Re: Is a Person One or Many?

From: Stathis Papaioannou (
Date: Sun Mar 09 2008 - 20:05:45 MDT

On 10/03/2008, John K Clark <> wrote:

> I am unaware of any logical paradoxes concerning personal identity. I
> can think of some odd situations but they are unusual only because up to
> now technology has been unable to do certain things; someday that will
> change

They aren't actually logical paradoxes, but there is a problem when
you try to fit notions such as anticipation or subjective probability
into situations we did not encounter when our brains evolved:

- Eliezer's example where you are duplicated 100-fold if a coin comes
up heads and then re-merged a short time later: what is the subjective
probability of heads?

- Lee's example where you are duplicated and an hour later you (i.e.
one of the copies) are offered painless death so that the other copy
gets a large sum of money. Most people would probably not agree to
this, and yet it is subjectively equivalent to the situation where you
are offered the money if you agree to have a drug like midazolam,
which can cause amnesia for a similar period. I have never known
anyone to refuse midazolam for fear of the amnesia.

- If 1000 copies of you are made in London lacking 50% of your
memories and 10 copies are made in Paris lacking 5% of your memories,
are you more likely to find yourself waking up in London or Paris?

- You are offered two choices:
(a) 100 copies of you are made in London and one copy is made in
Paris. The Paris copy is tortured while the London copies are not
(b) 100 copies of you are made in London and one copy is made in
Paris. After an hour, the 100 copies in London are tortured while the
copy in Paris is duplicated 100,000 times and none of these copies are
Is your subjective probability of being tortured at the moment of the
original copying greater in (a) or (b)?

Note that there is no problem *objectively* describing what happens in
any of these cases. Lee tries to take the objective point of view and
translate it into the subjective point of view as well. But to do this
would require a complete overthrow of our notions of anticipation and
subjective probability, and I don't think this is possible without
rewiring our brains.

Stathis Papaioannou

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