Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  "No!" she said. "No, you shouldn't think that, Harry! Just - just - just everything!" She realized that her wand was still pointed at Harry, and she lowered it. She was trying very hard not to burst out into tears. "Everything!" she repeated, and couldn't find any better to say than that, although she was certain that Harry wanted to tell her to be specific.

  "I think I understand," Harry said cautiously. "What're you reading?"

  Before she could stop him, them, Harry bent over the library-desk to see the book she was reading, leaning his head forward before she could think to grab the book away -

  Harry stared at the open page.

  "The World's Wealthiest Wizards and How They Got That Way," Harry read off the book's title from the top. "Number sixty-five, Sir Gareth, owner of a transportation company that won the 19th-century shipping wars... monopoly on oh-tee-threes... I see."

  "I s'pose you're going to tell me that I don't need to worry about anything and you'll take care of it all?" It came out sounding harsher than she would've wanted, and she felt another stab of guilt for being such a terrible person.

  "Nah," Harry said, sounding oddly cheerful. "I can put myself in your shoes well enough to know that if you paid a bunch of money to save me, I'd be trying to pay it back. I'd know it was silly on some level, and I'd still be trying to pay it back all by myself. There's no way I wouldn't understand that, Hermione."

  Hermione's face screwed up and she felt moisture in the corners of her eyes.

  "Fair warning, though," Harry went on, "I might solve the debt to Lucius Malfoy myself if I see a way before you do, it's more important to get that sorted immediately than which one of us gets it sorted. Anything interesting so far?"

  Three-quarters of her was running in circles and smashing into trees as she tried to figure out the implications of everything Harry had just said (did he still respect her as a heroine? or did that mean he thought she couldn't do it on her own?) and meanwhile a much more sensible part of Hermione flipped back the book to page 37 which had the most promising entry she'd seen so far (though in her imagination she always did it on her own and took Harry completely by surprise) -

  "I thought this seemed quite interesting," her voice said.

  "Number fourteen, 'Crozier', true name unknown," Harry read. "Wow, that is... that is the gaudiest checkered top hat I've ever seen. Wealth, at least six hundred thousand Galleons... so around thirty million pounds, not enough to make a Muggle famous, but good enough for the smaller wizard population, I guess. Rumored to be a modern alias of the six-century-old Nicholas Flamel, the only known wizard to succeed at the incredibly difficult alchemical procedure for creating the Philosopher's Stone, which enables the transmutation of base metals into gold or silver as well as... the Elixir of Life which indefinitely prolongs the youth and health of the user... Um, Hermione, this seems obviously false."

  "I've read more references to Nicholas Flamel," Hermione said. "The Rise and Fall of the Dark Arts says he secretly trained Dumbledore to stand up to Grindelwald. There's a lot of books that take the story seriously, not just this one... you think it's too good to be true?"

  "No, of course not," said Harry. Harry pulled out the chair next to her own, at the small table, and sat down beside her in his accustomed place on her right, just like he'd never left; she had to choke back a catch in her throat. "The idea of 'too good to be true' isn't causal reasoning, the universe doesn't check if the output of the equations is 'too good' or 'too bad' before allowing it. People used to think that airplanes and smallpox vaccines were too good to be true. Muggles have figured out ways to travel to other stars without even using magic, and you and I can use our wands to do things that Muggle physicists think are literally impossible. I can't even imagine what we could rule out the real laws of magic being able to do."

  "So what's the problem, then?" Hermione said. Her voice sounded more normal now, in her own ears.

  "Well..." Harry said. The boy reached over her own outstretched arm, his robes brushing hers, and tapped the artist's illustration of an ominously glowing red stone dripping scarlet liquid. "Problem one is that there's no logical reason why the same artifact would be able to transmute lead to gold and produce an elixir that kept someone young. I wonder if there's an official name for that in the literature? Like the 'turned up to eleven effect', maybe? If everyone can see a flower, you can't get away with saying flowers are the size of houses. But if you're in a flying saucer cult, since nobody can see the alien mothership anyway, you can say it's the size of a city, or the size of the Moon. Observable things have to be constrained by evidence, but when somebody makes up a story, they can make the story as extreme as they want. So the Philosopher's Stone gives you unlimited gold and eternal life, not because there's a single magical discovery that would produce both of those effects, but because someone made up a story about a super happy thingy."

  "Harry, there's a lot of things in magic that aren't sensible," she said.

  "Granted," said Harry. "But Hermione, problem two is that not even wizards are crazy enough to casually overlook the implications of this. Everyone would be trying to rediscover the formula for the Philosopher's Stone, whole countries would be trying to capture the immortal wizard and get the secret out of him -"

  "It's not a secret." Hermione flipped the page, showing Harry the diagrams. "The instructions are right on the next page. It's just so difficult that only Nicholas Flamel's done it."

  "So entire countries would be trying to kidnap Flamel and force him to make more Stones. Come on, Hermione, even wizards wouldn't hear about immortality and, and," Harry Potter paused, his eloquence apparently failing him, "and just keep going. Humans are crazy, but they're not that crazy!"

  "Not everyone thinks the same way you do, Harry." He did have a point, but... how many different references had she come across to Nicholas Flamel? Besides World's Wealthiest Wizards and Rise and Fall of the Dark Arts, there'd also been Stories of Moderately Ancient Times and Biographies of the Justly Famous...

  "All right then, Professor Quirrell would've kidnapped this Flamel guy. It's what an evil person or a good person or just a selfish person would do if they had any sense. The Defense Professor knows a lot of secrets and he wouldn't miss that one." Harry sighed and looked up; she followed his gaze, but he was apparently just looking at the larger library, the rows and rows and rows of bookcases. "I don't mean to mess with your project," said Harry, "and I certainly don't mean to discourage you, but... Honestly, Hermione, I'm not sure you're going to find any good ideas for making money in a book like this. Like the old joke about how if an economist sees a twenty-pound note lying in the street, they won't bother picking it up, because if it were real, someone else would've picked it up already. Any way of making lots of money that everyone knows about to the point where it's in books like this... you see what I'm saying? It can't be possible for everyone to make a thousand Galleons a month in three easy steps, or everyone would be doing it."

  "So? That wouldn't stop you," Hermione said, her voice now roughening again. "You do impossible things all the time, I bet you've done something impossible in the last week and you didn't bother telling anyone."

  (There was a slight pause, which, if Miss Granger had known, was exactly the length of pause you'd make if you'd fought Mad-Eye Moody and won exactly eight days earlier.)

  "Not in the last seven days, no," Harry said. "Look... part of the trick of doing the impossible is being selective about which impossibilities you challenge, and only trying when you have a special advantage. If there's a money-making method in this book that sounds difficult for a wizard, but it's easy if we can use Dad's old Mac Plus, then we'd have a plan."

  "I know that, Harry," Hermione said, her voice wavering only slightly. "I was looking to see if there was anything here I could figure out how to do. I thought, maybe the difficult part about making a Philosopher's Stone was that the alchemical circle had to be super precise, and I could get it right by using a Muggle microscope -"


  "That's brilliant, Hermione!" The boy rapidly drew his wand, said "Quietus," and then continued after the small noises of the rowdier books had died down. "Even if the Philosopher's Stone is just a myth, the same trick might work for other difficult alchemies -"

  "Well, it can't work," Hermione said. She'd flown across the library to look up the only book on alchemy that wasn't in the Restricted Section. And then - she remembered the crushing letdown, all the sudden hope dissipating like mist. "Because all alchemical circles have to be drawn 'to the fineness of a child's hair', it isn't any finer for some alchemies than others. And wizards have Omnioculars, and I haven't heard of any spells where you use Omnioculars to magnify things and do them exactly. I should've realized that!"

  "Hermione," Harry said seriously, as he started to dig down into the red-velvet pouch again, "don't punish yourself when a bright idea doesn't work out. You've got to go through a lot of flawed ideas to find one that might work. And if you send your brain negative feedback by frowning when you think of a flawed idea, instead of realizing that idea-suggesting is good behavior by your brain to be encouraged, pretty soon you won't think of any ideas at all." Harry put down two heart-shaped chocolates beside the book. "Here, have another chocolate. Besides the one from earlier, I mean. This one is to reinforce your brain for generating a good candidate strategy."

  "I suppose you're right," Hermione said in a small voice, but she didn't touch the chocolate. She started to turn the pages back to 167, where she'd been reading before Harry had come in.

  (Hermione Granger did not require bookmarks, of course.)

  Harry was leaning over slightly, his head almost touching her shoulder, watching the pages as she turned them, as though he might be able to glean valuable information from glimpsing the page for only a quarter-second. Breakfast hadn't been long ago, and she could clearly identify, from the faint scent of his breath, that Harry'd eaten banana pudding for dessert.

  Harry spoke again. "So with all that said... and please take this as a positive reinforcement... did you really try to invent a way to mass-produce immortality so that I could pay off my debt to Lucius Malfoy?"

  "Yes," she said in an even smaller voice. Even when she tried to think like Harry, it seemed she hadn't yet got the knack of it. "So what've you been doing this whole time, Harry?"

  Harry made a disgusted face. "Trying to collect evidence on the whole 'Who Framed Hermione Granger' mystery."

  "I..." Hermione looked up at Harry. "Shouldn't I... be trying to solve my own mystery, though?" It hadn't been her first thought, her first priority, but now that Harry mentioned it...

  "That wouldn't work in this case," Harry said soberly. "There's too many people who'll talk to me and not you... and I'm also sorry to say that some of them made me promise not to talk to anyone else. Sorry, I don't think you can help much on this one."

  "Okay, I guess," Hermione said leadenly. "Fine. You do everything. You gather all the clues and talk to all the suspects while I just sit here in the library. Let me know after it turns out that it was Professor Quirrell who did it."

  "Hermione..." Harry said. "Why is it so important who does what? Shouldn't it be more important to get everything solved, than who solves it?"

  "I guess you're right," Hermione said. She lifted her hands to press up at her eyes. "I guess it doesn't matter any more. Everyone's going to think - I know it's not your fault, Harry, you were - you were being Good, you were a perfect gentleman - but no matter what I do now, they'll all think that I'm just - someone for you to rescue." She paused, and said, with her voice quivering, "And maybe they're right, Harry."

  "Whoa, whoa, hold on there a second -"

  "I can't scare Dementors. I can get Outstandings in Charms class, but I can't scare Dementors."

  "I've got a mysterious dark side!" Harry hissed, after his head turned around to scan the library. (There was one boy in a distant corner, who did look in their direction occasionally, but he would've been too far away to hear anything even without the Quieting Barrier.) "I've got a dark side that definitely isn't a child, and who knows what other crazy magical stuff going on in my head - Professor Quirrell claimed that I become whoever I believe I am - that's all cheating, don't you see, Hermione? There's an arrangement that the school administration made that I'm not supposed to talk about, so that the Boy-Who-Lived could have more time to study every day, I'm cheating and you're still beating me in Charms class. I'm - I'm probably not - the Boy-Who-Lived probably isn't even something that you could properly call a child - and you're still competing with that. Don't you realize, if it wasn't for people paying attention to me, you'd look like the most powerful witch to come along in a century? When you can fight three older bullies by yourself, and win?"

  "I don't know," she said, pressing her hands again over her eyes, with her voice wavering. "All I know is - even if that's all true - nobody's ever going to see me for myself anymore, ever."

  "All right," Harry said after a while. "I see what you mean. Instead of the famous Potter-and-Granger research team, there'll be Harry Potter and his lab assistant. Um... here's an idea. How about if I don't focus on making money for a while? I mean, the debt doesn't come due until I graduate Hogwarts. So you can do it yourself and show the world you've still got it. And if you coincidentally crack the secret of immortality along the way, we'll just call it a bonus."

  The thought of Harry relying on her to come up with a solution seemed... like a crushing burden of responsibility to dump on a poor traumatized twelve-year-old girl, and she wanted to hug him for offering her a way to restore her self-respect as a heroine, and it was what she deserved for being a horrible person and speaking sharply to Harry all the time, when all along he'd been a truer friend to her than she'd ever been to him, and it was good that he still thought she could do things, and...

  "Is there some amazing rational thing you do when your mind's running in all different directions?" she managed.

  "My own approach is usually to identify the different desires, give them names, conceive of them as separate individuals, and let them argue it out inside my head. So far the main persistent ones are my Hufflepuff, Ravenclaw, Gryffindor, and Slytherin sides, my Inner Critic, and my simulated copies of you, Neville, Draco, Professor McGonagall, Professor Flitwick, Professor Quirrell, Dad, Mum, Richard Feynman, and Douglas Hofstadter."

  Hermione considered trying this before her Common Sense warned that it might be a dangerous sort of thing to pretend. "There's a copy of me inside your head?"

  "Of course there is!" Harry said. The boy suddenly looked a bit more vulnerable. "You mean there isn't a copy of me living in your head?"

  There was, she realized; and not only that, it talked in Harry's exact voice.

  "It's rather unnerving now that I think about it," said Hermione. "I do have a copy of you living in my head. It's talking to me right now using your voice, arguing how this is perfectly normal."

  "Good," Harry said seriously. "I mean, I don't see how people could be friends without that."

  She continued reading her book, then, Harry seeming content to watch the pages over her shoulder.

  She'd gotten all the way to number seventy, Katherine Scott, who'd apparently invented a way to turn small animals into lemon tarts, when she finally worked up the courage to speak.

  "Harry?" she said. (She was leaning a bit away from him now, though she didn't realize it.) "If there's a copy of Draco Malfoy in your head, does that mean you're friends with Draco Malfoy?"

  "Well..." Harry said. He sighed. "Yeah, I'd been meaning to talk with you about this anyway. I kind of wish I'd talked to you sooner. Anyway, how can I put this... I was corrupting him?"

  "What do you mean corrupting?"

  "Tempting him to the Light Side of the Force."

  Her mouth just stayed open.

  "You know, like the Emperor and Darth Vader, only in reverse."

  "Draco Malfoy," she said. "Harry, do you have any idea -"

  "Yes."

  "
- the sort of things Malfoy has been saying about me? What he said he'd do to me, as soon as he got the chance? I don't know what he told to you, but Daphne Greengrass told me what Malfoy says when he's in Slytherin. It's unspeakable, Harry! It's unspeakable in the completely literal sense that I can't say it out loud!"

  "When was this?" Harry said. "At the start of the year? Did Daphne say when this was?"

  "No," Hermione said. "Because it doesn't matter when, Harry. Anyone who said things - like Malfoy said - they can't be a good person. It doesn't matter what you tempted him to, he's still a rotten person, because no matter what a good person would never -"

  "You're wrong." Harry said, looking her straight in the eyes. "I can guess what Draco threatened to do to you, because the second time I met him, he talked about doing it to a ten-year-old girl. But don't you see, on the day Draco Malfoy arrived in Hogwarts, he'd spent his whole previous life being raised by Death Eaters. It would've required a supernatural intervention for him to have your morality given his environment -"

  Hermione was shaking her head violently. "No, Harry. Nobody has to tell you that hurting people is wrong, it's not something you don't do because the teacher says it's not allowed, it's something you don't do because - because you can see when people are hurting, don't you know that, Harry?" Her voice was shaking now. "That's not - that's not a rule people follow like the rules for algebra! If you can't see it, if you can't feel it here," her hand slapped down over the center of her chest, not quite where her heart was located, but that didn't matter because it was all really in the brain anyway, "then you just don't have it!"

  The thought came to her, then, that Harry might not have it.

  "There's history books you haven't read," Harry said quietly. "There's books you haven't read yet, Hermione, and they might give you a sense of perspective. A few centuries earlier - I think it was definitely still around in the seventeenth century - it was a popular village entertainment to take a wicker basket, or a bundle, with a dozen live cats in it, and -"