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
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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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