Re: Coextensive properties?
From: Just Playing (gms2004_at_lycos.com)
Date: 10/12/04
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Date: 12 Oct 2004 07:48:11 -0700
"Bill Modlin" <modlin1@metrocast.net> wrote in message news:<v7Gdnbcy6f29X_fcRVn-rw@metrocastcablevision.com>...
> 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;
Just Playing
My 2 cents worth.
I guess that he starts by defining the class of living beings.
Than he uses 2 criteria or properties to farther differentiate this
class, first the heart and second the kidney.
Finally after using these 2 criteria or properties he observes that
the results are identical, there is no difference.
The conclusion is that using these 2 different criteria gives you the
same answer.
So here comes his question:
but who will say that the property of having a heart is the same as
that of having kidneys?
Just Playing
Or what was the use of the 2 criteria or properties if they do not
give us different results?
And from here he goes on to look at the criteria or properties:
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.
Just Playing
Here he starts looking at the criteria or properties. The simple fact
that the criteria or properties are different does not mean that the
results will be different too. So maybe his conclusion is that we
ought to redefine the classes to include the properties that are
coextensive, as in calling the living being class the class that also
includes heart and kidney, and apply other criteria or properties to
farther differentiate this class.
> >
> > 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.
>
> Bill Modlin
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