the mitochondria of cells can mutate in the same way
that the more familiar nuclear genes do. And like nuclear genes,
mutations in mitochondrial genes may lead to disease. There are
indications that familial Alzheimer disease may be caused by a faulty
mitochondrial gene, though the research has not yet yielded any
definitive conclusions. Moreover, my concern is with genetic testing
rather than genetic screening. 'Genetic testing denotes the use of
specific assays to determine the genetic status of individuals already
suspected to be at high risk for a particular inherited condition
because of family history of clinical symptoms; genetic screening
involves the use of various genetic tests to evaluate populations or
groups of individuals independent of a family history of a disorder.'
Arno Motulsky et al., Assessing Genetic Risks: Implications for Health
and Social Policy (Washington, D. C., National Academy Press, 1994), p.

(n20) But see R. M. Blaese et al., 'Treatment of Severe Combined
Immunodeficiency (SCID) Due to Adenosine Deaminase Deficiency with CD34+
Selected Autologous Blood Cells Transduced with a Human ADA Gene', Human
Gene Therapy 4 (1993), pp. 521-7, M. Grossman et al., 'Successful Ex
Vivo Gene Therapy Directed to Liver in a Patient with Familial
Hypercholesterolemia', Nature Genetics 6 (1994), pp. 335-41, R. C.
Boucher et al., 'Gene Therapy for Cystic Fibrosis Using El Deleted
Adenovirus: A Trial in the Nasal Cavity', Human Gene Therapy 5 (1994),
pp. 615-39, and Melissa A. Rosenfeld, 'Human Artificial Chromosomes Get
Real', Nature Genetics 15 (1997), pp. 333-5.

(n21) Canavan's is a degenerative disease that strikes infants, leading
to the decay of the nervous system and early death. Hurler syndrome
involves disruption of cognitive development in early childhood and
usually death by age 10. Lesch-Nyhan syndrome causes both mental
retardation and compulsive self-mutilation in boys. Philip Kitcher
offers an insightful discussion of the genetic causes of these and other
diseases in The Lives to Come: The Genetic Revolution and Human
Possibilities (New York, Simon and Schuster, 1996).

(n22) See Glover, 'Future People, Disability, and Screening', McMahan,
'Cognitive Disability', and Allen Buchanan, 'Equal Opportunity and
Genetic Intervention', Social Philosophy and Policy 12 (1995), pp.
105-35, and 'Choosing Who Will Be Disabled: Genetic Intervention and the
Morality of Inclusion', Social Philosophy and Policy 13 (1996), pp.

(n23) R. G. Edwards and J. Purdy, Human Conception In Vitro (London,
Academic Press, 1981), p. 373.

(n24) See Feinberg, 'Wrongful Life and the Counterfactual Element in
Harming', in Freedom and Fulfillment (Princeton, Princeton University
Press, 1992), pp. 3-36, Heyd, Genethics, Ch. 1, Harris, Wonderwoman and
Superman, Ch. 4, and McMahan, 'Cognitive Disability' and 'Wrongful

(n25) Thomas Hurka presents a model that measures quality of life in
terms of averaging achievements in earlier and later stages of life in
Perfectionism (New York, Oxford University Press, 1993), pp. 70 ff. See
also Brock, 'Quality of Life Measures in Health Care and Medical
Ethics', in Life and Death: Philosophical Essays in Biomedical Ethics
(New York, Cambridge University Press, 1993), pp. 268-324.

(n26) I thank a referee for Bioethics for raising this issue.

(n27) 'Choosing Who Will Be Disabled', p. 32. Emphasis added.

(n28) Ibid., p. 33.

(n29) See, for example, Daniel Kevles, In the Name of Eugenics: Genetics
and the Uses of Human Heredity (New York, Alfred A. Knopf, 1985), an
examination of the history of eugenics in the United States.

(n30) The Lives to Come, p. 202. See also Glover, What Sort of People
Should There Be? (Harmondsworth, Penguin, 1984), John A. Wagner, 'Gene
Therapy Is not Eugenics', Nature Genetics 15 (1997), p. 234, and
Buchanan, Brock, Norman Daniels and Daniel Wikler, In the Shadow of
Eugenics: the Human Genome Project and the Limits of Ethical Theory

(n31) Eight years ago, in 'Contemporary and Future Possibilities for
Human Embryonic Manipulation', Mark Ferguson wrote 'it is unclear how
well the ageing human female reproductive system would cope with such
good embryos'. In Anthony Dyson and John Harris, eds., Experiments on
Embryos (London, Routledge and Kegan Paul, 1990), p. 10. Yet recently a
woman of 63 in Los Angeles gave birth to a healthy baby girl. See Gina
Kolata, 'A Record and Big Questions as Woman Gives Birth at 63'. New
York Times, April 24, 1997.

(n32) Davis v. Davis 1989 WL 140495 (Tenn Cir 1984) rev'd 842 S. W. 2D
588, 597 (Tenn 1992).

(n33) 'Resolving Disputes over Frozen Embryos', Hastings Center Report
19 (November-December 1989), p. 11. More recently, Robertson examines
this and related issues in Children of Choice: Freedom and the New
Reproductive Technologies (Princeton, Princeton University Press, 1996).

(n34) Life Before Birth: The Moral and Legal Status of Embryos and
Fetuses (New York, Oxford University Press, 1992), pp. 5-41.

(n35) I thank Bonnie Steinbock for pointing this out.

(n36) I am grateful to Michael Burgess, David Donaldson, Chris McDonald,
Bonnie Steinbock, and an anonymous referee for Bioethics for very
helpful comments on an ancestor of this paper. Work on the paper was
supported by a Killam Postdoctoral Fellowship at the Centre for Applied
Ethics, University of British Columbia, which also is gratefully


By Walter Glannon, Department of Philosophy University of Calgary

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