Harry Potter and the Methods of Rationality

"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.