X-Message-Number: 8266
Date: Sat, 31 May 1997 17:47:07 -0400 (EDT)
From: "Perry E. Metzger" <>
Subject: minds, machines, etc.

> From:  (Thomas Donaldson)
> 
> One major question: please tell me what you consider to be a
> "computer". Unless I know this I have no way to convincing you
> whether or not computers can become self aware or not.

What do I consider to be a computer? Roughly, a device that is Turing
equivalent.

All computers are equivalent according to the Church-Turing thesis,
regardless of form. The set of problems which are computable by a
computer is pretty much the same REGARDLESS of what sort of hardware
is in the machine. Even recent development of "quantum computer"
theory yields computers that are merely faster, and in no way able to
do anything a "normal" computer cannot do. To be semi-formal about it,
the set of functions computable by any computer, period, is the same
as that any other can compute given sufficient time.

If you have evidence that the Church-Turing thesis is wrong, please
let us all know -- you will likely get a Fields Medal for the
discovery.

BTW, the Church-Turing thesis probably holds for any analog device as
well as any digital device. Since analog computing mechanisms have
limits to their resolution and noise in their operation, one can
always simulate an analog computer with a sufficiently powerful
digital computer.

> Second major question: we have no trouble, in our rough way, in saying that
> one person is conscious while another is not. We do so on the basis of their
> behavior.

I have no difficulty assessing that someone is certainly AWAKE or
certainly NOT AWAKE. Consciousness, however, is not something I think
I can assess on the basis of behavior.

> In terms of what we ourselves notice about ourselves, we find that
> usually a judgement based on our behavior is correct: when others decide 
> that we are unconscious, then after we awaken we will agree. When others 
> decide we are conscious, we will also agree. Yes, sometimes people try to 
> act as if they are asleep, and many other such things happen, but there
> is a rough correspondence. 

Being "awake" is not what philosophers are refering to, usually, when
they say "conscious". Maybe we should come up with a definition first,
and then discuss whether we think it can be observed easily.

> So therefore: what is it that makes you say that no observational test for
> consciousness exists?

I cannot say what Mr. Clark's reasons might be, but to me, I'd say the
before even asking this question we have to have some clear idea of
what we define to be consciousness. I don't think that there *is* a
common definition being circulated in this discussion.

Perry

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