Do you think the knowledge argument successfully refutes physicalism? Why or why not?
Knowledge argument - Wikipedia
As a person who believes in physicalism, I find this one of the stronger arguments against physicalism. That said, I think I have a response.
First, though, imagine a super-scientists, Sally, who knows everything there is to know about planetary orbits. Given the specifics of any orbit, she can tell you anything you want to know. Then, a new planet is discovered and she is informed of the characteristics of the orbit of that planet. Does she learn anything about planetary orbits? The answer, I think, is clearly yes: she learns that specific planet has those specific orbital characteristics. She can then go on to tell you anything you want to know about the orbit of that planet.
Now, let's turn to our super-neurologist Mary, who knows everything there is to know about how the brain works, but has never seen the color red.
But before we discuss Mary's experiences, suppose she is given a subject, Tom. She is given all relevant information about Tom's brain. She can answer any question she is asked about Tom's experiences: if asked how Tom would respond if he is shown a given color of green, Mary will be able to say that he will experience happiness and be reminded of the green of the Christmas tree when Tom was 7.
Does Mary learn anything when told Tom was actually shown that color of green? Let's suppose her answer was correct in all detail. Did she learn something? Again, yes, she did. She learned that Tom did, in fact, experience that color of green.
Now let's turn to Mary herself. When asked what would happen when she is shown a particular color from the long end of the visual spectrum (i.e, red), she will be able to say that she will feel a certain type of sadness because it reminds her of her mother's lipstick.
So, does Mary learn anything when she is actually shown that color of red? Yes, of course. She learns that she has just experienced that color of red. And the reason she learned that is that it just happened. Did she learn anything about the experience of redness? Yes, she learned that she just experienced it.
And she would learn this even if physicalism is true.