Eliezer Yudkowsky - Harry Potter and the Methods of Rationality

His dark side had also noticed, when it was looking through the entire room for anything that could possibly be used as a weapon, that the enemy had been foolish enough to bring a Dementor into Harry's presence. That was a powerful weapon indeed, and one that Harry might wield better than its supposed masters. There had been a time in Azkaban when Harry had told twelve Dementors to turn and go, and they had gone.

The Dementors are Death, and the Patronus Charm works by thinking about happy thoughts instead of Death.

If Harry's theory was correct, that one sentence would be all it took to pop the Aurors' Patronus Charms like a soap bubble, and ensure that nobody within reach of his voice could cast another one.

I am going to cancel the Patronus Charms and prevent any more Patronuses from being cast. And then my Dementor, flying faster than any broomstick, is going to Kiss everyone here who voted to send a twelve-year-old girl to Azkaban.

Say that, to set up the if-then expectation, and wait for people to understand and laugh. Then speak the fatal truth; and when the Aurors' Patronuses winked out to prove the point, either people's anticipations of the mindless void, or Harry's threat of its destruction, would make the Dementor obey. Those who had sought to compromise with the darkness would be consumed by it.

It was the other solution his dark side had devised.

Ignoring the gasps rising from behind him, Harry crossed the radius of the Patronuses, strode to a single pace from Death. Its unhindered fear burst around him like a whirlpool, like stepping next to the sucking drain of some huge bathtub emptying out its water; but with the false Patronuses no longer obscuring the level on which they interacted, Harry could reach the Dementor even as it could reach him. Harry looked straight into the pulling vacuum and -

the Earth among the stars

all his triumph at saving Hermione

someday the reality of which you are a shadow will cease to exist

Harry took all the silver emotion that fueled his Patronus Charm and shoved it at the Dementor; and expected Death's shadow to flee from him -

- and as Harry did that, he flung his hands up and shouted "BOO!"

The void retreated sharply away from Harry until it came up against the dark stone behind.

In the hall there was a deathly silence.

Harry turned his back on the empty void, and looked up at where the toad-woman stood. She was pale beneath the pink makeup, her mouth opening and closing like a fish.

"I make you this one offer," said the Boy-Who-Lived. "I never learn that you've been interfering with me or any of mine. And you never find out why the unkillable soul-eating monster is scared of me. Now sit down and shut up."

The toad-woman fell back down to her bench without a word.

Harry looked further up.

"A riddle, Lord Malfoy!" the Boy-Who-Lived shouted across the Most Ancient Hall. "I know you weren't in Ravenclaw, but try to answer this one anyway! What destroys Dark Lords, frightens Dementors, and owes you sixty thousand Galleons?"

For an instant Lord Malfoy stood there with eyes slightly widened; then his face fell back into calm scorn, and his voice spoke coolly in reply. "Are you openly threatening me, Mr. Potter?"

"I'm not threatening you," said the Boy-Who-Lived. "I'm scaring you. There's a difference."

"Enough, Mr. Potter," said Professor McGonagall. "We shall be late for afternoon Transfiguration as it is. And do come back here, you're still terrifying that poor Dementor." She turned to the Aurors. "Mr. Kleiner, if you would!"

Harry strode back to them, as the Auror addressed moved forward and pressed a short rod of dark metal to the dark metal chair, muttering an inaudible word of dismissal.

The chains slithered back as smoothly as they had come forth; and Hermione pushed herself out of the chair as fast as she could, and half-ran and half-staggered forward a few steps.

Harry held out his arms -

- and Hermione half-jumped half-fell into Professor McGonagall's arms, beginning to sob hysterically.

Hmpfh, said a voice inside Harry. I kind of thought we'd earned that one ourselves.

Oh, shut up.

Professor McGonagall was holding Hermione so firmly that you might have thought it was a mother holding her daughter, or maybe granddaughter. After a few moments Hermione's sobs slowed, and then stopped. Professor McGonagall suddenly shifted her stance and grabbed onto her more tightly; the girl's hands were dangling limply, now, and her eyes were closed -

"She'll be fine, Mr. Potter," Professor McGonagall said softly in Harry's direction, without looking at him. "She just needs a few hours in one of Madam Pomfrey's beds."

"All right, then," Harry said. "Let's get her to Madam Pomfrey's."

"Yes," said Dumbledore, as he descended to the bottom of the dark stone stairs. "Let us all go home, indeed." His blue eyes were locked on Harry, as hard as sapphires.

The Lords and Ladies of the Wizengamot are departing their wooden benches, leaving as they came, looking rather nervous.

The vast majority are thinking 'The Dementor was frightened of the Boy-Who-Lived!'

Some of the shrewder ones are already wondering how this will affect the delicate power balance of the Wizengamot - if a new piece has appeared upon the gameboard.

Almost none are thinking anything along the lines of 'I wonder how he did that.'

This is the truth of the Wizengamot: Many are nobles, many are wealthy magnates of business, a few came by their status in other ways. Some of them are stupid. Most are shrewd in the realms of business and politics, but their shrewdness is circumscribed. Almost none have walked the path of a powerful wizard. They have not read through ancient books, scrutinized old scrolls, searching for truths too powerful to walk openly and disguised in conundrums, hunting for true magic among a hundred fantastic fairy tales. When they are not looking at a contract of debt, they abandon what shrewdness they possess and relax with some comfortable nonsense. They believe in the Deathly Hallows, but they also believe that Merlin fought the dread Totoro and imprisoned the Ree. They know (because that too is part of the standard legend) that a powerful wizard must learn to distinguish the truth among a hundred plausible lies. But it has not occurred to them that they might do the same.

(Why not? Why, indeed, would wizards with enough status and wealth to turn their hands to almost any endeavor, choose to spend their lives fighting over lucrative monopolies on ink importation? The Headmaster of Hogwarts would hardly see the question; of course most people should not be powerful wizards, just as most people should not be heroes. The Defense Professor could explain at great and cynical length why their ambitions are so trivial; to him, too, there is no puzzle. Only Harry Potter, for all the books he has read, is unable to understand; to the Boy-Who-Lived the life choices of the Lords and Ladies seem incomprehensible - not what a good person would do, nor yet an evil person either. Now which of the three is most wise?)

For whatever reason, then, most of the Wizengamot has never walked the path that leads to powerful wizardry; they do not seek out what is hidden. For them, there is no why. There is no explanation. There is no causality. The Boy-Who-Lived, who was already halfway into the magisterium of legend, has now been promoted all the way there; and it is a brute fact, simple and unexplained, that the Boy-Who-Lived frightens Dementors. Ten years earlier they were told that a one-year-old boy defeated the most terrible Dark Lord of their generation, perhaps the most evil Dark Lord ever to live; and they just accepted that too.