Harry Potter and the Methods of Rationality

'Just spin back around and go left, right, down, down, right, left, right, up, and left again, you'll be at the green study room and if you go in and walk straight out the opposite side you'll be on a big curvy corridor that goes to an intersection and on the right side of that intersection will be a long straight hallway that goes to the Transfiguration classroom!' The figure of the middle-aged man paused. 'At least that's how it was when I was in Hogwarts. This is a Monday on an odd-numbered year, isn't it?'

'Pencil and mechanical paper,' Harry said to his pouch. 'Er, cancel that, paper and mechanical pencil.' He looked up. 'Could you repeat that?'

After getting lost another two times, Harry felt that he was beginning to understand the basic rule for navigating the ever-changing maze that was Hogwarts, namely, ask a painting for directions. If this reflected some sort of incredibly deep life lesson he couldn't figure out what it was.

The green study room was a surprisingly pleasant space with sunlight streaming in from windows of green- stained glass that showed dragons in calm, pastoral scenes. It had chairs that looked extremely comfortable, and tables that seemed very well-suited to studying in the company of one to three friends.

Harry couldn't actually walk straight through and out the door on the other side. There were bookshelves set into the wall, and he had to go over and read some of the titles, so as to not lose his claim to the Verres family name. But he did it quickly, mindful of the complaint about being slow, and then went out the other side.

He was walking down the 'big curvy corridor' when he heard a young boy's voice cry out.

At times like this, Harry had an excuse to sprint all-out with no regards for saving energy or doing proper warmup exercises or worrying about crashing into things, a sudden frantic flight that nearly came to an equally sudden halt as he almost ran over a group of six first-year Hufflepuffs...

...who were huddled together, looking rather scared and like they desperately wanted to do something but couldn't figure out what, which probably had something to do with the group of five older Slytherins who seemed to be surrounding another young boy.

Harry was suddenly rather angry.

'Excuse me!' shouted Harry at the top of his lungs.

It might not have been necessary. People were already looking at him. But it certainly served to stop all the action cold.

Harry walked past the cluster of Hufflepuffs towards the Slytherins.

They looked down at him with expressions that ranged from anger to amusement to delight.

Part of Harry's brain was screaming in panic that these were much older and bigger boys who could stomp him flat.

Another part said dryly that anyone caught seriously stomping the Boy-Who-Lived was in for a whole world of trouble, especially if they were a pack of older Slytherins and there were seven Hufflepuffs who saw it, and that the chance of them doing him any permanent damage in the presence of witnesses was nearly zero. The only real weapon the older boys had against him was his own fear, if he allowed that.

Then Harry saw that the boy they had trapped was Neville Longbottom.

Of course.

That settled it. Harry had decided to apologise humbly to Neville and that meant Neville was his, how dare they?

Harry reached out and grabbed Neville by the wrist and yanked him out from between the Slytherins, the boy stumbling in shock as Harry pulled him out and in nearly the same motion pushed his own way through the same gap.

And Harry stood in the center of the Slytherins where Neville had stood, looking up at the much older, larger, and stronger boys.

'Hello,' Harry said. 'I'm the Boy-Who-Lived.'

There was a rather awkward pause. No one seemed to know where the conversation was supposed to go from there.

Harry's eyes dropped downwards and saw some books and papers scattered around the floor. Oh, the old game where you let the boy try to pick up his books and then knock them out of his hand again. Harry couldn't remember ever being the object of that game himself, but he had a good imagination and his imagination was making him furious. Well, once the larger situation was resolved it would be easy enough for Neville to come back and pick up his materials, provided that the Slytherins stayed too intent on him to think of doing anything to the books.

Unfortunately his straying eyes had been noted. 'Ooh,' said the largest of the boys, 'did 'oo want the widdle books -'

'Shut up,' Harry said coldly. Keep them off balance. Don't do what they expect. Don't fall into a pattern that calls for them to bully you. 'Is this part of some incredibly clever plan that will gain you future advantage, or is it as pointless a disgrace to the name of Salazar Slytherin as it -'

The largest boy shoved Harry Potter hard, and he went sprawling out of the circle of Slytherins onto the hard stone floor of Hogwarts.

And the Slytherins laughed.

Harry rose up in what seemed to him like terribly slow motion. He didn't know yet how to use his wand, but there was no reason to let that stop him, under the circumstances.

'I'd like to pay as many points as it takes to get rid of this person,' Harry said, pointing with his finger to the largest Slytherin.

Then Harry lifted his other hand, said 'Abracadabra,' and snapped his fingers.

At the word Abracadabra two of the Hufflepuffs screamed, including Neville, three other Slytherins leapt desperately out of the way of Harry's finger, and the largest Slytherin staggered back with an