While all persons (of the human kind) have a common entrance into existence, their exit
is of various, but still typical kinds. Some retain their rationality as long as their bodies
last, while others gradually loose the rational parts of their minds, and, as a limiting case, some end their lives as purely biological machines without any consciousness at all. In all these cases we will still think of our fate as something which happens to us, this does not only apply to those who retain their mental powers. But how literal shall we take our self-
ascription of these possible future stages of our lives? Clearly, I think of my death as
something happening to me, but my death at any rate is not a part of my existence. So,
can't we construe thoughts about a comatose existence as something happening to me in
the same manner? Yet, this is doubtful. We realize that we may consider it ethically
problematic to actively kill such a pure biological being, in contradistinction to cease to actively keeping it alive. And is not this because we still think of this kind of vegetative human existence as a continuation of the same individual who earlier on led a conscious
life? We may for two reasons accept this way of thinking. In the first place, we may appeal to an argument from symmetry. Just as we all start our existence on a purely
biological level, some of us end our existence in an equally vegetative way. So, since the former fact does not conflict with the zygote and the rational adult being parts of the same individual, why should we think differently about the relation between this mature person
and a vegetative sequel? Now, this argument from symmetry may appear weak, since a
vegetative exit of our existence is not a universal causal feature of persons, as their purely
biological entrance is. But there is a second argument. While the foetus and the baby merely are potential persons, we might say that even people permanently devoid of
conscious life towards the end of their existence actually retain their personhood in virtue
of having manifested the mental life characteristic of persons. Although those
manifestations are a bygone stage, the dignity, respect and concern which other persons
characteristically bestow on individuals who once developed into persons, are still there as
the remaining part of what it means to be a person. It is true that even dead people retain some of this respect, barring insensitive behaviour towards the body of dead persons. But
the kind of concern and even hope for an improvement bestowed on still living unconscious humans amounts to something more.
Limiting cases of personal identity just relying on bodily identity are clearly within
what is empirically the case. Limiting cases of the opposite kind are either purely
imaginary- being meant as imaginary, or at least highly controversial as to their causal
possibility. I am now thinking of cases where just psychological continuity is conceived to
secure personal identity. Among the first subgroup we find Lockean body-switches, like
those of the cobbler and the prince, or entrance of minds in new bodies while leaving
behind old bodies to die. We can also think of a person's body undergoing weird
metamorphoses, like what Kafka tries to imagine in his short-story about a man whose body is changed into a horrible insect. The second subgroup consists of imaginations of
post-mortem disembodied subjects. They can either, as all instances of the first subgroup,
be conceived as purely conceptual exercises, or as something more: as possible cases of
disembodied survival. However we personally conceive them, they point to a deeply
entrenched concept of a person in our culture, a concept which allows for diametrically
opposed limiting cases.- On the one hand, persons can survive as purely biological
machines and on the other hand as purely conscious minds, or at least as minds
imprisoned in bodies they were not born with. Persons are normally minds incarnated in a
permanent body, but they are not essentially so, and they are not even essentially actual
conscious minds. We can put it like this: Because psychological and bodily criteria of personal identity in normal cases both are so important, they can in limiting cases also
both serve as the sole surviving kind of criterion.