A common argument for favouring Evidential Decision Theory (EDT) over Causal Decision Theory (CDT) is that EDT has predictably higher expected returns in Newcomb Problems. But this does not show much. For almost any pair of theories, you can come up with cases where one does, on average, better than the other. Here I describe a case involving dynamic choice where EDT predictably does worse than CDT.

Jack Spencer argues we should reject a decision rule called MaxRat because it's incompatible with this principle: If you know that you will choose an option, x, and you know that x is better than every other option available to you, then it is permissible for you to choose x. I agree with Spencer that defenders of MaxRat should reject this principle. However, I disagree insofar as he suggests that he and orthodox causalists are in a position to accept it. (...) Both orthodox CDT and Spencer's own theory of rational choice are incompatible with the principle as well. It is surprising to realise, but all are agreed: it can be irrational to knowingly choose the best. (shrink)