To: Christopher J.
From: Geoffrey Klempner
Subject: Thought experiment of human body replacement
Date: 21 August 2007 12:31

Dear Chris,

Thank you for your email of 13 August, with your second essay for Possible World Machine, in response to the question, 'Imagine you are Michael Harding. As you lie injured on the road, you are told that a brain scanner is going to be used to map your memories and personality, and the information used to program the brain of a new body cloned from one of your own cells. The moment the new ‘you’ gains consciousness, the old ‘you’ will be painlessly destroyed. How do you feel about that prospect? – Justify your answer by reference to one of the competing philosophical accounts of the relation between mind and body.'

In your essay, you appear torn between wanting to say that a 'person' is nothing but a 'social construct, a fiction' and the intuition that an original of any entity x can only ever be the original, and a copy can only ever be a copy.

On the basis of the view of persons as social constructs, the identity of 'Mike Harding' is decided by the criteria - the necessary and sufficient conditions - for the identity of things of that kind, i.e. identity as a construct. As a construct, MH2 is 'Mike Harding' in virtue of being the best candidate, compared with the only competitor, recently deceased MH1. A human body can be dead, but a 'person' by definition cannot (except in the historical sense in which we say, 'Napoleon is dead').

On the basis of the view that a copy is necessarily non-identical with an original, on the other hand, there is simply no possibility that MH2 could be 'Mike Harding'. When MH1 dies, Mike Harding dies. MH2 is an impostor, notwithstanding the fact that he sincerely believes that he is the 'real' Mike Harding.

How are we to resolve this dilemma? The background to this question is the rejection of the dualist conception of personal identity. Our concern is purely and simply with giving a coherent set of criteria for personal identity, consistent with materialism, and applying these to the problem case in question.

There is one option which you seem to be prepared to consider, that the only 'true' self is the consciousness that we all have in common. This seems to be Derek Parfit's view in 'Reasons and Persons' and constitutes the basis for his argument for an ethics based on utilitarianism. The concept of 'person' is less 'important' than we believe it to be, and indeed our obsession with 'being persons' provides a major stumbling block in the way of morality. Subjects who have successfully cast aside their personalist prejudices are more likely to behave ethically because they take a disinterested perspective.

However, this debate can be bracketed for our purposes. Faced with the imminent prospect of death, it is difficult not to feel that one's personal identity is an issue of some importance. Even if inspired by Parfit one succeeds in discarding such feelings, it remains a legitimate question how the criteria for personal identity are best applied to the present problem case.

What is it to be an 'original'? Originality is a matter of spatio-temporal continuity. Let's say I accidentally break my aunt's precious Ming vase. A perfect atom-for-atom copy looks as good but it isn't the original. Even if I succeed in covering up the subterfuge, the original is gone.

However, with persons we have an additional factor to consider. Personal identity, according to the best available account, involves continuity of that which is causally necessary and sufficient for memory (this is basically the view of David Wiggins in his book 'Sameness and Substance'). Herein lies the main deficiency of Locke's account, which is unable to offer a criterion for distinguishing genuine memories from true but non-genuine memories.

Continuity of the material basis for memory is not necessarily continuity of a lump of matter, provided that we are able to identify a legitimate causal route which preserves all the necessary information (hence the 'Star Trek' idea of 'beaming down'). However, this allows for the following possibility, as described in the story of Mike Harding: MH1 is alive in the broom cupboard while MH2 is alive in the hospital bed. According to the best available criteria, a 'legitimate causal route preserving all the necessary information' exists for both MH1 and MH2.

Now, there are cases where we would be prepared to say that both 'are' Mike Harding, in other words that there are now two genuine Mike Hardings. For example, suppose Mike Harding stepped into a booth, which caused a symmetrical split down the middle from which two MHs emerged. However, the present case is not like this because there is a marked asymmetry. MH1 seems to have a greater claim to be the 'real' Mike Harding than MH2. Other things being equal, one would like to say, material continuity is the 'best kind' of causal route (as illustrated by the vase example).

But remember that we are only talking about a 'social construct'. Let's push the difference between MH1 and MH2 a bit more. Say, MH1 has a mental breakdown when he discovers that all four limbs will have to be amputated, or that a brain injury has wiped some but not all his memories, so that he no longer recognizes his family and friends. In that case, MH2 begins to look an increasingly attractive candidate for being the 'real' Mike Harding.

All the best,

Geoffrey