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Canadian Journal of Philosophy 36.1 (2006) 25-56


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Revelation and Normativity in Visual Experience

Zoltán Jakab

Department Of Cognitive Science
Budapest University Of Technology And Economics
Budapest
Hungary

I A problem to start

Suppose Figure 1 depicts stimuli from an experiment on shape discrimination, where the subjects are asked to point out the best circle.


Click for larger view		 Figure 1
Stimuli from a hypothetical shape-perception experiment. See the main text for further explanation.

Now suppose that Figure 2 shows stimuli from a color-discrimination experiment where the subjects' task is to pick the purest green — green that is neither yellowish nor bluish — in other words, is unique green.


Click for larger view		 Figure 2
Stimuli from a hypothetical color-vision experiment. See the main text for further explanation.
[End Page 25]

In both these tasks there are individual differences between different subjects. However, notice that in the shape-discrimination case there is exactly one correct response: the best circle is the fourth from the left. In the color case it is not obvious, to put it mildly, that there is exactly one correct response. One color-normal subject may find that the purest green is the third from the left, whereas another may choose the fifth from the left, and still another may pick the fourth. Who is right, and who is wrong? More importantly, why is there this difference between shape perception and color perception?

A traditional explanation that dates back to Aristotle is that we access color in one perceptual modality only, whereas shape we perceive via two different modalities: visual and tactile. Two independent modalities make possible a verification of our percepts (say, percepts of a given stimulus in one modality by those of the same stimulus in another modality) which is not possible for qualities accessed in one modality only.

According to the Lockean tradition, our ideas of shapes resemble shapes in ways our ideas of colors do not resemble colors. This difference could also be used to derive an explanation of the present puzzle. However, on a recent anti-Lockean proposal, there is a fact of the matter which object color is unique green because being, say, unique green is a property as independent of observers as is being circular or being rectangular.

In what follows I shall advance a view that is closer to the Lockean than to the Aristotelian approach, and which is motivated by recent ideas in cognitive psychology and psychophysics. According to it, in the above example, there is an observer-independent fact of the matter which figure is the best circle, whereas there is no observer-independent fact of the matter which color is unique green (mutatis mutandis for other shapes and colors). However, this difference has nothing to do with how many modalities give us access to shapes versus colors. Rather, it is due to how stimulus properties are represented within a single modality. Veridicality could apply to the distribution of color percepts over physical color stimuli if we represented colors in more complex ways than we actually do (e.g., similarly to the auditory representation of sounds), still within one modality only. Moreover, veridicality would not apply to the distribution of shape percepts over the shapes if shapes were perceptually represented in much simpler ways than they actually are — even if they were represented in a number of different modalities. [End Page 26]

II Revelation in color perception

One variant of philosophical realism has it that our visual experience reveals to us the very essence of color. In order to know immediately, and exactly, what properties the colors are, all one needs is to see them. However, even though colors exist independently of observers, what perception reveals about them cannot be revealed by any other means — not, at least, via language (Johnston, 1997, 138; Campbell, 1997, 178-9; McLaughlin, 2003b, 97; Russell, 1912, 47; Strawson, 1989, 224; Byrne and Hilbert, 1997a, 2003; Stroud, 2000). One can learn empirical facts about color via scientific inquiry, but such facts alone will never teach one the essential nature of...

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