Harry Potter and the Methods of Rationality (159 page)

If Harry hadn’t been constrained by Ethics, it was possible he could’ve wiped out the eviller sections of the Wizengamot that day; all by himself, using only a first-year’s magical power, on account of being clever enough to figure out Dementors. Though Harry might not have been in such a great political position after that, the surviving Wizengamot members might’ve found it easy and cheap to disavow his actions for P.R. purposes and condemn him, even if the smarter ones realized it was for the greater good… but
still.

If you were completely unrestrained by ethics, armed with the ancient secrets of Salazar Slytherin, had dozens of powerful followers including Lucius Malfoy, and it took you more than ten years to
fail
to overthrow the government of magical Britain, it meant you were stupid.

“How can I put this…” Harry said. “Look, Headmaster, you’ve got ethics, there’s a lot of battle tactics you don’t use because you’re not evil. And you fought the Dark Lord, a tremendously powerful wizard who wasn’t so restrained, and you held him off
anyway
. If You-Know-Who had been super-smart
on top of that
, you’d be
dead.
All
of you. You’d have died
instantly -
”

“Harry,” Professor McGonagall said. Her voice was faltering. “Harry, we almost
did
all die. More than half the Order of the Phoenix died. If not for Albus - Albus Dumbledore, the greatest wizard in two centuries, Harry - we surely would have perished.”

Harry passed a hand across his forehead. “I’m sorry,” Harry said. “I’m not trying to minimize what you went through. I know that You-Know-Who was a completely evil, incredibly powerful Dark Wizard with dozens of powerful followers, and that’s… bad, yes, definitely bad. It’s just…”
All that isn’t on remotely the same threat scale as the enemy being smart, in which case they Transfigure botulinum toxin and sneak a millionth of a gram into your teacup.
Was there any safe way to convey that concept without citing specifics? Harry couldn’t think of one.

“Please, Harry,” said Professor McGonagall. “Please, Harry, I beg you -
take the Dark Lord seriously!
He is more dangerous than -” The senior witch seemed to be having trouble finding words. “He is
far
more dangerous than Transfiguration.”

Harry’s eyebrows went up before he could stop himself. A dark chuckle came from Severus Snape’s direction.

Um,
said the voice of Ravenclaw within him.
Um, honestly Professor McGonagall is right, we’re not taking this as seriously as we’d take a scientific problem. The difficult thing is to react
at all
to new information, instead of just flushing it out the window. Right now it looks like we didn’t shift belief
at all
after encountering an unexpected, important argument. Our dismissal of Lord Voldemort as a serious threat
was
originally based on the Dark Mark being blatantly stupid. It would require a focused effort to de-update and suspect the whole garden-path of reasoning we went down based on that false assumption, and we’re
not
putting in that effort right now.

“All right,” Harry said, just as Professor McGonagall seemed to be about to speak again. “All right, to take this seriously, I need to stop and think for five minutes.”

“Please do,” said Albus Dumbledore.

Harry closed his eyes.

His Ravenclaw side divided into three.

Probability estimate,
said Ravenclaw One, who was acting as moderator.
That the Dark Lord is alive, and as smart as we are, and hence a genuine threat.

Why aren’t all his enemies already dead?
said Ravenclaw Two, who was prosecuting.

Note,
said Ravenclaw One,
we had already thought of that argument so we can’t use it to shift belief
again
each time we rehearse it.

But what’s the actual flaw in the logic?
said Ravenclaw Two.
In worlds with a smart Lord Voldemort, everyone in the Order of the Phoenix died in the first five minutes of the war. The world doesn’t look like that, so we don’t live in that world. QED.

Is that really certain?
asked Ravenclaw Three, who’d been appointed as the defender.
Maybe there was some reason Lord Voldemort
wasn’t
fighting all-out back then -

Like what?
demanded Ravenclaw Two.
Furthermore, whatever your excuse, I demand that the probability of your hypothesis be penalized in accordance with its added complexity -

Let Three talk,
said Ravenclaw One.

Okay… look,
said Ravenclaw Three.
First of all, we don’t
know
that anyone can take over the Ministry just with mind control. Maybe magical Britain is really an oligarchy and you need enough military power to intimidate the family heads into submission -

Imperius them too,
interjected Ravenclaw Two.

- and the oligarchs have Thief’s Downfall in the entrances to
their
homes -

Complexity penalty!
cried Ravenclaw Two.
More epicycles!

-
oh, be reasonable,
said Ravenclaw Three.
We haven’t actually
seen
anyone taking over the Ministry with a couple of well-placed Imperius curses. We don’t
know
that it can actually be done that easily.

But,
said Ravenclaw Two,
even taking that into account… it really seems like there should’ve been
some
other way. Ten years of failure, really? Using only conventional terrorist tactics? That’s just… not even
trying.

Maybe Lord Voldemort did have more creative ideas,
replied Ravenclaw Three,
but he didn’t want to tip his hand to
other
countries’ governments, didn’t want
them
to know how vulnerable they were and install Thief’s Downfall in
their
Ministries. Not until he had Britain as a base and enough servants to subvert
all
the other major governments simultaneously.

You’re assuming he wants to conquer the whole world,
noted Ravenclaw Two.

Trelawney prophesized that he would be our equal,
intoned Ravenclaw Three solemnly.
Therefore, he wanted to take over the world.

And if he is your equal, and you do have to fight him -

For an instant, Harry’s mind tried to imagine the specter of two
creative
wizards fighting an all-out-war against each other.

Harry had noted all the Charms and Potions in his first-year books that could be creatively used to kill people. He hadn’t been able to help himself. Literally. He’d
tried
to stop his brain from doing it each time, but it was like looking at a fish and trying to stop your brain from noticing it was a fish. What someone could creatively do with seventh-year, or Auror-level, or ancient lost magic such as Lord Voldemort had possessed… didn’t bear thinking about. A magically-superpowered creative-genius psychopath wasn’t a ‘threat’, it was an extinction event.

Then Harry shook his head, dismissing the gloomy line his reasoning had been going down. The question was whether there was a significant probability of facing anything so terrible as a Dark Rationalist in the first place.

Prior odds that someone attempting an immortality ritual would actually have it work…

Call it one to a thousand, at a generous overestimate; it was not the case that roughly one wizard in a thousand survived their death. Though, admittedly Harry didn’t have data on how many had attempted immortality rituals first.

What if the Dark Lord
is
as smart as us?
said Ravenclaw Three.
You know, the way Trelawney prophesied him being our
equal.
Then he would
make
his immortality ritual work.
P.S., don’t forget that ‘destroy all but a remnant of the other’ line.

Requiring that level of intelligence was an additional burdensome detail; prior odds of a random population member being that intelligent were low…

But Lord Voldemort wasn’t a randomly selected wizard, he was one particular wizard in the population who’d come to everyone’s attention. The puzzle of the Mark implied a certain minimum level of intelligence, even if (hypothetically) the Dark Lord had taken longer to think it through. Then again, in the Muggle world, all of the extremely intelligent people Harry knew about from history had
not
become evil dictators or terrorists. The closest thing to that in the Muggle world was hedge-fund managers, and none of
them
had tried to take over so much as a third-world country, a point which put upper bounds on both their possible evil and possible goodness.

There were hypotheses where the Dark Lord was smart and the Order of the Phoenix
didn’t
just instantly die, but those hypotheses were more complicated and ought to get complexity penalties. After the complexity penalties of the further excuses were factored in, there would be a large likelihood ratio from the hypotheses ‘The Dark Lord is smart’ versus ‘The Dark Lord was stupid’ to the observation, ‘The Dark Lord did not instantly win the war’. That was probably worth a 10:1 likelihood ratio in favor of the Dark Lord being stupid… but maybe not 100:1. You couldn’t actually say that ‘The Dark Lord instantly wins’ had a probability of
more
than 99 percent, assuming the Dark Lord started out smart; the sum over all possible excuses would be more than .01.

And then there was the Prophecy… which might or might not have
originally
included a line about how Lord Voldemort would
immediately
die if he confronted the Potters. Which Albus Dumbledore had then edited in Professor McGonagall’s memory, in order to lure Lord Voldemort to his doom. If there
was
no such line, the Prophecy did sound
somewhat
more like You-Know-Who and the Boy-Who-Lived were destined to have some later confrontation. But in
that
case, it was less likely that Dumbledore would’ve come up with a plausible-sounding excuse not to take Harry to the Hall of Prophecy…

Harry was wondering if he could even
get
a Bayesian calculation out of this. Of course, the point of a subjective Bayesian calculation wasn’t that, after you made up a bunch of numbers, multiplying them out would give you an exactly right answer. The real point was that the
process
of making up numbers would force you to tally all the relevant facts and weigh all the relative probabilities. Like realizing, as soon as you actually
thought
about the probability of the Dark Mark not-fading
if
You-Know-Who
was
dead, that the probability wasn’t low enough for the observation to count as strong evidence. One version of the process was to tally hypotheses and list out evidence, make up all the numbers, do the calculation, and then throw out the final answer and go with your brain’s gut feeling
after
you’d forced it to really
weigh
everything. The trouble was that the items of evidence weren’t conditionally independent, and there were multiple interacting background facts of interest…

…well,
one
thing at least was certain.

If the calculation could be done at all, it was going to take a piece of paper and a pencil.

In the fireplace at one side of the Headmaster’s office, the flames suddenly flared up, turning from orange to bright billious green.

“Ah!” said Professor McGonagall into the uncomfortable non-silence. “That would be Mad-Eye Moody, I suppose.”

“Let this matter bide for now,” the Headmaster said in some relief, as he too turned to regard the Floo. “I believe we are about to receive some news regarding it, as well.”

Hypothesis: Hermione Granger
(April 8th, 1992, 6:53pm)

Meanwhile in the Great Hall of Hogwarts, as the students who didn’t have secret meetings with the Headmaster bustled about their dinner around four huge tables -

“It’s funny,” Dean Thomas said thoughtfully. “I didn’t believe the General when he said that what we learned would change us forever, and we’d never be able to return to a normal life afterward. Once we knew. Once we saw what
he
could see.”

“I know!” said Seamus Finnigan. “I thought it was just a joke too! Like, you know, everything else General Chaos ever said ever.”

“But now -” Dean said sadly. “We
can’t
go back, can we? It’d be like going back to a Muggle school after having been to Hogwarts. We’ve just… we’ve just got to stay around each other. That’s all we can do, or we’ll go crazy.”

Seamus Finnigan, next to him, just nodded wordlessly and ate another bite of veldbeest.

Around them, the conversation at the Gryffindor table continued. It wasn’t as
relentless
as it’d been yesterday, but now and then the topic wandered back.

“Well, there must’ve been
some
sort of love triangle,” said a second-year witch named Samantha Crowley (she never answered when asked if there was any relation). “The question is, which ways was it
going
before it all went wrong? Who was in love with who - and whether or not that person loved them back - I don’t know
how
many possibilities there are -”

“Sixty-four,” said Sarah Varyabil, a blossoming beauty who probably should’ve been Sorted into Ravenclaw or Hufflepuff instead. “No, wait, that’s wrong. I mean, if nobody loved Malfoy and Malfoy didn’t love anyone then he wouldn’t really be part of the love triangle… this is going to take Arithmancy, could you all wait two minutes?”

“
I,
for one, think it perfectly clear that Granger is Potter’s moirail, and that Potter was auspisticing between Malfoy and Granger.” The witch who’d spoken nodded with the self-satisfaction of someone who has just precisely nailed down a complicated issue.

“Those aren’t even words,” objected a young wizard. “You’re just making them up as you go.”

“Sometimes you can’t describe a thing using
real
words.”