Why should evidence of bias be some evidence against a belief? This would be like magic: using someone's failure of rationality to learn something about the world, which is absurd. (Example: Federer's wife is very confident that he will win, because she is biased in his favor. Does this give me any reason to bet against Federer? Obviously not.)
Why should evidence of bias be some evidence against a belief? This would be like magic: using someone's failure of rationality to learn something about the world, which is absurd. (Example: Federer's wife is very confident that he will win, because she is biased in his favor. Does this give me any reason to bet against Federer? Obviously not.)