From: chalmers@bronze.ucs.indiana.edu (David Chalmers)
Subject: Re: Functionalist Theory of Qualia
Organization: Indiana University
Date: Fri, 17 Apr 92 00:26:36 GMT

[Sorry about the slow reply on this one.  It slipped past me somehow.]

Drew McDermott writes:

>For example, suppose that I walk through a freshly painted house, and
>observe that the red color of the walls in this room is exactly the
>same as the red I experienced in the previous room.  It feels to me as
>if I am retrieving the memory of a quale and comparing it to the
>current quale.  In other words, the qualia are playing a direct causal
>role.  But of course, they aren't really.  Because my verbal report
>can ultimately be explained (as you will no doubt agree to stipulate)
>by reference to signals flowing through my brain, the judgement that
>this red equals that one is ultimately explainable by reference to a
>comparator somewhere.  (The comparator is comparing the neural
>equivalent of floating-point numbers, not qualia at all.)  Indeed,
>it's the fact that this comparator says the two reds are the same that
>underlies my subjective experience that the two qualia are the same.
>No actual comparison of qualia plays any causal role in the chain.
>(How could it, unless there's a dualist medium where the comparison
>occurs?)

So far, that's fine (I'm more or less an epiphenomenalist, after all).
Some "qualia freaks" might protest at this, holding that qualia
in fact play a causal role but aren't *characterized* by their causal
role (so qualia might possibly be material, but would require a lot
more than the standard functional/behavioural type of explanation),
but let that pass for now.  I'm not sure, however, that one has a
"subjective experience that the two qualia are the same"; one certainly
has a subjective experience of two qualia, and forms a judgment that
they're the same, but it's not obvious that that judgment is itself a
subjective experience in the sense that qualia are.

>I could imagine an evil neurosurgeon reaching in and fiddling with the
>output of the comparator entirely independent of the actual contents
>of the color signals from the retina, so that I might say, "This red
>has hue H, saturation S, etc. [assuming I'm properly trained]," and
>also say with complete sincerity, "It's quite different from that
>other red with, even though I know I reported that it also had hue H
>and saturation S; I must have been mistaken."

Here you're assuming that the causal pathway by which verbal judgments
of individual qualia are formed doesn't involve the comparator; that's
not obvious.  But presumably it could be the case, so let the
thought-experiment stand.  What should a realist about qualia say about
this case?  It seems to me that there are a couple of possibilities,
depending on whether the qualia themselves are partly determined by
the functioning of the comparator.  If so, the use of the comparator
might actually change the qualia that one experiences.  But even if
not -- so that the two experiences really are qualitatively identical,
but are judged different -- I don't think that's a real problem.
Judgments about phenomenology are distinct from phenomenology (they're
harder work, for a start -- try it!), and they're the kind of thing
that can be mistaken in principle (especially if someone fiddles
with the circuits).  I once wrote a paper about the Sorites paradox for
qualia: e.g. Red-1 looks the same as Red-2, which looks the same as
Red-3, which...; but Red-1 doesn't look the same as Red-10.  The
best conclusion for a qualia realist to draw is that even under fairly
normal circumstances, two qualia can be judged identical without being
identical.

>In other words, I certainly have the strong impression that something
>is immediately given to consciousness, but even the attempt to pin
>down the simplest aspect of what that something might be leads to
>vacuousness.  The very idea of qualitative similarity turns out to be
>empty, and what is a quale if it is not (as it seems to be) a
>representative of a type?  Do quale tokens make sense without the
>types they appear to belong to?  This bafflement leads me (and
>others) to propose that the whole story is a fiction that the brain
>needs for some reason.

I think that quale-tokens are indeed members of a type, but I don't
see that serious problems arise.  We just can't base the notion of
qualitative similarity entirely on the results of verbal judgments.
Personally, I think that qualia supervene on a fairly wide causal role;
"comparator" operation is part but not all of that role.  Identity
of qualia requires more than comparator-equivalence (e.g. at the very
least, for qualia A and B to be identical, they should yield
identical results when individually compared to separate qualia C;
and then there are aspects of the causal role that don't involve the
comparator at all).

>Allow me to play around with the vanishing-qualia idea.  You have
>suggested that the physical universe could continue to work exactly as
>it works now, and yet there could be no qualia.  Very well, suppose
>God decided to do away with the qualia this morning at 9 AM.  Has it
>made any difference?  Obviously, just as in the fading-qualia case,
>no.  Not only will my verbal reports of my experiences be as before,
>so will my introspective state.  When the qualia went out, I'm not
>even allowed to say, "Hey! Something weird just happened, but I'm not
>sure what."  That would require a change to the physics.

That's right.

>Okay, let's suppose that the universe is only like this from 9 to 5
>(Eastern Standard Time) every day.  In other words, we only really
>have qualia after work.  The rest of the time we don't really exist.
>Of course, we don't notice this because all our memories are intact at
>5 o'clock; there's no contradiction in supposing that we can have
>memories of qualia we never really experienced.  It's enough that when
>we retrieve a memory there's a certain qualitative pang.
>
>I'd like this argument to show that qualia are totally vacuous.  But
>I'm afraid all it really shows is that qualia are probably
>supervenient on the physical world somehow, which everyone but
>Chalmers probably already accepts.

I don't see that this shows anything.  It's conceivable, consistent,
and almost certainly false.  It seems to be precisely of a kind with
Descartes' evil demon hypothesis, and the hypothesis that the world was
created five minutes ago.  One can't *disprove* such hypotheses (well,
not unless it's between 9 and 5, but unfortunately it's 7 pm now),
but one shouldn't believe in them either.  Is the very fact that this
hypothesis is conceivable meant to be a reductio ad absurdum of qualia,
or of dualism?  That doesn't seem to follow, any more than the
five-minutes-ago hypothesis is a reductio ad absurdum of the concept
of the past.

Incidentally, I certainly believe that qualia are supervenient on the
physical.  The supervenience is contingent, that's all.

-- 
Dave Chalmers                            (dave@cogsci.indiana.edu)      
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."