In the video above, Prof. David Papineau compares different "naturalist" theories of consciousness to propose that phenomenal concepts pose a problem for Wittgenstein's private language argument. (A version of this issue was briefly raised during the second episode discussing Philosophical Investigations.) Hint: If you're not yet familar with the "Mary's Room" thought experiment, it would be helpful to review a synopsis.
Click here for Papineau's paper, which commits the lecture to print, and might make it easier to follow:
The question I now wish to address is whether phenomenal concepts are inconsistent with Wittgenstein's private language argument. Certainly there would seem to be a tension here. After all, phenomenal concepts are posited specifically to accommodate distinctive ways of thinking about subjective states. Moreover, these ways of thinking are only available to people who have had those experiences themselves. This certainly looks like the kind of thing Wittgenstein was against.
Still, we should not be too quick. Clearly Wittgenstein did not want to rule out all possible terminology for states which would normally be counted as ‘subjective’. After all, words like 'pain' and 'seeing something red' are normal everyday terms. Nor presumably would he have objected to the idea that, once you have had certain experiences, you are thereby able to imaginatively recreate them and introspectively reidentify them in ways that you couldn't before.
However, phenomenal concepts involve more than these relatively digestible aspects of discourse about ‘subjective’ states.
Papineau is refreshingly articulate regarding his "scientific realist" views; to wit, yes, things really do exist, even if you can't directly observe them. He had a clever back-and-forth with Nigel Warburton on Philosophy Bites, where he came across to me as more a pragmatist than anything else:
Q: So you're saying that we should be a skeptic about some areas of science, and a realist about others?
A: Absolutely. And if you think that I'm kind of giving up on, "Well I promised you earlier scientific realism," well, that's too bad, because it seems to me the position I've outlined is obviously the sensible one. I mean, if you think about the question in the first place, "Should we be realists about science, about everything put forward by people who claim the authority of scientists," well, why should we? I mean, we should be realists about good theories and we should be skeptical about dodgy ones.
Q: The difficulty, of course, is finding out which are good and which are dodgy.