Research Group
in Analytic Philosophy

Abstract

Could rationality require you and I to disagree about something objective like the outcome of a coin toss even if, knowing we're equally rational, we have transmitted all of our relevant evidence to each other via communication (reaching a point where we have common knowledge that there’s nothing informative left for any of us to say)? It would be surprising if it could, for that would entail a particularly revisionary form of perspectivalism according to which some peers ought to agree to disagree in their worldly credences just because, as they would put it, “I am I, you are you”. Though most would be inclined to repudiate that type of perspectivalism, I’ll develop an argument inspired by Robert Stalnaker's discussion of the Sleeping Beauty problem to argue that one cannot both repudiate it and side with authors such as David Lewis who subscribe to the Halfer position on that case. By itself, this amounts to an exceptional, and so far unaddressed, challenge to a reputable philosophical view. But the implications of the argument extend beyond this particular case. In particular, it suggests that there's nothing essentially private or incommunicable about the epistemic import of the ‘I’ and ‘now’.