Harry Potter and the Methods of Rationality

There was a pause.

"Your... dark side..."

Harry sat up. Professor Quirrell was regarding him with one of the strangest expressions Harry had seen on anyone's face, let alone anyone as dignified as Professor Quirrell.

"It happens when I get angry," Harry explained. "My blood runs cold, everything gets cold, everything seems perfectly clear... In retrospect it's been with me for a while - in my first year of Muggle school, someone tried to take away my ball during recess and I held it behind my back and kicked him in the solar plexus which I'd read was a weak point, and the other kids didn't bother me after that. And I bit a math teacher when she wouldn't accept my dominance. But it's only just recently that I've been under enough stress to notice that it's an actual, you know, mysterious dark side, and not just an anger management problem like the school psychologist said. And I don't have any super magical powers when it happens, that was one of the first things I checked."

Professor Quirrell rubbed his nose. "Let me think about this," he said.

Harry waited in silence for a full minute. He used that time to stand up, which was more difficult than he had expected.

"Well," Professor Quirrell said after a while. "I suppose there was something you could say that would convince me."

"I have already guessed that my dark side is really just another part of me and that the answer isn't to never become angry but to learn to stay in control by accepting it, I'm not dumb or anything and I've seen this story enough times to know where it's going, but it's hard and you seem like the person to help me."

"Well... yes... very perspicacious of you, Mr. Potter, I must say... that side of you is, as you seem to have already surmised, your intent to kill, which as you say is a part of you..."

"And needs to be trained," Harry said, completing the pattern.

"And needs to be trained, yes." That strange expression was still on Professor Quirrell's face. "Mr. Potter, if you truly do not wish to be the next Dark Lord, then what was the ambition which the Sorting Hat tried to convince you to abandon, the ambition for which you were Sorted into Slytherin?"

"I was Sorted into Ravenclaw!"

"Mr. Potter," said Professor Quirrell, now with a much more usual-looking dry smile, "I know you are accustomed to everyone around you being a fool, but please do not mistake me for one of them. The likelihood that the Sorting Hat would play its first prank in eight hundred years while it was upon your head is so small as to not be worth considering. I suppose it is barely possible that you snapped your fingers and invented some simple and clever way to defeat the anti-tampering spells upon the Hat, though I myself can think of no such method. But by far the most probable explanation is that Dumbledore decided he was not happy with the Hat's choice for the Boy-Who-Lived. This is evident to anyone with the tiniest smidgin of common sense, so your secret is safe at Hogwarts."

Harry opened his mouth, then closed it again with a feeling of complete helplessness. Professor Quirrell was wrong, but wrong in such a convincing way that Harry was starting to think that it simply was the rational judgment given the evidence available to Professor Quirrell. There were times, never predictable times but still sometimes, when you would get improbable evidence and the best knowable guess would be wrong. If you had a medical test that was only wrong one time in a thousand, sometimes it would still be wrong anyway.

"Can I ask you never to repeat what I'm about to say?" said Harry.

"Absolutely," said Professor Quirrell. "Consider me asked."

Harry wasn't a fool either. "Can I consider you to have said yes?"

"Very good, Mr. Potter. You may indeed so consider."

"Professor Quirrell -"

"I won't repeat what you're about to say," Professor Quirrell said, smiling.

They both laughed, then Harry turned serious again. "The Sorting Hat did seem to think I was going to end up as a Dark Lord unless I went to Hufflepuff," Harry said. "But I don't want to be one."

"Mr. Potter..." said Professor Quirrell. "Don't take this the wrong way. I promise you will not be graded on the answer. I only want to know your own, honest reply. Why not?"

Harry had that helpless feeling again. Thou shalt not become a Dark Lord was such an obvious theorem in his moral system that it was hard to describe the actual proof steps. "Um, people would get hurt?"

"Surely you've wanted to hurt people," said Professor Quirrell. "You wanted to hurt those bullies today. Being a Dark Lord means that people you want to hurt get hurt."

Harry floundered for words and then decided to simply go with the obvious. "First of all, just because I want to hurt someone doesn't mean it's right -"

"What makes something right, if not your wanting it?"

"Ah," Harry said, "preference utilitarianism."

"Pardon me?" said Professor Quirrell.

"It's the ethical theory that the good is what satisfies the preferences of the most people -"

"No," Professor Quirrell said. His fingers rubbed the bridge of his nose. "I don't think that's quite what I was trying to say. Mr. Potter, in the end people all do what they want to do. Sometimes people give names like 'right' to things they want to do, but how could we possibly act on anything but our own desires?"

"Well, obviously," Harry said. "I couldn't act on moral considerations if they lacked the power to move me. But that doesn't mean my wanting to hurt those Slytherins has the power to move me more than moral considerations!"