Harry Potter and the Methods of Rationality (5 page)

(Harry’s parents had in fact only ever sung him those
particular
lines of that Tom Lehrer song, and Harry was blissfully unaware of the rest.)

Professor McGonagall’s stance had slightly softened - though mostly when Harry had said that he was heading for Ravenclaw. “What sort of
contingency
do you imagine this kit might prepare you for,
young man?
”

“One of my classmates gets bitten by a horrible monster, and as I scrabble frantically in my mokeskin pouch for something that could help her, she looks at me sadly and with her last breath says,
‘Why weren’t you prepared?’
And then she dies, and I know as her eyes close that she won’t ever forgive me -”

Harry heard the salesgirl gasp, and he looked up to see her staring at him with her lips pressed tight. Then the young woman whirled and fled into the deeper recesses of the shop.

What…?

Professor McGonagall reached down, and took Harry’s hand in hers, gently but firmly, and pulled Harry out of the main street of Diagon Alley, leading him into an alleyway between two shops which was paved in dirty bricks and dead-ended in a wall of solid black dirt.

The tall witch pointed her wand at the main street and spoke,
“Quietus
” she said, and a screen of silence descended around them, blocking out all the street noises.

What did I do wrong…

Professor McGonagall turned to regard Harry. She didn’t have a full adult Wrongdoing Face, but her expression was flat, controlled. “You must remember, Mr. Potter,” she said, “that there was a war in this country not ten years ago. Everyone has lost someone, and to speak of friends dying in your arms - is not done lightly.”

“I - I didn’t mean to -” The inference dropped like a falling stone into Harry’s exceptionally vivid imagination. He’d talked about someone breathing their last breath - and then the salesgirl had run away - and the war had ended ten years ago so that girl would have been at most eight or nine years old, when, when, “I’m sorry, I didn’t mean to…” Harry choked up, and turned away to run from the older witch’s gaze but there was a wall of dirt blocking his way and he didn’t have his wand yet. “I’m sorry, I’m sorry, I’m
sorry!
”

There came a heavy sigh from behind him. “I know you are, Mr. Potter.”

Harry dared to peek behind him. Professor McGonagall only seemed sad, now. “I’m sorry,” Harry said again, feeling wretched. “Did anything like that happen to -” and then Harry shut his lips and slapped a hand over his mouth for good measure.

The older witch’s face grew a little sadder. “You must learn to think before you speak, Mr. Potter, or else go through life without many friends. That has been the fate of many a Ravenclaw, and I hope it will not be yours.”

Harry wanted to just run away. He wanted to pull out a wand and erase the whole thing from Professor McGonagall’s memory, be back with her outside the shop again,
make it didn’t happen -

“But to answer your question, Mr. Potter, no, nothing like
that
has ever happened to me. Certainly I’ve watched a friend breathe their last, once or seven times. But not one of them ever cursed me as they died, and I never thought that they wouldn’t forgive me. Why would you
say
such a thing, Mr. Potter? Why would you even
think
it?”

“I, I, I,” Harry swallowed. “It’s just that I always try to imagine the worst thing that could happen,” and maybe he’d also been joking around a little but he would rather have bitten off his own tongue than say that now.

“What?” said Professor McGonagall. “But
why?”

“So I can stop it from happening!”

“Mr. Potter…” the older witch’s voice trailed off. Then she sighed, and knelt down beside him. “Mr. Potter,” she said, gently now, “it’s not your responsibility to take care of the students at Hogwarts. It’s mine. I won’t let anything bad happen to you or anyone else. Hogwarts is the safest place for magical children in all the wizarding world, and Madam Pomfrey has a full healer’s office. You won’t need a healer’s kit at all, let alone a five-Galleon one.”

“But I
do!
” Harry burst out. ”
Nowhere
is perfectly safe! And what if my parents have a heart attack or get in an accident when I go home for Christmas - Madam Pomfrey won’t be there, I’ll need a healer’s kit of my own -”

“
What
in Merlin’s name…” Professor McGonagall said. She stood up, and looked down at Harry an expression torn between annoyance and concern. “There’s no need to think about such terrible things, Mr. Potter!”

Harry’s expression twisted up into bitterness, hearing that. “Yes there
is!
If you don’t think, you don’t just get hurt yourself, you end up hurting other people!”

Professor McGonagall opened her mouth, then closed it. The witch rubbed the bridge of her nose, looking thoughtful. “Mr. Potter… if I were to offer to listen to you for a while… is there anything you’d like to talk to me about?”

“About what?”

“About why you’re convinced you must always be on your guard against terrible things happening to you.”

Harry stared at her in puzzlement. That was a self-evident axiom. “Well…” Harry said slowly. He tried to organise his thoughts. How
could
he explain himself to a Professor-witch, when she didn’t even know the basics? “Muggle researchers have found that people are always very optimistic, compared to reality. Like they say something will take two days and it takes ten days, or they say it’ll take two months and it takes over thirty-five years. For example, in one experiment, they asked students for times by which they were 50% sure, 75% sure, and 99% sure they’d complete their homework, and only 13%, 19%, and 45% of the students finished by those times. And they found that the reason was that when they asked one group for their best-case estimates if everything went as well as possible, and another group for their average-case estimates if everything went as usual, they got back answers that were statistically indistinguishable. See, if you ask someone what they expect in the
normal
case, they visualise what looks like the line of maximum probability at each step along the way - everything going according to plan, with no surprises. But actually, since more than half the students didn’t finish by the time they were 99% sure they’d be done, reality usually delivers results a little worse than the ‘worst-case scenario’. It’s called the planning fallacy, and the best way to fix it is to ask how long things took the last time you tried them. That’s called using the outside view instead of the inside view. But when you’re doing something new and can’t do that, you just have to be really, really, really pessimistic. Like, so pessimistic that reality actually comes out
better
than you expected around as often and as much as it comes out worse. It’s actually
really hard
to be
so
pessimistic that you stand a decent chance of
undershooting
real life. Like I make this big effort to be gloomy and I imagine one of my classmates getting bitten, but what actually happens is that the surviving Death Eaters attack the whole school to get at me. But on a happier note -”

“Stop,” said Professor McGonagall.

Harry stopped. He had just been about to point out that at least they knew the Dark Lord wouldn’t attack, since he was dead.

“I think I might not have made myself clear,” the witch said, her precise Scottish voice sounding even more careful. “Did anything happen to
you personally
that frightened you, Mr. Potter?”

“What happened to me personally is only anecdotal evidence,” Harry explained. “It doesn’t carry the same weight as a replicated, peer-reviewed journal article about a controlled study with random assignment, many subjects, large effect sizes and strong statistical significance.”

Professor McGonagall pinched the bridge of her nose, inhaled, and exhaled. “I would still like to hear about it,” she said.

“Um…” Harry said. He took a deep breath. “There’d been some muggings in our neighborhood, and my mother asked me to return a pan she’d borrowed to a neighbor two streets away, and I said I didn’t want to because I might get mugged, and she said, ‘Harry, don’t say things like that!’ Like thinking about it would
make
it happen, so if I didn’t talk about it, I would be safe. I tried to explain why I wasn’t reassured, and she made me carry over the pan anyway. I was too young to know how statistically unlikely it was for a mugger to target me, but I was old enough to know that not-thinking about something doesn’t stop it from happening, so I was really scared.”

“Nothing else?” Professor McGonagall said after a pause, when it became clear that Harry was done. “There isn’t anything
else
that happened to you?”

“I know it doesn’t
sound
like much,” Harry defended. “But it was just one of those critical life moments, you see? I mean, I
knew
that not thinking about something doesn’t stop it from happening, I
knew
that, but I could see that Mum really thought that way.” Harry stopped, struggling with the anger that was starting to rise up again when he thought about it. “She
wouldn’t listen
. I tried to tell her, I
begged
her not to send me out, and she
laughed it off
. Everything I said, she treated like some sort of big joke…” Harry forced the black rage back down again. “That’s when I realised that everyone who was supposed to protect me was actually crazy, and that they wouldn’t listen to me no matter how much I begged them, and that I couldn’t ever rely on them to get anything right.” Sometimes good intentions weren’t enough, sometimes you had to be sane…

There was a long silence.

Harry took the time to breathe deeply and calm himself down. There was no point in getting angry. There was no point in getting angry.
All
parents were like that,
no
adult would lower themselves far enough to place themselves on level ground with a child and listen, his genetic parents would have been no different. Sanity was a tiny spark in the night, an infinitesimally rare exception to the rule of madness, so there was no point in getting angry.

Harry didn’t like himself when he was angry.

“Thank you for sharing that, Mr. Potter,” said Professor McGonagall after a while. There was an abstracted look on her face (almost exactly the same look that had appeared on Harry’s own face while experimenting on the pouch, if Harry had only seen himself in a mirror to realise that). “I shall have to think about this.” She turned towards the alley mouthway, and raised her wand -

“Um,” Harry said, “can we go get the healer’s kit now?”

The witch paused, and looked back at him steadily. “And if I say no - that it is too expensive and you won’t need it - then what?”

Harry’s face twisted in bitterness. “Exactly what you’re thinking, Professor McGonagall.
Exactly
what you’re thinking. I conclude you’re another crazy adult I can’t talk to, and I start planning how to get my hands on a healer’s kit anyway.”

“I am your guardian on this trip,” Professor McGonagall said with a tinge of danger. “I
will not
allow you to push me around.”

“I understand,” Harry said. He kept the resentment out of his voice, and didn’t say any of the other things that came to mind. Professor McGonagall had told him to think before he spoke. He probably wouldn’t remember that tomorrow, but he could at least remember it for five minutes.

The witch’s wand made a slight circle in her hand, and the noises of Diagon Alley came back. “All right, young man,” she said. “Let’s go get that healer’s kit.”

Harry’s jaw dropped in surprise. Then he hurried after her, almost stumbling in his sudden rush.

The shop was the same as they had left it, recognisable and unrecognisable items still laid out on the slanted wooden display, the grey glow still protecting and the salesgirl back in her old position. The salesgirl looked up as they approached, her face showing surprise.

“I’m sorry,” she said as they got closer, and Harry spoke at almost the same moment, “I apologise for -”

They broke off and looked at each other, and then the salesgirl laughed a little. “I didn’t mean to get you in trouble with Professor McGonagall,” she said. Her voice lowered conspiratorially. “I hope she wasn’t
too
awful to you.”

“
Della!
” said Professor McGonagall, sounding scandalised.

“Bag of gold,” Harry said to his pouch, and then looked back up at the salesgirl while he counted out five Galleons. “Don’t worry, I understand that she’s only awful to me because she loves me.”

He counted out five Galleons to the salesgirl while Professor McGonagall was spluttering something unimportant. “One Emergency Healing Pack Plus, please.”

It was actually sort of unnerving to see how the Widening Lip swallowed the briefcase-sized medical kit. Harry couldn’t help wondering what would happen if he tried climbing into the mokeskin pouch himself, given that only the person who put something in was supposed to be able to take it out again.

When the pouch was done… eating… his hard-won purchase, Harry swore he heard a small burping sound afterward. That
had
to have been spelled in on purpose. The alternative hypothesis was too horrifying to contemplate… in fact Harry couldn’t even
think
of any alternative hypotheses. Harry looked back up at the Professor, as they began walking through Diagon Alley once more. “Where to next?”

Professor McGonagall pointed toward a shop that looked as if it had been made from flesh instead of bricks and covered in fur instead of paint. “Small pets are permitted at Hogwarts - you could get an owl to send letters, for example -”

“Can I pay a Knut or something and
rent
an owl when I need to send mail?”

“Yes,” said Professor McGonagall.

“Then I think emphatically
no.
”

Professor McGonagall nodded, as though ticking off a point. “Might I ask why not?”

“I had a pet rock once. It died.”

“You don’t think you could take care of a pet?”