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Article 5110 of comp.ai.philosophy:
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>From: minsky@media.mit.edu (Marvin Minsky)
Subject: Re: Categories: bounded or graded?
Message-ID: <1992Apr15.150901.10959@news.media.mit.edu>
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Cc: minsky
Organization: MIT Media Laboratory
References: <1992Apr14.143822.10246@psych.toronto.edu> <1992Apr15.010721.17700@organpipe.uug.arizona.edu>
Date: Wed, 15 Apr 1992 15:09:01 GMT
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In article <1992Apr15.010721.17700@organpipe.uug.arizona.edu> bill@NSMA.AriZonA.EdU (Bill Skaggs) writes:
>In article <1992Apr14.143822.10246@psych.toronto.edu> 
>christo@psych.toronto.edu (Christopher Green) writes:
>>
>>From: Stevan Harnad
>>
>>We disagree even more on categories. I think the Roschian view you
>>describe is all wrong, and that the "classical" view -- that categories
>>have invariant features that allow us to categorize in the all-or-none
>>way we clearly do -- is completely correct. Introspections about how
>>we categorize are irrelevant (did we expect introspection to do
>>our theoretical work for us, as cognitive theorists?), as are
>>reaction times and typicality judgments. The performance capacity
>>at issue is our capacity to learn to sort and label things as we do, not
>>how fast we do it, not how typical we find the members we can
>>correctly sort and label, not the cases we CANNOT sort and label,
>>not the metaphysical status of the "correctness" (just its relation
>>to the Skinnerian consequences of MIScategorization), and certainly
>>not how we happen to think we do it. And the categories of interest
>>are all-or-none categories like "bird," not graded ones like "big."
>
>  With Wittgenstein in mind, I ask:  what are the invariant features
>that characterize a "game"?
>
>  Wittgenstein, of course, argued that there are none.  His view,
>and an increasing popular view among linguists (see, for example,
>Lakoff's "Women, Fire, and Dangerous Things") is that natural
>categories are not defined by invariant features, but rather
>by radiation from prototypes.  (Thus a bird is anything that is
>sufficiently similar to the prototypical bird, which is something
>like a sparrow.)  I don't want to sound like Mikhail Zeleny, but
>I will go so far as to say that the idea that categories are
>defined by invariant features is no longer really defensible.
>
   The problem both with Wittgenstein and Lakoff is the same; basing a
definition on invariant features or on similarities to prototypes have
the same bug when the categories depend on the intentions of the
person who is trying to make the definition.  Consequently, what we
usually need is something that sandwiches the definition between the
two aspects: structural (that is, of the examples) and functional
(that is, of the intended purpose or usage of the category).  More
details start in section 12.4 of The Society of Mind.  Perhaps some of
you will see this as a way to resolve some of the problems that
frustrated Wittgenstein.



