Wednesday, June 11, 2014

Escher Colors
Hilary Putnam

Once, not long ago, I took my wife to have a picture taken of the maculae of her eyes, the tiny areas of the retina of greatest visual acuity surrounding the fovea. (The finding was satisfactory.)  As each eye was scanned, the macula filled the technician’s screen, and the technician,who specializes in taking such pictures, told me the magnification was so great that if one showed the whole back of the eye at the same magnification the picture would cover the whole large wall behind the apparatus—perhaps forty feet long! Afterwards, as the technician and I were chatting, I mentioned that most people experience a slight difference in the shades of color they seem to see when they look at something with one eye closed and then, looking from the same spot, look with the other eye closed, and that this is explained by slight normal variation in the pigmentation of the macula themselves.  The technician exclaimed, “I noticed that, and I thought there was some sort of imbalance in my vision.” So the ubiquity of a phenomenon which is easily checked (as my students have verified through the years), is not known to at least one technician who spends his life looking at precisely the maculae of the human eye, even though he experiences it himself! And, apart from Ned Block, who cited me as the source of his information [in “Wittgenstein and Qualia”], and myself,  it seems to be missing in the literature on perception. But it should be better known, because it is only by ignoring it that one can even consider accepting the version of ultra-naïve realism about perception that currently goes by the name of “representationalism” [or some of the more extreme versions of disjunctivism?].
As I explained in the course of a comment on a paper by Ned Block [“Comment on Ned Block” in Baghramian’s Reading Putnam], this phenomenon is one I noticed by chance when was a college student, and, as I just said, many people have verified it since, including (in his own case) the photographer of maculae I mentioned above. As I said in “Comment on Ned Block”:
“I have experienced it [that colors ‘look different’ to the right eye and to the left eye] in my own case. And it also doesn’t really depend on the names we have for the various colors and shades of colors. First of all, the difference isn’t so great that with one eye closed I would say “It’s a grey wall” and with the other eye closed I would say “It’s a white wall”. In the case of my experience when looking at a beach in bright sunlight, what I might have said is that the beach seemed to be slightly different shades of yellow, depending on which eye was open.  But I wouldn’t say that it seemed to be yellow when viewed through my left eye alone, and gray when viewed through my right eye alone. The difference was not that extreme. And it wouldn’t have affected my “matching” performance on a color chart. No matter which eye is shut, if the beach matches yellow32 with the left eye shut, it will match yellow32 with the right eye shut. And by the way, our notion of “exactly the same color,” has itself been affected by and refined by technology especially by mass production and the resultant need for standardization.
My own experience thus prepared me to accept one of the points that Block makes: the view (common to ‘representationalists’ and at least some ‘disjunctivists’ in the philosophy of perception) that the phenomenal quality of a subject’s visual experience upon looking at (hearing, feeling, smelling, etc) a certain portion of her environment is exhausted by the objective appearance-properties (e.g., looking such-and-such a shade from such-and-such a point in space under such-and-such lighting conditions) of that portion of the environment is untenable. This view is, of course, a strong form of ‘naïve realism’, and while I think naïve realists are right to say that what we see (hear, feel, smell, etc.) when we perceive objects and events in our environment are properties of those objects and not properties of our qualia (something Block also thinks is right, as his paper makes clear), it is a mistake to say that describing what we perceive in objective terms also completely describes the phenomenology of the perceptual experience. That phenomenology is determined by a combination of objective and subjective factors, and representationalists err by failing to recognize the contribution of the subjective side. On all this Block and I are in agreement.”
What I want to do in this little post is go further into the implications of this fact.
One of those implications was very well brought  our by Block [in “Wittgenstein and Qualia”, the paper I commented on].  Given that the phenomenon is ubiquitous (I had no way of knowing in advance that the technician I mentioned it to had noted it in his own case, but this agrees perfectly with the testimony of my students over the last ten years, since I have been mentioning it in lectures), it would be crazy to say that the explanation is that my right eye is “normal” and my left eye is “abnormal”, or vice versa. Nor is there any reason to suppose that my color-qualia are exactly the same when I look at the gray wall from a certain place using my right eye (i.e., with my left eye closed) as your color qualia when you look at the wall from the same viewpoint using either your right eye or your left eye. There is no reasonable notion of a “normal” macular pigmentation such that all persons with a normal macular pigmentation enjoy the same phenomenal color experience when they look at things with a given objective color.

Of course, the representationalist (or an extreme disjunctivist?) can claim that there are no such things as color qualia, and a fortiori no such meaningful question as whether my color qualia (with or without one eye closed) are the “same” as someone else's; but the question whether the phenomenal character of my own color experience when I use my right eye and when I immediately after use my right eye to view a given thing is a question to which I can certainly give an answer, and the fact that the answer is that it isn’t exactly the same precludes my saying that my experience can be identified with the color properties of the given thing, or with veridical information about those properties, or is simply a “taking in” of those objective properties (as some disjunctivists would put it), etc., etc. If the aim of this post were simply to make this point, it would be unnecessary, since Block has already made it. But I want to go more deeply into my experience when I perform this experiment.
On the beach
As I said above, I noticed this phenomenon (Hilla Jacobson and I call it, the “H phenomenon”), when I was a college student, and I noticed it by chance. I was lying on beach, and I shut my right eye so sand wouldn’t get it, and I was struck by the fact that the sand “looked different”.) I didn’t know the term then, but I can now say that the color of the sand looked less saturated—I thought of it as “paler”, or “grayer”, or something like that.  (So I was comparing the appearance when I used my left eye alone to the appearance when I used both eyes.)   When I reverted to this experience in the last twenty years, long long after my college years, instead of going to a beach I tried looking at various object—say a gray wall—using one eye and then the other, or using one eye and then both eyes, and eventually I got around to asking students to do the same and report what they experienced, and the reports were similar to my own. But, at some point (I don’t if it was already in my college years, although it might have been), I was struck by the thought that the question “Is the sand really the color it looks to be when I use my right eye, or really the color it looks to be when I use both eyes?” makes no sense. It makes no sense, although I would not have thought of that reason in my college years (even though I was a philosophy major), because what could “really be the color” mean if there is no one “color” the sand looks to be to all normal viewers?
I said “makes no sense”, but that is too “Wittgensteinian”. The point is not about language at all; certainly it is not contradictory (or a “violation of ordinary language”, or something like that) to suppose that there is such a thing as the one unique phenomenal way a thing “really looks” when seen “as it truly is”, and that some eyes (or pairs of eyes) see it that way and others don’t, even if we have no present way of discerning which eyes are thus metaphysically privileged. But it is crazy to say that. There is no basis in either the physics of color or the physiology of color vision to support the idea that some eyes have that sort of metaphysical privilege. And if that is a false metaphysics then we are stuck with Block’s “phenomenist” conclusion, that the objective (physical) properties of things, including their location in space relative to the viewer and the illumination of the scene,  do not fully determine the phenomenal character of the experience of the viewer, be she as “normal” as you wish.
But I want to go beyond this “phenomenist”  point. Yes, the question “is the wall (or the sand, in the beach case) really the shade of gray (or yellow, in the case of the sand) that it appears to be when I use my right eye or the shade it appears to be when I use both eyes, has no answer, “makes no sense”—there is no metaphysical fact to the matter to decide this “question”; but, in another way, it seems to make sense.  It takes reflection, however brief, to convince oneself that there is no such thing as the wall (or the sand) being colorwise as it looks to my left eye as opposed to its being as it looks to my right eye. It seems, at least for a moment, as it somethings may “really be” that color.  But there is no such thing as that color!   The color, or better the exact shade of gray or yellow or whatever,  that the wall seems to be when I use my right or left eye isn’t the sort of thing that a color on a paint chart is; the wall could really be, say, purple-gray32, but there is no such thing as it’s really being “gray*”, where gray* is the “shade” that the wall “seemed to be” when I used my left eye to view the wall on that occasion.  Subjective colors are impossible colors.  Like an Escher building, they seem to be real and simultaneously to be impossible. As as long I can remember how the “gray*” wall looked, I can say truly that “it looked gray*”, but “gray*” occurs intentionally, not referentially, in “looks gray*”; there is such a thing as “looking gray*” to a person at a time, but no such thing as really being gray*. Subjective colors aren’t colors; they are Escher colors.


  1. “It seems, at least for a moment, as it somethings may “really be” that color. But there is no such thing as that color! ... Subjective colors aren’t colors; they are Escher colors.”

    This is similar to the ‘general’ Buddhism. Yet, the Zen-Buddhism is slightly different. Zen does accept a solid ‘reality’ while claims that that reality is beyond the reach with ‘language’. Thus, when a Zen-student asks the ‘color’ of the sand or the wall, the ‘answer’ is a slap on student’s head, as this answer (slapping) is as good as any other possible answer.

    So, this ‘reality’ issue has been debated over 2,000 years. In fact, this issue can be settled with a simple proof in linguistics, the Martian Language Thesis -- Any human language can always establish a communication with the Martian or martian-like languages. That is, a ‘reality’ can be ‘described’ in zillion ways but,
    One, those zillion different descriptions will not change the solid reality the slightest bit.
    Two, by having that solid reality, those zillion different descriptions can always be translated among one another.

    More details about this Martian Language Thesis is available at .