descartes i am essentially rational, only accidentally an animal ‘essentially’ = logically...

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

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Page 1: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Descartes

I am essentially rational, only accidentally an I am essentially rational, only accidentally an animalanimal

‘‘essentially’ = logically necessarilyessentially’ = logically necessarily Strictly speaking, I’m not even accidentally an Strictly speaking, I’m not even accidentally an

animal, for I’m not an animal at all; I’m animal, for I’m not an animal at all; I’m (contingently) (contingently) embodiedembodied

The demon The demon thought experimentthought experiment shows that I could shows that I could (logically possibly) exist without my body, so I (logically possibly) exist without my body, so I am not identical with my bodyam not identical with my body

Page 2: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

John Perry

““A Dialogue on Personal Identity A Dialogue on Personal Identity and Immortality”and Immortality”

Possibility of survival after death Possibility of survival after death as entrée to thinking about as entrée to thinking about identity of personsidentity of persons

Logical possibilityLogical possibility, not probability, not probability

Page 3: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Qualitative Identity:Qualitative Identity:Being exactly similarBeing exactly similar

Numerical Identity:Numerical Identity:Being one and the sameBeing one and the same

““She’s not the same person since her She’s not the same person since her religious conversion….”religious conversion….”

Page 4: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

The Soul Theory: I am my soulThe Soul Theory: I am my soul

x and y are the same person iff x has (is) the x and y are the same person iff x has (is) the same soul as ysame soul as y

Soul=mind?Soul=mind?

Page 5: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Problem with the soul theory

1.1. Souls are immaterial, so we have no Souls are immaterial, so we have no evidence for reidentification of soulsevidence for reidentification of souls

2.2. But we do have evidence for But we do have evidence for reidentification of personsreidentification of persons

3.3. Therefore, persons are not identical with Therefore, persons are not identical with soulssouls

Page 6: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Argument for premise 1:

1.1. Souls perceived only indirectly, by assumption Souls perceived only indirectly, by assumption of same-soul-same-body principleof same-soul-same-body principle

2.2. This principle cannot be This principle cannot be a prioria priori, since it isn’t , since it isn’t necessarynecessary

3.3. It cannot be It cannot be a posterioria posteriori, since there’s no , since there’s no empirical evidence for it (and couldn’t be!)empirical evidence for it (and couldn’t be!)

4.4. Therefore, there’s no evidence for the principleTherefore, there’s no evidence for the principle

Page 7: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

The Body Theory: I am my bodyThe Body Theory: I am my body

x and y are the same person iff x has (is) the x and y are the same person iff x has (is) the same body as ysame body as y

Conditions for sameness of body?Conditions for sameness of body?

(Ship of Theseus)(Ship of Theseus)

Page 8: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Arguments against the Body Theory:

You wake up and you know who you are, without having identified your body yet.

Mind transfersMind transfers

Page 9: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 10: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 11: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 12: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

John Locke:(1632-1704)

I am a sequence of causally connected

experiences

Page 13: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Psychological Continuity TheoryPsychological Continuity Theory

x and y are the same person iff the x and y are the same person iff the psychological states of x are appropriately psychological states of x are appropriately linked to the psychological states of ylinked 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

Page 14: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 15: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 16: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 17: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Page 18: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Page 19: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Page 20: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Possibilities:

A. Matter is transferredA. Matter is transferred

Page 21: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Possibilities:

A. Matter is transferredA. Matter is transferred

Page 22: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Possibilities:

B. Only information is transferredB. Only information is transferred

Page 23: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Possibilities:

B. Only information is transferredB. Only information is transferred

Page 24: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

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 suicideSo teletransportation is suicide

Page 25: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 26: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,
Page 27: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Personal Identity redux

Soul theorySoul theory

Body theoryBody theory

Psychological continuity theoryPsychological continuity theory

Fictionalism: strictly speaking, persons don’t Fictionalism: strictly speaking, persons don’t endure over time; we attribute a fictional endure over time; we attribute a fictional identityidentity

Page 28: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Ego theory:

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

Page 29: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Bundle theory:

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

Page 30: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

David Hume1711-1776

Page 31: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

No concept of enduring self

1. If you can’t experience something, you can’t conceive it

2. Introspection reveals only train of perceptions, no enduring subject of perceptions

3. Therefore, we don’t experience an enduring self

4. Therefore, an enduring self distinct from these perceptions is literally unintelligible.

Page 32: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

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: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

Page 33: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Parfit: argument for bundle theory

1.1. If ego theory is true, there should be hard If ego theory is true, there should be hard and fast facts about whether x and y are and fast facts about whether x and y are the samethe same

2.2. But there very often aren’t such factsBut there very often aren’t such facts

3.3. Therefore, the ego theory is falseTherefore, the ego theory is false

4.4. The only alternative is the bundle theoryThe only alternative is the bundle theory

5.5. Therefore, the bundle theory is trueTherefore, the bundle theory is true

Page 34: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Parfit: argument for bundle theory

1.1. If ego theory is true, there should be hard If ego theory is true, there should be hard and fast facts about whether x and y are and fast facts about whether x and y are the samethe same

2. But there very often aren’t such facts

3.3. Therefore, the ego theory is falseTherefore, the ego theory is false

4.4. The only alternative is the bundle theoryThe only alternative is the bundle theory

5.5. Therefore, the bundle theory is trueTherefore, the bundle theory is true

Page 35: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Teletransportation with partial material Teletransportation with partial material preservation:preservation:

2% new matter?2% new matter?50% new matter?50% new matter?98% new matter?98% new matter?

Page 36: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Split brains

Page 37: Descartes I am essentially rational, only accidentally an animal ‘essentially’ = logically necessarily ‘essentially’ = logically necessarily Strictly speaking,

Two streams of consciousness: one ego Two streams of consciousness: one ego or two?or two?

1=1+1?1=1+1?

Suppose hemispheres placed in new Suppose hemispheres placed in new bodies, live separate lives. Is one of them bodies, live separate lives. Is one of them you?you?Which one?Which one?