 It is perfectly obvious to Don and his audience (Carla) that what Don has said is something he does not believe, and the audience knows that Don knows that is obvious to the audience. So … Don must be trying to get across some other proposition than the one he purports to be putting forward. This must be some obviously related proposition; the most obviously related proposition is the contradictory of the one he purports to be putting forward. (After Grice 1975:  34).[39]