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The knowledge argument (also known as Mary's room or Mary the super-scientist) is a philosophical thought experiment proposed by Frank Jackson in his article "Epiphenomenal Qualia" (1982) and extended in "What Mary Didn't Know" (1986). The experiment is intended to argue against physicalism — the view that the universe, including all that is mental, is entirely physical.

The thought experiment was originally proposed by Frank Jackson as follows:

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 specializes 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 wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. [...] What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?

Jackson sugguests that Mary, the omniscient scientist who knows all there is to know about the physical world, will learn something new after she leaves the black and white room. This is evidence for qualia, he says, and thus strong physicalism is false.

So, it seems like Jackson is denying that experience, or even "knowledge-how" can be explained physically.

But let's say that Mary--being the super scientist that she is--has borderline godlike powers: she knows supreme realities beyond our wildest dreams. In that case, if you assume that experience is physical, she would be able to simulate the correct chemicals and processes in the brain as to actually experience (albeit hallucinate, without a real stimulus) the color red. By "simulate" here I mean to duplicate the biophysical processes in her brain that result in the perception of color. In such a case, Jackson's argument would be wrong.

Is my interpretation of Jackson's argument wrong, or does it really not stand if we simply add to Mary's power as I describe? Why is it considered a persuasive argument to some people?

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  • If Mary leaves her 'room' and she knows all there is about the physical world what if she wanders into an Art Gallery . She will encounter various paintings in some order. Anyone who sees a painting will interpret it in certain ways dependent on the person's present 'cognitive' and emotional development . No two people see a painting in exactly the same ways. So Mary will see these paintings and for each one have cognitive and emotional experiences that would be 'hard' to predict even with knowing 'all there is about the physical world'. She will learn something new about how she reacts.
    – user128932
    Oct 19, 2014 at 5:50
  • So subjectivity exists, but I don't see how this disproves phyiscalism--since you can have physicalism and subjectivity at the same time without them being contradictory to one another. Oct 19, 2014 at 5:55
  • Is physicalism the idea every possible phenomenon is only about physical structures and how they interact? Subjectivity doesn't disprove physicalism but it shows a novel 'sequence' or set of ideas like a real configuration of patterns in a computer system ( if Mary was an android) could be considered a real set of 'qualia'; if qualia could 'represent' a respective set of patterns in the computer memory or a configuration of patterns in 'remembered' neuronal activation patterns.( if these are the right terms)So why couldn't qualia be considered a 'real' 4-dimensional phenomenon?
    – user128932
    Oct 19, 2014 at 6:08
  • Thanks for the followup! Are you saying that subjectivity (i.e. a unique set of patterns/ideas) can be represented/explained by either qualia or physicalism? Oct 19, 2014 at 6:17
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    @DaveB - There are visual illusions that create the sensation of color from black and white stimuli. For instance, newscientist.com/blogs/nstv/2011/09/…
    – Rex Kerr
    Oct 21, 2014 at 9:18

6 Answers 6

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Mary's room is persuasive to people who don't know the difference between declarative knowledge and other kinds.

If the super-scientist Mary studies but does not play tennis, and then you finally give her a tennis racket, guess what? She will not be competitive with top tennis players, since sports involve a large amount of procedural knowledge. This doesn't mean that "motor memory" isn't physical, or that muscles aren't physical. It just shows that not all knowledge is declarative. It doesn't even mean that Mary is missing something essential from her scientific hypotheses, just that her knowledge isn't in the right form for her to effectively swing a racket.

Anyway, it's a silly argument. It doesn't have the right form to show anything useful. We shouldn't waste any more time with it.

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Jackson does not claim that for Mary "the entirety of physical knowledge is a priori", but rather that Mary is "forced to investigate the world from a black and white room".

Here is how Jackson describes Mary:

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."

You wrote:

if you assume that experience is physical, she would be able to simulate the correct chemicals and processes in the brain as to actually experience (albeit hallucinate, without a real stimulus) the color red.

there is no doubt that you can produce an experience, but can you completely describe it as physical (mathematical?) knowledge?

so if by simulate you meant stimulate (her own brain) then she might experience color, but that misses the point.

on the other hand, if by simulate you meant by using a pen and paper, or a computer, then the question remains who will "actually experience"; is it Mary?

I think the idea is a qualitative distinction between a physical (mathematical?) description of neurophysiological processes in the brain, and the correlated subjective (fire breathing) experience which some people (not everybody) stubbornly insist they are having.

You can find the original paper here - http://philosophyfaculty.ucsd.edu/faculty/rarneson/Courses/FrankJacksonphil1.pdf

There is a also a later, somewhat different version from 1986.

and a discussion in SEP - http://plato.stanford.edu/entries/qualia-knowledge/

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  • Thanks for the reply! So there is a distinction between physical propositional knowledge and subjective knowledge, and Jackson argues that the existence of subjective knowledge is enough to disprove physicalism. What is it about subjectivity that is a problem for physicalism? Is it too far of a stretch to acknowledge that it's possible for subjective experience to be the result of physical interaction between the brain, body, and environment? Oct 19, 2014 at 6:05
  • there is another distinction, between physicalism and believing qualia arises as a natural phenomena in the brain; these are entirely different things! there are vaious kinds of non-physicalists, but some of them (like myself) believe that qualia is a natural phenomena produced by the brain by some process that we do not understand; I recommend that you dive into the links, if you are interested in the subject.
    – nir
    Oct 19, 2014 at 7:22
  • @nir Qualia as defined can not be produced by any physical process whether we understand it or not. There might be a process in the brain that runs parallel to experiencing of qualia, but that process is not qualia even if it provides complete relational knowledge of them. Isn't that the point of Mary's room?
    – Conifold
    Oct 20, 2014 at 20:21
  • @Conifold, I said it is a natural phenomena which is produced in the brain, which is a different thing, since the world is not a physical process; physics is just our partial and approximate description of it.
    – nir
    Oct 20, 2014 at 20:28
  • @nir Then what exactly is the meaning of "natural" as opposed to ideal or mental?
    – Conifold
    Oct 20, 2014 at 20:48
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So, it seems like Jackson is denying that experience, or even "knowledge-how" can be explained physically.

Perhaps there is a "map is not the territory" fallacy at play here. That experience can be explained physically does not make the explanation the equivalent of the experience.

I would agree, however, that given a sufficient explanation of an experience in neurophysical terms, it may be plausible to replicate the experience:

In that case, if you assume that experience is physical, she would be able to simulate the correct chemicals and processes in the brain as to actually experience (albeit hallucinate, without a real stimulus) the color red.

But, as others have pointed out, this is the equivalent of Mary actually going to the art gallery. In order to have this new knowledge of an experience, Mary must first have it -- whether this is via an art gallery trip or the simulation of same does not make any difference to the argument, namely that complete knowledge of the explanation of how an experience works is not the same as knowledge of the experience itself.

However, this does not seem like a strong objection to physicalism, only epistemological hair splitting.

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I can see the power behind the argument because to get around it a person would either have to stretch the imagination into areas that might seem implausible or have to solve a lot of academic problems, if the person is to be satisfied that Mary has all the facts and that all the facts are physical facts.

Foregoing the route of solving a lot of academic problems for now, I think we can continue to think about Mary in a way that derives directly from your formulation, RECURSIVE FARTS.

The original Mary is characterized with the standard scientific kind, as having descriptive knowledge. If it's implied that she has procedural knowledge, which standardly tends to be an engineering kind, it's not very much.

In domains where descriptive knowledge is enough, interfacing with things around you tends to be enough. You don't need to begin an approach to knowing the inner workings of things to the extent of knowing how to reconstruct them or something like them. That is, you don't need to begin an approach that's pointed to knowing things in themselves. At most, you'd need to know enough to create simulations, which, while a lot of times very sophisticated, is not the same.

But descriptive knowledge isn't always enough in all domains where physical knowledge is required. Additional knowledge is required to assemble basic components (which are usually for larger systems).

Without getting into whether or not Mary has the "right kind" of knowledge about colors, we can already say she lacks some physical knowledge. That is, she doesn't know how to assemble basic components. Or, at least, she doesn't have the facilities to assemble basic components and gain the knowledge of herself going through the process of assembling the basic components. Indeed, this would be just like you said, this would be a posteriori knowledge, RECURSIVE FARTS().

Now that we may begin to question the sobriety of the original caricature of Mary, we may be able to close in on settling the issue.

Even letting alone the question of the life-changing subjective quality of strolling through the wilderness, we know that as it stands Mary neither has enough knowledge ab intra nor has enough knowledge a fortiori. However, provided proper education and further facilities, whether industrial or surgically integrated with her body, she would simply demonstrate her sufficiently complete knowledge of the physical world.

First she would make basic nanoconstructors. Then she would make physical replicas of everyday inanimate objects. Then she would make physical replicas of archaea. (...) And finally, for now, she would give you a neural implant to complement hers for bidirectional communication of art works and anything else that could be seen in virtual reality. Of course, the tests she had to perform to get such magic right must've involved having knowledge of the physical world to such a degree that it went much beyond descriptive knowledge, and into its superset of acquaintance knowledge.

Having physical descriptive knowledge is simply not the only kind of physical knowledge to have.

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  • I recommend you edit RECURSIVE FARTS into @RECURSIVE_FARTS or something else entirely so folks don't get the wrong impression that you are using foul language.
    – nir
    Oct 19, 2014 at 7:07
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Very quickly I felt this thought experiment was flawed.

Displaying the world through a Black and White TV is still requires either an analog or digital conversion process when recording or converting the recorded colors to gray-scale. In this conversion, information is lost. With that loss of information, there are going to be shades of gray that can't be assigned a 1:1 definition as the color(s) Mary perceives. There will be a shade of grey that could be represent multiple combinations of color. The facts presented to Mary about wavelengths would include explanations of variations (shades) of colors as light frequencies change and explanations of how to reproduce color using RGB, CMYK, etc....

I believe the BRILLIANT Mary would be able to observe and that certain grey-scale shades were used to represent multiple colors as described to her in referential words. She would then deduce or hypothesize that she was missing some necessary contextual information to link what she has learned to what she observes. I believe she would either accept that her knowledge was either incomplete or unable to be tested/empirically proven by generating light waves, or she would be seeking the missing piece of knowledge/experience.

When she opened the door to the world of color, I believe she would see it as potentially answering the suspicions she already had.

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We do not need to hypothesise. In 2009 Catherine Mancuso from the University of Washington gave functional full colour vision to adult squirrel monkeys using gene therapy. Squirrel monkeys are a New World species with no history of three colour vision. Nevertheless, their brains, and our brains have enough neuroplasticity to adapt to the new stimuli. They did not immediately see the new colours, but they could see shades between red and green, and they learned to pick out the patch with the non-matching hue for rewards.

Rewards? Squirrel monkeys like apple juice.

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