Color Ontology and Color Science

10. How Can the Logic of Color Concepts Apply to Afterimage Colors?

10 How Can the Logic of Color Concepts Apply to Afterimage Colors? Jonathan Westphal 10.1 Personal It is often remarked that since the 1980s, there has been a dramatic increase in the amount of work being done in analytic philosophy on the philosophy of color. One of the causes was the publication of C. L. (Larry) Hardin’s groundbreaking work in the area, Color for Philosophers: Unweaving the Rainbow (1988, 1993), but apart from causing lots of other people to get into the field, Larry has been the main contributor to it. In addition to that book, I count nineteen very substantial articles about color in the ten years from 1983 to 1993, and there are probably more that I don’t know about. I was introduced to Larry at an Eastern Division APA meeting in the mid-1980s by Hilary Putnam, who thought we should get together because we both seemed obsessed with color. I remember that Larry and I had dinner and talked about our plans for the subject. He wanted to develop the philosophy of color in close connection with the science of color, and although I knew that this was very important, and wanted to contribute as much as I was able, my own more primitive interests seemed to point toward Wittgenstein and toward a limit to the science of color in its received form. “OK,” I said, “You do the science, and I’ll do Wittgenstein and some metaphysics,” and instantly regretted it. But for the most part we have stuck to the agreement. I am enormously proud to say that we reviewed one another’s books in the same number of Mind, his on color and science and mine on color and Wittgenstein. I had no idea, on that evening in Washington, that I was talking to someone who would become the doyen of color philosophy and a model practitioner of the new art, and I would have been even more shocked to have been told that within twenty years, the vague hope I had for the subject would become a reality. The vague hope was that there would be a detailed, responsible, and scientifically well-informed philosophy of color that was entirely sensitive to logical and conceptual issues. To some extent this already existed, for example, in the work of the Australian School (Armstrong, Smart and Campbell), and in the still earlier debate about the persistent problem of color incompatibility , though this debate tended not to include science. But Hardin’s work brought 246 Jonathan Westphal the different strands together, and it was the focus of what became in effect an academic specialty. He showed the way to other talented people who are now working in the field so effectively, such as Justin Broackes, Alex Byrne, Jonathan Cohen, Austen Clarke, Don Dedrick, David Hilbert, and Evan Thompson. So I am very happy about the state of the art. On the other hand, I am not as happy about the way in which color science has been deployed to sort out the problems of color incompatibility that were so important in the history of twentieth-century metaphysics and epistemology, starting with the Tractatus. Many quasilogical, semantic, and metaphysical questions having to do with incompatibility come up in color theory, and the problem is so tricky and delicate that I do not believe we have got it quite sorted out yet, despite some marvelous work on the topic. The trouble is especially acute in Larry’s favorite haunt, the subjective, as it is called, which has flying around in it, among other things, what are known as afterimages. My topic in this chapter is the incompatibility of afterimage colors. Every naïve subject I have talked to who encounters afterimages without prejudice has agreed that they have color; I mention this because I think it is the initial and also the commonsense view. But if a physical account of color incompatibility is right for physical colors, how can we account for the incompatibility of afterimage colors? One can of course give a physiological account based on opponent processes. But this will deliver at best a contingent truth, or a necessity relative only to a particular retinal structure and postretinal neural coding. 10.2 Wittgenstein’s Puzzle Propositions 10.2.1 Introduction and the Puzzle Propositions and Questions In Remarks on Colour, Wittgenstein (1978) wrestled with certain questions, very important ones in the development of analytic philosophy, about the impossibility of certain colors and...