It is possible to use language meaningfully without knowing exactly how it pans out in terms of precise configurations of matter, and also without denying that it eventually does. Treating pain semantically as some specific brain activity buys you nothing in terms of the ability to communicate and understand .... when you don't know which precise kind...which you don't. If Purple and Bitter are both Brain Activity Not Otherwise Specified, they are the same. If you can solve the mind body problem , then you will be in the position to specify the different kinds of brain activity they are. But you can also distinguish them , here and now, using the subjectively obvious difference. And without committing yourself to evil dualism.
It is possible to use language meaningfully without knowing exactly how it pans out in terms of precise configurations of matter
I have never claimed otherwise. In fact, there is literally nothing that I have exact description of, in terms of matter - neither pain nor chairs. But you have to know something. I know that "chair is what I sit on" and from that there is a natural way to derive many statements about chairs. I know that "gravity is what makes things fall down", and from that there is a fairly straightforward way to the curr...
(This post grew out of an old conversation with Wei Dai.)
Imagine a person sitting in a room, communicating with the outside world through a terminal. Further imagine that the person knows some secret fact (e.g. that the Moon landings were a hoax), but is absolutely committed to never revealing their knowledge of it in any way.
Can you, by observing the input-output behavior of the system, distinguish it from a person who doesn't know the secret, or knows some other secret instead?
Clearly the only reasonable answer is "no, not in general".
Now imagine a person in the same situation, claiming to possess some mental skill that's hard for you to verify (e.g. visualizing four-dimensional objects in their mind's eye). Can you, by observing the input-output behavior, distinguish it from someone who is lying about having the skill, but has a good grasp of four-dimensional math otherwise?
Again, clearly, the only reasonable answer is "not in general".
Now imagine a sealed box that behaves exactly like a human, dutifully saying things like "I'm conscious", "I experience red" and so on. Moreover, you know from trustworthy sources that the box was built by scanning a human brain, and then optimizing the resulting program to use less CPU and memory (preserving the same input-output behavior). Would you be willing to trust that the box is in fact conscious, and has the same internal experiences as the human brain it was created from?
A philosopher believing in computationalism would emphatically say yes. But considering the examples above, I would say I'm not sure! Not at all!