Friday, August 31, 2007

Notes on Riddles of Existence, Ch. 1, Personal Identity

The question: what makes persons numerically the same over time (if they are)?
Numerical sameness vs. qualitative sameness: we aren’t qualitatively the same at all times, yet we are numerically the same (or are we not?).

Some concrete reasons to be interested: regret, anticipation, just punishment, and life-after-death seem to make sense only on the assumption that that was me who did that or that will be me in the future.

“Same matter” theory:
Necessarily , a person A (at T1) is numerically identical to person B (at T2) if, and only if A & B are composed of the same matter.

Objections:
1. If the “same matter” theory is true, then you = the Greek statesman.
2. But you ≠ the statesman.
3. Therefore, the same matter theory is not true. (Modus tollens)

4. If the “same matter” theory is true, then you-NOW ≠ you-5MINUTES AGO.
5. But youNOW = you-5MINUTES AGO.
6. Therefore, the same matter theory is not true. (Modus tollens)


The Soul theory:
Necessarily, a person A (at T1) is numerically identical to person B (at T2) if, and only if A & B have the same soul.

A soul= ? (Non-physical entity that enables thought and feeling).
Sider’s responses: no good reason to believe there are souls. Brains are a better explanation for human thought and feeling.
1. If it is reasonable to believe the soul theory of personal identity, then it is reasonable to believe that there are souls.
2. But it is not reasonable to believe there are souls.
3. So the soul theory is not reasonable to believe.

Another problem:
A & B have the same soul if and only if__?___.
• At the very least, it’s not clear how one could tell this. If this would be known by observation of bodies, brains, and/or psychological matters (i.e., the personality), etc. then it would seem that those factors are what makes for personal identity: the soul would seem to be a “3rd wheel”.
• Further problems if souls have parts that they lose and gain: the problem of soul identity again. This is to dig our hole deeper.

Spaciotemporal (space-time) continuity theory:
Necessarily, a person A (at T1) is numerically identical to person B (at T2) if, and only if A & B are spaciotemporally continuous (and chances between members in the series are gradual, caused by the previous member …. )

Objection from Locke’s case of the Prince and the Cobbler:
1. If the Spaciotemporal (space-time) continuity theory is true, then the person in the prince’s body is really the prince, not the cobbler.
2. But the cobbler is in the prince’s body!
3. So the Spaciotemporal (space-time) continuity theory is not true.

The problem: the space-time theory focuses only on bodies. Locke’s suggestion is that personal identity depends on psychologies.

Psychological continuity theory (mental life=personalities, memories, character traits, etc.):
Necessarily, a person A (at T1) is numerically identical to person B (at T2) if, and only if A & B are psychologically continuous (and chances between members in the series are gradual, caused by the previous member …. ).

Charles and Guy Fawkes objection (from Bernard Williams, a famous philosopher):
Case: Both Charles and Robert (in 2007) have Guy Fawkes’ (1906) psychology.

Objection 1: The Duplication Problem (see also Parfit’s Teletransporter case)
1. If the Psychological continuity theory is true, then Charles = Fawkes and Robert = Fawkes.
2. But if Charles = Fawkes and Robert = Fawkes, then Charles=Robert!
3. But Charles ≠ Robert!
4. So, it’s not the case that: Charles = Fawkes and Robert = Fawkes
5. So the psychological continuity theory is not true.

Objection 2: The Circularity Objection [from Reading Metaphysics]
6. If the Psychological continuity theory is true, then Charles = Fawkes if and only if Charles has Fawkes’ memories, experiences, etc.
7. But Charles has Fawkes’ memories, experiences, etc. (i.e., he doesn’t just think he has these, or imagine having them) only if Charles = Fawkes!!
Moral: there is memory only with identity. So appealing to memory doesn’t help identify the essence of personal identity.

Back to Spaciotemporal (space-time) continuity theory:

How much Spaciotemporal change (to your body) can happen but you remain?

Duplication problem again:
Case: your body and brain are split down the middle. Each half is “rebuilt.” Each is spacio-temporally continuous with you.
If each = you, then each is identical to each other. But each isn’t identical to each other (suppose one is shipped to Japan, the other to Alaska). So each isn’t identical to you.

Problem: both theories have trouble with branching or duplication cases.
• An interesting fact: if there’s no branching, then there’s identity. If there is branching, then there is no identity!

Radical Solutions to the Problem of Duplication:

• Parfit: Being numerically identical to persons “before” and “in front of you” in time is not important!
• What’s important is psychological continuity. (Apply this to the cases above).

No comments: