04 May 2010

XKCD & Epiphenomenal Qualia

Randall Munroe's survey results on how people perceive and name colors has been making the rounds since he posted it yesterday. Results are definitely worth a look.

Color fascinates me because it is a great example of the subjectivity of experience and knowledge. 2+2 will always be 4, no matter who says otherwise or what words we use to describe it. But "red" ... what is "red"? Even if you and I agreed on exactly what wavelength of light corresponded to red and viewed that light in exactly the same conditions, can I ever be sure that you and I are experiencing the exact same mental state when it comes to redness?

If you read only one article on cognitive science and philosophy this year, make it Frank Jackson's 1982 paper "Epiphenomenal Qualia." Here's how Wikipedia describes the central conceit:
The ["Mary's Room"] thought experiment was originally proposed by Frank Jackson as follows:
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. [...] What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?
In other words, Jackson's Mary is a scientist who knows everything there is to know about the science of color, but has never experienced color. The question that Jackson raises is: once she experiences color, does she learn anything new?

Ontologically, the following argument is contained in the thought experiment:

(P1) Any and every piece of physical knowledge in regards to human color vision has been obtained (by the test subject, Mary) prior to her release from the black-and-white room. She has all the physical knowledge on the subject.

(P2) Upon leaving the room and witnessing color first-hand, she obtains new knowledge.

(C) There was some knowledge about human color vision she did not have prior to her release. Therefore, not all knowledge is physical knowledge.

(PS If you were to read a second paper in this vein, make it Thomas Nagel's "What is it like to be a bat," from 1974.)

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