Personal identity

Michael Lacewingenquiries@alevelphilosophy.co

.uk

Two kinds of identity

• Qualitative identity: two things are identical in their properties

• Numerical identity: there is just one thing (a=a)

• If one thing changes its qualities, does it remain the same thing?– ‘He was a different person after the cancer scare’– Who was? Change presupposes numerical identity

• Personal identity: what are the criteria for being the same (numerically identical) person over time?

One mind?

• Dualism: I am a mental substance; as long as the substance persists, I do

• Materialism: there is only matter - does this mean that I persist as long as my body does?

• Psychological theory: personal identity is continuity in psychological properties - even if these are transferred to another body

Locke’s theory• I am united by memory: I am the same person as I was at

times I remember– But I can’t remember every moment from the past– Overlapping chains of memory

• What of sleep? Shoemaker: causal dependence not just on memory but persistence through sleep

• Extend from memory to many psychological states

An objection

• The teletransporter malfunctions!– Both Kirks have overlapping chains

of psychological states; are both Kirk or neither? We have qualitative identity, but not numerical

– Not both: One person cannot be or become two people

– Not neither: the same causal relation holds as in normal cases; whether Kirk is Kirk can’t depend on whether another Kirk exist…?

• Something other than psychological continuity is needed for personal identity

Bodily theory

• Psychological continuity isn’t enough, there must be continuity in matter

• Williams: more than 50% of my brain• Animalism: we are animals, not

simply embodied minds; personal identity means continuing as the same organism

• Teletransportation doesn’t keep identity - it produces a replica

Brain transplants

• Is animalism or Williams right? If your brain is switched with another brain, which body are you ‘in’? Your original one or the one with your brain in?

• Your brain and mine are both ‘erased’ and then reprogrammed with each others psychological states; now which body are you ‘in’?

Was I that baby?

• I have almost no psychological continuity with the baby whose body became mine

• So was I ever a baby?• Option 1: we are

essentially animals, and only persons for some time

• Option 2: we are essentially persons, and start to exist after the animals whose bodies we are ‘in’