Consider a woman, Mary, who is color blind. She is a neuroscientist, and knows absolutely everything there is to know about color, all the wavelengths and all the effects of light on the eye, etc.. There is nothing she doesn’t know about it. But she has never, herself, experienced it. One day, a surgical procedure is developed, allowing her to see color for the first time. Does Mary gain any new knowledge?
So is formulated one of the modern classic philosophical arguments, and one that, honestly, is built on such a false premise that it’s difficult to believe that it’s had as much traction as it’s had. Rather than go through all the logical argumentation, I’ll simply rewrite the analogy, and the flaws should become glaringly obvious.
Consider a young man, Gary, who is a virgin. He is eighteen years old, and knows absolutely everything there is to know about sex. Thanks to the internet, there is nothing he does not know about it. But he, himself, has never actually had sex. One day, he goes on a date with a woman, and after dinner and a movie, they make love. Does Gary gain any new knowledge?
Obviously, Gary could not have full and complete knowledge of sex. Any claim as such is non-sense. There is no refutation of physicalism, because he never had the knowledge in the first place; he does not have all the physical knowledge, so his gain of new knowledge is nothing significant. He could imagine it, he could try to synthesize what it would be like, he could try to create a simulacrum via masturbation, etc. but any claim to absolute knowledge of the subject is necessarily false.