X-Message-Number: 7876
From: 
Date: Mon, 17 Mar 1997 15:22:23 -0500 (EST)
Subject: emulating brains

Joe Strout (#7864) has some remarks on uploading and emulation that, in my
opinion, repeat some old mistakes, so I'll briefly regurgitate some old
replies. (Joe says essentially that brains are computers and can be emulated,
hence can be uploaded, in principle....and with at least the implicit
suggestion that this would constitute survival for the uploaded brain.)

First, when Joe says brains are computers, presumably he means that all the
essential functions of the brain (outside of housekeeping) are computational.
This is by no means self evident, and probably not true. In particular, it is
not necessarily true that FEELING (or subjectivity) is just a kind of
computation, any more than a temperature is just a computation. The condition
of being hot or cold is not the same as a calculation of what a temperature
would be under certain conditions.

The definition of "emulation" is a bit hazy around the edges, but generally
it is used to mean a kind of isomorphism, whereby each of (say) two systems
has every feature and every behavior reflected in the other (assuming the
environments remain identical), so that, observing the behavior of one
system, we could accurately infer that of the other. But there are several
profound problems:

1. Depending on how strictly you define "emulation," you may run into
problems of real time vs. computer time. A Turing tape, in principle, can do
any computation that any computer can do--but not in real time. A highly
parallel computation might help, but not necessarily by enough. It is
possible, for example, that essential functions of the brain require certain
events to occur in a small volume of space-time, and it may not be PHYSICALLY
POSSIBLE for such to happen in some arbitrary physical computer space. It is
possible, in other words, that ONLY an organic substrate can support the
necessary interdependency of functions. Thus--conceivably--a computer might
be able to PREDICT or describe the detailed function of a brain, and still
not BE a brain.

2. Presumably we are talking about digital computers. We don't know whether
the brain is (or can be) digital, which leaves many open questions.

3. Even if computer emulation were perfect, spacetimewise as well as
otherwise, there would still remain the unresolved question of survival when
the original is destroyed (or not) and a duplicate created, or several
duplicates. If a perfect organic duplicate of you were somehow created, at
some arbitrary distance in spacetime, would that be you? If the duplicate
were created in the future, would that constitute your survival or
reincarnation? What if duplication were imperfect? What if the duplication
were of you as you were at some earlier stage in life? Or as you would become
at some later stage in life? These questions have many possible answers, but
none that is agreed upon. Would you bet your life on any of the answers, if
you were not forced to do so?   

Robert Ettinger


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