Swamp Thing About Mary

On Friday I attended Pete Mandik’s Cogsci talk at CUNY. The talk was excellent; entertaining and with a spirited discussion of many interesting topics. This paper represents one of a two part project that Pete is pursuing that involves Swamp Mary. One project employs Swamp Mary against dualists while the other employs her in an in-house dispute between what Pete call ‘gappy’ and ‘non-gappy’ physicalism. Friday’s talk was the latter and is based on his paper Swamp Mary Semantics: A Case for Physicalism without Gaps.

Pete’s distinction is recognizable as meant to capture type-a and type-b physicalism. More generally it is the distinction between a priori and a posteriori phsyicalism. Or at least one may get that idea from the way Pete characterizes the distinction. He says that the issue is over whether or not what we can “classic Mary” in her pre-release condition is in a position to know what it is like to see red. Pete claims that the gappy physicalist will deny that she does while the non-gappy physicalist does not. Swamp Mary is then presented as a challenge to the gappy physicalist. In short the challenge goes as follows. Swamp Mary is a physical duplicate of post-release Mary, the one who has seen red and so knows what it is like to see red, but Swamp Mary has never herself seen red since she is a swamp being who, we can stipulate, has had no experiences herself at all. She is a duplicate of a being that has had the experience of seeing red but hasn’t herself had the experience. Nonetheless, Pete urges, it is natural to say that Swamp Mary knows what it is like to see red. This is natural since post-release Mary knows what it is like to see red and Swamp Mary is a physical duplicate of post-release Mary. But since it is also natural to say that Swamp Mary has never seen red, or had an occurrent red quale, it is now mysterious why it is supposed to be the case the pre-release Mary doesn’t know what it is like to see red. If Swamp Mary can know what it is like to see red without ever having a red quale then it ought to be the case that pre-release Mary can also know what it is like to see red without having seen it. Thus, Pete concludes, physicalist should be non-gappy physicalist and hold that Mary can know what it is like to see red in her pre-release state.

Pete then goes through various responses that might be made by the type-b physicalist and tries to show that they all have problems. He does this by examining four different psychosemantic theories, which he also claims to be exhaustive, and arguing that they cannot provide the relevant explanation (i.e. of the difference between pre-release Mary and Swamp Mary’s knowledge of what it is like to see red). The four categories of psychosemantic theory are: 1. Quotation 2. Actual Cause 3. Nomological 4. Descriptive-homomorphic/isomorphic. Briefly, 1 is supposed to capture any kind of self-presentational view about phenomanl concepts like that of Chalmers or perhaps Block. 2 is supposed to capture any kind of teleological or causal theory of content while 3 is supposed to capture anything that resembles Fodor’s psychosemantics (think ‘asymmetric dependance’ here). Finally, 4 is supposed to capture any kind of conceptual role kind of theory. The problems for each of these, to make a long story short, are that 1 and 2 cannot explain how Swamp Mary does know what it is like to see red while 3 & 4 end up having problems explaining why pre-release Mary doesn’t know what it is like to see red.

There is a lot of detail that I am leaving out but in general Pete is trying to construct an argument against a central claim of the type-b physicalist. This is the intuition, shared by many, that one cannot really have the full concept RED without having the red quale present in ones consciousness. Or to put it more common sensically, one cannot know what it is like to see red unless one has (a) had a red experience and (b) has the ability to think, or otherwise identify, that the experience is red while one is having it. Pete has the intuition that Swamp Mary knows what it is like to see red and yet neither (a) nor (b) seem to be met and therefore concludes that the type-b physicalist is wrong. I suggested in discussion that Pete was running over the distinction between ‘knowing what it is like’ in the general sense, and ‘knowing what it is like FOR one’. To know what it is like for one too see red requires that one have, or be able to recall, a red experience and to be able to say, so to speak, to one’s self ‘this is what it is like to see red’. To know what it is like in the generic sense is to know what it is like to see red in the way that pre-release Mary is typically thought of by the type-b physicalist. She can know a lot about what it is like to see red. She can know that it is more like seeing something pink than it is like seeing blue, and all other kinds of facts. But intuitively she doesn’t know what it is like for her to see red. Once we have this distinction in mind we no longer have a problem with Swamp Mary. Swamp Mary knows what it is like in the generic sense, in just the same way as pre-release Mary, but she does no know what it is like for her to have the experience, again just like pre-release Mary. To put this in different terminology, both pre-release Mary and Swamp Mary lack the “pure” phenomenal concept, though they have many others. On the other hand, if we think that Swamp Mary does know what it is like in this way it will be because she has an ability to call up the red experience and identify it, whereas Classic Mary cannot do this.

Finally, does saying this really make one a gappy/type-b phsyicalist? I claim that it doesn’t. I agree that in the way the Mary thought experiment is usually set up we arrive at the conclusion that pre-release Mary cannot know what it is like for he to see red. This is because she lacks the appropriate concept, the pure phenomenal concept. In order to acquire this concept she needs to have the experience. But once she does there is no longer any gap between the physical and phenomenal. Once Mary has the pure phenomenal concept she is able to know what it is like to see red in the complete way necessary to make deductions from physical facts to phenomenal facts without relying on the pure phenomenal concept (or introspection) for justification of any step in the deduction. Thus in order to really count as a gappy physicalist in Pete’s sense we would have to deny that even once Mary had this concept she would be unable to know what it is like for her to see red just on the basis of the physical facts. This is much less plausible to me.

After the talk at the bar we started to talk about the role that intuitions should play in philosophy. This discussion was started by thinking about the experience principle. Why does anyone think that it is true that in order to fully have the concept of red one must have seen red, or had a red experience? I claimed that have prima facie evidence for this claim from the fact that it is intuitively obvious to many philosophers. I agree, basically, with Michael Devitt’s view that intuitions, especially those of experts, should count as defeasible evidence. Thus, we can have a priori justification for believing something but not a priori knowledge in the traditional sense. The mere fact that most philosophers think that Mary couldn’t know what it was like for her to see red from within her room should count as evidence, not for epiphenomenalism or dualism, but rather for the experience principle. That is what is really being tested there. Now, I agree that this is defeasible evidence. We could come to have reason to reject the idea. I *think* I can at least negatively conceive of a situation where pre-release Mary comes to know what it is like to see red without seeing it first. She will know that when people see red they are in a certain brain state. She will also know that people talk about knowing this state in a special first-person way and that they can only do this when in the relevant brain state. She might then conclude that to know what it is like to see red in this sense requires that she be in this brain state. Since she is not allowed to have the stimulus that will produce the brain state she must find some other way to produce the brain state. She might then realize that when one imagines seeing red one goes into something like the brain state that one is in when one actually sees red. Could she come to token this brain state without the stimulus? Well, obviously she could rig some kind of autobrain stimulation to stimulate the area and produce the experience. But is it absurd to think that she could do this without brain stimulation? That is, could she imagine what red looked liked without ever having seen it? I am not sure…my intuitions tend to go with the experience principle but I can’t see anything contradictory about the scenario just described…

There is more to say about all of this but this is getting too long already! 

Cross-posted at Philosophy Sucks! 


  1. Joshua Stern

    Could she come to token this brain state without the stimulus?


    Just about the same way your iPod can token “Smoke on the Water” without having been born in the 1960s.

    Swamp Mary. Ow, my head.

  2. Bill

    quote: “Since she is not allowed to have the stimulus that will produce the brain state she must find some other way to produce the brain state.”


    But there are at least three ways such internal quale production happens in humans all the time: memory, imagination, and dreaming.

    What if knowing what it is like to see red implies the ability to imagine or dream that color in a way that effectively creates that quale? After all, we can dream in color, which implies we can make quales without external stimuli. Normally such a quale would be in someone with the appropriate memories of that kind of quale, but perhaps a truly exact physical duplication of someone with memories of seeing the color red would include the ability to dream or imagine the color red?

    If so, such a duplicate would not know it is was like to see red UNTIL she imagined or dreamed that color– all the physical duplication would give was the immediate ability to do so without a red object in view. Probably just asking Swamp Mary a question about the color red to get her thinking about redness would be enough to trigger that quale, though. Perhaps this straddles the gappy and non-gappy positions above.

  3. Suppose the first thing that happens to Swamp Mary is she sees some blue and correctly thinks *this is not an experience of red*. Is it incoherent that she could do this without having a red quale? If so, I would like to see an explanation of why this would be the case that doesn’t just beg the question of whether pre-release non-Swamp Mary doesn’t know what it’s like to see red.

  4. Joshua Stern

    The idea that Mary (Swamp or Classic) could simply dream a red quale – is excellent! At least it comports with my gross physicalism. At least in theory. In practice (that is real life) we know that some visual experience is needed for the visual cortical system to develop. I am not aware of any real Mary experiments, with Mary the Rat or other subject, that would determine whether in fact such a dream of a never-experienced sensory quale would/could occur. I wonder if such a determination is now or will soon be within experimental range.

  5. Bill

    Presumably swamp Mary she can see and recognized blue just as she would red, and might logically (verbally) deduce from the fact that blue things are blue and not another color that this is not red.

    I suppose that it would be optional whether she would at that moment also do enough nonverbal (visual) thinking about redness to create a red quale.

  6. Bill

    This is actually relevant to my son, who has protanopia (red color blindness). There are some expreimental gene therapies out there in animals, and I think some neuropsychologists and philosophers need to interview any humans who get such a treatment to see what they see (once it’s truly safe, of course).

  7. Joshua Stern

    protanopia …

    Of course, natural “Mary”s! I believe it is known that the condition includes a lack of red/green receptors in the retina, right? I have a fuzzy recollection that I was so informed, umpty years ago in school, which may even have been correct (if my memory is!).

    Do we even have a clue what the relationship of that is to brain factors in the condition? Probably not … but at least, I am not aware of any reports of people with protanopia having dreams of colors they do not see in reality. A datum, if not a resolution.

  8. Bill

    To clarify, what I was saying above is that swamp Mary probably has the ability to dream redness, not that pre-release Mary can. Such is my intuition only, of course :).

    I don’t know of any real life examples of dreaming in colors we cannot otherwise see, but the animal studies on color perception after color blindness is corrected suggest that the brain can see a new color after the appropriate cone cells are fixed, even if development of brain areas for vision was otherwise already complete.

  9. Jonathan Farrell

    I’m interested in your (Richard’s) distinction in the fourth paragraph between (a) ‘knowing what it is like to V’ and (b) ‘knowing what it is like for one to V’. Is the idea that the former amounts only to knowing where V-ing stands in some network of similarity relations (to W-ing, X-ing, etc.)? If so, then it looks as if the ‘like’ in (a) is the ‘like’ of resemblance (the one that means something like ‘similar to’). But this doesn’t seem to be how the ‘like’ in (b) is working. Wouldn’t it be a bit odd if ‘like’ meant different things in (a) and (b)? (Also, it seems that people like, say, Nagel and Lewis explicitly rule out reading ‘like’ in (a) as ‘similar to’.) I haven’t come across this way of intepreting the two phrases before – do you know of any other discussions of it? Or have I misunderstood the distinction?

  10. Richard Brown

    Hi Jonathan, sorry to be so slow in replying to you! Things have been super busy out here in Meat Space!

    My discussion is inspired by the discussion in Rosenthal’s Consciousness and Cognition paper “How Many Kinds of Consciousness?” (available on his website). He there distinguishes between what he calls a “thick” and a “thin” reading of “what it is like”. The thin sense is meant to cover unconscious sensory qualities, ones that we are no way aware of having. These states have phenomenal character in that they differ  from other sensory states in characteristic ways, and in that they play certain characteristic functional roles (that is, perceptual roles). But when these states occur unconsciously they are phenomenal only in this thin sense. When they are conscious there is thick phenomenally and there is something that it is like for the subject. 
    The intuitive idea behind the distinction, for me at least, is that we can know what it is like to be a table in the sense that we can specify in third person terms the complete details that entail the table’s existence. That is all there is to what it is like to be a table. It is boring…simply like a bunch of 1 dimensional strings vibrating…or point-particles, or whatever physics says. But there is nothing that it is like for the table to be a table. This emphasis on there being something that it is like for the subject is something that was emphasized by Nagel himself in his original discussion of this. So, I wouldn’t want to say that it is simply similarity-relational stuff, but is rather all of the stuff that, intuitively, can be known completely from the third-person. It is in this sense that we can know what it is like to be a bat. But we cannot what it is like for us to be a bat without having the relevant experiences. Does this help or did I miss what was bothering you? 
  11. Jonathan Farrell

    Hi Richard.

    What you said dealt with my worry, thanks. I can see the distinction that Rosenthal is drawing, and how it’s relevant to the swamp Mary case.

    (Although I’m not sure that describing the distinction in terms of ‘what it is like’ vs ‘what it is like for’ is helpful (unless Rosenthal is stipulating how we should use these terms). It seems to me that they can both be naturally read in either way. But this is a worry about the way Rosenthal labels the distinction, not about your use of it, so a bit off topic here.)

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