• Korean Journal of Logic
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• v.15 no.1
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• pp.107-154
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• 2012

In my previous paper (2009), I defended a solution of the Sleeping Beauty problem, according to which, on Monday, Sleeping Beauty assigns a lower credence to the coin's landing heads than 1/2. This conclusion was largely favorable to the Thirder view. However, even if my defense of the Thirder view was successful, it left one important question to be unanswered: Where did the Halfers go wrong? Their main argument was simple: Because Sleeping Beauty does not receive new and relevant evidence about how the coin lands, her credence in its landing heads should remain to be the same. But note that, if the Thirder view was right and Sleeping Beauty receives no new and relevant evidence, then this becomes a special case of the so-called old evidence problem (Glymour, 1980). In this paper, I will explain why it is rational for Sleeping Beauty to change her credence despite the lack of new evidence about the coin's landing heads. For this explanation, I will use Garber's well-known solution to the old evidence problem.