Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking, I’m not even accidentally an animal, for I’m not an animal at all; I’m (contingently) embodied Strictly speaking, I’m not even accidentally an animal, for I’m not an animal at all; I’m (contingently) embodied The demon thought experiment shows that I could (logically possibly) exist without my body, so I am not identical with my body

John Perry “A Dialogue on Personal Identity and Immortality” Possibility of survival after death as entrée to thinking about identity of persons Possibility of survival after death as entrée to thinking about identity of persons Logical possibility, not probability Logical possibility, not probability

Qualitative Identity: Being exactly similar Being exactly similar Numerical Identity: Being one and the same Being one and the same “She’s not the same person since her religious conversion….”

The Soul Theory: I am my soul x and y are the same person iff x has (is) the same soul as y Soul=mind?

Problem with the soul theory 1. Souls are immaterial, so we have no evidence for reidentification of souls 2. But we do have evidence for reidentification of persons 3. Therefore, persons are not identical with souls

Argument for premise 1: 1. Souls perceived only indirectly, by assumption of same-soul-same-body principle 2. This principle cannot be a priori, since it isn’t necessary 3. It cannot be a posteriori, since there’s no empirical evidence for it (and couldn’t be!) 4. Therefore, there’s no evidence for the principle

The Body Theory: I am my body x and y are the same person iff x has (is) the same body as y Conditions for sameness of body? (Ship of Theseus)

Arguments against the Body Theory: You wake up and you know who you are, without having identified your body yet. Mind transfers Mind transfers

John Locke: ( ) I am a sequence of causally connected experiences

Psychological Continuity Theory x and y are the same person iff the psychological states of x are appropriately linked to the psychological states of y ‘appropriately linked’? ‘appropriately linked’? Locke: memory: x = y iff the later of the two can remember the experiences of the earlier

Teletransportation Person is disassembled, reassembled elsewhere

Teletransportation Person is disassembled, reassembled elsewhere

Teletransportation Person is disassembled, reassembled elsewhere

Possibilities: A. Matter is transferred

Possibilities: A. Matter is transferred

Possibilities: B. Only information is transferred

Possibilities: B. Only information is transferred

Argument against Psychological Continuity Theory: If you can replicate one, you can replicate two. Since they aren’t both identical with me, it seems that neither is So teletransportation is suicide So teletransportation is suicide

Personal Identity redux Soul theory Body theory Psychological continuity theory Fictionalism: strictly speaking, persons don’t endure over time; we attribute a fictional identity

Ego theory: underlying subject of experiences: a substance in the technical sense (usually immaterial substance)

Bundle theory: collection of mental events: there is (in a sense) no self

David Hume

No concept of enduring self If you can’t experience something, you can’t conceive it Introspection reveals only train of perceptions, no enduring subject of perceptions Therefore, we don’t experience an enduring self Therefore, an enduring self distinct from these perceptions is literally unintelligible.

Why do we believe in enduring things? Observing a smooth succession is very similar to observing an enduring object, so we mistake the former for the latter. We ascribe identity when: changes are proportionately small changes are gradual changes don’t alter purpose of the whole All this shows that identity is ascribed, rather than a real property of the objects

Parfit: argument for bundle theory 1. If ego theory is true, there should be hard and fast facts about whether x and y are the same 2. But there very often aren’t such facts 3. Therefore, the ego theory is false 4. The only alternative is the bundle theory 5. Therefore, the bundle theory is true

Parfit: argument for bundle theory 1. If ego theory is true, there should be hard and fast facts about whether x and y are the same But there very often aren’t such facts 3. Therefore, the ego theory is false 4. The only alternative is the bundle theory 5. Therefore, the bundle theory is true

Teletransportation with partial material preservation: 2% new matter? 2% new matter? 50% new matter? 50% new matter? 98% new matter? 98% new matter?

Split brains

Two streams of consciousness: one ego or two? Two streams of consciousness: one ego or two? 1=1+1? 1=1+1? Suppose hemispheres placed in new bodies, live separate lives. Is one of them you? Suppose hemispheres placed in new bodies, live separate lives. Is one of them you? Which one? Which one?