http://esr.ibiblio.org/?p=1192#more-1192
ADDED: Even if you disagree with ESR's take, and many will, this is the clearest definition I have seen on what qualia is. So it should present a useful starting point, even for those who strongly disagree, to argue from.
They are incommunicable because you cannot occupy any arbitrary brainstate you want to. See the ability hypothesis.
To repeat my point: that doens't explain why other metnal content is communicable.
http://esr.ibiblio.org/?p=1192#more-1192
ADDED: Even if you disagree with ESR's take, and many will, this is the clearest definition I have seen on what qualia is. So it should present a useful starting point, even for those who strongly disagree, to argue from.