It cannot be known for sure in advance whether a zygote, an embryo, a (postembryonic) fetus or a baby is the living body of a preexistent person. If no member of the animal species concerned ever develops into a person, it may be said that it is not the living body of a potential, let alone a preexistent, person. But if the fetus or baby belongs to an animal species of which the members normally develop into persons, it may be said that it probably is. As a living, or happiness-catenal, being there is no difference between the one fetus or baby and the other; the difference lies in its relation to personhood. Yet, the fetus or baby which is to develop into the body of a person at a later stage, is not (yet) a person itself, and not even the body of a person.

Traditional antiabortionists have claimed that the fetus in a human mother is a human being or a potential human being; and rightly so. Every fetus is a being belonging to the same species as that of the parents (granted that the parents are members of the same species, and that no important mutation has occurred). This is not typically human, and there is nothing typical about being human or potentially human in this respect. As a (potential) human being the human fetus is a living being, an animal being and, perhaps, a happiness-catenal being, not a fetish with the magical power of membership of an exclusive club. The traditional antiabortionist argument that the human fetus would be a person with its own right to life is, naturally, nonsensical. Or, if person is used as a mere synonym of human being, it suffers from the same speciesism as in the former reasoning. More interesting tho, is the claim that the human fetus is a potential person. This is the claim that it is possibly the living body of a preexistent person.

If abortion were wrong because a person who had existed in the future will not exist 'anymore', then this would also make contraception wrong -- as has been pointed out. And contraception would not only be wrong, it would be equally wrong, something the antiabortionists would probably not have intended (except for those methods of contraception not preventing fertilization but causing the rejection of fertilized eggs, which are indeed techniques of very early abortion). When the reply is that the fetus is a potential person that has already started its existence, the problem is why terminating the process would be wrong at this stage and not at a previous stage. (As one human being conceived: 'if it is the cake you are interested in, it is equally a pity if the ingredients were thrown away before being mixed as after being mixed'.) This antiabortionist position is but one remove from both spermatism, the belief that the human spermatozoon contains all properties of a new human being, and ovism, the belief that a new human being is already formed in the ovum before being fertilized by the male's sperm. The antiabortionist might now rejoin that it is precisely the absurdity of both spermatism (with its obsession about and fear of the masturbation of male humans) and ovism which justifies 'er drawing the line at conception or the fertilization of the ovum. But this moment is not necessarily the moment that a new, individual human being starts its life either, because one fertilized egg may still split up later, or two eggs may still combine. Moreover, even the fertilized egg which does not split up or combine (anymore) is not an individual human being if the prerequisite for being an individual, or whole, living being is the capacity to survive outside the body of another living being.

The difference between the new (potential) human being and the separate ovum and spermatozoon is one in the packages of genetic information. This is a purely biological difference, and from the perspective of potential personhood it is not relevant whether the body of a person or potential person has the same genetic information as that of a particular woman, as that of a particular man, or a mixture of both; the reproduction might as well be metagenetic. What counts is that if viability, that is the capacity to survive and function outside a mother's or father's body, is not a criterion of potential personhood, this applies to both the zygotes, or other inviable fetuses, and the gametes of the human, or other animal, species.

Viability of the body cannot be a necessary criterion of personhood (and of potential personhood), for it would mean that a person whose body had become inviable on its own had to be denied personhood even tho this person would clearly have and express 'er own ideas about life or other matters. If the only way to keep someone alive were by plugging 'er body into another body, even if permanently, the person concerned would still be a person despite 'er physical dependence. Now, if viability cannot mark the end of personhood, it cannot mark the beginning of it either. Moreover, viability is a shifting boundary: because of medical developments the zone of probable survival of a fetus has been moving back further and further. Once it is possible to fertilize eggs and produce children entirely outside the womb the boundary of potential personhood has moved back to the individual ovum and spermatozoon, or their potential combination.

Inclusivism urges us to respect not only both living and nonliving things, both human and nonhuman beings, but also both personal and nonpersonal beings. The DNI does not know a doctrinal principle of the sanctity of life as such, of human life as such, or of personhood as such. The significance of personhood derives from the metadoctrinal principle, but it does not follow that potential personhood is of any value in itself; a being simply has extrinsic rights and duties or does not have them, and only persons have these rights and duties, not their bodies. That a being will have extrinsic rights and duties becomes important later on; that it did have them was important before. Another way to put it is: a potential person may have potential rights (and duties), it does not have actual rights (and duties). The potentiality criterion is logically erroneous. A potential president, for instance, does not on that account have the right to preside over a meeting, nor does anyone on that account have a duty to obey 'er instructions. Person A who may now be the president of country B, did not have any right as a president, or as a potential president, when 'e was still a baby, nor did anyone have any duties towards 'im as a president, or as a potential president, at that time.

Given that only actual possession of the characteristics of personhood may justify a direct difference in treatment between living, animal or human beings, we must treat the living bodies of preexistent or potential persons in the same way as all other living beings, or as all other happiness-catenal beings of the same happiness-catenary type, unless there is a significant difference in side-effects. Such side-effects have been stated as a reason to differentiate between nonconception and abortion: the effects of an abortion on the mother, the father, the surgeon(s), the nurse(s) and all others involved are quite different from those of a nonconception, particularly when the abortion takes place at a later stage. Moreover, abortion is a form of deliberate killing, and unlike nonconception it might thus make it easier for people to kill living, happiness-catenal or human beings in general. This argument can only be taken seriously, however, if it is put forward by people who also apply it to the killing of other human beings (for example, by or for the state) and to the killing of living or happiness-catenal beings of the same or a more developed type (for example, for food or hunting).

While side-effects are important to distinguish our attitude towards abortion from that towards nonconception, they are still more important to distinguish our attitude towards infanticide from that towards abortion. There are first the side-effects for those closely affected. Yet, where the effects of having to kill a neonate may be very bad to them, the effects of having a child, and of rearing a child, which is radically deformed may be much worse. Then there are the social effects of allowing infanticide, even if only in exceptional cases. It is here that we are confronted with the 'slippery slope' or the 'wedge problem'. Arguments using the image of the slippery slope or wedge are not only put forward in the case of infanticide but also in cases of killing animals for food and in cases of euthanasia, especially active euthanasia. Theorists distinguish a logical and a psychological or empirical version of such arguments. The logical version is that if accepting the thin end of the wedge is justified, the rest of it cannot be rejected anymore, because a cut-off point somewhere between the two ends would always be arbitrary. But it has been rightly argued that this interpretation fails, for altho there may be a field of uncertainty to which carefully formulated moral principles cannot be applied with precision, such does not mean that the fuzzy border between what is allowed and what is not allowed could lie anywhere. (We do not have to choose between a ban on all motorized traffic and a system in which people are permitted to drive at any speed anywhere. Altho there may not be a precise justification for a particular speed limit in, for example, a residential area, we know that certain limits would be too low and that other limits would be too high.)

On the psychological version of wedge arguments it is claimed that in fact more and more of the wedge will follow once the thin end is allowed to be inserted. This claim is empirical, and as such not one for a normative doctrine to validate or invalidate. As a general claim it is not convincing, however, for --as has been pointed out elsewhere-- many people also start to drink without ending up as alcoholics. (And is working wrong because some workers end up as workaholics?) Nevertheless, the strength of the psychological version of the wedge argument against infanticide is that the sharp boundary of birth is removed by moving from abortion to infanticide as a form of killing which may be warranted under specific circumstances. The crucial question has now become where to draw the line between an infant without any of the characteristics of personhood and an older individual with the minimum characteristics of personhood. It has been said that the whole complex of traits which make up personhood would not obviously be present until the second year of childhood, and this would imply that the killing of babies in their first year were no violation of their extrinsic rights. In spite of this it may be a serious violation of their intrinsic rights as living and happiness-catenal beings. On the other hand --as has already been pointed out too--, not killing or letting a neonate or fetus die which is (probably) going to be severely deformed may be an equally serious violation of its intrinsic rights. That is why to religiously strive to keep alive radically deformed human babies, while allowing healthy adult human beings (such as young men in warfare) or sentient beings (such as animals for food) to be killed at the same time, makes a complete mockery of the whole idea of the value of life.

What the body of a preexistent or potential person has in common with living beings which are in no way related to personhood is that there is no person who has this body and who can decide on its use, or who has decided on its use. This condition is quite different not only from that of the bodies of living persons but also from that of the bodies of dead persons. People cannot decide during their lives what must not have been done to them (or rather to their bodies) as fetuses or as infants, but they can decide during their lives what must not be done to them when they will not be in a position anymore to have or to express their own wishes. This is important when their personhood has terminated, that is, when they are dead as persons, but when their bodies are still alive or kept alive. Such a body of which, for example, the heart is still beating but the brain no longer functioning, is then only a living being like all other living beings if the person who died never expressed what should be done to it, or if 'e did lay down 'imself that it should be treated as any living thing of the same category of life. In the event that the dead person's living body does not survive in a happiness-catenary state, it should be treated as a non-happiness-catenal living thing, and in the event that it does, as a happiness-catenal being of the happiness-catenary category concerned, unless the body is under the posthumous influence of the person who had it. If the actions to be taken with respect to this body are affected by the dead person's will, the relationship in question is not really one between a person acting and a nonpersonal living thing but one between several people. It is the role of this kind of relationship in matters of life and death to which we will now turn.