What RoboMary Knows[1]
Frank Jackson’s thought experiment
about Mary the color scientist is a prime example of an intuition pump, a
thought experiment that is not so much a formal argument as a little scenario
or vignette that has been pumping philosophical intuitions with remarkable
vigor since it first appeared in 1982. For sheer volume and reliability, this
must count as one of the most successful intuition pumps ever devised by
analytical philosophers. But is it a
good intuition pump? How could we tell? Douglas Hofstadter’s (1981) classic advice to
philosophers confronted by a thought experiment is to treat it the way
scientists treat a phenomenon of interest: vary it, turn it over, examine it
from all angles, and in different settings and conditions, just to make sure
you aren’t taken in by illusions of causation. During the last twenty years,
philosophers have examined many variations and defended many different
responses, but they have singularly neglected some of the possible settings of
the knobs. More than a decade ago, I
conducted a preliminary exploration of the knobs, and issued a kill-joy verdict
that has been almost universally disregarded: “Like a good thought experiment,
its point is immediately evident even to the uninitiated. In fact it is a bad
thought experiment, an intuition pump that actually encourages us to
misunderstand its premises!” (Dennett, 1991, p398) In fact it is much more
difficult to imagine the scenerio correctly than people suppose, so they
imagine something easier, and draw their conclusions from that mistaken base.
In an attempt to bring out the flaws in the thought experiment, I encouraged
people to consider a variant ending:
And so, one day, Mary’s captors decided it was time for
her to see colors. As a trick, they prepared a bright blue banana to present as
her first color experience ever. Mary took one look at it and said ‘Hey! You
tried to trick me! Bananas are yellow, but this one is blue!” Her captors were
dumfounded. How did she do it? “Simple,” she replied. “You have to remember
that I know everything–absolutely everything–that could ever be known
about the physical causes and effects of color vision. So of course before you
brought the banana in, I had already written down, in exquisite detail, exactly
what physical impression a yellow object or a blue object (or a green object,
etc.) would make on my nervous system. So I already knew exactly what thoughts
I would have (because, after all, the ‘mere disposition’ to think about this or
that is not one of your famous qualia, is it?). I was not in the slightest
surprised by my experience of blue (what surprised me was that you would try
such a second-rate trick on me). I realize it is hard for you to imagine
that I could know so much about my reactive dispositions that the way blue
affected me came as no surprise. Of course it’s hard for you to imagine. It’s
hard for anyone to imagine the consequences of someone knowing absolutely
everything physical about anything!’” (p399-400)
It is standardly assumed that things
could not proceed this way. As
First, I have found that some
readers–maybe most–just didn’t get my blue banana alternative.[2] What was I saying? I was saying
that Mary had figured out, using her vast knowledge of color science, exactly
what it would be like for her to see something red, something yellow,
something blue in advance of having those experiences.[3] I asserted this flat out--in
your face, as it were–in order to expose to view the fact that people
normally assume that this is impossible on the basis of no evidence or theory
or argument, but just on the basis of ancient philosophical tradition going
back at least to John Locke. Perhaps a little dialogue would help bring out the
intended point:
TRAD: What on earth do you mean? How
could Mary do that?
DCD: It wasn’t easy. She deduced it, actually, in a
4765-step proof (for red–once she’d deduced what red would look like to her,
green fell into line with a 300-step lemma, and the other colors–and all the
hues thereof–were relatively trivial extensions of those proofs).
TRAD: You’re just making all that
up! There are no such proofs!
DCD: This is a thought experiment; I get to make up all
sorts of things. Can you prove that there are no such proofs? What established fact or principle am I
contradicting when I help myself to a scenario in which she deduces what colors
would look like to her from everything she knows about color?
TRAD: Look. It’s just obvious! You can’t deduce what a
color looks like if you’ve never seen one!
DCD: That’s an interesting folk theorem, I must say.
Here’s another: If you burp, sneeze and fart all at the same time, you die.
Both sound sort of plausible to me, but is there any scientific backing for
either one of them?
1.
She’ll be surprised, dammit!
If the Mary thought experiment was
intended simply to draw out and
illustrate vividly the implications of a fairly standard way of thinking
that many, probably most, people have, it might be a useful anthropological
exercise, an investigation of folk psychology laid bare. But those who have
championed Mary have thought that it might actually prove something bigger, not
just the conclusion that most people’s unexamined assumptions imply dualism--I
think we already knew that, but maybe not--but the conclusion that dualism is
true! The fact that philosophers would
so much as entertain such an interpretation of such a casual exercise of
the imagination fills me with astonishment. I had no idea philosophers still
put so much faith in the authority of their homegrown intuitions. It is almost
as if one thought one could prove that the Copernican theory was false by
noting that it “seems just obvious” that the earth doesn’t move and the sun
does.
Consider, for instance, the recent
article “Mary Mary Quite Contrary,” by
George Graham and Terence Horgan (2000) Graham and Horgan (G&H henceforth)
have usefully managed to distill precisely the unargued intuition that I have
been attempting to isolate and discredit for fifteen years and more–the one we
might express as “She’ll be surprised, dammit!” G&H begin by distinguishing
two main materialist responses to Mary: thin and thick materialism. Thin
materialism, of which I am one of the few exponents, denies that Mary learns
anything post-release. Thick materialists attempt to salvage materialism while
going along with the gag that Mary is startled, delighted, surprised, or
something like that, when she is released from her colorless captivity.
G&H’s strategy is first to declare briskly that thin materialism is a
non-starter in need of no refutation since it “has been amply criticized by
others,” (p63). The only critics they list are McConnell (1994) and Lycan
(1996). Since I replied at some length to McConnell in the same journal
(Dennett, 1994), and since Lycan doesn’t criticize my version of thin
materialism, I don’t find this criticism ample, but I must admit that G&H
are only going along with the mainstream in ignoring my brand of thin
materialism. That’s why the current essay is necessary.
G&H spell out the best of the
thick materialist campaigns–Michael Tye’s PANIC–and imagine their own variation
on the original theme: Mary Mary, the daughter of the original Mary, and a
devotee of Tye’s brand of thick materialism. According to Tye’s PANIC theory,
“phenomenal character is one and the same as Poised Abstract Nonconceptual
Intentional Content” (Tye, 1995, p137), which means roughly that it is content
that is “in position to make a direct impact on the belief/desire system” and
is about non-concrete, non-conceptualized discriminable properties. If follows from Tye’s view, they claim, that
Mary Mary, upon release, shouldn’t be surprised. As they say, “In the
end, Tye’s version of thick materialism is just too thin. And this
problem threatens to arise for any materialist treatment of phenomenal
content.” (p77).
I had previously viewed Tye’s
alternative to my brand of thin materialism as giving too much ground to the
qualophiles, the lovers of phenomenal content, but thanks now to G&H I can
welcome him into my underpopulated fold as a thin materialist malgré lui,
someone who has articulated much more painstakingly than I had just what sorts
of functionalistically explicable complexities go to constitute the
what-it-is-likeness, the so-called phenomenality, of conscious
experience. I applaud G&H’s analysis of Mary Mary’s predicament, leading inexorably to the conclusion that
since she already knows all the facts, has all the information needed to have
anticipated all the noticeable, remarkable-upon properties of her debut
experience in a colored world, she should not, in spite of what Tye claims, be
(or expect to be) surprised. Here, in a nutshell, is what they say:
First, what is psychologically significant about the
PANIC properties is just the functional/representational role they play in
human cognitive economy–something that Mary thoroughly understands already, by
virtue of her scientific omniscience. . . . . Second, what is psychologically
significant about phenomenal concepts (given Tye’s theory) is that they are capacity-based
concepts; . . . . But she already understands these capacities thoroughly,
including how PANIC states subserve them, even though she does not possess the
capacities herself. No expected
surprises there, either.
Third,
the psychological distinctiveness of beliefs and knowledge-states employing
phenomenal concepts is completely parasitic (given Tye’s theory) upon the
capacity-based nature of the phenomenal concepts. So she already understands well the nature
of these beliefs and knowledge-states . . . . So Mary Mary, as a True Believer
in Tye’s PANIC theory of phenomenal consciousness, has no good reason to expect
surprise or unanticipated delight upon being released from her monochrome
situation. (p71-2)
In short, Tye should join me in
predicting that Mary Mary, like her mother Mary, would not be surprised
or delighted at all. She’s been there, done that, in her vast imagination
already, and has nothing left to learn.
So what’s the problem? Why don’t G&H join Tye and me? (I’m presuming for the fun of it that Tye is
now on my side.) Because–and here comes the super-pure, double-distilled
intuition that I’ve been gunning for–“Surely, we submit, she should be both
surprised and delighted.” (p72)
“Surely.” As I noted in “Get
Real” (Dennett, 1994) in one of my many commentaries on Ned Block, “Wherever
Block says ‘Surely,’ look for what we might call a mental block.” (p549). Block
is perhaps one of the most profligate abusers of the “surely” operator among
philosophers, but others routinely rely on it, and every time they do a little
alarm bell should ring. Here is where the unintended sleight-of-hand happens,
whisking the false premise by the censors with a nudge and a wink. G&H do
pause momentarily to ask why they are so sure, and this is what they answer:
What will surprise and delight Mary Mary . . . . is (it
seems to us) the unanticipated experiential basis of her concept-wielding,
recognitional/discriminatory, capacities and the acknowledged richness of her
experience; she never expected polychromatic experience to be like this.
(p72)
I know
that it seems to many people that there is this extra “richness,” this “experiential
basis” over and above all the PANIC details, but I have claimed that they
are just wrong about this, and I have offered a diagnosis of the sources of
this deep-seated theorists’ illusion. In
“Quining Qualia” (Dennett, 1988), I discussed
the example of the torn Jell-O box, half of which has shape property M,
and the other half of which is the only practical M-detector: the shape
may defy description but it is not literally ineffable or unanalyzable;
it is just extremely rich in information. It is a mistake to inflate practical
indescribability into something metaphysically more portentous, and I have been
urging people to abandon this brute
hunch, tempting though it may be. G&H cannot bring themselves to abandon
the intuition, but more important, they cannot even bring themselves to
acknowledge that their whole case thus comes down to simply announcing their
continued allegiance to a claim that, whether it is true or false, has been
declared false and hence could use some support. They offer no support for it,
but they do keep coming back to it, again and again:
Although
phenomenal states may indeed play a PANIC role in human psychological economy,
their phenomenal character is not reducible to that role. It is something more,
something surprising and delightful. (p73)
Who says? This is
just what I have denied, at length.
Its
greater richness is what is surprising and delightful about it, and Tye’s
theory leaves this out. (p73)
This
“greater richness” is just what needs to be demonstrated, not assumed. After
all, the point of the Mary example is supposed to be that although thanks to
her perfect knowledge she can anticipate much of what it will be like to
see colors, she cannot anticipate it all. Since some of us have claimed
that there is no reason to deny that all the “greater richness” is
accessible to Mary in advance, this bald assertion by G&H is
question-begging. It simply won’t do to lean on the obvious fact that under
normal circumstances, indeed under any circumstances except the wildly
improbable extreme circumstances of this thought experiment, Mary would learn
something.
But she will experience surprise and unanticipated
delight, upon release from her monochromatic environment–which presumably
should lead her to repudiate the materialist theory she previously accepted.
(p74)
So they say. Now thin materialism
may, in the end, be false, but you can’t argue against it by just saying
“Surely not!” I have claimed that the
richness we appreciate, the richness that we rely on to anchor our acts of
inner ostension and recognition is composed of and explained by
the complex set of dispositional properties that Tye has called PANIC
properties. G&H make the mistake of assuming that there is, in addition to
all this, a layer of “direct acquaintance” with “phenomenal properties.” They
say baldly:
There is also direct acquaintance with phenomenal
character itself, acquaintance that provides the experiential basis for those
recognitional/discriminatory capacities.(p73)
And
also:
She claims to be delighted . . . . Auto-phenomenology
suggests strongly, very strongly, that she is right about this: the
intrinsic phenomenal character of color experience is distinct from, and
provides the basis for, these recognitional/discriminatory capacities. (p77)
This is,
according to me, just about backwards. These capacities are themselves the
basis for the (illusory) belief that one’s experience has “intrinsic phenomenal character,” and we
first-persons have no privileged access at all into the workings of these
capacities. That, by the way, is why we shouldn’t do auto-phenomenology. It
leads us into temptation: the temptation to take our own first-person
convictions not as data but as the undeniable truth.
So on his [Tye’s] story, Mary Mary’s post-release
heterophenomenological claims evidently must be viewed as rationally
inappropriate, and thus as embodying some kind of error or illusion. That is
the basic problem: the apparent failure to provide adequate theoretical
accommodation for the manifest phenomenological facts. (p77)
The
basic problem, they say, is dealing with these “manifest” facts, but it’s only
a problem if, in fact, she will learn something. It is not a problem for my
view (and Tye’s, if he’ll join the thin materialists); she won’t learn
anything, and won’t be surprised; there are no such manifest phenomenological
facts. At this point, if you are like many of my students, you are beset with
frank incredulity. Of course Mary learns something on release! She has
to! Oh? Then please give me an
argument, based on premises we can all accept, that demonstrates this. But I
have never seen such an argument even attempted. “It stands to reason!” people
say, and then they decline to offer any reasons, thinking them somehow uncalled
for. I call for them.
In response to the previous
paragraph in an earlier draft, Bill Lycan has answered the call:
Here's a way to see why some of us think Mary does learn
something. What one knows when one knows
w.i.l. [what it's like] to experience a blue sensation is ineffable; at least,
it's very tough to put into (noncomparative) words. One resorts to the
frustrated demonstrative: "It's like...this." The reason physically omniscient Mary doesn't
know what it’s like is that the ineffable and/or the ineliminably demonstrative
can't be deduced, or even induced or abduced, from a body of impersonal
scientific information. (personal communication)
I daresay that Lycan speaks for many
who are sure that Mary learns something, so now we have an explicit rendering
of a background presumption of ineffability and an illustration of the role it
plays in the argument I call for. Now what about that argument? First of all,
nobody could deny that these propositions ventured by Lycan are large
theoretical claims, not minimal logical intuitions, or the immediate,
unvarnished judgments of experience. What one knows when one knows what it’s
like to experience a blue sensation is ineffable. I suppose the concept of ineffability being
appealed to here would get elaborated along these lines:
It is
not the case that there is a string of demonstrative-free sentences of natural
language, of any length, that adequately expresses the knowledge of what it is
like to experience a blue sensation.
One
would like to see that proved. (I’m being ironic. Of all the things one might
want to construct a formal theory of, ineffability is way down the list,
but it might be worthwhile to consider the difficulty of any such undertaking.)
Presumably one wants to contrast the ineffability of what it’s like to
experience a blue sensation with, say, the ready effability (if I may) of what
it’s like to experience a triangle.
Someone
who has never seen or touched a triangle can presumably be told in a few
well-chosen words just what to expect, and when they experience their first
triangle, they should have no difficulty singling it out as such on the basis
of the brief description they had been given. They will learn nothing. With
blue and red it is otherwise–that, at any rate, is the folk wisdom relied upon
by
2. You had to be there
Another unargued intuition exploited
by the Mary intuition pump comes in different varieties, all descended inauspiciously
from Locke and Hume (think of Hume’s missing shade of blue). This is the idea
that the “phenomenality” or “intrinsic phenomenal character” or “greater
richness”–whatever it is–cannot be constructed or derived out of lesser
ingredients. Only actual experience (of color, for instance) can lead to the
knowledge of what that experience is like. Put so boldly, its
question-beggingness stands out like a sore thumb, or so I once thought, but
apparently not, since versions of it still get articulated. Here are two, drawn
from Tye and Lycan:
Now, in the case of knowing via phenomenal concepts,
knowing what it is like to undergo a phenomenal state type P demands the
capacity to represent the phenomenal content of P under those concepts. But one
cannot possess a predicative phenomenal concept unless on has actually
undergone token states to which it applies. (Tye, p169)[4]
As Nagel emphasizes, to know w.i.l., one must either have
had the experience oneself, in the first person, from the inside, or been told
w.i.l. by someone who has had it and is psychologically very similar to
oneself. (Lycan, forthcoming)[5]
The role of this presupposition is
revealed in the many attempts in the literature to guarantee that Mary doesn’t
cheat, somehow smuggling the experience of color into her cell. What
special care must be taken to prevent Mary from taking surreptitious sips from
the well of color? The blockades erected
by Jackson in his original telling have long been recognized as insufficient as
they stand. Mary might, for instance, innocently rub her closed eyes one day
and create some colored “phosphenes” (try it–I just got a nice deep indigo one
right in the middle of my visual field). Or she might use her vast knowledge to
engage in some trans-cranial magnetic stimulation of her color-sensitive
cortical regions, producing even gaudier effects for her to sort out. Should a sophisticated alarm system be
installed in her brain, to cut short any dream “in color” that she might innocently
wander into by happenstance? Is it in
fact possible for a person to dream in color if that person has never seen
colors while awake? (Whaddya think? Some might be tempted to respond: “Naw. The
colors have to get in there through open eyes in order to be available
for later use in dreaming.”–that’s the Lockean premise laid bare, and
presumably nobody would be seduced by it in such a raw form today.) If Mary’s color vision system is still
intact–a non-trivial empirical assumption, given what is known about the ready
reassignment of unused cortical resources in other regards–then she already has
“in there” everything she needs to experience color; it just hasn’t been
stimulated. (That, at any rate, is the stipulation on which the thought
experiment depends, however unrealistic it may be empirically.) A dream could
trigger the requisite activity as readily, presumably, as any external stimulus
to the open eyes. There are no doubt myriad ways of short-circuiting the
standard causal pattern and producing color experience in the absence of external
world color.
More ominously for the prospects of
the thought experiment, there are no doubt myriad ways of adjusting the
standard causal pattern to produce some state of the brain that is almost
the same as the sort of state that underlies standard color experience, but
that differs in ways that subvert the clarity of the scenario and what it is
meant to prove. What started out as a crisp, clean, “intuitive” predicament is
being pulled out of shape by the inconvenient complications of science. According
to the original thought experiment, it is the subjective, internal experience
of color, however produced, that is held to be a prerequisite for
knowing what it is like to see red, but now that this thesis has lost its naive
anchoring in eyes-open-and-awake, it cannot so readily be distinguished from
other states of mind that have many of the effects of experiences of color
without clearly being experiences of color.
To take the most obvious case, if you right now imagine you are seeing a
red rose, do you thereby experience red?
(Here is an argument, if a need for one is felt: imagining anything is
having an experience, so imagining a red rose is having an experience as of a
red rose, which is different from having an experience as of a yellow rose, and
the difference must be that in the former case of imagining, you have an
experience of red.) As plausible as this
can be made to seem, if it is endorsed, triviality looms for the Mary argument:
To know what it is like to experience red is to imagine what it is like and
imagine it correctly; but to imagine experiencing red just is to
experience red, so it follows trivially that you can’t know what it is like to
experience red until you have experienced red.
We are told that Mary in her cell
can’t imagine what it’s like to experience red, try as she might. But suppose she doesn’t accept this
limitation and does try her best, cogitating for hours on end, and one day she
tells us she just got lucky and succeeded. “Hey,” she says, “I was just
day-dreaming, and I stumbled across what
it’s like to see red, and, of course, once I noticed what I was doing I tested
my imagination against everything I knew, and I confirmed that I had, indeed,
imagined what it’s like to see red!”
Doubting her, we test her by showing her a display of three differently
colored circles, and she immediately identifies the red one as red.[6] What would we conclude?
A. Jackson was wrong; Mary can figure out what
it’s like to see red in the absence of any experience of red; or
B.Mary
didn’t figure out what it is like to see red; she had to resort to
(highly intelligent, theory-guided) exercises of imagining in order to
come to know what it is like to see red. By imagining red, she was
actually illustrating Jackson’s point, not refuting it. As her example shows,
you can’t know what it’s like before you’ve actually experienced what it’s
like.
An
awkward moment: a simple variation on the tale that clearly refutes it or
clearly vindicates it, depending on how you interpret what happened. If B is
the only conclusion Jackson intended, then we philosophers have been wasting a
lot of time and energy on what appears to be a relatively trivial definitional
issue: nothing is going to be allowed to count as a state of knowing
what it’s like to see red without also counting as an experience of red.
Before looking more closely at this
contretemps, let’s consider one other variation , one I would have thought was
the obvious variation for philosophers: Swamp Mary.[7] Suppressing my gag reflex and my
giggle reflex, here she is:
Swamp Mary: Just as standard Mary is about to be released from
prison, still virginal re colors and aching to experience “the additional and
extreme surprise, the unanticipated delight, or the utter amazement that lie in
store for her” (G&H, p82), a bolt of lightning rearranges her brain,
putting it by Cosmic Coincidence into exactly the brain state she was just
about to go into after first seeing a red rose. (She is left otherwise
unharmed of course; this is a thought experiment.) So when, a few seconds
later, she is released, and sees for the first time, a colored thing (that red
rose), she says just what she would say on seeing her second or nth
red rose. “Oh yeah, right, a red rose. Been there, done that.”
Let me try to ensure that the point
of this variation is not lost. I am not discussing the case in which the
bolt of lightning gives Swamp Mary a hallucinatory experience of a red rose.
That is, of course, one more “possibility” but it is not the possibility I am
introducing. I am supposing instead that the bolt of lightning puts Swamp
Mary’s brain into the dispositional state, the competence state, that an
experience of a red rose would have put her brain into had such an
experience (hallucinatory or not) occurred. So, after her Cosmic Accident,
Swamp Mary may think that she’s seen a red rose, experienced red, been
in a token brain state of the type that subserves experiences of red, but she
hasn’t. It’s just as if she had. Maybe
she wrongly remembers or seems to remember (just like Swampman) having
seen a red rose, or maybe, in spite of her lacking any such episodic memories,
her competences are otherwise all as if she had had such episodes in her
past. (After all, you could forget your first color experiences and still have
phenomenal concepts, couldn’t you?) Ex hypothesi she didn’t have any
such experiences, whatever she now thinks; any bogus memories of color were
inserted illicitly in her memory box by the lightning bolt. Hey, [surely] it’s logically possible.
Swamp Mary is exactly like Mary, an atom-for-atom duplicate of Mary at every
moment of her life except for a brief interlude of lightning that performs the
accidental (but not supernatural) feat of doing in a flash exactly what Mary’s
looking at the rose would do by more normal causal routes. It follows that
those who think “that there are certain concepts that . . . . can only be
possessed and deployed on the basis of having undergone the relevant conscious
experiences oneself” (G&H, speaking of Tye, p65) may be right as a matter
of contingent fact, but it is logically possible for one to acquire this
enviable ability by accidental means). (These
words stick in my throat, but I’m playing the game as best I can.)
3. RoboMary
We now have two routes to Mary’s
post-release knowingness: the Approved Path of “undergoing the relevant
conscious experiences oneself” and the logically possible Cosmic Accident Path.
The second path is a throw-away, not worth discussing. What is worth
discussing is a third route to this summit: not a pseudo-miracle but an ascent
by good hard work: Mary puts all her scientific knowledge of color to use and figures
out exactly what it is like to see red (and green, and blue) and hence is
not the least bit surprised when she sees her first rose. This third path is
hard to imagine, certainly, and as we have just seen, its difficulty is
complicated by the threat of a retreat into circularity. It is high time to
make the task easier, mounting a positive account that just might convince a few
philosophers that they really can imagine it after all. I’m here to help. I
will begin with a deliberately simple-minded version, for clarity, and
gradually add the complications that the disbelievers insist on. In the spirit
of cooperative reverse-engineering, I’m numbering the knobs on my intuition
pump, and adding comments on how the knob settings agree or differ from other
models of the basic intuition pump
1.RoboMary is a standard
Mark 19 robot, except that she was brought on line without color vision;
her video cameras are black and white, but everything else in her hardware is
equipped for color vision, which is standard in the Mark 19.
Hold
everything. Before turning to the interesting bits, I must consider what many
will view as a pressing objection:
Robots don’t have color experiences! Robots don’t have qualia. This
scenario isn’t remotely on the same topic as the story of Mary the color
scientist.
I
suspect that many will want to endorse this objection, but they really must
restrain themselves, on pain of begging the question most blatantly.
Contemporary materialism–at least in my version of it–cheerfully endorses the
assertion that we are robots of a sort–made of robots made of robots.
Thinking in terms of robots is a useful exercise, since it removes the excuse
that we don’t yet know enough about brains to say just what is going on
that might be relevant, permitting a sort of woolly romanticism about the
mysterious powers of brains to cloud our judgment. If materialism is true, it
should be possible (“in principle!”) to build a material thing–call it a robot
brain–that does what a brain does, and hence instantiates the same theory of
experience that we do. Those who rule out my scenario as irrelevant from the
outset are not arguing for the falsity of materialism; they are assuming it,
and just illustrating that assumption in their version of the Mary story. That might be interesting as social
anthropology, but is unlikely to shed any light on the science of
consciousness.[8]
Back to knob 1. Just like Mary, RoboMary’s internal equipment is
‘normal’ for color vision but she is being peripherally prevented–from
birth–from getting the appropriate input. RoboMary’s black-and-white cameras
stand in nicely for the isolation of human Mary, and we can let her wander at
will through the psychophysics and neuroscience journals reading with her
black-and-white-camera eyes.
2. While waiting for a pair of color cameras to replace
her black-and-white cameras, RoboMary learns everything she can about the color
vision of Mark19s. She even brings colored objects into her prison cell along
with normally color-sighted Mark 19s and compares their responses–internal and
external–to hers.
This was
something that Mary could do, of course, only somewhat more tediously–she had
to watch black and white TV while conducting all the experiments she needed to
get that admirably complete compendium of physical information. This suggests a
modest improvement that could be made in Jackson’s original experiment, in which
Mary’s eyes are declared normal, and the entire color-blockade has to be
accomplished with prison walls, confiscation of mirrors, white gloves, etc. As
various commentators have observed, such a world would still be an ample source
of chromatic input–shadows, and the like, not to mention the different shades
of “white”. It would have been a lot
cleaner for Jackson’s original telling if he had stipulated that Mary had a
pair of camcorders with black-and-white eyepieces strapped over her eyes,
peering at the world all her life like somebody videotaping her vacation in
Europe. (Or, slightly more science-fictionally,
he might have imagined Mary not imprisoned but with “filters” implanted
on her optic nerves, permitting only black-and-white signals through.)
3. She learns all about the million-shade color-coding
system that is shared by all Mark19s.
We don’t
know that human beings share the same color-coding system. Probably they don’t,
but this is just a complication we can leave out; if Mary knows everything,
she knows all the variations of human color-coding, including her own.
4. Using her vast knowledge, she writes some code that
enables her to colorize the input from her black and white cameras (à la Ted
Turner’s cable network) according to voluminous data she gathers about what
colors things in the world are, and how Mark19s normally encode these. So now
when she looks with her black-and-white cameras at a ripe banana, she can first
see it in black and white, as pale gray, and then imagine it as yellow (or any
other color) by just engaging her colorizing prosthesis, which can swiftly look
up the standard ripe-banana color-number-profile and digitally insert it in
each frame in all the right pixels. After a while, she decides to leave the
prosthesis turned on all the time, automatically imagining the colors of things
as they come into focus in her black and white camera eyes.
Isn’t this simply the robot version of phosphenes
and trans-cranial magnetic stimulation–forbidden ways of getting color experience
into RoboMary? Or is it rather a way of dramatizing the immense knowledge of
color “physiology” that RoboMary, like Mary, enjoys? What is either of them
allowed to do with their knowledge? Is
this a cheat or isn’t it?
Let’s
turn the knob both ways, and see what happens. In the first, and simplest,
setting, we declare that just as Mary is entitled to use her imagination in any
way she likes in her efforts to come up with an anticipation of what it’s going
to be like to see colors, RoboMary is
entitled to use her imagination, and that is just what she is doing–after all,
no hardware additions are involved: she is just considering, by stipulation,
what it might be like to see color under various conditions. (We can suppose
she goes to the trouble of considering dozens of variant colorization codings,
so she has entertained many different hypotheses about what it is like to see
red, etc., and settled, defeasibly, on the one she thinks is best.)
5. She wonders if the ersatz coloring scheme she’s installed
in herself is high fidelity. So during
her research and development phase, she checks the numbers in her registers
(the registers that transiently store the information about the colors of the
things in front of her cameras) with the numbers in the same registers of other
Mark 19s looking at the same objects
with their color camera eyes, and makes adjustments when necessary, gradually
building up a good version of normal Mark 19 color vision.
In the
case of RoboMary it is obvious what sorts of use she can make of her knowledge
about color and color vision in Mark 19s. It is far from obvious, of course,
how human Mary could make use of her knowledge. But that just shows how
treacherous the original intuition pump is; it discourages us from even trying
to imagine the task facing Mary if she wants to figure out what it is like to
see red.
6. The big day arrives. When she finally gets her color
cameras installed, and disables her colorizing software, and opens her eyes,
she notices . . . . nothing. In fact, she has to check to make sure she has the
color cameras installed. She has learned nothing. She already knew exactly what
it would be like for her to see colors just the way other Mark 19s do.
4.
Locked RoboMary
Too easy! Now let’s turn the knob
and consider the way RoboMary must proceed if she is prohibited from tampering
with her color-experience registers. I don’t know how Mary could be crisply
rendered incapable of using her knowledge to put her own brain into the
relevant imaginative and experiential states, but I can easily describe the
software that will prevent RoboMary from doing it. In order to prevent this
sort of self-stimulation skullduggery (if that is what it is), we arrange for
RoboMary’s color-vision system–the array of registers that transiently hold the
codes for each pixel in Mary’s visual field, whether seen or imagined–to be
restricted to gray-scale values. This is simple: We arrange to code the
gray-scale values (white through many shades of gray to black) with numbers
below a thousand, let’s say, and simply filter out (by subtraction) any values
for chromatic shades in the million-shade subjective spectrum of Mark 19s–and
we put unbreakable security on this sub-routine. Try as she might, RoboMary
can’t jigger her “brain” into any of the states of normal Mark 19 color vision or
imagination. She has all her hard-won knowledge of that system of color
vision, but she can’t use it to adjust her own hardware so that it matches that
of her conspecifics. Her color-representing hardware is disabled.
This doesn’t faze her for a minute,
however. Using a few terabytes of spare (undedicated) RAM, she builds a model
of herself and from the outside, just as she would if she were
building a model of some other being’s color vision, she figures out just
how she would react in every possible color situation.
I find that people have trouble
imagining just how intimate and extensive this “third-person” knowledge would
be, so let’s indulge in a few illustrative details, to help furnish our imaginations.
She obtains a ripe tomato and plunks it down in front of her
black-and-white-cameras, obtaining some middling gray-scale values, which lead
her into a variety of sequel states. She automatically does the usual “shape
from shading” algorithm, obtaining normal convictions about the bulginess and
so forth, and visually guided palpation gives her lots of convictions about its
softness. She consults an encyclopedia about the normal color range of
tomatoes, and she knows that these gray-scales in these lighting conditions are
consistent with redness, but of course nothing comes to her directly about
color, since she has black-and-white cameras, and moreover, she can’t use her
book-learning to adjust these values, since her color system is locked. So, as advertised, she can’t put herself directly into the red-tomato-experiencing
state. She looks at the (gray-appearing) tomato and reacts however she does,
resulting in, say, thousands of temporary settings of her cognitive machinery.
Call that voluminous state of her total response to the locked
gray-tomato-viewing state A. This is a state of her knowing what it is
like for her to see a gray tomato. Then she compares state A with the state
that her model of herself goes into. Her model isn’t locked; it readily goes
into the state that any normal Mark 19 would go into when seeing a red tomato.
And, since this is her model of herself, it then goes into state B, the
state she would have gone into if her color system hadn’t been locked. RoboMary notes all the differences between
state A, the state she was thrown into by her locked color system, and state B,
the state she would have been thrown into had her color system not been locked,
and–being such a clever, indefatigable and nearly omniscient being–makes all
the necessary adjustments and puts herself into state B. State B is, by definition, not an
illicit state of color-experience; it is the state that such an illicit state
of color-experience normally causes (in a being just exactly like her). But now
she can know just what it is like for her to see a red tomato, because she has
managed to put herself into just such a dispositional state–this is of course
the hard-work analog of the miraculous feat wrought by the Cosmic Accident of
the lightning bolt in the case of Swamp Mary.
Her epistemic situation when she has
completed this Vast (Dennett, 1995, p109) but not infinite labor is
indistinguishable from her epistemic situation in the case in which we allowed
her to colorize her actual input–and it had been conceded that in that
epistemic situation she had known what it is like to see red, but the case was
thrown out for cheating. So there are no surprises for her when her color
system is unlocked and she’s given color cameras. In fact, when she completes her
model of herself, down to the very last detail, she can arrange for it to take
over for her locked onboard color system, a spare color system she can use much
as Dennett used his spare computer brain in “Where am I?” (in Dennett, 1978).
Remember: RoboMary knows all the physical facts, and that’s a lot.
Objection: RoboMary can’t put
herself into state B, the state her model is driven into by its unlocked color
system, because that state involves the wielding of what Tye calls “phenomenal
concepts” and these are strictly parasitic on actual phenomenal experiences,
which they quote or reproduce, in effect, when they are exploited in such
demonstrative thoughts as “that is what red looks like.” Part of having
the competence that comes (normally) from experience is being able later to use
demonstratives with internal referents of this sort.
Oh really? Why can’t RoboMary form
demonstratives that allude to the relevant states of her model, instead of her
own locked color system? And why wouldn’t they be just as good? Because they
wouldn’t have that extra je ne sais quoi? But that is just what has not been shown to
exist. In the case of RoboMary the temptation to posit a rather magical extra
property that adheres somehow to her entering into these color-system states
(which are basically just numbers in registers, after all) is weak. The
temptation should be resisted in the case of Mary, too. It has no legitimate
business to do, and tends to distort the imagination covertly.
Objection (thanks to the editors of
this volume): For RoboMary to self-program herself into state B is cheating
just as much as for her to self-program herself into the “experiencing red”
state. What matters is whether Mary (or RoboMary) can deduce what it’s
like to see red from her complete physical knowledge, not whether one could use
one’s physical knowledge in some way or other to acquire knowledge of what it’s
like to see in color.
I just don’t see that this is what
matters. So far as I can see, this objection presupposes an improbable and
extravagant distinction between (pure?) deduction and other varieties of
knowledgeable self-enlightenment. I didn’t describe RoboMary as
“self-programming” herself; I said she “notes all the differences between state
A, the state she was thrown into by her locked color system, and state B, the
state she would have been thrown into had her color system not been locked,
and–being such a clever, indefatigable and nearly omniscient being–makes all
the necessary adjustments and puts herself into state B.” If I use my knowledge to imagine myself into
your epistemic shoes in some regard, is this “self-programming”? And if so,
what is the import of this characterization for the knowledge argument?
Consider Rosemary, another of Mary’s daughters, who is entirely normal and free
to move around the colored world, and is otherwise her mother’s equal in
physical knowledge of color. Rosemary
has a hard time imagining her mother’s epistemic predicament. What must it be
like, she wonders, not yet to know what it is like to see red? She is burdened, it seems, with too much
knowledge (cf. my example of the newly discovered Bach Cantata in Consciousness
Explained, 1991, p388). This is,
presumably, a psychological impediment to her imagination, but not an
epistemological lack.
I take the example of RoboMary to
shift the burden of proof. Thin materialism, the view that Mary, in her well
nigh unimaginable circumstances, would not be surprised after all, has a lot to
be said for it. Enough, surely, to undermine the blithe confidence with which
philosophers have presumed otherwise.
A closing observation: I find that
some philosophers think that my whole approach to qualia is not playing fair. I
don’t respect the standard rules of philosophical thought experiments. “But
Dan, your view is so counterintuitive!” No kidding. That’s the whole
point. Of course it is counterintuitive. Nowhere is it written that the true
materialist theory of consciousness should be blandly intuitive. I have all
along insisted that it may be very counterintuitive. That’s the trouble
with “pure” philosophical method here. It has no resources for developing, or
even taking seriously, counterintuitive theories, but since it is a very good
bet that the true materialist theory of consciousness will be highly
counterintuitive (like the Copernican theory--at least at first), this means
that “pure” philosophy must just concede impotence and retreat into
conservative conceptual anthropology until the advance of science puts it out
of its misery. Philosophers have a choice: they can play games with folk
concepts (ordinary language philosophy lives on, as a kind of aprioristic
social anthropology) or they can take seriously the claim that some of these
folk concepts are illusion-generators. The way to take that prospect seriously
is to consider theories that propose revisions to those concepts.
References:
Dennett,
Daniel, 1978, Brainstorms: Philosophical Essays on Mind and Psychology,
Cambridge, MA: MIT Press/A Bradford Book.
Dennett, Daniel, 1991, Consciousness Explained,
Boston: Little Brown.
Dennett,
Daniel, 1994, “Get Real,” reply to my critics in Philosophical Topics, 22, pp. 505‑568
Dennett, Daniel, 1995, Darwin’s Dangerous Idea,
New York: Simon & Schuster.
Dennett,
Daniel, 1996, “Cow‑sharks, Magnets, and Swampman,” in Mind &
Language, vol. 11, no. 1, pp. 76‑77.
Graham,
George, and Terence Horgan, 2000, “Mary Mary Quite Contrary,” Philosophical
Studies, 99, pp59-87.
Hofstadter,
Lycan, William, 1996, Consciousness and Experience,
Cambridge, MA: MIT Press.
Lycan,
William, forthcoming, “Perspectival Representation and the Knowledge Argument,”
in Q. Smith and A.Jokic (eds.), Consciousness: New Philosophical Essays, Oxford
U.P.
McConnell,
Jeff, 1994, “In Defense of the Knowledge Argument,” Philosophical Topics,
22, pp157-897.
Robinson,
Howard, 1993, “Dennett on the Knowledge Argument,” Analysis, 53,
pp174-77,
Tye,
Michael, 1995, Ten Problems of Consciousness, Cambridge, MA: MIT Press.
[1]I am grateful to Diana Raffman, Bill Lycan, Victoria McGeer and my
students for many discussions, on email and in person, on the ins and outs of
this argument.
[2]For instance, Howard Robinson (1993) supposes
that I am illicitly helping myself to the premise that Mary knows “every
particular physical thing that is going on” (p175), but my claim does not at
all depend on such a strong claim, as will be clear from the variations I
develop here.
[3]Robinson (1993) also claims that I beg the
question by not honoring a distinction he declares to exist between knowing “what
one would say and how one would react” and knowing “what it is like.” If there is such a distinction, it has not
yet been articulated and defended, by Robinson or anybody else, so far as I
know. If Mary knows everything
about what she would say and how she would react, it is far from clear that she
wouldn’t know what it would be like.
[4]Earlier Tye had noted simply that “possessing
the phenomenal concept red requires that one have experienced red . . .
. possession consists (very roughly) in
having available a state that has a causal history that links it with the
relevant experiences . . . . ” (p167)
[5]Lycan’s second alternative is a startling
concession, unremarked upon. If one can be told, why can Mary not simply be
told, by standard color-enjoyers psychologically very similar to her? I don't
think Nagel allows this, and if Lycan does, the game is over. Thin materialism
wins. In the context, Lycan is imagining the variation in which Mary is born
colorblind, which explains the lapse: those who could tell her are not
‘psychologically very similar’ to her.
[6]I find that this example nicely focusses the
attention of students. I show my students a display that contains three
brightly-colored and unlabeled disks of red, green and blue: “Are you claiming
that Mary could not tell, on first seeing this display, which disk was
red?” They are inclined to insist that she could not, but what would they make
of it, I then ask, if she could do it? Would it have to be “magic” or
“cheating” or could it just possibly be the result of good hard work on her
part? They then see that the impossibility claim is in fact much more dubious
than
[7]Gabriel Love suggested this hybrid to me, and
I think he was inspired by considering another: In “The Trouble With Mary,”
Victoria McGeer (forthcoming) has written persuasively and elegantly on what
happens when you hybridize Mary and zombies. I have expressed my distrust of
all such thought experiments in Dennett (1994); excerpted (with revisions) in
Dennett, (1996).
[8]It has been drawn to my attention by the editors that a “type-identity
theorist who believes conscious experiences are essentially neural” could balk
at my robot scenario, on grounds that it was impossible. Officially, I suppose,
such a theorist counts as a materialist, and so would a theorist who views
blood-pumping as “essentially cardial” and declares artificial hearts to be
impossible, but nobody has yet offered a remotely plausible reason for
believing any such doctrine. Such mysterian or vitalistic versions of materialism
deserve to be ignored until someone has made a positive case for them.