← Home

Mary’s Room

“It seems just obvious” is the whole argument. Its author no longer finds it obvious.

Defendant
Frank Jackson, “Epiphenomenal Qualia” (1982)
Claim
Mary knows every physical fact about colour vision and still learns something when she first sees red. So there are facts physics leaves out, and physicalism is false.
Charge
Stipulating an unimaginable quantity of knowledge, then consulting the imagination about what it contains.
Verdict
Guilty, on the defendant’s own later testimony.

The argument, in his words

Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specialises in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wave-length combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal chords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. — Jackson (1982)
What will happen when Mary is released from her black and white room or is given a colour television monitor? Will she learn anything or not? It seems just obvious that she will learn something about the world and our visual experience of it. But then it is inescapable that her previous knowledge was incomplete. But she had all the physical information. Ergo there is more to have than that, and Physicalism is false. — Jackson (1982)

The extra something he called qualia, and the paper opens: “I am what is sometimes known as a ‘qualia freak’.” The title tells you where it ends up. The qualia are epiphenomenal: they are caused by the brain and cause nothing themselves.

Rebuke 1: everything is a lot

The argument has one premise that does any work: “It seems just obvious that she will learn something.” That is a report of an intuition. So whose situation is the intuition about?

Look at what Mary is said to know. Not the textbook. She knows exactly how light from the sky ends up, by way of the entire central nervous system, moving a larynx. That is the complete dynamics of something like 1011 neurons, her own included, for every colour and every circumstance. Patricia Churchland:

How can I assess what Mary will know and understand if she knows everything there is to know about the brain? Everything is a lot — P. S. Churchland (1986)

Nobody can imagine being Mary. So the reader quietly imagines somebody else, a woman who has read a great many books about colour, and consults their intuition about her. The intuition is correct, about her. It is the move from the Chinese Room: stipulate something astronomical, picture something that fits on a desk, and report what the picture tells you.

Dennett made the point with a story of his own:

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. … 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!” — Dennett (1991)

Dennett’s story does not show that Mary would spot the banana. It shows that nobody knows what she would spot, which is all that is needed. Jackson offered an intuition as a premise, and the intuition is about the wrong woman.

On “it seems just obvious”, Dennett again, in dialogue with a traditionalist:

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? — Dennett (2007)

Rebuke 2: knowing about a state is not being in it

Grant that Mary’s jaw drops. Something new has certainly happened: her visual cortex is in a state it has never been in. The argument needs more than that. It needs the new thing to be a fact that physics omits.

Just as the obstetrician does not become pregnant by knowing all about pregnancy, so Mary does not have the sensation of redness by knowing all about the neurophysiology of perceiving and experiencing red. — P. S. Churchland (1986)

Knowing everything about a hurricane does not make your study windy. Nobody concludes that wind is non-physical. A complete description of a state and an instance of that state are different things, whatever the state is made of.

Philosophers have two ways of spelling this out. David Lewis and Laurence Nemirow say Mary gains abilities and no new fact: she can now recognise, imagine and remember red. Others say she meets an old fact under a new description, the way you can know that Clark Kent is in the building and still be surprised to hear that Superman is. Both replies have critics. Either one blocks the inference, and the argument has to defeat both.

Rebuke 3: it works just as well against ghosts

Suppose physicalism is false and colour experience involves some non-physical ingredient. Give Mary black-and-white lectures on that too. David Lewis:

Black-and-white Mary may study all the parapsychology as well as all the psychophysics of color vision, but she still won’t know what it’s like. Lessons on the aura of Vegemite will do no more for us than lessons on its chemical composition. — Lewis (1988)

So the thought experiment has nothing in particular to do with physics. No course of lessons, on any subject matter, puts you in the state of seeing red. The gap between complete description and first acquaintance opens whatever the descriptions are about, and a gap you would expect under physicalism and under its rivals alike is not by itself evidence against physicalism.

Rebuke 4: the conclusion can’t explain why anyone believes it

Jackson accepted where the argument leads. On his own epiphenomenalist account the quale does nothing; more generally, causal closure gives that result once systematic overdetermination is ruled out. He defended the position, while admitting it is hard to give qualia a causal role “without sounding like someone who believes in fairies.”

Now ask what causes Mary to say “So this is what it’s like”. Speech is air moved by muscle. On Jackson’s view the quale cannot have moved it. She would have said the same words without it. Lewis drew the obvious further consequence:

Afterward she does things she couldn’t do before, such as recognizing a new sample of the first color she ever saw. She may also do other things she didn’t do before: unfortunate things, like writing about phenomenal information and the poverty of materialism. — Lewis (1988)

“Epiphenomenal Qualia” is a physical object, produced by a physical hand. If its conclusion is true, qualia played no part in its being written.

Jackson’s response

He agreed. It took a while, but he agreed, and that last problem is what did it. His 1995 postscript argues that if qualia are epiphenomenal then knowledge of them is impossible, so something in the knowledge argument has to be wrong.

Most contemporary philosophers given a choice between going with science and going with intuitions, go with science. Although I once dissented from the majority, I have capitulated and now see the interesting issue as being where the arguments from the intuitions against physicalism—the arguments that seem so compelling—go wrong. — Jackson (2003)
In ‘Epiphenomenal Qualia’ I explain why it’s not such a disaster being an epiphenomenalist, but I came to think of this as a triumph of philosophical ingenuity over common sense. This is what someone who’s done a good philosophy degree can somehow make seem all right, but if you look at it in a more commonsensical way it’s actually pretty implausible. — Jackson, interviewed by James Garvey (2011)

He also explained how the paper came about. The psychology department at Monash, he says, “sort of said we understand that you’re one of the few dualists left on the planet. Would you like to give a talk saying why?”

Make a mistake in philosophy and the world has to hear about it endlessly. The author left the room years ago. Mary is still in there, on every syllabus.

Scope

None of this shows that physicalism is true, or that there is nothing puzzling about experience. It shows that this thought experiment does not settle the question.

The argument still has able defenders who think Jackson was right the first time. Their case has to be made without “it seems just obvious”.

In Jackson’s favour

The argument is stated in two paragraphs, with its premises in plain view. Most of what it is up against cannot say that.

The distinction it trades on is real. Reading about red and seeing red are different, and saying exactly how is harder than it looks.

And he changed his mind in print, named his own error, and was funny about it.

References