Well, that’s the sticking point. Parseltongue and the Vow prove that Harry is honest. They don’t prove that he’s right, and Voldemort can simply choose to dismiss any of Harry’s arguments as insufficient (which isn’t that hard, given that the risk of keeping him alive is the end of the world, and any risk incurred by killing him is probably going to be less bad).
Well, that’s the sticking point. Parseltongue and the Vow prove that Harry is honest. They don’t prove that he’s right, and Voldemort can simply choose to dismiss any of Harry’s arguments as insufficient (which isn’t that hard, given that the risk of keeping him alive is the end of the world, and any risk incurred by killing him is probably going to be less bad).
http://lesswrong.com/r/discussion/lw/lsp/harry_potter_and_the_methods_of_rationality/c22c