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From: peru@cogsci.ed.ac.uk (Peter Ruhrberg)
Subject: Re: 1. FOL and 2. Longley's insidious programme
Message-ID: <DCHFzH.9uz@cogsci.ed.ac.uk>
Organization: Centre for Cognitive Science, Edinburgh, UK
References: <806970538snz@longley.demon.co.uk> <3vclci$a66@news.service.uci.edu> <807011331snz@longley.demon.co.uk>
Date: Sat, 29 Jul 1995 14:52:26 GMT
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Xref: glinda.oz.cs.cmu.edu comp.ai:32028 comp.ai.philosophy:31113 sci.logic:13335 sci.cognitive:8718 sci.philosophy.tech:19105

In article <807011331snz@longley.demon.co.uk> David@longley.demon.co.uk writes:
>
>However, on this issue I am all ears. As someone looking for clarification
>of this issue (it seems that each and every writer seems to wish to redraw
>the lines between the different 'logics'), I would be grateful for *views*
>on why FOL does not suffice. The posings on 'connectedness' did not really
>resolve the issue. 

If you want clearification you better ask precise questions rather
than posting endless quotes. You might even provoke some people who
*really* know the subject (I'm not including me there) into helpful
responses. I confidently predict one thing they will all agree on:
there is no argument from behaviorism to first-orderism, or vice
versa. you can be a prisoner of FOL, like Bealer, with the wildest
intensional ontology and believe in any psychology you like, or a
hard nosed Skinnerian, using the most outlandish logics.

What can and cann't be "done" in FOL is surrounded by many myths, many
of which arise by not contemplating *theories* expressed in FOL,
rather than only the bare calculus. Others by attatching too much
philosophical weight to model theory.

>Inevitably, those working on modal and higher order logics think this work
>important, it may well be. However, I, and many others would like to  know
>why one of this century's most eminent philosophers should claim that  FOL
>should suffice.

As for Quines reasons, from looking at your quotes and dim memory of
his writing, it sounds to me like: FOL is the stronges formalism where
two misguided explications of 'logical truth' almost coincide. Ok.,
that's a bit unfair, but his (refinement of the) substitutional
account of logic is certainly subject to pretty devastating
objections, (see Etchemendy's book "The Concept of Logical
Consequence",) and the modeltheoretic one, is infected with some of
the same troubles (which come out clearly is 2nd order logic). 

Peter


