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In article <1992Sep17.154637.9156@guinness.idbsu.edu> holmes@opal.idbsu.edu (Randall Holmes) writes:

[contra Chalmers]

>What I am trying to point out is that your argument is unsound.  As I
>see it, you are arguing thus:
>
>i.  It is logically possible that physical states can exist without
>the corresponding conscious states.
>
>The fallacy is in i; it is not "possible" that they are different; it
>is "imaginable" on the basis of what we know that they are different.
>We do not know if it is possible until we know more about what the
>relation between them is in the actual world (we may never find out,
>of course).

It's important not to forget that David Chalmers is talking about logical
possibility and not physical possibility.  Something might be logically
possible even if physically possible.  Of course, not everyone will
accept that logical possibility is an interesting notion.

Moreover, "possible world" means logically possible world in this
context.

>You cannot claim i. until you KNOW that the conscious states and the
>physical states are different

Not so.  When two things are actually the same it can still be
logically possible for them to be different.  Not always, though.
You have to figure out which case you're in.  But you don't always
have to know two things are actually different to know that it's
logically possible for them to be different.

>         Now, your assertion that it is logically possible
>that C and P are different amounts to "On the basis of what we know,
>we can imagine that facts of type P occur without facts of type C";
>you _cannot_ say "It is actually true in some possible world that
>facts of type C occur without facts of type P" [...]

Almost any conclusion we care to make could be prefixed by "on the
basis of what we know"; so we can factor it out.  And "it's logically
possible that" is just another way to say "there's a possible world in
which it's true that".  So if we can say "it's logically possible
that" we can just as well say "it's true in some possible world
that".

>Here is a formally parallel argument:

This point turns on the use of two different meanings for "strangeness".
If we look at them correctly, we will reach one conclusion about
logical possibliity for one meaning and a different conclusion for
the other.  All we can really say about it is that if you _define_
"strangeness" in terms of the number of quarks, then (of course!)
there is no possible worlds in which the concepts are not identical.
But this conclusion is taken as saying something about the other
case, where we don't define them to be identical.  

>Matters are obscure here, he says, but, in any event, I can prove that
>"strangeness" is not identical with "the number of strange quarks
>minus the number of strange anti-quarks"; there is a possible world in
>which these concepts are not identical (he has in mind a world in
>which there are no quarks), so the identity of these predicates is
>contingent, and the number of quarks minus the number of anti-quarks
>thus represents additional information about the world in addition to
>the more easily observed "strangeness" of the particles. 

And this is the right conclusion to reach when we don't make the
identity true by definition.

>But, if we
>believe the standard model, we _define_ "strangeness" in terms of
>numbers of quarks, and we do not draw any such conclusions from the
>hypothetical physicist's possible world; in this world, there is
>indeed a property called "strangeness" which acts rather like our
>quark-based property, but we do not admit that they are coordinate
>concepts, because their underpinning is quite different, and we do not
>recognize the hypothetical physicist's "strangeness" as a ghostly
>additional property of objects in the real world.

And this is just fine when we do define them to be identical.

But consciousness is _not_ defined interms of physical properties.
So this case is not formally parallel to Chalmers' argument.

-- jd