To: Max W.
From: Geoffrey Klempner
Subject: Personal identity and exchanging bodies
Date: 5th November 2010 12:04

Dear Max,

Thank you for your email of 27 October, with the corrected version of your essay for the University of London Diploma Introduction to Philosophy module, in response to the question, 'Do you think it possible that one person could exchange bodies with another? Relate your answers to Locke or Williams or both.'

Let's start with aspects of the problem which don't really get to the core of the question. You note the practical difficulty involved in exchanging bodies, on the assumption that there is a material basis to consciousness. We know that much more than just a functioning brain is involved. It is indeed very likely that the very idea of removing a brain and putting it in another body is a science fiction fantasy which bears no relation to the scientific facts. (The same applies to thought experiments like the 'brain in a vat'.) The brain doesn't have a 3-pin connection (or even a 3000-pin connection) that you can just plug in to the spinal cord.

I think that it is worth noting this point, before moving on.

It wasn't clear to me that you had fully understood Locke's view of personal identity. Locke argues that the concept of a person is necessarily bound up with our notion of the criteria for personal identity. And, moreover, the concept of a person is 'forensic', in the sense that what concerns us is all that is necessary and sufficient for attributing personal responsibility, moral praise and blame etc. So sharply focused is his view of personal identity that he takes the extraordinary step of denying that the identity of a non-physical soul, whose presence we can never (ex hypothesi) detect is completely irrelevant to personal identity. If you and I switched souls, and your soul thereby acquired my memories and my soul acquired yours, then we would be totally unaware of the fact. It would be irrelevant to our respective identities as persons.

Locke is not committed to any particular view of what it is that accounts for consciousness and memory. He is simply reporting what anyone can observe for themself, that their sense of self is bound up with memory.

Consider the Prince and the cobbler, or, better still, the prima ballerina and the and the dying man. Make the difference between bodies and external circumstances as extreme as you like: we seem to be able to *imagine* what it would be like to wake up with a body that was not ours. What happened after that, the violent changes that this would wreak to our personalities is another question. Personal identity is consistent with even drastic change. As Locke would argue, so long as the thread of memory and consciousness remains, then the person is one and the same.

In any case, the question asked whether it is possible that one person could exchange bodies with another. If the answer is 'yes' in a few very restricted cases (say when we are dealing with twins, or persons whose bodies and physical abilities are similar) then it is yes. Even if it could be argued that it is not *always* possible to exchange bodies, it could still be the case that it sometimes is possible.

Questions relating to the self and the future, as opposed to the self and its memories, can be very confusing and Williams exploits this in his thought experiment of the anticipated torture. Suppose you are told that your memory and consciousness will be transplanted (say, by being uploaded onto disk then downloaded into a fresh brain), but that there will be two recipient brains, not one. The owner of the first brain will be tortured and the owner of the second will go on a luxury cruise. Can both the recipients be 'you'? Or, if not both, then one but not the other (only we don't know which)? How does one decide?

What this seems to show is that if we are prepared to go to the lengths of considering transplanting a 'person' into another body, what we would be giving up along the way is the last meaningful link to the idea of identity as opposed to mere similarity. The capacity to remember is a function, a property, which can be exemplified by more than one entity.

Insisting on the spatio-temporal continuity of that which is causally necessary and sufficient for continuity of memory and consciousness would be one way to resist the consequences of Locke's view. It does at least provide us with a criterion for 'true' memory as opposed to 'fake' memory (e.g. the person who 'remembers' being Marie Antoinette). But it won't do because the physical stuff itself -- brain stuff or whatever -- could in principle be divided any number of times between a corresponding number of new bodies.

One possible conclusion from this is that the very concept of a 'person' depends on particular empirical circumstances in such a way that, were those circumstances to change sufficiently, we could no longer have that concept. As Williams argues elsewhere, the name 'Max W' could become like 'Ford Capri', a general term or universal. When we imagine a person 'exchanging bodies with another' we wrongly assume that the concept of a 'person' is immutable, like a Cartesian soul substance that can be put here or put there. Whereas, if this happened in reality, persons as we know them would have ceased to exist.

All the best,

Geoffrey