Harry Potter and the Methods of Rationality

Hermione reached into the pouch Harry had bought her, whispered "water" through her parched throat, took out the bottle and drank in great huge gulps.

And then it was still a while before she could talk again.

"We broke the rules, Harry," she said in a hoarse voice. "We broke the rules."

"I..." Harry swallowed. "I still don't see how, I've been thinking but -"

"I asked if the Transfiguration was safe and you answered me!"

There was a pause.

"That's it?" Harry said.

She could have screamed.

"Harry, don't you get it?" she said. "It's made out of tiny fibers, what if it unraveled, who knows what could go wrong, we didn't ask Professor McGonagall! Don't you see what we were doing? We were experimenting with Transfiguration. We were experimenting with Transfiguration!"

There was another pause.

"Right..." Harry said slowly. "That's probably one of those things they don't even bother telling you not to do because it's too obvious. Don't test brilliant new ideas for Transfiguration by yourselves in an unused classroom without consulting any professors."

"You could have gotten us killed, Harry!" Hermione knew it wasn't fair, she'd made the mistake too, but she still felt angry at him, he always sounded so confident and that had dragged her unthinkingly along in his wake. "We could have spoiled Professor McGonagall's perfect record!"

"Yes," said Harry, "let's not tell her about this, shall we?"

"We have to stop," Hermione said. "We have to stop this or we're going to get hurt. We're too young, Harry, we can't do this, not yet."

A weak grin crossed Harry's face. "Um, you're sort of wrong about that."

And he held out a small pink rectangle, a rubber eraser with a bright metal patch on it.

Hermione stared at it, puzzled.

"Quantum mechanics wasn't enough," Harry said. "I had to go all the way down to timeless physics before it took. Had to see the wand as enforcing a relation between separate past and future realities, instead of changing anything over time - but I did it, Hermione, I saw past the illusion of objects, and I bet there's not a single other wizard in the world who could have. Even if some Muggleborn knew about timeless formulations of quantum mechanics, it would just be a weird belief about strange distant quantum stuff, they wouldn't see that it was reality, accept that the world they knew was just a hallucination. I Transfigured part of the eraser without changing the whole thing."

Hermione raised her wand again, pointed it at the eraser.

For a moment anger crossed Harry's face, but he didn't make any move to stop her.

"Finite Incantatem," said Hermione. "Check with Professor McGonagall before you try it again."

Harry nodded, though his face was still a bit tight.

"And we still have to stop," said Hermione.

"Why?" said Harry. "Don't you see what this means, Hermione? Wizards don't know everything! There's too few of them, even fewer who know any science, they haven't exhausted the low-hanging fruit -"

"It's not safe," Hermione said. "If we can find out new things it's even less safe! We're too young! We made one big mistake already, next time we could just die!"

Then Hermione flinched.

Harry looked away from her, and started taking slow, deep breaths.

"Please don't try to do it alone, Harry," Hermione said, her voice trembling. "Please."

Please don't make me have to decide whether to tell Professor Flitwick.

There was a long pause.

"So you want us to study," Harry said. She could tell he was trying to keep the anger out of his voice. "Just study."

Hermione wasn't sure if she should say anything, but... "Like you studied, um, timeless physics, right?"

Harry looked back at her.

"That thing you did," Hermione said, her voice tentative, "it wasn't because of our experiments, right? You could do it because you'd read lots of books."

Harry opened his mouth, and then he shut it again. There was a frustrated look on his face.

"All right," Harry said. "How about this. We study, and if I think of anything that seems really worth trying, we'll try it after I ask a professor."

"Okay," Hermione said. She didn't fall over with relief, but only because she was already sitting down.