Eliezer Yudkowsky - Harry Potter and the Methods of Rationality

Sprout, to offer her a conspiracy. My first attempt at suasion failed. I Obliviated her and tried again with a new presentation. The second bait failed. The third bait failed. The tenth bait failed. I was so frustrated that I began going through my entire library of guises, including those more appropriate to Mr. Zabini. Still nothing worked. The child would not violate her childish code.”

“ You do not get to call her childish, Professor.” Harry’s voice sounded strange in his own ears. “Her code worked. It prevented you from tricking her. The whole point of having deontological ethical injunctions is that arguments for violating them are often much less trustworthy than they look. You don’t get to criticize her rules when they worked exactly as intended.” After they resurrected Hermione, Harry would tell her that Lord Voldemort himself hadn’t been able to tempt her into doing wrong, and that was why he’d killed her.

“Fair enough, I suppose,” said Professor Quirrell. “There is a saying that even a stopped clock is right twice a day, and I do not think Miss Granger was actually being reasonable. Still, Rule Ten: one must not rant about the opposition’s unworthiness after they have foiled you. Regardless. After two full hours of failed attempts, I realized that I was being over-stubborn, and that I did not need Miss Granger to carry out the exact part I had planned for her. I gave up on my original intent, and instead imbued Miss Granger with False Memories of watching Mr. Malfoy plotting against her under circumstances that implied she should not tell you or the authorities. In the end it was Mr. Malfoy who gave me the opening I needed, entirely by luck.” Professor Quirrell dropped a bellflower and a scrap of parchment into the cauldron.

“Why did the wards show the Defense Professor as having killed Hermione?”

“I wore the mountain troll as a false tooth while Dumbledore was identifying me to the Hogwarts wards as the Defense Professor.” A slight smile. “Other living weapons cannot be Transfigured; they will not survive the disenchantment for the requisite six hours to avoid being traced by Time-Turner. The fact that a mountain troll was used as a weapon of assassination was a clear sign that the assassin had needed a proxy weapon that could be Transfigured safely. Combined with the evidence of the wards, and Dumbledore’s own knowledge of how he had identified me to Hogwarts, you could have deduced who was responsible—in theory. However, experience has taught me that such puzzles are far harder to solve when you do not already know the solution, and I considered it a small risk. Ah, that reminds me, I have a question of my own.” The Defense Professor was now giving Harry an intent look. “What gave me away at the last, in the corridor outside these chambers?”

Harry put aside other emotions to weigh up the cost and benefit of answering honestly, came to the conclusion that the Defense Professor was giving away far more information than he was getting ( why? ) and that it was best not to give the appearance of reticence. “The main thing,” Harry said, “was that it was too improbable that everyone had arrived in Dumbledore’s corridor at the same time. I tried running with the hypothesis that everyone who arrived had to be coordinated, including you.”

“But I had said that I was following Snape,” the Defense Professor said. “Was that not plausible?”

“It was, but…” Harry said. “Um. The laws governing what constitutes a good explanation don’t talk about plausible excuses you hear afterward. They talk about the probabilities we assign in advance. That’s why science makes people do advance predictions, instead of trusting explanations people come up with afterward. And I wouldn’t have predicted in advance for you to follow Snape and show up like that. Even if I’d known in advance that you could put a trace on Snape’s wand, I wouldn’t have expected you to do it and follow him just then. Since your explanation didn’t make me feel like I would have predicted the outcome in advance, it remained an improbability. I started to wonder if Sprout’s mastermind might have arranged for you to show up, too. And then I realised the note to myself hadn’t really come from future-me, and that gave it away completely.”

“Ah,” said the Defense Professor, and sighed. “Well, I think it is all working out for the best. You did understand only too late; and there would have been inconveniences as well as benefits to you remaining unaware.”

“What on Earth were you trying to do? The reason I was trying so hard to figure it out was that the whole thing was just so weird.”

“That should have pointed at Dumbledore, not myself,” said Professor Quirrell, and frowned. “The fact is that Miss Greengrass was not supposed to arrive in that corridor for several hours… though I suppose, since I did have Mr. Malfoy give her the clue I assigned her, it is not too surprising they banded together. Had Mr. Nott arrived seemingly alone, events would have played out less farcically. But I consider myself a specialist in battlefield control magics, and I was able to ensure that the fight went as I wished. I suppose it did end up looking a bit ridiculous.” The Defense Professor dropped a peach slice and a bellflower into the cauldron. “But let us defer our discussion of the Mirror until we reach it. Did you have any more questions concerning Miss Granger’s regrettable and hopefully temporary demise?”

“Yes,” Harry said in an even voice. “What did you do to the Weasley twins? Dumbledore thought—I mean, the school saw the Headmaster go to the Weasley twins after Hermione was arrested. Dumbledore thought you, as Voldemort, had wondered why Dumbledore had done so, and that you’d checked on the Weasley twins, found and took their map, and Obliviated them afterward?”

“Dumbledore was quite correct,” Professor Quirrell said, shaking his head as though in wonderment. “He was also an utter fool to leave the Hogwarts Map in the possession of those two idiots. I had an unpleasant shock after I recovered the Map; it showed my name and yours correctly! The Weasley idiots had thought it a mere malfunction, especially after you received your Cloak and your Time-Turner. If Dumbledore had kept the Map himself—if the Weasleys had ever spoken of it to Dumbledore— but they did not, thankfully.” Showed my name and yours correctly— “I would like to see that,” Harry said.

Without taking his eyes from the cauldron, Professor Quirrell drew a folded parchment from within his robes, hissed at it “ Sshow our ssurroundingss ”, and tossed the folded parchment toward Harry. It cut unerringly through the air, an increase of doom breathing on Harry’s senses as it moved toward him, and then it fluttered gently to Harry’s feet.

Harry picked up the parchment and unfolded it.

At first the parchment seemed blank. Then, as though an unseen pen were moving across it, the outline of walls and doors appeared, all drawn in handwritten lines. The writing outlined a series of chambers, most of them shown as empty; the last chamber in the series had a confused scribble in its center, as though the Map were trying to indicate its own bewilderment; and the second-to-last chamber showed two names within, written in positions within the chamber corresponding to where Harry was sitting and Professor Quirrell was standing.

Tom M. Riddle.

Tom M. Riddle.

Harry gazed at the parchment, an unpleasant chill coming over him.

It was one thing to hear Lord Voldemort claim that your name was Tom Riddle; it was another thing to find that Hogwarts’s magic agreed. “ Did you tamper with thiss map to achieve thiss ressult, or did it appear before you by ssurprisse? ”