Harry Potter and the Methods of Rationality

bizarre, noisy gidgets. Clearly visible from where Harry had perched himself on his chair's arm was a truncated- conical object, like a cone with its top snipped off, slowly spinning around a pulsating central light which it shaded but did not obscure; and each time the inner light pulsated, the assembly made a vroop-vroop- vroop sound that sounded oddly distant, muffled like it was coming from behind four solid walls, even though the spinning-conical-section thingy was only a meter or two away.

Vroop... vroop... vroop...

And then there were the various still-breathing bodies of Harry Potter he'd stashed in one quiet corner, cleaning up a mess that was his own in more ways than one. (Only one body wasn't inside a copy of the Invisibility Cloak; but then it merely took a small effort of concentration for Harry to perceive his other selves beneath the Cloak of which he was master - an effort which Harry had carefully not put forth earlier, to avoid getting advance temporal information he wanted to determine by his own decision.) The sad thing was that by this point, having his own body visibly lying in a corner didn't seem all that crazy. It was just... Hogwarts.

"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