I have a question about Cartesian skepticism. One of the premises of the argument is something to the effect of:
(1) I don't know that I'm not dreaming.
My question is: What justifies this proposition? My intuition is that the evidence for (1) cannot possibly be empirical; for the upshot of the skeptical argument is precisely that all empirical claims are dubious. (Maybe it's helpful to rephrase (1) as "It's possible that I'm dreaming," if that is legitimate.)