Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  Harry's father, Professor Michael Verres-Evans, rolled his eyes. "Yes, Harry."

  "And you, Mum, your theory says that the professor should be able to do this, and if that doesn't happen, you'll admit you're mistaken. Nothing about how magic doesn't work when people are sceptical of it, or anything like that."

  Deputy Headmistress Minerva McGonagall was watching Harry with a bemused expression. She looked quite witchy in her black robes and pointed hat, but when she spoke she sounded formal and Scottish, which didn't go together with the look at all. At first glance she looked like someone who ought to cackle and put babies into cauldrons, but the whole effect was ruined as soon as she opened her mouth. "Is that sufficient, Mr. Potter?" she said. "Shall I go ahead and demonstrate?"

  "Sufficient? Probably not," Harry said. "But at least it will help. Go ahead, Deputy Headmistress."

  "Just Professor will do," said she, and then, "Wingardium Leviosa."

  Harry looked at his father.

  "Huh," Harry said.

  His father looked back at him. "Huh," his father echoed.

  Then Professor Verres-Evans looked back at Professor McGonagall. "All right, you can put me down now."

  His father was lowered carefully to the ground.

  Harry ruffled a hand through his own hair. Maybe it was just that strange part of him which had already been convinced, but... "That's a bit of an anticlimax," Harry said. "You'd think there'd be some kind of more dramatic mental event associated with updating on an observation of infinitesimal probability -" Harry stopped himself. Mum, the witch, and even his Dad were giving him that look again. "I mean, with finding out that everything I believe is false."

  Seriously, it should have been more dramatic. His brain ought to have been flushing its entire current stock of hypotheses about the universe, none of which allowed this to happen. But instead his brain just seemed to be going, All right, I saw the Hogwarts Professor wave her wand and make your father rise into the air, now what?

  The witch-lady was smiling benevolently upon them, looking quite amused. "Would you like a further demonstration, Mr. Potter?"

  "You don't have to," Harry said. "We've performed a definitive experiment. But..." Harry hesitated. He couldn't help himself. Actually, under the circumstances, he shouldn't be helping himself. It was right and proper to be curious. "What else can you do?"

  Professor McGonagall turned into a cat.

  Harry scrambled back unthinkingly, backpedalling so fast that he tripped over a stray stack of books and landed hard on his bottom with a thwack. His hands came down to catch himself without quite reaching properly, and there was a warning twinge in his shoulder as the weight came down unbraced.

  At once the small tabby cat morphed back up into a robed woman. "I'm sorry, Mr. Potter," said the witch, sounding sincere, though the corners of her lips were twitching upwards. "I should have warned you."

  Harry was breathing in short gasps. His voice came out choked. "You can't DO that!"

  "It's only a Transfiguration," said Professor McGonagall. "An Animagus transformation, to be exact."

  "You turned into a cat! A SMALL cat! You violated Conservation of Energy! That's not just an arbitrary rule, it's implied by the form of the quantum Hamiltonian! Rejecting it destroys unitarity and then you get FTL signalling! And cats are COMPLICATED! A human mind can't just visualise a whole cat's anatomy and, and all the cat biochemistry, and what about the neurology? How can you go on thinking using a cat-sized brain?"

  Professor McGonagall's lips were twitching harder now. "Magic."

  "Magic isn't enough to do that! You'd have to be a god!"

  Professor McGonagall blinked. "That's the first time I've ever been called that."

  A blur was coming over Harry's vision, as his brain started to comprehend what had just broken. The whole idea of a unified universe with mathematically regular laws, that was what had been flushed down the toilet; the whole notion of physics. Three thousand years of resolving big complicated things into smaller pieces, discovering that the music of the planets was the same tune as a falling apple, finding that the true laws were perfectly universal and had no exceptions anywhere and took the form of simple maths governing the smallest parts, not to mention that the mind was the brain and the brain was made of neurons, a brain was what a person was -

  And then a woman turned into a cat, so much for all that.

  A hundred questions fought for priority over Harry's lips and the winner poured out: "And, and what kind of incantation is Wingardium Leviosa? Who invents the words to these spells, nursery schoolers?"

  "That will do, Mr. Potter," Professor McGonagall said crisply, though her eyes shone with suppressed amusement. "If you wish to learn about magic, I suggest that we finalise the paperwork so that you can go to Hogwarts."

  "Right," Harry said, somewhat dazed. He pulled his thoughts together. The March of Reason would just have to start over, that was all; they still had the experimental method and that was the important thing. "How do I get to Hogwarts, then?"

  A choked laugh escaped Professor McGonagall, as if extracted from her by tweezers.

  "Hold on a moment, Harry," his father said. "Remember why you haven't been going to school up until now? What about your condition?"

  Professor McGonagall spun to face Michael. "His condition? What's this?"

  "I don't sleep right," Harry said. He waved his hands helplessly. "My sleep cycle is twenty-six hours long, I always go to sleep two hours later, every day. I can't fall asleep any earlier than that, and then the next day I go to sleep two hours later than that. 10PM, 12AM, 2AM, 4AM, until it goes around the clock. Even if I try to wake up early, it makes no difference and I'm a wreck that whole day. That's why I haven't been going to a normal school up until now."

  "One of the reasons," said his mother. Harry shot her a glare.

  McGonagall gave a long hmmmmm. "I can't recall hearing about such a condition before..." she said slowly. "I'll check with Madam Pomfrey to see if she knows any remedies." Then her face brightened. "No, I'm sure this won't be a problem - I'll find a solution in time. Now," and her gaze sharpened again, "what are these other reasons?"

  Harry sent his parents a glare. "I am a conscientious objector to child conscription, on grounds that I should not have to suffer for a disintegrating school system's failure to provide teachers or study materials of even minimally adequate quality."

  Both of Harry's parents howled with laughter at that, like they thought it was all a big joke. "Oh," said Harry's father, eyes bright, "is that why you bit a maths teacher in third year."

  "She didn't know what a logarithm was!"

  "Of course," seconded Harry's mother. "Biting her was a very mature response to that."

  Harry's father nodded. "A well-considered policy for addressing the problem of teachers who don't understand logarithms."

  "I was seven years old! How long are you going to keep on bringing that up?"

  "I know," said his mother sympathetically, "you bite one maths teacher and they never let you forget it, do they?"

  Harry turned to Professor McGonagall. "There! You see what I have to deal with?"

  "Excuse me," said Petunia, and fled through the backdoor into the garden, from which her screams of laughter were clearly audible.

  "There, ah, there," Professor McGonagall seemed to be having trouble speaking for some reason, "there is to be no biting of teachers at Hogwarts, is that quite clear, Mr. Potter?"

  Harry scowled at her. "Fine, I won't bite anyone who doesn't bite me first."

  Professor Michael Verres-Evans also had to leave the room briefly upon hearing that.

  "Well," Professor McGonagall sighed, after Harry's parents had composed themselves and returned. "Well. I think, under the circumstances, that I should avoid taking you to purchase your study materials until a day or two before school begins."

  "What? Why? The other children already know magic, don't they? I have to start catching up right away!"

&nbs
p; "Rest assured, Mr. Potter," replied Professor McGonagall, "Hogwarts is quite capable of teaching the basics. And I suspect, Mr. Potter, that if I leave you alone for two months with your schoolbooks, even without a wand, I will return to this house only to find a crater billowing purple smoke, a depopulated city surrounding it and a plague of flaming zebras terrorising what remains of England."

  Harry's mother and father nodded in perfect unison.

  "Mum! Dad!"

  Chapter 3: Comparing Reality To Its Alternatives

  If J. K. Rowling asks you about this story, you know nothing.

  "But then the question is - who?"

  "Good Lord," said the barman, peering at Harry, "is this - can this be -?"

  Harry leaned towards the bar of the Leaky Cauldron as best he could, though it came up to somewhere around the tips of his eyebrows. A question like that deserved his very best.

  "Am I - could I be - maybe - you never know - if I'm not - but then the question is - who?"

  "Bless my soul," whispered the old barman. "Harry Potter... what an honour."

  Harry blinked, then rallied. "Well, yes, you're quite perceptive; most people don't realise that so quickly -"

  "That's enough," Professor McGonagall said. Her hand tightened on Harry's shoulder. "Don't pester the boy, Tom, he's new to all this."

  "But it is him?" quavered an old woman. "It's Harry Potter?" With a scraping sound, she got up from her chair.

  "Doris -" McGonagall said warningly. The glare she shot around the room should have been enough to intimidate anyone.

  "I only want to shake his hand," the woman whispered. She bent low and stuck out a wrinkled hand, which Harry, feeling confused and more uncomfortable than he ever had in his life, carefully shook. Tears fell from the woman's eyes onto their clasped hands. "My granson was an Auror," she whispered to him. "Died in seventy-nine. Thank you, Harry Potter. Thank heavens for you."

  "You're welcome," Harry said automatically, and then he turned his head and shot Professor McGonagall a frightened, pleading look.

  Professor McGonagall slammed her foot down just as the general rush was about to start. It made a noise that gave Harry a new referent for the phrase "Crack of Doom", and everyone froze in place.

  "We're in a hurry," Professor McGonagall said in a voice that sounded perfectly, utterly normal.

  They left the bar without any trouble.

  "Professor?" Harry said, once they were in the courtyard. He had meant to ask what was going on, but oddly found himself asking an entirely different question instead. "Who was that pale man, by the corner? The man with the twitching eye?"

  "Hm?" said Professor McGonagall, sounding a bit surprised; perhaps she hadn't expected that question either. "That was Professor Quirinus Quirrell. He'll be teaching Defence Against the Dark Arts this year at Hogwarts."

  "I had the strangest feeling that I knew him..." Harry rubbed his forehead. "And that I shouldn't ought to shake his hand." Like meeting someone who had been a friend, once, before something went drastically wrong... that wasn't really it at all, but Harry couldn't find words. "And what was... all of that?"

  Professor McGonagall was giving him an odd glance. "Mr. Potter... do you know... how much have you been told... about how your parents died?"

  Harry returned a steady look. "My parents are alive and well, and they always refused to talk about how my genetic parents died. From which I infer that it wasn't good."

  "An admirable loyalty," said Professor McGonagall. Her voice went low. "Though it hurts a little to hear you say it like that. Lily and James were friends of mine."

  Harry looked away, suddenly ashamed. "I'm sorry," he said in a small voice. "But I have a Mum and Dad. And I know that I'd just make myself unhappy by comparing that reality to... something perfect that I built up in my imagination."

  "That is amazingly wise of you," Professor McGonagall said quietly. "But your genetic parents died very well indeed, protecting you."

  Protecting me?

  Something strange clutched at Harry's heart. "What... did happen?"

  Professor McGonagall sighed. Her wand tapped Harry's forehead, and his vision blurred for a moment. "Something of a disguise," she said, "so that this doesn't happen again, not until you're ready." Then her wand licked out again, and tapped three times on a brick wall...

  ...which hollowed into a hole, and dilated and expanded and shivered into a huge archway, revealing a long row of shops with signs advertising cauldrons and dragon livers.

  Harry didn't blink. It wasn't like anyone was turning into a cat.

  And they walked forwards, together, into the wizarding world.

  There were merchants hawking Bounce Boots ("Made with real Flubber!") and "Knives +3! Forks +2! Spoons with a +4 bonus!" There were goggles that would turn anything you looked at green, and a lineup of comfy armchairs with ejection seats for emergencies.

  Harry's head kept rotating, rotating like it was trying to wind itself off his neck. It was like walking through the magical items section of an Advanced Dungeons and Dragons rulebook (he didn't play the game, but he did enjoy reading the rulebooks). Harry desperately didn't want to miss a single item for sale, in case it was one of the three you needed to complete the cycle of infinite wish spells.

  Then Harry spotted something that made him, entirely without thinking, veer off from the Deputy Headmistress and start heading straight into the shop, a front of blue bricks with bronze-metal trim. He was brought back to reality only when Professor McGonagall stepped right in front of him.

  "Mr. Potter?" she said.

  Harry blinked, then realised what he'd just done. "I'm sorry! I forgot for a moment that I was with you instead of my family." Harry gestured at the shop window, which displayed fiery letters that shone piercingly bright and yet remote, spelling out Bigbam's Brilliant Books. "When you walk past a bookshop you haven't visited before, you have to go in and look around. That's the family rule."

  "That is the most Ravenclaw thing I have ever heard."

  "What?"

  "Nothing. Mr. Potter, our first step is to visit Gringotts, the bank of the wizarding world. Your genetic family vault is there, with the inheritance your genetic parents left you, and you'll need money for school supplies." She sighed. "And, I suppose, a certain amount of spending money for books could be excused as well. Though you might want to hold off for a time. Hogwarts has quite a large library on magical subjects. And the tower in which, I strongly suspect, you will be living, has a more broad-ranging library of its own. Any book you bought now would probably be a duplicate."

  Harry nodded, and they walked on.

  "Don't get me wrong, it's a great distraction," Harry said as his head kept swivelling, "probably the best distraction anyone has ever tried on me, but don't think I've forgotten about our pending discussion."

  Professor McGonagall sighed. "Your parents - or your mother at any rate - may have been very wise not to tell you."

  "So you wish that I could continue in blissful ignorance? There is a certain flaw in that plan, Professor McGonagall."

  "I suppose it would be rather pointless," the witch said tightly, "when anyone on the street could tell you the story. Very well."

  And she told him of He-Who-Must-Not-Be-Named, the Dark Lord, Voldemort.

  "Voldemort?" Harry whispered. It should have been funny, but it wasn't. The name burned with a cold feeling, ruthlessness, diamond clarity, a hammer of pure titanium descending upon an anvil of yielding flesh. A chill swept over Harry even as he pronounced the word, and he resolved then and there to use safer terms like You-Know-Who.

  The Dark Lord had raged upon wizarding Britain like a wilding wolf, tearing and rending at the fabric of their everyday lives. Other countries had wrung their hands but hesitated to intervene, whether out of apathetic selfishness or simple fear, for whichever was first among them to oppose the Dark Lord, their peace would be the next target of his terror.

  (The bystander effect, thought Harry, thinking of Latan
e and Darley's experiment which had shown that you were more likely to get help if you had an epileptic fit in front of one person than in front of three. Diffusion of responsibility, everyone hoping that someone else would go first.)

  The Death Eaters had followed in the Dark Lord's wake and in his vanguard, carrion vultures to pick at wounds, or snakes to bite and weaken. The Death Eaters were not as terrible as the Dark Lord, but they were terrible, and they were many. And the Death Eaters wielded more than wands; there was wealth within those masked ranks, and political power, and secrets held in blackmail, to paralyse a society trying to protect itself.

  An old and respected journalist, Yermy Wibble, called for increased taxes and conscription. He shouted that it was absurd for the many to cower in fear of the few. His skin, only his skin, had been found nailed to the newsroom wall that next morning, next to the skins of his wife and two daughters. Everyone wished for something more to be done, and no one dared take the lead to propose it. Whoever stood out the most became the next example.

  Until the names of James and Lily Potter rose to the top of that list.

  And those two might have died with their wands in their hands and not regretted their choices, for they were heroes; but for that they had an infant child, their son, Harry Potter.

  Tears were coming into Harry's eyes. He wiped them away in anger or maybe desperation, I didn't know those people, not really, they aren't my parents now, it would be pointless to feel so sad for them -

  When Harry was done sobbing into the witch's robes, he looked up, and felt a little bit better to see tears in Professor McGonagall's eyes as well.

  "So what happened?" Harry said, his voice trembling.

  "The Dark Lord came to Godric's Hollow," Professor McGonagall said in a whisper. "You should have been hidden, but you were betrayed. The Dark Lord killed James, and he killed Lily, and he came in the end to you, to your cot. He cast the Killing Curse at you, and that was where it ended. The Killing Curse is formed of pure hate, and strikes directly at the soul, severing it from the body. It cannot be blocked, and whomever it strikes, they die. But you survived. You are the only person ever to survive. The Killing Curse rebounded and struck the Dark Lord, leaving only the burnt hulk of his body and a scar upon your forehead. That was the end of the terror, and we were free. That, Harry Potter, is why people want to see the scar on your forehead, and why they want to shake your hand."