Archive for the ‘Reading Notes’ Category

Reddish Green

Sunday, July 22nd, 2007

The following figure is from “REDDISH GREEN: A CHALLENGE FOR MODAL CLAIMS ABOUT PHENOMENAL STRUCTURE” by Martine Nida-Rumelin & Juan Suarez (link to pdf) and reproduces stimuli utilized in experiments in which paradoxical visual experiences were induced, such as experiences of a single color patch being colored reddish green.


Some subjects report “seeing a homogeneous color phenomenally composed of red and green whose components are as clear and as compelling as the red and blue components of a purple.”

The phenomenon is induced by presenting equilluminant colored stripes in images stabilized via use of an eye-tracker. The experiments reported are from Billock et al. which reproduce experiments from Crane and Piantanida.


Billock, V. A., Gleason, G. A., & Tsou, B. H. (2001). “Perception of forbidden colors in retinally stabilized equiluminant images: an indication of softwired cortical color opponency?” J Opt Soc Am A Opt Image Sci Vis, 18(10), 2398-403.

Crane, H. D., & Piantanida, T. P. (1983). “On Seeing Reddish Green and Yellowish Blue.” Science, 221(4615), 1078-1080.

See also my “Hyperbolic Mary

Concepts, Contexts, and Kelly Cases

Friday, June 15th, 2007

In some cases, colors descriminable in simultaneous presentations are indescriminable in serial presentations. I’ll call such cases “Kelly Cases” for they play a central role in Sean Kelly’s arguments against the conceptual constitution of perception (hereafter, “conceptualism”) (Kelly, S. 2001. “Demonstrative Concepts and Experience” The Philosophical Review, 110, 3: 397-420).

Of course, a more accurate description of Kelly’s target is a demonstrative-concepts defense of conceptualism. My intent here is to defend conceptualism without relying on demonstrative concepts.

Kelly cases raise trouble for conceptualism only if accompanied by certain assumptions. One assumption, discussed quite a bit by Kelly, is a re-identifiability requirement on concept possession: in order to have a concept of something, one must be able to identify that something on separate occasions. Another assumption, discussed very little, if at all, by Kelly, is that the perceptual contents in the simultaneous and serial presentations differ only with respect to their time of presentation.

The first assumption doesn’t bother me too much. I question the second assumption.

There are lots and lots of cases in which the context of presentation messes with the discriminability of the colors presented. One of my favorites involves the color contrast cubes depicted below.

Figure 1. This is awesome.

In this image, the “blue” tiles on the top of the left cube and the “yellow” tiles on the top right are actually neither blue nor yellow but the same shade of gray. See a cool animated demonstration of this over at Dale Purves’s Lab webpage here.

It’s open, then, for conceptualism to be protected by treating simultaneous and serial presentations as different contexts that give rise to differences in perceptual content. Of course, the question arises of how to characterize the differences conceptually. It would be consistent with conceptualism to say something like that in the simultaneous half of the Kelly case, the concepts applied are a concept of, say, green plus the concept of difference-in-shade; and that in the serial half of the Kelly case, there is no application of the concept of difference-in-shade.

Note that the defense of conceptualism sketched here is not the demonstrative-concepts defense of McDowell and Brewer that constitutes Kelly’s main target. I envision that the demonstrative-concepts defense would have to say something like that in the simultaneous half of the Kelly case, the concepts applied are the demonstrative concepts that-shade-1, that-shade-2, and the concept of difference; and that in the serial half of the Kelly case, there is no application of the concept of difference. The question arises, however, of what is going on besides a failure of noticing a difference in the serial half. It must be either that (1) the serial case involves neither that-shade-1 nor that-shade-2, (2) only that-shade-1 is applied, or (3) only that-shade-2 is applied.

An objection to this version of the demonstrative-concepts defense that may be raised at this point is that neither (1), (2), nor (3) would constitute the satisfaction of the re-identifiability condition on conceptual content. So, for example, in (2) the shade identified in the simultaneous half of the Kelly case as that-shade-2 is not being re-identified.

Thankfully, I’m not leaning on demonstrative concepts here, and thus the problem raised is somebody else’s problem.

[UPDATE (6/19/2007): I really don't like the last three paragraphs of this post.]

Gibbons’ “Qualia: They’re Not What They Seem”

Monday, February 12th, 2007

Light Leaks

Originally uploaded by Pete Mandik.

Reading Notes on John Gibbons’ “Qualia: They’re Not What They Seem” Philosophical Studies 126:33, 397-428, Kluwer, 2005.

Ways things seem are not invertable. Intuitively, they would have been. Qualia are not the ways things seem and we should not trust our intuitions about them. There are unlikely to be good arguments for the existence of qualia. Certainly, we can’t trust claims that qualia are obvious.

§2. A Surprising Impossibility
Ways things seem cannot be inverted between Laverne and Shirley. Laverene and Shirley learned the same language in the same environments. They both call red things “red” and they both believe what they say. When they say “x seems red” it is true.

§3. A Surprisingly Unstable Situation
If transported to Inverted Earth and fitted with reversing lenses, you will call green things “red” and mean red. You will have systematically false beliefs. But over time the meanings of your terms will change: when you say “red” it will refer to green. Not only will the meanings of your words change, so do the contents of your beliefs. The ways things seem to you have changed without your noticing. But this has been accompanied by a change in the meanings of your words and thought contents.

§4. Should we believe in qualia at all?
Red qualia are the redness in the mind. Three main but not good reasons for believing in the redness in the mind are introspection, intrasubjective spectrum inversion, and the argument from illusion.

Bad reason 1: Introspection
Introspection does not tell us that there is redness in the mind. When we go looking for redness we find it in the objects in the world.

Bad reason 2: Intrasubjective spectrum inversions
Qualia are hypothesized to explain a certain case. This is not a great reason for believing in qualia if there are other ways to explain the case

The case and the qualia explanation
You put on inverting lenses and eventually get used to them. Before putting them on, grass looks green. Right after putting them on, grass looks red. What we need an explanation for is what to say about after you get used to them. One thing you might say is that the grass seems green in one sense and in another sense seems red. This is the qualia strategy. It postulates that there are two kinds of “seeming”, “looking”, etc.. There are two senses for every appearance concept: an epistemic sense that has to do with the representational content of judgments and a phenomenal sense that has to do with qualia.

The Non-qualia explanation of the case
Where the qualia explanation postulates an ambiguity in the meaning of “seems”, the non-qualia strategy postulates an ambivalence people have about whether one’s representational contents can change without one noticing. So, prior to the lenses, one represents grass as green. Right after, one represents grass as red. After one has gotten used to the glasses, one is ambivalent about whether one’s experiences still represent the grass as red or now represent it as green. The non-qualia explanation is also able to explain what it is like to undergo experiences similar to intrasubjective spectrum inversion like getting used to sunglasses. Here, the difference of what it is like is doe to differences in the operation of thought. It is not weird to think that thought influences what it is like. Consider what it is like to taste wine before and after gaining wine-tasting expertise.

Bad reason 3: The argument from illusion
The argument goes something like this. Things can look red even though they are not red. But in order for things to look red, something or other has to be red. So, when you undergo the illusion that something external to you is red, what is really happening is that you are experiencing the redness in your mind. Such an argument about rock illusions wouldn’t suffice to show that you had rocks in your head. Just rock beliefs, that is, beliefs about rocks. If the argument from illusion doesn’t suffice to show that you have rocks in your head, why think it suffices to show that you have redness in the mind? Is there some special distinction between properties like redness for which the argument works and properties like rock-ness for which it does not?
Failed attempts at such a distinction:
-Secondary vs. primary qualities
-Just seen vs inferred properties
Secondary vs. primary won’t work because things that are red must be shaped. This puts shapes in the head too and they are no better than rocks in the head.
Just seen vs inferred properties won’t work because something can seem like a rock even though you believe I isn’t. If you don’t believe it you don’t infer it.

Hawthorne’s “Direct Reference and Dancing Qualia”

Tuesday, December 19th, 2006

Reading Notes on John Hawthorne’s “Direct Reference and Dancing Qualia” In (T. Alter and S. Walter) Phenomenal Concepts and Phenomenal Knowledge (OUP, 2006).
Hawthorne’s main thesis: Direct reference theory for phenomenal concepts is incompatible with the dualist possibility of dancing qualia.

What is the gist of Hawthorne’s argument?

Hawthorne wants to argue that if qualia can dance, then there are certain situations in which one might not be sure whether one concept and another concept refered to the same qualia. Further, Hwthorne wants to argue, in such situations, it looks like what is going on is more like wondering whether “Hesperus = Phospherus” than being unsure about the a priori knowable “Hesperus = Hesperus”. Thus, if qualia can dance, Fregeanism, not Russellianism is a better theory of phenomenal concepts.