Newsgroups: comp.ai.philosophy
Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!gatech!news.sprintlink.net!tank.news.pipex.net!pipex!uknet!bcc.ac.uk!ucacpaf
From: ucacpaf@cs.ucl.ac.uk (Alasdair Turner)
Subject: Re: Defining a chair
Message-ID: <ucacpaf.806928300@cs.ucl.ac.uk>
Date: Fri, 28 Jul 1995 10:45:00 GMT
References: <ucacpaf.806597088@cs.ucl.ac.uk> <jqbDC96w8.AvD@netcom.com>
Organization: University College London
Keywords: chair fuzzy logic intent purpose 
Lines: 79

jqb@netcom.com (Jim Balter) writes:
>[...]
>Surely it is important for 'chair' to not refer to stools, or doctor's tables
>(certainly designed, among other things, to be sat upon), or a flagpole

(upon == on?) 

>designed solely for challenging flagpole-sitting records, or a toilet, or a
>bench, etc.  Is a bench a chair?  Is a narrow bench a chair?  What about a
>narrow bench with a flat seat parallel to the ground?  It seems to me that you
>only escape sorites problems by ignoring the thorny cases.

True... although chair v stool (or toilet) is [seems] well defined for humans.

AT> [People] do not seem to say "Well, it's mostly a chair".
>
>As long as they don't encounter examples that fall into the fuzziness of their
>meanings.  Most people, e.g., have trouble deciding whether a piece of art
>designed like a chair but clearly not meant to be sat upon really *is* a
>chair.  The presence of a sign that says "please do not sit" or "please sit"
>could affect that judgement.  Especially if the latter sign hung over a
>"chair" made of tissue paper, or with a steel spike attached to the "seat".

(Is a house a chair if the artist claims it is a chair? --- which is not to
diminish this line of argument [which is good])

>Is the latter "identical in form" to a chair?  It seems that having the right
>form is not necessarily enough to say that something is a chair, nor is having
>the right function, but having both the right form and the right function is
>too much (a chair with broken legs and a torn seat, making it impossible to
>sit upon it, is clearly still a chair, whereas we really wonder about that
>thing with the steel spike).

Yes --- however this worries me even more...

>[...]
>I would say that the abstract definition partially concerns form and partially
>concerns function and partially concerns context and partially consists of
>examples.  This abstraction provides us with a method to decide that many
>situations deserve the response "is a chair" and many situations deserve the
>response "is not a chair", but the logic is not complete and thus cannot
>provide a clear answer in every case.  I.e., it's "fuzzy".

However, you (I) could argue that the logic is not fuzzy, that we just don't 
know what the rules are [for the combination of form / function / context / 
example].  Perhaps, even, a paradigm that suggests an intensional /
extensional distinction is in error and the root of the of problem.

>[...]  But if you want it to label objects as
>chairs iff *you* would call them chairs, you may need a model of your own
>brain state, or a replay of the entire set of input that led to the creation
>of the abstract representation of the concept "chair" in your brain.

Maybe rather "society" than "*me*".  Obviously this will leave a bit of
'fuzzy' border where different members of society disagree (or different
societies have culture bound 'definitions' or, as you mention above, an
actual fuzzy instance of "I don't know"), but I'd like to be able to
reach an acceptable definition a chair without needing to replay all this
input.

>[...] The problem is much much harder than most
>people realize.  You cannot reliably distinguish between a chair and a narrow
>bench without also having notions of parks, living rooms, and the like.

Thanks! :-(

>[...]
>Forget about faith and belief; just do the work and see what comes of it.
>-- 
><J Q B>

Yes, I was afraid that that was going to be the answer!  Oh well... back to
work.

Thanks for the useful discussion,

Alasdair Turner


