Harry Potter and the Methods of Rationality

'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!'

Professor Quirrell blinked.

'Not to mention,' Harry said, 'being a Dark Lord would mean that a lot of innocent bystanders got hurt too!'

'Why does that matter to you?' Professor Quirrell said. 'What have they done for you?'

Harry laughed. 'Oh, now that was around as subtle as Atlas Shrugged.'

'Pardon me?' Professor Quirrell said again.

'It's a book that my parents wouldn't let me read because they thought it would corrupt me, so of course I read it anyway and I was offended they thought I would fall for any traps that obvious. Blah blah blah, appeal to my sense of superiority, other people are trying to keep me down, blah blah blah.'

'So you're saying I need to make my traps less obvious?' said Professor Quirrell. He tapped a finger on his cheek, looking thoughtful. 'I can work on that.'

They both laughed.

'But to stay with the current question,' said Professor Quirrell, 'what have all these other people done for you?'

'Other people have done huge amounts for me!' Harry said. 'My parents took me in when my parents died because they were good people, and to become a Dark Lord is to betray that!'

Professor Quirrell was silent for a time.

'I confess,' said Professor Quirrell quietly, 'when I was your age, that thought could not ever have come to me.'

'I'm sorry,' Harry said.

'Don't be,' said Professor Quirrell. 'It was long ago, and I resolved my parental issues to my own satisfaction. So you are held back by the thought of your parents' disapproval? Does that mean that if they died in an accident, there would be nothing left to stop you from -'