What is the role of sceptical scenarios—dreams, evil demons, brains in a vat—in sceptical arguments? According to the error view, sceptical scenarios illustrate the possibility of massive falsity in one’s beliefs, whereas according to the ignorance view, they illustrate the possibility of massive ignorance not necessarily due to falsity. In this paper, the ignorance view is defended by surveying the arguments in favour of it and by replying to two pressing objections against it. According to the first objection, the ignorance view illicitly introduces the kk-principle into sceptical arguments. In reply I argue that kk is not less plausible than its main rival, the closure principle. According to the second objection, relying on veridical ignorance-possibilities contradicts the transparency of belief. In reply I introduce a version of transparency that is consistent with the ignorance view.
Roush (2010) and Atkins and Nance (2014) argue for the stronger claim that the bipartite conception undermines the sceptical argument immediately. Roush does so by presenting a dilemma: Vis-à-vis the possibility of being a handless brain in a vat there is no reason to give up the knowledge claim that I have hands. That such specific possibilities do not obtain is “just not much to know” since knowing this is neither difficult nor significant. And vis-à-vis the possibility of being any kind of brain in a vat there is no reason to give up the knowledge claim either: Without incompatibility the inability to rule out being a brain in vat poses no threat. Atkins and Nance (2014) argue that with bipartite sceptical scenarios the sceptical argument is either question-begging, a transmission-failure or structurally inefficient. The argument for the premise that I do not know that not (I am a brain in a vat and not-P) must already presuppose its conclusion that I do not know that P. For, if I knew that P, I would, or easily could, know that not (I am a brain in a vat and not-P). Both versions of the objection are too quick. Roush does not explain why knowing that one is not a handless brain in a vat should be easy. It is by no means obvious why knowing this should be less difficult than knowing that one is not a brain in a vat (cf. Avnur et alii 2011). Atkins and Nance do not explain why arguing that I do not know that I am not a handless brain in a vat must rely on the premise that I do not know that I have hands. Whether that is so depends on how the premise is actually defended, not on its logical form.
See Okasha (2013) and Greco (forthcoming) for recent discussions pro kk.