Re: Coextensive properties?
From: Lester Zick (lesterDELzick_at_worldnet.att.net)
Date: 10/11/04
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Date: Mon, 11 Oct 2004 20:00:02 GMT
On Mon, 11 Oct 2004 13:26:51 -0400, "Bill Modlin"
<modlin1@metrocast.net> in comp.ai.philosophy wrote:
>This Quine quote often cited by Longley cropped up once again in a note
>by Patty...
>
>> 'If it makes sense to speak of properties, it should
>> make clear sense to speak of sameness and differences of
>> properties; but it does not. If a thing has this
>> property and not that, then certainly this property and
>> that are different properties. But what if everything
>> that has this property has that one as well, and vice
>> versa? Should we say that they are the same property? If
>> so, well and good; no problem. But people do not take
>> that line. I am told that every creature with a heart
>> has kidneys, and vice versa; but who will say that the
>> property of having a heart is the same as that of having
>> kidneys?
>>
>> In short, coextensiveness of properties is not seen as
>> sufficient for their identity. What then is? If an
>> answer is given, it is apt to be that they are identical
>> if they do not just happen to be coextensive, but are
>> necessarily coextensive. But NECESSITY, q.v., is too
>> hazy a notion to rest with.
>>
>> We have been able to go on blithely all these years
>> without making sense of identity between properties,
>> simply because the utility of the notion of property
>> does not hinge on identifying or distinguishing them.
>> That being the case, why not clean up our act by just
>> declaring coextensive properties identical? Only because
>> it would be a disturbing breach of usage, as seen in the
>> case of the heart and kidneys. To ease that shock, we
>> change the word; we speak no longer of properties, but
>> of CLASSES......
>>
>> We must acquiesce in ordinary language for ordinary
>> purposes, and the word 'property' is of a piece with it.
>> But also the notion of property or its reasonable
>> facsimile that takes over, since these contexts never
>> hinge on distinguishing coextensive properties. One
>> instance among many of the use of classes in mathematics
>> is seen under DEFINITION, in the definition of number.
>>
>> For science it is classes SI, properties NO.'
>>
>> W. V. O. Quine (1987)
>> Classes versus Properties
>> QUIDDITIES:
>
>Since Quine is no longer around to ask, perhaps David will help me to
>understand this better.
>
>The example chosen by Quine to illustrate a problem with "properties"
>seems silly. We say that an organism has a heart because we dissect it
>and find a muscular lump of tissue suited for pumping blood. We say
>that it has a liver because we find a different lump of tissue, in a
>different location, suited among other things for filtering harmful
>chemicals from the blood.
>
>Because each is involved with blood, it is not surprising that they tend
>to be found in the same organisms, that their occurrences are highly
>correlated. But I don't see how such a correlation, even if perfect,
>among clearly distinguishable properties should lead one to want to
>consider them the same property.
>
>Quine seems to be saying that we should take "having a liver" and
>"having a heart" as defining the same property, and says that the only
>reason we don't take this step is that it would be a breach of common
>usage. He then suggests that we switch to using the word "class" as
>though this will somehow make it reasonable to ignore the differences
>between hearts and livers....
>
>Which is absurd. The criteria for determining whether or not an
>individual is a member of a class of liver-possessing entities is still
>quite distinct from the criteria for membership in a class of
>heart-possessing entities. If those two distinct criteria are
>empircally determined to lead to identical classes, that is useful
>information. It suggests that there may be a connection between the two
>criteria, a relationship between the properties, which is worth
>following up and may lead to more information about things like
>circulatory systems and blood flow. But it in no way suggests an
>identity between hearts and livers, or between classes of things having
>them or between the properties of having them.
>
>I can imagine cases where different labels may be applied to vaguely
>defined properties, cases in which one might discover that one was
>making a distinction without a difference, and clarity might be better
>served by recognizing the equivalence of properties previously
>considered different.
>
>But this is not such a case, and the class of things with livers remains
>distinct from the class of things with hearts, regardless of the
>empirical coextensiveness of those classes.
>
>I don't think science requires us to ignore relevant distinctions just
>to allow silly wordplay at this level.
>
>However. My impression is that Quine was pretty smart. Which suggests
>he might not be making the silly mistake this seems to me to be. So
>I'm open to further explanation, if someone can show me where I missed
>the point. Just please don't direct me to more of Quine's words... I've
>read them, many times, and I don't think I'll get any more from reading
>them again at this time.
No, I think you've analyzed the problem correctly. You have a stronger
stomach for Quine than I.
Regards - Lester
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