Eliezer Yudkowsky - Harry Potter and the Methods of Rationality

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.