Harry Potter and the Methods of Rationality

I've found this fantastic fanfiction, called Harry Potter and the Methods of Rationality, which asks what would be different about the Harry Potter universe if Harry had been raised by a scientist instead of by Vernon Dursely? I'm only a few chapters in, but here are some of my favorite quotes so far:


McGonagall turned into a cat.


Harry scrambled back unthinkingly, backpedaling so fast that he tripped over a stray stack of books and landed hard on his bottom with a thwack. His hands came down to catch himself without quite reaching properly, and there was a warning twinge in his shoulder as the weight came down unbraced.


At once the small tabby cat morphed back up into a robed woman. "I'm sorry, Mr. Potter," McGonagall said, sounding sincere, though her lips were twitching toward a smile. "I should have warned you."


Harry was breathing in short pants. His voice came out choked. "You can't DO that!"


"It's only a Transfiguration," said McGonagall. "An Animagus transformation, to be exact."


"You turned into a cat! A SMALL cat! You violated Conservation of Energy! That's not just an arbitrary rule, it's implied by the form of the quantum Hamiltonian! Rejecting it destroys unitarity and then you get FTL signaling! And cats are COMPLICATED! A human mind can't just visualize a whole cat's anatomy and, and all the cat biochemistry, and what about the neurology? How can you go on thinking using a cat-sized brain?"


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"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 watch?"


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An old woman's face peered out from above the neighboring 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.


The part of his mind that wasn't convinced was screaming conspiracy! at the top of its lungs. She's in on it too!


The other part of him noted, much more matter-of-factly, she was probably put here to watch you.