Identity
McMahan considers four different candidates for the identity of persons/human beings:
(1) A person/human being is (i) a soul or (ii) a compound unity of soul and body
(2) A person/human being is a human organism
(3) A person/human being is a psychological being
(4) A person/human being is an embodied mind
He rejects (1)-(3) and defends (4).
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(1) (ii) A person/human being is a compound unity of soul and body
Hylomorphism (from "hyle" (body) and "morphe"(form))
This is the position that the matter that makes up the body has a certain form or "organizing principle" that is called the soul. Thus a soul is not a separate substance, on this account; it is just the way that the matter is organized. Matter that is organized in a certain way is a person/human being.
Note that on this account a person/human being is not a soul. Here "the soul is just the inherent organization of the matter of the body in a distinctive way, so that the matter constitutes an individual of a particular sort" (p. 13).
A person/human being is an material body organized in such a way that he/she/it has certain capacities and powers (e.g. consciousness). On this account, there cannot be such capacities without the material body, since it must be organized in a certain for those capacities to exist.
Aquinas (following Aristotle) identified three types of soul:
(1) Vegetative or nutritive soul (plants)
(2) Animal or sensitive soul (animals)
(3) Rational soul (persons/human beings)
Aquinas accepted the principle of "immediate animation", that is, that the zygote is alive, or that there is life at conception. However, he believed in "delayed hominization", that is, that a person/human being is not present at conception, or that a zygote is not a person/human being.
The zygote passes through two stages, namely, a vegetative stage and an animal stage, until it finally there is a rational soul (but this must be directed infused by God), in which case there is a person/human being. This "hominization" takes place after 40 days in the case of men, and after 90 days in the case of women. (Aquinas took this from Aristotle, who accepted anecdotal reports of movements in the womb in the case of male and female embryos and fetuses).
Some contemporary versions of hylomorphism, however, endorse what we may call "immediate hominization", i.e. that there is a person/human being present at conception, or that a zygote is a person/human being.
However, there is a problem with immediate hominization for contemporary versions of hylomorphism. In the case of a zygote, there is simply a single cell. How is it possible to hold that this single cell is "organized" in such a way that he/she/it has the various capacities that are normally deemed necessary for being a person/human being? Such a cell may indeed have capacities, e.g. the capacity to divide. But does it have any capacities that are normally deemed necessary for being a person/human being?
Note that having a capacity is different from having the potential to have the capacity. A capacity is such that it can be exercised, i.e. the zygote can be it or do it. In the case of division, for example, the zygote has the capacity for division, i.e. the zygote can divide. A capacity for consciousness would be a capacity such that it can be exercised. So if the zygote has a capacity for consciousness, then the zygote can be conscious.
In order for there to be a capacity for consciousness, however, it appears there must be structures in place that are causally involved in the exercise of consciousness. It appears false that a zygote has such structures. Hence, it appears false that a zygote has the capacity for consciousness.
Indeed, if the list of capacities that are normally deemed necessary for being a person/human being is considered (consciousness, having interests, having feelings, etc.), it appears false that this single cell is "organized" in such a way that it he/she/it has any of the various capacities that are normally deemed necessary for being a person/human being. Hence it appears false that a zygote is a person/human being.
Hence, it appears that contemporary hylomorphism fails to establish "immediate hominization", the position that there is a person/human being present at conception, or that a zygote is a person/human being.
Note that one could argue here that "person" is more demanding than "human being", and that a zygote is a human being even though he/she/it lacks many or all of the capacities required for being a person, and is not a person. Or one could argue that a zygote is a person although he/she/it lacks many or all capacities required for personhood.
Alternatively, one could argue that a zygote does indeed have some or all of the capacities required for personhood, even though none of them are exercised. On this account, e.g. the zygote does have the capacity for consciousness, even if it is not exercised, and thus, even if the zygote is not conscious. Indeed, even if no zygote ever does exercise the capacity for consciousness, and hence, even if no zygote is conscious, then nevertheless, each zygote has the capacity for consciousness. On this account, it is either false that there must be structures in place that are causally involved in the exercise of consciousness, or else, that the zygote does indeed have these structures (and hence that much less is needed than is normally thought to be needed in order to have the capacity for consciousness).
One might argue against this position by arguing that why, if every zygote has the capacity for consciousness, does he/she/it never exercise it, and thus, is never conscious?
The defender could say: he/she/it it has the capacity, but other conditions are not satisfied (say, no inputs from sense organs), and hence, the capacity is never exercised, and hence, he/she/it is never conscious. This is not in itself a problem. (Human beings might have the capacity to do something that they never do because the conditions are never right.) The only possible problem with this position is: how can we know that something has a capacity that is never exercised? How can we know, for example, that a zygote has a capacity for consciousness that is never exercised, and hence, that a zygote can be conscious but that it never is conscious? But this is not necessarily a problem for the defender of this position. The defender can simply say: we believe this on the basis of faith, because it is revealed to us in the Bible, etc. The position itself -- that a zygote has the capacity for consciousness that is nevertheless never exercised and hence that a zygote is never conscious -- is entirely consistent. Furthermore, it can be argued consistently that a zygote has every single capacity that is normally required for he/she/it's being a person/human being, but that none of them are ever exercised, and hence, that a zygote is not conscious, does not have feelings, etc., even though it can be all of these things.
One problem for this position, however, is why we might not likewise argue that e.g. plants, or rocks, have a capacity for consciousness that is never exercised. The disadvantage here is that at least the defenders of the position can point to the fact that a zygote can develop into an organism that both has a capacity for consciousness and also exercises that capacity for consciousness, and hence, is conscious. This is not true of plants or rocks.
However, there is one final problem for a different (moral) position that is often connected to this one. It is often said that since a zygote has the capacity for consciousness, whereas other things (e.g. plants) do not, a zygote must be treated in a special way. For example, one morally ought not to kill (etc.) a zygote. However, if a zygote is not conscious (no more than a plant), but only has the capacity for consciousness that is never exercised, then why must the zygote be treated in any special way? Again, however, the defenders of this position can argue that they are not saying merely that a zygote has the potential to have the capacity for consciousness. Rather, the zygote actually has that capacity; it is just that he/she/it cannot exercise it. For some reason, exercise of the capacity is somehow not possible. But, they can argue, the zygote has a property -- the capacity -- that is not possessed by other things and that this entails that he/she/it must be treated specially.
Of course, it the defender also argues that the zygote has e.g. the capacity to be self-conscious, know right from wrong, etc., then it may turn out that the zygote is different in kind from all animals as well as plants and inanimate objects, and hence, that it deserves very special treatment indeed, even if he/she/it is never self-conscious, never knows right from wrong, etc.
(1) (ii) A person/human being is a soul
Cartesian Soul (from Renč Descartes, 17th century French philosopher)
This is the position that a person/human being is a nonphysical entity, namely, a soul, that is conscious or thinks. (For Descartes, the soul is always conscious or thinking, even if the soul does not remember this. When one is asleep, for example, one is conscious or is thinking. It is not possible for a soul to be 'unconscious', if that means not having thoughts.)
Note that on this account, a soul "uses" a brain and the rest of the body, but can exist in a disembodied state, thinking. Hence a body is not necessary for the existence of a person/human being. A soul is sufficient.
On this account, a soul is always conscious even if there is no psychological continuity (e.g. severe Alzheimer's Disease). There can simply be continuity in the existence of the soul (substance), which is always thinking in some form, even if the thoughts at one moment are not psychologically connected to thoughts at another moment.
According to Descartes, the soul is created by God at a certain point in time, and is at this same moment united to a body; he/she/it remains united to a body for a period of time; he/she/it parts from this body after a certain period of time, but continues to exist indefinitely so long as God chooses not to annihilate the soul (i.e. he/she/it is, or can be, immortal).
(Note that other non-Cartesian theories hold that souls are eternal, or at least that that they exist before the creation of particular bodies, and are united with them for periods of time before parting with them again; also, according to some theories, this process is continued indefinitely (i.e. reincarnation)).
Descartes held that "even in the mother's womb" (p. 16) the soul is conscious. (Well, the soul is not "in" the womb). That is, even when the soul is united with a zygote he/she/it is conscious. (Actually, Descartes appears to go further and claim that even in the womb the soul is self-conscious !)
Note that this claim -- that even when the soul is united with a zygote he/she/it is conscious -- is completely different from the claim that the soul has the capacity for consciousness which it does not exercise while it is united with a zygote (and hence, that the soul is not conscious when he/she/it is united to a zygote.) Rather, it the position that the soul has a capacity for consciousness that he/she/it is always exercising. However, this entails that the soul is conscious when he/she/it is united with a zygote. This position entails that:
(1) The soul united with a zygote is conscious, but is "locked in", such that this conscious activity is not or cannot be detected, at least by any normal means;
(2) Later the soul suffers amnesia about this period in which it was united to a zygote and conscious.
In the contemporary version of Cartesianism, the soul has the capacity for consciousness at this point, although the body (the zygote) is not sufficiently developed, and hence, the capacity cannot be exercised. Thus, on this account, the soul is unable to be conscious while united with a zygote.
On this account, however, it is not clear why it is not also true that after the death of the body, the soul goes back to merely having a capacity for consciousness without being able to exercise it, and is unable to be conscious (say, in the afterlife). Alternatively, if the soul may be conscious in the afterlife without the body, then why may it not also be conscious while united with a zygote? If it can exercise the capacity later, without a body, why not earlier, without a body?
There are many problems with Cartesian Souls:
(1) Thinking or consciousness is what a soul does; but what is a soul? Souls tend to be defined in terms of what they are not -- not a body, not mortal, not in space, not in time. They appear to be 'featureless'. They are, simply, things that think or are conscious.
(2) How do souls interact with bodies, and vice versa? In particular, how does it happen that thinking or consciousness is affected by alcohol, damage to the brain, etc., if the soul is not the body?
(3) If animals are not souls, then are they not conscious? (Descartes claimed that they were not conscious.)
(4) Monozygotic twinning. The body divides into two bodies. What happens to the one soul?
(5) Division of consciousness as a result of commissurotomy. There are now two centers of consciousness. Does this entail that there are two souls?
The following are responses to the possibility of monozygotic twinning on the part of Cartesianism:
(a) A soul divides into two new souls, and the previous soul goes out of existence. So "twinning is tragic" (p. 19)
(b) Soul does not divide. It now unites with just one of the twins. Then either a new soul is created for the other twin, or the other twin is a soulless entity, not (never) a human being/person (this twin is not (never) conscious; it is no more than a non-thinking animal)
(c) God anticipates the twinning and implants two souls in the zygote. When twinning occurs, the souls unite with the respective twins.
If consciousness does not begin until well after conception, and in particular, until well after the period in which monozygotic twinning can occur, then the position would have to be that "When twinning occurs, only the physical embryo divides. Both resulting fetuses receive souls later on."
These are no knockdown arguments. However, there remains the problem of Division.