I agree that the order matters, and I should have discussed that in the post, but I think the conclusion will hold either way. In the case where P(intelligent ancestor|just my background information) = 0.1, and I learn that Richard disagrees, the probability then goes above 0.1. But then when I learn that Richard’s argument is bad it goes back down. And I think it should still go below 0.1, assuming you antecedently knew that there were some smart people who disagreed. You’ve learned that, for at least some smart intelligent ancestor believers, the arguments were worse than you expected.
I agree that the order matters, and I should have discussed that in the post, but I think the conclusion will hold either way. In the case where P(intelligent ancestor|just my background information) = 0.1, and I learn that Richard disagrees, the probability then goes above 0.1. But then when I learn that Richard’s argument is bad it goes back down. And I think it should still go below 0.1, assuming you antecedently knew that there were some smart people who disagreed. You’ve learned that, for at least some smart intelligent ancestor believers, the arguments were worse than you expected.