Harry Potter and the Methods of Rationality

Happiness is not the most important thing in the world to me. I would not become all that I could be, in Hufflepuff. I would sacrifice my potential.

The Hat flinched; Harry could feel it somehow. It was like he had kicked the hat in the balls - in a strongly weighted component of its utility function.

Why are you trying to send me where I do not belong?

The Hat's thought was almost a whisper. "I cannot speak of the others to you - but do you think that you are the first potential Dark Lord to pass under my brim? I cannot know the individual cases, but I can know this: Of those who did not intend evil from the very beginning, some of them listened to my warnings, and went to Houses where they would find happiness. And some of them... some of them did not."

That stopped Harry. But not for long. And of those who did not heed the warning - did they all become Dark Lords? Or did some of them achieve greatness for good, as well? Just what are the exact percentages here?

"I cannot give you exact statistics. I cannot know them so I cannot count them. I just know that your chances don't feel good. They feel very not-good."

But I just wouldn't do that! Ever!

"I know that I have heard that claim before."

I am not Dark Lord material!

"Yes, you are. You really, really are."

Why? Just because I once thought it would be cool to have a legion of brainwashed followers chanting 'Hail the Dark Lord Harry'?

"Amusing, but that was not your first fleeting thought before you substituted something safer, less damaging. No, what you remembered was how you considered lining up all the blood purists and guillotining them. And now you are telling yourself you were not serious, but you were. If you could do it this very moment and no one would ever know, you would. Or what you did this morning to Neville Longbottom, deep inside you knew that was wrong but you did it anyway because it was fun and you had a good excuse and you thought the Boy-Who-Lived could get away with it -"

That's unfair! Now you're just dragging up inner fears that aren't necessarily real! I worried that I might be thinking like that, but in the end I decided it would probably work to help Neville -

"That was, in fact, a rationalisation. I know. I cannot know what the true outcome will be for Neville - but I know what was truly happening inside your head. The decisive pressure was that it was such a clever idea you couldn't stand not to do it, never mind Neville's terror."

It was like a hard punch to Harry's entire self. He fell back, rallied:

Then I won't do that again! I'll be extra careful not to turn evil!

"Heard it."