To: Chris M.
From: Geoffrey Klempner
Subject: Criteria of identity for persons and for human beings
Date: 10th January 2011 12:06

Dear Christian,

Thank you for your email of 31 December with your essay for the University of London BA Metaphysics module, in response to the question, 'Are the criteria of identity for persons distinct from the criteria of identity of human beings?'

I was going to say that you managed to say a lot in one hour, then I noticed that this actually took you 1 hour 20 minutes. Still, not bad.

I agree that the question whether all persons are necessarily human beings is a different question from whether the criteria of identity for persons are the same as the criteria of identity for human beings. You are right to put the first question on one side and concentrate on the second. However, you spoil this somewhat by offering the inaccurate gloss, 'Is it necessary and sufficient for a person to be a human being?' on the question, 'Whether a person x1 at t1 is the same person as x2 at t2 in virtue of being the same human being at both times.' Assume that it is necessary and sufficient for a person to be a human being. So all human beings are necessarily persons and all persons are necessarily human beings. Even on this (questionable) assumption, it might still be the case that the criteria of identity for persons and human beings diverge. The same human being might 'become' a different person; or the same person might acquire a new human body.

You do make the important point -- which can easily get missed amongst all the examples and counterexamples -- that the notion of personal identity has two kinds of consequences: for our own sense of what it means to 'survive', and also for our political and legal practice.

The latter is relatively easy to deal with. The science fiction scenarios described by philosophers are extremely unlikely to arise. If they did arise, and become commonplace, then this would indeed involve a radical change to our moral, social, legal and political landscape. But this question is moot. There are very good practical reasons for treating newborn infants and those in persistent vegetative states as 'persons', and this is sufficient to justify regarding the criteria for personal identity as coincident with the criteria for the identity of a human being.

Abortion, on the other hand, is an issue which is contested: if foetuses were persons then abortion would be murder. But I don't think that your answer to the question about the criteria for personal identity and for the identity of human beings needs to decide this issue.

The question of 'what it means to survive' is much harder. Here, I wasn't fully convinced that the question really gripped you. Judith Jarvis Thompson makes an extraordinary claim about the head transplant case. (Although, I once asked two of my daughters when they were much younger 'who would be see in a mirror' if their heads were switched. Both unhesitatingly agreed that they would see their sister's face!) However, given all we know about the role of the brain I find Thompson's answer difficult to believe.

And yet, one only has to tug a little bit at the psychological criterion and it begins to unravel. Wiggins in an important discussion of personal identity (in 'Sameness and Substance') criticizes Locke for failure to recognize that we need a material basis for memory in order to be able to distinguish between 'true' and 'false' memories. Wiggins' own preference is to regard person as a 'natural kind' term (in other words, aligned with the concept of human being). The problem is that we can satisfy the requirement for causal continuity in a material substrate in ways which would allow the fission cases: the example of the 'split brain' is the simplest, but once we accept the idea that in principle brains can be 'programmed', then there is no limit.

Even with two, I think we have to say that I *survive* as A and I also survive as B. This is David Lewises 'intuition'. In that case, what A and B will both say is that, 'I wrote an email to CM on 10 Jan 2011', and, most importantly, each of them will speak the literal truth. (I.e. a 'person' on this view is effectively a 'life history', and life histories can branch -- a view Wiggins detests.)

Imagine a future society where fission was something that occurred fairly often, but not all the time. Various provisions would need to be made: you can't get away with murder, say, by going to a fission booth. If you do, then both A and B must stand trial. And so on. If you met A at a party, and later met B, and they both told you their life story, you would accept this. 'They' were indeed 'both' born at Bushey General Hospital on 17 Jan 1951, even though only one baby emerged from the womb on that day.

But this still doesn't deal with the 'first person view' problem: how I will view a future where A and B are both 'me'? The classic example is where A is sent to a lab to for grotesque medical experiments and B wins 50 million on the Euro lottery. It's something hard to get one's mind around. But, then, what does it mean to 'identify' with a future self anyway? What special kind of caring attaches to 'my own' self that does not apply to others? Parfit (your spell checker changed this to Parfait, as in the dessert!) has a point here.

All the best,

Geoffrey