 As should be clear, slow switch arguments can be seen as skeptical arguments, where the skeptic raises the possibility that we are in Oscar’s predicament. The externalist is thus asked to rule out deviant thought contents from the armchair. Moreover, since the skeptic thinks she cannot do so, he claims that the externalist lacks armchair self-knowledge. But one sort of reply is that such skepticism is self-undermining (Ebbs 1996; 2001; 2005; Brueckner &amp; Ebbs, 2012, ch. 12). The contention is that, assuming EXT, the skeptic cannot both deny SK and be justified in accepting the premises of his own argument. If so, skeptical slow switch arguments end up being incoherent.