Psyche 8(19): 'Zombie-Mary and the Blue Banana' by Tillmann Vierkant
Patrick Wilken
PSYCHE: AN INTERDISCIPLINARY JOURNAL OF RESEARCH ON CONSCIOUSNESS
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ZOMBIE-MARY AND THE BLUE BANANA
ON THE COMPATIBILITY OF THE 'KNOWLEDGE ARGUMENT' WITH THE ARGUMENT
FROM MODALITY
Tillmann Vierkant
Max Planck Institute for Psychological Research
Amalienstr.33
80799 Munich
GERMANY
Copyright (c) Tillmann Vierkant 2002
PSYCHE, 8(19), October 2002
http://psyche.cs.monash.edu.au/v8/psyche-8-19-vierkant.html
KEYWORDS: Epistemic Argument, Zombies, Epiphenomenalism, Physicalism,
Common Sense Realism
ABSTRACT: This paper is trying to show that it is not possible to use
the Knowledge argument as independent evidence for the form of
non-reductionism the Modal argument argues for. To show this,
Jackson's famous 'Mary' thought experiment is imagined in a zombie
world. This leads to the result that there are many problems in the
Mary experiment, which cannot have anything to do with phenomenal
Qualia, because the Zombie-Mary would encounter them as well, and once
all these problems are accounted for, it is no longer clear whether a
Zombie-Mary is conceivable at all. Finally, an alternative explanation
for the strong non-reductive intuitions of the Mary experiment is
discussed.
1. THE EPISTEMIC AND THE MODAL ARGUMENT
Frank Jackson developed one of the most famous thought experiments in
the philosophy of mind to prove that *physicalism* must be false. In
this paper I want to argue that this thought experiment confuses two
very different ideas about non-reductionism. The first idea is
*epiphenomenalism*, i.e. the idea that there are irreducible phenomenal
facts which nevertheless do not influence our behavior, while the second
is *common sense realism*, which I take to be the idea that an
irreducible phenomenal consciousness (i.e. a consciousness that
includes phenomenal facts which are neither type nor token identical
with physical facts) is causally relevant for at least parts of our
behavior. This second alternative must, of necessity, doubt in some way
one of the central claims of physicalism, i.e. that there is in our
world a physical cause for every physical effect. If this suspicion is
correct, then the thought experiment featuring the omniscient but
blind-blind scientist Mary invokes intuitions which have nothing to do
with the first idea of non-reductionism. Understanding the experiment in
this way changes it into what Daniel Dennett has labeled an intuition
pump. It would be rendered no more than one of these "fiendishly clever
devices" which "deserve their fame, if only for their seductiveness"
(Dennett 1991, p.282). This is to say that Mary prompts intuitions of
common sense realism which obviously cannot be reconciled with the
theoretical position of epiphenomenalism. And this in the light of the
fact that the Mary experiment is used by many, including its inventor,
to support precisely this latter position.
But first of all, let us examine Jackson's argument. Imagine this
intuitively very convincing thought experiment:
"Mary is confined to a black-and-white room, is educated through
black-and-white books and through lectures relayed on black-and
white television. In this way she learns everything there is to know
about the physical nature of the world. She knows all the physical
facts about us and our environment, in a wide sense of 'physical'
which includes everything in completed physics, chemistry, and
neurophysiology, and all there is to know about the causal and
relational facts consequent upon all this, including of course
functional roles. If physicalism is true, she knows all there is to
know. For to suppose otherwise is to suppose that there is more to
know than every physical fact, and that is what physicalism denies.
Physicalism is not the noncontroversial thesis that the actual world
is largely physical, but the challenging thesis that it is entirely
physical. This is why physicalists must hold that complete physical
knowledge is complete knowledge simpliciter. For suppose it is not
complete: then our world must differ from a world, W(P), for which
it is complete, and the difference must be in non-physical facts:
for our world and W(P) agree in all matters physical. Hence,
physicalism would be false at our world (though contingently so, for
it would be true at W(P)).
It seems, however, that Mary does not know all there is to know. For
when she is let out of the black-and-white room or given a color
television, she will learn what it is like to see something red,
say. This is rightly described as learning-she will not say,
"ho,hum". Hence physicalism is false." (Jackson 1986, p.291).
It is almost impossible not to feel the intuitive force of this
experiment. Intuitively, all the physical knowledge in the world cannot
give Mary the slightest clue about the experiential feel of seeing
colors. Jackson concluded from his experiment that this feel can
therefore play no role in the functional description of our world, i.e.
that this feel must be epiphenomenal.
The thought experiment evoked a host of other philosophical
interpretations as well, many agreeing, but even more criticizing, the
conclusion of Jackson's argument. These critical voices were very
heterogeneous in themselves. They ranged from a complete denial of the
conclusion of the experiment (Dennett, 1991), through the claim that
Mary gained a new ability but no knowledge (Nemirow, 1990), to various
forms of replies that found in the Mary experiment evidence for the
intricacies of the term knowledge, knowing how and knowing that,
indexical arguments, opacity of knowledge, e.g. (Horgan, 1984; Perry,
1979).
There is much to be learned from this debate, but this paper focuses
exclusively on the question of whether the experiment can provide
independent evidence for the ontology advocated by the epiphenomenalist
<1>, as it was intended to by Jackson and as many philosophers have
thought after him. This essay is trying to provide a tool that allows
philosophers and non-philosophers alike not to get misled by the thought
experiment as easily as in the past. It wishes to argue that the Mary
experiment does not provide support for the theoretical position it was
originally designed to defend and which David Chalmers <2> has made such
a very strong and famous case for, i.e. epiphenomenalism. The Mary
experiment might be compatible with this position, but cannot provide
any evidence for it.
These points can be made by demonstrating that the intuitions Mary
evokes relate problematically to another classical piece of ammunition
within the epiphenomenalist artillery. In fact, Jackson's description of
the purely physical world W(P) is strongly reminiscent of another very
interesting philosophical creature.
Probably the only other being that has become as famous as the
conclusive proof against reductionism is the *zombie* <3>. A
philosophical zombie is, as no philosopher ever forgets to mention,
quite different from a voodoo zombie. Where the latter is essentially
something with a frighteningly different appearance and terrifying
behavior in comparison to a normal human being, the philosophical zombie
is exactly like a human being, with one small but decisive exception. It
does not have phenomenal consciousness. In some versions, philosophical
zombies are only behaviorally indistinguishable from their conscious
fellow beings whereas in other, more extreme cases, zombies are supposed
to be exact physical replicas of their conscious twins, which therefore
must be behaviorally isomorphic to their conscious counterparts as well.
Many people find these creatures difficult to imagine, so it might be
useful to emphasize once more: What sets them apart from human beings is
nothing else but a complete lack of phenomenal consciousness. Zombies do
not have *Qualia*. Qualia are conscious qualities <4> - this means that
they are the experiential properties of our feelings, thoughts,
impressions, etc. They are 'what it is like' to have all these things.
The zombie argument is supposed to show that, as it is conceivable to
imagine a world that is just like ours apart from the non-existence of
Qualia, it cannot be possible that Qualia can be reduced to something
else (typically a purely functional description) in ours.
This is not to say that zombies do not talk about Qualia! As they are
behaviorally equivalent to us, they can be imagined to talk about
consciousness just as much as we do. Only in their case, the only reason
for their doing so is the complex architecture in their brain. But all
the neural firing that is going on in their heads does not give them the
phenomenal side of consciousness.
2. ZOMBIE-MARY
Now armed with this understanding of philosophical zombies, as well as
intuitions from Jackson's thought experiment which show us why Qualia
might be a further fact that Mary comes to know about when she leaves
her black and white room, we can turn now to *Zombie-Mary* <5>.
Zombie-Mary is the perfect neuroscientist living in her black and white
world. She acts exactly like 'normal' Mary, but does not really have
black and white, or indeed any, experiences. In other words, Zombie-Mary
inhabits one of the possible worlds where there are human beings without
consciousness who behave just like we do. She lives in zombie world.
Whether or not she has got a conscious human Mary twin in our world,
whose physical replica she is, does not really matter. But it is
interesting nevertheless to note that for Jackson there is no
significant difference between silicon and neurons.<6> The physical
make-up of Zombie-Mary simply does not matter for Jackson. For him, the
possibility of conscious experience is not confined to humans. It is
imaginable that computers will be conscious one day. If that should
happen, then it would easily be imaginable that these computers have
unconscious silicon twins on W(P). Nevertheless, the force of the
example is better felt if Zombie-Mary does indeed have a conscious Mary
twin in our world.
2.1 ZOMBIE-MARY'S FIRST COLOR 'EXPERIENCE'
Imagine, therefore, a physical duplicate of Jackson's Mary on W(P). In
so doing, it should be possible to find out whether the intuitions that
normal Mary triggered had to do with the fact that she discovered
something about phenomenal consciousness, or with something else. If it
was because of phenomenal consciousness, then imagining Zombie-Mary
should not trigger any of the intuitions triggered by the original
experiment, because in Zombie-Mary's world no such thing as phenomenal
consciousness exists. If these intuitions are triggered nevertheless,
then this seems to show that phenomenal consciousness was not
responsible for them in the first place.
So, let's first of all imagine, purely intuitively, a day in the life of
Zombie-Mary:
Zombie-Mary quietly works in her black and white laboratory until one
day, a fellow zombie puts a red apple into her black and white
environment. What will happen? The only answer that is compatible with
the theoretical concept of zombies means that the following scenario
unfolds: Our zombie will jump up and shout: "Wow, that's it! That's what
it is like to see colors! I had all this knowledge about neurons. I knew
exactly which neurons fire when light waves of a certain length are
translated into neuronal information about the redness of an apple, but
I never knew what it's like to see a red apple. Isn't the world
beautiful? Redness is something so exquisite, I cannot begin to put it
in words." She will do this because she is functionally completely
identical to her conscious twin, and will therefore always do what this
twin does. So her behavior is not surprising at all. The fascinating
thing is that nothing actually seems to have caused it, as she doesn't
have the phenomenal consciousness which is seemingly responsible for
normal Mary's reaction. But on second thoughts, this is not quite true.
Actually, there is a cause for her behavior. The cause is obviously the
neurons involved in color discrimination in her unconscious brain, which
had not fired up until now, but which go crazy as the light rays
reflecting from the apple hit her retina.
Nevertheless, if this describes accurately how Zombie-Mary would react,
then in my view the story of 'normal' Mary is deeply misleading as a
thought experiment. The thought experiment suggests that the phenomenal
knowledge Mary gains will make a difference to the way she leads her
life, thinks about her life, feels about her life and so on. If it turns
out that her zombie equivalent gains just the same "knowledge" by
leaving the room, even though she obviously acquires no new
phenomenology (i.e. that leaving the room means for her the same changes
in her zombie thoughts, zombie feelings), then the experiment loses its
intuitive force. The original Mary experiment seemed to show that
consciousness makes a behavioral difference, but in fact it shows
nothing of the sort. The Zombie-Mary thought experiment shows that the
inmate of the black and white room must have been lacking something more
than phenomenal consciousness; otherwise Zombie-Mary would not lack
anything at all. But it seems clear that she does: Zombie-Mary would
acquire some new knowledge as well, she would not say, "ho, hum" any
more than normal Mary.
To many people, this simple story seems to be enough to view the Mary
experiment in a different light, but Zombie-Mary can do more. Up to now,
I have only shown that Zombie-Mary evokes intuitions that Mary evokes as
well. In the next section, the Zombie-Mary experiment will show that the
philosophical debate associated with the Mary problem nowadays does not
discuss different solutions to the same problem that Jackson saw, but
seeks to find solutions to a different problem altogether. Jackson's
idea of epiphenomenal facts must be regarded as an additional and
disconnected problem, which does not provide a further solution to the
problems of the philosophical debate aroused by or hidden in the Mary
experiment. In the section after this, I will ask the question of
whether Zombie-Mary is a possibility at all.
2.2 ZOMBIE-MARY IN THE NIDA-RUEMELIN ROOM
Imagine a slight variation on our first story. This time, Zombie-Mary's
evil fellow zombies put a switch which shows a red and a green square
into her black and white environment. She is told that moving the switch
to red will blow her world to smithereens, while moving it to green will
bring eternal happiness (whatever that may be in a zombie world). Will
she know what to do? In the normal Mary experiment, most people have the
intuition that she would not know what to do.
Martine Nida-Ruemelin (Nida-Ruemelin, 1993), for example, imagines a room
where all objects are brightly colored, but not in their natural color.
If Mary were led into such a room, she would learn about the color
phenomenon, but she would not know which color was which. If she would
not know, then neither should the behaviorally equivalent Zombie-Mary.
This seems very strange, though. Zombie-Mary knows all the facts there
are to know about colors in her physical world, so she shouldn't have a
problem with a coded-coded switch. If it is nevertheless imaginable that
she has such a problem, then it can't have to do with her imperfect
knowledge. If this is the case in Zombie-Mary's case, then the argument
does not work for normal Mary either, because she might be lacking
whatever it is that her zombie twin is lacking as well. This something
might be many things, but is certainly not phenomenal facts, which are
excluded by definition from the zombie world.
That most philosophers and non-philosophers nevertheless feel that the
*Nida-Ruemelin room* shows something interesting about the Mary
experiment shows that most people do believe that whatever it is that
the Mary experiment shows, it has to be something that has behavioral
consequences. The epiphenomenalist on the other hand, now has two
options. She can either claim that the Nida-Ruemelin room would not
work, i.e. that Mary would know where to move the switch, or she can
claim that there are many things going on at once.
If she chooses the second option, this is good news for all the
philosophers who attempted ability hypotheses or opacity of knowledge
replies to the original thought experiment, because they now have the
epiphenomenalist on their side. The epiphenomenalist then has to hold
that there is a problem with being exposed to color rays for the first
time which is absolutely independent of phenomenal consciousness,
because otherwise Zombie-Mary could not have that problem. This puts the
epiphenomenalist in an uncomfortable position, as there is now no need
at all any more to postulate phenomenal facts to solve the problems of
the experiment. As it would be clear that there are intuitions triggered
by something that has nothing to do with phenomenal consciousness, the
onus would be on the epiphenomenalist to show that it is not this
something which gives rise to the possibly mistaken impression that the
Mary experiment seems to be about phenomenal consciousness as well. The
experiment is thus at most compatible with, but not evidence for, her
position. This option is, therefore, extremely undesirable for the
epiphenomenalist.
To avoid this conclusion, she could argue instead that the Nida-Ruemelin
room would not pose a problem because Zombie-Mary, as well as conscious
Mary, would know fine well how to save the world. This option is
discussed in the next section, where we will encounter a more
fundamental problem.
2.3. BACK TO THE BLACK AND WHITE ROOM
The claim that Mary could save the world in the Nida-Ruemelin room has
been made before, but the author of the claim seems to be the most
unlikely candidate for a defendant of any form of non-reductionism.
Daniel Dennett (Dennett, 1991) argues that most people (even hardened
philosophers) understand Mary in such a way that she couldn't say which
of her first two color experiences was the red one without any further
clues. This impression, says Dennett, is wrong. Instead, he argues, Mary
would be able to distinguish between the two colors just because of her
physical knowledge. If the experimenters were to put a blue banana in
her room, she would exclaim: "Don't trick me! I know bananas are not
normally blue". It seems obvious that this ending to the experiment
should mean that its original purpose had failed, but this not a
necessary conclusion.
David Chalmers, for example, holds that Dennett's argument, far from
endangering the epiphenomenalist position, even enforces the
epiphenomenalist view by showing that the ability hypotheses (Nemirow,
1990) must be wrong (Nemirow claims that Mary acquires a new ability but
no new knowledge in the original experiment) without ever touching the
phenomenal side of Chalmers' argument p.145. Chalmers argues that the
intuitions triggered by the Mary experiment are completely independent
of her behavior in any room and arise only because there is the
particular phenomenal feel that accompanies her behavior. To place this
in the context of our Nida-Ruemelin example: Dennett argues that the
Nida-Ruemelin room would not pose a problem for Mary, because she would
have the relevant abilities to use the switch. But even if that should
hold true (as we know by now it should, if the epiphenomenalist wants to
have an interesting case), it does nothing to prove that she also has
the knowledge of what it is like to have a color experience (Chalmers,
1996b).
According to Chalmers, Dennett's argument only hits the mark if one
accepts the ability hypothesis about phenomenal experience in advance
(i.e. if one accepts that having the ability to distinguish between
colors is all there is to have), because only then would it be true that
there would be no additional fact for Mary to learn once she has the
ability to distinguish between colors. If that were the case, then
Dennet's argument would show that the thought experiment is flawed,
because it concludes that Mary does not have an ability which she really
would have. But to accept the ability hypothesis as a premise is to
accept the conclusion as a premise, and would therefore be question
begging. It would mean that any argument against materialism in this
context would have already failed before the experiment had even begun.
As it is, Dennett's argument is beside the point, because Mary's having
the ability to distinguish between colors does not mean that she has
everything there is to have, because she still might be lacking the
phenomenal side of this ability.
This is, as it stands, a valid argument against Dennett.<7>
Nevertheless, there are still some puzzling results, even if we do not
take the ability hypothesis premise for granted, as Chalmers suggests.
This is illustrated quite well if we compare Mary to her zombie twin
once more.
2.4. THE FALSE BELIEFS OF (ZOMBIE) MARY
If Mary has the ability to recognize blue even before she leaves her
room, this could mean three things:
1) The zombie, faced with a blue banana, could observe her own behavior
and then conclude: I react in this specific way because my system has
been exposed to waves which create a blue functional state. But this
option has undesirable consequences. It means that Mary would use
exactly the same deductive mechanisms, because otherwise she would not
be equivalent to Zombie-Mary any more, which in turn means that her
belief about what is like to see blue does not stem from the phenomenal
experience, but from her clever deductions. This could now either be
true, in which case physicalism would be true as well, or it could be
false and Mary actually learned something from her phenomenal experience
(and just managed to deceive herself about her surprise when she learned
this new and unexpected phenomenal fact). Nevertheless, this alternative
renders the original premise, that Mary knows everything physical there
is to know about color perception, incorrect, because she would now
mistakenly believe that she had learned something as a result of her
deductions, when she really learned something for very different
reasons. This means: She believes in a physical fact P that does not
exist. Therefore, she does not know the physical fact that -P is the
case. This possibility is therefore not a possibility after all.
2) Another option might be that Zombie-Mary acquires the ability because
of her knowledge, but believes that she has it because of the phenomenal
impression (she would believe that she just had a surprising phenomenal
experience). This would save the original Mary experiment, because Mary
could now rightly believe that she learned a new phenomenal fact, but it
has one major fault for Zombie-Mary. She would then have acquired a
false belief about her perceptions: This is because she lives in a world
that is per definition only physical and believes in a non-physical
reason for her belief, but this renders the premise that Zombie-Mary
knows everything there is to know about perception wrong. If she holds a
false belief, then she obviously does not know the true state of affairs
about why she holds a certain belief connected to her perceptions.
3) It seems to me that there is only one possibility to avoid such a
dilemma. One would have to argue that there is something wrong with the
idea of a Zombie-Mary itself. This could be because it does not make
sense to talk of knowledge in the zombie world or it could be because a
Zombie-Mary or a Mary are not possible for contingent reasons, or
because somebody who has complete physical knowledge would know whether
she is a zombie or not. All these options have undesirable side effects,
but they are not the topic of this essay.
The purpose of this essay is only to show that the Mary argument does
not provide support for the zombie ontology. This goal seems achieved.
Not only do the two experiments not provide any support for each other,
but they actually seem to be fully incompatible.
2.5. PRIMARY CONCLUSIONS
Zombie-Mary destroyed bit by bit the idea that the Mary experiment
really can be used as an argument for the ontology advocated by the
zombie argument. First of all, she could show that the intuitions
triggered by Mary are triggered by Zombie-Mary as well. This seems to
indicate that these intuitions are triggered because of a feature both
Marys share, and not by the feature that sets them apart. Secondly,
Zombie-Mary could show that all the ingenious solutions that have been
thought about for the Mary problem would apply to her as well and
therefore, all these problems cannot be the problems that are so special
in phenomenal consciousness. Finally, it turned out that there are some
real problems in the very idea of Zombie-Mary, because it seems that
either she or her conscious counterpart must have a false belief about
their knowledge of colors. This seems to be incoherent, considering the
fact that both of them know everything physical there is to know about
color perception.
If my arguments succeed up to now, then I have shown that Mary does not
provide an argument for epiphenomenalism at all. This is in itself an
important result, but it can be made more plausible by providing a
positive explanation for the intuitions triggered by the Mary
experiment. If it is not epiphenomenalism, what else might it be? This
is the question for the remainder of this essay.
3. THE ' WHAT IS IT LIKE' ARGUMENT
At the very beginning of the Zombie-Mary story, it turned out that we
find the Mary experiment intuitively plausible, not because of
epiphenomenalist Qualia, but because of some important changes in her
life which dramatically change what it is like to be Mary. This
formulation is reminiscent of Thomas Nagel's famous 'what is it like to
be a bat' argument (Nagel, 1974), and I want to argue that Mary's story
and the *what-is-it-like* argument do in fact invoke similar intuitions
for similar reasons on one specific reading. This fact in itself is not
very instructive though, because some epiphenomenalists (like Chalmers
(Chalmers, 1996b)) also see the Knowledge argument as merely one form of
the more general what-is-it-like argument. Nevertheless, Jackson himself
believes that there is a difference between his idea of Nagel's argument
and the Knowledge argument. Jackson's position might be less consistent
here than Chalmers' is, but Jackson's differing intuitions about both
experiments are very instructive. Jackson believes that the
what-is-it-like argument points towards physicalism, but the arguments
he provides for that claim could, on closer analysis, also be used to
defend the non-reductionist position of common sense realism. I argue
that it is this position and not epiphenomenalism which provides the
background for the incredibly strong intuitions that are triggered by
what-is-it-like arguments and Knowledge arguments alike.
Jackson differentiates between his Knowledge argument and
what-is-it-like arguments because Jackson understands the Mary
experiment, like Chalmers, in the epiphenomenalist way I have been
discussing, but has a different understanding of the what-is-it-like
argument. He tries to illustrate the difference by invoking another
thought experiment about a guy called Fred, who sees two different
colors where other people see only red. Again, the argument seems very
plausible, because Fred can consistently sort out piles of cards in red
and his special color. Jackson wants to understand Fred as a similar
example to Mary, which shows the intuitive plausibility of the idea that
Qualia are irreducible facts, but he insists that 'what-is-it-like
arguments' work in a different way:
"It is important to distinguish this argument [the what-is-it-like
argument] from the Knowledge argument. When I complained that all
the physical knowledge about Fred was not enough to tell us what his
special color experience was like, I was not complaining that we
weren't finding out what it is like to be Fred. I was complaining
that there is something about his experience, a property of it, of
which we were left ignorant. And if and when we come to know what
this property is we still will not know what it is like to be Fred,
but we will know more about him. No amount of knowledge about Fred,
be it physical or not, amounts to knowledge "from the inside"
considering Fred. We are not Fred. There is thus a whole set of
items of knowledge expressed by forms of words like 'that is I
myself who is...' which Fred has and we simply cannot have because
we are not him. When Fred sees the color he alone can see, one thing
he knows is the way his experience of it differs from his experience
of seeing red and so on; another is that he himself is seeing it.
Physicalist and qualia freaks alike should acknowledge that no
amount of information of whatever kind that others have about Fred
amounts to knowledge of the second. My complaint though concerned
the first and was that the special quality of his experience is
certainly a fact about it and one which Physicalism leaves out
because no amount of physical information told us what it is.
Nagel speaks as if the problem he is raising is one of extrapolating
from knowledge of one experience to another, of imagining what an
unfamiliar experience would be like on the basis of familiar ones.
In terms of Hume's example, from knowledge of some shades of blue we
can work out what it would be like to see other shades of blue.
Nagel argues that the trouble with bats et al. is that they are too
unlike us. It is hard to see an objection to Physicalism here.
Physicalism makes no special claims about the imaginative or
extrapolative powers of human beings, and it is hard to see why it
need do so." (Jackson, 1982, p.132)
Obviously, Jackson did not want his thought experiments to be compatible
with physicalism. According to Jackson's interpretation of the
what-is-it-like argument, physicalism and Nagel's argument are quite
compatible; therefore, his own Knowledge argument must be about
something fundamentally different. The following will try to show that
the difference between Fred and Fred's ability to see an additional
shade of red might be less clear than Jackson suggests, even though
intuitively Jackson's differentiation between a specific phenomenal
percept and the perceiver seems very plausible. This will be helpful,
because it will pave the way for a form of non-reductionism that does
not rely on such a distinction.
Is it really true then, that perceiver and percept can be so strictly
separated? To answer this question we turn now to Zombie-Mary's cousin,
Zombie-Fred. Consider: Fred has a special cone in his visual system that
allows him to differentiate between red one and red two. After he dies,
this cone is transplanted into Anne's system. Anne tells us now what it
is like to see red one and two. Two years later, the zombie detector <8>
is found, which can distinguish zombies from other people. It turns out
that Fred was a zombie, but Anne is not. Now Anne is shocked. How can it
be that Fred didn't really see all the beautiful colors she can see,
even though he had the same cone? She realizes that from the beginning
red one and red two had nothing to do with the cone but with the system
that used the cone. In Fred the cone did nothing special, because he was
a zombie. She shudders, because she realizes that, when she wanted to
see what Fred saw, what she wanted to see was the phenomenal blackness
that a zombie sees.
Jackson leads his readers down the wrong track when he emphasizes the
difference between the cone and Fred.<9> He gives the impression that
the cone is just a tool, whereas the person is the subject. This is a
classical Cartesian fallacy. The cone is no more or less a tool than
Fred's whole brain, or sunglasses that Fred might have worn. Postulating
a subject behind the information-processing brain is postulating a
Cartesian homunculus. What Anne actually wanted to know was what it
would be like to be her with such a cone, or perhaps what it would be
like for Fred to have the cone. In any case, she always wanted to know
what it would be like to be a person in a certain state. The problem was
that she did not realize the importance of the perceiving system. She
did not realize that she was not interested in what the cone does on its
own, but in the cone integrated in her (or another) system. She did not
realize that she had no idea what it would be like to be her with the
cone. There is nothing like the perception of colors that does not
presuppose the entire perceiving system.
If such a difference should be impossible, then Jackson might have been
right to believe that the what-is-it-like argument could be compatible
with physicalism, but he incorrectly postulated a difference between the
what-is-it-like argument and the Knowledge argument. In fact, the notion
both arguments are not compatible with, if they are understood as
suggested above, is the notion of zombies, indeed, the zombie idea can
be used to call the whole structure of the what-is-it-like argument into
question. The zombie argument seems to show that it is possible to see
more in a qualitative experience than a problem of an individual
perspective. It seems to show that there might be something to
qualitative experiences which is completely independent of the
experiencing system.
4. COMMON SENSE REALISM
If one wants to endorse a form of non-reductionism which is compatible
with the idea that experiences cannot be seen as separate entities from
experiencers, then one has to believe in something which I want to call
common sense realism. Common sense realism starts from the premise that
people with phenomenal consciousness cannot have a zombie equivalent. If
this should be true, then the Mary and Fred experiments might still
point to something interesting, but zombies are out of the game.
Phenomenal consciousness would, in every possible world, result in at
least one functional difference between zombies and us, but this would
be the end of the zombie as defined in philosophical terms. This in turn
would mean that there is something deeply wrong with the
epiphenomenalist idea of consciousness.
If one wants to hold that Mary learns a new fact, although she had all
the physical facts available, then Mary could be understood as showing
that reductive materialism must be wrong, because the right causal story
must contain essentially perspectivic facts, i.e. it must take into
account that the world is not completely describable in third person
terms, because there is a form of causation which can only be described
in first person terms. But for this very same reason, epiphenomenalism
insults our basic intuitions as well, because the definition of
epiphenomenalism requires that phenomenal consciousness be never
involved in causation.<10> This reading is so intuitively plausible
because with it, one can construct a functional role for consciousness
that satisfies common sense realism. That this role is not describable
in scientific terms, for reasons of essential perspectiveness, adds to
the intuitive appeal of such a solution to folk psychology.
Nevertheless, like all philosophical positions on consciousness, such a
reading has not only the desired consequences, but some highly
undesirable side effects as well. In this case, it is the problem that
such a position has to surrender an understanding of function that is
describable purely in third person perspective terms. This is a very
high price to pay to justify the intuitions of the what-is-it-like
argument. I do not want to attempt to defend such a position, nor am I
convinced that it is worth defending, but I believe that only this
non-reductive position does justice to the intuitions of Nagel's
argument.
5. CONCLUSION
David Chalmers has held that different forms of non-reductionism can be
combined to form a stronger argument for non-reductionism. This paper
could show that this is at least not always the case. The combination of
two classical non-reductionist thought experiments, i.e. the zombie and
Mary experiments, showed that the Mary experiment does not, by any
means, provide independent support for the ontology advocated by the
zombie argument. The Zombie-Mary thought experiment showed that it is
not because of epiphenomenal Qualia that we find the Mary experiment so
fascinating, but because of changes in Mary's life that have to be
independent of phenomenal consciousness, because we can imagine them for
Zombie-Mary as well. What is more, after separating the real problem of
phenomenal facts from all the other interesting features of the Mary
thought experiment, it turned out that the idea of an omniscient color
scientist might actually be incompatible with the idea of a zombie
equivalent of that person.
On the contrary, Mary invokes intuitions that are useful for theoretical
positions like common sense realism, which are strictly incompatible
with the zombie idea because they assume that phenomenal consciousness
will make a functional difference in every possible world. The paper did
not try to defend such a position, but it wants to point out that it is
obviously impossible to have it both ways. Common sense realism is
intuitively very plausible, but faces massive problems if we want to
integrate it into our scientific worldview. A position like
epiphenomenalism may be philosophically very sophisticated, but it has
to give up the pretence that the non-reductionism it defends saves the
more important parts of common sense realism along the line. It does
not! As we have seen, common sense realism is plausible precisely
because of the assumption that epiphenomalism denies, i.e. the idea that
our phenomenology does effect our behavior. The two non-reductionist
positions do not stand united against physicalism, but are every bit as
incompatible with each other as physicalism is with one of the two.
I think this is an important result, and not only because it clarifies
the status of a classical thought experiment in the philosophy of mind.
It is also important because many non-philosophers have been attracted
to the epiphenomenalist position because of the Mary experiment, and I
hope that the Zombie-Mary story provides them with a tool to check
whether it really was the epiphenomenalist intuition that they found
convincing.
NOTES
<1>. The conceivability of a zombie world is a necessary condition for the
coherence of the epiphenomenalist position. But epiphenomenalism makes
even stronger claims as well: the conceivability of a zombie world only
shows that there might be a world in which function and phenomenology
are completely separated, but this does not entail that our world has to
be such a world, as epiphenomalists hold. As my arguments make use of
the weaker zombie argument, every result I achieve counts a fortiori
against epiphenomenalism.
<2>. Chalmers does not believe that epiphenomenalism is the only possible
non-reductionist position, but most of his anti-reductionist arguments
are typical epiphenomenalist arguments.
<3>. David Chalmers has an excellent and extensive zombie literature page
at: http://www.u.arizona.edu/~chalmers/zombies.html.
<4>. (Rosenthal, 1997) holds that there is something like unconscious
qualitative discriminations. Whether these discriminations should be
called Qualia is unclear. For present purpose, I want to avoid this
debate by defining Qualia as conscious.
<5>. Zombie-Mary has been used before. Steven Ravett Brown makes the point
that the Qualia explanation of the thought experiment is redundant,
because we have a better and more probable physical one. I agree, but I
do not believe that this is the interesting problem in the Mary case.
Brown's argument is a standard argument against epiphenomenalism, but it
does not take into account the intuitive plausibility of the Mary case,
which stems from another source, which I believe to be what-is-it-like
intuitions. Brown's argument and a couple of replies, including one from
Chalmers, are available at
http://www.ai.sri.com/~connolly/psyche-list-archive/1998a/0231.html.
<6>. Chalmers is another adherent of this argument. He proposes it
explicitly in (Chalmers, 1996a).
<7>. Nevertheless, Dennett was on the right track. He assumed correctly
that the question of epiphenomenalist Qualia cannot be settled in the
Nida-Ruemelin room.
<8>. Whether a zombie detector is conceivable is by no means clear. It
might be strictly impossible to develop anything that could distinguish
between zombies and normal people. But even if that should be the case,
the argument doesn't suffer. It is enough that Anne realizes that Fred
could have been a zombie and what that would have meant for her desire
to see what Fred saw.
<9>. A similar mistake has often been made in interpreting Nagel's bat
example. Martine Nida-Ruemelin (Nida-Ruemelin, 1993) for example, holds
that we cannot understand bats, because we do not know what the percepts
of the sonic radar would be like. But Nagel's point is not the problem
of what it is like to have a sonic radar, but the problem of what it is
like for a bat to have sonic radar.
<10>. I take Naomi Eilan to argue in that direction. (Eilan, 1995).
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