X-Message-Number: 15240
Date: Tue, 02 Jan 2001 23:53:34 -0700
From: Mike Perry <>
Subject: Turing's Ideas, Reanimation

Thomas Donaldson, #15226, says:

> Moreover, the behavior of human brains (which inevitably must be 
> coupled to a sensory system and another system which allows them to act)
> may violate Turing's ideas: not simply by being parallel, but by
> adding and subtracting new subcomputers (called neurons) and changing
> their circuitry too. It just isn't enough to produce a computer
> which can, at some very low speed, imitate some of the behavior of
> a human being. We need one which works at the same speed. I do not
> accept Turing's ideas as the last word on just how our computing
> circuits can work, not at all... and especially not because he
> envisioned a single computer working on an endless tape.
>

"Turing's ideas" about computing are largely implementation-independent.
True, he did employ a model consisting of a single, simple device (a
read-write head) moving back and forth over a single, 1-dimensional tape.
But he and others after him made it clear that equivalent computations are
possible using more than one tape, a tape with more than one dimension, a
cellular space with every cell capable of independently changing state and
all changing in parallel, many computers running in parallel, and so on. If
you understood this principle better, Thomas, I think you'd see how our two
positions are not in fundamental disagreement, at least if you grant that
people *could* operate at lower speed given a suitable environment. And, as
someone has pointed out, that may be necessary in the more distant future as
the universe becomes less energetic. Earlier than that, we could face
tradeoffs such as whether to reanimate someone "in the flesh" knowing it is
hazardous, or to express them in some computational form even if some basic
features would change such as a speedup of mental processes or,
alternatively, an unavoidable slowdown.

Mike Perry

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