Newsgroups: comp.ai.philosophy
From: lupton@luptonpj.demon.co.uk (Peter Lupton)
Path: cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!news2.near.net!MathWorks.Com!news.duke.edu!news-feed-1.peachnet.edu!gatech!howland.reston.ans.net!pipex!demon!luptonpj.demon.co.uk!lupton
Subject: Re: Strong AI
References: <356ggl$3mf@toves.cs.city.ac.uk> <352i6s$7d5@portal.gmu.edu> <SWRA01.94Sep13145419@cs19.cs.aukuni.ac.nz> <35483r$gk@portal.gmu.edu>
Distribution: world
Organization: No Organisation
Reply-To: lupton@luptonpj.demon.co.uk
X-Newsreader: Newswin Alpha 0.4
Lines:  40
Date: Sun, 18 Sep 1994 09:33:04 +0000
Message-ID: <171232385wnr@luptonpj.demon.co.uk>
Sender: usenet@demon.co.uk

In article: <356ggl$3mf@toves.cs.city.ac.uk>  jampel@cs.city.ac.uk (Michael Jampel) writes:
> 
> HARRY R. ERWIN <herwin@mason1.gmu.edu> wrote:
> 
> >I left out a point that matters here--the brain is an analog device. 
> >Although it supports syntactic (digital) processing, it isn't limited to
> >that. Spikes are used primarily in long-range communication, while local
> >communication involves graded potentials. Yes, at the level of the
> >individual ion, you might think you could discuss some sort of digital
> >process, but even there, the ion moves continuously. This analog nature
> >probably underlies why the brain appears to operate semantically.

Don't see this. I can't get from semantics to analog or continuity. So far
as I can see the defining characteristic of continuity is infinite information.
Don't see how that would help us. As for analog, I don't see anything
in analog system which isn't dicreteness in-the-small.

> >
> >To show that the operation of the brain cannot be adequately simulated by
> >a Turing machine, you have to get your arms around the problem of when a
> >digital simulation might fail for a real-world (hence, continuous) system.
> 
> I thought that the entire world was quantised: neurons etc only appear
> to be analog because we are `standing too far away' from them: if we
> chose a resolution comparable to the Planck length, wouldn't everything
> appear quantised hence discrete hence digital?

Talking about the Planck length makes discretness seem rather academic -
what is needed is a sense in which discreteness does more work for us
in a more immediate sense. The importance of discreteness lies in the
notion of finite information. And this notion lies at the heart of
approximation and so to resemblance and fit. A continuous system - a 
system of truly infinite information - has no well-defined notion of
approximation which could be made use of in a finitary manner. To do
*that* some *measure* would need to be added - but this would just 
lead us straight back to aritrary-up-to-an-epsilon and so to discreteness.

-------------------
Peter Lupton
