Abstract

There are two epistemological problems connected with dreaming, which are of different kinds and require different treatment. The internal problem is best seen as a problem of rational consistency, of how we can maintain all of: Dreams are experiences we have during sleep. Dream-experiences are sufficiently similar to waking experiences for the subject to be able to mistake them for waking experiences. We can tell that we are awake. (1)-(3) threaten to violate a requirement on discrimination: that we can only tell Xs from Ys if there is some detectable difference between Xs and Ys. Attempts to solve the problem by Descartes and Williams are considered. It is suggested that if we take account of levels of epistemic risk, we can use Descartes's criterion of lack of coherence, at least with hindsight - which is the time when we need to use it.