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Re: [ontolog-forum] what is a proposition?

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Thu, 24 May 2007 04:25:48 -0400
Message-id: <46554C0C.7000206@xxxxxxxxxxx>
Ingvar,    (01)

As I said in a previous note, my preferred definition of
'proposition' is a Peircean view of a proposition as an abstract
entity that corresponds to something along the lines of the
quotation you cited:    (02)

> "In philosophy, but not in business and sexual activity, a proposition 
> is whatever can be asserted, denied, contended, maintained, assumed, 
> supported, implied, or presupposed. It is that which is expressed by a 
> typical indicative sentence. The same proposition may be expressed by 
> different sentences."    (03)

But I realize that many logicians follow Quine in allowing sets
or constructions of sets as the only admissible abstract entities
in their ontologies.    (04)

 > I have noted that you call your definition a "formal definition"
 > of proposition, but I  think a more adequate label would be
 > "definition of the formal-logical counterpart to propositions".    (05)

I agree with that point.  Instead of saying    (06)

    "a proposition is defined as an equivalence class of sentences
    in some formal language L under some meaning-preserving translation
    (MPT) defined over the sentences of L."    (07)

I would be happy to accept the quotation above by identifying
a proposition as "that which is expressed by a typical indicative
sentence."  And I would expand the following sentence "The same
proposition may be expressed by different sentences" by saying
that all the sentences that express the same proposition form
an equivalence class.    (08)

In other words, the propositions are in a one-to-one correspondence
with the equivalence classes of sentences.  But I agree that I should
avoid saying that the propositions *are* the equivalence classes.    (09)

John    (010)

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