Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  By the second line the others had joined in, and soon you could hear the same soft chant coming from nearby parts of the forest.

  And Neville marched alongside his fellow Chaos Legionnaires,

  strange feelings stirring in his heart,

  imagination becoming reality,

  as from his lips poured a fearful song of doom.

  Harry stared at the bodies scattered across the forest. Something inside him felt a bit queasy, and he had to remind himself hard that they were only sleeping. There were girls among the fallen, and that made it a lot worse somehow, and he would have to be careful never to mention that in front of Hermione or the Aurors would find his remains stuffed into a small teapot.

  Half of Sunshine army hadn't put up much of a fight against all of Chaos. The nine ground soldiers had run in screaming inarticulately with Simple Shields raised, circular screens to protect their faces and chests. But you couldn't fire and hold the shield at the same time, and Harry's soldiers had simply aimed for the legs. All but one of the Sunnies had fallen over as soon as the cries of "Somnium!" filled the air. That last one had dropped her shield and managed to take out one of Harry's soldiers before being hit by the second wave of sleep spells (the Sleep Hex was safe for multiple hits). The two Sunny broomsticks had been much harder to take down and had accounted for three Chaotics before being auraed by massed ground fire.

  Hermione wasn't among the fallen. Draco must have gotten her and that was making Harry feel angry on some completely incomprehensible level, he wasn't sure if he was feeling protective toward Hermione, or cheated that he hadn't been the one to do it, or maybe both.

  "All right," Harry said, raising his voice. "Let's everyone be clear on one thing, that wasn't a real fight. That was General Granger making a mistake in her first battle. Today's actual fight is with Dragon Army and it's not going to be anything like this. It's going to be a lot more fun. Let's move out."

  A broomstick fell out of the sky, approaching terrifyingly fast, and spun on its end and decelerated so hard you could almost hear the air screaming in protest, and came to a halt directly beside Draco.

  It wasn't dangerous showing-off. Gregory Goyle simply was that good and he didn't waste time.

  "Potter's coming," Gregory said with no trace of his usual fake drawl. "They've still got all four of their brooms, you want me to take them out?"

  "No," Draco said sharply. "Fighting over their army gives them too much of an advantage, they'll fire on you from the ground and even you might not be able to dodge it all. Wait until the forces engage."

  Draco had lost four Dragons in exchange for twelve Sunnies. Apparently General Granger actually had been that incredibly stupid, though she hadn't been among the attackers, so Draco hadn't gotten a chance to taunt her or ask her what in Merlin's name she had been thinking.

  The true battle, they all knew, would be with Harry Potter.

  "Prepare yourselves!" roared Draco at his troops. "Stay together with your mates, act as a unit, fire as soon as the enemy is in range!"

  Discipline against Chaos.

  It shouldn't be much of a fight.

  The adrenaline was pumping and pumping into Neville's blood until he felt like he could hardly breathe.

  "We're closing in," said General Potter in a voice barely loud enough to carry to the whole army. "Time to spread out."

  Neville's comrades moved away from him. They would still support each other, but if you clustered together, the enemy would have a much easier time hitting you; fire aimed at one of your comrades might miss and get you instead. You would be a lot harder to hit if you spread out and moved as fast as you could.

  The first thing General Potter had done, during their training session, was get them to fire on each other when both sides were running fast, or both stood still and took time to aim, or one was moving and one was standing still - the reverse charm to the Sleep Hex was simple, though you weren't allowed to use it during real battles. General Potter had carefully recorded everything that happened, done some figuring and ciphering, and then announced that it made more sense for them to focus, not on slowing down to aim carefully, but on moving fast so they wouldn't get hit.

  It still bothered Neville a little not to be marching side-by-side with his comrades, but the scary battlecries they'd learned were already thundering in his head and that made up for a lot.

  This time, Neville silently vowed to himself, his voice was absolutely positively not going to squeak.

  "Shields up," said General Potter, "power to forward deflectors."

  "Contego," murmured the army, and the circular screens sprang into existence before their heads and chests.

  A sharp taste filled Neville's mouth. General Potter wouldn't have ordered them to cast shields unless they were almost in range. Neville could see the uniformed shapes of Dragons moving through the dense screens of trees, and the Dragons would be seeing them as well -

  "Attack!" came a cry from the distance, the voice of Draco Malfoy, and General Potter bellowed, "Charge -"

  All the adrenaline in Neville's blood was unleashed, and his legs took over, sending him flying faster than he'd ever run before, straight toward the enemy, knowing without needing to look that all his comrades were doing the same.

  "Blood for the blood god!" screamed Neville. "Skulls for the skull throne! Ia! Shub-Niggurath! The enemy's gate is sideways!"

  There was a soundless impact as a sleep spell wasted itself against Neville's shield. If there'd been other spells fired, they hadn't hit.

  Neville saw the brief look of fear on Wayne Hopkins's face, as he stood besides two Gryffindors Neville didn't recognize, and then -

  - Neville dropped the Simple Shield and fired at Wayne -

  - missed -

  - his racing legs went straight past the enemy grouping and toward another three Dragons, their wands coming up on him, their mouths opening -

  - not even thinking about it, Neville dived down to the forest floor just as three voices cried "Somnium!"

  It hurt, hard stones and hard twigs digging into Neville as he rolled, it wasn't as bad as falling off his broomstick but he'd still hit the ground pretty hard, and then Neville, with sudden insight, lay still and closed his eyes.

  "Stop that!" screamed a voice. "Don't shoot us, we're Dragons!"

  With a flash of glorious satisfaction, Neville realized that he'd managed to get between two groups of Dragons just as one group had fired on him. Harry had talked about this as a tactic for making the enemy afraid to fire, but apparently it worked a bit better than that.

  And not only that, the Dragons believed they'd gotten him, since they'd seen Neville fall just as they fired.

  Neville counted to twenty inside his head, then opened his eyes a crack.

  The three Dragons were very near him, heads spinning rapidly as cries of "Somnium!" and "Skulls for the skull throne!" filled the air around them. All three had Simple Shields up now.

  Neville's wand was still in his hand, and it didn't take much effort to point it at one boy's boots and whisper "Somnium."

  Neville quickly closed his eyes and relaxed his hand as he heard the boy fall to the ground.

  "Where'd it come from?" screamed Justin Finch-Fletchley's voice, and Neville heard rustles on the leafy forest floor, as of two Dragons spinning around looking for an enemy.

  "Reform ranks!" bellowed Malfoy's voice. "To me, everyone, don't let them scatter you!"

  Neville's ears heard the two Dragons actually jump over his prone body as they ran off.

  Neville opened his eyes, pushed himself to his feet a bit painfully, and then pointed his wand and said the new charm that General Potter had taught them all. They couldn't do real illusion spells to confuse the enemy, but even at their age they could -

  "Ventriliquo," whispered Neville, pointing the wand to one side of Justin and the other boy, and then yelled, "For Cthulhu and glory!"

  Justin and the other boy stopped abruptly, turning their shields toward wher
e Neville had moved his battlecry, and that was when multiple cries of "Somnium!" filled the air and the other boy dropped before Neville was finished aiming.

  "The last one's mine!" yelled Neville, and then he started sprinting straight toward Justin, who'd been mean to him until the older Hufflepuffs straightened him out. Neville was surrounded by his comrades and that meant -

  "Special attack, Chaotic Leap!" howled Neville as he ran, and felt his body lighten, then lighten twice again, as his comrades got their wands turned toward him and quietly cast the Hover Charm, and Neville raised his left hand and snapped his fingers and then used his legs to push off the ground as hard as he could and soared through the air. Sheer shock painted Justin's face as Neville went over the other boy's shield and pointed his wand down at the form passing beneath him and cried "Somnium!"

  Because he'd felt like it, that was why.

  Neville didn't quite get his feet turned around properly and rather plowed into the ground as he landed, but two out of three of the other Chaos Legionnaires had managed to hold their wands on him throughout and he didn't hit very hard.

  And Neville got to his feet, panting. He knew he should be moving, people were yelling "Somnium!" all over the place -

  "I am Neville, the last scion of Longbottom!" screamed Neville to the sky above, holding his wand pointed straight up as though to challenge the blazing blue heaven itself, knowing that nothing after this day would ever be the same again. "Neville of Chaos! Face me if you da-"

  (When Neville woke up afterward, he was told that Dragon Army had taken this as their cue to counterattack.)

  The girl beside Harry slumped to the ground, taking the shot meant for him, and he could hear Mr. Goyle's distant gloating laugh as his broomstick blasted past them, cutting the air so hard it should have shattered in his wake.

  "Luminos!" cried one of the boys next to Harry, who hadn't been able to rebuild the magical strength fast enough to do it earlier, and Mr. Goyle dodged it without a pause.

  Chaos had only six soldiers left, now, and Dragon Army had two, and the only problem was that one of those soldiers was invincible, and the other one was using up three soldiers just to cover him inside his shield.

  They'd lost more soldiers to Mr. Goyle than all the other Dragons put together, he was weaving and dodging through the air so fast that no one could hit him, and he could shoot people while he did that.

  Harry had thought of all sorts of ways to stop Mr. Goyle but none of them were safe, even using the Hover Charm to slow him down (it was a continuous beam and much easier to aim) wouldn't be safe because he might fall off the broomstick, throwing things in his way wouldn't be safe, and that was getting harder and harder to remember as Harry's blood froze over.

  It's a game. You're not trying to kill him. Don't throw away all your future plans for a game...

  Harry could see the pattern, he could see how Mr. Goyle was weaving, he could see how and when they all needed to fire in order to create a web of shots that Mr. Goyle wouldn't be able to dodge, but he just hadn't been able to explain it fast enough to his soldiers, they couldn't coordinate their shots well enough, and now they didn't have enough people left to do it -

  I refuse to lose, not like this, not my whole army to one soldier!

  Mr. Goyle's broomstick turned faster than anything should have been able to turn and started to angle in toward Harry and his surviving troops, he could sense the boy beside him tensing, getting ready to throw himself in front of his general.

  SCREW THIS.

  Harry's wand came up, focusing on Mr. Goyle, Harry's mind visualized the pattern, and Harry's lips opened and his voice screamed -

  "Luminosluminosluminosluminosluminosluminosluminosluminosluminosluminosluminosluminos-"

  When Harry's eyes opened again, he found himself resting in a comfortable position with his hands folded over his chest, holding his wand like a fallen hero.

  Slowly, Harry sat up. His magic was aching, a strange sensation but not an entirely unpleasant one, much like the burn and lethargy that followed hard physical exercise.

  "The general's awake!" cried a voice, and Harry blinked and focused in that direction.

  Four of his soldiers held their wands on a shimmering prismatic hemisphere, and Harry realized that the battle wasn't over. Right... he hadn't been hit by a Sleep Hex, just exhausted himself, so when he woke up, he was still in the game.

  Harry suspected he was going to get a lecture from someone-or-other about not exhausting his magic to the point of unconsciousness over a children's game. But he hadn't hurt Mr. Goyle when he'd lost his temper, and that was the important thing.

  Then Harry's mind clicked on another implication, and he looked down at the steel ring on his left hand's pinky finger, and almost swore out loud when he saw that the tiny diamond was missing and there was a marshmallow lying on the ground near where he'd fallen.

  He'd sustained that Transfiguration for seventeen days, and would now need to start over.

  Could've been worse. He could've done this fourteen days later, after Professor McGonagall had approved him to Transfigure his father's rock. That was one very good lesson to learn the easy way.

  Note to self: Always remove ring from finger before completely exhausting magic.

  Harry pushed himself up, making rather hard going of it. Using up your magic didn't exhaust your muscles, but dodging around trees certainly did.

  He staggered over to the iridescent hemisphere that contained Draco Malfoy, who was holding his wand aloft to sustain the shield, and smiling coldly at Harry.

  "Where's the fifth soldier?" said Harry.

  "Um..." said a boy whose name Harry couldn't remember at the moment. "I fired a Sleep Hex at the shield and it bounced off and hit Lavender, I mean the angle shouldn't have been right but it did..."

  Draco was smirking inside the shield.

  "So let me guess," Harry said, looking Draco directly in the eyes, "those neat little trios are the formation used by professional magical militaries? Made up of trained soldiers who can easily hit moving targets if their own hands are steady, and who can combine their defensive powers so long as they stay together? Unlike your soldiers?"

  The smirk had vanished from Draco's face, which was now hard and grim.

  "You know," Harry said lightly, knowing that none of the others would understand the real message passing between them, "it just goes to show that you should always question everything you see your role models doing, and ask why it's being done, and whether it makes sense in context for you to do it too. Don't forget to apply that advice to real life, by the way. And thanks for the slow-moving clustered targets."

  Because Draco had already gotten that lecture, and, Harry suspected, discounted it out of suspicion that Harry was trying to shift his loyalties further away from pureblood tradition. Which of course Harry was. But this example would make an excellent excuse, next Saturday, to claim that questioning authority was a merely practical technique for real life. And Harry would also mention the experiments he'd run, first with individuals and then with groups, to check that his ideas about the importance of speed had actually been correct, by way of hammering home the point of Draco needing to keep an eye out at all times for chances to apply the methods in everyday practice.

  "You haven't won yet, General Potter!" snarled Draco. "Maybe we'll run out of time, and Professor Quirrell will call it a draw."

  A fair and worrisome point. The war only ended when Professor Quirrell, in his personal judgment, decided one army had won by practical real-world standards. There was no formal victory condition, Professor Quirrell had explained, because then Harry would figure out how to game the rules. Harry had to admit this was a fair cop.

  And Harry couldn't blame Professor Quirrell for not calling an end, because it was plausible that the last soldier of Dragon Army could take out all five survivors of the Chaos Legion.

  "All right," Harry said. "Does anyone know anything about General Malfoy's shield spell?"

/>   It developed that Draco's shield was a version of the standard Protego which had several disadvantages, the most important of which was that the shield couldn't move with the caster.

  The upside - or from Harry's perspective, downside - was that it was easier to learn, easier to cast, and much easier to sustain for long times.

  They would need to hammer the shield with attack spells in order to bring it down.

  And Draco could apparently exert some control over the angle of reflection at which the spells would bounce off.

  The thought occurred to Harry that they could use Wingardium Leviosa to pile up heavy rocks on the shield until Draco couldn't sustain it against the pressure... but then the rocks might fall in afterward and hit Draco, and injuring the enemy general for real was not among today's goals.

  "So," said Harry. "Are there such things as specialized shield-piercing spells?"

  There were.

  Harry asked if any of his soldiers knew them.

  No one did.

  Draco was smirking again, inside his shield.

  Harry asked if there was any sort of attack spell that wouldn't bounce.

  Lightning bolts, it seemed, were usually absorbed by shields instead of bouncing off them.

  ...No one knew how to cast any sort of lightning-related spell.

  Draco sniggered.

  Harry sighed.

  He quite deliberately laid his wand on the ground.

  And Harry announced, with some weariness in his voice, that he would just go ahead and take down the shield himself, using some method that would remain mysterious; and everyone else was to fire on Draco as soon as his shield went down.

  The Chaos Legionnaires looked nervous.

  Draco looked calm, which was to say, controlled.

  A thin, folded blanket came out of Harry's pouch.

  Harry sat down next to the shimmering shield, and pulled the blanket over his head so no one could see what he did - except Draco, of course.

  From Harry's pouch came a car battery and a set of jumper cables.