Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  "We're outside the wards, Mr. Potter," said Professor Quirrell's voice from the front. "Time to go."

  Professor Quirrell carefully disembarked from the carriage, bracing himself as he stepped down. Harry, on his own side, jumped off.

  Harry was wondering exactly how they'd get there when Professor Quirrell said "Catch!" and threw a bronze Knut at him, and Harry caught it without thinking.

  A giant intangible hook caught at Harry's abdomen and yanked him back, hard, only without any sense of acceleration, and an instant later Harry was standing in the middle of Diagon Alley.

  (Excuse me, what? said his brain.)

  (We just teleported, explained Harry.)

  (That didn't used to happen in the ancestral environment, Harry's brain complained, and disoriented him.)

  Harry staggered as his feet adjusted to the brick of the street instead of the dirt of the forest corridor they had been traversing. He straightened, still dizzy, with the bustling witches and wizards seeming to sway slightly, and the cries of the shopkeepers seeming to move around in his hearing, as his brain tried to place a world to be located in.

  Moments later, there was a sort of sucking-popping sound from a few paces behind Harry, and when Harry turned to look Professor Quirrell was there.

  "Do you mind -" said Harry, at the same time as Professor Quirrell said, "I'm afraid I -"

  Harry stopped, Professor Quirrell didn't.

  "- need to go off and set something in motion, Mr. Potter. As it has been thoroughly explained to me that I am responsible for anything whatsoever that happens to you, I'll be leaving you with -"

  "Newsstand," Harry said.

  "Pardon?"

  "Or anywhere I can buy a copy of the Daily Prophet. Put me there and I'll be happy."

  Shortly after, Harry had been delivered into a bookstore, accompanied by several quietly spoken, ambiguous threats. And the shopkeeper had gotten less ambiguous threats, judging by the way he had cringed, and how his eyes now kept darting between Harry and the entrance.

  If the bookstore burned down, Harry was going to stick around in the middle of the fire until Professor Quirrell got back.

  Meanwhile -

  Harry took a quick glance around.

  The bookstore seemed rather small and shoddy, with only four rows of bookcases visible, and the nearest shelf Harry's eyes had jumped to seemed to deal with narrow, cheaply bound books with grim titles like The Massacre of Albania in the Fifteenth Century.

  First things first. Harry stepped over to the seller's counter.

  "Pardon me," said Harry, "One copy of the Daily Prophet, please."

  "Five Sickles," said the shopkeeper. "Sorry, kid, I've only got three left."

  Five Sickles dropped onto the counter. Harry had the feeling he could have bargained him down a couple of points, but at this point he didn't really care.

  The shopkeeper's eyes widened and he seemed to really notice Harry for the first time. "You!"

  "Me!"

  "Is it true? Are you really -"

  "Shut up! Sorry, I've been waiting all day to read this in the original newspaper instead of hearing about it secondhand, so please just hand it over, all right?"

  The shopkeeper stared at Harry for a moment, then wordlessly reached under the counter and passed over one folded copy of the Daily Prophet.

  The headline read:

  HARRY POTTER

  SECRETLY BETROTHED

  TO GINEVRA WEASLEY

  Harry stared.

  He lifted the newspaper off the counter, softly, reverently, like he was handling an original Escher artwork, and unbent it to read...

  ...about the evidence that had convinced Rita Skeeter.

  ...and some interesting further details.

  ...and yet more evidence.

  Fred and George had cleared it with their sister first, surely? Yes, of course they had. There was a picture of Ginevra Weasley sighing longingly over what Harry could see, looking closely, was a photo of himself. That had to have been staged.

  But how on Earth...?

  Harry was sitting in a cheap folding chair, rereading the newspaper for the fourth time, when the door whispered softly and Professor Quirrell came back into the shop.

  "My apologies for - what in Merlin's name are you reading?"

  "It would seem," said Harry, awe in his voice, "that one Mr. Arthur Weasley was placed under the Imperius Curse by a Death Eater whom my father killed, thus creating a debt to House Potter, which my father demanded be repaid by the hand in marriage of the recently born Ginevra Weasley. Do people actually do that sort of thing around here?"

  "How could Miss Skeeter possibly be fool enough to believe -"

  And Professor Quirrell's voice cut off.

  Harry had been reading the newspaper held vertically and unfolded, which meant that Professor Quirrell, from where he was standing, could see the text underneath the headline.

  The look of shock on Professor Quirrell's face was a work of art almost on par with the newspaper itself.

  "Don't worry," said Harry cheerfully, "it's all fake."

  From elsewhere in the store, he heard the shopkeeper gasp. There was the sound of a stack of books falling over.

  "Mr. Potter..." Professor Quirrell said slowly, "are you sure of that?"

  "Quite sure. Shall we go?"

  Professor Quirrell nodded, looking rather abstracted, and Harry folded the newspaper back up, and followed him out of the door.

  For some reason Harry didn't seem to be hearing any street noises now.

  They walked in silence for thirty seconds before Professor Quirrell spoke. "Miss Skeeter viewed the original proceedings of the restricted Wizengamot session."

  "Yes."

  "The original proceedings of the Wizengamot."

  "Yes."

  "I would have trouble doing that."

  "Really?" said Harry. "Because if my suspicions are correct, this was done by a Hogwarts student."

  "That is beyond impossible," Professor Quirrell said flatly. "Mr. Potter... I regret to say that this young lady expects to marry you."

  "But that is improbable," said Harry. "To quote Douglas Adams, the impossible often has a kind of integrity which the merely improbable lacks."

  "I see your point," Professor Quirrell said slowly. "But... no, Mr. Potter. It may be impossible, but I can imagine tampering with the Wizengamot proceedings. It is unimaginable that the Grand Manager of Gringotts should affix the seal of his office in witness to a false betrothal contract, and Miss Skeeter personally verified that seal."

  "Indeed," said Harry, "you would expect the Grand Manager of Gringotts to get involved with that much money changing hands. It seems Mr. Weasley was greatly in debt, and so demanded an additional payment of ten thousand Galleons -"

  "Ten thousand Galleons for a Weasley? You could buy the daughter of a Noble House for that!"

  "Excuse me," Harry said. "I really have to ask at this point, do people actually do that sort of thing around here -"

  "Rarely," said Professor Quirrell, with a frown on his face. "And not at all, I suspect, since the Dark Lord departed. I suppose that according to the newspaper, your father just paid it?"

  "He didn't have any choice," said Harry. "Not if he wanted to fulfill the conditions of the prophecy."

  "Give me that," said Professor Quirrell, and the newspaper leaped out of Harry's hand so fast that he got a paper cut.

  Harry automatically put the finger in his mouth to suck on, feeling rather shocked, and turned to remonstrate with Professor Quirrell -

  Professor Quirrell had stopped short in the middle of the street, and his eyes were flickering rapidly back and forth as an invisible force held the newspaper suspended before him.

  Harry watched, gaping in open awe, as the newspaper opened to reveal pages two and three. And not much long after, four and five. It was like the man had cast off a pretense of mortality.

  And after a troublingly short time, the paper neatly folded itself up
again. Professor Quirrell plucked it from the air and tossed it to Harry, who caught it in sheer reflex; and then Professor Quirrell started walking again, and Harry automatically trudged after.

  "No," said Professor Quirrell, "that prophecy didn't sound quite right to me either."

  Harry nodded, still stunned.

  "The centaurs could have been put under an Imperius," Professor Quirrell said, frowning, "that seems understandable. What magic can make, magic can corrupt, and it is not unthinkable that the Great Seal of Gringotts could be twisted to another's hand. The Unspeakable could have been impersonated with Polyjuice, likewise the Bavarian seer. And with enough effort it might be possible to tamper with the proceedings of the Wizengamot. Do you have any idea how that was done?"

  "I do not have one single plausible hypothesis," said Harry. "I do know it was done on a total budget of forty Galleons."

  Professor Quirrell stopped short and whirled on Harry. His expression was now completely incredulous. "Forty Galleons will pay a competent ward-breaker to open a path into a home you wish to burglarize! Forty thousand Galleons might pay a team of the greatest professional criminals in the world to tamper with the proceedings of the Wizengamot!"

  Harry shrugged helplessly. "I'll remember that the next time I want to save thirty-nine thousand, nine hundred and sixty Galleons by finding the right contractor."

  "I do not say this often," said Professor Quirrell. "I am impressed."

  "Likewise," said Harry.

  "And who is this incredible Hogwarts student?"

  "I'm afraid I couldn't say."

  Somewhat to Harry's surprise, Professor Quirrell made no objection to this.

  They walked in the direction of the Gringotts building, thinking, for they were neither of them the sort of person who would give up on the problem without considering it for at least five minutes.

  "I have a feeling," Harry said finally, "that we're coming at this from the wrong angle. There's a tale I once heard about some students who came into a physics class, and the teacher showed them a large metal plate near a fire. She ordered them to feel the metal plate, and they felt that the metal nearer the fire was cooler, and the metal further away was warmer. And she said, write down your guess for why this happens. So some students wrote down 'because of how the metal conducts heat', and some students wrote down 'because of how the air moves', and no one said 'this just seems impossible', and the real answer was that before the students came into the room, the teacher turned the plate around."

  "Interesting," said Professor Quirrell. "That does sound similar. Is there a moral?"

  "That your strength as a rationalist is your ability to be more confused by fiction than by reality," said Harry. "If you're equally good at explaining any outcome, you have zero knowledge. The students thought they could use words like 'because of heat conduction' to explain anything, even a metal plate being cooler on the side nearer the fire. So they didn't notice how confused they were, and that meant they couldn't be more confused by falsehood than by truth. If you tell me that the centaurs were under the Imperius Curse, I still have the feeling of something being not quite right. I notice that I'm still confused even after hearing your explanation."

  "Hm," said Professor Quirrell.

  They walked on further.

  "I don't suppose," said Harry, "that it's possible to actually swap people into alternate universes? Like, this isn't our own Rita Skeeter, or they temporarily sent her somewhere else?"

  "If that was possible," Professor Quirrell said, his voice rather dry, "would I still be here?"

  And just as they were almost to the huge white front of the Gringotts building, Professor Quirrell said:

  "Ah. Of course. I see it now. Let me guess, the Weasley twins?"

  "What?" said Harry, his voice going up another octave in pitch. "How?"

  "I'm afraid I couldn't say."

  "...That is not fair."

  "I think it is extremely fair," said Professor Quirrell, and they entered through the bronze doors.

  The time was just before noon, and Harry and Professor Quirrell were seated at the foot and head of a wide, long, flat table, in a sumptuously appointed private room with thoroughly cushioned couches and chairs along the walls, and soft curtains hanging everywhere.

  They were about to eat lunch in Mary's Place, which Professor Quirrell had said was known to him as one of the best restaurants in Diagon Alley, especially for - his voice had dropped meaningfully - certain purposes.

  It was the nicest restaurant that Harry had ever been in, and it was really eating away at Harry that Professor Quirrell was treating him to the meal.

  The first part of the mission, to find an Occlumency instructor, had been a success. Professor Quirrell, smiling evilly, had told Griphook to recommend the best he knew, and not worry about the expense, since Dumbledore was paying it; and the goblin had smiled in return. There might have been a certain amount of smiling on Harry's part as well.

  The second part of the plan had been a complete failure.

  Harry was not allowed to take money out of his vault without Headmaster Dumbledore or some other school official present, and Professor Quirrell had not been given the vault key. Harry's Muggle parents could not authorize it because they were Muggles, and Muggles had around the same legal standing as children or kittens: they were cute, so if you tortured them in public you could get arrested, but they weren't people. Some reluctant provision had been made for recognizing the parents of Muggleborns as human in a limited sense, but Harry's adoptive parents did not fall into that legal category.

  It seemed that Harry was effectively an orphan in the eyes of the wizarding world. As such, the Headmaster of Hogwarts, or his designees within the school system, were Harry's guardians until he graduated. Harry could breathe without Dumbledore's permission, but only so long as the Headmaster did not specifically prohibit it.

  Harry had then asked if he could simply tell Griphook how to diversify his investments beyond stacks of gold coins sitting in his vault.

  Griphook had stared blankly and asked what 'diversify' meant.

  Banks, it seemed, did not make investments. Banks stored your gold coins in secure vaults for an annual fee.

  The wizarding world did not have a concept of stock. Or equity. Or corporations. Businesses were run by families out of their personal vaults.

  Loans were made by rich people, not banks. Though Gringotts would witness the contract, for a fee, and enforce its collection, for a much larger fee.

  Good rich people let their friends borrow money and pay it back whenever. Bad rich people charged you interest.

  There was no secondary market in loans.

  Evil rich people charged you annual interest rates of at least 20%.

  Harry had stood up, turned away, and rested his head against the wall.

  Harry had asked if he needed the Headmaster's permission before he could start a bank.

  Professor Quirrell had interrupted at this point, saying that it was time for lunch, and swiftly conducted a fuming Harry out of the bronze doors of Gringotts, through Diagon Alley, and to a fine restaurant called Mary's Place, where a room had been reserved for them. The owner had looked shocked at seeing Professor Quirrell accompanied by Harry Potter, but had conducted them to the room without complaint.

  And Professor Quirrell had quite deliberately announced that he would pay the bill, seeming to rather enjoy the look on Harry's face.

  "No," said Professor Quirrell to the waitress, "we will not require menus. I will have the daily special accompanied by a bottle of Chianti, and Mr. Potter will have the Diracawl soup to start, followed by a plate of Roopo balls, and treacle pudding for dessert."

  The waitress, clad in robes that still looked severe and formal while being rather shorter than usual, bowed respectfully and departed, shutting the door behind her.

  Professor Quirrell waved a hand in the direction of the door, and a bolt slid shut. "Note the bolt on the inside. This room, Mr. Potter,
is known as Mary's Room. It happens to be proof against all scrying, and I do mean all; Dumbledore himself could detect nothing of what happens here. Mary's Room is used by two kinds of people. The first sort are engaged in illicit dalliances. And the second sort lead interesting lives."

  "Really," said Harry.

  Professor Quirrell nodded.

  Harry's lips were parted in anticipation. "It would be a waste to just sit here and eat lunch, then, without doing anything special."

  Professor Quirrell grinned, then took out his wand and flicked it in the direction of the door. "Of course," he said, "people who lead interesting lives take precautions more thorough than the dalliers. I have just sealed us in. Nothing will now pass in or out of this room - through the crack under the door, for example. And..."

  Professor Quirrell then spoke no fewer than four different Charms, none of which Harry recognized.

  "Even that does not really suffice," said Professor Quirrell. "If we were doing anything of truly great import, it would be necessary to perform another twenty-three checks besides those. If, say, Rita Skeeter knew or guessed that we would come here, it is possible that she could be in this room wearing the true Cloak of Invisibility. Or she could be an Animagus with a tiny form, perhaps. There are tests to rule out such rare possibilities, but to perform all of them would be arduous. Still, I wonder if I should do them anyway, just so as not to teach you bad habits?" And Professor Quirrell tapped a finger on his cheek, looking abstracted.

  "It's fine," Harry said, "I understand, and I'll remember." Though he was a little disappointed that they weren't doing anything of truly great import.

  "Very well," Professor Quirrell said. He leaned back in his chair, smiling broadly. "You wrought quite well today, Mr. Potter. The basic notion was yours, I'm sure, even if you delegated the execution. I don't think we'll be hearing much more from Rita Skeeter after this. Lucius Malfoy will not be pleased with her failure. If she's smart, she'll flee the country the instant she realizes she's been fooled."