Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  "Um," Harry said, "can we go get the healer's kit now?"

  The witch paused, and looked back at him steadily. "And if I say no - that it is too expensive and you won't need it - then what?"

  Harry's face twisted in bitterness. "Exactly what you're thinking, Professor McGonagall. Exactly what you're thinking. I conclude you're another crazy adult I can't talk to, and I start planning how to get my hands on a healer's kit anyway."

  "I am your guardian on this trip," Professor McGonagall said with a tinge of danger. "I will not allow you to push me around."

  "I understand," Harry said. He kept the resentment out of his voice, and didn't say any of the other things that came to mind. Professor McGonagall had told him to think before he spoke. He probably wouldn't remember that tomorrow, but he could at least remember it for five minutes.

  The witch's wand made a slight circle in her hand, and the noises of Diagon Alley came back. "All right, young man," she said. "Let's go get that healer's kit."

  Harry's jaw dropped in surprise. Then he hurried after her, almost stumbling in his sudden rush.

  The shop was the same as they had left it, recognisable and unrecognisable items still laid out on the slanted wooden display, the grey glow still protecting and the salesgirl back in her old position. The salesgirl looked up as they approached, her face showing surprise.

  "I'm sorry," she said as they got closer, and Harry spoke at almost the same moment, "I apologise for -"

  They broke off and looked at each other, and then the salesgirl laughed a little. "I didn't mean to get you in trouble with Professor McGonagall," she said. Her voice lowered conspiratorially. "I hope she wasn't too awful to you."

  "Della!" said Professor McGonagall, sounding scandalised.

  "Bag of gold," Harry said to his pouch, and then looked back up at the salesgirl while he counted out five Galleons. "Don't worry, I understand that she's only awful to me because she loves me."

  He counted out five Galleons to the salesgirl while Professor McGonagall was spluttering something unimportant. "One Emergency Healing Pack Plus, please."

  It was actually sort of unnerving to see how the Widening Lip swallowed the briefcase-sized medical kit. Harry couldn't help wondering what would happen if he tried climbing into the mokeskin pouch himself, given that only the person who put something in was supposed to be able to take it out again.

  When the pouch was done... eating... his hard-won purchase, Harry swore he heard a small burping sound afterward. That had to have been spelled in on purpose. The alternative hypothesis was too horrifying to contemplate... in fact Harry couldn't even think of any alternative hypotheses. Harry looked back up at the Professor, as they began walking through Diagon Alley once more. "Where to next?"

  Professor McGonagall pointed toward a shop that looked as if it had been made from flesh instead of bricks and covered in fur instead of paint. "Small pets are permitted at Hogwarts - you could get an owl to send letters, for example -"

  "Can I pay a Knut or something and rent an owl when I need to send mail?"

  "Yes," said Professor McGonagall.

  "Then I think emphatically no."

  Professor McGonagall nodded, as though ticking off a point. "Might I ask why not?"

  "I had a pet rock once. It died."

  "You don't think you could take care of a pet?"

  "I could," Harry said, "but I would end up obsessing all day long about whether I'd remembered to feed it that day or if it was slowly starving in its cage, wondering where its master was and why there wasn't any food."

  "That poor owl," the older witch said in a soft voice. "Abandoned like that. I wonder what it would do."

  "Well, I expect it'd get really hungry and start trying to claw its way out of the cage or the box or whatever, though it probably wouldn't have much luck with that -" Harry stopped short.

  The witch went on, still in that soft voice. "And what would happen to it afterward?"

  "Excuse me," Harry said, and he reached up to take Professor McGonagall by the hand, gently but firmly, and steered her into yet another alleyway; after ducking so many well-wishers the process had become almost unnoticeably routine. "Please cast that silencing spell."

  "Quietus."

  Harry's voice was shaking. "That owl does not represent me, my parents never locked me in a cupboard and left me to starve, I do not have abandonment fears and I don't like the trend of your thoughts, Professor McGonagall!"

  The witch looked down at him gravely. "And what thoughts would those be, Mr. Potter?"

  "You think I was," Harry was having trouble saying it, "I was abused?"

  "Were you?"

  "No!" Harry shouted. "No, I never was! Do you think I'm stupid? I know about the concept of child abuse, I know about inappropriate touching and all of that and if anything like that happened I would call the police! And report it to the head teacher! And look up social services in the phone book! And tell Grandpa and Grandma and Mrs. Figg! But my parents never did anything like that, never ever ever! How dare you suggest such a thing!"

  The older witch gazed at him steadily. "It is my duty as Deputy Headmistress to investigate possible signs of abuse in the children under my care."

  Harry's anger was spiralling out of control into pure, black fury. "Don't you ever dare breathe a word of these, these insinuations to anyone else! No one, do you hear me, McGonagall? An accusation like that can ruin people and destroy families even when the parents are completely innocent! I've read about it in the newspapers!" Harry's voice was climbing to a high-pitched scream. "The system doesn't know how to stop, it doesn't believe the parents or the children when they say nothing happened! Don't you dare threaten my family with that! I won't let you destroy my home!"

  "Harry," the older witch said softly, and she reached out a hand towards him -

  Harry took a fast step back, and his hand snapped up and knocked hers away.

  McGonagall froze, then she pulled her hand back, and took a step backwards. "Harry, it's all right," she said. "I believe you."

  "Do you," Harry hissed. The fury still roaring through his blood. "Or are you just waiting to get away from me so you can file the papers?"

  "Harry, I saw your house. I saw you with your parents. They love you. You love them. I do believe you when you say that your parents are not abusing you. But I had to ask, because there is something strange at work here."

  Harry stared at her coldly. "Like what?"

  "Harry, I've seen many abused children in my time at Hogwarts, it would break your heart to know how many. And, when you're happy, you don't behave like one of those children, not at all. You smile at strangers, you hug people, I put my hand on your shoulder and you didn't flinch. But sometimes, only sometimes, you say or do something that seems very much like... someone who spent his first eleven years locked in a cellar. Not the loving family that I saw." Professor McGonagall tilted her head, her expression growing puzzled again.

  Harry took this in, processing it. The black rage began to drain away, as it dawned on him that he was being listened to respectfully, and that his family wasn't in danger.

  "And how do you explain your observations, Professor McGonagall?"

  "I don't know," she said. "But it's possible that something could have happened to you that you don't remember."

  Fury rose up again in Harry. That sounded all too much like what he'd read in the newspaper stories of shattered families. "Suppressed memory is a load of pseudoscience! People do not repress traumatic memories, they remember them all too well for the rest of their lives!"

  "No, Mr. Potter. There is a Charm called Obliviation."

  Harry froze in place. "A spell that erases memories?"

  The older witch nodded. "But not all the effects of the experience, if you see what I'm saying, Mr. Potter."

  A chill went down Harry's spine. That hypothesis... could not be easily refuted. "But my parents couldn't do that!"

  "Indeed not," said Professor McGonagall. "It wo
uld have taken someone from the wizarding world. There's... no way to be certain, I'm afraid."

  Harry's rationalist skills began to boot up again. "Professor McGonagall, how sure are you of your observations, and what alternative explanations could there also be?"

  The witch opened her hands, as though to show their emptiness. "Sure? I'm sure of nothing, Mr. Potter. In all my life I've never met anyone else like you. Sometimes you just don't seem eleven years old or even all that human."

  Harry's eyebrows rose toward the sky -

  "I'm sorry!" Professor McGonagall said quickly. "I'm very sorry, Mr. Potter. I was trying to make a point and I'm afraid that came out sounding different from what I had in mind -"

  "On the contrary, Professor McGonagall," Harry said, and slowly smiled. "I shall take it as a very great compliment. But would you mind if I offered an alternative explanation?"

  "Please do."

  "Children aren't meant to be too much smarter than their parents," Harry said. "Or too much saner, maybe - my father could probably outsmart me if he was, you know, actually trying, instead of using his adult intelligence mainly to come up with new reasons not to change his mind -" Harry stopped. "I'm too smart, Professor. I've got nothing to say to normal children. Adults don't respect me enough to really talk to me. And frankly, even if they did, they wouldn't sound as smart as Richard Feynman, so I might as well read something Richard Feynman wrote instead. I'm isolated, Professor McGonagall. I've been isolated my whole life. Maybe that has some of the same effects as being locked in a cellar. And I'm too intelligent to look up to my parents the way that children are designed to do. My parents love me, but they don't feel obliged to respond to reason, and sometimes I feel like they're the children - children who won't listen and have absolute authority over my whole existence. I try not to be too bitter about it, but I also try to be honest with myself, so, yes, I'm bitter. And I also have an anger management problem, but I'm working on it. That's all."

  "That's all?"

  Harry nodded firmly. "That's all. Surely, Professor McGonagall, even in magical Britain, the normal explanation is always worth considering?"

  It was later in the day, the sun lowering in the summer sky and shoppers beginning to peter out from the streets. Some shops had already closed; Harry and Professor McGonagall had bought his textbooks from Flourish and Blotts just under the deadline. With only a slight explosion when Harry had made a beeline for the keyword "Arithmancy" and discovered that the seventh-year textbooks invoked nothing more mathematically advanced than trigonometry.

  At this moment, though, dreams of low-hanging research fruit were far from Harry's mind.

  At this moment, the two of them were walking out of Ollivander's, and Harry was staring at his wand. He'd waved it, and produced multicoloured sparks, which really shouldn't have come as such an extra shock after everything else he'd seen, but somehow -

  I can do magic.

  Me. As in, me personally. I am magical; I am a wizard.

  He had felt the magic pouring up his arm, and in that instant, realised that he had always had that sense, that he had possessed it his whole life, the sense that was not sight or sound or smell or taste or touch but only magic. Like having eyes but keeping them always closed, so that you didn't even realise that you were seeing darkness; and then one day the eye opened, and saw the world. The shock of it had poured through him, touching pieces of himself, awakening them, and then died away in seconds; leaving only the certain knowledge that he was now a wizard, and always had been, and had even, in some strange way, always known it.

  And -

  "It is very curious indeed that you should be destined for this wand when its brother why, its brother gave you that scar."

  That could not possibly be coincidence. There had been thousands of wands in that shop. Well, okay, actually it could be coincidence, there were six billion people in the world and thousand-to-one coincidences happened every day. But Bayes's Theorem said that any reasonable hypothesis which made it more likely than a thousand-to-one that he'd end up with the brother to the Dark Lord's wand, was going to have an advantage.

  Professor McGonagall had simply said how peculiar and left it at that, which had put Harry into a state of shock at the sheer, overwhelming uncuriosity of wizards and witches. In no imaginable world would Harry have just went "Hm" and walked out of the shop without even trying to come up with a hypothesis for what was going on.

  His left hand rose and touched his scar.

  What... exactly...

  "You're a full wizard now," said Professor McGonagall. "Congratulations."

  Harry nodded.

  "And what do you think of the wizarding world?" said she.

  "It's strange," Harry said. "I ought to be thinking about everything I've seen of magic... everything that I now know is possible, and everything I now know to be a lie, and all the work left before me to understand it. And yet I find myself distracted by relative trivialities like," Harry lowered his voice, "the whole Boy-Who-Lived thing." There didn't seem to be anyone nearby, but no point tempting fate.

  Professor McGonagall ahemmed. "Really? You don't say."

  Harry nodded. "Yes. It's just... odd. To find out that you were part of this grand story, the quest to defeat the great and terrible Dark Lord, and it's already done. Finished. Completely over with. Like you're Frodo Baggins and you find out that your parents took you to Mount Doom and had you toss in the Ring when you were one year old and you don't even remember it."

  Professor McGonagall's smile had grown somewhat fixed.

  "You know, if I were anyone else, anyone else at all, I'd probably be pretty worried about living up to that start. Gosh, Harry, what have you done since you defeated the Dark Lord? Your own bookshop? That's great! Say, did you know I named my child after you? But I have hopes that this will not prove to be a problem." Harry sighed. "Still... it's almost enough to make me wish that there were some loose ends from the quest, just so I could say that I really, you know, participated somehow."

  "Oh?" said Professor McGonagall in an odd tone. "What did you have in mind?"

  "Well, for example, you mentioned that my parents were betrayed. Who betrayed them?"

  "Sirius Black," the witch said, almost hissing the name. "He's in Azkaban. Wizarding prison."

  "How probable is it that Sirius Black will break out of prison and I'll have to track him down and defeat him in some sort of spectacular duel, or better yet put a large bounty on his head and hide out in Australia while I wait for the results?"

  Professor McGonagall blinked. Twice. "Not likely. No one has ever escaped from Azkaban, and I doubt that he will be the first."

  Harry was a bit sceptical of that "no one has ever escaped from Azkaban" line. Still, maybe with magic you could actually get close to a 100% perfect prison, especially if you had a wand and they did not. The best way to get out would be to not go there in the first place.

  "All right then," Harry said. "Sounds like it's been nicely wrapped up." He sighed, scrubbing his palm over his head. "Or maybe the Dark Lord didn't really die that night. Not completely. His spirit lingers, whispering to people in nightmares that bleed over into the waking world, searching for a way back into the living lands he swore to destroy, and now, in accordance with the ancient prophecy, he and I are locked in a deadly duel where the winner shall lose and the loser shall win -"

  Professor McGonagall's head swivelled, and her eyes darted around, as though to search the street for listeners.

  "I'm joking, Professor," Harry said with some annoyance. Sheesh, why did she always take everything so seriously -

  A slow sinking sensation began to dawn in the pit of Harry's stomach.

  Professor McGonagall looked at Harry with a calm expression. A very, very calm expression. Then a smile was put on. "Of course you are, Mr. Potter."

  Aw crap.

  If Harry had needed to formalise the wordless inference that had just flashed into his mind, it would have come out something like,
'If I estimate the probability of Professor McGonagall doing what I just saw as the result of carefully controlling herself, versus the probability distribution for all the things she would do naturally if I made a bad joke, then this behavior is significant evidence for her hiding something.'

  But what Harry actually thought was, Aw crap.

  Harry turned his own head to scan the street. Nope, no one nearby. "He's not dead, is he," Harry sighed.

  "Mr. Potter -"

  "The Dark Lord is alive. Of course he's alive. It was an act of utter optimism for me to have even dreamed otherwise. I must have taken leave of my senses, I can't imagine what I was thinking. Just because someone said that his body was found burned to a crisp, I can't imagine why I would have thought he was dead. Clearly I have much left to learn about the art of proper pessimism."

  "Mr. Potter -"

  "At least tell me there's not really a prophecy..." Professor McGonagall was still giving him that bright, fixed smile. "Oh, you have got to be kidding me."

  "Mr. Potter, you shouldn't go inventing things to worry about -"

  "Are you actually going to tell me that? Imagine my reaction later, when I find out that there was something to worry about after all."

  Her fixed smile faltered.

  Harry's shoulders slumped. "I have a whole world of magic to analyse. I do not have time for this."

  Then both of them shut up, as a man in flowing orange robes appeared on the street and slowly passed them by; Professor McGonagall's eyes tracked him, unobtrusively. Harry's mouth was moving as he chewed hard on his lip, and someone watching closely would have noticed a tiny spot of blood appear.

  When the orange-robed man had passed into the distance, Harry spoke again, in a low murmur. "Are you going to tell me the truth now, Professor McGonagall? And don't bother trying to wave it off, I'm not stupid."

  "You're eleven years old, Mr. Potter!" she said in a harsh whisper.

  "And therefore subhuman. Sorry... for a moment there, I forgot."