Harry Potter and the Methods of Rationality

I’ve just finished reading Eliezer Yudkowsky’s magnum opus Harry Potter and the Methods of Rationality, for the second time and it is amazing. Off the top of my head I think it’s the only novel I’ve read twice in one year, the first time because I couldn’t put it down, and the second time to find all the details I missed while eagerly following the story the first time. Like the Rowling canon, there’s a lot more depth here than you notice the first time through. It’s the only HP fanfic that I’ve found as compelling, maybe more compelling, than the original.

There are two ways I can think of to explain this story. The obvious one is that it’s an alternate history of the Potterverse in which Harry’s Aunt Petunia convinces her sister to magically make her beautiful. As a result instead of marrying Vernon Dursley, she marries physicist Michael Verres. Consequently instead of growing up in a closet under the stairs, Harry grows up as a doted-upon only child of way above average intelligence. But the more accurate description is a story in which Harry Potter is replaced by Ender Wiggin.

Warning: major spoilers follow.

Differences from Canon

As I said, the major departure from established events is when Lily Evans uses magic to make Petunia beautiful. Most of the differences from canon can be derived from that, especially her marriage to Michael Verres and the loving and intellectually curious household that Harry grows up in until his letter from Hogwarts arrives.

Furthermore, you really do have to accept that the character of Harry in this fanfic is completely different from the character of Harry in canon. They are really two very different people. This Harry is more like Ender Wiggin; and like Ender he’s smarter, wiser, and more learned way beyond what any actual 11-year old ever is or ever could be. As in Ender’s Game, the real supernatural power here is the protagonist’s extreme intelligence, cunning, and learning. One of the things that makes the original series so compelling is that Harry acts and thinks like an 11 year old in the Sorcerer’s Stone and grows up through the series. That’s lost here because when the story opens Harry is in many ways already wiser and more mature than 99% of the magical world. Heck, he’s wiser and more mature than 99% of people in our real Muggle world. As Mcgonagall says on p. 49, “In all my life I’ve never met anyone else like you. Sometimes you just don’t seem eleven years old or even all that human.”

Beyond that there are a few other differences from the canonical story that, I think, all occur after Lily casts her spell on Petunia. Thus you could invoke the Butterfly Effect to explain them, but they aren’t obviously caused by Lily’s spell and its consequences. Specifically:

  • During the war, Dumbledore may have burned Narcissa Malfoy to death in her bed; and if he didn’t someone did. Or the whole thing was faked for as yet unrevealed reasons. In any case, Draco grew up without a mother.
  • During the war, the Death Eaters kidnapped Aberforth and tortured him to death when Albus wouldn’t pay his ransom.
  • Peter Pettigrew probably did not go into hiding as the Weasleys’ rat; or, if he did, he switched in a real rat before Harry arrives at Hogwarts. Sirius may have killed him in this version. He may even not have been the Potters’ secret keeper. So far, the story is unclear on these points.
  • McGonagall also hear Trelawney’s prophecy. (Double check that she didn’t in canon)
  • Trelawney’s prophecy is subtly different between the canon and HPMOR, though arguably this is a result of the future changing as a result of Petunia’s transformation, and since the future changed prophecies of the future changed too.

There may be a couple more I’ve missed, but I don’t think there were any that precede Lily making Petunia beautiful.

Rowling Criticisms

There are a number of amusing places in the book where Yudkowsky takes good natured jabs at either Rowling the author or Rowling’s characters in canon. Among them:

Harry is astonished, shocked, and appalled that a sixth year Gryffindor would attack a Sixth Year Slytherin with a curse when he didn’t even know what it would do:

Professor Quirrell slammed the book shut and it vanished with a
small whispering sound. He looked up, then, and Harry flinched.

“I suppose an intelligent conversation would be pleasant for
me at this point,” said Professor Quirrell in the same
biting tone that had invited Harry to enter. “You are not
likely to find it so, be warned.”

Harry drew a deep breath. “I promise I won’t mind if you snap at
me. What happened?”

The cold in the room seemed to deepen. “A sixth-year Gryffindor
cast a curse at one of my more promising students, a sixth-year

Harry swallowed. “What… sort of curse?”

And the fury on Professor Quirrell’s face was no longer
contained. “Why bother to ask an unimportant question like that,
Mr. Potter? Our friend the sixth-year Gryffindor did not think it
was important!”

“Are you serious? ” Harry said before he could stop

“No, I’m in a terrible mood today for no particular reason.
Yes I’m serious, you fool! He didn’t know. He actually
didn’t know.
I didn’t believe it until the Aurors confirmed it
under Veritaserum. He is in his sixth year at Hogwarts and
he cast a high-level Dark curse without knowing what it

“You don’t mean,” Harry said, “that he was mistaken about
what it did, that he somehow read the wrong spell description

“All he knew was that it was meant to be directed at an enemy.
He knew that was all he knew.”

And that had been enough to cast the spell. “I do not understand
how anything with that small a brain could walk upright.”

“Indeed, Mr. Potter,” said Professor Quirrell.

cf. Harry Potter and the Half-blood Prince, Chapter 24.

The snitch completely ruins Quidditch:

“So let me get this straight,” Harry said as it seemed that
Ron’s explanation (with associated hand gestures) was winding down.
“Catching the Snitch is worth one hundred and fifty

“Yeah -“

“How many ten-point goals does one side usually score not counting the Snitch?”

“Um, maybe fifteen or twenty in professional games -“

“That’s just wrong. That violates every possible rule of game
design. Look, the rest of this game sounds like it might make
sense, sort of, for a sport I mean, but you’re basically saying
that catching the Snitch overwhelms almost any ordinary point
spread. The two Seekers are up there flying around looking for the
Snitch and usually not interacting with anyone else, spotting the
Snitch first is going to be mostly luck -“

“It’s not luck!” protested Ron. “You’ve got to keep your eyes
moving in the right pattern -“

“That’s not interactive, there’s no back-and-forth with
the other player and how much fun is it to watch someone incredibly
good at moving their eyes? And then whichever Seeker gets lucky
swoops in and grabs the Snitch and makes everyone else’s work moot.
It’s like someone took a real game and grafted on this pointless
extra position so that you could be the Most Important Player
without needing to really get involved or learn the rest of it. Who
was the first Seeker, the King’s idiot son who wanted to play
Quidditch but couldn’t understand the rules?” Actually, now that
Harry thought about it, that seemed like a surprisingly good
hypothesis. Put him on a broomstick and tell him to catch the shiny

Ron’s face pulled into a scowl. “If you don’t like Quidditch,
you don’t have to make fun of it!”

“If you can’t criticise, you can’t optimise. I’m suggesting how
to improve the game. And it’s very simple. Get rid of the

“They won’t change the game just ’cause you say so!”

“I am the Boy-Who-Lived, you know. People will listen to
me. And maybe if I can persuade them to change the game at
Hogwarts, the innovation will spread.”

A look of absolute horror was spreading over Ron’s face. “But,
but if you get rid of the Snitch, how will anyone know when the
game ends?”

Buy… a… clock. It would be a lot fairer than having
the game sometimes end after ten minutes and sometimes not end for
hours, and the schedule would be a lot more predictable for the
spectators, too.” Harry sighed. “Oh, stop giving me that look of
absolute horror, I probably won’t actually take the time to
destroy this pathetic excuse for a national sport and remake it
stronger and smarter in my own image. I’ve got way, way, way
more important stuff to worry about.” Harry looked thoughtful.
“Then again, it wouldn’t take much time to write up the
Ninety-Five Theses of the Snitchless Reformation and nail it to a
church door -“

(I’ve always agreed with this.)

The plot of Harry Potter and the Goblet of Fire makes no sense at all:

“Bahl’s Stupefaction,” Moody said, naming an extremely addictive narcotic with interesting side effects on people with Slytherin tendencies; Moody had once seen an addicted Dark Wizard go to ridiculous lengths to get a victim to lay hands on a certain exact portkey, instead of just having someone toss the target a trapped Knut on their next visit to town; and after going to all that work, the addict had gone to the further effort to lay a second Portus, on the same portkey, which had, on a second touch, transported the victim back to safety. To this day, even taking the drug into account, Moody could not imagine what could have possibly been going through the man’s mind at the time he had cast the second Portus.

(I’ve always thought Goblet of Fire was by far the weakest of the seven canon novels.)

Dangling Plot Points

HPMOR’s story isn’t finished yet. It’s several hundred pages longer than the longest Rowling novel, with several hundred more yet to come. And it still only takes Harry through Year One at Hogwarts. There are a number of open questions that have yet to be resolved, including:

What’s wrong with the story of Harry’s parents’ deaths on p. 20?

And somewhere in the back of his mind was a small, small note of confusion, a sense of something wrong about that story; and it should have been a part of Harry’s art to notice that tiny note, but he was distracted. For it is a sad rule that whenever you are most in need of your art as a rationalist, that is when you are most likely to forget it.

What was the incident at the Potions Shop? (Perhaps just unmentioned or unclear?)

Was Harry sorted into Slytherin? (possibly)

On p. 176 what does the drooling professor remind him of?

On p. 200 Why does the Remebrall glow when Harry picks it up? What has Harry forgotten? Possible (but not probable) answer: he has simply forgotten that he should have lost to Goyle. I don’t like that though because it’s more a failure to figure something out than forgetting something he once knew.

What is the defense professor’s mysterious illness? Possible answer: Voldemort’s stuck to the back of his head, but it seems too obvious and too derived from canon. Yudkowsky is explicit about telling a different story, albeit in the same universe with mostly the same characters. In this case since the defense professor is not Quirrell, we can assume that the real Quirrell is somewhere offstage, possibly with Voldemort stuck to the back of his head. On p. 848 we see the back of Quirrell’s head, and there’s no Voldemort there. Memo to self: check to see if the physical descriptions Quirrell in HPMOR match those in Sorcerer’s Stone. If they do, then perhaps the defense professor is holding Quirrell in a trunk somewhere and using polyjuice to maintain appearances.

Why does Harry have a sense of impending doom when he gets close to the defense professor? Why do their magics interact like they do? Same possible answer. Same objection. A more interesting possibility: Voldemort is not stuck to the back of the defense professor’s head. Voldemort is the defense professor. In this version Tom Riddle is older, wiser, and less evil for reasons yet to be seen. The reveal of his true identity in Chapter 79 is a double fake. Or he’s just as evil as ever but still older and wiser and he intends to take over Harry Potter’s body or otherwise rule through him. This seems to be the most popular explanation, though I’m trying to avoid getting caught in an Asch conformity experiment here. (That’s why I didn’t spend a lot of time reading the forums until I’d read the whole thing twice.)

Is Dumbledore insane? I think not. My best guess is that this is the same Dumbledore we see in canon, but because Harry is different he interprets Dumbledore’s actions and personality differently.

Who set up Hermione? How and was it done and why?

What does the defense professor want to lose on p. 598? A Horcux?

Why did the defense professor break Bellatrix out of Azkaban? it seems unlikely that the reasons he gives before or after the fact are sufficient.

Did Dumbledore burn Narcissa Malfoy to death in her bed? If so, were there extenuating circumstances? And if he didn’t, who did? (My guess: Dumbledore did it, and there were no extenuating circumstances according to the terms of Draco’s agreement with Harry; but Harry may change his mind and break his promise to Draco anyway.)

Who is the man in the black hat/mysterious glowing lady? And what does she want? My best guess: Rowena Ravenclaw or her ghost. Second best guess: Narcissa Malfoy or her ghost.

What really happened to Peter Pettigrew?

What is Harry’s mysterious dark side? (The obvious answer is the eighth part of Voldemort’s soul, but that seems a little too obvious; and too gratuitously different from canon. Yudkowsky seems to stick fairly closely to the established workings of magic from the original. he introduces new details and explanations, but does not throw away what we already know about how magic works. If it is the eighth part of Voldemort’s soul, then there has to be a reason it affects Harry differently in HPMOR than in canon.)

Is Voldemort still alive? If so, where? There are strong hints in the book that maybe he isn’t alive in this alternate universe; and maybe he isn’t the Dark Lord Harry has to defeat. (My best guess: Harry himself is the Dark Lord Harry has to defeat.)

Possibly related question: what happened to the real Quirinus Quirrell? I suspect the answer to this one is that this was simply driven by the needs of the plot. I.e. Yudkowsky needs to bring in a different character to make his stories work.

Maybe we’ll know a little more in December, when the next update is scheduled. Meanwhile Yudkowsky does seem to believe you can figure out the plot from Chapter 1-3 alone, and maybe even just 1, though he seems to only know someone who’s done it from 1-20. Of course, great mysteries are obvious but only in hindsight.

Ultimate Predictions

If we take Yudkowsky at his word you can figure out the entire plot from Chapter 1, then that severely limits the hypothesis space. Very little is suggested by Chapter 1, but this seems significant:

Petunia bit her lip. “I can’t just tell you. You’ll think I’m -”
She swallowed. “Listen. Michael. I wasn’t – always like this -” She
gestured at herself, as though to indicate her lithe form. “Lily
did this. Because I – because I begged her. For years, I
begged her. Lily had always been prettier than me, and
I’d… been mean to her, because of that, and then she got
magic, can you imagine how I felt? And I begged her
to use some of that magic on me so that I could be pretty too, even
if I couldn’t have her magic, at least I could be pretty.”

Tears were gathering in Petunia’s eyes.

“And Lily would tell me no, and make up the most ridiculous
excuses, like the world would end if she were nice to her sister,
or a centaur told her not to – the most ridiculous things, and I
hated her for it. And when I had just graduated from university, I
was going out with this boy, Vernon Dursley, he was fat and he was
the only boy who would talk to me. And he said he wanted children,
and that his first son would be named Dudley. And I thought to
myself, what kind of parent names their child Dudley
It was like I saw my whole future life stretching out
in front of me, and I couldn’t stand it. And I wrote to my sister
and told her that if she didn’t help me I’d rather just -“

Petunia stopped.

“Anyway,” Petunia said, her voice small, “she gave in. She told
me it was dangerous, and I said I didn’t care any more, and I drank
this potion and I was sick for weeks, but when I got better my skin
cleared up and I finally filled out and… I was beautiful, people
were nice to me,” her voice broke, “and after that I
couldn’t hate my sister any more, especially when I learned what
her magic brought her in the end -“

So the one serious clue we have in Chapter 1 is that Lily was warned somehow that helping her sister would bring about the end of the world. Furthermore she may have been told this by a centaur, and we know from canon that centaurs are really good at astrology and divination. Maybe this wasn’t just an excuse? So the ultimate resolution of this story is that the world ends, or something very close to that occurs.

Of course any change here is probably going come about through a change in Harry (or very less likely, the non-existence of Dudley, or something Vernon Dursley does; but nothing in the next 84 chapter suggests this). What is the one important thing Harry does in canon? He defeats Voldemort. Everything else he does leads up to that. So the hypothesis is that in HPMOR, Harry fails to defeat Voldemort. Voldemort wins. Possibly he destroys the world thereafter, or perhaps destroying the world is a bit exaggerated and metaphorical, and this brings us to the second possibility.

In canon, by defeating Voldemort, Harry preserves the existing magical order. The International Statute of Wizarding Secrecy is maintained. The Ministry of Magic still rules. And as we see in the final chapter of The Deathly Hallows, life continues for wizards into the next generation much as it has before. This time around I don’t think it does. Even if Harry ultimately defeats Voldemort again (if Voldemort is even still alive in this variant) I think he’s going to destroy the existing wizarding world. This is hinted at repeatedly throughout the book, and in several chapters Harry is quite explicit about it. He doesn’t quite get around to doing it by chapter 85, but he does successfully force Dumbledore to assist him by threatening to tear down Azkaban if he doesn’t, and his backup plan at that point is to kill two thirds of the Wizengamot, so he’s definitely thinking about it. I think before the book is over Harry’s going to do it. He may not (or may) kill a whole bunch of people but I think he’s going to break International Statute of Wizarding Secrecy and bring down the Ministry of Magic, leaving a magical society so changed that the world as wizards know it will have ended for good, thus fulfilling Lily’s fears.

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