Abstract

Currently, it appears that the most widely accepted solution to the Sleeping Beauty problem is the one-third solution. Another widely held view is that an agent’s credences should be countably additive. In what follows, I will argue that these two views are incompatible, since the principles that underlie the one-third solution are inconsistent with the principle of Countable Additivity (hereafter, CA). I will then argue that this incompatibility is a serious problems for thirders, since it undermines one of the central arguments for their position.