 But is the tension real? One pro argument is a reductio ad absurdum: The claim is that EXT and SK jointly entail an obvious falsehood, namely, that Oscar can know from the armchair contingent facts about the external world (McKinsey 1991; 1994; 2002; 2007, Brown 1995, Boghossian 1997; 1998). If so, then EXT and SK cannot be jointly true, and the incompatibilist wins the debate.