I have a certain fascination for what, my own interior vernacular, i think of as "fundamentalist logic" and this PC thing smells like that so i tried to think it through:
Seems like this PC thing can only invalid a narrow range of arguements, specifically only those from someone who bought into this whole "ideal speech situation" thing in the first place.
To wit:
you say "the ideal speech situation is implicit in everyday speech, that is, we gauge what are people say according to the ideals of truth telling, seriousness"
i say well, i think your theorectical/philosophical concept/foundational axiom of the "ideal speech situation" has some problems because...
can't spring the PC thing on me yet, right?
furthermore i say "... has some problems as a representation of "coming to an understanding"/the performative of being serious, etc. (i.e. whatever ground outside its own language that it's supposed to cover) because..."
still no PC gotcha, right?
if i say "the ideal speech isn't implicit in everyday speech"
well, maybe PC can get me now, since now i'm accepting this ideal speech thing at face value (by making an assertion about it) but even here only if the performance of this statement some shares something with every instance of "everyday speech", or to be more specific, those "certain forms of human communication, the kind we use when we want to get something accomplished"
And for this to be true either a) you define "getting something accomplished" in terms of instrumental logic and then I dare say this whole thing get wrapped up in a tautology (cause intstrumental logic is tied up with the ideal of truth) or b) you accept a bunch of metaphysics to hold this together -- for example, that the performative act of intentionally misleading someone (lying) implies the subject holds some ideal of truth telling (and if that seems like acceptable assumption, remember that animals can intentionally mislead).
Off the top of my head some problematic examples of communication "to get something done" in terms of requiring ISS: - bargaining - Laurel & Hardy trying to carry a piano together down a flight stairs
The PC arguement that i find convincing (but only convincing) is something like "people that have the cultural background to argue with Habermas about his ideas such that Habermas believes that he can seriously argue back share the ideals of ISS despite whatever protests they make to the contrary"
So how does this "*ground* social theory"? what does ISS give you that's different from any theory of rationality?
-- adam