Harry Potter and the Methods of Rationality

Harry Potter's head appeared, floating in midair as an invisible hand drew back the hood of his invisibility cloak.

"That eye," said Harry Potter. There was a strange fierce light in the boy's eyes. "That isn't any ordinary device. It can see right through my invisibility cloak. You dodged my Transfigured taser as soon as I started raising it, even though I didn't speak any incantations. And now that I've watched it again - you spotted all my Time-Turned selves the moment you Flooed into this room, didn't you?"

Mad-Eye Moody was smiling, the same teeth-bared grin she'd seen him wear as they'd faced off against Voldemort himself. "Spend a hundred years hunting Dark wizards, and you see everything," said Moody. "I once arrested a young Japanese who tried a similar trick. He found out the hard way that his shadow replica technique was no match for this eye of mine."

"You see in all directions," Harry Potter said, that strange fierce light still in his gaze. "No matter where that eye is pointing, it sees everything around you."

Moody's tiger-grin grew wider. "There's no more of you in this room, now," Mad-Eye said. "Think that's because you'll give up after this time, or because you'll win? Any bets, boy?"

"It's my final attempt because I decided to stake my last three hours on one shot," said Harry Potter. "As for whether I win -"

There was a blur filling the whole air of the Headmaster's office. Mad-Eye Moody leapt to one side with blinding speed and an instant later Harry's head darted backward as he cried "Stuporfy!"

Three shimmers in the air went past Harry's moving head, just as a red bolt erupted from Harry's location, shooting past Moody as he dodged in yet another direction -

If she'd blinked, she would have missed it, the red bolt making an angled turn in midair and slamming into Moody's ear.

Moody fell.

Harry Potter's floating head dropped to the height of a first-year on their hands and knees, then dropped further to the ground, his face showing sudden exhaustion.

Minerva McGonagall said, "What in Merlin's name just -"

"So you went to Flitwick, then," Moody said. The retired Auror was now sitting in a chair, drinking long draughts from a restorative in a bottle he'd taken off his belt.

Harry Potter nodded, now sitting in his own chair instead of perched on an armrest. "I tried the Defense Professor first, but -" The boy grimaced. "He... wasn't available. Well, I'd decided it was worth risking five House points, and if you say a risk is worth it, you can't complain when you have to pay up. Anyway, I figured that if you had an eye that saw things other people couldn't see, then as Isaac Asimov pointed out in Second Foundation, the weapon to use is a brilliant light. Read enough science fiction, you know, and you'll read everything at least once. Anyway, I told Professor Flitwick that I needed a Charm that would make a huge number of shapes, bright and flickering and filling the whole office, but invisible, so only your eye could see them. I had no idea what it would even mean to cast an illusion and then make it invisible, but I figured if I didn't mention that out loud, Professor Flitwick would just do it anyway, and he did. Turns out there was no spell like that I could cast myself, but Flitwick Charmed me a one-time device for it - though I had to persuade him that it wasn't cheating, since nothing could possibly be cheating against an Auror who'd lived long enough to retire. And then I still didn't see how I could hit you, when you were moving that fast. So I asked about targeted spells, and that was when Flitwick showed me that hex I cast at the end, the Swerving Stunner. It's one of Professor Flitwick's own inventions - he's a champion duellist as well as a Charms Master -"

"I know that, son."

"Sorry. Anyway, the Professor says he left the duelling circuit before he got a chance to use that spell, since it only works as a finishing move on an unshielded opponent. The hex gets as close to the target as possible along its original trajectory, and then once it detects that the target is getting more distant again, the hex turns in midair and heads straight for the target. It can only swerve once - but the incantation sounds very close to 'Stupefy' and the hex is the same red color, so if the enemy thinks it's a regular Stunning Hex and tries a normal dodge, that midair retargeting will finish them off. Oh, and the Professor requested that none of us talk about his special move, just in case he does get a chance to use it during competition someday."

"But -" said Professor McGonagall. She glanced at Mad-Eye Moody, who was nodding his approval, and at Severus, who was keeping his face decidedly blank. "Mr. Potter, you just stunned Mad-Eye Moody! The most famous Dark wizard hunter in the history of the Auror Office! That should've been impossible!"

Moody let out a dark chuckle. "What's your answer to that one, kid? I'm curious."

"Well..." Harry said. "First of all, Professor McGonagall, neither of us were fighting seriously."

"Neither of you?"

"Of course," Harry said. "In a serious fight, Mr. Moody would've dropped all my copies immediately without waiting for them to attack. And on my side, if it was actually necessary to take down the most famous Auror in the history of the office, I'd get Headmaster Dumbledore to do it for me. And beyond that... since that wasn't a real fight..." Harry paused. "How can I put this? Wizards are used to duels where people fight back and forth with spells for a while. But if two Muggles with guns stand in a small room and fire bullets at each other... then whoever hits first, wins. And if one of them is deliberately missing his shots, giving the other person one chance after another - like Mr. Moody gave me one chance after another - well, you'd have to be pretty pathetic to lose."

"Oh, not that pathetic," Moody said with a slightly threatening grin.

Harry didn't seem to notice. "You might say that Mr. Moody was testing me to see if I would try to fight him, or try to win. That is, whether I'd carry out the role of somebody fighting - use standard spells I already knew, even though I didn't expect the consequences of that action to be victory - or if I'd search through unusual plans until I found something that could win. Like the difference between a student who sits in class because that's what students do, versus a student who cares enough to ask themselves what it takes to actually learn a piece of material, and practices however necessary - you see, Professor McGonagall? When you look at it that way - realize that Mr. Moody was giving me chances, and that I shouldn't attack in the first place unless I think I can win - then I don't come out looking so well, since it actually