Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  A sinking sensation began to dawn in Harry's stomach. "Lucius was behind Rita Skeeter...?"

  "Oh, you didn't realize that?" said Professor Quirrell.

  Harry hadn't thought about what would happen to Rita Skeeter afterward.

  At all.

  Not in the slightest.

  But she would get fired from her job, of course she would be fired, she might have children going through Hogwarts for all Harry knew, and now it was worse, much worse -

  "Is Lucius going to have her killed?" Harry said in a barely audible voice. Somewhere in his head, the Sorting Hat was screaming at him.

  Professor Quirrell smiled dryly. "If you have not dealt with journalists before, take it from me that the world gets a little brighter every time one dies."

  Harry jumped out of his chair with a convulsive movement, he had to find Rita Skeeter and warn her before it was too late -

  "Sit down," Professor Quirrell said sharply. "No, Lucius won't kill her. But Lucius makes life extremely unpleasant for those who serve him ill. Miss Skeeter will flee and start her life over with a new name. Sit down, Mr. Potter; there is nothing you can do at this point, and you have a lesson to learn."

  Harry sat down, slowly. There was a disappointed, annoyed look on Professor Quirrell's face that was doing more to stop him than the words.

  "There are times," Professor Quirrell said, his voice cutting, "when I worry that your brilliant Slytherin mind is simply wasted on you. Repeat after me. Rita Skeeter was a vile, disgusting woman."

  "Rita Skeeter was a vile, disgusting woman," Harry said. He wasn't comfortable saying it, but there didn't seem to be any other possible actions, none at all.

  "Rita Skeeter tried to destroy my reputation, but I executed an ingenious plan and destroyed her reputation first."

  "Rita Skeeter challenged me. She lost the game, and I won."

  "Rita Skeeter was an obstacle to my future plans. I had no choice but to deal with her if I wanted those plans to succeed."

  "Rita Skeeter was my enemy."

  "I cannot possibly get anything done in life if I am not willing to defeat my enemies."

  "I have defeated one of my enemies today."

  "I am a good boy."

  "I deserve a special reward."

  "Ah," said Professor Quirrell, who had been grinning a benevolent smile for the last few lines, "I see I have succeeded in catching your attention."

  That was true. And while Harry felt like he was being railroaded into something - no, that wasn't just a feeling, he had been railroaded - he couldn't deny that saying those things, and seeing Professor Quirrell's smile, did make him feel better.

  Professor Quirrell reached into his robes, the gesture slow and deliberately significant, and drew forth...

  ...a book.

  It was different from any book Harry had ever seen, the edges and corners visibly misshapen; rough-hewn was the phrase that came to mind, like it had been hacked out of a book mine.

  "What is it?" breathed Harry.

  "A diary," said Professor Quirrell.

  "Whose?"

  "That of a famous person." Professor Quirrell was smiling broadly.

  "Okay..."

  Professor Quirrell's expression became more serious. "Mr. Potter, one of the requisites for becoming a powerful wizard is an excellent memory. The key to a puzzle is often something you read twenty years ago in an old scroll, or a peculiar ring you saw on the finger of a man you met only once. I mention this to explain how I managed to remember this item, and the placard attached to it, after meeting you a good deal later. You see, Mr. Potter, over the course of my life, I have viewed a number of private collections held by individuals who are, perhaps, not quite deserving of all that they have -"

  "You stole it?" Harry said incredulously.

  "That is correct," said Professor Quirrell. "Very recently, in fact. I think you will appreciate this particular item much more than the vile little man who held it for no other purpose than impressing his equally vile friends with its rarity."

  Harry was simply gaping now.

  "But if you feel that my actions were incorrect, Mr. Potter, I suppose you needn't accept your special present. Though of course I shan't go to the trouble of stealing it back. So which is it to be?"

  Professor Quirrell tossed the book from one hand to another, causing Harry to reach out involuntarily with a look of dismay.

  "Oh," said Professor Quirrell, "don't worry about a little rough handling. You could toss this diary in a fireplace and it would emerge unscathed. In any case, I await your decision."

  Professor Quirrell casually threw the book up into the air and caught it again, grinning.

  No, said Gryffindor and Hufflepuff.

  Yes, said Ravenclaw. What part of the word 'book' did you two not understand?

  The theft part, said Hufflepuff.

  Oh, come on, said Ravenclaw, you can't seriously ask us to say no and spend the rest of our life wondering what it was.

  It sounds like a net positive from a utilitarian standpoint, said Slytherin. Think of it as an economic transaction which generates gains from trade, only without the trade part. Plus, we didn't steal it and it won't help anyone to have Professor Quirrell keep it.

  He's trying to turn you Dark! shrieked Gryffindor, and Hufflepuff nodded firmly.

  Don't be a naive little boy, said Slytherin, he's trying to teach you Slytherin.

  Yeah, said Ravenclaw. Whoever owned the book originally was probably a Death Eater or something. It belongs with us.

  Harry's mouth opened, then halted that way, an agonized look on his face.

  Professor Quirrell seemed to be quite enjoying himself. He had balanced the book on its corner, on one finger, and was keeping it upright while humming a little tune.

  There came a knock at the door.

  The book vanished back into Professor Quirrell's robes, and he rose up from his chair. Professor Quirrell started to walk over to the door -

  - and staggered, suddenly lurching into the wall.

  "It's all right," said Professor Quirrell's voice, which suddenly sounded a lot weaker than usual. "Sit down, Mr. Potter, it's just a dizzy spell. Sit down."

  Harry's fingers gripped the edge of his chair, uncertain as to what he should do, what he could do. Harry couldn't even get too close to Professor Quirrell, not unless he wanted to defy that sense of Doom -

  Professor Quirrell straightened, then, his breathing seeming a bit heavy, and opened the door.

  The waitress came in, bearing a platter of food; and as she distributed the plates, Professor Quirrell walked slowly back to the table.

  But by the time the waitress had bowed her way out, Professor Quirrell was sitting upright and smiling again.

  Still, the brief episode of whatever-it-was had decided Harry. He couldn't say no, not after Professor Quirrell had gone to that much trouble.

  "Yes," Harry said.

  Professor Quirrell held up a cautioning finger, then took out his wand again, locked the door again, and repeated three of the same Charms from earlier.

  Then Professor Quirrell took the book back out of his robes and tossed it to Harry, who almost dropped it into his soup.

  Harry shot Professor Quirrell a look of helpless indignation. You weren't supposed to do that with books, enchanted or not.

  Harry opened the book with ingrained, instinctive care. The pages seemed too thick, with a texture unlike either Muggle paper or wizarding parchment. And the contents were...

  ...blank?

  "Am I supposed to be seeing -"

  "Look nearer the beginning," said Professor Quirrell, and Harry (again with that helpless, ingrained care) turned a block of pages back.

  The lettering was obviously handwritten, and very hard to read, but Harry thought the words might be Latin.

  "What is this?" said Harry.

  "That," said Professor Quirrell, "is a record of the magical researches of a Muggleborn who never came to Hogwarts. He refused his letter,
and conducted his own small investigations, which never did get very far without a wand. From the description on the placard, I expect that his name bears rather more significance to you than to me. That, Harry Potter, is the diary of Roger Bacon."

  Harry almost fainted.

  Nestled up against the wall, where Professor Quirrell had stumbled, glistened the crushed remains of a beautiful blue beetle.

  Chapter 27: Empathy

  J. K. Rowling is 87% confident you will burst into flames.

  Roger Bacon lived in the 13th century and is credited as one of the earliest advocates of the scientific method. Giving a scientist his experimental diary is sort of like giving a writer the pen, not of Shakespeare, but of someone who helped invent writing.

  It wasn't every day you got to see Harry Potter beg.

  "Pleeaaase," whined Harry Potter.

  Fred and George shook their heads again, smiling.

  There was an agonized look on Harry Potter's face. "But I told you how I did the one with Kevin Entwhistle's cat, and Hermione and the vanishing soda, and I can't tell you about the Sorting Hat or the Remembrall or Professor Snape..."

  Fred and George shrugged and turned to leave.

  "If you ever do figure it out," said the Weasley twins, "be sure to let us know."

  "You're evil! You're both evil!"

  Fred and George firmly closed the door to the empty classroom behind them, and made sure to keep the grin on their faces for a while, just in case Harry Potter could see through doors.

  Then they turned a corner and their faces sagged.

  "I don't suppose Harry's guesses -"

  "- gave you any ideas?" they said to each other at the same time, and then their shoulders slumped further.

  Their last relevant memory was of Flume refusing to help them, though they couldn't remember what they'd asked him to do...

  ...but they must have looked elsewhere and found someone to help them do something illegal, or they wouldn't have agreed to be Obliviated afterward.

  How had they possibly been able to get all that done on just forty Galleons?

  At first they'd worried that they'd forged evidence so good that Harry actually would end up married to Ginny... but they'd thought of that too, it seemed. The Wizengamot proceedings had been tampered with again to put them back the way they'd been originally, the fake betrothal contract had vanished from its dragon-guarded vault in Gringotts, and so on. It was pretty scary, actually. Most people now thought the Daily Prophet had just made the whole thing up for unguessable reasons, and the Quibbler had helpfully twisted the knife deeper with the next day's headline, HARRY POTTER SECRETLY BETROTHED TO LUNA LOVEGOOD.

  Whoever they'd hired would tell them after the statute of limitations expired, they desperately hoped. But meanwhile it was awful, they'd pulled their greatest prank ever, maybe the greatest prank in the history of pranking, and they couldn't remember how. It was crazy, they'd been able to think of a way the first time, so why couldn't they see it now after knowing everything they'd done?

  Their only consolation was that Harry didn't know they didn't know.

  Not even Mum had questioned them about it, despite the obvious Weasley connection. Whatever had been done, it was far out of the reach of any Hogwarts student... except possibly one, who, if certain rumors were true, might have done it by snapping his fingers. Harry had been questioned under Veritaserum, he'd told them... with Dumbledore present and giving the Aurors scary looks. The Aurors had asked just enough to determine that Harry hadn't pulled the prank himself or disappeared anyone, and then gotten the heck out of Hogwarts.

  Fred and George had wondered whether to feel insulted about Harry Potter being questioned by the Aurors for their prank, but the look on Harry's face, probably for exactly the same reason, made everything worth it.

  Unsurprisingly, Rita Skeeter and the editor of the Daily Prophet had both vanished and were probably in another country by now. They would've liked to be able to tell their family about that part. Dad would have congratulated them, they thought, after Mum had finished killing them and Ginny had burned the remains.

  But everything was still all right, they'd tell Dad someday, and meanwhile...

  ...meanwhile Dumbledore had happened to sneeze while passing them in the hallway, and a small package had accidentally dropped out of his pockets, and inside had been two matched wardbreaker's monocles of incredible quality. The Weasley twins had tested their new monocles on the "forbidden" third-floor corridor, making a quick trip to the magic mirror and back, and they hadn't been able to see all the detection webs clearly, but the monocles had shown a lot more than they'd seen the first time.

  Of course they would have to be very careful never to get caught with the monocles in their possession, or they would end up in the Headmaster's office getting a stern lecture and maybe even threats of expulsion.

  It was good to know that not everyone who got Sorted into Gryffindor grew up to be Professor McGonagall.

  Harry was in a white room, windowless, featureless, sitting before a desk, facing an expressionless man in formal robes of solid black.

  The room was screened against detection, and the man had performed exactly twenty-seven spells before saying so much as "Hello, Mr. Potter."

  It was oddly appropriate that the man in black was about to try reading Harry's mind.

  "Prepare yourself," the man said tonelessly.

  A human mind, Harry's Occlumency book had said, was only exposed to a Legilimens along certain surfaces. If you failed to defend your surfaces, the Legilimens would go through and be able to access any part of you which their own mind was able to comprehend...

  ...which tended not to be much. Human minds, it seemed, were hard for humans to understand on any level but the shallowest. Harry had wondered if knowing lots of cognitive science could make him an incredibly powerful Legilimens, but repeated experience had finally driven into him the lesson that he needed to get a little less excited in his anticipations about this sort of thing. It wasn't as if any cognitive scientist understood humans well enough to make one.

  To learn the counter, Occlumency, the first step was to imagine yourself to be a different person, pretending it as thoroughly as you could, immersing yourself entirely in that alternate persona. You wouldn't always have to do that, but in the beginning, it was how you learned where your surfaces were. The Legilimens would try to read you, and you would feel it happening if you paid close enough attention, you would sense them trying to enter. And your job was to make sure that they always touched your imaginary persona and not the real one.

  When you were good enough at that, you could imagine being a very simple sort of person, pretend to be a rock, and make a habit of leaving the pretense in place where all your surfaces were. That was a standard Occlumency barrier. Pretending to be a rock was hard to learn, but easy to do afterward, and the exposed surface of a mind was much shallower than its interior, so with enough practice you could keep it up as a background habit.

  Or if you were a perfect Occlumens, you could race ahead of any probes, answering queries as fast as they were asked, so that the Legilimens would enter through your surfaces and see a mind indistinguishable from whoever you were pretending to be.

  Even the best Legilimens could be fooled that way. If a perfect Occlumens claimed they were dropping their Occlumency barriers, there was no way to know if they were lying. Worse, you might not know you were dealing with a perfect Occlumens. They were rare, but the fact that they existed meant you couldn't trust Legilimency on anyone.

  It was a sad commentary on how little human beings understood each other, how little any wizard comprehended the depths lying beneath the mind's surface, that you could fool the best human telepaths by pretending to be someone else.

  But then human beings only understood each other in the first place by pretending. You didn't make predictions about people by modeling the hundred trillion synapses in their brain as separate objects. Ask the best social manipulator o
n Earth to build you an Artificial Intelligence from scratch, and they'd just give you a dumb look. You predicted people by telling your brain to act like theirs. You put yourself in their place. If you wanted to know what an angry person would do, you activated your own brain's anger circuitry, and whatever that circuitry output, that was your prediction. What did the neural circuitry for anger actually look like inside? Who knew? The best social manipulator on Earth might not know what neurons were, and neither might the best Legilimens.

  Anything a Legilimens could understand, an Occlumens could pretend to be. It was the same trick either way - probably implemented by the same neural circuitry in both cases, a single set of control circuits for reconfiguring your own brain to act as a model of someone else's.

  And so the race between telepathic offense and telepathic defense had been a decisive win for defense. Otherwise the entire magical world, maybe even the whole Earth, would have been a very different place...

  Harry took a deep breath, and concentrated. There was a slight smile on his face.

  For once, just once, Harry hadn't gotten shortchanged in the mysterious powers department.

  After almost a month of work, and more on a whim than any real hunch, Harry had decided to make himself coldly angry and then try the book's Occlumency exercises again. At that point he'd mostly given up hope on that sort of thing, but it had still seemed worth a quick try -

  He'd run through all the book's hardest exercises in two hours, and the next day he'd gone and told Professor Quirrell he was ready.

  His dark side, it had turned out, was very, very good at pretending to be other people.

  Harry thought of his standard trigger, from the first time he'd gone over entirely to his dark side...

  Severus paused, looking quite pleased with himself. "And that will be... five points? No, let us make it an even ten points from Ravenclaw for backchat."