Aaron Sloman
(At The University of Birmingham, UK, since 1991).
In his recent Aristotelian Society paper ('Personal identity, personal
relationships, and criteria' in Proceeding of the Aristotelian Society,
1970-71, pp. 165-186), J. M. Shorter argues that the connexion between
physical identity and personal identity is much less tight than some
philosophers have supposed, and, in order to drive a wedge between the
two sorts of identity, he discusses logically possible situations in which
there would be strong moral and practical reasons for treating physically
discontinuous individuals as the same person. I am sure his main points
are correct: the concept of a person serves a certain sort of purpose and
in changed circumstances it might be able to serve that purpose only if
very different, or partially different, criteria for identity were employed.
Moreover, in really bizarre, but "logically" possible, situations there
may be no way of altering the identity-criteria, nor any other feature of
the concept of a person, so as to enable the concept to have the same
moral, legal, political and other functions as before: the concept may
simply disintegrate, so that the question 'Is X really the same person as
Y or not?' has no answer at all. For instance, this might be the case if
bodily discontinuities and reduplications occurred very frequently. To
suppose that the "essence" of the concept of a person, or some set of
general logical principles, ensures that questions of identity always have
answers in all possible circumstances, is quite unjustified.
Shorter's examples (op. cit., p. 169, ff.) involve situations in which
it is fairly common for two people suddenly to exchange mental and
physical characteristics: where Mr. A was a moment ago we now find
someone who looks, feels, behaves, thinks, etc., exactly like Mrs. B,
and vice versa. Despite any temporary embarrassments, it would surely be
most sensible and morally justifiable, in the long run, to say that Mr.
A and Mrs. B had suddenly changed places, rather than that they had both
suddenly undergone strange and distressing transformations, while
remaining where they were. Shorter seems to think that this shows not
only that physical continuity is not required for personal identity, but
also that bodily identity is not required for personal identity.
However, the latter follows only if bodily identity requires physical
continuity, and Shorter's own pattern of argument might be used to
undermine this: there might be good practical reasons for saying that
two bodies (e.g. Mr. A's and Mrs. B's) had suddenly changed places
rather than that each had suddenly changed its shape, for example. I
wish now to describe, without much comment, a possible situation in
which this loophole in Shorter's discussion is closed. In my example
both physical continuity
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and bodily identity are clearly separated from personal identity. Moreover,
it does not, as Shorter's apparently does, assume the falsity of
current physical theory.
Whether human bodies are physical systems is an empirical question.
Although many aspects of the physics, chemistry and engineering of human
bodies are still hardly understood, it is at least clear that all the
substances of which human bodies are composed are themselves composed of
physical elements which can exist in inanimate matter. What is not so
clear, is whether every physical change, including movements, occurring
in a human body conforms with the laws of physics (which, in view of
quantum theory, is not to say that every such event has an explanation).
No known processes or events in human bodies are known to be
incompatible with current physical theory, but some might turn out to
be. However, for the sake of our conceptual investigation let us accept
the empirical assumption that all physical and chemical processes in
human bodies conform to current physical theory, or at least something
like current physical theory. In that case, if my body were suddenly
duplicated in all its detail, down to the last sub-atomic particle, then
all the physical processes in that body thereafter would be-similar in
character to the processes in mine, and consequently the observable
behaviour of the new body, including facial expressions, verbal
utterances, and all the other details which matter in personal
communication, would be exactly the same as in mine except for the
differences arising out of subsequent physical inputs and the
differences permitted by quantum indeterminacy.
We already have machines which can transcribe a pattern of molecules
from one magnetic tape to another with sufficient fidelity for most, if not
all, listeners to be unable to tell whether they are listening to the "master"
tape recording of a symphony concert or a copy. It seems to be at least
logically possible that one day physicists will construct machines with
still more spectacular reproductive capacities. Place your watch in box
A, make sure the machine has the requisite supply of power and chemicals,
then, when the green light shines another watch exactly like yours will
be found in box B. The watches will probably not behave exactly alike
forever, since the margin of indeterminacy in current physical theory and
different subsequent treatment will allow differences to emerge: but if
the original was very well made these differences should prove slight.
Similarly when the machine is developed, after about a hundred
more years, so that it can duplicate human bodies: granted the
afore-mentioned empirical assumption that human bodies are physical systems,
then, although there may be very slight differences in the behaviour of
the two persons stepping out of boxes A and B, these will not suffice to
enable anyone, not even his nearest and dearest, to distinguish the
original from the copy.
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Notice that if the copy always turned out to lack some important
feature of humanity, or to be different in intelligence or personality from
the original, this would be evidence (though inconclusive) against the
hypothesis that all the physical behaviour of human bodies conforms to
physical theory. But we are assuming this does not occur.
Of course, the use of the transcriptor to multiply persons beyond
necessity could cause dreadful moral, social, political and economic
problems. However, a modified version of the machine might be very
useful, and quite justified morally, as we shall see.
It will be a long time before engineers make a machine which will not
merely copy a tape recording of a symphony, but also correct poor
intonation, wrong notes, or unmusical phrasing. An entirely new
dimension of understanding of what is being copied is required for this.
Similarly, it may take a further thousand years, or more, before the
transcriptor is modified so that when a human body is copied the
cancerous or other diseased cells are left out and replaced with normal
healthy cells. If, by then, the survival rate for bodies made by this
modified machine were much greater than for bodies from which
tumours had been removed surgically, or treated with drugs, then I
should have little hesitation, after being diagnosed as having incurable
cancer, in agreeing to have my old body replaced by a new healthy one,
and the old one destroyed before recovering from the anaesthetic. This
would be no suicide, nor murder.
I expect my family and friends would be pleased with the outcome.
So would the families and friends of other incurably sick persons, except
perhaps the impoverished surgeons. Because of the moral and practical
benefits (who's going to quibble about spatio-temporal continuity when,
in place of the ailing and helpless patient carried to hospital on a
stretcher, the hale and hearty substitute walks in?), the business could
well grow, until it became quite reasonable to say 'I'm going to hospital
next week, to get a new body', or 'I like my new body much better than
that sick old one'. Surely this is a simple extension of what makes it
reasonable to say 'I'm going to get a new heart', or 'I much prefer this
new trachea they've given me'. (As Shorter suggested, in commenting
on the first draft, various intermediate cases between a new heart and a
whole new body can be envisaged.) However, this way of speaking
could only be tolerated if the original bodies were destroyed, or at least
somehow kept out of circulation. Many, more or less macabre, variations
on this theme, illustrating different points, are easily envisaged.
It might, of course, turn out on analysis that this concept of a perfect
physical transcription machine, or its modified version, is incompatible
with some aspect of modern physical theory. Indeed this is more than
likely. However, that would show that my little story is physically
impossible, not that it is logically impossible. Its advantage over
Shorter's, apart from its resistance to the comment that there's no loss of
bodily identity, only change of place, is then simply that its physical
impossibility is less obvious.
University of Sussex.