Harry Potter and the Methods of Rationality

I've been thinking about trying to get into Slytherin House myself just because I heard you were in it as a child -"

"What are you saying, Mr. Potter?" came a near-scream from outside the shop, and Professor McGonagall burst in a second later.

There was such pure horror on her face that Harry's mouth opened automatically, and then blocked on nothing-to-say.

"Professor McGonagall!" cried Draco. "Is it really you? I've heard so much about you from my father, I've been thinking of trying to get Sorted into Gryffindor so I can -"

"What?" bellowed Lucius Malfoy and Professor McGonagall in perfect unison, standing side-by-side. Their heads swivelled to look at each other in duplicate motions, and then the two recoiled from one another as though performing a synchronised dance.

There was a sudden flurry of action as Lucius seized Draco and dragged him out of the shop.

And then there was silence.

In Professor McGonagall's left hand lay a small drinking-glass, tilted over to one side in the forgotten rush, now slowly dripping drops of alcohol into the tiny puddle of red wine that had appeared on the floor.

Professor McGonagall strode forward into the shop until she was opposite Madam Malkin.

"Madam Malkin," said Professor McGonagall, her voice calm. "What has been happening here?"

Madam Malkin looked back silently for four seconds, and then cracked up. She fell against the wall, wheezing out laughter, and that set off both of her assistants, one of whom fell to her hands and knees on the floor, giggling hysterically.

Professor McGonagall slowly turned to look at Harry, her expression chilly. "I leave you alone for six minutes. Six minutes, Mr. Potter, by the very clock."

"I was only joking around," Harry protested, as the sounds of hysterical laughter went on nearby.

"Draco Malfoy said in front of his father that he wanted to be sorted into Gryffindor! Joking around isn't enough to do that!" Professor McGonagall paused, visibly taking breaths. "What part of 'get fitted for robes' sounded to you like please cast a Confundus Charm on the entire universe!"

"He was in a situational context where those actions made internal sense -"

"No. Don't explain. I don't want to know what happened in here, ever. Whatever dark power inhabits you, it is contagious, and I don't want to end up like poor Draco Malfoy, poor Madam Malkin and her two poor assistants."

Harry sighed. It was clear that Professor McGonagall wasn't in a mood to listen to reasonable explanations. He looked at Madam Malkin, who was still wheezing against the wall, and Malkin's two assistants, who had now both fallen to their knees, and finally down at his own tape-measure-draped body.

"I'm not quite done being fitted for clothes," Harry said kindly. "Why don't you go back and have another drink?"

Chapter 6: The Planning Fallacy

Blah blah disclaimer blah blah Rowling blah blah ownership.

A/N: The "Aftermath" section of this chapter is part of the story, not omake.

You think your day was surreal? Try mine.

Some children would have waited until after their first trip to Diagon Alley.

"Bag of element 79," Harry said, and withdrew his hand, empty, from the mokeskin pouch.

Most children would have at least waited to get their wands first.

"Bag of okane," said Harry. The heavy bag of gold popped up into his hand.

Harry withdrew the bag, then plunged it again into the mokeskin pouch. He took out his hand, put it back in, and said, "Bag of tokens of economic exchange." That time his hand came out empty.

"Give me back the bag that I just put in." Out came the bag of gold once more.

Harry James Potter-Evans-Verres had gotten his hands on at least one magical item. Why wait?

"Professor McGonagall," Harry said to the bemused witch strolling beside him, "can you give me two words, one word for gold, and one word for something else that isn't money, in a language that I wouldn't know? But don't tell me which is which."

"Ahava and zahav," said Professor McGonagall. "That's Hebrew, and the other word means love."

"Thank you, Professor. Bag of ahava." Empty.

"Bag of zahav." And it popped up into his hand.

"Zahav is gold?" Harry questioned, and Professor McGonagall nodded.

Harry thought over his collected experimental data. It was only the most crude and preliminary sort of effort, but it was enough to support at least one conclusion:

"Aaaaaaarrrgh this doesn't make any sense!"

The witch beside him lifted a lofty eyebrow. "Problems, Mr. Potter?"

"I just falsified every single hypothesis I had! How can it know that 'bag of 115 Galleons' is okay but not 'bag of