Harry Potter and the Methods of Rationality

'Um,' Harry said to Hermione. 'Can I just sort of go off and follow him and let you work out what I should say to make sure you're not all worried and offended?'

'No,' Hermione said, her voice trembling.

Severus's laughter echoed from around the corner.

Harry bowed his head. 'Sorry,' he said lowly, 'really,' and he went off after the Potions Master.

'So,' Harry said. There were no other sounds now but two pairs of legs, the long and the short, padding across a random stone corridor. The Potions Master was striding quickly but not too fast for Harry to keep up, and insofar as Harry could apply the concept of directionality to Hogwarts, they were moving away from the frequented areas. 'What's this about?'

'I don't suppose you could explain,' Severus said dryly, 'why the two of you were plotting to murder Cho Chang?'

'I don't suppose you could explain,' Harry said dryly, 'in your capacity as an official of the Hogwarts school system, why catching a golden mosquito is deemed an academic accomplishment worthy of a hundred and fifty House points?'

A smile crossed Severus's lips. 'Dear me, and I thought you were supposed to be perceptive. Are you truly so incapable of understanding your classmates, Potter, or do you dislike them too much to try? If Quidditch scores did not count toward the House Cup then none of them would care about House points at all. It would merely be an obscure contest for students like you and Miss Granger.'

It was a shockingly good answer.

And that shock brought Harry's mind fully awake.

In retrospect it shouldn't have been surprising that Severus understood his students, understood them very well indeed.

He had been reading their minds.

And...

...the book said that a successful Legilimens was extremely rare, rarer than a perfect Occlumens, because almost no one had enough mental discipline.

Mental discipline?

Harry had collected stories about a man who routinely lost his temper in class and blew up at young children.

...but this same man, when Harry had spoken of the Dark Lord still being alive, had responded instantly and perfectly - reacting in precisely the way that someone completely ignorant would react.

The man stalked about Hogwarts with the air of an assassin, radiating danger...

...which was exactly not what a real assassin should do. Real assassins should look like meek little accountants until they killed you.

He was the Head of House for proud and aristocratic Slytherin, and he wore a robe with spotted stains from bits of potions and ingredients, which two minutes of magic could have removed.

Harry noticed that he was confused.

And his threat estimate of the Head of House Slytherin shot up astronomically.

Dumbledore had seemed to think Severus was his, and there'd been nothing to contradict that; the Potions Master had been 'scary but not abusive', as promised. So, Harry had reasoned earlier, this was Fellowship business. If Severus had been planning harm, surely he wouldn't have come to get Harry in front of Hermione, a witness, when he could have simply waited for some time when Harry was alone...

Harry quietly bit his lip.

'I once knew a boy who truly adored Quidditch,' said Severus Snape. 'He was an utter pillock. Just as you and I would expect, we two.'

'What is this?' Harry said slowly.

'Patience, Potter.'

Severus turned his head, and then glided with his assassin's bearing into a nearby opening in the corridor walls, a smaller and narrower hallway leading off.

Harry followed him, wondering if it would be smarter to simply run away.

They turned and made another turn, and came to a dead end, a simple blank wall. If Hogwarts had actually been built, rather than conjured or summoned or birthed or whatever, Harry would have had some sharp words for the architect about paying people to build hallways that didn't go anywhere.

'Quietus,' said Severus, and a few other things as well.

Harry leaned back, folded his arms across his chest, and watched Severus's face.

'Looking me in the eyes, Potter?' said Severus Snape. 'Your Occlumency lessons cannot have progressed far enough for you to block Legilimency. But then perhaps they have progressed far enough for you to detect it. Since I cannot know otherwise, I will not risk trying.' The man smiled thinly. 'And the same will hold for Dumbledore, I think. Which is why we are now having this little talk.'

Harry's eyes widened involuntarily.

'To begin with,' Severus said, eyes glittering, 'I should like you to promise not to speak of our conversations to anyone. So far as the school is concerned, we are discussing your Potions homework. Whether or not they believe that is unimportant. So far as Dumbledore and McGonagall are concerned, I am violating Draco Malfoy's confidences in me, and neither of us think it proper to speak further of the particulars.'

Harry's brain tried to calculate the ramifications and implications of this and ran out of swap space.