Eliezer Yudkowsky - Harry Potter and the Methods of Rationality

Everything that made life worth living.

His wand rose into the starting position for the Patronus Charm.

Harry thought of the stars, the image that had almost held off the Dementor even without a Patronus. Only this time, Harry added the missing ingredient, he'd never truly seen it but he'd seen the pictures and the video. The Earth, blazing blue and white with reflected sunlight as it hung in space, amid the black void and the brilliant points of light. It belonged there, within that image, because it was what gave everything else its meaning. The Earth was what made the stars significant, made them more than uncontrolled fusion reactions, because it was Earth that would someday colonize the galaxy, and fulfill the promise of the night sky.

Would they still be plagued by Dementors, the children's children's children, the distant descendants of humankind as they strode from star to star? No. Of course not. The Dementors were only little nuisances, paling into nothingness in the light of that promise; not unkillable, not invincible, not even close. You had to put up with little nuisances, if you were one of the lucky and unlucky few to be born on Earth; on Ancient Earth, as it would be remembered someday. That too was part of what it meant to be alive, if you were one of the tiny handful of sentient beings born into the beginning of all things, before intelligent life had come fully into its power. That the much vaster future depended on what you did here, now, in the earliest days of dawn, when there was still so much darkness to be fought, and temporary nuisances like Dementors.

Mum and Dad, Hermione's friendship and Draco's journey, Neville and Seamus and Lavender and Dean, the blue sky and brilliant Sun and all bright things, the Earth, the stars, the promise, everything humanity was and everything it would become...

On the wand, Harry's fingers moved into their starting positions; he was ready, now, to think the right sort of warm and happy thought.

And Harry's eyes stared directly at that which lay beneath the tattered cloak, looked straight at that which had been named Dementor. The void, the emptiness, the hole in the universe, the absence of color and space, the open drain through which warmth poured out of the world.

The fear it exuded stole away all happy thoughts, its closeness drained your power and strength, its kiss would destroy everything that you were.

I know you now , Harry thought as his wand twitched once, twice, thrice and four times, as his fingers slid exactly the right distances, I comprehend your nature, you symbolize Death, through some law of magic you are a shadow that Death casts into the world.

And Death is not something I will ever embrace.

It is only a childish thing, that the human species has not yet outgrown.

And someday...

We'll get over it...

And people won't have to say goodbye any more...

The wand rose up and leveled straight at the Dementor.

"EXPECTO PATRONUM!"

The thought exploded from him like a breaking dam, surged down his arm into his wand, burst from it as blazing white light. Light that became corporeal, took on shape and substance.

A figure with two arms, two legs, and a head, standing upright; the animal Homo sapiens, the shape of a human being.

Glowing brighter and brighter as Harry poured all his strength into his spell, blazing with incandescent light brighter than the fading sunset, the Aurors and Professor Quirrell shielding their eyes in shock -

And someday when the descendants of humanity have spread from star to star, they won't tell the children about the history of Ancient Earth until they're old enough to bear it; and when they learn they'll weep to hear that such a thing as Death had ever once existed!

The figure of a human shone more brilliant now than the noonday Sun, so radiant that Harry could feel the warmth of it on his skin; and Harry sent out all his defiance at the shadow of Death, opening all the floodgates inside him to make that bright shape blaze even brighter and yet brighter.

You are not invincible, and someday the human species will end you.

I will end you if I can, by the power of mind and magic and science.

I won't cower in fear of Death, not while I have a chance of winning.

I won't let Death touch me, I won't let Death touch the ones I love.

And even if you do end me before I end you,

Another will take my place, and another,

Until the wound in the world is healed at last...

Harry lowered his wand, and the bright figure of a human faded away.

Slowly, he exhaled.

Like waking up from a dream, like opening his eyes after sleep, Harry's gaze moved away from the cage, he looked around and saw that everyone was staring at him.

Albus Dumbledore was staring at him.

Professor Quirrell was staring at him.

The Auror trio was staring at him.

They were all looking at him like they'd just seen him destroy a Dementor.

The tattered cloak lay empty within the cage.

The last tip of the Sun was sinking below the horizon, the red light fading from the treetops, only the blue sky illuminating the six people standing upon the winter-dried and snow-spotted grass, near a vacant cage on whose floor lay an empty, tattered cloak.

Harry felt... well, normal again. Sane-ish. The spell hadn't undone the day and its damage, hadn't made the injuries as if they had never been, but his hurts had been... bandaged, meliorated? It was hard to describe.

Dumbledore was also looking healthier, though not fully restored. The old wizard's head turned for a moment, locked eyes with Professor Quirrell, then looked back to Harry. "Harry," Dumbledore said, "are you about to collapse in exhaustion and possibly die?"

"No, strangely enough," Harry said. "That took something out of me, but a lot less than I thought it would." Or maybe it gave something back, as well as taking... "Honestly, I expected my body to be hitting the ground with a thud about now."

There was a distinct body-hitting-the-ground-with-a-thuddish sort of sound.

"Thank you for taking care of that, Quirinus," said Dumbledore to Professor Quirrell, who was now standing above and behind the unconscious forms of the three Aurors. "I confess I am still feeling a bit peaky. Though I shall handle the Memory Charms myself."

Professor Quirrell inclined his head, and then looked at Harry. "I will omit a good deal of useless incredulity," said Professor Quirrell, "remarks to the effect that Merlin himself failed to do that, et cetera. Let us go straight to asking the important question. What the sweet slithering snakes was that? "

"The Patronus Charm," Harry said. "Version 2.0."

"I rejoice to see that you are your usual self again," said Dumbledore. "But you are not going anywhere , young Ravenclaw, until you tell me what exactly was that warm and happy thought."

"Hm..." said Harry. He tapped a contemplative finger on his cheek. "I wonder if I should?"

Professor Quirrell suddenly grinned.

"Please?" said the Headmaster. "Pretty please with sugar on top?"

Harry felt an impulse and decided to go with it. It was dangerous, but there might not ever be a better opportunity until the end of time.

"Three sodas," Harry said to his pouch, then looked up at the Defense Professor and the Headmaster of Hogwarts. "Gentlemen," Harry said, "I bought these sodas on my first visit to Platform Nine and Three-Quarters, on the day I entered into Hogwarts. I have been saving them for special occasions; there is a minor enchantment on them to ensure they are drunk at the right time. This is the last of my supply, but I do not think there will ever come a finer occasion. Shall we?"