Harry Potter and the Methods of Rationality

Usually Harry was pretty good at answering that question, but in this particular case, he had no clue what his brain was thinking.

Harry mentally shrugged. A flat metal plate on a door affords pushing, and a handle on a door affords pulling, and the thing to do with a testable hypothesis is to go and test it.

He took a piece of lined paper from his desk, and started writing.

Dear Deputy Headmistress

Harry paused, reflecting; then discarded the paper for another, tapping another millimetre of graphite from his mechanical pencil. This called for careful calligraphy.

Dear Deputy Headmistress Minerva McGonagall,

Or Whomsoever It May Concern:

I recently received your letter of acceptance to Hogwarts, addressed to Mr. H. Potter. You may not be aware that my genetic parents, James Potter and Lily Potter (formerly Lily Evans) are dead. I was adopted by Lily's sister, Petunia Evans-Verres, and her husband, Michael Verres-Evans.

I am extremely interested in attending Hogwarts, conditional on such a place actually existing. Only my mother Petunia says she knows about magic, and she can't use it herself. My father is highly sceptical. I myself am uncertain. I also don't know where to obtain any of the books or equipment listed in your acceptance letter.

Mother mentioned that you sent a Hogwarts representative to Lily Potter (then Lily Evans) in order to demonstrate to her family that magic was real, and, I presume, help Lily obtain her school materials. If you could do this for my own family it would be extremely helpful.

Sincerely,

Harry James Potter-Evans-Verres.

Harry added their current address, then folded up the letter and put it in an envelope, which he addressed to Hogwarts. Further consideration led him to obtain a candle and drip wax onto the flap of the envelope, into which, using a penknife's tip, he impressed the initials H.J.P.E.V. If he was going to descend into this madness, he was going to do it with style.

Then he opened his door and went back downstairs. His father was sitting in the living-room and reading a book of higher maths to show how smart he was; and his mother was in the kitchen preparing one of his father's favourite meals to show how loving she was. It didn't look like they were talking to one another at all. As scary as arguments could be, not arguing was somehow much worse.

"Mum," Harry said into the unnerving silence, "I'm going to test the hypothesis. According to your theory, how do I send an owl to Hogwarts?"

His mother turned from the kitchen sink to stare at him, looking shocked. "I - I don't know, I think you just have to own a magic owl."

That should've sounded highly suspicious, oh, so there's no way to test your theory then, but the peculiar certainty in Harry seemed willing to stick its neck out even further.

"Well, the letter got here somehow," Harry said, "so I'll just wave it around outside and call 'letter for Hogwarts!' and see if an owl picks it up. Dad, do you want to come and watch?"

His father shook his head minutely and kept on reading. Of course, Harry thought to himself. Magic was a disgraceful thing that only stupid people believed in; if his father went so far as to test the hypothesis, or even watch it being tested, that would feel like associating himself with that...

Only as Harry stumped out the back door, into the back garden, did it occur to him that if an owl did come down and snatch the letter, he was going to have some trouble telling Dad about it.

But - well - that can't really happen, can it? No matter what my brain seems to believe. If an owl really comes down and grabs this envelope, I'm going to have worries a lot more important than what Dad thinks.

Harry took a deep breath, and raised the envelope into the air.

He swallowed.

Calling out Letter for Hogwarts! while holding an envelope high in the air in the middle of your own back garden was... actually pretty embarrassing, now that he thought about it.

No. I'm better than Dad. I will use the scientific method even if it makes me feel stupid.

"Letter -" Harry said, but it actually came out as more of a whispered croak.

Harry steeled his will, and shouted into the empty sky, "Letter for Hogwarts! Can I get an owl? "

"Harry?" asked a bemused woman's voice, one of the neighbours.

Harry pulled down his hand like it was on fire and hid the envelope behind his back like it was drug money. His whole face was hot with shame.

An old woman's face peered out from above the neighbouring fence, grizzled grey hair escaping from her hairnet. Mrs. Figg, the occasional babysitter. "What are you doing, Harry?"

"Nothing," Harry said in a strangled voice. "Just - testing a really silly theory -"

"Did you get your acceptance letter from Hogwarts?"

Harry froze in place.

"Yes," Harry's lips said a little while later. "I got a letter from Hogwarts. They say they want my owl by the