From: hal@finney.org
Date: Thu Dec 13 2001 - 13:29:39 MST
John Clark writes, quoting Michael F:
> > I can be reasonable sure that when I go to sleep at night I don't die for a
> > few reasons 1) Hooking me up to any kind of machine that measures brain
> > activity would never measure any absolute cessation in activity
>
> Not in normal sleep but it would under deep anesthesia. When you go to the
> hospital to have your tonsils removed are you the same man when you walk out?
One of the problems with Michael's position is that it is possible that
normal sleep doesn't kill you, because as he said the brain activity
continues, but that deep anesthesia does (supposing that in fact brain
waves stop during that time).
His position on identity states that there is a fact of the matter about
whether any particular instance of consciousness is a continuation of an
earlier one which successfully retains the same identity. Certain kinds
of discontinuities, in this view, break the chain and so the identity
is not the same. Other kinds, like sleep or blows to the head, do not
break the chain.
The question is, how could you know that severe discontinuities like
John's anesthesia example, or severe head trauma, don't break the chain?
It certainly won't work to ask the person afterwards if he feels the
same, because I think everyone agrees that he would say he does, even if
in fact the chain of identity had been broken. Someone who was copied
without his knowledge would say the same thing, and on this view he
is wrong, his identity is no longer the same, but he doesn't know it.
So statements and even personal experience are no evidence.
If you agree that there is no way to tell if severe trauma breaks the
chain of identity, and even the person involved can't tell afterwards,
then how confident can you be that ordinary sleep doesn't break it,
either? Your personal experience and memories are no guide.
Evolutionarily there would be no reason for brains to have evolved to
maintain "identity" since it has no operational effect in the world.
A race which unknowingly died every night would be no less successful
than one which maintained the chain of consciousness from day to day.
Without evolutionary pressure to maintain the property of identity
conservation, and with your personal experience offering no evidence
that it exists, why would you expect it to be true?
Hal
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