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In article <23af61c2.0108180659.1cbf8b83@posting.google.com>, Robert Dodier writes:

*> Stephan.Lehmke@cs.uni-dortmund.de (Stephan Lehmke) wrote:
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*>
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*>> Robert Dodier writes:
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*>> >
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*>> > Any such definition must ignore the relation between elements in a
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*>> > compound: if truth(B')=truth(B), then in any proposition containing
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*>> > A and B, I can swap in B' in place of B, and get exactly the same
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*>> > truth value for the compound; whether the elements are redundant,
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*>> > contradictory, or completely unrelated doesn't enter the calculation.
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*>>
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*>> It's exactly the same in two-valued logic. As fuzzy logic agrees with
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*>> classical logic on the extremal truth values, there is no way the
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*>> behaviour you observe can be avoided.
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*>
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*> Consider a less-extreme example, then: let A = "the mayor is tall",
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*> B = "the mayor is heavy", and B' = "the mayor is well-dressed". For the
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*> sake of argument suppose that truth(B)=truth(B'). Despite the fact that
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*> we know that there is some relation between height and weight, the
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*> truth value assigned to a compound containing A and B is just the same
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*> as what we get by putting B' in the place of B.
*

Again, i must ask whether the situation would change if two-valued

logic were employed? Otherwise, obviously it has to be the same in

fuzzy logic. Fuzzy logic is about vagueness, not telepathy (whatever I

know has to be reflected by the logical system, whether I care to

write it down or not).

Btw, I doubt that the fact that you know something is reflected by

probabilistic logic, without your formalizing it in any way.

*> There is a two-fold drawback of defining truth value of a compound
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*> strictly as a function of truth values of its parts. (i) You cannot
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*> exploit information about the relation between A and B; even if you
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*> know what it is, there is simply no place to put it in the computation
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*> of the truth value of a compound proposition. (ii) The rules for computing
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*> truth value of the compound don't tell you when you need to supply
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*> some information about the relation between the parts.
*

I think we're talking cross purposes here. Logic is not about

computing truth values, but about drawing conclusions from assertions.

Of course, it is perfectly possible to state the relations between A

and B it the form of axioms, as I have pointed out before.

*> To draw a
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*> conclusion about a compound proposition, maybe you need to know something
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*> about the relation between the parts and maybe you don't, but there's
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*> no way to tell from the rules which is the case.
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This statement is unintelligible to me. Could you elaborate?

regards

Stephan

-- Stephan Lehmke Stephan.Lehmke@cs.uni-dortmund.de Fachbereich Informatik, LS I Tel. +49 231 755 6434 Universitaet Dortmund FAX 6555 D-44221 Dortmund, Germany############################################################################ This message was posted through the fuzzy mailing list. (1) To subscribe to this mailing list, send a message body of "SUB FUZZY-MAIL myFirstName mySurname" to listproc@dbai.tuwien.ac.at (2) To unsubscribe from this mailing list, send a message body of "UNSUB FUZZY-MAIL" or "UNSUB FUZZY-MAIL yoursubscription@email.address.com" to listproc@dbai.tuwien.ac.at (3) To reach the human who maintains the list, send mail to fuzzy-owner@dbai.tuwien.ac.at (4) WWW access and other information on Fuzzy Sets and Logic see http://www.dbai.tuwien.ac.at/ftp/mlowner/fuzzy-mail.info (5) WWW archive: http://www.dbai.tuwien.ac.at/marchives/fuzzy-mail/index.html

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