"What Mary Didn't Know" and its Rhetorical Objections

Considering John Locke's philosophical orientation, it's not surprising that his rhetorical discussions include elements that are vital to contemporary philosophy. One particular section in the reading made me think of a popular philosophical debate I've discussed in past philosophy classes. Locke writes, “He that puts not constantly the same sign for the same idea, but uses the same words sometimes in one and sometimes in another signification, ought to pass in the schools and conversation for as fair a man, as he does in the market and exchange, who sells several things under the same name.” This logic is used in many refutations of Frank Jackson's Knowledge argument. The argument, which aims to discredit physicalism by noting that not all knowledge can be gained through physical scientific inquiry, contains the following thought experiment, often referred to as “What Mary Didn't Know:”

“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?”

Ontologically, the argument goes:

(P1) Any and every piece of physical knowledge in regard 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.

The philosophers get rhetorical in refutations of this theory. They claim that Jackson is doing what Locke warned against, using the same word to mean different things. The word in question here is “knowledge.” Laurence Demirow and David Lewis claim that Jackson fudges together the words knowledge and ability. Experiencing a color, they claim, does not provide Mary with any new facts or any new knowledge, but it rather provides her with an ability. She can now recognize red, imagine red, remember red, but none of these things are facts, they are abilities that have not added to her scientific knowledge banks. Experience can lead to ability, not knowledge, and confusing the concepts of knowledge and ability is what gets Jackson in trouble. Consider a piano. Imagine someone has spent years studying the intricacies of music theory, notation, keyboard layout etc, but has never actually sat at a piano and played it. When he finally is given a keyboard, he cannot play it at first but after a long period of practicing he can. He can now play songs and yet his factual base of musical knowledge has not expanded. His ability does not affect his knowledge. Physicalists claim that what Mary gains through experience is ability, not fact, and so her scientific, physical understanding is not proven incomplete by her new found ability, rather her knowledge of color has always been complete and the ability she gains through experience simply has nothing to do with knowledge. The philosophers point out Jackson's conceptual flaw by examining his rhetoric. Only by understanding that Jackson equates knowledge acquisition with skill acquisition do we see that his logic is flawed and thus, the rhetorical pitfall elucidated by John Locke still plays a role in the discourse of contemporary philosophy.