Eliezer Yudkowsky - Harry Potter and the Methods of Rationality

And the true and honest reason Harry knew the Dark Lord couldn't have been that smart... well... there wasn't any tactful way to say it, but...

Harry had been to a convocation of the Wizengamot. He'd seen the laughable 'security precautions', if you could call them that, guarding the deepest levels of the Ministry of Magic. They didn't even have the Thief's Downfall which goblins used to wash away Polyjuice and Imperius Curses on people entering Gringotts. The obvious takeover route would be to Imperius the Minister of Magic and a few department heads, and owl a hand grenade to anyone too powerful to Imperius. Or owl them knockout gas, if you needed them alive and in a state of Living Death to take hairs for Polyjuice potions. Legilimency, False Memories, the Confundus Charm - it was ridiculous, the magical world was supersaturated with ways to cheat. Harry might not do any of those things himself, during his own takeover of Britain, since he was constrained by Ethics... well, Harry might do some of the lesser ones, since Polyjuice or a temporary Confundus or read-only Legilimency all sounded better than an extra day of Azkaban... but...

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.