Online research in philosophy

It has been suggested that difficult-to-quantify differences in visual processing may prevent researchers from equating the color experience of different observers. However, spectral locations of unique hues are remarkably invariant with respect to everything other than gross differences in preretinal and photoreceptor absorptions. This suggests a stereotyping of neural color processing and leads us to posit that minor differences in observer neurophysiology may be irrelevant to color experience.

Let me begin by indicating where I think Harman and I are in agreement. We both think that "subjective reactions" must come into an account of color, although we have different views about how they do. We both think that perceptual experience has a "presentational or representational character," and that color is represented by our visual experiences as a feature of external objects, not as a feature of our experience. Moreover, we agree that, as Harman puts it, "color is experienced as a simple basic quality, rather than a disposition or complex of causal properties." As Harman emphasized in an earlier paper, 1 what we are introspectively aware of in our experience is its presentational or representational content, not any "mental paint" which bestows this content. I shall refer to all of this as Harman's "phenomenological point." Because we agree on this, we also agree that if his characters George and Mary were spectrum inverted relative to each other, supposing that to be possible, this would have to involve their perceiving the same objects as having different properties, this despite the fact that as normal perceivers they would perceive these objects as having the same colors. And I think we agree that in this case the properties would have to be relational ones, defined or constituted by their relations to the experiences of the subject perceiving them.

Philosophy has long struggled to understand the nature of color. The central role color plays in our lives, in visual experience, in art, as a metaphor for emotions, has made it an obvious candidate for philosophical reflection. Understanding the nature of color, however, has proved a daunting task, despite the numerous fields that contribute to the project. Even knowing how to start can be difficult. Is color to be understood as an objective part of reality, a property of objects with a status similar to shape and size? Or is color more like pain, to be found only in experience and so somehow subjective? Or is color more like what some have said about time--that it seems real until we reflect enough, where we come ultimately to dismiss it as mere illusion? If color is more like shape and size, can we give a scientific account of it? Various strategies exist for this option--taking the color of an object to be just a complicated texture of that object, one that reflects certain wavelengths. Or perhaps color is merely a disposition to cause experiences in us, as salt has a disposition to dissolve. On the other hand, if color is more like pain, and found only in subjective experience, what is the nature of color experience? How, for instance, does an experience of red differ from an experience of blue, or from an experience of pain for that matter? Finally, if color is mere illusion, how do we continue to be so taken in by that illusion and how can something unreal seem so real and important to us?

Hardin argues that Reflectance Physicalism about color fails because it cannot accommodate color structure. David Lewis and others have replied that the Reflectance Physicalist may explain color structure in terms of color experience. I argue that this reply fails.

Ross argues that the location problem for color-the problem of how it is represented as occupying a particular location in space-constitutes an objection to color subjectivism. There are two ways in which the location problem can be interpreted. First, it can be read as a why-question about the relation of visual experience to the environment represented: Why does visual experience represent a patch of color as located in this part of space rather than that? On this interpretation, the subjectivist can answer Ross's objection by appealing to the physical location of reflectance rather than color. Second, it can be read as a how-question about visual representation itself: How does visual experience put together the experience of a color with the experience of its being located in space? This version makes the location problem a problem about visual experience itself and renders the ontology of color irrelevant to its solution. The location problem is thus no more a problem for the color subjectivist than for the color realist.

In this paper I argue that color is a relational feature of the distal objects of perception, a way of appearing. I begin by outlining three constraints any theory of color should satisfy: (i) physicalism about the non-mental world, (ii) consistency with what is known from color science, and (iii) transparency about color experience. Traditional positions on the ontological status of color, such as physicalist reduction of color to spectral re?ectance, subjectivism, dispositional- ism, and primitivism, fail, I claim, to meet all three constraints. By treating color as a relational property, a way of appearing, the three constraints can be met. However, serious problems for this view emerge when considering the relation between illusory color experiences (particularly hallucinations) and veridical color experiences. I do not propose a solution to these problems.

Despite a wealth of data we still have no clear idea what color experiences represent. In fact, color experiences vary with so many factors that it has been claimed that they do not represent anything at all. The primary challenge for any representational account of color experience is to accommodate the various psychophysical results that demonstrate that color appearance depends not only on the spectral nature of the target but also on the spectral, spatial and figural nature of the surround. A number of theorists have proposed that this dependence is an aspect of the visual system's constancy mechanism. However this does not in and of itself tell us what, if anything, is represented in color experience. Ultimately the answer to this question will be informed by one's theory of representational content. I will argue that adopting a molecular scheme of representation enables the development of an account of the represented object of color experience that can do justice to the psychophysical data.

In this Response, I defend the notion of intrinsic qualities of experience, discuss the distinction between relational experience and relational structure, clarify the difference between narrow and broad interpretations of color experience, argue against externalist approaches to color experience, defend the concept of isomorphism as a limitation in understanding color experiences, examine critiques of the color machine and color room arguments, and counter objections to within-subject experiments based on memory limitations.

What is the relationship between color experience and color? Here, I defend the view that it is semantic: color experience denotes color in a code innately known by the perceiver. This semantic theory contrasts with a variety of theories according to which color is defined as the cause of color experience (in a special set of circumstances). It also contrasts with primary quality theories of color, which treat color as a physical quantity. I argue that the semantic theory better accounts for the kinds of knowledge we have regarding both the color of objects that we see and of the colors themselves.