Mary the Scientist

This argument is put forth by Frank Jackson. 

Mary is a scientist confined to a room where everything is black and white. She learns every fact about the physical world, or just about everything there is to know about the physical world and how it works. If physicalism, the view that all that there is entirely physical, is true, then Mary knows everything there is to know, and so she knows everything. There isn't something she doesn't know. Yet, this does not seem true. If Mary were let out to the world and experience something Red, it would be said that Mary has actually learned something, which is, redness. She knows what it is like to experience redness. So, physicalism is false. This is the knowledge argument against physicalism. 

This doesn't seem convincing to me. First, it seems to assume that if physicalism is true, then everything must be expressed as a proposition. Even if physicalism was true, that wouldn't follow. Say Mary didn't know what strawberries taste like in her room, yet she knew all physical facts about strawberries. She wouldn't know what sweetness tasted like, but the absence of that knowledge is still knowledge of the physical world, not some non-physical one. It just can't be expressed as a proposition. What Mary has learned she could have learned as a disembodied mind, but she is also a physical being, and how she learns things physically (like what pain is) is still a type of physical knowledge which cannot be expressed as a proposition. Or take knowledge of my future wife. I may know everything there is to know about my wife in proposition form, but when I first meet her, my kind of knowing is different. 

Second, it seems to play on an intuition, and I am usually wary of intuitions. What if someone genuinely had the intuition that Mary did not experience anything new? What, are we at some sort of stalemate? So, I don't put much stock on intuition. Not to say they're not good for anything, but, if that's what we are going to hinge this argument on, then I'd pass on this argument, personally. 

Jackson would reply that I have set up a straw-man. The argument isn't that Mary learns anything new at all, and that shows physicalism is false. Rather, the argument is that while Mary learns everything there is to know about other people's experience of redness, through maybe like brain scans or something neuroscience-y, when she finally experiences Redness herself, she realizes that what she was learning about other people's experience was missing something really important. Seeing how other people react to redness is not the same as experiencing redness itself, but it is what would follow under physicalism. And since it is not the same as experiencing redness, physicalism is false (a modus tollens). 

While I think that's a slightly stronger way of putting it, that in studying someone else, she doesn't know everything about them, I still think it's fair to put forth the same criticism.