Personal Identity Derek Parfit Notes

• Parfit targets two beliefs:

  1. that in problem cases of personal identity there must be an answer - many people believe this to be true e.g. ‘whatever happens, any future experience will either be my experience, or it will not.’

This belief has two effects: it promotes self interest, and makes people feel depressed about ageing and death. Very difficult to disprove - Parfit will attempt to make it seem implausible

2. that unless the question of identity has an answer, we are unable to answer important questions e.g. survival, memory etc

Parfit’s response: certain questions do presuppose a question about personal identity, but we can free them of this presupposition, and once we have done so, personal identity has no importance

• Fission:

  • What happens to me?

    1. I survive as one - why only as one? How can a double success be a failure?

    2. I do not survive - seems absurd that you do survive as long as there is not external replica. Why one rather than the other?

    3. I survive as both. Logically impossible? If we are talking about numerical identity. Also science has shown that a split brain seems to lead to a split consciousness

  • Maths exam, two solutions to a question, both need to be done. So I voluntarily split my brain, work out the solutions simultaneously and reunite before writing answer. It seems mental history (cf. identity) can be not just like a canal, but like a river, with islands and separate streams.

  • Can we claim survival in fission cases, where survival implies identity? Yes, but we can only keep the language of identity at the cost of our concept of a person. Alternatively, we give up the language of identity

  • The problem with giving up the language of identity is that it seems to sidestep the problem of personal identity. BUT this objection only matters if we hold one or more of the above beliefs, and the fission cases give us very good reasons for thinking the first belief to be implausible - it seems that the split persons neither have the same nor obviously different identities to the original person. This also undermines the second belief - it does not always make sense to question personal identity, so if we want answers to the important derivative questions we need to separate them from identity

  • So, to separate survival from identity: if we are asking ‘will there be someone alive who is the same person as me?’ we must surely say that we survive fission. If the relation between C and C1 would be sufficient for survival in the case in which there is no C2, why should the existence of C2 make any difference? If anything we should imagine it is a simultaneously doubling of life expectancy

  • Parfit’s conclusion: the relation of the original person to each of the resulting people contains all that matters in any ordinary case of survival. So we need a sense in which one person can survive as two.

• Identity is a one-one relation. What matters in survival need not be one-one.

  • One problem with taking identity to be what matters is that it is one-one, and what actually matters (psychological relations etc) are relations of degrees - the one-one mentality leads us into false beliefs etc

  • Most of the relations that matter can be referred to as ‘psychological continuity’ (including causal continuity). The language of identity implies such continuity - so psychological continuity may provide a criterion of identity.

  • In fact, psychological continuity is a ground for speaking of identity when it is one-one. If psychological continuity took a one-many or many-one/ branching form, we would need to abandon the language of identity

  • In the case of branching, we may now be obliged to say that a one-many...

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