What is a Person?
What is a Person? topics include: PVS ,
Brain Death The Problem of Artificial Life Support & Are We More Than Just Our Brains?
"'TK' who has been brain dead for over 19 years. He has been brain dead since the age of four, and yet, far from his body slowly decaying, his body has grown, developed through puberty, overcome infections, and healed wounds, all things that would seem to be clear signs of somatic integration. . . ."
Jesus was once asked, "Who is my neighbour?" (Lk 10:29). Modern versions of this same question arise today in bioethics. If we create a human-animal hybrid, will it be an animal we can experiment on, or, will it be 'my neighbour'? How might we know? Similarly, what about a comatose patient, or the collection of cells that makes up the early embryo? This article will summarise contemporary scientific data about the beginning and end of life and indicate what it shows about personhood, then it will comment on the personhood of hybrids. It will first outline some erroneous secular models of personhood, indicating why many secular bioethicists not only support abortion but also allow for infanticide.
The question of personhood is vital to contemporary ethical debates because 'persons' are those entities that bear 'rights', most specifically, the right to life. This said, the concept of personhood and rights has become fraught with confusion.
The United Nations' 1948 Declaration of Human Rights spoke of the "inherent dignity? rights? and worth of the human person". Similarly, the Catholic Church repeatedly extols the "rights inherent in every person" To say that dignity and rights are 'inherent' is to say that they belong to someone in virtue of what he is: they are not something granted to him by others.
The above notion of 'inherent' personal dignity is something that used to be accepted throughout the modern world; however, many today question it. Mary Warnock, often referred to in the media as Britain's "philosopher queen", says that there are no 'natural rights'; rather, all rights are granted by the state or by someone. Thus, she says, there is no natural right to not be a slave. "It is essentially for society to decide who is a bearer of rights" and the question of who is to be counted as a person is similarly "a decision that society has to make". It was such a notion that enabled the Nazis to decide that Jews, Gypsies and other non-Aryans were non-persons. If rights are granted by the state, then there is no court of appeal.
Another means of denying the personhood of many humans
consists in choosing a particular facet of human existence that is said to be
necessarily present for a human to be a person. The most popular facet appealed
to by contemporary ethicists is the "self-consciousness requirement".
John Harris, for example, argues that if you cannot be self-conscious then you
cannot value your life and cannot mind if your life is taken away from you.
Thus Harris and Michael Tooley are among the many who justify not only abortion
but infanticide. Infants have no self-conscious desire to live and so do not
have this desire 'thwarted' by being killed. There are two methodological
problems with defining a person this way. First, the facet chosen to define
personhood ends up being arbitrary. Different writers define personhood by
different facets: self-consciousness, rationality, and neocortical function
being but a few of the debated options. This thus reduces personhood to a matter
of decision (as Warnock's approach does). Second, and more fundamentally, such
an approach to personhood only values healthy people, and excludes the weak,
sick, and vulnerable. It is only healthy people who are defined as persons. Such
an approach lends itself to creating an aristocracy of those considered to be
healthy, attractive, and desirable. Such an approach values someone for what he
has (health, beauty, intelligence, rationality) not for what he is (a human with
The Catholic approach to personhood is rooted in a belief that dignity and rights are inherent in someone naturally. Contrary to Warnock, your rights should be recognised by other people, but you possess these rights whether or not someone else recognises them. People have a sense of a 'natural justice' that exists whether or not the law protects it, and such a sense is well-founded. A point even more fundamental to the Catholic position is the following: contrary to Harris, a person is defined by his 'type', not just by whether he is a healthily functioning specimen of his type. Philosophically, this means that a person is defined by his 'nature'. The standard Catholic definition of the person was offered by Boethius in the 6th Century: "A person is an individual substance of a rational nature".
This definition raises a question: Why do beings with 'a
rational nature' deserve respect? What about them implies dignity? A few brief
comments in answer to this question follow.
From a Christian perspective, the answer to the above question relates to the image of God in the human being. According to the Genesis account, of all creation it was only man and woman that were made "to his image" (Gen 1:26). Thomas Aquinas notes that this image is not something merely extrinsic to man, it is not something imprinted onto him, rather, it is something that holds from the very type of being that he is: he is 'of a rational nature'. God, who is intellect, is also of a rational nature. Christian Faith teaches us about two types of beings made to God's image: angels and humans. Both are of a rational nature and are thus inherently "an image of the same species" as God. Such 'persons' thus hold a dignity that separates them from the rest of creation. The purpose which Thomas sees in the image of God in man is to make him capable of turning to God. It is only in virtue of having an intellectual nature that man has "a natural aptitude for understanding and loving God; and this consists in the very nature of mind, which is common to all men".
If the above has briefly indicated why Christians should respect persons, what reasons might a non-Christian accept? It can be conceded that Catholic apologetics has not yet focused enough on the answer to this question.
For nearly two centuries Kant's notion of personal Rights and
inherent dignity has largely held sway in the western world, and christian
thought has been able to enjoy the fact that secular thinkers promoted the
notion of human dignity (even if they did so in a confused manner and for
mistaken reasons). Today, however, Kant's notion of personal rights seems to
have been largely superseded by Mill's utilitarianism. There seems to be no
common ground in either metaphysical terminology or in moral principles.
Nonetheless, there are solid reasons for a non-Christian to hold that 'persons'
possess inherent dignity. We can argue against Warnock, Harris, et al without
referring to Christian revelation.
First, in keeping with Aquinas, the logic of the Faith synthesis proposed by this magazine argues that even non-Christians can recognise the dignity of persons once they recognise the existence of God (even without yet recognising Christ). The existence of God is capable of rational demonstration. Such a God can be rationally demonstrated because He is Himself rational and has structured His creation rationally. The non-Christian rational believer in a rational God can recognise that both man and God are capable of a non-material activity, namely, reasoning. This is only possible because both are of a non-material i.e. spiritual nature, and the existence of the spiritual soul in man is a truth (we argue) that can be deduced from reason. Thus, even without the added clarity that faith in Christ (the "image of the invisible God" (Col 1:15)) brings, the dignity that Christians accord to all humans (because all humans are made to God's image) can be recognised by a logic available to non-Christians. The Faith vision uses modern knowledge of matter and the human body to attempt an update the specific Thomistic arguments for God and the soul.
A second reason available to non-Christians can be founded in the 'phenomenological' reasoning of Pope John Paul II. Kant's moral analysis started with the supposition that there exists something "whose existence has in itself an absolute worth, something which as an end in itself could be the ground of determinate laws". He concludes that rational beings are such ends. John Paul II through a phenomenological analysis of behaviour purifies this insight to reveal the existence of something that deserves nothing less than love: "The person is a good towards which the only proper and adequate attitude is love... the person is the kind of good which does not admit of use and cannot be treated as an object of use and as such the means to an end." The remainder of this article will use contemporary science to apply Boethius' definition to the start and end of life, and then to hybrids. If the Boethian definition is used to analyse scientific data about human biology, it can easily be reduced to two issues. First, a person must be an individual ('an individual substance'); second, he must be properly human (and thus 'of a rational nature'). While neither of these are scientific questions per se, nonetheless, science can give useful indications of what the answers might be.
Before commenting on the embryo, it will be useful to summarise a few basic points about its early development. After the sperm penetrates the egg membrane the single-cell product is referred to as the zygote. It is only after the cell divides and becomes a two-cell embryo that the DNA is established in each cell. The cells then divide repeatedly resulting in a 2, 4, 8 etc cell cluster. At this early stage each cell is called 'totipotent' because, if it is separated from the cluster, each cell is capable of developing into a whole new individual. In addition, the cell cluster can divide in two and form identical twins. By 14 days the cells have visibly specialised, the primitive streak (the precursor of the backbone) forms, and implantation in the lining of the womb occurs. After this stage the various organs form.
Before answering the question of when a person first comes
into existence, it is necessary to respond to a common objection. It is often
noted that a large number of zygotes fail to implant in the womb, and thus die.
This figure is sometimes speculated as being more than 30%. It is said that
surely these cannot all have been persons, How could God allow such a large
percentage of persons to die? Thus, zygotes cannot be persons. Two points can be
noted in response to this. First, for much of human history, and even today in
many parts of the world, infant mortality has been much higher than 30%. But
this is no reason to argue that infants are not persons (rather, it is reason to
seek to promote the health of infants). Second, the 30% statistic fails to
observe why the early embryos do not implant.
Many fail to implant because some defect has occurred in the process of fertilisation. Often the products of fertilisation are not true embryos but are what would be more "properly called pseudo-embryos". Fertilisation often fails to produce the cell-to-organism transition, and thus a 'fertilised egg' is not necessarily an embryo. The loss of these pseudo-embryos is not the loss of human beings. While it seems impossible to know the exact percentages, it seems reasonable to suggest that these make up a significant part of the '30%' that fail to |10| implant. The high rate of non-implantation is thus no reason to suggest that a successfully fertilised egg, i.e. the single-cell zygote, is not a person.
As has been noted, in order for the embryo to satisfy the
Catholic definition of personhood it must be an individual; however, this is
precisely what many ethicists dispute. Because the single-cell zygote lacks
established DNA it is said that it cannot be an individual. It is further
claimed that even after this stage the early embryo is not an individual but is
merely a loosely-related collection of cells. These cells develop and eventually
some of them become an individual, but (it is alleged) "purposeful development
[from the single-cell zygote to the later embryo] occurs between cells, but not
within an ongoing multicellular ontological individual from the two-cell stage".
There are a number of reasons given to support this interpretation of the data.
It is said that the cells behave independently of one another: some become part
of the 'embryo proper', while some become part of other things like the
placenta. Further, the 'independent' nature of these cells is indicated by the
fact that they are 'totipotent'. According to this interpretation, the
collection of cells does not become an individual until each cell is determined
in its eventual function in the final embryo. This is said to occur at the
14-day stage when the 'primitive streak' (the beginnings of the backbone) forms
and the cells coalesce into "one whole multicellular individual living human
being, possessing for the first time a body axis and bilateral symmetry".
It is only at this stage that one can speak of an individual, and thus,
possibly, a person.
The above interpretation of the development of the embryo was held by many in the latter part of the 20th Century, and was used in 1984 by the Warnock Report to justify experimentation on human embryos before the 14-day stage. However, recent embryology does not support the above interpretation. In order to refute it, each aspect of it must be examined.
Yes, an individual
It is said that the single-cell zygote cannot be an individual because it does not yet have established DNA. DNA, however, does not constitute individuality. Individuals can exist with different DNA in different parts of their bodies. Experiments on black and white mice have combined black mice embryos with white mice embryos, to form a single 8-cell embryo out of two 4-cell embryos. This embryo then develops as a whole, and results in an adult mouse with different DNA in different parts of its body, and a resulting mixture of coloured fur. Adult humans have also been found who possess different DNA in different parts of their body (such humans presumably formed by two non-identical embryos combining in the womb). Conversely, identical twins share the same DNA, and yet are two individuals. DNA does not constitute individuality.
What then can be said about the collection of cells that makes up the early embryo? And, what is known about their development? Although much of the scientific establishment recently thought that the young embryo was simply a uniform mass of totipotent cells this "view is now undergoing something of a revolution". It has long been known that the type of development witnessed in a particular embryonic cell is somehow dependent on its position in the embryo, i.e. its position relative to the other cells of the cluster. It is now known that the two-cell embryo is already determined as to what the two different cells will develop into. The progeny of one cell will form the extra-embryonic material like the placenta while the progeny of the other cell will form the 'embryo proper'. These cells develop according to their position, and so, even though the cells appear to be the same and appear to be simply a uniform mass of totipotent cells, they are actually cells operating according to their programming. The cell-cluster develops as an integrated whole. In the service of the whole, some of these cells purposefully form tissues like the placenta that will ultimately be shed (just as children shed milk teeth as they become adults). Other cells develop into the body organs.
The above has indicated that the cells of the cluster behave
according to their positional information; however, it might be asked where the
positioning information originates. The answer to this question returns the
analysis to the first moment of the zygote's existence. The positioning
information that determines the embryo's development is established by the
positioning that first established the embryo, namely, the position where the
sperm first penetrated the egg membrane. The position of the entry point of the
sperm into the ovum "patterns the zygote so that it divides in a specific way?
and the embryo is never an unorganised mass of cells".
In fact, the position of the sperm entry point determines not only the position
of the first cell cleavage but also the position of the subsequent primitive
streak at the 14-day stage and the position of the backbone after that. It
follows that individuality is established not by the formation of the primitive
streak but by the sperm's penetration of the ovum. This can also be seen by the
fact that "some one to three minutes after sperm and egg unite"
there is an explosive increase in calcium levels, coinciding with the membrane
hardening to resist penetration by any other sperm. The fertilised egg is thus a
closed system and develops as an individual, even before the DNA is established.
Far from individuality being established at 14 days, it is established at the
moment of fertilisation.
It can be noted that the 'determining' of the cells at the early stage is still very elastic, i.e. they can be redetermined or re-programmed if their position changes. This is what happens when a cell is removed from the cluster. Its positioning relative to the other cells of its former cluster is lost, and so (it seems) it redetermines itself to develop into a new individual. Far from this indicating that there was not an individual existing previously, this capacity of the cells to be redetermined simply indicates the extent to which the cells are already part of a proper individual: that they can be re-programmed indicates that they are already programmed. To make a comparison, an adult's liver can be transplanted to another adult without this suggesting that he is not a person. Similarly, embryonic cells (which are admittedly much more flexible than adult liver cells) can be transferred to another cell-cluster or even isolated to form a new individual. This does not imply that the embryo the cell was taken from was not already a true individual.
The developmental elasticity of the cells, as noted above, is
witnessed in nature by the phenomenon of monozygotic twinning: the cell-cluster
divides in two and two identical twins form. This division can only happen
during the first 14 days of the embryo's development, i.e. while the cells of
the embryo retain the above mentioned ability to be re-determined. After 14 days
the primitive streak forms and the embryo implants (it is not known precisely
which of these two factors makes twinning no longer possible).
Little is known about why spontaneous twinning happens, however, there are strong reasons to think that it is caused by a defect in the programme of development in the embryo. It can be speculated that the programme of development normally leads to a single foetus. A minor defect in the development causes the cell-cluster to divide in two, and two individuals form. Such a scenario would suggest that twinning would be accompanied by other defects; this is exactly what repeated studies have shown. While the overall frequencies remain low, "in comparison with singleton births, twins have significantly higher reported frequencies of" a diverse range of defects, ranging from Downs Syndrome to indeterminate sex to branchial cleft.
The above has argued that a person exists before twinning would occur. It might then be asked, what happens to the original person if his cells are split in two in the formation of twins? There are three basic possibilities that have been suggested to describe what happens to the 'person' in the event of twinning. First, there might be two souls present at fertilisation, so that what was thought to be one zygote after fertilisation was actually two, somehow destined to result in twinning. In this case the original zygote has an active potential to twin and needs no additional stimuli. Second, there might be only one soul, one person, in the original zygote. The zygote would then have a passive potential to twin which would be triggered by some outside stimuli. When the twinning occurs there is then one new individual and one continuing individual.
This would be similar to the creation of a new individual in cloning in that this process does not destroy the preexisting individual. Finally, as a variation on the second case, when twinning occurs the existing individual is destroyed and two new individuals come into existence. This last interpretation might accord with the higher frequency of defects, defects which might be seen as an indication that the programme of development has been radically disrupted. Also, this last interpretation seems to most closely describe the Aristotelian account of what happens to a living individual when it is divided. Nonetheless, any of these descriptions might explain what happens in twinning in a way that does not call the personhood of the original zygote into question.
The above, very briefly, has outlined some recent scientific data that indicates that the embryo is established as an individual the instant the sperm penetrates the ovum. This, however, does not conclude that this individual is a person. The second half of Boethius's definition maintains that the individual must be 'of a rational nature'. Is this true of the embryo? How could this be established? The answer to this question lies in a simple philosophical principle: a thing is known by its behaviour. What can be said of the behaviour of the embryo? To answer this, its potential must be considered.
The argument from 'potential' says that the 'nature' or 'kind' of a thing is indicated not merely by how it acts today but by how it is capable of acting in the future. In particular, by what it has the potential to do. An infant is not presently rational; however, it has the potential to develop rationality. It is thus reasonable to describe the 'nature' of an infant by referring to what it has the potential to do, not just what it can presently do. A dog does not have the potential to develop rationality, no matter how much time it is given and how many aids it is given. Rationality is simply not part of its nature. A dog is therefore not 'of a rational nature'.
To indicate the potential of a thing, there is an additional factor that needs to be considered: is its development that of an individual, or, does it change from one individual to another individual? For example, those who misunderstand the argument from potential say: a sperm has the potential to develop into an adult person. This, however, fails to observe that the sperm is not the same individual that the later embryo is. The combination of the egg and the sperm replaces the two individual substances that were the egg and the sperm. A new individual is instantiated.
There is thus a profound difference between the sperm's passive potential to be changed into something with a rational potential and the zygote's active potential to develop itself into an adult with functioning rationality. The difference is the difference between the development into an individual (sperm and egg into the zygote) and the development of an individual (the zygote through its many stages of human maturation). Once the zygote has formed it develops through many stages, but none of these stages can be claimed to indicate the change from one individual to a different individual. It thus follows that the rational adult is the same individual as the fertilised zygote. The activity of the rational adult thus tells us the 'kind' of thing that the zygote already is: it is 'of a rational nature'.
The above argument from potential can be clarified by considering the difference between living beings and artefacts, and the different ways in which they each change. An artefact like a car can gradually have its various parts replaced and changed. By doing this what started as a car can end up becoming an airplane. This is because an artefact is brought about, is "caused by external forces". There "is no internal, ordering principle to ground its unity, nor to ground ordered change or guide the movement? toward an ordered telos". As a result there is no limit to the way in which it can change. In contrast, living things are very limited in the way they can change. A puppy can grow and change but it cannot grow and change into an oak tree, only acorns can become oak trees. This is because living things possess "an internal nature" such that this "nature directs the developmental process of the individual substance and establishes limits on the variations each substance may undergo and still exist".
One significant aspect of the above noted distinction concerns the way in which things can be defined. Artefacts can be defined by their function. The mind of the artificer gives an external causation and meaning to the collection of parts that makes up the artefact that performs the function he desires. Planes fly. Cars motor. If a plane ceases to be able to fly it ceases to be a plane. An artefact is defined by what it does; lacking an inherent unifying principle there is no other means of defining what it is. This does not hold for substances like living beings: "Essence precedes function" and a substance is defined by "what it is, not what it does".
The nature of a species can be defined by what a species does, but the individual of the species is defined by what it is. 'Human nature' can be defined using "the ordinary practice of defining things from their highest activity, e.g. plants from vegetative life or animals from sensation". Human nature can thus be defined as rational. But this does not need to imply that every human person is functionally rational. Unlike an artefact, a living being is not defined by its functions or its functioning. A person "possesses [his] properties and parts" he is not defined by his possessions; rather, he is defined by his nature, his kind.
A further consequence of this relates back to the question of potential. The above noted difference between a living being and an artefact is relevant because it sheds further light on the way in which change occurs in an individual. An artefact can be changed because its individuality is not internal to it; there is a sense in which it is not truly an individual. In contrast, the limited manner in which a living individual can change helps indicate that it is the same individual that is changing. A thin man might become a fat man, but he will not become a cat or a car. He might change so that he is no longer a human, but only by killing him. This final manner of change, namely death, will be relevant in a latter part of this article.
This article has already considered the beginning of life and personhood. What of personhood at the end of life? Two categories will be noted in this article: PVS and brain death.
PVS, Persistent or Permanent Vegetative State, is a condition that has often been highlighted in the media. Many cases have been reported of people waking up from what is supposedly a 'permanent' state. Dr. Alan Shewmon is among the many who question the whole validity of the term and concept of PVS and say that "'Post-coma unresponsiveness' would have been an intellectually more honest and accurate term".
It can be noted that many secular approaches to personhood claim that PVS patients are not persons. If they cannot be self-conscious then they cannot be persons, argues Harris. Their body organs should thus be made available to others. In contrast with this, the Catholic Church holds that a person continues to be a person even though he is unhealthy and has lost the use of a highly important function, namely, consciousness. A person is valuable for what he is, not just when he is fully functioning. Thus the Church says of such patients that 'persons in the vegetative state deserve proper care'  and that such care includes the basic provision of food and water, even when these need to be artificially administered by intubation. To deny this is to be guilty of a type of dualism, saying that a man is only his mind, and that a living body is not still a living person.
The Bishops of England and Wales recently rejected a 1998 proposal by the UK Department of Health to define death as "the irreversible loss of the capacity for consciousness, combined with the irreversible loss of the capacity to breathe". This somewhat ad hoc definition combines two unrelated criteria: breathing and consciousness. Why should these two be said to define human life? For example, why not include heart beat? Warning against the dualism that similarly belittles PVS patients, the bishops said, "If the body retains its capacity to function as a living whole then it is alive, even if the capacity for consciousness is lost". The question then becomes: 'When does the body cease to be a living whole?' The brain's role (or not) in answering this question is what turns this article to the question of brain death.
Catholic thought defines death as the separation of the soul from the body. The soul integrates the person's functions, and so its departure results in the loss of integration of the bodily functions. Thus, though some body parts might continue some isolated activity (e.g. the stomach might continue digesting for a while) there is none of the integrated activity that defines a whole. This emphasis on integration and wholeness is another manner of expressing the concern identified in the embryo: only an 'integrated whole' can be an 'individual'. Until the 20th Century, in keeping with this notion of death, death was medically identified by the cardio-respiratory criteria, i.e. the cessation of spontaneous breathing and pulse.
These criteria, however, came to be questioned with the development of artificial ventilators and artificial nutrition and hydration. With this treatment in place, the lungs can still perform respiration and the heart keeps beating, even in the unconscious state now called 'brain death'. Nonetheless, it was said that once the brain had died there would be "inevitable asystole [cardiac arrest]" in a relatively short span of days (or possibly weeks). This 'inevitable' cardiac arrest was taken to be a sign that the body had lost its capacity to integrate itself. From a Catholic perspective this would seem to imply that the soul had already departed, i.e. that the patient had died. As a result, statements from the Pontifical Academy of Sciences assume this 'inevitable asystole' and approve the use of brain death criteria, as has (an albeit highly nuanced) statement from Pope John Paul II. Research published in the late 1990s, particularly by Shewmon, has questioned the accuracy of this medical data. This research has yet, it seems, to have been digested by the Pontifical Academy of Sciences and the Academy's documents maintain its approval of brain death criteria. Nonetheless, the Academy recently hosted a conference refuting the appropriateness of brain death criteria.
To many it would seem self-evident that a person without a functioning brain is dead; however, this assumption is typically founded on either a dualistic notion of man or a mistaken view of the brain's relationship to the body. To respond to the second notion it will be useful to indicate the manner in which the body can continue to function as an integrated whole even when there is complete brain death.
When someone is dead we might well expect the body to disintegrate and decompose. This does not happen in a brain dead patient. The patient is permanently unconscious and thus cannot feed himself and so needs to be fed and hydrated by tubes. Further, the part of breathing that involves the muscles moving air in and out of the lungs does not occur, and thus an artificial ventilator is needed to move air in and out of the lungs. "However, if 'breathing' is understood as a somatically mediative function, it is better understood as 'respiration' in the technical sense of exchange of oxygen and carbon dioxide" which continues in the brain dead patient. In addition to respiration, the heart continues to function (beating spontaneously), as do the other body organs. Moreover, if the patient is a child, the body will continue to grow and will develop through puberty.
Among the 175 cases that Shewmon has documented, the most spectacular concerns an individual identified simply as 'TK' who has been brain dead for over 19 years. He has been brain dead since the age of four, and yet, far from his body slowly decaying, his body has grown, developed through puberty, overcome infections, and healed wounds, all things that would seem to be clear signs of somatic integration. Lest it be thought that this is due to his not being truly brain dead, Shewmon notes that MRI scans indicate that his "entire brain, including the brain stem, had been replaced by ghost-like tissues and disorganized proteinaceous fluids". His body |14| needs to be kept on a ventilator, he is fed by a tube to his stomach (and he urinates spontaneously), but he needs little more than nursing care, all of which he receives at home. There are few cases that have been documented as long as TK because in most Western countries the brain dead patient soon has his ventilator switched off, and the body subsequently dies; the patients thus cannot be observed over a prolonged period of time.
What can be said of the above? Shewmon summarises his analysis by concluding that 'integration does not require an integrator': the body does not need the brain in order to keep functioning. Embryos, plants, and many lower animals are integrated wholes with no coordinating centre. Similarly, brain dead patients (if they survive the trauma to the body that was the cause of the brain death) can maintain somatic integration with less nursing care than many ICU patients receive. Such a brain dead patient would seem to clearly satisfy the criteria for personhood given by the Bishops of England and Wales. (Though the question of the treatment suitable to be given him is a further issue.) The only possible reason to declare such a patient to be dead comes from a dualist notion of man that denies that permanently unconscious patients are still persons.
A further comment on the personhood of the brain dead patient can be made by returning to the previously discussed analysis of change. With respect to the embryo, it was noted previously that there is a difference between the change of an individual and the change into an individual. If change is the type of continuous developmental change characteristic of living beings (as opposed to artefacts), then the individual remains the same individual. If this is applied to the brain dead patient it can be noted that there is a difference between the change of an individual and the change from an individual into a decaying corpse.
The latter change involves the destruction of the previous substance. Such a destruction is not witnessed in the change from a sick patient to a brain death patient: all that is witnessed is a loss of functionality. There is therefore no reason to assume that there has been a change from one type of individual to another type of individual. It is reasonable to assume that the brain dead patient remains the same individual he always has been, i.e. he remains 'of a rational nature', i.e. he is a person.
On a more speculative note, in the light of earlier comments, it will now be possible to return to the question of a human-animal hybrid, as was mentioned at the start of this article. A distinction must first be made between hybrids and chimeras. In Greek mythology the chimera had a lion's head, a goat's body and a serpent's tail. A chimera combines cells of each species in such a way that different parts of the creature have cells of a different genetic make-up. For example, the combined black and white mouse embryos referred to earlier in this article were chimeric. In contrast, a hybrid possesses the same DNA in each cell. It combines two (or more) species by combining their DNA. This can happen in nature, for example, a mule is the genetic cross of a horse and donkey.
How might the creation of animal-human chimeras and hybrids be analysed morally? The limited use of some animal tissues in human medical treatment is not morally problematic: for example, a monkey's heart can be transplanted into a human just as a mechanical heart can be. The Pontifical Academy for Life has suggested that a moral limit for such transplants would concern those organs that affect an individual's identity, namely, such transplants must exclude "the encephalon [brain] and the gonads [ovaries or testes], [which are] indissolubly linked with the personal identity of the subject because of their specific function".
This said, some proposals to combine human and animal embryos seem to move a step beyond the morally permissible. The attempt to make such chimeras or hybrids has been condemned by many Catholic moralists because to "mix the imago Dei with the non-imago Dei seems a violation". Further, at the very least, the process is immoral for the same reasons that IVF is contrary to the natural law: it would procreate separated from a loving marital act. The individual created would have been made as an object for the curiosity of the scientist. He would not have been created for his own benefit. Nonetheless, what might be said about the personhood of such a hybrid or chimera? After a scientist has made him, how should others treat him? This is the topic more proper to this article.
Before directly answering the above question it should be noted that Catholics already believe that there are nonhuman persons: angels are persons. In addition, while we have no particular reasons for thinking they exist, intelligent aliens on other planets would also be persons. They would be 'individual substances of a rational nature', i.e. persons. We would therefore be morally required to treat them as persons. This need not imply, however, that we have the same obligations to Martians that we have to humans. Catholic thought holds that members of a family have a particular duty to each other. Similarly, as part of the 4th Commandment, a citizen has a particular duty to members of his own country in patriotism. By extension it could be suggested that every human has a duty to other members of his species simply because they are members of his species. Thus a human should treat members of his own species with a familial love that would be beyond what he would extend to rational Martians. Nonetheless, this would be a very limited degree of prejudice in favour of your own species: a human's actions should never neglect (let alone violate) the personal dignity of a Martian. The very limited form of prejudice in favour of members of your own family might be taken as a guide in this regard.
While the above might seem fanciful, it offers a useful point of comparison for how we should treat any animal-human chimeras, and, how we should treat any new hybrid species that might be created. Such a new species might be comparable to a race of Martians. If they were formed in such a manner that they were capable of abstract rational thought processes then we would know that they are 'of a rational nature' and thus are persons. Given that they were formed, in part, from human tissue, it would seem appropriate to give them a broad degree of 'the benefit of the doubt' in manifesting rational nature. Thus, if they are persons they must be treated as such. If the judgment that they are persons is 'probable',41 then, again, they should be treated as persons.
The above paragraph suggested reasons for a limit to the moral preference they should be given: if they are sufficiently different to us to no longer be 'human', then, they would not be our brothers in the sense that 'all men are brothers'. However, it could well be argued that there is a different reason to treat them well: we should have compassion on them as violated persons, violated with a violation that cannot be removed as long as they live. Humans' care for such creatures could thus be reparation for the indignity perpetrated against them. (It might well be hoped that God has structured human nature in such a way that any attempt to create a human-animal hybrid would be so defective that it would not live, or that it would not be apt matter for a rational soul -but there is no way of knowing whether this is the case.) A further point of comparison might be made: A child that is the fruit of the violation of rape is worthy of the same respect as any other child. Similarly, a rational chimera that is the fruit of a scientist's immoral experiments is also worthy of being respected as a person.
To return to the central argument: This article has noted and rejected notions of personhood that deny that personal dignity is inherent to a person. It has further rejected notions that define persons by self-consciousness, excluding many sick and wounded humans from the class of persons. This article has instead sought to defend the Catholic notion of personhood, a notion that defines persons by what a being is not by what he possesses. Persons are persons even when they are in bad health and even when they fail to possess the attributes of rationality and consciousness. As this article has noted, there is sound scientific data to indicate that a person is instantiated at the first moment of fertilisation: the moment the sperm penetrates the egg membrane a closed system is created, an individual exists, an individual that will take a long time to develop the many features we associate with mature persons, but the immature person is a person nonetheless.
This article has also noted that personhood continues even after the capacity for self-consciousness is lost. In addition to PVS patients, there are strong reasons to argue that brain dead patients also continue to be persons and thus deserve the respect appropriate to persons. Finally, while this article has been wary of the morality of creating animal-human chimeras and hybrids, it has suggested that if they are found to be 'of a rational nature' they should be treated with full personal dignity.
 John Paul II, Evangelium Vitae (1995), 18.
 Mary Warnock, An Intelligent Person's Guide to Ethics (London: Duckworth, 1998), 85; 70. Warnock similarly dismisses the notion of a 'right to life' as "a pretty vague sort of right" (p.101). She concedes that the language of 'natural rights' may have some rhetorical value, but nothing more (p.109).
 Michael Tooley, "Abortion and Infanticide", in Bioethics: An Anthology, ed. Helga Kuhse and Peter Singer (Oxford: Blackwell, 1999), 24.
 John Harris, The Value of Life: An Introduction to Medical Ethics (London: Routledge and Kegan Paul, 1985), 17.
 [i] Thomas Aquinas, Summa Theologica, Ia, q.93, a.2.
 [ii] Ibid., Ia, q.93, a.4.; c.f. a.8.
 [iii] Immanuel Kant, Grounding for the Metaphysics of Morals: On a Supposed Right to Lie because of Philanthropic Concerns, trans. James W. Ellington, 3rd edition (Indianapolis: Hackett Publishing Company, 1993), n.428.
 [iv] Karol Wojtyla (Pope John Paul II), Love and Responsibility (New York: Farrar, Straus, and Giroux, 1981), 40-41.
 However, these cells are now thought not to be as totipotent as they were once thought to be.
 Nicanor Pier Giorgio Austriaco, O.P., "On Static Eggs and Dynamic Embryos: A Systems Perspective", National Catholic Bioethics Quarterly 3.4 (Winter 2002): 670. Hydatidiform moles and mutations preventing embryogenesis are two possible examples of pseudo-embryos. Germain Grisez similarly notes "many natural pregnancy losses are due to such severe chromosomal defects? these are not losses of human beings" (Germain Grisez, Living a Christian Life, The Way of the Lord Jesus, Vol. 2 (Quincy, Illinois: Franciscan Press, 1993), 497).  Norman Ford, The Prenatal Person Ethics from Conception to Birth (Oxford: Blackwell, 2002), 66.
 Ford, When Did I Begin? Conception of the human individual in history, philosophy and science (Cambridge: Cambridge University Press, 1988, reprint 1991), 171-2.
 Embryologist Richard Gardner of the University of Oxford, cited in Helen Pearson, "First division seals embryo fate", Nature [online edition] (2 October 2001).
 As is typical in such studies, the research has been done on mouse (or sheep) embryos, with it being thought that similar patterns of activity occur in human embryos.
 Karolina Piotrowska, Florence Wianny, Roger A. Pedersen and Magdalena Zernicka-Goetz, "Blastomeres arising from the first cleavage division have distinguishable fates in normal mouse development", Development 128.19 (October 2001): 3739. C.f. Berenika Plusa, Karolina Piotrowska, and Magdalena Zernicka- Goetz, "Sperm Entry Position Provides a Surface Marker for the First Cleavage Plane of the Mouse Zygote", Genesis 32.3 (March 2002): 193-8; Pontifical Academy for Life, "Final Communiqu?of the 12th General Assembly of the Pontifical Academy for Life and Congress on 'The Human Embryo in the Pre-implantation Phase: Scientific Aspects and Bioethical Considerations' " (23 March 2006).
 Nicanor Pier Giorgio Austriaco, O.P., "The Pre-Implantation Embryo Revisited: A Two-Celled Individual or Two Individual Cells", Linacre Quarterly 70.2 (2003): 122.
 Austriaco, "On Static Eggs and Dynamic Embryos", 666, 673.
 P.E. Doyle, V. Beral, B. Botting and C.J. Wale, "Congenital malformations in twins in England and Wales", Journal of Epidemiology and Community Health 45 (1991): 43-48.
 Michael R. Panicola, "Three Views on the Preimplantation Embryo", National Catholic Bioethics Quarterly 2.1 (Spring 2002), p.80; Agneta Sutton, "Arguments for Abortion of Abnormal Fetuses and The Moral Status of the Developing Embryo", Ethics and Medicine 6.1 (1990), pp.6-7; Helen Watt, "The Origin of Persons", in Identity and Statute of Human Embryo, Proceedings of the Third Assembly of the Pontifical Academy for Life (Vatican City, 14-16 February 1997), ed. Juan de Dios Vial Correa and Elio Sgreccia (Vatican City: Libreria Editrice Vaticana, 1997), pp.356-7.
 Aristotle offers a detailed analysis of how certain living creatures are structured in such a way that they can divide and produce two or more new individuals. Earthworms do this when they are cut in two. Plants often do this when producing off-shoots known as 'runners'. C.f. Kevin L. Flannery, S.J. "Applying Aristotle in Contemporary Embryology", The Thomist 67 (2003): 249-78.  Harris, 10-12.
 James P. Moreland and John Mitchell. "Is the Human Person a Substance or a Property-thing?", Ethics and Medicine 11.3 (Fall 1995): 50-51.
 Ibid., 54-5.
 John P. Doyle, "Reflections on Persons in Petri Dishes", Linacre Quarterly 64.4 (November 1997): 66.
 D. Alan Shewmon, "The ABC of PVS", in Brain Death and Disorders of Consciousness [Proceedings of the 4th International Symposium on Coma and Death], ed. Calixto Machado and D. Alan Shewmon (New York: Kluwer Academic/Plenum Publishers, 2004), 226.
 C.f. John Paul II, "Persons in 'Vegetative State' Deserve Proper Care" (Address to members of the Congress on 'Life-Sustaining Treatments and Vegetative State' (20 March 2004)), L'Osservatore Romano (English) 13 (31 March 2004), 5.
 Catholic Bishops' Conference of England and Wales. Cherishing Life (2004), 64.
 "Death can mean decomposition, disintegration, a separation. It occurs when the spiritual principle which ensures the unity of the individual can no longer exercise its functions in and upon the organism, whose elements, left to themselves, disintegrate" (John Paul II, "Determining the Moment When Death Occurs" (Discourse of John Paul II to the Participants of the Working Group on the Determination of Brain Death and Its Relationship to Human Death (14 December 1989)), Origins 19.32 (11 January 1990), n.4).
 In 1989 the Academy spoke of brain death marking the stage when integration of "functions is definitively abolished, even if some bodily functions like heart activity and respiration can be maintained artificially for a brief period of time" [emphasis added]. How the writers of this document would respond to later studies that show that a person can live many years (i.e. much more than 'a brief period of time') is unclear. It would seem that this would wholly contradict the scientific basis of the rationale they offered for accepting brain death criteria. (Pontifical Academy of Sciences, Working Group, "Final Considerations Formulated by the Scientific Participants", in Working Group on the Determination of Brain Death and Its Relationship to Human Death (Dec 10-14, 1989), ed. R.J. White, H. Angstwurm, and I. Carrasco de Paula (Vatican City: Pontifical Academy of Sciences, 1992), 81).
 Pius XII noted that while the philosophical and theological definition of death can be defined by the Church, and the general criteria (i.e. dis-integration of functions) that is implied can be indicated by the Church, to the question of which specific biological signs indicate death, "the answer cannot be deduced from any religious and moral principle and, under this aspect, does not fall within the competence of the Church". Similarly, John Paul II said that "the Church does not make technical decisions". Nonetheless, John Paul II noted that many in the medical profession held that brain death was a biological sign satisfying the definition of death offered by the Church, if so, they can use brain death criteria with 'moral certitude'. However, many scientists question the scientific veracity of the claim that the scientific data correspond to the philosophical definition of death held by the Church. (Pius XII, Pope. "The Prolongation of Life. An Address of Pope Pius XII to an International Congress of Anaesthesiologists" (24 November 1957), The Pope Speaks 4.4 (Spring 1958): 393-98; Pope John Paul II, "Cloning, involving the use and destruction of human embryos, is morally unacceptable" (Address to the 18th International Congress of the Transplantation Society (29 August 2000)), L'Osservatore Romano (English) 35 (30 August 2000): 1-2).
 The full papers of this conference have not been published. A summary of them has been published as: Paul A. Byrne, Cicero G. Coimbra, Robert Spaemann, and Mercedes Arz?a name="en31"> Wilson, "'Brain Death' is Not Death!" (Essay), The Catholic World Report (March 2005): 54-8.
 Such a dualistic notion of man might claim that a person is his brain, or that the soul is the form of the brain not the form of the whole body, or that a body without a brain cannot be apt matter for a rational soul. These are not notions readily compatible with orthodox Catholic thought, and are minority rationales for brain death. C.f. Descartes held that the soul was united to the body through the pineal gland of the brain. In contrast, Thomas Aquinas taught that soul is "in the whole body, and in each part thereof" and "is entire in each part thereof", i.e. it is not located simply in the brain or a part of the brain or a gland of the brain. Thomas explicitly rejects the notion that the soul is "only in the one part through which it would move the others" (Thomas Aquinas, Summa Theologica, Ia, q.76, a.8). C.f. The Church's teaching that the soul is the form of the body (Council of Vienna (1311-12), D481; 5th Lateran Council (1513), D738. C.f. D1655, D1914).
 Nicanor Pier Giorgio Austriaco, O.P., "Is the Brain-Dead Patient Really Dead?", Studia Moralia 41.2 (2003): 293.
 TK was still alive in 2003 at the age of 19 (Ibid., 292).
 D. Alan Shewmon, "Is It Reasonable to Use the UK Protocol for the Clinical Diagnosis of 'Brain Stem Death' as a Basis for Diagnosing Death?", in Issues for a Catholic Bioethic, ed. Luke Gormally (London: Linacre Centre, 1999), 323.
 D. Alan Shewmon, "The Brain and Somatic Integration: Insights into the Standard Biological Rationale for Equating 'Brain Death' With Death", Journal of Medicine and Philosophy 26.5 (2001): 473.
 It is possible to argue that the ventilator constitutes extraordinary care for a brain dead patient. Although the patient is truly a living person, the ventilator's permanent use is a treatment disproportionate to the gain that the patient achieves. Thus the ventilator may be removed. So argue William May, David Jones, and Shewmon. Dr. Paul Byrne is among those who disagree and argue that in the contemporary context a ventilator is no longer an extraordinary treatment. C.f. Shewmon, "Recovery from 'Brain Death': A Neurologist's Apologia", The Linacre Quarterly (February 1997): 83; William E. May, Catholic Bioethics and the Gift of Human Life (Huntington, Indiana: Our Sunday Visitor Publishing, 2000), 297; David Jones, "Nagging Doubts about Brain Death", Catholic Medical Quarterly 47.3 (1995), 7; Paul A. Byrne and Walt F. Weaver. "'Brain Death' is Not Death", in Brain Death and Disorders of Consciousness [op. cit], 48.
 Pontifical Academy for Life, "Prospects for Xenotransplantation: Scientific Aspects and Ethical Considerations" (2001), n.11.
 Tara L. Seyfer, "An Overview of Chimeras and Hybrids", National Catholic Bioethics Quarterly 6.1 (Spring 2006), p.49.
 Catechism of the Catholic Church, nn.2251-2. c.f. nn.2212, 2239.
 Cf. The teaching of the SCDF that to prohibit the abortion of the early embryo "it suffices that this presence of the soul be probable (and one can never prove the contrary)". SCDF Let Me Live: Declaration on Procured Abortion (1974), footnote 19.