To: Stuart B.
From: Geoffrey Klempner
Subject: Personal identity and survival
Date: 22nd March 2011 11:37

Dear Stuart,

Thank you for your email of 9 March, with your essay for the University of London BA Metaphysics module, in response to the question, 'Is a person's survival different from, and more important than, a person's continuing identity?'

This is a very thorough and well-researched essay which goes deeply into the question of whether, and how, an alternative to what you term 'diachronic logical identity' for persons might be constructed. I don't have any real difficulties with the details of this account, save one.

In considering the 'four possible answers' to the fission puzzle, you reject the answer, 'both' (the B-body person and the C-body person are both identical with the A-body person) and claim that it is 'universally dismissed'. If A undergoes fission into B and C, then it does seem obviously wrong to assert that A=B and A=C but not-(B=C). That is a plain, flat-out contradiction according to the definition of identity.

However, there is a way out of this, which I am sure I have mentioned before (correct me if I'm wrong). David Lewis proposes this solution, although I came to it independently. If A undergoes fission into B and C, then from our new temporal perspective what we can and should say is that we now recognize the existence of two As, the A that became B and the A that became C. In other words, a 'person' is to be construed as a life history. (I'm pretty sure I did talk about this, as I mentioned Wiggins' objection to the effective reduction of a person to a mere series of person-stages.)

What would we say about Riker? I'm pretty the only thing we could say is that both are 'Riker', both enrolled as space troopers and were assigned to the Enterprise. They both remember narrowly passing the exam, flirting with the girl at the space station, being hospitalized for two weeks after a radiation leak and so on.

Does this make sense? Or, maybe a better question, Is this what we want from a notion of personal identity? What question should we ask here?

My main problem with your essay is that you don't address at all the question of what it means to 'survive'. This is the crux. If diachronic logical identity doesn't hold up, if the very notion is beset by irresolvable contradictions, then what interest does a weaker notion of continuity have?

I have three daughters. That means three chances for the 'survival' of my blood line. It is a deep and wonderful fact about human life that, although we are mortal, we are, potentially at least, a link in a potentially infinite series of generations. This is not personal survival by any definition, but it matters to me. It also matters to me that human beings, generally, will survive to populate the universe and not be wiped out in, say, 500 years.

Not good enough? Let's say I have a twin brother, and we both serve as technicians on the same nuclear submarine. There is a reactor failure and one of us has to go in to replace the fuel rods by hand. It means certain death. But if I have to go in, at least I know that my twin will survive. We are very close, we share everything. But he is not I. If the coin falls on heads and I have to go in to the reactor room then I will die. There will be no more of me. Although there will be more of someone very much like me, so like me in fact, that anyone who knew one of us would hardly notice the replacement.

But I don't think this is good enough either. What intuitions are we calling upon, when we attempt to decide this issue?

Shifting back to the fission case, who is to say whether I should or shouldn't count one of my future continuers as 'close enough' for survival? How can survival be a merely relative matter? It's a matter of life or death, surely.

Parfit's agenda is crucially different. The point about downplaying the 'importance' of identity comes out when one considers the consequences for ethics. Logically, a 'good' ought not to be more desirable just because it is good for 'me'. In the case of the submarine twins, there is no justification, period, for my wanting to survive at the expense of my twin. The very idea of there being 'something extra', namely 'my being me', is the very thing that Parfit rejects. We are qualitatively the same, and that's all that matters.

Generalizing from this, all that counts are the qualities of persons, and the satisfactions that can be gained by a person of such-and-such quality, in the process of maximizing the benefit for all. In other words, the ethics of preference utilitarianism.

In other words, Parfit isn't talking about 'survival', he is talking about something else. To use the old formula (which became slightly unfashionable after Quine's '2 Dogmas') he hasn't analysed the notion of 'survival' he has merely 'changed the subject'. I still wait to be convinced that there is an interesting and relevant sense of 'survive' which does not equate to identity.

All the best,

Geoffrey