Harry Potter and the Methods of Rationality

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 mechanics being normal and them being weird.)

Harry had shown his mother the healer's kit he'd bought to keep in their house, though most of the potions wouldn't work on Dad. Mum had stared at the kit in a way that made Harry ask whether Mum's sister had ever bought anything like that for Grandpa Edwin and Grandma Elaine. And when Mum still hadn't answered, Harry had said hastily that she must have just never thought of it. And then, finally, he'd fled the room.

Lily Evans probably hadn't thought of it, that was the sad thing. Harry knew that other people had a tendency to not-think about painful subjects, in the same way they had a tendency not to deliberately rest their hands on red-hot stove burners; and Harry was starting to suspect that most Muggleborns rapidly acquired a tendency to not-think about their family, who were all going to die before they reached their first century anyway.

Not that Harry had any intention of letting that happen, of course.

And then it was late in the day on December 24th and they were driving off for their Christmas Eve dinner.

The house was huge, not by Hogwarts standards, but certainly by the standards of what you could get if your father was a distinguished professor trying to live in Oxford. Two stories of brick gleaming in the setting sun, with windows on top of windows and one tall window that went up much further than glass should go, that was going to be one huge living room...

Harry took a deep breath, and rang the doorbell.

There was a distant call of 'Honey, can you get it?'

This was followed by a slow patter of approaching steps.

And then the door opened to reveal a genial man, of fat and rosy cheeks and thinning hair, in a blue button- down shirt straining slightly at the seams.

'Dr. Granger?' Harry's father said briskly, before Harry could even speak. 'I'm Michael, and this is Petunia and our son Harry. The food's in the magical trunk,' and Dad made a vague gesture behind him - not quite in the direction of the trunk, as it happened.

'Yes, please, come in,' said Leo Granger. He stepped forward and took the wine bottle from the Professor's outstretched hands, with a muttered 'Thank you,' and then stepped back and waved at the living room. 'Have a seat. And,' his head turning down to address Harry, 'all the toys are downstairs in the basement, I'm sure Herm will be down shortly, it's the first door on your right,' and pointed toward a hallway.

Harry just looked at him for a moment, conscious that he was blocking his parents from coming in.

'Toys?' said Harry in a bright, high-pitched voice, with his eyes wide. 'I love toys!'

There was an intake of breath from his mother behind him, and Harry strode into the house, managing not to stomp too hard as he walked.

The living room was every bit as large as it had looked from outside, with a huge vaulted ceiling dangling a gigantic chandelier, and a Christmas tree that must have been murder to maneuver through the door. The lower levels of the tree were thoroughly and carefully decorated in neat patterns of red and green and gold, with a newfound sprinkling of blue and bronze; the heights that only a grownup could reach were carelessly, randomly draped with strings of lights and wreaths of tinsel. A hallway extended until it terminated in the cabinetry of a kitchen, and wooden stairs with polished metal railings stretched up toward a second floor.

'Gosh!' Harry said. 'This is a big house! I hope I don't get lost in here!'

Dr. Roberta Granger was feeling rather nervous as dinner approached. The turkey and the roast, their own contributions to the common project, were steadily cooking away in the oven; the other dishes were to be brought by their guests, the Verres family, who had adopted a boy named Harry. Who was known to the wizarding world as the Boy-Who-Lived. And who was also the only boy that Hermione had ever called 'cute', or noticed at all, really.

The Verreses had said that Hermione was the only child in Harry's age group whose existence their son had ever acknowledged in any way whatsoever.

And it might've been jumping the gun just a little; but both couples had a sneaking suspicion that wedding bells might be in the offing a few years down the road.

So while Christmas Day would be spent, as always, with her husband's family, they'd decided to spend Christmas Eve meeting their daughter's possible future in-laws.

The doorbell rang while she was right in the middle of basting the turkey, and she raised her voice and shouted, 'Honey, can you get it?'

There was a brief groan of a chair and its occupant, and then there was the sound of her husband's heavy footsteps and the door swinging open.

'Dr. Granger?' said an older man's brisk voice. 'I'm Michael, and this is Petunia and our son Harry. The food's in