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From: peru@cogsci.ed.ac.uk (Peter Ruhrberg)
Subject: Re: McCarthy, Leibnitz's Law & Intension
Message-ID: <DBpKvH.A2q@cogsci.ed.ac.uk>
Organization: Centre for Cognitive Science, Edinburgh, UK
References: <805473042snz@longley.demon.co.uk> <DBK6FH.5xq@cogsci.ed.ac.uk> <805480529snz@longley.demon.co.uk>
Date: Fri, 14 Jul 1995 13:45:13 GMT
Lines: 72
Xref: glinda.oz.cs.cmu.edu comp.ai.philosophy:30160 sci.philosophy.tech:18760

In article <805480529snz@longley.demon.co.uk> David@longley.demon.co.uk writes:
>In article <DBK6FH.5xq@cogsci.ed.ac.uk>
>           peru@cogsci.ed.ac.uk "Peter Ruhrberg" writes:
>> 
>> I think it is time to get rid of the idea, floating in this newsgroup,
>> that science of the intensional is impossible because of the
>> substitutivity problem in intensional contexts. The bookshelves are
>> full of consistent intensional logics. The key point is what you take
>> for denotations, so the issue is ontological really. If you're happy
>> with possible worlds, or properties, you may even - oh wonder - use
>> 1st - or whatever order - *extensional* logic to talk about them. (for
>> example basic modal logic is a fragment of FOL, via Kripke's
>> semantics; Bealers Property Theory is fully expressed in FOL; etc...)
>> The question is whether we want to live in Quines cold universe of
>> particles, sets, and double standards. 
>> 
>> Peter
>> 
>
>This is where methodological solipsism (Fodor 1980) leads one to. As far 

reading people other than Quine on the subject of intensional logic
was to blame in my case. (You might find Bealer's "Quality and
Concept" a stimulating read. Take Davidsons word for it.)

>as is known, we *do* live in Quine's cold universe, whether we *like it* 
>or not is beside the point. Psychotics can  have  internally  consistent
>'logics', but that doesn't mean they are not deluded. 

*do* we? at least you seem ready to cencede that it is consistent to
think otherwise. maybe it is also sensible, but i didn't go so far (yet).

>    'Once  it  is shown that a region of  discourse  is  not 
>    extensional, then according to Quine, we have reason  to 
>    doubt its claim to describe the structure of reality.'
>
>    C. Hookway
>    Logic: Canonical Notation and Extensionality
>    Quine (1988)

I just explained that *extensional* logic is perfectly suitable to
talk about very intensional entities. This reason is no more.

(two non-quine quotes deleted)

>To seriously adopt your recommendation  would  surely open new  vistas 
>for AI - perhaps warranting the new name of 'Artificial Reality',which
>elsewhere we call fiction (at best). This has already happened over in
>psychology, as Skinner was at pains to point out in 1987 in  'Whatever 
>Happened to Psychology as the Science of Behaviour?'. 
>
>Whilst just about anything *is*  possible  in  the  worlds of  virtual 
>reality, that is only the case  because the constraints of physics, ie
>the real world, are abandoned. Furtermoe, if there are essentially no 
>constraints at all, what sort of science can that possibly be??
>-- 
>David Longley

David, I made just an attempt here to get the issue of *extensional
logic* out of the way. What matters for psychology is the issue of
ontology: do we need *intensional entities* or not? I'm not saying they
exist, just because it is consistent to think so. Let's be pragmatic
on this matter. If science can do without them I'm happy to regard
them as science fiction. Just don't tell me I have to abandon them
because Quine says there's something wrong with them. My personal
concern is the theory of meaning of natural languages. The best ones I
know use intensional entities. I'm not yet prepared to apply double
standards and regard this business as unscientific waffle. Maybe you
can convince me?

Peter

