Harry Potter and the Methods of Rationality

Defeating the Dark Lord is neither selfish nor short-term. All the parts of my mind are in accord on this: If you don't answer my questions, I'll refuse to talk to you, and you won't be able to do a good and proper Sorting.

"I ought to put you in Slytherin for that!"

But that is equally an empty threat. You cannot fulfill your own fundamental values by Sorting me falsely. So let us trade fulfillments of our utility functions.

"You sly little bastard," said the Hat, in what Harry recognized as almost exactly the same tone of grudging respect he would use in the same situation. "Fine, let's get this over with as quickly as possible. But first I want your unconditional promise never to discuss with anyone else the possibility of this sort of blackmail, I am NOT doing this every time."

Done, Harry thought. I promise.

"And don't meet anyone's eyes while you're thinking about this later. Some wizards can read your thoughts if you do. Anyway, I have no idea whether or not you've been Obliviated. I'm looking at your thoughts as they form, not reading out your whole memory and analyzing it for inconsistencies in a fraction of second. I'm a hat, not a god. And I cannot and will not tell you about my conversation with the one who became the Dark Lord. I can only know, while speaking to you, a statistical summary of what I remember, a weighted average; I cannot reveal to you the inner secrets of any other child, just as I will never reveal yours. For the same reason, I can't speculate on how you got the Dark Lord's brother wand, since I cannot specifically know about the Dark Lord or any similarities between you. I can tell you that there is definitely nothing like a ghost - mind, intelligence, memory, personality, or feelings - in your scar. Otherwise it would be participating in this conversation, being under my brim. And as to the way you get angry sometimes... that was part of what I wanted to talk to you about, Sorting-wise."

Harry took a moment to absorb all this negative information. Was the Hat being honest, or just trying to present the shortest possible convincing answer -

"We both know that you have no way of checking my honesty and that you're not actually going to refuse to be Sorted based on the reply I did give you, so stop your pointless fretting and move on."

Stupid unfair asymmetric telepathy, it wasn't even letting Harry finish thinking his own -

"When I spoke of your anger, you remembered how Professor McGonagall told you that she sometimes saw something inside you that didn't seem to come from a loving family. You thought of how Hermione, after you returned from helping Neville, told you that you had seemed 'scary'."