Harry Potter and the Methods of Rationality

Well, he had - Harry glanced at his watch - one whole hour to figure it out, since he was supposed to be on the train at eleven. Maybe this was the equivalent of an IQ test and the stupid kids couldn't become wizards. (And the amount of extra time you gave yourself would determine your Conscientiousness, which was the second most important factor in scholarly success.)

"I'll figure it out," Harry said to his waiting parents. "It's probably some sort of test thingy."

His father frowned. "Hm... maybe look for a trail of mixed footprints on the ground, leading somewhere that doesn't seem to make sense -"

"Dad!" Harry said. "Stop that! I haven't even tried to figure it out on my own!" It was a very good suggestion, too, which was worse.

"Sorry," his father apologised.

"Ah..." Harry's mother said. "I don't think they would do that to a student, do you? Are you sure Professor McGonagall didn't tell you anything?"

"Maybe she was distracted," Harry said without thinking.

"Harry!" hissed his father and mother in unison. "What did you do? "

"I, um -" Harry swallowed. "Look, we don't have time for this now -"

"Harry!"

"I mean it! We don't have time for this now! Because it's a really long story and I've got to figure out how to get to school!"

His mother had a hand over her face. "How bad was it?"

"I, ah," I can't talk about that for reasons of National Security, "about half as bad as the Incident with the Science Project?"

"Harry!"

"I, er, oh look there are some people with an owl I'll go ask them how to get in!" and Harry ran away from his parents towards the family of fiery redheads, his trunk automatically slithering behind him.

The plump woman looked to him as he arrived. "Hello, dear. First time at Hogwarts? Ron's new, too -" and then she peered closely at him. "Harry Potter?"

Four boys and a red-headed girl and an owl all swung around and then froze in place.

"Oh, come on!" Harry protested. He'd been planning to go as Harry Verres at least until he got to Hogwarts. "I bought a sweatband and everything! How come you know who I am?"

"Yes," Harry's father said, coming up behind him with long easy strides, "how do you know who he is?" His voice indicated a certain dread.

"Your picture was in the newspapers," said one of two identical-looking twins.

"HARRY!"

"Dad! It's not like that! It's 'cause I defeated the Dark Lord You-Know-Who when I was one year old!"

"WHAT?"

"Mum can explain."

"WHAT?"

"Ah... Michael dear, there are certain things I thought it would be best not to bother you with until now -"

"Excuse me," Harry said to the redheaded family who were all staring at him, "but it would be quite extremely helpful if you could tell me how to get to Platform Nine and Three Quarters right now."

"Ah..." said the woman. She raised a hand and pointed at the wall between platforms. "Just walk straight at the barrier between platforms nine and ten. Don't stop and don't be scared you'll crash into it, that's very important. Best do it at a bit of a run if you're nervous."

"And whatever you do, don't think of an elephant."

"George! Ignore him, Harry dear, there's no reason not to think of an elephant."

"I'm Fred, Mum, not George -"

"Thanks!" Harry said and took off at a run towards the barrier -

Wait a minute, it wouldn't work unless he believed in it?

It was at times like this that Harry hated his mind for actually working fast enough to realise that this was a case where "resonant doubt" applied, that is, if he'd started out thinking that he would go through the barrier he'd have been fine, only now he was worried about whether he sufficiently believed he'd go through the barrier, which meant that he actually was worried about crashing into it -

"Harry! Get back here, you have some explaining to do!" That was his Dad.

Harry shut his eyes and ignored everything he knew about justified credibility and just tried to believe really hard that he'd go through the barrier and -

- the sounds around him changed.

Harry opened his eyes and stumbled to a halt, feeling vaguely dirtied by having made a deliberate effort to believe something.