X-Message-Number: 9796
Date: Thu, 28 May 1998 08:08:43 -0400
From: Thomas Donaldson <>
Subject: more for John K. Clark

Hi again!

A little more for John Clark:

Here is a simple way to see the problem with Merkle's argument. Apply
it to a piece of brain ground up into hamburger.

Certainly we will know the location of every atom in that brain, and
since grinding generally doesn't directly affect chemistry, we'll 
even know the biochemicals of which the brain was composed. But 
whatever structures held memory in that brain have now been completely
destroyed. As structures they were on a higher level than either atoms
or molecules --- they dealt with the LOCATION of those atoms and
molecules, which grinding up the brain has destroyed.

There IS an older theory of memory, produced before people understood
the potential of neural nets, that suggested that memory consisted of
specially altered chemicals in our brain --- to put it primitively,
every memory was encoded in one of these chemicals. This is the only
way in which grinding up the brain might not destroy memory; however
unfortunately or not this theory is no longer believed by anyone.
(It would be nice if it were true, since that would mean that even 
simple freezing would preserve you).

And please understand that I am NOT saying that brains cryopreserved
by present methods are comparable to hamburger. That's not my point at
all. My point is simply that memory almost certainly depends on the
relations between neurons at a much higher level than chemistry or
atoms, and these relations are clearly disturbed by present methods.
We want to know if that disturbance is so great that they cannot be
recovered. To do so we must consider the effects of cryopreservation
on that higher level, in detail. 

And yes, such effects will probably leave a trail in terms of the
location of particular chemicals. But that trail is not at all the
same as the structures we want to recover, and we may find that several
possible structures give the same trail. I am actually optimistic about
our eventual ability to unravel this problem, but any argument which
only talks very generally about how we can locate every atom and molecule
simply fails to tell us just what those locations may say. And that
is the problem: do they tell us nothing at all, or do they give us
hints about the higher level structures from which they came? There is
NO a priori method to tell that. 

Of course, this means that research done now may even clarify this
issue. But we still need that research.

			Best and long long life to all,

				Thomas Donaldson

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