Good rationalists, taken as a group, shouldn’t be systematically optimistic.
They should be if they want to win in practice, as opposed to just getting theoretically-correct answers. See, e.g., the studies referenced in Seligman’s “Learned Optimism”, that show optimists consistently out-perform pessimists (i.e., realists) in a wide variety of fields and endeavors.
(Of course, Seligman’s definition of optimism may be different from yours.)
They should be if they want to win in practice, as opposed to just getting theoretically-correct answers. See, e.g., the studies referenced in Seligman’s “Learned Optimism”, that show optimists consistently out-perform pessimists (i.e., realists) in a wide variety of fields and endeavors.
(Of course, Seligman’s definition of optimism may be different from yours.)