This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 99, 100, and 101The previous thread is at nearly 500 comments. 

There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.) 

The first 5 discussion threads are on the main page under the harry_potter tag.  Threads 6 and on (including this one) are in the discussion section using its separate tag system.

Also: 1,  2,  3,  4,  5,  6,  7,  8,  9,  10,  11,  12,  13,  1415,  16,  17,  18,  19,  20,  21,  22,  23,  24,  252627

Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically:

You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).

If there is evidence for X in MOR and/or canon then it’s fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that “Eliezer said X is true” unless you use rot13.

Harry Potter and the Methods of Rationality discussion thread, part 28, chapter 99-101
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"Tell me, son of Lily, do the Muggles in their wisdom say that soon the skies will be empty?"

Interesting tie-in to:

"HE IS HERE. THE ONE WHO WILL TEAR APART THE VERY STARS IN HEAVEN. HE IS HERE. HE IS THE END OF THE WORLD."

So the centaur and Trelawney seem to be reading from the same playbook. Any guesses to who the centaur approached sixteen years ago and what lines he crossed? Seems like a plausible time to be Lily, no? Could possibly be the payoff to this from Chapter 1:

"...And I begged her to use some of that magic on me so that I could be pretty too, even if I couldn’t have her magic, at least I could be pretty.”
Tears were gathering in Petunia’s eyes.
“And Lily would tell me no, and make up the most ridiculous excuses, like the world would end if she were nice to her sister, or a centaur told her not to – the most ridiculous things, and I hated her for it."

“There is nothing above the folly of men,” whispered the voice from the emptiness. “There is nothing beyond the destructive powers of sufficiently intelligent idiocy, not even the stars themselves.

“The Sun is very large, after all; I doubt the Dementor would have much effect on it. But it is not a test I would like to try, Mr. Potter, just in case.”

“Is the Sun still in the sky?” said Professor Quirrell, still with that strange gentleness. “Is it still shining? Are you still alive?”

The destruction of the sun is a recurrent theme with Quirrell.

[-][anonymous]170

the world would end if she were nice to her sister

Plausible, if her being nicer to her sister is why Harry got the upbringing he did instead of the canon one.

[-]jefftk190

Via: "Lily is nice to Petunia" -> "Lily makes Petunia prettier" -> "Petunia ends up with Michael and not Vernon" -> "Harry learns science instead of ptsd".

0HungryHippo
It's even worse if one believe that Harry is Harry!Mort.

"...The stars themselves proclaim your innocence, ironically enough."

9ygert
This seems to be the case. It all ties together to nicely not to be. Sixteen years ago, Firenze (I assume that is who the centaur is, from his views and attitudes) told Lilly that "the world would end if she were nice to her sister", based on the same prophecy based on which he tried to kill Harry: One that was similar to the one Trelawney made. Remember also the twice-repeated wave of prophecies over the world, despite the fact that we are told that disturbances in time are never enough to cause more than a single prophecy. It would make sense that if any prophacy could be of such import, it would be one about the end of the world.
6drnickbone
What puzzles me about this: * The centaur foresees that Harry is "the end of the world" * Quirrell has also heard that Harry is"the end of the world" * Quirrell is really afraid of this (it's the only credible threat to all his horcruxes) * The centaur is conveniently about to kill Harry But then Quirrell saves Harry's life. Why? Is the only reason because Quirrell has already seen future Harry in Chapter 100 (under the cloak), so knows that Harry has to make it out alive somehow, so he might as well do the saving?

If Quirrell wanted Harry dead, he would kill him. Even without being able to use magic against him directly, there are plenty of ways for him to do it.

I think Quirrell still wants or hopes something from Harry. Maybe it's just that Harry needs to be still alive for the "blood, bones, flesh" rituals, but I think it's something much more specific, linked to Harry's dark side and why their magic can't interact.

6Tedav
Personally, I think Quirrell killed Hermione, in the hopes of getting Harry to actually figure out how to defeat death - something no one else has ever done. The reason he was happy when he heard the prediction that Harry would break the Universe is that this was near-confirmation that Harry would be successful. In short, here is my version of Quirrell's plan: 1) For deniability reasons, be anti-resurrection from the start, and horribly worried about what Harry will do - tell Harry this 2) Kill someone Harry won't allow to stay dead (Hermione) 3) Become convinced by Harry to help with the plan - provide magic knowledge he doesn't have access to on his own 4) Use any means necessary (Unicorn blood) to stay alive until Harry is close to success 5) Harry is now the solution to whatever is slowly killing you
2Velorien
That is the exact opposite of how he reacted. His attitude after hearing the prophecy can be summed up by his words to McGonagall, which are consistent with everything he does thereafter:
1Tedav
I would say that his request to McGonagall is consistent with my theory - he knew that her attempts to stop Harry would have the opposite effect. I am guessing that Quirrell has some alternate interpretation to the prophecy. One possibility for this is "The End of the World" corresponds to an change to the natural order that makes the world unrecognizable, such as the removal of mortality. It is possible that instead of burning up his own life to destroy all the dementors or defeat death, Harry could burn up some stars, which could explain the rest of the prophecy. I'm not saying that I am correct, but I still see no actions that are inconsistent with my theory. I think part of the confusion is that we are interpreting the punctuation differently. I don't interpret your second quotation (first quotation from the text) as meaning that he was happy, until interrupted by hearing the prophecy, but rather that the prophecy was the reason he had smiled.
1Velorien
Regarding the sequence of events, here's how it goes: (quoted from hpmor.com rather than the .pdf this time for greater accuracy) I really don't see how you can get any sequence of events out of that other than "Trelawney is about to make prophecy -> Quirrell analyses Harry's emotions and is happy with what he finds -> Trelawney makes prophecy". Quirrell doesn't even get a full stop at the end of his thought before the quote marks open for Trelawney to speak.
0Tedav
Fair enough. I must admit, this makes my theory less likely, but I still don't see your reading as the unambiguously correct interpretation, but I will freely cede that it look plausible that it is an interrupt, not an elaboration. This may, in part, stem from the fact that I am a big proponent of using "-" in my writing, and my usage is somewhat nonstandard. Even if that is right, I don't think it rules out my guess about Quirrell's plan, but again, I'm significantly less confident now.
3drnickbone
Not strictly true: if Quirrell both wanted Harry dead and was able to kill him then he would kill him. It seems to me we have to consider two hypotheses, each of which is problematic:. 1. Quirrell can't kill Harry 2. Quirrell can kill Harry, but Harry is so supremely valuable that Quirrell is willing to risk the destruction of the whole universe (including himself, and all his horcruxes) to keep Harry alive. Both hypotheses contain a puzzle. If Quirrell is unable to kill Harry, why is that? (One guess: his offering to spare Harry in exchange for Lily's life created a binding dark ritual, and Quirrell can't get out of it.) Alternatively, if Quirrell is able to kill Harry, what exactly makes Harry so supremely valuable? Using Harry in a resurrection ritual, or as a puppet ruler of magical Britain, don't seem to be high enough value when measured against the risk, do they? My initial thought was that Chapter 101 provides evidence against 1 and in favour of 2: if Quirrell's problem is an inability to kill Harry, then Quirrell could just let the centaur do the job instead. But then, the Time-Turner evidence means that Quirrell already knows that the centaur's attempt will fail anyway, so he might as well stop it himself (and stay in Harry's favour). I still don't think we can rule out hypothesis 1.
2bramflakes
Quirrell said he considered killing Harry at some point, so there are 3 possibilities: 1) he's lying, 2) there is a dark binding ritual that he doesn't know about, or 3) there is no dark ritual. Considering his knowledge of dark rituals we can rule out number 2, and since there isn't a clear reason why he'd tell this specific lie, I'm going to go with 3. If Quirrell doesn't want Harry dead then obviously he'd stop the Centaur, and if he does want Harry dead, he wants to do it on his own terms, with nothing left to chance and no loose ends, so again he'd stop the Centaur.
4linkhyrule5
Or 4) He considered it, and discarded it because of a dark binding ritual.
3drnickbone
Quirrell might have been referring to his initial plan (as Voldemort) to end Harry's life back when Harry was a baby. Quirrell/Voldemort could not have known about a dark ritual then, because he hadn't created it. I still don't think the "dark ritual" hypothesis is very strong, because I can't see why Quirrell would have done it deliberately, so it happened accidentally. It's not clear whether "accidental" dark rituals are even possible in the HPMor universe, but if they are, Quirrell ought to be more careful to avoid them.
3Gurkenglas
We have an outcome pump on our hands that says that Harry is going to tear apart the stars. He can do that for better or worse reasons, and with a better or worse outcome. Quirrel thinks that a Harry that isn't crippled by a centaur (since Quirrel already knows Harry won't die) has a better chance of producing a good outcome than another Harry. Remember that he offered in chapter 95 to read some of his science books and speaking of what comes to mind (...about a month ago. Why isn't Harry omnipotent yet? When I read that Quirrel's suggestion, I thought the rest of the story would have to be squeezed in the time it takes Quirrel to regain sentience.)
2shokwave
It seems plausible that Quirrel read the science books and isn't going to tell Harry anything reality-breaking, since he did a similar thing with the library - after telling Harry that Memory Charms are just filed under M, he says he's going to put some of his own special wards on the restricted section.
2Dentin
It could always be possible that Quirrel's "special wards" happen to let Harry through more easily, or allow Harry to browse the section more covertly, though I'd put odds of that fairly low given his mention of the situation to Minerva.
0Gurkenglas
While I didn't realize Quirrel might be lying about his willingness to cooperate, the Memory books aren't in the restricted section and we haven't heard anything about him sabotaging Harry's attempts at taking over the universe since chapter 95 (except for some sort of deception in 100/101... "what a fiasco" is not something you would hear Quirrel say to himself audibly and honestly). Maybe he was in Zombie mode until 99? We wouldn't know, since we weren't in Harry's POV since 2 days after that chapter, although in his shoes I would have attempted contacting Quirrel as soon as possible.
0Velorien
While both the former and the latter are entirely plausible things for Quirrell to do, it is also worth noting that Quirrell would happily play the Role of a concerned tutor before McGonagall at this time. It would make her trust him more at a time when he may need to use her and other teachers on short notice to fulfil his own objectives, even if he doesn't intend to do anything about the Restricted Session at all.
2Decius
If Quirrell can't solve the problem of future Harry seeing and hearing someone that he thinks looks and sounds like himself, he isn't the dark wizard we deserve.
0[anonymous]
Why everybody believes that centaur wanted to kill Harry ? It rather seems like centaur was disarming him. And it is even possible, he was under imperius curse (from Quirrel) while disarming Harry. He seemed to be surprised about what he was doing (looked up with widened eyes) and he apologised. I believe Quirrel just wanted to interrupt the conversation between Harry and Centaur.
0SyncHole
As a thought, maybe - possibly - Quirrell anticipated the possibility of point 4 (Centaur.) It might be an effective way to make Harry look at his current goals (and their potential repercussions) from another perspective. I wouldn't think the anticipation would be that the encounter was certain, but if it were considered possible...
0buybuydandavis
The final book in Stephen Donaldson's Thomas Covenant Series has a theme of the stars disappearing and the end of the world as well. Anyone read it and sees a tie in? I'm only a few chapters in.
0ChrisHallquist
Wow. So, now it's pretty unambiguous that Harry is going to completely remake the universe somehow. The only question that remains is: does this go well?
0HungryHippo
One way Harry can fulfill the prophesy of tearing apart the very stars in heaven is to somehow send the whole universe back in time far enough to reverse stellar formation. Not sure how to fit the "end of the world" part, though.
8gjm
I suppose it doesn't, strictly, say which end.
[-]iceman460

Premise: Quirrell plays the game one level higher than Harry Potter.

Observation: This entire incident is uncharacteristically sloppy. Why were the unicorn corpses found? Why was Quirrell discovered?

Observation: Harry Potter is now really pissed off that herds of unicorns to slay aren't standard procedure for stable-izing people with life threatening injuries. He has just been given another "if only" to fixate on. It has been brought to his attention in ways that wouldn't trip his "why am I being told this" sense.

Father had told Draco that to fathom a strange plot, one technique was to look at what ended up happening, assume it was the intended result, and ask who benefited.

Hypothesis: Reminding Harry that there were ways the wizarding world could have saved Hermione was the primary effect. Possible secondary effects may include impressing on Harry just how ridiculously powerful he is. Perhaps implanting the desire to save Quirrell into Harry's mind? Quirrell may not actually need the blood right now, though I suspect it doesn't hurt.

5Desrtopa
I don't think knowing that unicorn blood has uses which may not be properly exploited by wizarding society changes his opinion of wizarding society much anyway. It's kind of a straw on a logpile. I think it's more likely that Quirrell's planned reveal to Harry was his impending mortality (which, considering the horcruxes and the spell which can restore him to his original state, is probably not so unavoidable as he implied.)

(which, considering the horcruxes and the spell which can restore him to his original state, is probably not so unavoidable as he implied.)

While he's certainly determined to make Harry believe he's going to die ("this is the last time I will be able to do this for you"), it is likely he is lying for a couple of additional reasons. The man obsessed with not dying, prepared to tear his very soul to shreds to stay alive, has

a) been trying to prevent Harry from seeking a way to bring back the dead, and

b) been doing so purely as part of an effort to save the world - which he has no reason to care about unless he expects to remain in it.

0buybuydandavis
If Quirrell is going through time by using up bodies and moving to new ones, applying a bring "back from death" spell to a former host might force him back to his previous used up body.
3pjeby
I don't think unicorns are actually kept in stables, despite their horse-like anatomy. ;-)
1hairyfigment
Related point that I haven't seen: chapter 100 increased the probability that Harry would bring any clever idea for defeating death straight to the Defense Professor. I like to think that 101 decreased it again, and that Harry might have talked to Draco about those false memories (thereby learning that Quirrell couldn't make guilt feel real). But we'll see.
1ChristianKl
Hermione was dead before she could have killed a unicorn and drank it's blood.
1kilobug
Depends exactly how it works. Is someone dead when the heart is stopped, but can still be restarted ? What happens if someone is forced fed unicorn blood (and the unicorn dies in the process) just after cardiac arrest, but when no damage is done to the brain yet ?
1linkhyrule5
By the time a capable wizard (Dumbledore) was on the scene, Hermione was dead. I doubt there's anything unicorn blood can do that phoenix tears can't, so.

I'd think that unicorn blood has unique properties on phoenix tears.

Otherwise Quirrel would be tracking down Phoenixes and... showing them the first 5 minutes of 'Up' or something.

9TobyBartels
Yes. "Up" was a fairly good movie, but it doesn't hold a candle to the short film that constituted its first 5 or 10 minutes. That should have won an Oscar.
4Gunnar_Zarncke
Here it is
0TobyBartels
I prefer the original audio, but that might be too much to hope to find on YouTube.
4Baughn
I could rewatch Up, except that doing so would require rewatching the first ten minutes. And I can't do that.
0TobyBartels
I know that you're probably not serious but … you can always skip that part. You already remember what happens.
0keen
Doesn't this plan seem rather risky if the primary benefits are so limited? On the other hand, now Quirrell has a way to convince Harry to help him get the Philosopher's Stone, or to consider leaving Hogwarts in spite of the danger to help him with a "life-saving ritual". On the other other hand, telling Harry about these life-saving methods could just make him angry that no one mentioned them with respect to Hermione.
0buybuydandavis
Another effect - Harry's now thinking about the power of unicorn blood to keep people alive.
0ygert
Intresting. I do think that Quirrell needs the blood, but tipping his hand this way did seem to have those effects on Harry, and I would be very surprised if that was unintentional on Quirrell's part.

I know Harry is just a kid, but his reaction towards unicorns don't seem very rational to me. Remember, Harry became vegetarian for a while when he was afraid animals could be sentient. And now, he speaks about massively killing unicorns, magical creatures whose sentient status isn't very clear (like with phoenix), for a "temporary" stop of death at a cost of "permanent side-effects", without inquiring how temporary temporary is, what are those side-effects, and how sentient unicorns are. Without measuring those three parameters, there is no way to know if utility(killing unicorns in St Mungo) is positive or negative.

I think it's less that Harry is a kid right now and more that he's specifically extra-freaked out than usual by perma-death at the time. Plus the Quirrel Distortion Field is keeping him from ever seriously considering anything Quirrel does as really evil.

9Ishaan
Except for its attraction to innocence, there's no particular reason to think that the unicorn is more sentient than a horse, is there? Did I miss something important in the story?
4Desrtopa
I don't think there's any particular evidence in the story which bears on the intelligence of unicorns, save for the fact that some non humanoid magical creatures such as acromantulas are much smarter than their mundane kin. This alone should be sufficient to raise it to the point of being worthy of consideration. Here's another possibility which Harry failed to consider; the side effects of drinking unicorn blood may in fact be worse than death, not for the individual, but for society, if it does something like permanently compromising the recipient's morality. Quirrell is already amoral enough not to care, but if Hermione had been saved with unicorn blood, she might have come out like Demented Harry. It might not be the sort of thing which is obviously likely enough to be worthy of consideration in his position, but the way Dumbledore described in in the original canon, I think suggests it as a distinct possibility.
0Velorien
I would say that "living a cursed half-life" sounds more detrimental to the individual than to wider society. And in general, the limited discourse we hear ("you have slain something innocent to save yourself") sounds more like that of punishment than corruption to me.
2Desrtopa
I always interpreted it as more of a corruption effect; a cursed half-life sounds to me like something where you lack various things that people consider important elements of being alive, perhaps things like taste and touch, perhaps also things like empathy.
0kilobug
So did I, in canon, I imagined unicorn-blood-drinking to be somewhat like horcrux, ripping you of the ability to love, feel empathy, ... and that's what Dumbledore and others consider "half life". It's an hypothesis that is worth probing before just saying "oh let's farm unicorns".
2Velorien
Makes you wonder if anyone has ever tried to research magics that restored someone's empathy etc., or gave it to people born without. Somehow, I doubt it.
0Sheaman3773
It's likely observation bias, but the whole of the wizarding society seems to lack empathy; I join you in doubting that much research on the subject has been done.
4[anonymous]
That's true, but unicorns are immortal, and they have to be killed in order to give a human a few more years of life. Presumably some number of horse-years are worth a human-year; horses aren't quite so negligibly intelligent that the life-value of infinite horse-years converges to zero.
1somervta
perhaps, but the unicorns don't actually have infinite life-spans.
1Alsadius
Well yes, because people keep vamping on them.
2MathiasZaman
I don't think you did and neither was there anything in canon about this. Unicorns are about as sentient as any other magical animal. The taboo of killing unicorns stems from the bad effects it has, rather than the sentience of the creatures.
2kilobug
Well, the point is that "magical animals" have very varrying degrees of sentience - some, like acromantula are fully sentient, some like phoenix are half-sentient, the status of unicorn can't be established without some inquiry.
1kilobug
Well, the magical world is full of sentient or half-sentient things, from house elves to phoenix. The hypothesis that unicorns are half-sentient like a phoenix can't be excluded a priori, it's something a rationalist should inquire before taking any decision. And the scope and nature of side-effects should be inquired. Harry doesn't even do the simplest inquiry, asking Quirrel about it, but jumps to conclusion with incomplete data, doesn't sound like him at all.
9Mestroyer
He does at least know that "temporary" is long enough and the side effects are small enough for Quirrel to consider it worthwhile.
6ygert
He also knows that Quirrell is totally amoral: Quirrell himself admits that he does not comprehend the thing that people call morality. Thus, he knows that Quirrell considering something worthwhile is only evidence about that thing's utility to Quirrell, not its moral validity.
[-]gjm130

mortality

I'm not generally in the habit of calling out typos, but that particular one is probably worth fixing. I think Quirrell understands mortality rather well.

3ygert
True, very true. Edited.
7TobyBartels
He's only brainstorming now, not actually rounding up unicorns or even in a position to do so. That said, I would have expected him to go into more depth about the possible downsides, to be in character.
2buybuydandavis
Harry has dropped the Batman code. Life is full of trade offs. Being alive and sentient trumps side effects and consuming animals, magical or otherwise.
2Desrtopa
Not if those animals themselves are (note that sentience is not really the relevant quality here, that should actually apply to most animals above a certain level of complexity) also sapient. Considering that other magical creatures such as centaurs, goblins and house elves are known to be sapient, and animals not normally considered so, such as snakes, may become so due to magic, the prospect is certainly worth considering.
4knb
It's weird that you're assuming Harry doesn't know that unicorns aren't sentient. You don't know that, but Harry has already researched the known intelligent magical creatures, and he could easily know that unicorns are just magical horses that are pretty. Harry isn't even a vegetarian, of course he would be OK with someone killing unicorns to survive.
0TobyBartels
That's a good point (that Harry might well already know). Then I blame the author for not telling us; this should have come out in an earlier chapter where Harry was reading about unicorns, just so that the readers don't end up distracted from the story by a non-issue.
3knb
There was a chapter in which Harry does research to determine which animals are known to be intelligent. I don't remember if unicorns were specifically mentioned, but I think we should assume Harry already knows they are non-sentient by his lack of concern. (I guess that the new, colder Harry might actually think Quirrell's life is even more valuable than some number of intelligent unicorns--because Quirrell has a lot of extremely valuable knowledge that Harry believes might save many lives some day. But I really don't think this is what Eliezer is going for here.)
0TobyBartels
Can anybody find this for me? I'm not having luck.
4gwern
animal intelligence research site:hpmor.com; first hit: http://hpmor.com/chapter/49 which is not explained in the chapter, so one looks back to http://hpmor.com/chapter/48 and http://hpmor.com/chapter/47 for the full context of Harry freaking out about talking to snakes and being carnivorous.
0TobyBartels
Thanks, I stopped looking too soon!
0Richard_Kennaway
Something else not explained there is the namecheck to Paul Breedlove's "Speak and Spell". I suspect the Lady of Flying Squirrels also means something but I don't know what, although the French version of Speak and Spell was called La Dictée Magique, and one of its modules was Les Animaux Familiers.
1gwern
Just Eliezer throwing in more allusions: https://en.wikipedia.org/wiki/Squirrel_Girl / http://tvtropes.org/pmwiki/pmwiki.php/ComicBook/SquirrelGirl (this was identified in the discussions for those chapters, and Squirrel Girl actually appeared before in the Ultimate Meta Mega Crossover IIRC).
0BlindIdiotPoster
What leads people to even suspect that unicorns are sentient?
4kilobug
1. Sentient is not a binary thing, but a more fuzzy ones. The sentience of apes or newborn for example is hard to quantify in a binary way. 2. Many magical creatures have a higher level of sentience than mere animals. Some are fully sentient like centaurs or acromentulas, some are half sentient like phoenix. Even magical owls or cats tend to be more sentient than their mundane counter-parts. So it really seems from 1. and 2. that the level of sentience of unicorns has to be carefully evaluated, to be able to figure out if the harm done to them would be worth a "temporary cursed" life, it depends of the values of the three parameters : how sentient they are, how "temporary" it is and how "cursed" it is.
0ygert
This is true. However, in his defence, I will say that he has no real idea of whether unicorns are sentient or not, and although it was remiss of him to assume they are not, under the assumption that they are not sentient it is a good plan. Yes, though. It is out of character for Harry, who has in the past done things like become vegetarian when he though that there was the slightest possibility that animals could be sentient. He was still in shock, sure, but the Harry that we know should have known to ask.
[-]Ishaan270

Why did Quirrell allow the unicorn corpses to be found? Why didn't he dispose of the corpse by making it disappear, instead of trying to pass it off as a predator? Would anyone notice if a unicorn vanished without leaving a corpse? ( I suppose they might, since they're medically valuable, but since unicorns are known not to have predators the predated corpse is hardly a good cover, as we saw. Vanishing the corpse would have made it take longer to notice.)

Anyway, this is one of the few times we see Quirrell's plot clearly failing without anyone actually acting to thwart him. Is it plausible that he was actually unable to kill and drink a unicorn without anyone immediately noticing?

6ChristianKl
The alternative is that Quirrell does want people to know that unicorns get attacked. If you want to make a magical reanimation ritual, a species that helps people on the verge of death seems to be a path to go. This whole interaction gave Harry information about unicorns.
4ygert
Hagrid would have noticed. Hagrid named each individual unicorn in the forest, and if one disappeared, he'd definitely go to Dumbledore about it.
9JoshuaZ
Doesn't work. Hagrid says explicitly in the chapter that he's had almost no interaction with the unicorns.
3ygert
He did notice when one died... No interaction does not mean being unaware of their existence (or lack thereof.) Specific proof is that he knew Alicorn was dead before they found the body. He can know that the unicorns live in a place, see the signs of their passing, without actually going up to them and interacting with them.
0xian16
Right? How could he, he's not a young virgin (probably).
2Waffle_Iron
Since school children were being used to investigate the dead unicorn it seems that passing it off as a predator worked fairly well.
2Mestroyer
This bothered me too. To fanwank something, perhaps when near death and desparately in need of unicorn pony blood Quirrell's mental capacity is reduced.
3Ishaan
Ah, that's possible too. I was more implying that since such a mistake is implausible, it must have been intentional on Quirrell's part- for example, perhaps it was a purposefully orchestrated plot to kill Draco. (actually, now that I thought of that, it seems obvious that this is exactly what it was)
3RolfAndreassen
How does he arrange for Draco to go to a Silver Slytherin meeting at exactly the right time to get caught by Filch, and then for Filch to give Draco that precise detention? That's a lot of Imperiuses or other manipulation.
2Ishaan
He did it with hermione, no? He just needs to know about SS meeting beforehand and tip off Filch about it without linking the tip to his ID. Only one hard manipulation here, which is to suggest a specific detention.
0ikrase
And that could probably be done with appropriate False Memory Charm. He's got to have a time turner.
2Mestroyer
If he wanted to kill Draco, why not just AK him without being seen in the middle of the forest, and not reveal that the unicorn-eater is Draco's murderer? Revealing that gives the heroes a place to actually strike back against the student-killer, which is the unicorn population.
2Ishaan
1) Dunno, but I'm guessing it's for the same reason why he didn't just AK Hermione instead of using a troll? We haven't been told the full extent of magic useful for forensics in this story - for example, in canon there is a spell that allows you to check which spells have been recently cast, so if you find an AK'ed corpse it would be fairly simple to check everyone's wands for recently cast AK to narrow down suspects. (Not that there aren't other ways to discreetly kill, but my main point is that we as audience aren't aware of the constraints involved.) 2) Hogwarts ward doesn't operate outside of Hogwarts, and the ward pointed fingers at Quirrell for Hermione's death (presumably he possessed the troll or something). It wouldn't do for that to happen repeatedly - how many times can one use the "framing" defense? Doing it in the forest avoids the wards, the dead unicorns were a pretext for getting Draco out to the forest, and the unicorn killer identity creates a possible extra suspect, Or, are you saying that it allows the heroes to fight back by simply relocating the unicorns? That's true...which means that Quirrell doesn't think he will desperately need additional unicorn blood in the future.
1Desrtopa
An AK'ed corpse in particular should be pretty easy to diagnose; the total lack of any other apparent causes of death should give it away. However, there's nothing in particular to prevent feeding the corpse to any of the various horrible creatures in the Forbidden Forest.
0Mestroyer
Hmm, is the Forbidden Forest within Hogwarts wards? Because I thought the reason he didn't kill Hermione himself was so that Harry wouldn't take it seriously when the wards said that "the defense professor" killed her.
2Ishaan
If the wards do extend to the forest, Tracy can say she saw a dark thing which was not Quirrell kill Draco. If the wards don't extend to the forest, killing him in the forest doesn't alert the wards. The first is a motive against discreet killings, the second is a motive against doing it inside hogwarts.
0alex_zag_al
And if he's going to leave a corpse, he could at least do it silently. Remember that Tracey ran towards the sound of a unicorn being attacked? That's what makes me sure that Quirrell wanted to get caught. There's just no reason for him to skip the silencing spell, otherwise. (Unless he's hiding from someone that can detect the use of magic?) I don't know how he got Tracey to approach, though.

A nausea was in his stomach, a churning sensation that, looking back in memory, seemed both like and unlike a sense of guilt, as though it had the sensations but not quite all of the emotion.

Heh, so Quirrell doesn't know what guilt feels like.

Centaur spears can block many spells, but no one tries to block if they see that the spell is a certain shade of green. For this purpose it is useful to know some green stunning hexes.

This reminds me, if you can make a homing version of the stunning spell, can you make a homing version of the killing curse? Sounds like that would be useful.

The chapter endings for 100 and 101 are a little odd. They stop very abruptly, specially 101. Usually you would get an extra sentence or paragraph to give the chapter a sense of closure.

The reason Quirell and Harry cannot interact magically is supposed to be so Quirrell cannot read harry's mind, memory charm him, confound him, or outright imperio him. But this feels a little weak to me. What's stopping Quirrell from threatening, bribing, tricking, imperiousing, etc... a third party to do it on his behalf?

And if the homing version of "Stupify" is "Stuporfy," how ridiculously twisted would AK get? "Averder Kerderber?"

[-]Shmi330

Abracadabra, surely.

5[anonymous]
At no point does Quirrell say "I just used such a spell on this centaur". I'm not ruling out that he killed the thing, and made an inferius in front of Harry. That would explain the unusually (?) sharp sense of doom that Harry felt when he "revived" it. Also a possibility: memory charming a centaur is a lot harder, since they're only passingly similar to humans, so Quirrel had to draw more heavily on his magic, which in turn resulted in a sharper sense of doom.
4alex_zag_al
Wow, it's amazing how obvious the Inferius seems now that you've said it. I was reading another comment elsewhere on the page which claimed there must be some magical explanation for how Harry's managed to miss that Quirrell=Voldemort. And my first thought was, "yeah, he sat there with his wand on the centaur for a long time instead of just saying 'Innervate' and then 'Obliviate' and Harry still believed him". That actually seemed to me like an extraordinary thing that needed explaining. But, then I remembered: I didn't think of it. I read this chapter days ago, I've been talking about it, theorizing, and *I didn't see it. And now it seems so obvious that I look for a supernatural explanation for why Harry didn't see it? EDIT: As I brought up elsewhere, another reason Quirrell would be drawing heavily on his magic is to read Firenze's mind everything he knows about the future.
0TobyBartels
But you're forgetting that Harry is smarter than you! :-P
6Nornagest
I'm actually not sure how bright Harry's supposed to be. He's not stupid, obviously. But, from a Watsonian perspective, he's leaning very heavily on rationality skills and an unusual reading list for an 11-year-old, Hermione seems to have him beat in some respects as far as raw intelligence goes, and being the smartest person in a class of a hundred and change isn't that great an achievement in the scheme of things. From a Doylist perspective, making Harry get a lot of mileage out of raw intelligence would undermine the message Eliezer's presumably trying to preach.
4Velorien
This doesn't matter very much, though, since we know Quirrell would not hesitate to utter a direct lie if it served his purposes.
1[anonymous]
That's true. Quirrell has played the "mislead without lying" game in the past though, hence I'm not ruling it out.
0avichapman
An increase in the sense of doom? What if Quirrel can possess many bodies at once. He created Voldi to have a villain to fight back in the olden days and then retired Voldi when he got sick of it. He periodically takes over other people's bodies for his own ends, sometimes even when he's not in his 'zombie mode'. Perhaps the variability in the sense of doom is correlated with his extra-body activities. When he takes over the body of a dead centaur, you get an increase in the sense of doom. The fact that he's not in 'zombie mode' at the same time as possessing the centaur might makes things even worse. This would mean of course that Voldimort isn't Quirrel - Quirrel is Voldimort. Quirrel isn't out and out evil the way Voldi is. He simply invented a larger than life character so that he can play the good guy. Being possessed of normal human emotions, his fondness for Harry could be real.
2[anonymous]
I don't think inferii are possessed by their creators. Pretty sure they're just zombies that do the summoners' bidding. I always thought the sense of doom was related to how strongly Quirrel was drawing on his power.
1Viliam_Bur
Whether Voldemort's persona was or wasn't real, the suffering caused by him was real. If I would for some reason decide to pretend that I'm Voldemort, and I would kill many people (shooting them by gun while pretending to cast Avada Kedavra), finding out this all was a disguise would prove that I'm not Voldemort, and that Voldemort's professed beliefs don't have to be my actual beliefs... but I would be a horrible person anyway.
0Vulture
It depends on what your reason for adopting the persona in the first place was.
0Velorien
Then he would rule the world the day he decided to rule the world (which he did at one point, at least extending to magical Britain). A single Quirrell is among the most powerful wizards in the world. A team of Quirrells would have no meaningful opposition, even before he took advantage of the hive-mind benefits of instant coordination and reaction. That would imply that all the words and actions that portray him as a sociopath are an act for Harry's benefit. What would his motivation be in doing this?
2buybuydandavis
The reason for a fact of the HPMOR universe is narrative convenience for the author? Maybe so, but I've been wondering if the in universe reason is that Harry is a time turned Quirrell.
2CAE_Jones
In canon, Harry and Voldemort have a complicated magical relationship due to two separate spells placed on Harry due to the events at Godrick's Hollow. Harry and Quirrell's connection in HPMoR appears to be a simplified version of that.
0buybuydandavis
In canon, was there any reason Harry couldn't cast a spell on Voldemort?
1CAE_Jones
In canon, Harry only ever tried casting spells on Voldemort twice, and both times it was Expeliarmis, and in both cases, Voldemort simultaneously fired Avada Kedavra, and in both cases, wandlore ended it in Harry's favor (in the first case, it was because their wands share a common core, which may or may not be due to their magical link. This one is notable, because it prevented Harry from casting on Voldemort as much as it prevented Voldemort from casting on Harry, but without his wand, Harry was still vulnerable to Voldemort's crucio. This effect was a flashier version of what happened in Azkaban, including a light show and images of the last few people Voldemort killed climbing out of his wand.) Voldemort tried using Luceus's wand in later books to get around the wand problem, but this failed for reasons that did not seem adequately explained (something to do with wand ownership?) I expect Quirrell was using his Alder wand in Azkaban instead of Foldemort's yew, in which case the connection in HPMoR presumably recurses a level. If we use canon as a guide, if Harry touches Quirrell, it will cause them both pain (sense of doom), but to Quirrell it will do physical damage (Lilly's sacrificial protection). I expect there to be less of an imbalance in Harry's favor in HPMoR, but I didn't expect the troll or the unicorns, so my HPMoR predictions aren't so high confidence.
2CronoDAS
He doesn't trust a third party to do this without getting caught?
0BlindIdiotPoster
iirc, that spell wasn't homing, it just turned to the side at the end.
0Velorien
But the side it turned to was the side necessary to hit its original target. Given that spells have some sort of natural AI (like the enchantment on Harry's pouch), and that basic wanded magic is just a matter of triggering a pre-defined effect by saying an incantation while moving in the right way, it seems more likely that the spell was intelligent enough to change direction to hit its target than that Harry pre-programmed it with that specific directional change during casting.
0ikrase
IDK. Moody suggests that the spell might already be mildly homing or at least very easy to target.
2Velorien
In canon at least, the protagonists do nothing but dodge Avada Kedavras in a number of confrontation scenes. It has to be that way, because no Death Eater would be stupid enough to use anything but Avada Kedavra on a target they weren't trying to take alive, and most characters had enough plot armour not to die in a random firefight.
2kilobug
Doesn't AK use more magical energy than a simple stun ? Or just require longer to cast ? "Avada Kedavra" is longer to say than "Stupefy" or "Expelliarmus", at least.
1Velorien
But it is unblockable and precludes the target being revived in the first case or recovering their wand/grabbing someone else's/running away in the latter. In particular, HPMOR makes a very big deal out of any decent wizard being able to put up a dozen different shields, sometimes all but instantly, so unblockable spells are an extremely big deal.
0ikrase
In HPMOR, it also penetrates at least some thickness of cover, according to Moody, who also suggests that it does need significant mana. (How much mana? I'm getting the impression that Stupify is acceptable for Auror-level combat despite being castable by top first-years.) It also cannot be countered. We don't see much of countering in HPMOR, but we do see Susan try to counter an extremely powerful bully's spell in the SPHEW.
[-]gjm200

Nothing specifically to do with these chapters, but it's only just occurred to me: Is it supposed to be significant that the initials of Potter-Evans-Verres are also the start of "Peverell" (indeed, you can get more if you take a few more letters of "Verres")? It seems a rather superficial observation, but "Verres" is a really unusual surname and it would be nice to have an explanation for why Eliezer chose it.

4drethelin
I think there's a good chance Eliezer started writing before he read any of the books that have the name peverell in them?
[-]Dentin160

Peverell -> Potter Evans Verres Quirrel?

Yay pattern matching.

-1somervta
PEVQ? erell = rrel? Doesn't really work.
0TobyBartels
AFAIK, he still hasn't read them, but he should have read ABOUT them before beginning.
2CAE_Jones
Eliezer mentioned in a past discussion where he got the name Verres. Iirc it was a reference to someone/something, though I don't remember who/what. (This falsified my standing hypothesis at the time, which was that EY got the name from Latin for "truth".)
9sketerpot
"Verres" came from combining "Vassar" and "Herreshoff". Here's the thread you're remembering.

This isn't a particularly bad thing, but I must say, chapter 100 was perhaps the most self indulgent this story has had yet.

1somervta
Tto whom is it indulgent? Harry, Eliezer, or the reader?

I would say Eliezer. Introducing another event from the first year of school and subverting it utterly. Blatantly referencing Twilight AND My Little Pony (to the point of bending canon for its inclusion) AND a Methods or Rationality fanwork AND an obscure math program AND Several other cameos sprinkled throughout.

2NancyLebovitz
Does it matter for this discussion that MLP canon unicorns are sentient?

Lets talk about chapter 99.

Chapter 99 was there for a reason. I think the most likely reason is to emphasize the 10 days later. Chapter 98 was April 20, and chapter 100 was May 13. For some reason EY wants the first attack to happen on April 30. This could be because QQ only needs to drink the blood every couple weeks. However, why not just make the first unicorn found on May 12 and have no chapter 99? This would make more sense. I would expect the forest to be searched immediately afterwords. This is empathized further in chapter 100:

Draco nodded; he distantly remembered hearing something along those lines a couple of weeks ago, toward the end of April.

Maybe the goal with this is to give some character a full 2 weeks to research unicorns or make a plan.

Other theories for chapter 99:

He wanted the reveal of the unicorn to fall under the Roles sequence for some reason.

He wanted to build suspense. (But then I would expect him to have posted 99 on Sunday and 100 on Wed.)

He wants chapter 99 to be written in passive voice to hide the identity of the person who "found" the unicorn.

I think that the fact that chapter 99 falls into the 'roles - aftermath' title, indicates it's relatedness. This is the consequence of the roles arc, somehow - perhaps this is Quirrell's response to the new regulations, whyever that might be.

2Scott Garrabrant
I didn't think of that. I think that is more likely than my hypothesis. EY is telling us that the unicorn attack is a consequence of the roles arc.
9Fermatastheorem
Or he's telling us that Quirrell is playing the role of someone who is on the verge of dying.
[-]wwa130

The Severing Charm wouldn't bring down a tree, so he'd started partially Transfiguring cross-sections through the wood.

Quirell saw that. Partial transfiguration is not the power the dark lord knows not.

0mjr
I've pretty much assumed that cat to be out of the bag since the escape from Azkaban. Though he didn't see how Harry penetrated the wall, he could probably reason it out with decent probability. But sure, beside what Sheaman said about PT being already counterindicated, this does clinch it.
0Sheaman3773
http://hpmor.com/chapter/28 http://hpmor.com/chapter/86 Still, good catch.

Reddit discussion of chp 99-101, which includes a few words from the author.

Eliezer: I got the math joke.

Explanation and implementation (spoiler if you haven't spotted the joke yet): http://tinyurl.com/hpmor100mathjoke

(But this only covers the first half of the joke; I had not heard of the second half before!)

[-]Subbak130

If you want to play with a (rather tame, since it doesn't always use its regeneration powers) Bucholz Hydra, here's a link for you: http://www.madore.org/~david/math/hydra.xhtml

For my part, I knew about hydra games and had forgotten the name, but the context made it fairly obvious that this was a joke about the hydra being so hard to kill that you can't prove you do it with only Peano arithmetic.

9loup-vaillant
I have defeated the hydra! (I had to cut off 670 heads). Feels like playing Diablo.
4NoahTheDuke
670? Lucky. I finally bested it after 1750-ish, yesterday. Once I hit 1000, I thought, "Why am I doing this? What am I proving?" and then I started clicking again.
3Vulture
1750? I forced myself to give up and get back to work somewhere around the 6500 mark. (I had decided, somewhere around 1000 or so, to try out the strategy of preferring to cut normal rather than dire heads when possible. Maybe that's a bad idea)
1NoahTheDuke
I worked top-to-bottom, without change. If a new branch grew higher than my previous cuts, I focused it immediately. I know there's an optimal way, but I'm not quite clever enough to think of it.
3Vulture
Well, for this applet the optimal strategy might depend heavily on how exactly its tameness is executed, which isn't very enlightening. Edit: Derp, I tried out top-to-bottom and got it in 572. Definitely better than left-to-right or normals-first-ltr.
0Fermatastheorem
I used top-to-bottom, but dires first on each level, and that seemed to work consistently pretty well.
3ygert
I got it too, and I think Eliezer was vastly under confident in his estimate of the number of people who would get it: We have a very mathy community around here. In any case, I am glad Eliezer ended up including it. HPMOR is good enough to make me actually laugh out loud at least once every chapter, and the bit about the hydras was chapter 100's contribution.
4[anonymous]
Chapter 99?
0ygert
OK, fine. But that wasn't a real chapter.
3TheTerribleTrivium
Chapter 99 made me laugh, just because I read the author notes beforehand due to how they updated in my RSS reader and was fearing something as mental as worm 27b
3lmm
I found it jarring. Either the characters were making jokes at a very uncharacteristic time, or just saying things that make no sense; either way this derails them. It seems to be a general problem in fanfic.
0ygert
How come? They were not saying things that make no sense, if that is how hydras operate in that world...
-1TobyBartels
That (the mathematical hydras related to ordinal arithmetic) can't possibly be how hydras operate in that world. Wizards don't know ordinal arithmetic, they only go on experience, and experience would tell them that a hydra with more than a few heads is impossible to kill. The mathematical existence of success is irrelevant when it takes longer than the age of the universe.
4ygert
These are wizards. They can do, if not quite everything, a lot that we consider impossible or insanely hard. Maybe hydras have the magic property that they "stop time" nearby. For anyone near a hydra, time seems to freeze, at least until the hydra is dead. So if they can kill the hydra, the world pops back to normal with not a second past since the hyda attacked, but if not, they just get eaten. This is a powerful attack/defense mechanism for the hydra, as the hydra's opponent must spend eon upon eon fighting it to win, and almost all give up before then. At least, that is how I imagine Eliezer would write it if that kind of hydras appeared in canon and Eliezer had to come up with a reasonable explanation to it. Many things "don't make sense". How can dragons fly? They are to big to reasonably do so. But an intelligent author can "fix" things, and give a reasonable explanation. Eliezer did that a lot to certain things from canon, and such is the correct attitude for facing a fictional thing you deem "impossible".
0TobyBartels
In that case, fighting hydras is something that any decently curious Wizard should attempt as a matter of course. Even if you're spending most of your effort watching the hydra, it still gives you a long time to think. No way (unless that's part of the hydra's spell) that you're coming out of that experience the same person!
3Desrtopa
Well over periods of time that long, you might come out of it a new person who differs from the old one by being bugfuck crazy.
0itaibn0
Well, none of the commenters explicitly mentioned the relevance of 'second order' and 'comprehend', and some gave indications they didn't notice those hidden puns. Personally, I read the author's note before the chapters themselves so I knew it was coming, but I believe I would have noticed it anyways. However, I didn't recognize the name Paris until after looking it up.
4ygert
I mentioned that I laughed aloud at the hydra joke. the actual specific point which I laughed out loud at though, was the "second order, iterate" part. It was just so... appropriate, if out of context and only that way due to the speaker's accent.
0somervta
OK, I got those puns, but didn't get the hydra reference (I'd never heard of them), and I spent some time trying to figure out what they were related to.
0Adele_L
I got about 80% of the joke - I pattern-matched the description to being something like Tbbqfgrva'f gurberz, but I didn't recognize the names Paris or Buchholz.

You had to try to live the other person's entire life inside your own head, at least if you wanted to create the False Memories with less than a sixteen-to-one slowdown as you separately crafted sixteen major tracks of memory

Was this by any change a reference to Permutation City? That was 17× slowdown, but that could be explained by taking the ratio of real+simulated time. But I do not get the "sixteen major tracks of memory" then.

Far fetched, I know...

0Gurkenglas
Nah, Permutation City specifically said that slowdown was due to the best known designs for brain emulations on current hardware, and to be made less severe in due time.

It seems the entire race of centaurs have taken something of a hit - in the books, they were perfectly aware that their divination was based on one's state of mind and could easily be applied to the patterns perceived in, for example, twisting smoke from a campfire.

I wouldn't mind much - Eliezer may not even have known or remembered that - except that this is not a new lesson for the readers, and it seems a missed opportunity to talk about pattern-matching, maybe tie it in with some of the other stuff about subconscious knowledge or desires in that scene.

I'm torn between vaguely hoping Eliezer will decide to change this, and uncertainty as to whether he even reads these comments. Heck, why should he? I certainly can't write anything like HPMOR, why would he expect to get a useful suggestion from such a comment? (And it doesn't help I'm signalling incompetence with typos from this darn phone, props to TobyBartels and others for reminding me to fix them.)

[-]gjm21