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Re: [ontolog-forum] Ontology, Information Models and the 'Real World': C

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From: <matthew.west@xxxxxxxxx>
Date: Fri, 1 Jun 2007 08:35:57 +0100
Message-id: <808637A57BC3454FA660801A3995FA8F053AC47B@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Dear Colleagues,    (01)

Well I am one of those who has followed this thread with interest.    (02)

I wonder if there is someone who would summarise it onto a page
for the Ontolog Wiki?    (03)

Regards    (04)

Matthew West
Reference Data Architecture and Standards Manager
Shell International Petroleum Company Limited
Registered in England and Wales
Registered number: 621148
Registered office: Shell Centre, London SE1 7NA, United Kingdom    (05)

Tel: +44 20 7934 4490 Mobile: +44 7796 336538
Email: matthew.west@xxxxxxxxx
http://www.shell.com
http://www.matthew-west.org.uk/    (06)


> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx]On Behalf Of Ingvar
> Johansson
> Sent: 31 May 2007 17:11
> To: [ontolog-forum]
> Subject: Re: [ontolog-forum] Ontology, Information Models and 
> the 'Real
> World': Contexts
> 
> 
> John F. Sowa schrieb:
> > Folks,
> >   
> 
> The discussion seems to have come to an end. Since I introduced the 
> question "what is a proposition?" into this forum, I would 
> like to say 
> some concluding words on my part, too. That is, words from a 
> philosopher 
> not interested in constructing formal-logical models or 
> languages. But I 
> happen to be convinced that propositions are as needed in speech act 
> theoretical analyses of natural languages as they are in the 
> propositional calculus.
> 
> > One reason for introducing a technical term, such as proposition,
> > is to make distinctions that are confused in more common words
> > such as 'meaning'.  However, technical terms are always defined
> > in some theory, and people who hold different theories are likely
> > to have different and incompatible definitions.
> >   
> 
> Sure; nonetheless: as far as I can see, everyone agrees (i) that 
> propositions are truthvalue bearers, and (ii) as soon as propositions 
> are tied to merely  one world, one context, or one 
> some-such-thing, then 
> the truthvalue of a proposition cannot possibly be changed. 
> (I hope I am 
> allowed to use the word "changed" here, even though John 
> wants to take 
> it away from IKL.)
> > Quine has been cited as an authority, and he is for many purposes.
> > But Q. has stated some strong views, which are not accepted by a
> > large number of logicians and philosophers. 
> 
> Since I am the one who quoted Quine, let me make it clear 
> that I quoted 
> him *only* in order to show that he is among the philosophers 
> who regard 
> propositions (and/or their equvivalents such as 'eternal 
> sentences') as 
> entities that cannot change truthvalues. I am by no means a Quinenan. 
> John Sowa has listed many respects in which his views differs from 
> Quine's. In all these respects, I share John's views; I even 
> share his 
> critical stance towards much possible world talk.
> 
> >  In particular,
> >
> >   1. Q. rejected any version of modal logic.  His 
> opposition amounted
> >      to more than merely ignoring it while working on other issues.
> >      Instead, he denied the value, usefulness, or even the 
> possibility
> >      of having a coherent system of modal logic.
> >
> >   2. Point #1 is compatible with Q's denial of any clear or coherent
> >      distinction between intension and extension.  That distinction
> >      is central to any version of modal logic, which allows 
> a sentence
> >      s (with no unresolved indexicals) to have different 
> truth values
> >      in different worlds, contexts, or universes of discourse.
> >
> >   3. Since Q's primary work has been in formal logic, he never
> >      developed a complete semantics for natural languages (and he
> >      has been skeptical of the possibility of developing a complete
> >      semantics).  Yet he made many comments about various sentences
> >      in NLs and their translations to logic.
> >
> >   4. In those comments, Q. avoided directly addressing the question
> >      of indexicals by coining the term 'eternal sentence' 
> for a sentence
> >      whose referents are all fixed (either bound to 
> explicit quantifiers
> >      or to explicitly named individuals).  In effect, he 
> defined that
> >      term to mean 'absence of indexicals' without using the terms
> >      'indexical', 'context', 'possible world', etc.
> >
> > These views gave Quine's writings an admirable clarity, but at the
> > expense of ignoring or even deprecating all talk about subjects he
> > was not prepared to discuss clearly -- which includes the 
> most serious
> > issues about natural languages.
> >
> > For these reasons, I believe that taking the word 'proposition' as
> > synonymous with Q's term 'eternal sentence' 
> 
> Surely, I have not proposed this; see my former remark! And I don't 
> think anyone else in this discussion has done it either.
> 
> > would force us to adopt
> > aspects of Q's philosophy that are incompatible with applications
> > for which IKL (and other logics) might be used.  Among them is the
> > semantics of NLs, for which many people would like to use IKL.
> >
> > Since IKL uses the word 'proposition' as a technical term, it is
> > important to use that word in a way that minimizes confusion among
> > IKL adopters. 
> 
> But when it is introduced in a forum like "ontolog-forum", I 
> think it is 
> equally important to introduce it in such a way that even confusion 
> among the members of the forum that are not IKL adopters is minimized.
> 
> >  I think I agree with Pat about the IKL formalism,
> > and I think that I know what he meant by the following statements:
> >
> >   1. A proposition has a fixed truth value.
> >
> >   2. But a proposition might have different truth values in 
> different
> >      contexts.
> >
> > However, this conjunction is likely to cause confusion (or at least
> > lengthy discussions such as this thread).
> >
> > My recommendation is to replace the above statements with something
> > along the following lines:
> >
> >   1. The IKL model theory defines an evaluation function Phi, which
> >      for any proposition p, determines a truth value Phi(p).
> >
> >   2. Inside a nested context, however, the proposition p could have
> >      a truth value that is different from the value Phi(p) 
> that would
> >      be determined outside any nested context.
> >
> > This avoids the word 'fixed' without introducing the word 'changing'
> > or any term such as 'proposition-in-a-context'.
> >   
> 
> At last, may I humbly repeat an earlier (but unanswered) 
> mail-question 
> of mine; even if perhaps it is based on a complete 
> misunderstanding of 
> IKL. Here the mail once again:
> 
> ------------------------------------------------------------------
> 
> Waclaw Kusnierczyk schrieb:
> 
> > > I think we agree.  A context, as treated in IKL, corresponds to a 
> > > perspective (no cognitive agent implied) on a proposition 
> *as if it 
> > > were* true or false, irrespectively of whether it *is* 
> true or false.
> > >   
> >   
> 
> Dear Waclaw,
> 
> Does this solve the following earlier problem of yours: "The 
> question, 
> again, is about propositions. The sentence "no roses are 
> blue" was true 
> some time ago, and is false now; but does it correspond to the same 
> proposition in both cases? Is it the proposition that changed 
> its truth 
> value, or are we really dealing with two distinct propositions: 'no 
> roses are blue at t1', and 'no roses are blue at t2'?" ?
> 
> If "no roses are blue" are stated twice (in the way you have 
> described) 
> *in the same context*, then it seems to me that a distinction such as 
> mine between *sentence meaning* and *used sentence meanings* is 
> nonetheless needed as a complement.
> 
> -----------------------------------------------
> 
> Is my question completely beside the point? Is IKL not at all 
> meant to be applied to the kind of
> natural language situations that I am envisaging? If so, then 
> there is of course no need to discuss how to individuate 
> propositions in natural languages. Can someone, please, tell 
> me whether IKL has or is meant to be given some kind of 
> relation to natural languages.
> 
> best wishes,
> Ingvar
> 
> 
>  
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>     (07)


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