Judy Benjamin is a Sleeping Beauty

Consider van Fraassen's ( 1981) Judy Benjamin (JB) problem. Judy is dropped in an area that is divided vertically in Blue (B) and Red (R) and horizontally in Headquarters (Q) and Second Company (S). These divisions define four quadrants, as in Figure 1 (roman script headings). Judy initially believes that there is an equal chance of being in each quadrant. She is then told by a fully reliable source that if she is in R, then there is a chance of q > 0.50 that she is in Q. Now ask yourself: what should Judy's credence be that she is in B on the basis of this information? I am interested here in the limiting case of this problem in which q = 1. Let us call this limiting case the JB′ problem.

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http://eprints.lse.ac.uk/31650/