Harry Potter and the Methods of Rationality

by Eliezer Yudkowsky

  "All right, then," Moody said, looking rather sour about it. From within his leather armor, the scarred man took out a black folder. "This is a copy of what Amelia's people put together. She almost certainly knows we've got it, but it's all off the books, that clear? Anyway -"

  And Moody told them who the Department of Magical Law Enforcement thought 'Quirinus Quirrell' really was. A seemingly ordinary Hogwarts student (though talented enough that he'd been only narrowly beaten out for the Head Boy position) who'd gone vacationing in Albania after his graduation, disappeared, returned after 25 years, and then been caught up in the Wizarding War -

  "It was murdering the House of Monroe that made Voldie's name," Moody said. "Until then, he was just another Dark Wizard with delusions of grandeur and Bellatrix Black. But after that -" Moody snorted. "Every fool in the country flocked to serve him. You would've hoped the Wizengamot would turn serious, once they realized Voldie was willing to kill their own sacred selves. And that's just what the bastards did - hope that some other bastard would turn serious. None of the cowards wanted to step in front. It was Monroe, Crouch, Bones, and Longbottom. That was nearly everyone in the Ministry who'd dare say a word that might give Voldie offense."

  "That was how your House came to be ennobled, Mr. Potter," injected the solemn voice of Professor McGonagall. "There is an ancient law that if anyone ends a Most Ancient House, whoever avenges that blood will be made Noble. To be sure, the House of Potter was already older than some lines called Ancient. But yours was titled a Noble House of Britain after the end of the war, in recognition that you had avenged the Most Ancient House of Monroe."

  "Flush of gratitude and all that," Mad-Eye Moody said sourly. "It didn't last, but at least James and Lily got a fancy title and a useless medal to take to their graves. But that's leaving out eight years of complete horror after Monroe disappeared and Regulus Black - he was Monroe's private source in the Death Eaters, we're pretty sure - was executed by Voldie. Like a dam breaking and gore flooding out, drowning the whole country. Albus bloody Dumbledore himself had to step into Monroe's shoes, and that was barely enough for us to survive."

  Harry listened with an odd sense of unreality. Some of it felt right, matched up with observation - especially with the speech Professor Quirrell had made before Christmas - and yet...

  This was Professor Quirrell they were talking about.

  "So that's who the Department thinks is your Defense Professor," Mad-Eye Moody finished up his account. "Now what do you think, son?"

  "Well..." Harry said slowly. It is also possible to have a mask behind the mask. "The obvious next thought is that this 'David Monroe' person died in the war after all, and this is just someone else pretending to be David Monroe pretending to be Quirinus Quirrell."

  "That's obvious?" said Professor McGonagall. "Dear Merlin..."

  "Really, boy?" said Mad-Eye Moody, his blue eye spinning rapidly. "I'd say that's a little... paranoid."

  You don't know Professor Quirrell, Harry did not say. "It's an easy theory to test," Harry said out loud. "Just check whether the Defense Professor remembers something about the war that the real David Monroe would've known. Though I suppose, if he's playing the part of David Monroe pretending to be someone else, he has a good excuse to pretend he's pretending he doesn't know what you're talking about -"

  "A little paranoid," said the scarred man, his voice rising. "Not paranoid enough! CONSTANT VIGILANCE! Think about it, lad - what if the real David Monroe never came back from Albania?"

  There was a pause.

  "I see..." Harry said.

  "Of course you do," Professor McGonagall said. "Don't mind me, please. I'll just sit here quietly going mad."

  "In this line of work, if you survive, you learn that there's three kinds of Dark Wizards," Moody said grimly; his wand wasn't pointed at anyone, it was angled slightly downward, but it was in his hand. It had never left his hand since the moment he'd entered the room. "There's Dark Wizards that have one name. There's Dark Wizards that have two names. And there's Dark Wizards that change names like you and I change clothes. I saw 'Monroe' go through three Death Eaters like he was snapping twigs. There's not many wizards that good at age forty-five. Dumbledore, maybe, but not many others."

  "Perhaps that is true," said the Potions Master from where he was lurking. "But what of it, Mad-Eye? Whatever his identity, Monroe was surely the Dark Lord's enemy. I've heard Death Eaters curse his name even after they thought him dead. They feared him well."

  "So far as Defense Professors are concerned," Professor McGonagall said primly, "I shall take it and be grateful."

  Moody swung around to glare at her. "Just where the devil was 'Monroe' all those years he was gone, eh? Maybe he thought he could make a name for himself in Britain by opposing Voldie, and vanished away when he found out he was wrong. Then why'd he come back now, hah? What's his new plan?"

  "He, ah..." Harry ventured tentatively. "He says he always wanted to be a great Defense Professor because all the best fighting wizards have taught at Hogwarts. And he kind of is being an incredibly good Defense Professor, actually... I mean, if he just wanted to keep up a disguise, he could get away with much sloppier work..."

  Professor McGonagall was nodding firmly.

  "Naive," Moody said flatly. "I suppose you all haven't wondered if your Defense Professor set up the whole House of Monroe to be wiped out?"

  "What?" cried Professor McGonagall.

  "Our mystery wizard hears about a missing kid from a Most Ancient House of Britain," Moody said. "Steps into the shoes of 'David Monroe', but stays away from the real Monroe family. But eventually the House is bound to notice something wrong. So this imposter somehow prods Voldie into wiping them all out - maybe leaked a password they'd given him for their wards - and then he was a Lord of the Wizengamot!"

  There seemed to be a fight going on inside Harry's mind between Hufflepuff One, who'd never trusted the Defense Professor in the first place; and Hufflepuff Two, who was far too loyal to Harry's friend, Professor Quirrell, to believe something like that just because Moody said so.

  It is kind of obvious, though, observed his Slytherin part. I mean, do you actually believe that under natural circumstances, anyone would end up as the last heir to a Most Ancient House AND Lord Voldemort killed his family AND he has to avenge his martial arts sensei? If anything I'd say he went too far over the top in setting up his new identity as the ideal literary hero. That sort of thing doesn't happen in real life.

  This from an orphan who was raised unaware of his heritage, commented Harry's Inner Critic. With a prophecy about him. You know, I don't think we've ever read a story about two equally destined heroes competing to see who's cliched enough to take down the villain -

  Yes, replied the central Harry over the distant vroop-ing noise in the background, it's a very sad life we lead and YOU'RE NOT HELPING.

  There's only one thing to do at this point, said Ravenclaw. And we all know what it is, so why argue?

  But, Harry replied, how do we test experimentally whether or not Professor Quirrell is the original David Monroe? I mean, what sort of observable behaves differently, depending on whether he's the real David Monroe or an impostor?

  "What do you want me to do about it, Mad-Eye?" Professor McGonagall was demanding. "I can't -"

  "You can," the scarred man said, glaring at her fiercely. "Just fire the bloody Defense Professor."

  "You say that every year," said Professor McGonagall.

  "Yes, and I'm always right!"

  "Constant vigilance or no, Alastor, the students must be taught!"

  Moody snorted. "Pfah! I swear the curse gets worse every year, as you lot get more and more reluctant to let them go. Your precious Professor Quirrell would have to be Grindelwald in disguise, to get himself sent off!"

  "Is he?" Harry couldn't help asking. "I mean, could he actually be -"

  "I check Grindie's cell every two months," Moody said. "He was there in March."

  "Could t
he person in the cell be a ringer?"

  "I administer a blood test for his identity, son."

  "Where do you keep the blood you use as a reference?"

  "In a safe place." Something like a smile was stretching the scarred lips. "Have you considered the Auror Office after you graduate?"

  "Alastor," Professor McGonagall said reluctantly. "The Defense Professor does have a... health condition. I suppose you will call it suspicious in itself - but it is by no means certain that it will be any ill-doing on his part which prevents us from renewing his employment."

  "Yes, his little naptimes," Moody said darkly. "Amelia thinks he stepped into the path of a high-level curse. Sounds to me more like a Dark ritual gone wrong!"

  "You've no proof of that!" Professor McGonagall said.

  "That man might as well be wearing a sign saying 'Dark Wizard' in glowing green letters over his head."

  "Ah..." Harry said. It didn't seem like an especially good time to ask what Mr. Moody thought of the 'not all sacrificial rituals are evil' standpoint. "Excuse me, but you said earlier that Professor Quirrell - I mean the old David Monroe - I mean the Monroe from the seventies - anyway, you said that person used the Killing Curse. What does that imply? Does somebody have to be a Dark Wizard to use it?"

  Moody shook his head. "I've used it myself. All it takes is power and a certain mood." The grimacing lips were showing teeth. "The first time I cast it was against a wizard named Gerald Grice, and you can ask me what he did after you graduate Hogwarts."

  "But why is it Unforgiveable, then?" Harry said. "I mean, a Cutting Hex can kill someone too. So why's it any better to use a Reducto instead of Avada Kedav-"

  "Shut your mouth!" Moody said sharply. "Someone might take it the wrong way, your saying that incantation. You look too young to cast it, but there's such a thing as Polyjuice. And to answer your question, boy, there's two reasons why that spell's in the blackest book. The first is that the Killing Curse strikes directly at the soul, and it'll just keep going until it hits one. Straight through shields. Straight through walls. There's a reason why even Aurors fighting Death Eaters weren't allowed to use it before the Monroe Act."

  "Ah," said Harry. "That does seem like an excellent reason to ban -"

  "I'm not finished, son. The second reason is that the Killing Curse doesn't just take a powerful bit of magic. You've got to mean it. You've got to want someone dead, and not for the greater good, either. Killing Grice didn't bring back Blair Roche, or Nathan Rehfuss, or David Capito. It wasn't for justice, or to stop him doing it again. I wanted him dead. You understand now, lad? You don't have to be a Dark Wizard to use that spell - but you can't be Albus Dumbledore, either. And if you're arrested for killing with it, there's no possible defense."

  "I... see," murmured the Boy-Who-Lived. You can't want the person dead as an instrumental value on the way to some positive future consequence, you can't cast it if you believe it's a necessary evil, you have to actually want them dead for the sake of being dead, as a terminal value in your utility function. "A magically embodied preference for death over life, striking within the plane of pure life force... that does sound like a difficult spell to block."

  "Not difficult," Moody snapped. "Impossible."

  Harry nodded gravely. "But David Monroe - or whoever - used the Killing Curse against a couple of Death Eaters even before they wiped out his family. Does that mean he already had to hate them? Like, the martial arts story was probably true?"

  Moody shook his head slightly. "One of the dark truths of the Killing Curse, son, is that once you've cast it the first time, it doesn't take much hate to do it again."

  "It damages the mind?"

  Again Moody shook his head. "No. It's the killing that does that. Murder tears the soul - but that's just the same if it's a Cutting Hex. The Killing Curse doesn't crack your soul. It just takes a cracked soul to cast." If there was a sad expression on the scarred face, it could not be read. "But that doesn't tell us much about Monroe. The ones like Dumbledore who'll never be able to cast the Curse all their lives, because they never crack no matter what - they're the rare ones, very rare. It only takes a little cracking."

  There was a strange heavy feeling in Harry's chest. He'd wondered what exactly it had meant, that Lily Potter had tried to cast the Killing Curse at Lord Voldemort with her last breath. But surely it was forgiveable, it was right and proper for a mother to hate the Dark Wizard who was coming to kill her baby, mocking her for how she couldn't stop him. There was something wrong with you as a parent if you couldn't cast Avada Kedavra, in that situation. And no other spell could've gone past the Dark Lord's shields; you'd have to at least try to hate the Dark Lord enough to want him dead for the sake of dead, if that was the only way to save your baby.

  It only takes a little cracking...

  "Enough," said Professor McGonagall. "What would you have us do?"

  Moody's smile twisted. "Get rid of the Defense Professor and see if all your troubles mysteriously clear up. Bet you a Galleon they do."

  Professor McGonagall looked like she was in pain. "Alastor - but - will you teach the classes, if -"

  "Ha!" said Moody. "If I ever say yes to that question, check me for Polyjuice, because it's not me."

  "I'll test it experimentally," Harry said. And then, as everyone looked at him, "I'll ask Professor Quirrell a question that the real David Monroe would know - like who else was in the Slytherin class of 1945, or something like that - hopefully without making it obvious. It won't be definitive proof, he could've studied the role, but it would be evidence. Still, Mr. Moody, even if Professor Quirrell isn't the original Monroe, I'm not sure that getting rid of him is a free action. He saved my life twice -"

  "What?" demanded Moody. "When? How?"

  "Once when he knocked down a bunch of witches who were summoning me toward the ground, once when he figured out that the Dementor was draining me through my wand. And if Professor Quirrell wasn't the one who set up Draco Malfoy in the first place, then he saved Draco Malfoy's life, and things would be a lot worse if he hadn't. If the Defense Professor isn't behind it all - he's not someone we can afford to just get rid of."

  Professor McGonagall nodded firmly.

  Hypothesis: Severus Snape

  (April 8th, 1992, 9:03pm)

  Harry and Professor McGonagall now stood on the slowly turning stairs, turning without descending; or at least one Harry stood upon those stairs - his other three selves had been left behind in the Headmaster's office.

  "Can I ask you a private question?" Harry said, when he thought they were far enough away not to be heard. "And in particular, private from the Headmaster."

  "Yes," Professor McGonagall said, not quite sighing. "Though I hope you realize that I cannot do anything which conflicts with my duties to -"

  "Yes," Harry said, "that's exactly what I need to ask you about. In front of the Wizengamot, when Lucius Malfoy was saying that Hermione was no part of House Potter and that he wouldn't take the money, you told Hermione how to swear that oath. I want to know, if something like that comes up again, if your first duty is to the Hogwarts student Hermione Granger, or to the head of the Order of the Phoenix, Albus Dumbledore."

  Professor McGonagall looked like someone had hit her in the face with a cast-iron frying-pan, a few minutes earlier, and now she'd been told that somebody was about to do it again, and not to flinch.

  Harry flinched a little himself. Somewhere along the line he needed to pick up the knack of not phrasing things to hit as hard as he possibly could.

  The walls rotated around them, behind them, and somehow, they descended.

  "Oh, Mr. Potter," Professor McGonagall said with a low exhalation. "I... wish you wouldn't ask me such questions... oh, Harry, I wasn't thinking then, not at all. I only saw a chance to help Miss Granger and... I was Sorted into Gryffindor, after all."

  "You've got a chance to think now," Harry said. It was all coming out wrong, but he had to say it anyway, because - "I'm not asking you
to be loyal to me. But if you do know - if you are sure - what you'll do if it comes down to an innocent Hogwarts student versus the Order of the Phoenix a second time..."

  But Professor McGonagall shook her head. "I'm not sure," the Transfiguration Professor whispered. "I don't know if it was the right choice even then. I'm sorry. I can't decide such awful things!"

  "But you'll do something if it happens again," Harry said. "Indecision is also a choice. You can't just imagine having to make an immediate decision?"

  "No," Professor McGonagall said, sounding a little stronger; and Harry realized that he'd accidentally offered a way out. The Professor's next words confirmed Harry's fears. "Such a dreadful choice as that, Mr. Potter - I think I should not make it until I must."

  Harry gave an internal sigh. He supposed he had no right to expect Professor McGonagall to say anything else. In a moral dilemma where you lost something either way, making the choice would feel bad either way, so you could temporarily save yourself a little mental pain by refusing to decide. At the cost of not being able to plan anything in advance, and at the cost of incurring a huge bias toward inaction or waiting until too late... but you couldn't expect a witch to know all that. "All right," Harry said.

  Though it wasn't right at all, not really. Dumbledore might want that debt removed, Professor Quirrell would also want Harry out of that debt. And if the Defense Professor was David Monroe, or could convincingly appear to be David Monroe, then Lord Voldemort technically hadn't exterminated the House of Monroe. In which case somebody might be able to pass a Wizengamot resolution revoking the Noble status of House Potter, which had been granted for avenging the Most Ancient House of Monroe.

  In which case Hermione's vow of service to a Noble House might be null and void.

  Or maybe not. Harry didn't know anything about the legalities, especially not whether House Potter got the money back if someone managed to send Hermione to Azkaban. Just because you lost something might not mean the payment was returned, legally speaking. Harry wasn't sure and he didn't dare ask a magical solicitor...