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this to the doctors. They hear him say that everything is fine, so they don't have a clue
what's happening to him. His depiction of this scenario reminds one of the stories about
curare, the paralytic that was mistakenly thought to be an anesthetic.3 Patients were
suffering horribly but unable to move a muscle, so the doctors believed them to be
unconscious. If all the replacement were supposed to preserve is behavioral equivalence,
then this depiction of scenario (1) would make sense.
However, Zjoe is supposed to be functionally equivalent to me as well as behaviorally
equivalent. So when Searle is gradually turning into his zombie counterpart, Zjohn, we
have to suppose that functional equivalence is maintained. Functional equivalence
involves a lot more than behavioral equivalence, especially with respect to what's going
on inside. Not only would Searle's behavior have to match that which he would manifest
were his consciousness to be maintained, but all of his internal states would have to
maintain all of their causal relations as well.
In particular, consider his introspective states. Throughout the replacement process his
introspective states would maintain their functional role. So suppose that state I-R is his
belief state with the content I am now having an experience of type R (where R
refers to a reddish experience). I-R, presumably, is normally caused by experiential states
of type R. At some point in the replacement process states of type R will disappear,
replaced by states of type E-R (ersatz R-experiences). But E-R will still cause I-R, since
functional equivalence is maintained. Furthermore, since I-R had the content I am
having an experience of type R before the replacement, there is no reason to refuse to
attribute to it the same content after the replacement. But that means Searle would
continue to believe he is having R-experiences, quite unlike the way he described the
scenario. In fact, it seems as if he would be as clueless regarding his fading consciousness
as the doctors. But if
end p.153
that's the case, what difference could consciousness make to him in the first place? Any
conception of consciousness on which one could lose it without noticing does not seem to
be a conception of the phenomenon we care about. Thus the zombie hypothesis seems to
reduce to absurdity.
The replacement process allegedly leads to an absurdity. The source of the absurdity
seems to be the fact that the process is gradual; hence Chalmers's name for the argument,
fading qualia. How could my qualia be gradually fading and yet I be unaware of it? If,
on the other hand, the process were instantaneous, then presumably the sense of absurdity
would diminish, or vanish altogether. If I go from being conscious to being a zombie in
one fell swoop, then there's no point at which I should be noticing something happening
but, by the hypothesis of functional identity, am unable to notice it. If replacement yields
total and instantaneous loss of consciousness, then it's no harder to swallow than the
existence of a zombie in the first place.
So one possible response to the replacement argument is to maintain that consciousness is
realized in such a way that either it's completely there or it isn't there at all. In fact, one
wouldn't have to maintain that there was a single consciousness cell, or something of that
sort, which really would be quite implausible. It might be that there is some very complex
physical configuration which, when it's completely present, so is consciousness, and,
when any part of it is absent, consciousness goes completely. Thus ridding the brain of
one neuron might turn one into a total zombie, but there's no one neuron that has the
honor of being the consciousness neuron. Losing any one out of a whole bunch might do
the trick.
Though not obviously incoherent, this reply does seem desperate. Is it really plausible
that some small physical change could turn one into a zombie? We just have no reason to
think that the psycho-physical link works that way. For the qualophile to insist that it
must be so is to adopt an ad hoc position, pressed into service merely to undermine the
replacement argument. It would be much more compelling to show that sense could be
made of the replacement scenario even if consciousness is lost gradually.
Another possible line of reply for the qualophile is to deny the premise of functional
identity, a premise that is crucial to the charge of absurdity. That I and Zjoe are
functionally identical is built into the zombie hypothesis, so the qualophile can't mess
with that. But it doesn't follow from the claim that I and Zjoe are functionally identical
that replacement of my parts with Zjoe's parts would leave me functionally unchanged.
Call the realizers of my functional states, the ones with qualitative character, Q-states,
and the realizers of Zjoe's functional states, the ones without qualitative character, Z-
states. Where Qr realizes my reddish visual experience, Zr realizes Zjoe's functional
analogue of my reddish visual experience, his ersatz reddish experience. The replacement
argument depends on the assumption that were my Qr to be replaced by Zr, then when I
look at my red diskette case, and go into state Zr, I would be occupying a state
functionally identical to the state I used to occupy, but would fail to have the conscious
experience that used to
end p.154
accompany it. But why should we assume this? In Zjoe, Zr played a certain functional
role. Why think it would play this role in me?
Again, though perhaps this line could be pursued, it really doesn't seem to get at the heart
of the issue. Of course it may be that, given the natures of both conscious and non-
conscious realizers, it's not possible to mix them in such a way as to preserve functional
identity. But at most the sense of possibility at issue must be nomological. It's certainly
not conceptually impossible, and it seems hard to see good reason to think it's
metaphysically impossible, though one can insist that it may be nonetheless. It seems to
me that the qualophile should allow both that replacement might preserve functional
identity, and that the loss of consciousness might be gradual, or piecemeal. Now, can the
qualophile make these concessions and still avoid the reductio?
Here's one way to begin to break the sense of absurdity. As the scenario is standardly
described this certainly comes across from Searle's description I am supposed to be
experiencing a fading of consciousness, as my conscious realizers are replaced by ersatz
realizers. The image one gets is of one gradually losing consciousness before going to
sleep. But there is no justification for this way of imagining what would happen. In fact,
there is an interesting fallacy involved in this depiction of the replacement process, one
akin to a fallacy that Dennett and Kinsbourne (1992) point out with respect to
consciousness of time. They emphasize that one shouldn't confuse the consciousness of a
time interval with the interval, or duration, of a state of consciousness. In this case, one
shouldn't confuse the fading of consciousness with the consciousness of fading. Both
happen (often) as one falls asleep, but only the former is involved in the replacement
process.
Let me elaborate. It's supposed to be absurd that I could be experiencing a fading, or
limiting of my conscious experience without being aware of it. But there's nothing in the
initial description of the replacement process that should lead one to describe me as
having an experience of fading, or diminishing, or even limiting of my conscious
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