Abstract

In this paper I defend the thirder solution to the sleeping beauty problem by considering the credence Beauty ought to have, upon first awakening, that it is Monday. This leads to problems for the double-halfer and halfer but not for the thirder. In the three cases the credences Beauty ought to have, upon first awakening, that it is Monday are 1, 3/4, and 2/3, respectively. The first value is implausible given that Tuesday awakenings are possible. The second is implausible because Beauty's credence in the day of the week is linked to her credence in the result of the coin toss such that evidence to favor Monday over Tuesday is evidence that should affect her credence in the result of the coin toss. This is contrary to the halfers' claim that, upon first awakening, Beauty has no such evidence. However, the credence of 2/3 assigned by the thirder can be independently defended in a way that mirrors the thirders defense of assigning a credence of 1/3 to Heads. Moreover, recognizing the probabilistic connection between Beauty's credences in the days of the week and the results of the coin toss indicates the nature of Beauty's inadmissible information. Beauty's loss of information regarding the day is relevant to the credence she should assign to Heads.