Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  They had asked about Dementors.

  They had asked about phoenixes.

  They had asked about dragons and trolls and house elves.

  Harry had frowned, pointed out that creatures which needed the most magic could just be dying out entirely, and had asked for the most powerful magical creatures known.

  There wasn't anything unfamiliar on the list, except for a species of Dark creature called mind flayers which the translator noted had finally been exterminated by Harold Shea, and those didn't sound half as scary as Dementors.

  Magical creatures were as powerful now as they'd ever been, apparently.

  The sickness in Draco's stomach was easing, and now he just felt confused.

  "Harry," Draco said in the middle of the old man translating a list of all eleven powers of a beholder's eyes, "what does this mean?"

  Harry held up a finger and the old man finished the list.

  Then Harry thanked all the portraits for helping - Draco, pretty much on automatic, did so as well and more graciously - and they headed back to the classroom.

  And Harry brought out the original parchment with the hypotheses, and began scribbling.

  Observation:

  Wizardry isn't as powerful now as it was when Hogwarts was founded.

  Hypotheses:

  1 . Magic itself is fading.

  2 . Wizards are interbreeding with Muggles and Squibs.

  3 . Knowledge to cast powerful spells is being lost.

  4. Wizards are eating the wrong foods as children, or something else besides blood is making them grow up weaker.

  5. Muggle technology is interfering with magic. (Since 800 years ago?)

  6. Stronger wizards are having fewer children. (Draco = only child? Check if 3 powerful wizards, Quirrell / Dumbledore / Dark Lord, had any children.)

  Tests:

  A. Are there spells we know but can't cast (1 or 2) or are the lost spells no longer known (3)? Result: Inconclusive due to Interdict of Merlin. No known uncastable spell, but could simply have not been passed on.

  B. Did ancient first-year students cast the same sort of spells, with the same power, as now? (Weak evidence for 1 over 2, but blood could also be losing powerful wizardry only.) Result: Same level of first-year spells then as now.

  C. Additional test that distinguishes 1 and 2 using scientific knowledge of blood, will explain later. Result: There's only one place in the recipe that makes you a wizard, and either you have two papers saying 'magic' or you don't.

  D. Are magical creatures losing their powers? Distinguishes 1 from (2 or 3). Result: Magical creatures seem to be as strong as they ever were.

  "A failed," said Harry Potter. "B is weak evidence for 1 over 2. C falsifies 2. D falsifies 1. 4 was unlikely and B argues against 4 as well. 5 was unlikely and D argues against it. 6 is falsified along with 2. That leaves 3. Interdict of Merlin or not, I didn't actually find any known spell that couldn't be cast. So when you add it all up, it looks like knowledge is being lost."

  And the trap snapped shut.

  As soon as the panic went away, as soon as Draco understood that magic wasn't fading out, it took all of five seconds to realize.

  Draco shoved himself away from the desk and stood up so hard that his chair skittered with a scraping noise across the floor and fell over.

  "So it was all just a stupid trick, then."

  Harry Potter stared at him for a moment, still sitting. When he spoke, his voice was quiet. "It was a fair test, Draco. If it had come out a different way, I would have accepted it. That's not something I would ever cheat on. Ever. I didn't look at your data before I made my predictions. I told you up front when the Interdict of Merlin invalidated the first experiment -"

  "Oh," Draco said, the anger starting to come out into his voice, "you didn't know how the whole thing was going to come out?"

  "I didn't know anything you didn't know," Harry said, still quietly. "I admit that I suspected. Hermione Granger was too powerful, she should have been barely magical and she wasn't, how can a Muggleborn be the best spellcaster in Hogwarts? And she's getting the best grades on her essays too, it's too much coincidence for one girl to be the strongest magically and academically unless there's a single cause. Hermione Granger's existence pointed to there being only one thing that makes you a wizard, something you either have or you don't, and the power differences coming from how much we know and how much we practice. And there weren't different classes for purebloods and Muggleborns, and so on. There were too many ways the world didn't look the way it would look if you were right. But Draco, I didn't see anything you couldn't see too. I didn't perform any tests I didn't tell you about. I didn't cheat, Draco. I wanted us to work out the answer together. And I never thought that magic might be fading out of the world until you said it. It was a scary idea for me, too."

  "Whatever," Draco said. He was working very hard to control his voice and not just start screaming at Harry. "You claim you're not going to run off and tell anyone else about this."

  "Not without consulting you first," Harry said. He opened his hands in a pleading gesture. "Draco, I'm being as nice as I can but the world turned out to just not be that way."

  "Fine. Then you and I are through. I'm going to just walk away and forget any of this ever happened."

  Draco spun around, feeling the burning sensation in his throat, the sense of betrayal, and that was when he realized he really had liked Harry Potter, and that thought didn't slow him down for a moment as he strode toward the classroom door.

  And Harry Potter's voice came, now louder, and worried:

  "Draco... you can't forget. Don't you understand? That was your sacrifice."

  Draco stopped in midstride and turned around. "What are you talking about?"

  But there was already a freezing coldness in Draco's spine.

  He knew even before Harry Potter said it.

  "To become a scientist. You questioned one of your beliefs, not just a small belief but something that had great significance to you. You did experiments, gathered data, and the outcome proved the belief was wrong. You saw the results and understood what they meant." Harry Potter's voice was faltering. "Remember, Draco, you can't sacrifice a true belief that way, because the experiments will confirm it instead of falsifying it. Your sacrifice to become a scientist was your false belief that wizard blood was mixing and getting weaker."

  "That's not true!" said Draco. "I didn't sacrifice the belief. I still believe that!" His voice was getting louder, and the chill was getting worse.

  Harry Potter shook his head. His voice came in a whisper. "Draco... I'm sorry, Draco, you don't believe it, not anymore." Harry's voice rose again. "I'll prove it to you. Imagine that someone tells you they're keeping a dragon in their house. You tell them you want to see it. They say it's an invisible dragon. You say fine, you'll listen to it move. They say it's an inaudible dragon. You say you'll throw some cooking flour into the air and see the outline of the dragon. They say the dragon is permeable to flour. And the telling thing is that they know, in advance, exactly which experimental results they'll have to explain away. They know everything will come out the way it does if there's no dragon, they know in advance just which excuses they'll have to make. So maybe they say there's a dragon. Maybe they believe they believe there's a dragon, it's called belief-in-belief. But they don't actually believe it. You can be mistaken about what you believe, most people never realize there's a difference between believing something and thinking it's good to believe it." Harry Potter had risen from the desk now, and taken a few steps toward Draco. "And Draco, you don't believe any more in blood purism, I'll show you that you don't. If blood purism is true, then Hermione Granger doesn't make sense, so what could explain her? Maybe she's a wizarding orphan raised by Muggles, just like I was? I could go to Granger and ask to see pictures of her parents, to see if she looks like them. Would you expect her to look different? Should we go perform that test?"

  "They would have put her with relatives," Dra
co said, his voice trembling. "They'll still look the same."

  "You see. You already know what experimental result you'll have to excuse. If you still believed in blood purism you would say, sure, let's go take a look, I bet she won't look like her parents, she's too powerful to be a real Muggleborn -"

  "They would have put her with relatives!"

  "Scientists can do tests to check for sure if someone is the true child of a father. Granger would probably do it if I paid her family enough. She wouldn't be afraid of the results. So what do you expect that test to show? Tell me to run it and we will. But you already know what the test will say. You'll always know. You won't ever be able to forget. You might wish you believed in blood purism, but you'll always expect to see happen just exactly what would happen if there was only one thing that made you a wizard. That was your sacrifice to become a scientist."

  Draco's breathing was ragged. "Do you realize what you've done?" Draco surged forward and he seized Harry by the collar of his robes. His voice rose to a scream, it sounded unbearably loud in the closed classroom and the silence. "Do you realize what you've done?"

  Harry's voice was shaky. "You had a belief. The belief was false. I helped you see that. What's true is already so, owning up to it doesn't make it worse -"

  The fingers on Draco's right hand clenched into a fist and that hand dropped down and blasted up unstoppably and punched Harry Potter in the jaw so hard that his body went crashing back into a desk and then to the floor.

  "Idiot!" screamed Draco. "Idiot! Idiot!"

  "Draco," whispered Harry from the floor, "Draco, I'm sorry, I didn't think this would happen for months, I didn't expect you to awaken as a scientist this quickly, I thought I would have longer to prepare you, teach you the techniques that make it hurt less to admit you're wrong -"

  "What about Father?" Draco said. His voice trembled with rage. "Were you going to prepare him or did you just not care what happened after this?"

  "You can't tell him!" Harry said, his voice rising in alarm. "He's not a scientist! You promised, Draco!"

  For a moment the thought of Father not knowing came as a relief.

  And then the real anger started to rise.

  "So you planned for me to lie to him and tell him I still believe," Draco said, voice shaking. "I'll always have to lie to him, and now when I grow up I can't be a Death Eater, and I won't even be able to tell him why not."

  "If your father really loves you," whispered Harry from the floor, "he'll still love you even if you don't become a Death Eater, and it sounds like your father does really love you, Draco -"

  "Your stepfather is a scientist," Draco said. The words coming out like biting knives. "If you weren't going to be a scientist, he would still love you. But you'd be a little less special to him."

  Harry flinched. The boy opened his mouth, as if to say 'I'm sorry', and then closed his mouth, seeming to think better of it, which was either very smart of him or very lucky, because Draco might have tried to kill him.

  "You should have warned me," Draco said. His voice rose. "You should have warned me!"

  "I... I did... every time I told you about the power, I told you about the price. I said, you have to admit you're wrong. I said this would be the hardest path for you. That this was the sacrifice anyone had to make to become a scientist. I said, what if the experiment says one thing and your family and friends say another -"

  "You call that a warning?" Draco was screaming now. "You call that a warning? When we're doing a ritual that calls for a permanent sacrifice?"

  "I... I..." The boy on the floor swallowed. "I guess maybe it wasn't clear. I'm sorry. But that which can be destroyed by the truth should be."

  Hitting him wasn't enough.

  "You're wrong about one thing," Draco said, his voice deadly. "Granger isn't the strongest student in Hogwarts. She just gets the best grades in class. You're about to find out the difference."

  Sudden shock showed in Harry's face, and he tried to roll quickly to his feet -

  It was already too late for him.

  "Expelliarmus!"

  Harry's wand flew across the room.

  "Gom jabbar!"

  A pulse of inky blackness struck Harry's left hand.

  "That's a torture spell," said Draco. "It's for getting information out of people. I'm just going to leave it on you and lock the door behind me when I go. Maybe I'll set the locking spell to wear off after a few hours. Maybe it won't wear off until you die in here. Have fun."

  Draco moved smoothly backward, wand still on Harry. Draco's hand dipped down, picked up his bookbag, without his aim wavering.

  The pain was already showing in Harry Potter's face as he spoke. "Malfoys are above the underage magic laws, I take it? It's not because your blood is stronger. It's because you already practiced. In the beginning you were as weak as any of us. Is my prediction wrong?"

  Draco's hand whitened on his wand, but his aim stayed steady.

  "Just so you know," Harry said through gritted teeth, "if you'd told me I was wrong I would have listened. I won't ever torture you when you show me that I'm wrong. And you will. Someday. You're awakened as a scientist now, and even if you never learn to use your power, you'll always," Harry gasped, "be looking, for ways, to test, your beliefs -"

  Draco's backing away was less smooth, now, a little faster, and he had to work to keep his wand on Harry as he reached back to open the door and stepped back out of the classroom.

  Then Draco shut the door again.

  He cast the most powerful locking Charm he knew.

  Draco waited until he heard Harry's first scream before casting the Quietus.

  And then he walked away.

  "Aaahhhhh! Finite Incantatem! Aaaahhh!"

  Harry's left hand had been put into a pot of boiling cooking oil and left there. He'd put everything he had into the Finite Incantatem and it still wasn't working.

  Some hexes required specific counters or you couldn't undo them, or maybe it was just that Draco was that much stronger.

  "Aaaaahhhh!"

  Harry's hand was really starting to hurt, now, and that was interfering with his attempts to think creatively.

  But a few screams later, Harry realized what he had to do.

  His pouch, unfortunately, was on the wrong side of his body, and it took some twisting to reach into it, especially with his other arm flailing around in a reflex, unstoppable attempt to fling off the source of pain. By the time he managed it his other arm had managed to throw away his wand again.

  "Medical ahhhhh kit! Medical kit!"

  On the floor, the green light was too dim to see by.

  Harry couldn't stand. He couldn't crawl. He rolled across the floor to where he thought his wand was, and it wasn't there, and with one hand he managed to raise himself high enough to see his wand, and he rolled there, and got the wand, and rolled back to where the medical kit was opened. There was also a good deal of screaming, and a bit of throwing up.

  It took eight tries before Harry could cast Lumos.

  And then, well, the package wasn't designed to be opened one-handed, because all wizards were idiots, that was why. Harry had to use his teeth and so it took a while before Harry finally managed to wrap the Numbcloth over his left hand.

  When all feeling in his left hand was finally gone, Harry let his mind come apart, and lay motionless on the floor, and cried for a while.

  Well, Harry's mind said silently into itself, when it had recovered enough to think in words again. Was it worth it?

  Slowly, Harry's functional hand reached up to a desk.

  Harry pulled himself to his feet.

  Took a deep breath.

  Exhaled.

  Smiled.

  It wasn't much of a smile, but it was a smile nonetheless.

  Thank you, Professor Quirrell, I couldn't have lost without you.

  He hadn't redeemed Draco yet, not even close. Contrary to what Draco himself might now believe, Draco was still the child of a Death Eater, throu
gh and through. Still a boy who'd grown up thinking "rape" was something the cool older kids did. But it was one heck of a start.

  Harry couldn't claim it had all gone just as planned. It had all gone just as completely made up on the spot. The plan hadn't called for this to happen until December or thereabouts, after Harry had taught Draco the techniques not to deny the evidence when he saw it.

  But he'd seen the look of fear on Draco's face, realized that Draco was already taking an alternative hypothesis seriously, and seized the moment. One case of true curiosity had the same sort of redeeming power in rationality that one case of true love had in movies.

  In retrospect, Harry had given himself hours to make the most important discovery in the history of magic, and months to break through the undeveloped mental barriers of an eleven-year-old boy. This could indicate that Harry had some sort of major cognitive deficit with respect to estimating task completion times.

  Was Harry going to Science Hell for what he'd done? Harry wasn't sure. He'd contrived to keep Draco's mind on the possibility that magic was fading, made sure Draco would carry out the part of the experiment that would seem at first to point in that direction. He'd waited until after explaining genetics to prompt Draco into realizing about magical creatures (though Harry had thought in terms of ancient artifacts like the Sorting Hat, which no one could duplicate anymore, but which continued to function). But Harry hadn't actually exaggerated any evidence, hadn't distorted the meaning of any results. When the Interdict of Merlin had invalidated the test that should have been definitive, he'd told Draco up front.

  And then there was the part after that...

  But he hadn't actually lied to Draco. Draco had believed it, and that would make it true.

  The end, admittedly, had not been fun.

  Harry turned, and staggered toward the door.

  Time to test Draco's locking spell.

  The first step was simply trying to turn the doorknob. Draco could have been bluffing.

  Draco hadn't been bluffing.

  "Finite Incantatem." Harry's voice came out rather hoarse, and he could feel that the spell hadn't taken.