Re: "Inevitable Illusions"

From: Wise (weiz@spam-block.sympac.com.au)
Date: Mon May 21 2001 - 15:58:16 MET DST

  • Next message: Ellen Hisdal: "Re: "Inevitable Illusions", Law of Excluded Middle etc."

    I nursed for a while and we often needed to dip
    a plastic stick, containing a number of chemically impregnated
    pieces of paper up the length of the stick, into a urine sample.

    These sticks gave us an indication of sugar, proteins, etc found in
    the urine sample. Inevitably they were graded not just true or false
    indications.
    In real life the diagnosis and treatment of disease is not just true or
    false.

    Your example talks about an absoluteness in having a disease which is
    inevitably not always the case.

    We can have a person who can belong to the fuzzy set of diabetics who we
    would think
    of as having diabetic tendencies. In fuzzy terms they have a small
    membership value
    in the diabetic set.

    The classical logic would have us render them as diabetic or not diabetic.
    The artificial
    preciseness is actually a dangerous circumstance because now we have to
    treat or
    not treat. Real life actually uses fuzzy logical strategies to handle these
    people and their
    treatment.

    A full on, full blown diabetic (a real life description) is someone who, in
    fuzzy set
    terms, has a high membership value in the diabetic set.

    The words (descriptions) are optional, the fuzzy math under the bonnet is
    consistent.

    I think that a lot of discomfort with fuzziness is its ability to
    accommodate the superficial, the changing
    and very malleable language layer. They are only descriptors used to label
    both the sets and then the
    extent of membership in those sets.

    As descriptors ....slightly diabetic, less diabetic, diabetic tendencies ...
    allows me and
    you to put our heads at the lower end of the spectrum (low membership
    values) of diabetic types.

    We do need to be on the same page with respect to our fuzzy set definitions,
    our fuzzy value universe,
    etc... if we jointly intend doing any thing more precise, but often to hold
    a conceptual conversation
    a lot of this stuff is just not required, it is implied.

    If I tendered the following advise

                 to treat your diabetic tendencies patient with diet and review
    after a while

    without a lot of definitions, to prop up the words tendencies and review or
    the word while you would get the drift of
    what I recommended.

    Now if you wanted to meter out a precise dose of chemical A for particular
    Diabetic lets talk about the
    membership value of that person in the diabetic set and then using fuzzy
    mathematics calculate the
    dose and frequency of chemical A.

    Fuzzy control systems work today that achieve this type of precision.

    And that my friend is TRUE in a fuzzy kind of way.

    Rob W

    Chris De Voir wrote in message ...
    >> -----Original Message-----
    >> From: fuzzy-mail@dbai.tuwien.ac.at
    >> [mailto:fuzzy-mail@dbai.tuwien.ac.at]On Behalf Of Wise
    >> Sent: Wednesday, May 16, 2001 6:31 PM
    >> To: Multiple recipients of list
    >> Subject: Re: "Inevitable Illusions"
    >>
    >>

    >My question is: Supposing that all the data in the above example take on
    >Fuzzy values, how does one maintain logical clarity of Bayes to make good
    >predictions/decisions using Fuzzy still subject to limited rationality?
    >
    >Regardless, the answer may still be, no, this has not been studied. But
    >thanks for the response.
    >
    >Chris.

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