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Personal identity. Michael Lacewing enquiries@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 ?
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Personal identity Michael Lacewing enquiries@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’