Harry Potter and the Methods of Rationality

glad when Professor Quirrell had turned out to be so easily fooled.

'I do hope those five Galleons will be enough to last, since you counted them so carefully,' said Professor Quirrell. 'I doubt the Headmaster shall be so eager to entrust me with your vault key a second time, once he discovers I've been tricked.'

'I'm sure you did your best,' Harry said with deep gratitude.

'Do you need any assistance finding a safe place to store all those Knuts, Mr. Potter?'

'Well, sort of,' said Harry. 'Do you know of any good investment opportunities, Professor Quirrell?'

And the two of them walked on, in their tiny sphere of silence and isolation, through the brilliant and bustling crowds; and if you looked carefully, you would see that where they went, leafy boughs faded, and flowers withered, and children's toys that played cheerful bells changed to lower and more ominous notes.

Harry did notice, but he didn't say anything, just smiled a little to himself.

Everyone had their own way of celebrating the holidays, and the Grinch was as much a part of Christmas as Santa.

Chapter 33: Coordination Problems, Pt 1

I just recite to myself, over and over, until I can choose sleep: It all adds up to J. K. Rowling.

The version of decision theory used in this chapter is not the academically dominant one. It's based on something called 'timeless decision theory' that's under development by (among others) Gary Drescher, Wei Dai, Vladimir Nesov, and, well... (coughs a few times) me.

The terrifying part was how fast the whole thing had spiraled out of control.

'Albus,' Minerva said, not even trying to keep the worry out of her voice as the two of them entered the Great Hall, 'something has to be done.'

The atmosphere at Hogwarts before Yuletide was usually bright and cheerful. The Great Hall had already been decorated in green and red, after a Slytherin and a Gryffindor whose Yule wedding had become a symbol of friendship transcending Houses and allegiances, a tradition almost as ancient as Hogwarts itself and which had even spread to Muggle countries.

Now the students eating dinner were glancing nervously over their shoulders, or sending vicious glares at other tables, or at some tables arguing heatedly. You could have described the atmosphere as tense, perhaps, but the phrase coming to Minerva's mind was fifth degree of caution.

Take a school, into four Houses divided...

Now into each year, add three armies at war.

And the partisanship of Dragon and Sunshine and Chaos had spread beyond the first-years; they had become the armies for those who had no armies. Students were wearing armbands with insignia of fire or smile or upraised hand, and hexing each other in the corridors. All three first-year generals had told them to stop - even Draco Malfoy had heard her out and then nodded grimly - but their supposed followers hadn't listened.

Dumbledore gazed out at the tables with a distant look. 'In every city,' the old wizard quoted softly,'the population has been divided for a long time past into the Blue and the Green factions... And they fight against their opponents knowing not for what end they imperil themselves... So there grows up in them against their fellow men a hostility which has no cause, and at no time does it cease or disappear, for it gives place neither to the ties of marriage nor of relationship nor of friendship, and the case is the same even though those who differ with respect to these colours be brothers or any other kin. I, for my part, am unable to call this anything except a disease of the soul...'

'I'm sorry,' said Minerva, 'I don't -'

'Procopius,' said Dumbledore. 'They took their chariot-racing very seriously, in the Roman Empire. Yes, Minerva, I agree that something must be done.'

'Soon,' Minerva said, her voice lowering even further. 'Albus, I think it must be done before Saturday.'

On Sunday, most students would leave Hogwarts to stay the holiday with their families; Saturday, then, was the final battle of the three first-year armies that would determine the awarding of Professor Quirrell's thrice-cursed Christmas wish.

Dumbledore glanced over at her, studying her gravely. 'You fear that the explosion will come then, and someone will be hurt.'

Minerva nodded.

'And that Professor Quirrell will be blamed.'

Minerva nodded again, her face tight. She had long since become wise in the ways that Defense Professors were fired. 'Albus,' Minerva said, 'we cannot lose Professor Quirrell now, we cannot! If he but stays through January our fifth-years will pass their OWLs, if he stays through March our seventh-years will pass their NEWTs, he is remedying years of neglect in months, a whole generation will grow up able to defend themselves in spite of the Dark Lord's curse - you must stop the battle, Albus! Ban the armies now!'

'I am not sure the Defense Professor would take that kindly,' said Dumbledore, glancing over toward the Head Table where Quirrell was drooling into his soup. 'He did seem most attached to his armies, though when I agreed I thought there would be four in each year.' The old wizard sighed. 'A clever man, probably with the best of intentions; but perhaps not clever enough, I fear. And to ban the armies might also trigger the explosion.'

'But then Albus, what will you do?'

The old wizard favored her with a benign smile. 'Why, I shall plot, of course. It's the new fashion in Hogwarts.'

And they had come too close to the Head Table for Minerva to say anything more.

The terrifying part was how fast the whole thing had spiraled out of control.

The first battle in December had been... messy, or so Draco had heard.