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

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

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

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….”

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?

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

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

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)

Arguments against the Body Theory:

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

Mind transfersMind transfers

John Locke:(1632-1704)

I am a sequence of causally connected

experiences

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

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Teletransportation

Person is disassembled, reassembled Person is disassembled, reassembled elsewhereelsewhere

Possibilities:

A. Matter is transferredA. Matter is transferred

Possibilities:

A. Matter is transferredA. Matter is transferred

Possibilities:

B. Only information is transferredB. Only information is transferred

Possibilities:

B. Only information is transferredB. 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 suicideSo teletransportation is suicide

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

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 Hume1711-1776

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.

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

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

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

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?

Split brains

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?