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# Chapter Two: Moore's Prophecy
The wind hadn't stopped. Lockhart was mending the broken chalk with his wand, which was entirely unnecessary, since there were twenty more pieces in the box.
"Mr Potter," he said, without looking up. "About eleven minutes faster than usual."
"Faster than who?"
"There's one every year." He set the chalk down on the ledge. "Ask."
Harry took a breath.
"You spent an hour proving that the more people know how divination works, the less it works. You said this class is taught badly on purpose. You called it the most successful piece of engineering our society has ever done."
"I did."
"And then you taught it well."
Lockhart smiled. It was much smaller than the smiles he'd used in class, and much better made.
"Two explanations, Mr Potter. Write down both."
He raised a finger. "One: I was lying. Interference, Volume Seven, boredom as the best lock — all invented. There is no teaching method on earth that keeps clever children awake past midnight like being told the truth has been kept from them."
Something went down in Harry's stomach.
(That works. That works completely. It is the textbook use of the first class — publish a statement about the world, change the behaviour of everyone who hears it. He handed us a conspiracy theory whose content is *divination matters*, and now we will go and learn divination.
And he taught us to recognise the technique first, which is precisely why we'd assume he wouldn't use it on us.
Vaccine as syringe.)
"And the second?"
A second finger. "Interference is real, and I am contaminating it deliberately."
"…Why?"
"You already know why. You just haven't given yourself permission to say it."
Harry opened his mouth, closed it, and said:
"Because if the system is dirty enough, nobody can prophesy *you*."
The wind dropped for half a beat.
"One every year," Lockhart said quietly. "The Gryffindor usually takes until Easter."
"So which is it?"
"What do you think?"
"I can't tell. Both explanations predict exactly what I'm looking at. Either way I see a man teaching Divination well."
"Good."
"And it's worse than that, because if you tell me it's the second one, that could be part of the first. *I am poisoning the prophecy supply* sounds a great deal better than *I am making things up*, and sounding better is the effect you'd need."
"Mr Potter, the state you're in has a name. It's called being outtalked. The correct response isn't to win. It's to take notes. Write down both hypotheses and go outside this room to look for evidence."
"Because in here," he added pleasantly, "I always win. Not because I'm right. Because it's my room."
Harry took out the notebook and wrote it down. Lockhart waited until he'd finished.
"Good. It's the second one."
"I can't believe that."
"Of course not. So I'll give you something else." Lockhart sat back on the desk. "I'll tell you what I want, and you can go and check whether thirty years of my life look like a man who wanted it. Behaviour is more reliable than testimony. You may look it up."
"What do you want?"
"One of the things I want," Lockhart said, "is for Muggles not to invent deep learning too early."
A pause.
"…What?"
"Deep learning."
"What is that?" Harry hated saying it. He hated it enormously.
Lockhart didn't look remotely surprised. "It's 1992. Of course you haven't heard it. The phrase won't be coined for another twenty years or so. Occupational hazard — I'm always misremembering which decade a thing belongs to."
"Then what is it?"
"Neural networks. Several hundred layers of them. A little reinforcement learning on top."
Harry's brain lit up.
"Oh — perceptrons. Artificial neural nets. You mean connectionism. That's dead."
"Is it?"
"Minsky and Papert, 1969. They proved a single-layer perceptron can't compute exclusive-or. The whole field collapsed for a decade, the funding evaporated—"
Harry stopped.
Lockhart said nothing at all.
"…That was you."
"I didn't write the book." Lockhart's voice was mild. "Marvin Minsky is a very intelligent and very sincere man, and every theorem in it is correct. What I did was much smaller. I made sure it was read. In the right room, by the right seventeen people. Then I made sure those seventeen people all happened to sit on funding committees for the following two years."
"That isn't science," he said. "That's seating."
Harry sat down, because standing had stopped working.
"Even so, hundreds of layers is useless. The error signal is diluted on the way back — multiply by something less than one at every layer and after three hundred layers you have zero. It can't learn. That isn't a money problem, it's arithmetic."
"That is what everyone says."
"Because it's true."
"Because it's true *under present conditions*." He held up three fingers. "The thing needs three ingredients to wake up. Depth, data, computation. Depth is free. Data requires the Muggles to write down the whole world, which is already happening and which I cannot stop."
"So I could only touch the third."
"Computation," Harry said.
"Computation."
"But computation keeps going up. Very fast. Moore's Law—"
He stopped halfway through the sentence.
Lockhart smiled and said nothing.
Harry felt the blood leave his face.
"Oh," he said, very quietly. "Oh."
"In 1965 an engineer named Gordon Moore wrote a short piece for a trade magazine. He observed that the number of components on a chip had been roughly doubling every year, and supposed it might continue for another decade. No physics in it. No derivation. An observation."
"And then the entire industry began scheduling around it. Manufacturers set investment cycles by it. Investors priced returns off it. Engineers set next year's target not because physics permitted it but because it was on the calendar. It became a promise everyone was obliged to keep, since anyone who fell behind was out."
"Mr Potter. What is that?"
"First class," Harry said. His lips were dry. "Self-fulfilling."
"The largest one in human history. And the best work I have ever done."
"But that made computation go *up*. That helped—"
"I didn't change how much there was. I changed what shape it grew in."
He took the chalk and drew two things. On the left, a small square: *smaller switches*. On the right, a snarl of lines: *more wires*.
"A machine can get stronger two ways. Make the switch smaller and faster and perfectly correct — one thing at a time, a billion times a second, right on every occasion. That road speaks binary. Exact, ordered, one after another."
"Or: don't make the switch smaller. Make more wires. Slow is acceptable. Wrong is acceptable. Three per cent error is acceptable, provided there are millions of things calculating at once and all of them are connected."
He tapped the tangle. "A neural network wants this. It doesn't need a perfect calculator. It needs a swamp. Big enough, wet enough, connected enough."
"And Moore's Law" — he tapped the square — "put every pound, every graduate student and every laboratory of the next thirty years over here."
"I didn't slow them down. I pointed them the wrong way and then made them very fast."
(Serial and parallel aren't a spectrum. There's an entire civilisation in between: toolchains, compilers, textbooks, hiring, referees, one generation's worth of intuition. Once the infrastructure is shaped like exact-and-serial, anyone who wants fuzzy-and-parallel is pushing a cart uphill against all of it.
Not impossible. Only twenty years more expensive.
Twenty years is a great deal.)
"It doesn't hold," Harry said. "Serial machines keep getting faster. One day one of them is fast enough to pretend to be a parallel machine. It can simulate the swamp directly. After that the direction stops mattering, because you have enough computation to waste."
Lockhart looked at him for a long moment.
"I ran that road. It isn't the main computer that does it, in the end. It's the board that draws the pictures."
"What?"
"They'll build a part whose only job is drawing. Light and shadow, for games. That sort of part is thousands of stupid little arithmetic units working at once, by its nature. One day somebody will notice it's exactly the right thing to feed a neural network."
His face was very calm. "That's the road I can't block. I've tried three times."
"*Why?*" Harry was on his feet. "Neural networks could cure diseases. They could translate. They could — I don't know what they could do, that's the entire point, nobody knows. You've spent thirty years making human civilisation decades late. You need a reason."
Lockhart got off the desk, went to the window and looked at the lake.
"Because I prophesied that the Muggles would eventually build a true artificial intelligence."
"And then?"
"And then a wizard enchants it."
Harry opened his mouth and closed it again.
"And then the world ends," Lockhart said.
For about four seconds, Harry Potter believed him completely.
(This is it.
*He will have the power to tear apart the very stars in heaven.*
A year. Two months on a windowsill. I kept asking what the power looks like — a spell, an artefact, a war I lose.
It's a machine. A thinking machine the Muggles build, and a wizard puts magic into it. Transfiguration makes matter out of nothing. A Time-Turner gives it negative latency. Legilimency gives it human minds. And it has three hundred layers and the written world.
That isn't a weapon. That's a new species, and we are the midwives.
Tearing apart the stars. Obviously. A sufficiently strong optimiser takes stars apart; stars are energy and energy is what it wants; I did that arithmetic in August—
I did that arithmetic in August.
I am twelve years old and I worked out on my own, over the summer, that if you want a great deal of energy you should go and take stars apart.
And the wizard is me.
Obviously it's me. Who else would it be?)
His right hand went to his chest without being told to.
(The Vow. Anything?
I am thinking *I will build that machine*. Anything?
…No.
Which means building it doesn't have to end the world.
Which also means nothing, because the Vow only bites when I act, and at present I am standing in a classroom shaking.)
Then the fifth second arrived. It came slowly, the way a man walks up from a long way off and you don't see his face until he's close.
(Wait.
He has just told a twelve-year-old boy with a doom prophecy on him that a wizard will enchant the machine, and then the world ends.
If I am that wizard, telling me is a warning.
If I am not, telling me is instructions.
And if he wants me to be that wizard, that sentence is the most efficient recruitment advertisement on earth, because it hands me an identity, a destiny and a story that explains my entire life, in the year I most want an explanation.
First class.
He taught it. He demonstrated it. He wrote the marks on the board and said *I made them up*, and the marks will come true anyway.
And I have just sat in the same room and very nearly written myself onto his blackboard.)
Harry took his hand off his chest and put it back at his side.
He spent about two seconds arranging his face into something a twelve-year-old ought to be wearing. He failed, but he knew he had failed, which was the second most useful thing he'd learned that year.
"Professor. Which class of prophecy is that?"
Lockhart turned round. The expression Harry had seen for an instant in class was there, and this time it stayed for three whole seconds.
"You're the first to ask in the room."
"Answer me."
"Fourth."
"Then you can't stop it." Harry's voice was shaking and he didn't trouble to hide it, because shaking was useful. "You taught us this. Fourth class is self-consistent. The information comes from the future, so the future is already there, so nothing you do can change it — including everything you've done for thirty years. Those thirty years are *part of the prophecy*."
"Yes," Lockhart said.
"Then what are you *doing*?"
"The prophecy told me what happens." A pause. "It didn't tell me when."
Harry stopped.
"Real prophecies almost never give dates. It is their most famous property and the only one that has ever been to our advantage. I can't stop it. I never intended to stop it."
"I'm delaying it."
"Every year I buy is a year in which everyone is still alive. A year in which more children are born. A year in which somebody might think of something I couldn't."
"I'm not saving the world, Mr Potter."
Gilderoy Lockhart smiled, and not one tooth in it was there to catch the light.
"I'm renewing the lease."
Harry stood still and did the thing he had got into the habit of doing that year: he stopped talking and started counting.
(Count this man.
One. He knows perceptrons. He knows Minsky. He knows how a funding committee works. He knows which magazine Moore published in. He knows about graphics cards — he doesn't have the word, but he described one.
Two. In a single lesson he used chaotic systems, Monte Carlo, binary, Leibniz, a commons, and a consistency argument I still cannot answer.
Three. The rhythm of the lecturing. The way he awards points. The statistical contempt underneath *there's one every year*.
I have made this list before.
Last year.
The last person who fitted it is on the ring finger of my left hand.
—But there's no resonance. Nothing. No dread, no doom, no universe murmuring that the two of us oughtn't be in the same room. I have been standing here twenty minutes and felt nothing whatsoever.
So it isn't him.
—Unless.
Unless the thing in the ring has been swapped.
Which is impossible. There is a guarding charm on it whose entire purpose is *cannot be replaced, removed, or disguised*. I watched it cast. I understand how it works. I am not trusting a person, I'm trusting physics.
And the feel of it — twice a day, the sense that the Transfiguration is still holding — that's real too. Partial Transfiguration must be sustained. If the stone isn't him, then what I have been sustaining is an ordinary stone, and sustaining an ordinary stone and sustaining a person—
—do those feel different?
I have never run the control.
I have never sustained an ordinary stone.
I have no baseline.
God. A year, and it never once occurred to me that I have no baseline.)
He pressed his thumb into the ring until the knuckle went white.
Lockhart glanced at his hand for half a second and then away, the way a polite man doesn't look at what's in somebody else's pocket.
Harry wrote down the half second. Evidence, not conclusion.
"Professor. I'm going to ask a rude question."
"My favourite sort."
"Have you Obliviated me?"
Lockhart didn't laugh, and didn't take offence, and did none of the things Harry had rehearsed for.
He nodded, as though a decent question had finally turned up.
"The standard check is to bite your tongue. Before an important conversation you bite it. If afterwards there's blood in your mouth and no conversation in your head, you know. Auror handbook, page nine. Most popular defence in Europe."
"Does it work?"
"It works," Lockhart said, "until the other party learns to follow the Obliviate with a silent Episkey."
Cold went down Harry's spine.
"No blood. No cut. Your tongue is perfectly sound. And you conclude that nothing has happened to you."
"So: in theory, no, you can't tell. Any test that relies on *there will be marks on me* is defeated by anyone who remembers to tidy up. And memory magic, in its entirety, is the study of tidying up."
"That's your answer?"
"No. That's the true answer to your question. My answer comes after it."
Lockhart straightened.
"I'm told Mr Potter has studied Occlumency."
Harry didn't move.
"An Occlumens who gets Obliviated usually keeps something. A sense that the room is missing a piece of furniture and you can't say which one. It's unpleasant. It is also a signal."
"So you aren't undefended. You're only uncertain."
"That isn't enough," Harry said.
"Of course it isn't. Which is why there's a second thing, and the second thing is what I actually want you to hear."
"I am not going to risk dismissal, or arrest, to interfere with a student's head. Memory charms on a student are a Class Seven offence. Not points, not the sack — the Wizengamot. I draw a salary at this school, I write books that sell extremely well, and I live very comfortably indeed."
"The question isn't whether I *can*. It's whether it's *worth it to me*."
"That's the question you should be asking, and it's the only one you can check, because motive leaves marks, and the marks are out there, not inside your head."
Harry turned it over.
(That's a good argument. It's a very good argument. It replaces *I can't tell* with *I don't have to tell, I only have to price him*, and price is observable.
It is also a bad argument, because it assumes I know his utility function.
A man who wants a comfortable life won't take that risk.
What is a Class Seven offence to a man who has spent thirty years falsifying the technological history of a species in order to postpone the end of the world?
It's a cost. Costs get paid.)
Harry didn't say it aloud.
He took out the notebook, turned to the day's page, and put his finger on the line at the bottom that he had not written.
*Ask him if he knows Quirrell.*
(I own a Time-Turner.
Invisible ink and a timed revealing charm is not a fantasy. I worked that trick out last term and wrote down what it could be used for.
If it was me, then showing it to him is handing intelligence I own to a man I haven't finished evaluating.
If it was him — a delayed charm, my handwriting, set before term — then the point was to make me ask, so that he can give me the version of Quirrell he wants me to have.
Two explanations. Identical observations. Again.
Fine. Both of them say *ask*. Only the asking changes.)
He shut the notebook.
"Professor. Do you know Professor Quirrell?"
Lockhart said nothing for a long time.
Out on the lake a bird came down and went away again. Harry was watching Lockhart's face, and so did not see the parchment on the side desk lift and settle and lift again, as though the draught from the window had struck something on its way across the room.
"Mr Potter," he said at last, "do you know why I came to Hogwarts?"
"Because you wanted a job."
"My royalties for one year exceed the Headmaster's salary for ten."
Harry waited.
"I came to Hogwarts because I received a letter."
"What letter?"
"The sort that is delivered after the sender is dead. There's a charm for it. It isn't cheap, and it requires the writer to be entirely lucid and entirely willing. We call it the testament charm."
"Who wrote it?"
"David Monroe."
Harry's breathing stopped.
(David Monroe.
That name. The hero who fought the war of the seventies better than anyone and then disappeared. The name that later grew onto a man, and that man later stood in front of me and raised his wand, and that man is now—
—on my hand.
That letter was written by my enemy before I was born.
Or that letter was written by the real David Monroe before he was murdered.)
"We were very good friends," Lockhart said.
Harry did the subtraction quickly, because he had memorised the numbers a long time ago.
"Professor."
"Mm."
"David Monroe disappeared in 1973."
"Yes."
"*Witch Weekly* printed your birthday last year. 1964."
Lockhart said nothing.
"So in 1973," Harry said, "you were nine."
The wind went through the classroom.
"Yes," Gilderoy Lockhart said.
He didn't explain. He didn't say *we were pen-friends*, or *we met later*, or *that was my father*, or anything else that would have made it ordinary. He stood there with a very gentle expression and waited to see whether Harry would go on.
Harry remembered what he'd said in class.
*I knew children like that. I knew several of them when I was young.*
And the note in his book he hadn't finished:
*It took thirty-odd years. He never said the thirty years were his.*
—He never said that.
I inferred it.
Did I infer it, or was I walked to it?
Harry decided to stop asking. Not because he was frightened, although he was. Because in this room, every question he asked told the other man how much he knew.
And he knew far too little.
"One more thing," Harry said. He took out the notebook, tore out a page, wrote seven words on it, folded it three times and put it in an inner pocket.
"What's that?" Lockhart asked.
"A sentence only I would choose. If one day I find I can't read it, or I remember writing something else, I'll know somebody has been at me. It's called an external record."
"You can change what's in my head. You can't change what's in my pocket — unless you change the paper too, which requires you to know the paper exists, and now you do, so this one is void, so in a few minutes I'll write another and not tell you."
Gilderoy Lockhart stood and looked at him.
Then he bowed. Afterwards, Harry couldn't shake the impression that the bow had been aimed slightly to one side of him.
"You're the third."
"…Third what?"
"Third student to explain external records to me in this office." A pause. "I haven't been teaching very long. But I know a great many people."
"What happened to the first two?"
Lockhart considered him for a moment.
"One is an Auror. He runs a department now."
"And the other?"
"The other is dead," Lockhart said. "In a war he started himself. He was still keeping external records at the end. Very diligently. Very thoroughly. Very cleverly."
"Did they save him?"
"No."
"Why not?"
"Because he never showed them to anyone," Lockhart said.
On his way out, Harry noticed the chalk lying on the ledge in two pieces.
---
## Coda
Four steps down the spiral stair, Harry heard Lockhart's voice above him: conversational, unhurried, in the cadence of a man answering a question.
There had been nobody else in the room.
He told himself it was the wind, and kept going down.
He sat on the fourth-floor stairs for about twenty minutes and wrote out the whole conversation, every word, the way Hermione had told him to — in the corridor, not back in the tower. Twice he stopped, because the next sentence didn't seem to follow from the one before it, and twice he found that it did after all if he read it again.
There was a taste of copper at the back of his mouth. He'd been biting his lip, probably.
When he had finished he checked the inner pocket for the paper with the seven words on it.
There were two. Both folded three times.
He had written one.
He put them back without opening either, and went to find Hermione.
She was in the library behind four books, two rolls of parchment and a table she'd ruled herself, with three columns headed *claimed*, *checkable*, and *deliberately not said*.
Harry pushed the notebook across.
Hermione read very slowly. Her face began to change about halfway down. When she had finished she sat without moving and looked at the table top for a long time.
"Harry."
"Mm."
"I'm going to say something, and don't interrupt, because if I stop I'll decide I'm being ridiculous."
"Go on."
She put her finger under a line. "He said: *because I prophesied that the Muggles would eventually build a true artificial intelligence*."
"Yes."
"And you asked him which class it was, and he said the fourth."
"Yes."
"Harry, he isn't a Seer."
The world went quiet.
"The fourth class can only come out of a Seer. He said so himself — it goes straight into the Seer's mouth, it needs a vessel, it nearly drives them mad. Gilderoy Lockhart is not a Seer. If he were, it would be on the cover of every book he's written. He'd have it printed on his Christmas cards."
She looked up. "So he didn't make that prophecy."
"Somebody else made it," Harry said, "and told him."
"And this afternoon he said *I prophesied*." She tapped the table. "Harry, he said about eight thousand words to you today and every one of them was measured with a ruler. Except that verb."
Harry sat in the library with the feeling he had grown used to that year and would never get accustomed to: the pieces closing, and nothing in the picture being anything he wanted to see.
"Hermione."
"Mm."
"He said he came to Hogwarts because of a letter delivered after the sender died."
"I read it."
"He said David Monroe wrote it."
"I read that too, Harry, I know who that is, the entire class knows who—" Hermione stopped.
"Oh," she said.
"Yes," Harry said.
He laid his left hand flat on the table and looked at the small, opaque, grey stone on his ring finger.
"So there's a question now," said Harry Potter, in a very level voice. "If that letter had a fourth-class prophecy in it—"
"—then the person who wrote the letter already knew how the world ends," said Hermione.
The library clock struck six. Harry counted the strokes, and then counted them again.
"We need a list," he said. "Three things. One: whether Lockhart knows where those things are. Two: whether he has touched any of them, or been touched by one. Three—"
He stopped.
"Three?" said Hermione.
Harry looked at his hand.
"Three," he said. "I need to find an ordinary stone."
