Note: This story contains major spoilers for Harry Potter and the Methods of Rationality. If you haven't read to at least chapter 94, turn back now. I don't own the rights to Harry Potter, nor the rights to Harry Potter and the Methods of Rationality.

The blood had been washed away. The terrace was immaculate, likely cleaned more deeply than it had been in hundreds of years. Yet it was still easy for Harry to find the exact spot, the junction of tiles where she'd drawn her last-for-now breath. He crouched down and placed a hand on it. Some part of his brain, the part that had internalized a hundred stories, had expected that the tile would still be warm to the touch, and when his fingertips found only cool stone the rational part of his brain had said a quiet I told you so. Hermione would probably have an empty grave somewhere, and the Headmaster would no doubt hold a funeral, but Harry wanted to say goodbye on his own terms. Not a final goodbye, just "see you in a bit". And for that, Harry wanted to be alone.

"Hi Harry," said a familiar voice from behind him.

Harry spun around, whipping his wand out in the process, and found it pointed straight at Hermione Granger. He could see straight through her. He slowly lowered his wand back down and stuffed it into his pocket, then took a moment to look at her. She was the same girl, with bushy hair and large front teeth, and she was wearing her school robes. Her legs, thankfully, were still beneath her. She was translucent, and all the color of her cheeks and hair had faded into a light blue. Harry was vaguely reminded of the hologram of Leia in Star Wars.

"You're a ghost," he said. Somehow it sounded even more ridiculous out loud than it had in his head.

"Yeah," she replied. She seemed like she was going to say something more, but decided against it.

Harry could feel tears welling up. He searched desperately for something he could say to distract himself. "Ghosts are just stored memories and behaviors with no awareness or life, accidentally impressed into the surrounding material by the burst of magic that accompanies the violent death of a wizard," said Harry. "You said that."

"Well," said the ghost of Hermione, "Actually it was Lucretius Featherbottom, who wrote that in The Tides of Ancient Deaths."

"But it's true, isn't it?" asked Harry.

"I don't know," said Hermione's ghost. "I had a violent death. I can still feel the trolls teeth piercing through my flesh, if I think about it too hard." Harry winced. "But I don't feel that much different." She looked down at her hands. "I feel cold, and I feel sad, but I still feel like me."

"Alright," nodded Harry. He'd thought that it would be years, or at least a single year as the lower bound, before he'd be able to see her again. And obviously this was just a pale reflection of the Hermione that had once been, but it was at least something. Not her, but a thing like a video or photograph. If he thought of it like that, it would be easier to deal with. "I'm going to bring you back to life," he said. It felt good, to say it out loud.

"I'd like that," said Hermione's ghost. "But if I'm not real, if I'm just a - a photograph, what's going to happen to me if you do that?"

"What do you mean?" he asked. "You'll be alive."

"No, I mean … there's this girl in the first floor girl's bathroom, a ghost that they call Moaning Myrtle, and she's been there for ages," said Hermione's ghost. "If you somehow brought her back to life, do you think she'd remember fifty years of moping around a bathroom? Or would it all just fade like a dream? If you bring me back to life, what happens to the person you're talking to right now?"

"Ah," said Harry. "Well, um, I hadn't quite thought that of that. I'm not sure that really factors into things."

"Why not?" asked Hermione's ghost with a frown.

"Well, you're not really a … a person, I guess," said Harry helplessly.

"I feel like a person," said Hermione's ghost. She crossed her arms, then thought about it for a bit and softened somewhat. "I suppose what I actually feel like is a ghost, but what I'm trying to say is that other than feeling cold and sad, which I think is perfectly natural for someone that's died, I don't feel like being a ghost has changed me much."

"I'd like to believe that you're really there, but that would mean believing a whole lot of other things that don't make any sense. I'd have to accept that there's something like a soul. And if there are souls then why don't muggles leave behind ghosts?" asked Harry. "Why aren't there any original discoveries by ghosts? I've been in Professor Binns history class the whole year, and he never deviates from the lectures or even seems to notice that I'm there."

"Harry," she said gently, "We've never had this conversation before, have we? It's original, isn't it? If I were just a recording, which I don't think I am, I couldn't make up new responses on the spot."

"Unless I'm somehow projecting responses into you, like with the Sorting Hat, or Parseltongue, or Dementors, or any number of other phenomenon I've already been exposed to," said Harry. "Besides that, I've talked with a ghost before, and they're not really conscious."

"The only ghost that you've really been around is Professor Binns. Have you ever thought that perhaps Professor Binns is just like that? Your father taught at Oxford, didn't he ever mention professors that drone on without caring about their students? Maybe Professor Binns is the exception to how ghosts normally behave. You had a name for that, when you base all of your observations off of looking at a single example of a thing."

"An n of one problem," said Harry distantly. She was making sense. The fact that she was making sense was a point in favor of her not actually being just the magical equivalent of a photograph. And she'd told him the title of the book she'd been quoting from, which might have been dredged up from Harry's own subconscious but was at least something that could be checked to put some constraints on the problem. "What do I think I know about ghosts, and how do I think I know it?"

"What do we think," said Hermione's ghost.

"Alright, we," replied Harry. "We think we know that ghosts are something like a recording of patterns but not actually conscious as such."

"And we know that because I read it in Lucretius Featherbottom's The Tides of Ancient Deaths," said Hermione's ghost.

"But how did he know it?" asked Harry. "He was a wizard, so he probably didn't do any experimentation. The same would go for other wizards or witches who wrote about ghosts. Maybe there's a way to take a reading of the place someone died, to see the magic associated with the ghost. Are ghosts even tied down to one physical location?"

"I don't think so," said Hermione's ghost. "The Grey Lady didn't die in Hogwarts, I don't think, nor did the Bloody Baron." The Grey Lady was the House Ghost of Ravenclaw, and the Bloody Baron was the House Ghost of Slytherin. "The two of us could test that easily enough."

"So the proposal of ghosts being imprinted also holds that they can somehow move from the place that they died?" asked Harry. "That sounds like a complexity penalty to me, but we'll have to research the magics involved. Tabled for now. Moving on."

"I think I'm conscious," said Hermione's ghost.

"I'm sorry, but that doesn't mean anything," said Harry. "You're just saying that you've conscious, which you could fake by setting up a really simple Artificial Intelligence program like ELIZA. Even my mokeskin bag has a certain level of natural language processing. What we need is an operational definition of what it means to be conscious, one that we can run tests against." He didn't want to admit it, but for a moment it really did feel like the old days, back before all that business with Draco and the blood cooling charm. He still regarded it as a fantasy though, one last day with Hermione as a way to say goodbye. It was safer to think of it that way, so that his heart wouldn't break when he came back tomorrow and she couldn't remember anything.

"Alright," said Harry, "Let's do some quick tests."

"Okay," said Hermione's ghost. She had the same intent look on her face that she always got when a test was about to be administered. Hermione Granger had loved tests, and apparently her ghost did as well.

"You give me a triplet of three numbers," said Harry, "And I'll tell you 'Yes' if the three numbers are an instance of the rule, and 'No' if they're not. I am Nature, the rule is one of my laws, and you are investigating me. You already know that 2-4-6 gets a 'Yes'. When you've performed all the further experimental tests you want-"

"Harry, we did this on our very first day on the train," said Hermione's ghost.

"Oh," said Harry. "Right." That was one of the little lesson-games that he kept in his back pocket at all times. He felt somewhat embarrassed that he'd forgotten they'd done it before. "Let me pick a new set of rules and we will at least be able to see whether you can do science. First, real quickly, can you still do math? What's eleven times forty-three?"

"Four hundred and seventy-three," said Hermione's ghost with a derisive snort. Hermione had always been excellent at math. It took Harry longer to get the answer than she did, and that was another constraint on the problem of what a ghost really was. They could do math, apparently.

"Alright," said Harry, "Good enough." He reached into his mokeskin bag and said "Dice," and then took five of them out of the bag that had appeared and put the rest back. He'd had vague notions of playing a game of Dungeons and Dragons at some point, back before he'd come to Hogwarts, and there wasn't any real reason not to keep a bag of dice in the mokeskin bag. Each of the dice had six sides. "This is a pretty famous one that you hopefully haven't heard of before. The name of the game is petals around the rose. I can tell you the result of a roll, but nothing else. Are you ready?" Hermione's ghost nodded, and Harry rolled the dice. 4-1-6-3-6. "Two," Harry declared.

Hermione's ghost stared at it. "Does the order matter?" she asked.

"That's for you to figure out on your own," said Harry with a faint smile. It was the first time that he'd smiled since - well, in a while.

"Again," she said.

5-6-5-4-4. "Eight," said Harry.

"Again," she said.

2-6-2-4-1. "Zero," said Harry.

"Zero?" she asked.

"Zero," Harry replied. "Come on, start generating some hypotheses, I don't really care if you get it, I just want to see if you can really reason."

"Well you may not care, but it's very important to me that I arrive at the correct answer on my own," said Hermione's ghost. She stared down at the dice. "So far, the range is eight to zero and the answers are even. But I need more data. I was thinking that perhaps you add, subtract, or multiply the dice, but that wouldn't give zero for that last one unless you could do something with order of operations. Two plus six divided by two minus four minus one would get an answer of zero, but that has a complexity penalty, and besides that doesn't fit with the previous two results."

Harry almost cracked a joke about her teaching math at Hogwarts when he remembered that she was dead. Professor Binns had gotten a job, but he couldn't imagine Hermione teaching basic math to people that were her age when she died. He could maybe imagine Dumbledore giving her the position though, because Dumbledore was insane. He didn't say any of that, and rolled the dice instead.

6-5-6-2-2. "Four."

3-3-5-1-1. "Eight."

2-4-6-1-3. "Two."

5-3-4-3-5. "Twelve."

"That's the highest I've seen so far," said Hermione's ghost with a frown. "Odd numbers seem to give a higher result."

2-2-6-1-4. "Zero."

"What was the name of the game?" asked Hermione's ghost.

"Petals around the rose," said Harry.

"Oh, well that almost makes it too easy," said Hermione's ghost. "I could figure out that the answer's always even easily enough, and that it has something to do with which numbers are rolled. It's not a matter of adding and subtracting the numbers themselves, or anything like that, it's just a simple substitution and then addition. Six, four, two, and one are worth zero, five is worth four, and three is worth two. And it's called petals around the rose because you can imagine the center pip as the center of a flower, so on dice that have a center pip you count the outer pips, the petals on the flower."

"You got it," said Harry. He couldn't resist smiling. "Well if you could figure that out, then I don't think there's anything standing in the way of doing original research." He had trouble seeing how he would get around the projection conjecture. If he'd thought about Hermione becoming a ghost before she died, he would have had her write down a piece of information that was known only to her.

"What about memories?" asked Hermione's ghost.

"That's not part of being conscious," said Harry. "Do you remember me lending you a book on neuropsychology when I was saying that brain damage disproves the existence of a soul?" Her ghost nodded. "Well, there are types of brain damage that make people unable to form new memories, but you'd still say that they're conscious, wouldn't you?"

"I suppose," said Hermione's ghost.

"Memory, at least long-term memory, doesn't have to be a condition for consciousness then. Obviously it's not preferable to be without the ability to make memories, but it's not a real impediment to consciousness." He frowned. "But we should do some tests on that later. It would explain why ghosts aren't known to have done original research, and why some of them forget what century they're in, and why Binns teaches the same history class every year. There's still the open question of what your brain is running on, since obviously you don't have any neurons firing anymore."

"Oh," said Hermione's ghost. "I thought that perhaps it was just my soul taking on corporeal form." Harry gave her a funny look. "And yes, I remember that you don't believe in souls, obviously."

"It's just that -" Hermione's ghost began raising one finger "-there's no real-" her finger slowly moved up "-evidence." She was pointing at her own face. "Oh come on, you can't just use yourself as an example of a soul. Besides, we agreed that you were a ghost and not a soul."

"I can be both," said Hermione's ghost with an offended look.

"Brain damage disproves the existence of a soul," said Harry, though he was somewhat less certain of that now that he was talking to someone who didn't even seem to have a brain. "Phineas Gage got a metal rod through his head and began acting wildly different. This is pretty basic muggle science."

"Maybe it doesn't apply to wizards," said Hermione's ghost.

"What?" asked Harry. "Of course-" He stopped and closed his mouth. He'd been about to say "Of course wizards get brain damage," but then he'd realized that he didn't actually know whether or not that was true. It certainly seemed like they should, but Harry didn't have any evidence that this was the case. It stood to reason that their brains were the same, since with the exception of the magic gene they shared the same genome, and could interbreed. Yet he'd never actually done any research to see whether wizards had the same brains as muggles. After all, a wizard's brain shrunk to the size of a walnut when they turned into a cat, and that certainly suggested that there was something odd going on with how they thought, even if that wasn't entirely indicative of a soul. There were many questions being raised by this line of thinking, and there was one very sensible course of action to take. "Let's see how far you can walk," said Harry, "I think it's time for us to do some research."

"Madame Pomfrey, do wizards get brain damage?" asked Harry.

Madame Pomfrey's eyes were wide, moving quickly between Harry and Hermione's ghost. "Oh Harry," she said softly, "It doesn't do to associate with ghosts, you'll only drag out the pain and sorrow of her passing." Madame Pomfrey's eyes were red from crying, and it occurred to Harry that he'd been somewhat of a fool to come here, and more of a fool to bring the ghost with him. He was sure that Madame Pomfrey was feeling the pain and numbness Hermione's passing, and she'd seen what the troll had done to the Weasley twins, it just hadn't been obvious until he took a moment to think about it. Harry himself had wanted to be alone just an hour before. But now there was a mystery to solve, and whatever Pomfrey was feeling, this was Important. If anyone knew about the affect brain damage had on wizards it would be the school's healer.

"I just want to know whether wizards ever suffer from brain damage," said Harry. "Then I'll leave."

"Of course they do," said Madame Pomfrey.

Harry felt his heart sink. He wasn't sure why he'd wanted her to say no. Possibly it was because he'd still held out hope that there was something beyond death, some way that it wasn't the worst thing in the world, even if there was only an afterlife for wizards. Of course, the nonexistence of brain damage in wizards didn't mean that there was such a thing as a soul, and a soul didn't mean that there was an afterlife, but brain damage very much seemed to rule out a soul.

Hermione's ghost spoke up. "Madame Pomfrey, when wizards suffer from brain damage, do their personalities change?"

"Heavens no," said Madame Pomfrey, holding her hand to her chest. "Why would they? They get headaches, or black out, but I've never heard of anyone going to St. Mungo's with a different personality, at least not from something that happened to their brain."

Hermione turned to Harry and tried to smile, but it came out looking far too sad.

"Wait," said Harry, "What about alcohol or caffeine? Wizards still have stimulants and depressants, and those change how people behave, so are you telling me that a soul is affected by those things too? We're talking about the same thing when we talk about a soul aren't we, an extra-physical thing that holds personal identity in some fashion?"

"Oh, certainly there are things that can temporarily act on a person," said Madame Pomfrey, "But none that change the way a person is forever, not down to their core. Even strong magics like a love potion wear off after a time, and the person will go back to normal."

"Okay," said Harry, turning to Hermione's ghost. "That's not conclusive, we need to do more research. I mean, that would indicate that there's a difference between muggles and wizards, if we accept that's true, but that doesn't tell us what that difference is. I'm not going to say that I refuse to believe that souls exist, because if you live in a universe where souls exist then that's what you want to believe, even if it doesn't make any intuitive sense. And that doesn't actually answer the question of why muggles don't ever become ghosts."

"Oh dear," said Madame Pomfrey, "I'm afraid muggles don't have souls."

"That - what?" asked Harry. He felt completely befuddled. "You're a blood purist?"

"Oh no dear," said Madame Pomfrey. She adjusted her apron. "Though I'm certain Dumbledore will tell you otherwise, it's a simple matter of medical fact that muggles don't have souls, and I don't care how politically incorrect that might be to say in the modern age. I don't know a single healer who would disagree with me. That doesn't mean that we should treat them unkindly, of course. There are those who think that just because a person doesn't have a soul means that they're not a person at all, and I hold no truck with that."

"But … that's - how do you know that muggles don't have souls?" asked Harry.

"It was one of the tactics that He-Who-Must-Not-Be-Named used," said Madame Pomfrey, "If you feed a muggle Polyjuice potion, they won't be the same person anymore. They'll believe that they are whoever they were turned into, since there's no soul to provide constancy during the transformation."

Harry opened and closed his mouth a few times. "That's, the security implications of that, if you had a captive muggle-"

"Were I you, I would say no more," said Dumbledore from the doorway. Harry hadn't heard him come in. "You have a penchant for novel solutions that might be used against you by your enemies, and it is clear that Hogwarts itself is no longer entirely safe from those enemies." He nodded towards Hermione's ghost.

"Headmaster, why didn't you tell me any of this?" asked Harry. "There were precautions that I could have taken to ensure that I wasn't-" he caught the Headmaster's look "-that no one was able to Polyjuice into me."

"Precautions you weren't already taking, or that weren't already taken for you? Your robes are charmed," said Dumbledore. "They capture and evaporate any stray hairs, along with other material that one might use in such a potion."

He felt his head spinning. If a transformed muggle would end up with the same brain as a wizard when Polyjuiced, that would mean that you could take a willing or unwilling muggle, feed them Polyjuice, and then have a tied up copy of your enemy. From there you could feed them Veritaserum, or use Legilimency if they weren't an Occlumens (and how did that even work, was Occlumens explicitly magical or could it be learned by anyone who wanted to go through the mental exercises?), and break the enemy's security protocols wide open.

"I believe that this is a conversation that might be better had in my office," said Dumbledore. Harry nodded. "Miss Granger, you are welcome to join us as well."

They walked down the corridors of the castle in silence. Hermione's ghost didn't walk, but instead floated, with her hair waving behind her and her feet pointed towards the floor. She hadn't done that before, and Harry momentarily worried that it meant she was becoming more ghost-like before his eyes. He desperately wanted her to stay as she was, the best companion that he could have hoped for in his time at Hogwarts.

"You're floating," he said. "You were walking before." Dumbledore turned to look between the two of them, but kept moving all the same.

"You would float too, if you could," said Hermione's ghost.

Harry had to admit that it was true.

The reached the spiral staircase, and Dumbledore said the password, "Cockroach clusters", which was another kind of sweet. It was terrible security. Harry had a letter in his mokeskin pouch that contained a list of every kind of sweet. The letter was a Howler, a type of magical letter that said things when it opened up, and it had only taken a half day to figure out how to get it to say those things really fast. If Harry ever wanted or needed to get into the Headmaster's office, it would be as simple as opening the Howler and having it iterate through the list. Of course, there might be other forms of security to get past, but it paid to have such a weapon in his arsenal.

Harry sat down in the over-stuffed chair in front of the Headmaster's desk, and Hermione stood beside him.

"I had feared you would become a ghost," said Dumbledore to Hermione in a low and heartbroken voice. "Ghosts form most often from those afraid of death, and your friendship with Harry Potter would seem to have provoked that fear in you." Hermione lowered her head, feeling the sting of being chastised even from beyond the grave. "I have failed you in more ways than one."

"Headmaster," said Harry, "Why didn't you tell me that ghosts were like this?"

Dumbledore raised his eyebrows. "You and I had a conversation, long ago, on the nature of souls. You quoted Featherbottom to me, and I assumed that you had made up your mind on the matter of ghosts. As I recall, we moved on to much firmer evidence, the Veil of Souls chief among them, and you rejected that evidence as well. I have not often found that arguing against someone who has made up their mind to be good practice, as it tends only to firm their opposition."

Harry glowered at him. "And why was I never told that there's evidence that muggles don't have souls?" That wasn't technically true. He'd been told by Draco and simply assumed that it was blood purist idiocy without a shred of evidence to back it up.

"I shall have to speak with Madame Pomfrey about what's appropriate to say to children," said Dumbledore. "There are competing theories on the matter. Some say that muggles have no souls, while others contend that it is simply a matter of the way that wizards interact with magic, and that muggles have an immortal soul which continues on just the same without being seen or felt, a position that I regularly take in the Wizengamot."

"If I put a Polyjuiced muggle into an MRI machine, what would I see?" asked Harry.

"A muggle device, I presume?" asked Dumbledore.

"A magnetic resonance imaging machine, it's used to look at someone's brain," said Harry. "You can map out changes in the brain on a coarse level."

"Ah," said Dumbledore. "I have not tried it myself, but my experience with Animagi would suggest that their brain would change along with their body. Harry, how did you think that an Animagi was able to continue to think, if souls did not exist? It is only through the will of the person's soul that the animal form can think and act as a person would."

"I thought," began Harry. He stopped to think for a moment. "I thought that perhaps the brain was shrunken down in size and rewired to provide the same response to stimulus."

"Do you realize what an extraordinarily complicated bit of magic you propose?" asked Dumbledore.

"You're already turning people into cats!" Harry practically shouted.

"A cat is a known form," said Dumbledore, "And thus much easier to work with than the hybrid that you propose. Polyjuice potion is extraordinarily expensive and difficult to create, and you believe that on top of changing one person into another, it leaves the brain as a constant?" He shook his head sadly. "I sometimes forget that you are only in your first year, and then in conversations like this is becomes apparent. We have schools for a reason, to teach you the limits of what magic can and cannot do."

Harry stared at the Headmaster. "So you're saying that magic keeps a fully up to date copy of my - of my essence, my personality, my feelings and thoughts. And if I were to drink Polyjuice potion, magic would keep all of that going without an actual brain." He turned to look at Hermione. "And that's what happened to Hermione?"

"You put it in odd terms," said Dumbledore, "But that is essentially correct."

"How do we fix it?" asked Hermione's ghost.

"There is no way to undo death," said Dumbledore, which Harry didn't believe for a second.

"Can I stop being a ghost?" she asked.

"That would be like dying all over again," said Harry. "If you can keep living as a ghost, why wouldn't you?"

"It's cold," said Hermione's ghost. "Cold and sad. I'll never grow up, never see my parents again, or have my first kiss or get an Outstanding on my O.W.L.s. Ghosts can't even eat. Would you want to live like this, if you could never do the things that bring you pleasure?"

"Of course I would," said Harry.

"That's a terrible thing to say, Harry Potter," said Dumbledore. "Hermione, I am sorry, but someone who becomes a ghost stays as one forever. There are ways to motivate them, or to keep them contained, but once you become a ghost you are chained to this realm forever, never to pass into the next."

"I'm a ghost forever?" asked Hermione's ghost. She began to cry, and Harry's heart broke just a little bit more.

"It's not so bad," Harry began. She turned away from him, and fled from the office, going straight through a wall. For a moment he made to go after her, but settled down in his chair and glared at the Headmaster. "Souls exist," said Harry.

"They do," replied Dumbledore.

"And the Veil that you spoke of earlier, you believe that souls pass through it into the next world?" asked Harry.

"I do," said Dumbledore. "You have said that it is an uninteresting fraud, I recall, but it was built with magics more powerful than those known in modern times. The Veil predates the Ministry itself, which was built around it to contain it. Perhaps it was a mistake to have you raised by muggles, if you believe wizards to be so stupid."

"That proves nothing," said Harry, though it did somewhat lower the odds that it was a fraud given the trouble that someone would have to go through and the scrutiny that the Veil would presumably have been under. "Even if I were to accept that souls exist in some form or another, that says nothing about the existence of an afterlife." Harry turned and looked backwards, in the direction that Hermione had fled. "I should really go after her." He got up from his chair and turned to leave.

"Harry, I will not prohibit it, but nothing good can come of a continued relationship with the ghost of Miss Granger," said Dumbledore. Harry nodded but said nothing, and continued down the stairs. When he got there, he found that Professor Quirrell was waiting for him. Somehow, he wasn't surprised.

"I have heard," said the Defense Professor, "That you have been making inquiries into the nature of the soul."

"I was," said Harry. "The Headmaster said some things that made me think."

"Oh?" asked Quirrell.

"Do you believe in souls?" asked Harry.

"Of course," said Quirrell. "It's obvious that they exist to anyone who gives it the merest thought."

"Perhaps I'm asking the wrong question," said Harry. "What exactly is a soul?"

"It's the animating intellect, the spirit, and the essence of being," said Quirrell. "It is what exists beyond the body. Animagi, Polyjuice, paintings, photographs, ghosts, all these work on the principle of the soul. There is even legend of a dark magic which can be used to split the soul, such that a wizard can survive beyond death."

Harry was very quiet for a long moment. "Why don't muggles have souls?" asked Harry. "Why are they different?"

"Walk with me," said Quirrell. Harry did, not really paying attention to where they were going. "Of all the questions to ask, you ask of muggles?"

"My parents," said Harry, "What does it mean that they don't have that same extra-physical personhood that wizards appear to have?"

"They cannot think," said Quirrell. "Not like you or I. They have memories, which can be obliviated or charmed away, but do you know what you see if you attempt Legilimency on a muggle?" Harry shook his head. "You would see nothing at all. No thoughts going on behind their eyes, no animating spirit. It's like looking at a perfectly flat lake, undisturbed by wind or wave. And if you want to replace that calm surface, it's as simple as giving the slightest push."

Harry shuddered, and hoped that Quirrell wasn't speaking from experience. "They still speak though, they still think and dream and laugh," he said in a rush. "They've written whole treatises on the nature of philosophy." Harry suddenly wished that he'd read more of them.

"Empty words," said Quirrell. "The product of a mechanical process, or electrical impulses and chemical reactions. Have you never wondered whether there was really something animating the muggles? With magic we can look into their minds and see. Wizards have souls, and muggles do not. It is incontrovertible."

"Just because you can't see anything with Legilimency - no, I'm sorry, that's the wrong tactic to take here. Let's say for a moment that muggles don't have souls, that there's not some extra-physical identity tied to them. That doesn't mean that they don't think the same as you or I. Their psychology is identical, or near enough. They behave in the same way that we do."

"Yet there's nothing behind their behavior," said Quirrell. He gave Harry a strange look. "Do you not see that? Perhaps you would need learning as a Legilimens for yourself. But even with a Penseive the difference is clear. A muggle's memories do not take on the same biases and warpings as a wizard's do. Their memories are of crystal clarity, untainted by thought."

"Muggles practically invented bias," said Harry.

"They convincingly fake bias," said Quirrell.

Harry said nothing. He was distinctly uncomfortable without having access to the same body of facts as everyone else. There were a number of books in the library about souls, though most of them were in the restricted section, and Harry hadn't taken the time to look through them. He'd thought that they were just fluff, the same kind of thing that you could find in a muggle bookstore, empty speculation that was pulled from thin air.

"I need to gather more data," said Harry. "If I take the soul hypothesis as it's been presented to me, there are still a few things that don't make sense. The Killing Curse, for example. You said that it works on anything with a brain, and Professor McGonagall said that it works by separating the soul from the body. But muggles have brains, I'm completely sure of that, and if you were right then the Killing Curse still kills them."

"The Killing Curse does two things when it strikes the body," said Quirrell. "First, it cuts the soul away from the body, if one is present. Second, it immediately stops all electrical activity in the nervous system of the creature so struck. The first method is useful only against wizards, the second against nearly everything else, with a few notable exceptions such as ghosts, which have no body to cut the soul away from or nervous system to shut down."

"And how do you know this?" asked Harry.

"You have heard of the Dark Wizard Grindelwald?" asked Quirrell.

"The one Dumbledore defeated," said Harry.

"Yes," replied Quirrell. "Grindelwald had a burning curiosity within him that is common to the dark wizards. He wondered, as you did, what would happen when someone was struck by the Killing Curse after they'd had their soul removed."

"How … how do you remove a soul?" asked Harry. "How is that even possible?" Something tickled at his memory, a discarded scrap of information marked as not true. "Dementors."

Quirrell nodded. "Dementors do not act simply to inspire fear and drain happiness from people. They will plant their bony lips upon your face, and you will have no urge to stop them, and they will suck your soul straight from you. It was this dark magic that Grindelwald used. In fact, it is still used to this day as a means of execution by the Wizengamot. What's left behind is a body, brain still apparently active and heart still beating, but utterly soulless. No memories, no thoughts, a blankness that cannot be faked or recovered from."

"That's terrible," said Harry. He felt nauseous. "That's nearly the most terrible thing that I can imagine. Why? Why do it that way, why not simply kill them dead? Is it retribution?"

"Imagine for a moment that you had seen the Veil which sits at the heart of the Ministry of Magic, around which the government of magical Britain had been built." Quirrell had something feral in his eyes. "Imagine that the wizards who held control of the Veil had tried certain courses of action, nothing like science, but killings directly in front of the Veil to see the movement of a soul in flight. Not the wizards of today, but those of Merlin's time perhaps. Imagine that there is this artifact, which by all accounts seems to lead to the afterlife, and imagine the thousand tales of what lies beyond. The Wizengamot certainly doesn't know what the next world might contain, but surely it occurred to them, as it would likely occur to you or I, that criminals pass through the Veil as well. Criminals, heretics, dissidents, and dark wizards, all would have to be defeated a second time, and in many cases a second victory was not such a sure thing. If there exists a method to rid yourself of an enemy completely and forever, well, I should hardly think that they would stand on a moral high ground and not use it."

"They're preparing for a war," said Harry. He felt the blood drain from his face. "They're preparing for a war in the afterlife, whatever it might be."

Quirrell let out a humorless laugh. "Mr. Potter, what stakes did you think we've all been playing for?"

Harry walked to the terrace. His head was still swimming with all the things he'd been told. He had no idea where to begin with assessing their truth values, and that was only a precursor to figuring out what to do next. Yet he had to go talk to Hermione, to convince her that everything was going to be alright. It was what a good friend would do.

"Hi Harry," said Hermione's ghost. She floated above the cleaned tiles. "I think I'm a ghost."

Harry only nodded. He'd steeled himself against that response, but it stung all the same. He'd read up on books about dealing with ghosts, on the ways of speaking to them, and he'd special order muggle books about dealing with people who'd suffered from anterograde amnesia. Hermione lived on, in a crippled form, but he'd restore her to life if it was the last thing he did. The day's revelations had changed little, only piled on more mysteries to solve; he was still going to have to optimize the world.