Sunday, July 08, 2007

Leon Kass and the Science of Color

This continues my previous post on Leon Kass's recent article in Commentary and the response from Steven Pinker.

As I have indicated, I am not persuaded by Kass's assumption that we can look to Rene Descartes--and particularly, his materialist reductionism--as determining the whole history of modern science. To me, Descartes' dualistic separation of matter and mind and his physicalist reductionism denies the emergent complexity of living phenomena as studied by Darwinian biology.

To illustrate his claim about Descartes as the founder of all modern science, Kass says that "in a revolution-making passage in the Rules for the Direction of the Mind, Descartes sets the program of all modern science by transforming how we should approach the study of color." (Like much of this article, this entire section is taken from Kass's essay on "The Permanent Limitations of Biology" in his book Life, Liberty and the Defense of Dignity, 277-97.)

Descartes says that we can study colors by arbitrarily identifying them as corresponding to various geometrical figures. Kass writes: "Descartes's geometrical figures, standing for the differences among the colors white, blue, and red may be passe, but the principle he proposes is not: today we still treat color in terms of 'wave lengths,' purely mathematical representations from which all the color is sucked out. This tells the whole story: the objective is purely quantitative. All quality disappears."

Is this really "the whole story" of the scientific study of color? Certainly, part of the story is that scientists explain visible light as a continuously varying wave-length. But this is not the whole story, because wave-lengths of light have no color intrinsic to them. Color arises only for animals that have neural systems of vision that translate the variations in wave-length into color perceptions. Different species perceive different colors or none at all.

Many anthropologists used to say that human color perception was an arbitrary creation of culture depending on the variable color vocabularies of different human languages. But in the 1960s, a famous experiment conducted by Brent Berlin and Paul Kay showed that this variation in color vocabularies followed a regular pattern indicating a universal of human nature. Native speakers of twenty languages from around the world were asked to look at a Munsell array showing the full spectrum of colors and then apply the color terms from their languages. Although there was great variation, the variation followed a universal pattern moving from two to eleven basic color terms. The reason for this is that the human sensory system for vision tends to break down the continuing varying wavelengths of visible light into discrete units.

Notice that Berlin and Kay had to ask their subjects to report their subjective experience of color in the terms of their color vocabularies. Color as a perceptual quality is known to us only by our subjective experience. But we can testify to that qualitative experience through language that can then be the basis for scientific study. It is not true, then, that for modern science, "all quality disappears."

Edward O. Wilson--in his book Consilience: The Unity of Knowledge--offers the Berlin and Kay study of color vocabularies as an example of "gene-culture coevolution" guided by "epigenetic rules." He writes: "The brain constantly searches for meaning, for connections between objects and qualities that cross-cut the senses and provide information about external existence. We penetrate that world through the constraining portals of the epigenetic rules. As shown in the elementary cases of paralanguage and color vocabulary, culture has risen from the genes and forever bears their stamp. With the invention of metaphor and new meaning, it has at the same time acquired a life of its own. In order to grasp the human condition, both the genes and culture must be understood, not separately in the traditional manner of science and the humanities, but together, in recognition of the realities of human evolution" (163).

In my chapter on "emergence" in Darwinian Conservatism, I indicated that although Wilson sometimes identifies "consilience"--the unity of all knowledge--as based on a strong form of reductionism, he has to recognize the emergent complexity of life that cannot be explained through strong reductionism. So, for example, the epigenetic rules of human biology shape the broad patterns in color vocabularies that are universal propensities across all human societies. But within those broad patterns, the specific content of color vocabularies will be determined by linguistic practices, social customs, and deliberate choices that are peculiar to some particular group. And our scientific studies of color perception must combine quantitative methods of objectified science with the qualitative experience of human subjects expressed in language.

Such scientific study of the emergent complexity of life is lost in Kass's assumption that Descartes's reductionism "sets the program of all modern science."

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