Harry Potter and the Methods of Rationality

least, as wide as Harry had ever seen it, wider than when a new grant came in, or when one of his students got a position, and you couldn't ask for a wider smile than that.

Mum was blinking hard, and she was trying to smile but not doing a very good job.

"So!" said his father as he came striding up. "Made any revolutionary discoveries yet?"

Of course Dad thought he was joking.

It hadn't hurt quite so much when his parents didn't believe in him, back when no one else had believed in him either, back when Harry hadn't known how it felt to be taken seriously by people like Headmaster Dumbledore and Professor Quirrell.

And that was when Harry realized that the Boy-Who-Lived only existed in magical Britain, that there wasn't any such person in Muggle London, just a cute little eleven-year-old boy going home for Christmas.

"Excuse me," Harry said, his voice trembling, "I'm going to break down and cry now, it doesn't mean there was anything wrong at school."

Harry started to move forward, and then stopped, torn between hugging his father and hugging his mother, he didn't want either one to feel slighted or that Harry loved them more than the other -

"You," said his father, "are a very silly boy, Mr. Verres," and he gently took Harry by the shoulders and pushed him into the arms of his mother, who was kneeling down, tears already streaking her cheek.

"Hello, Mum," Harry said with his voice wavering, "I'm back." And he hugged her, amid the noisy mechanical sounds and the smell of burned gasoline; and Harry started crying, because he knew that nothing could go back, least of all him.

The sky was completely dark, and stars were coming out, by the time they negotiated the Christmas traffic to the university town that was Oxford, and parked in the driveway of the small, dingy-looking old house that their family used to keep the rain off their books.

As they walked up the brief stretch of pavement leading to the front door, they passed a series of flower-pots holding small, dim electric lights (dim since they had to recharge themselves off solar power during the day), and the lights lit up just as they passed. The hard part had been finding motion sensors that were waterproof and triggered at just the right distance...

In Hogwarts there were real torches like that.

And then the front door opened and Harry stepped into their living-room, blinking hard.

Every inch of wall space is covered by a bookcase. Each bookcase has six shelves, going almost to the ceiling. Some bookshelves are stacked to the brim with hardcover books: science, math, history, and everything else. Other shelves have two layers of paperback science fiction, with the back layer of books propped up on old tissue boxes or two-by-fours, so that you can see the back layer of books above the books in front. And it still isn't enough. Books are overflowing onto the tables and the sofas and making little heaps under the windows...

The Verres household was just as he'd left it, only with more books, which was also just how he'd left it.

And a Christmas tree, naked and undecorated just two days before Christmas Eve, which threw Harry briefly before he realized, with a warm feeling blossoming in his chest, that of course his parents had waited.

"We took the bed out of your room to make room for more bookcases," said his father. "You can sleep in your trunk, right?"

"You can sleep in my trunk," said Harry.

"That reminds me," said his father. "What did they end up doing about your sleep cycle?"

"Magic," Harry said, making a beeline for the door that opened upon his bedroom, just in case Dad wasn't joking...

"That's not an explanation!" said Professor Verres-Evans, just as Harry shouted, "You used up all the open space on my bookcases?"

Harry had spent the 23rd of December shopping for Muggle things that he couldn't just Transfigure; his father had been busy and had said that Harry would need to walk or take the bus, which had suited Harry just fine. Some of the people at the hardware store had given Harry questioning looks, but he'd said with an innocent voice that his father was shopping nearby and was very busy and had sent him to get some things (holding up a list in carefully adult-looking half-illegible handwriting); and in the end, money was money.

They had all decorated the Christmas tree together, and Harry had put a tiny dancing fairy on top (two Sickles, five Knuts at Gambol & Japes).

Gringotts had readily exchanged Galleons for paper money, but they didn't seem to have any simple way to turn larger quantities of gold into tax-free, unsuspicious Muggle money in a numbered Swiss bank account. This had rather spiked Harry's plan to turn most of the money he'd self-stolen into a sensible mix of 60% international index funds and 40% Berkshire Hathaway. For the moment, Harry had diversified his assets a little further by sneaking out late at night, invisible and Time-Turned, and burying one hundred golden Galleons in the backyard. He'd always always always wanted to do that anyway.

Some of December 24th had been spent with the Professor reading Harry's books and asking questions. Most of the experiments his father had suggested were impractical, at least for the moment; of those remaining, Harry had done many of them already. ("Yes, Dad, I checked what happened if Hermione was given a changed pronunciation and she didn't know whether it was changed, that was the very first experiment I did, Dad!")

The last question Harry's father had asked, looking up from Magical Draughts and Potions with an expression of bewildered disgust, was whether it all made sense if you were a wizard; and Harry had answered no.

Whereupon his father had declared that magic was unscientific.

Harry was still a little shocked at the idea of pointing to a section of reality and calling it unscientific. Dad seemed to think that the conflict between his intuitions and the universe meant that the universe had a problem.

(Then again, there were lots of physicists who thought that quantum mechanics was weird, instead of quantum