To: Steve D.
From: Geoffrey Klempner
Subject: Personal identity and body duplication
Date: 13 November 2003 11.23

Dear Steve,

Thank you for your e-mail of 4 November, with your first essay for the Possible World Machine, in response to the question, "What thought experiments concerning body duplication show is that the concept of personal IDENTITY is ultimately dispensable."

This is a thoughtful and intelligent piece of work. I recently saw 'The Sixth Day' on TV, and I agree that this film provides an excellent framework for discussing the problem posed by 'body duplication'.

First, a relatively minor point about strategy. It would have been better to start off with the Theseus ship case, because this serves to emphasize what is special about personal identity, namely self-consciousness and memory.

However, another point can be made about the Theseus ship case, concerning the role of 'sortal concepts'. (See Alfredo Lucero-Montano 'Artefacts and Persons' Philosophy Pathways Issue 63.) Under the sortal concept 'ship', we identify the ocean going vessel which has each plank removed and replaced one by one. Under the sortal concept, 'same wood' or 'same planks', we identify the wood, or the collection of planks which once made up Theseus ship, but now lie rotting in the shipyard. (These ideas originated with David Wiggins' monograph 'Identity and Spatio-Temporal Continuity' (Blackwell) which later appeared in his book 'Sameness and Substance', (OUP).) Similarly, although most of the human body is replaced during a seven year cycle, we have no difficulty identifying the 'same body' as the spatio-temporal continuant which persists despite the non-identity of its matter with the matter which previously constituted that body.

But how important is spatio-temporal continuity for human beings, given that memory plays such a crucial role? One criticism of the Lockean account of personal identity is that Locke provides no means for distinguishing 'true memory' from 'false memory'. If I woke up tomorrow convinced that I was Hitler, and was able to describe Hitler's last days in the bunker in remarkable detail, that still would not make me Hitler. From Locke's 'forensic' standpoint, I would not deserve to be punished for Hitler's crimes. Of course, we would look for some explanation. (Perhaps the 'Guava juice' I drank yesterday evening contained Hitler's mushed up brain cells saved by a mad Nazi scientist.)

What we require for personal identity is the *right kind* of causal connection between the original events and the putative 'memory' of those events. The problem, as the 'Sixth Day' scenario shows, is saying what constitutes the right kind of causal connection. Perhaps we want to say that when I drink the mushed up brain cells, there is still 'me' there. So what we have is not Hitler, but GK suffering severe psychological disturbance. Whereas if a 'fresh brain' in an Arnie-Adam clone is programmed with Adam's entire brain program, what we have *is* Adam, in the fullest sense of identity available. Not only do we have memory, but the causal connection is 'as good as' anything one could reasonably require of memory.

It remains true, of course, that cloned Adam's memory of saying goodbye to his wife is partially false, because it is false that *these lips* kissed hers etc. But it remains true that *he* kissed his wife.

You try various moves of Adam realizing and cloned-Adam not realizing, Adam not realizing and cloned-Adam realizing etc. I don't see how this can help with the problem of deciding who has the rightful title to Adam's identity, because it confuses the question of *what constitutes* identity with *how x knows* that the identity holds, or doesn't hold.

I agree with your suspicions that the film does go for the 'cop out' solution. Cloned-Adam is not 'as identical' (whatever that could mean) with the Adam before the cloning took place as the original Adam, so, despite the fact that he will miss 'his' wife and child he agrees to go off to Patagonia. But this is nonsense if what we have said above is correct. The right kind of causal connection is all it takes for identity, so being the 'original body' ought not give you any special privileges.

However, we have not yet answered the question.

Is the concept of 'personal identity dispensable? This is in fact the conclusion reached by Derek Parfit in his book 'Reasons and Persons' (OUP). Suppose that human cloning became fully acceptible. Let's say Tony Blair is faced with a crisis that requires two Tony's. Of course once you have two, you can't go back without committing murder. Now we have to deal with a straightforward logical problem that the three propositions A=B and A=C and not-(B=C) generate a contradiction. A year (or even, as I would argue, a second) later Tony(2) is a different person from Tony(1). Yet Tony(2) *is* the original Tony just as much as Tony(1).

Parfit says that in the face of this we should be prepared to give up the concept of 'identity' in favour of 'psychological continuity'. To say that Tony(1) and Tony(2) are psychologically continuous with the original Tony does not generate a contradiction.

I prefer the alternative response (originating from David Lewis) that the act of duplication brings makes it true that before the duplication here were two 'Tonys'. Or, less paradoxically, that in view of what we know now, the original Tony turns out to have been part of two 'lives of Tony'. This in fact does more justice to the memories of Tony(1) and Tony(2). When Tony(1) says, 'I was elected leader of the Labour Party' and Tony(2) says 'I was elected leader of the Labour party', both statements are true.

All the best,

Geoffrey