 The intuition that two-boxing is the rational choice in a Newcomb problem, or that defection is the rational choice in the PD with positive correlation between the players' moves, seems to conflict with the idea that rationality requires maximizing expectation. This apparent conflict has led some to suggest that standard decision theory needs to be refined in cases in which an agent's actions provide evidence for, without causing, the context in which he is acting. In the case of the PD, standard (evidential) decision theory asks Player One to compare his expected utilities of cooperation and defection, which can be written as \(p(\bC_2 \mid \bC_1) \times R + p(\bD_2 \mid \bC_1) \times S\) and \(p(\bC_2 \mid \bD_1) \times T + p(\bD_2 \mid \bD_1) \times P\) (where, for example, \(p(\bC_2 \mid \bC_1)\) is the conditional probability that player Two cooperates given that Player One cooperates). If the players' moves are strongly correlated then \(p(\bC_2 \mid \bC_1)\) and \(p(\bD_2 \mid \bD_1)\) will be close to one and \(p(\bC_2 \mid \bD_1)\) and \(p(\bD_2 \mid \bC_1)\) will be close to zero. On the suggested revision, these conditional probabilities should be replaced by some kind of causally conditional probabilities, which might (on some accounts) be expressed by phrases like “the probability that if One were to cooperate, Two would also cooperate.” When the moves are causality independent this would just be the probability that Two cooperates.