Harry Potter and the Methods of Rationality discussion thread, part 12

General announcement:

I do not lie to my readers.

Almost everything in MoR is generated by the underlying facts of the story. Sometimes it is generated by humor (I can't realistically claim that Ch. 5 would have comic timing that precise in a purely natural universe). Nothing is generated to deliberately fool the readers.

There are two exceptions to this claim I can readily recall - cases where red herrings made it into the text - and they occur in Ch. 21 where my phrasing of Dumbledore's note to Harry was influenced to be overly compatible with the fan theory (which took me quite by surprise) that the notes were sent by Sirius Black. And in Ch. 77 when Mr. Hat and Cloak says "Time -", which was generated to be compatible with the postulate of a Peggy Sue. I may go back and eliminate both of these at some point to make the text herring-free.

Methods of Rationality is a rationalist story. Your job is to outwit the universe, not the author. There are also cases where people have scored additional points by successful literary analysis, e.g. Checkov's Gun principles. But the author is not your enemy here, and the facts aren't lies.

Of course there are various characters running deceptions and masquerades, but that is quite a different matter.

Hypothesis:

Quirrellmort intends to upload his mind into Harry's body soon, as soon as Harry is Dark enough. Voldemort will become the Boy-Who-Lived. And Quirrellmort wants or needs this to happen within the next few months.

Evidence:

If Quirrellmort were only after the Philosopher's Stone and training Harry for a long career, he'd keep his own cover intact as long as he could. Instead, over the last few story months, Quirrellmort has cheerfully all but ruined his cover in favor of giving Harry chances to turn Dark.

• Quirrellmort got the Dementor brought to Hogwarts, waited until the last moment to observe Harry's wand by the Dementor's cage, gave wrong advice about how to help Harry recover from the Dementor-induced personality change, and persuaded the other wizards to let Harry face the Dementor again.
• Quirrellmort took Harry to Azkaban soon after seeing Patronus 2.0, leading to more Dementor contact and the recovery of Bellatrix, Quirrellmort's preferred assistant for critical tasks (like, say, ritual magic to download yourself into your Horcrux's body).
• Quirrellmort (as H&C) set up Hermione for Draco's attempted murder, thus both cutting off Harry from the person who's his best influence against being Dark, and motivating Harry to embrace his Dark side more in order to rescue or avenge Hermione.

The first stunt made Dumbledore suspect a plot, the second showed that Voldemort had returned, the third that Voldemort was in Hogwarts. But it's all been worth it to Quirrellmort to hurry up Dark!Harry. Why?

Perhaps because Quirrellmort is running out of time in his current body.

• On the day he killed Rita Skeeter, she observed Quirrellmort had his hair falling out.
• Harry has noticed Quirrell looking visibly older.
• The curse on the Defense against the Dark Arts position demands a terrible conclusion to his year - or at least the appearance of one.

And if Quirrellmort doesn't intend to be around as Quirrell much longer, what does he intend? We have clues.

• We know from the prophecy that Quirrellmort and Harry can destroy each other's spirits.
• Quirrellmort has said that Harry's sense of doom between them is precisely of Harry's doom.
• We suspect from canon combined with "Dark Harry" moments that Harry is an accidental Horcrux containing a partial copy of Voldemort's mental circuitry, and possibly some of his power too.
• Quirrellmort suggested a plan where Harry would be seen to fight the returned Voldemort and defeat him.

The obvious answer is that Quirrellmort intends just the plan he told Harry: Harry will indeed be seen to fight Voldemort and "defeat" him. And "Quirrell" will die, probably having been revealed to be Voldemort. But Quirrellmort... will have downloaded himself into Harry's mind, and so will win the duel he seems to lose.

Just as before, a single clash of spells between Voldemort and Harry Potter will lead to the destruction of "Voldemort"(Quirrell.) And "Harry" will walk away triumphant. But "Harry" won't be Harry any more.

If Quirrellmort's plan succeeds, Harry as we know him will cease to exist. Voldemort will go on in triumph -- as Harry Potter, the boy who destroyed Voldemort twice over. Harry will be the beloved hero of magical Britain -- and Voldemort inside.

I suggest Quirrellmort's top priority is to turn Harry fully Dark before the end of the year, so he can safely download into Harry.

Not HPMOR talk, just a suggestion for these discussion threads:

I think that it would make far more sense to start a new thread after every new update rather than when they reach a certain number of comments. New people starting in this thread will miss a lot of good ideas posted in the last one, and also that it is better to have all ideas in one thread than scattered so we can refer to them. Having two threads without any new update in between could also create unnecessary rehashing of old posts.

Since the update schedule seems to be spaced about a week apart, there will probably be about 500-1500 comments in the meantime so there is little chance of having to create new threads too early. In the rare case, a minimum number of comments can be assigned if updating is too frequent.

Dumbledore's trickeries: just how much is he covering up?

We know, now, from the "Santa Claus" stunts, that Dumbledore is quite capable of trickery. Reading between the lines, it appears he cruelly sabotaged Snape and Lily's teenaged relationship.

What other deceptions belong to Dumbledore? Several are possible.

• the prophecy and Snape
• Rita Skeeter's False Memory Charm
• Amelia Bones burning Narcissa Malfoy
• Lily's final Dark-ritual conversation with Voldemort

The prophecy and Snape:

The "confessor" interlude makes it clear that Snape was present for Sybil's prophecy. Does that mean that Harry is wrong to theorize that Dumbledore arranged for Snape to hear it...

... or did Dumbledore use a Time-Turner to make sure Snape heard the prophecy live and in person, so that Snape would be baited more credibly into telling Voldemort?

Rita Skeeter's False Memory Charm:

Dumbledore rewards the Weasleys for the prank, which happened to benefit Harry Potter and deprive Lucius Malfoy of a tool. Is it possible that he not only rewarded them for it, but committed the active part of it himself?

Amelia Bones burning Narcissa Malfoy:

There's suggestive evidence within the text ("Someone would burn for this") that Amelia Bones is hard-bitten and fire-minded. We also see her specifically pulling back Dumbledore from confessing to Narcissa's murder. Is it possible that Bones performed the murder, and afterward Dumbledore pretended to Lucius that he had been Narcissa's killer?

Lily's final Dark-ritual conversation with Voldemort:

Lily's last conversation with Voldemort just so happens to replicate the requirements of a Dark ritual - you name the thing sacrificed, and then the thing to be gained.

"I accept the bargain. Yourself to die, and the child to live."

Did Dumbledore prompt Lily on what to say if confronted by Voldemort, to trigger the accidental Horcruxing that saved Harry?

How much of this is Dumbledore actually guilty of? Do we know or suspect other trickeries, or have other evidence?

Let's discuss Dementors. I was surprised to learn that a lot of people came away from TSPE believing in Harry's initial hypothesis, that Dementors had no minds of their own and were controlled by the expectations of the people nearest them. To me, this seemed conclusively disproved by something Harry isn't aware of: the fact that the dozen Dementors he scared away went back to their hundred-plus brethren in the central pit and thereafter all of them refused to tell the Aurors where Harry was, despite the fact that there were quite a lot of Aurors believing very strongly that they would.

If there's something I'm missing that rescues this hypothesis, I'd appreciate it being pointed out. At this point, I have to believe that whatever ritual (or possibly "law of magic", if we believe Harry) creates Dementors also imbues them with at least some independent decision-making ability, and that they have goals which include 'continuing to exist'.

Why is HPMOR's Quirrellmort so much less violent than HPMOR's Voldemort?

HPMOR paints a Voldemort fixated on punishing his inferiors, a Voldemort who never used persuasion or inspiration when he could rely on suffering.

• Voldemort amused himself by inducing in Bellatrix a love so knowingly one-sided that it was not a happy thought for her.
• Quirrell asserts Voldemort slaughtered an entire monastery rather than simply impersonate an appropriate student.
• Voldemort's rule was so coercive and terrorizing that Lucius Malfoy finds it best to claim he was not merely deceived or misled but forced to obey him.
• If Harry's "dark" thoughts under the Dementor's influence represent Voldemort's mind accurately, Voldemort's reflex inclination was to punish or kill anyone who didn't slavishly obey.

Yet Quirrellmort, for all that he talks cynically and is prepared to kill or memory-charm, prefers not to punish when he can benignly persuade or inspire.

• Quirrell is verbally much less insulting than an army drill sergeant, let alone how Snape treated students.
• The "Quirrell point" system is all about achieving rewards, not avoiding punishments.
• Quirrell's entire plan revolves around patient impersonation and feigned subordination - the kind of behavior that the old Voldemort allegedly refused at the monastery.
• Quirrell is explicitly disapproving about the old Voldemort's approach to persuasion.
• We've been in Quirrell's head when Harry and Dumbledore weren't around, yet his violent acts have always been to "eliminate my enemy", not to "instill fear of me in my intended lackey." The author's had 70+ chapters to show Quirrell or even H+C tormenting a hireling of his with no one else around, and neither has done so.

In HPMOR, Voldemort was grandiose, cynical, and punitive. Quirrellmort is grandiose, cynical, but not punitive. We see him kill to remove danger, but we don't see him torment to instill subordinates' fear of him. Why the change? Options:

• 1: Maybe Quirrellmort is still as punishment-oriented as old Voldemort, but the author doesn't want to show us that ugly side of him quite yet. But if Quirrell doesn't deserve our sympathy, isn't it a good idea to make us lose it? Or if the author wants to hold off on admitting Quirrell is Voldemort until the last moment, why not have H+C be the punisher instead of Quirrell?
• 2: Maybe Voldemort had bad publicity; he was ruthless with enemies, but it's only propaganda that he abused his own people. But Bella and Dementor!Harry are both private evidence that Voldemort was abusive.
• 3: Maybe Quirrellmort has realized the practical downsides of being punitive with those under your authority, and no longer uses those tactics. But if he could figure he was wrong about such a huge part of his leadership style, why is he so deaf to all the other ways he could be wrong about what to expect from people? Where did that open-mindedness go?
• 4: Maybe Quirrellmort doesn't have Voldemort's abusive impulses, because Horcrux!Harry is holding onto them. But why would Quirrellmort not believe in terrifying his subordinates anymore, when he still believes that nobody has any reliable kindness or loyalty? It's cynicism as much as anger that inspires rule-by-fear, and Quirrellmort has full cynicism.

Of those four, my bet is on Horcrux!Harry, but even that doesn't quite make sense to me. Why'd you change, Quirrellmort?

I thought you all might find this amusing: I just got a friend to read HPMoR, and now he's planning on using parts of it to teach his Intro to Psych course.

I think he's planning to use Ch 8 (Hermione's Comed-Tea test) and the chapter(s) with Draco and Harry doing the Blood Purity experiment.

I don't remember MY Intro to Psych course being anywhere NEAR that interesting...

1. Dumbledore believes that Voldemort is at large.
2. And that he's probably responsible for Hermione's troubles.
3. And that he can possess people.
4. And that Quirrell is under heavy suspicion, both as a Defense Professor and directly in this case.
5. And Dumbledore still looks for Tom Riddle elsewhere.
6. And he doesn't hold the Idiot Ball (because no one in this fic does).

I notice I am confused.

I just penned a few thoughts on maintaining proper pessimism about Methods's future. (I also teased Eliezer and, indirectly, Less Wrong commenters a bit. It's all tongue-in-cheek and in a spirit of friendship.)

If anyone can think of a better title for that post, do let me know. I couldn't come up with a pithy Rationalist phrase that quite fit it.

Only tangentially HPMoR related (HPMoR hammers on the #5 point, will hopefully delve deeply into the #6, and touches on the others), but this Cracked article was an interesting perspective:

In retrospect, our guesswork was a lot messier than it should have been.

Chapter 25:

One set of problem-solving groups had been given the instruction "Do not propose solutions until the problem has been discussed as thoroughly as possible without suggesting any."

The other set of problem-solving groups had been given no instructions. And those people had done the natural thing, and reacted to the presence of a problem by proposing solutions. And people had gotten attached to those solutions, and started fighting about them, and arguing about the relative importance of freedom versus efficiency and so on.

and

Starting out by looking for solutions was taking things entirely out of order. Like starting a meal with dessert, only bad.

While Less Wrong discussants are usually prone to less fighting and arguing than the norm, they are not prone to being inefficient.

What we should have done was forbade any and all solutions until two days after the chapter was released. We had five full days to guess, we didn't need to have all our solutions down the first twenty-four hours. Not to mention that instead of simpler solutions, we continued to look for answers more complex than the ones already proposed after we thought we already cleared the low-hanging fruit.

While some people have made an attempt to analyze first, listing everything in the room, things that only Harry knows, et cetera, the majority of us just proposed solutions right away. This was probably not what Mr. Yudkowsky wanted.

Word of God:

One thing I did notice was that many readers (a) neglected simple solutions in favor of complex ones, (b) neglected obvious solutions in favor of nonobvious ones, and (c) suggested that the correct hints had been put there for deliberately deceptive purposes.

...which in my mind I parsed as keep it simple, stupid, and you all were looking in the wrong direction and why the hell are you all proposing one preposterous idea after another, are you trying to look intelligent or something.

My only conclusion after reading that was that if we drew a map first we probably would of found the more probable solutions a lot quicker. Also reading through 1.5k+ comments full of solutions was headache-inducing.

Apologies if this was in the earlier thread; I didn't see it.

Some facts: When Quirrell is being interrogated, he "sneezes" to cancel the spell "polyfluis reverso", which would show who, if anyone, had polyjuiced into Quirrell. Canon has it being posession, not polyjuice. Also, he suggests that someone is possessing Quirrell in a way that makes it unlikely to be believed.

Some speculation: Quirrell wants the auror to think that he's somebody else polyjuiced as Quirrell, and is willing to reveal that he is capable of powerful wandless magic to do so. He also at least partly reveals that when he messes with the room's lighting earlier. Why does Quirrell not try to hide this ability better when he knows the strategic value of hidden abilities and, IIRC, only a few wizards (Voldemort among them) are known to be capable of wandless magic?

Somewhere in the last thread's 1000 posts, it occured to me that it might be useful to have a list of non-obvious insights aggregated. This is stuff that may be missed if the reader has read only HPMoR but is unfamiliar with canon, or it may be things that are well hidden in plain sight. I know it's not normal practice to rot13 such things, but the sheer density of them makes it seem prudent.

• Dhveery vf Ibyqrzbeg.

• Yhpvhf guvaxf Uneel vf Ibyqrzbeg.

• Dhveery znqr gur Iblntre 2 cebor n Ubepehk.

• Uneel nppvqragnyyl thrffrq gur ybpngvbaf bs Dhveery'f Ubepehkrf.

• Dhveery xvyyrq Evgn Fxrrgre.

• Qhzoyrqber urycrq Yvyl znxr Crghavn'f ornhgl cbgvba.

• Dhveery unf gur Erfheerpgvba Fgbar Qrnguyl Unyybj.

I know there's a bunch I'm missing so feel free to add. Ideally, they should not be controversial, just easily missed.

First - YAY! I really do love this book.

Second, the link to part 13 isn't working.

Third, are we going to get a George Bailey scene of people helping to pay off the debt? He did only save them all from the Dark Lord. I know it's not quite as important as helping people to get mortgages, but it should count for something. If nothing else, there's got to be enough people with money out there who wouldn't want the Boy Who Lived to be in debt to the leader of the Death Eaters just as a political matter. And after his show of power against the Dementor, there should be a few people who would consider doing him a favor an extremely wise investment.

Maybe this is the wrong place to ask, but are there any other cool pieces of "edufiction" like HPMoR? I mean fiction where you can learn about science, economics or other topics just by reading the story, and thinking along with it.

There is lots of historic fiction material, so I'd like to exclude that genre from my question.

I am now convinced (>51%) that Harry is going to sell out Quirrell to buy Hermione's freedom. I originally came to this hypothesis because it is a solid plan; Harry frames Professor Quirrell using his knowledge of Azkaban to free Hermione. He can do this by framing Quirrell as Voldemort, but each conjunction makes a probability less likely so I'll stick with just the above (even though I personally believe this will be the case). With the Watsonian parts hammered down, I'm awestruck by the elegance of the Doylist reasons.

Instead of looking at fiction as a series of words, we can instead look at it as a way to maximize tension, humor, and dramatic irony while keeping believability as strong as possible. Believability is important. Many other stories have their characters act stupid or out of character to create dramatic moments. At the eleventh hour a (badfanfic!)Harry decides to run off instead of get his friends, or randomly (badfanfic!)Hermione decides to side with Lucius for no goddamn reason. In HPMoR's case, we will have everyone working in their own rational self interest, intelligently, and coming out with a result that flows seamlessly to create maximal drama.

Harry falsely (accidentally truthfully) rats out Quirrell to save Hermione. From Harry's point of view he'll be forced to attack a (guilty but he thinks) innocent man who's done nothing but help him. Harry knows that Quirrell offered to fake a Voldemort fight for him (partially easing Harry's guilt), but now he's doing it without his consent. +1 irony for using Quirrell's own plan against him.

From Lucius' point of view he'll have (Harry!)Voldemort lying about the existence of Voldemort to his face. Lucius will inadvertently help Harry by preventing legillimency being done on Harry because Lucius thinks Harry is Voldemort and Voldemort is an occlumens. Even while we and Harry know he's not Voldemort, Lucius will not. And Harry will think that Lucius will be helping Harry because he wants to back out of taking revenge while saving face in front of the Wizengamot. Meanwhile Lucius will merely want to prevent the higher standard of evidence from being admitted and realize he's been outmaneuvered by (who he thinks is) the Dark Lord.

From Quirrell's point of view he'll have enacted a perfect plan to break Harry's 'side of goodness' while having Lucius destroy Dumbledore for him... only to be foiled by that fool boy messing up the plan again. Just like in Azkaban he'll underestimate Harry's need to save others, but in this case it'll take the form of betraying Quirrell. Since Harry is the only person Quirrell has ever liked (or possibly even loved), he can take this opportunity to turn even more evil and declare Harry his mortal enemy etc. It's possible he's even already laid the groundwork to break Hermione out (ex imperius the auror transferring her), but did not think for Harry to fail two of his lessons at once (be willing to lose / avada kedavra lesson in azkaban).

The story will get to use the investments from TSPE, Occlumency training, and Lucius' belief in Harrymort. I'm actually kind of in awe of this. Each one of those flowed naturally to create a believable world and fascinating reading in themselves. But that they can be recycled with such efficiency is amazing. Hopefully it's not just hindsight bias, but I'm seeing threads all the way back 50 chapters woven together. It makes me view Eliezer with a kind of formidableness in storytelling, like the ET Jaynes of fanfiction.

From a narrative point of view, the Voldemort reveal to the world has to occur soon. Voldemort needs to become an adversary to Harry before the final act, and it would require an entire build-up cycle again to make that happen. The Voldemort reveal (to harry) has to occur eventually as well and this preserves it until the very end for maximal drama.

So, in universe it makes sense. Out of universe it creates a beautiful story. I suspect it's too clever a resolution for Eliezer not to write. If I am correct in my guess, remember that Eliezer is a writer maximizing good storytelling and drama, not a writing trying to trick his audience. Plus, no one reading the chapters as a completed book would have ever figured it out, even as the parts flowed seamlessly together.

And if I'm incorrect in my guess.... well I guess I get a great lesson in humility and calibrating confidence.

Whatever the hell happens, it has to end with a snap.

Short detour back to chapter 79, to look closely at the night's events:

At midnight, Draco and Hermine meet for the duel. (Let's assume they did have a duel, because implanting very believable (but still false) memories into both of their brains would take about twice the time of the duel and would thus be unnecessary work.) Let's assume that the duell takes about 15 to 20 minutes, so it's now 12:20am. Enter Mister X. Mister X stuns Draco, implants false memories (< 1 min) into Hermione's brain of her doing the Blood-Cooling Charm, and finally performs the Blood-Cooling Charm on Draco in a way to make sure he survives for >6 hours. Mister X is back in his room at 12:30am and needs to wait 6 hours (plus epsilon) until all traces leading to him have vanished.

And guess what:

At 6:33am, Quirinus Quirrell had Flooed St. Mungo's from his office for immediate pickup of Draco Malfoy.

Some Bayesian updating on P(Quirrell did it | Quirrell found Draco at 6:33am) tells us that this increases the probability of "Quirrell did it" by a quite noticeable amount.

OTOH, I'm not sure whether it would be okay to just do the math, without taking into account the possibility that Eliezer chose that time deliberately to steer us in a certain direction. Any thoughts on that?

This seems like brinksmanship. My instinct tells me Dumbledore was right and anything Harry does is weakening the ultimate compromise that everyone who matters knows will be reached (most likely behind closed doors.)

We're given at least two hints about this during the trial, though I did not read too closely.

Where do prophecies come from?

• The idea of Time itself designating some people and events as Important and composing vague poetry about them is incompatible with a universe that runs on simple physical laws and is obviously nonsense. Doubly so if those laws are actually timeless. I hope I can state this unequivocally.

• If Eliezer wants to teach his readers that a hero can be anyone with the talent, courage, and conscientiousness to do what's right, that there are no auras of destiny, that heroes choose themselves, then he can't actually have the planet's operating system, the Source of Magic, amputating the characters' destinies by choosing which ones to promote to Power User status. Even if it has a naturalistic explanation, a story whose heroes are ordained by fate would teach the same lessons as Star Wars. While David Brin is reading it. And Eliezer wouldn't do that, right?

Dunno.

• Depending on where you draw the line, anywhere from four to six false prophets have now appeared in the story. I assumed they were there to prime you - really, beat you over the head - with the idea that prophecies can be human fabrications. But perhaps Eliezer just likes to repeat himself.

• Similarly, the repetition of Grindelwald's name should be priming us to accept his subsequent appearance in the story and not find it arbitrary or contrived. Chapter 42 is utterly pointless except as foreshadowing of his motivation for returning. If Trelawney's prophecies have a human author, it should be someone who can play at the same level as Dumbledore and Voldemort, but not be one of the prophecies' dupes. Grindelwald is the only available candidate. It fits the rhythm of the story, which is pounded out with falling anvils: Harry being forced to fight Voldemort and Grindelwald at the same time is the sort of escalation of challenge he faces routinely. It's a reasonable guess.

But there's nothing connecting Grindelwald to prophecy. And I was wrong the last time I guessed at his role in the story, trying to shoehorn him into Voldemort's superfluous second secret identity, Mr Hat and Cloak. So I don't know. Where do prophecies come from?

Isn't it about time Harry taught Hermione Patronus 2.0?

Sticking my neck out with a prediction, at the eleventh hour: I think that 1) the most likely solution of any proposed is that Harry will call in the debts owed to him by some of the Wizengamot members, 2) the true culprit behind the duel, GHD attack, and possible other mind-magic will eventually be revealed but not necessarily in this chapter, and that 3) it's probably Quirrel. Note that this shouldn't be taken as one giant conjunction, just three independent predictions.

And that is how you do a Mood Whiplash right. I was incredibly nervous going into the chapter, and laughing the moment I saw the word "marriage."

Also, I think that Harry actually managed to make a slightly conciliatory argument at the end there. Namely, "If you don't piss me off any more, I can be a really, really powerful ally. And I'm in debt to you."

Looks like the LessWrong readership called it. Both plans, even. Congratulations, people who guessed quicker than I did.

I notice that Harry's view of the Wizengamot as a faceless entity doesn't actually seem to have changed this chapter. So much for that hint.

Also, it would be nice to know which members of the Wizengamot now think Harry is Voldemort and why they think he decided to pretend to die or whatever they think happened.

Has anyone suggested Harry simply giving a long impassioned plea, thus acting as Hermione's missing lawyer? He might be able to sway enough of the voters if he proposes a satisfactory lesser punishment (and passes a rhetoric and/or sophistry skill check). Hagrid was convicted of murder in Hogwarts, and his punishment was having his wand snapped and being expelled.

Can we add a link in the article heading to discussion section eleven?

My exhaustive analysis of Chapter 81

As we know, Harry's idea of double memory-charm has not been presented to the Wizengamot, which is a good thing; not only is it low status, as Harry realized, it's also unlikely to work, as Snape pointed out. Also, that's not what happened.

Hermione has been told the right lie, to lead her through the right emotions - a growing suspicion towards Draco, mainly - and then she was Obliviated, and told the same lie over again, went through the same emotions again, and again. If the sense of disorientation isn't a problem, she could have been looped through just the final, triggering sentence. Comulative effects had left her with the reoccuring thoughts and nagging doubts, the obsession we were told about. Even the idea of confronting Draco at the next battle, or keeping her doubts to herself could have been planted this way.

Hopefully it will be seen as a typical Voldemort-like cleverness by enough of the Wizengamot for the rest to work. In fact, redirecting Lucius's anger towards the real perpetrator should be doable, and most of his faction (politics!) would be eager to accept Harry's suggestion that Dumbledore was foolish enough to let an agent of the Dark Lord teach at Hogwarts - I doubt it would be a good idea to reveal the truth too early.

Quirrell, who, I think, is still held within the Ministry, will be brought for questioning, and revealed to be Voldemort. Whether it will be his power or the Bystander Effect (the title of the next trigger warning page) that holds the Wizengamot back long enough, I don't know. Actually, a single threat could make most of them hesitate long enough... Than, just as planned, he tries to kill Harry, explodes, then it's cheers and Butterbeers all 'round.

Harry will choose to cooperate with this plan because he will see it's aim wasn't to kill his friends - Draco could have been left for dead, and wasn't - and because he doesn't have five days to think of anything else.

It would be a serious change in the story and, with Quirrell gone, he couldn't fulfill his promise of both Slytherin and Ravenclaw winning the House Cup - but these things would not motivate Voldemort to pass on this opportunity, I think.

It's annoying that the whole fic has been hanging by a thin thread for awhile now for no good reason. When Dumbledore, McGonagall, Snape or anyone else finally tells Harry about horcruxes, Harry will figure out in seconds that Quirrell is Voldemort and that Harry himself is a horcrux. (Quirrell told Harry about the Pioneer plaque, and later asked him about secure ways to lose a thing. Harry remembered Voldemort casting the horcrux spell, but filed it away as a "strange word" in Ch.45. Harry's being a horcrux explains his dark side and his sense of doom near Quirrell. Etc.)

Between chapter 80 and 81, here's my analysis. I can think of seven broad possibilities;

1.) Do nothing
2.) Attack publicly
2b.) Attack publicly in disguise
3.) Stealth attack
4.) Retreat and regroup
5.) Change the board
6.) Deus Ex Machina

1.) Do nothing; I list this simply because people often forget that inaction may be the best possible action. Here, that doesn't seem to be the case. On the other hand, once you realize that sacrifice is necessary, why not give in to the dark side? What's one muggleborn more or less? With proper obliviation Harry can literally forget about Hermione. Plus, the dark side has tasty Hufflepuffs. And cookies.

2.) Attack publicly.
While romantic, this puts Harry into a massive, wasteful, battle with basically all of wizarding Britton.
He's good, but realistically, he'd lose.
Blackmailing the council publicly seems equally pointless. Even if they gave in, it would be disastrous in the long run. On the plus side, this is by far the most dramatic possibility. It's not hard to imagine Harry laying waste to the Dementors essentially freeing all the prisoners, and throwing the wizarding world into complete and utter chaos.

2b.) Attack publicly in disguise. Basically, put on a mask and break Hermione out of custody. Again, several possible ways to do it, but all with the significant drawback of making Hermione a wanted fugitive.

3.) Stealth attack. Harry and Quirrell almost succeeded in getting Bellatrix out without any help and without anyone knowing. With the order and the aurors attempting it, it wouldn't be unimaginable that they could remove Hermione without anyone finding out. On the minus side, Hermione would have to become a non-entity for 10 years, and they'd have to sneak her back in. On the plus side, the comedic potential is enormous. Almost every major character could reasonably have a motive to sneak Hermione out, even the evil ones. Massive Gambit Pileup ensues.

4.) Retreat and regroup The bad part of this is Hemione will be in Azkaban for some amount of time. The good part is that it doesn't result in Harry being at war with magical Britton before he's ready. This probably isn't as bad as it first seems. Many will be outraged by the decision to send a 12 year old girl to Azkaban, including, I bet, Draco Malfoy. Now that the court room acting is over, "Draco" can argue for leniency, and Lucious can soften his heart over the plight of so young a girl who was clearly unaware of the severity of her crime, and blah blah blah. Lucious wants Hermione away from his son, discredited, and wants to stir up the blood purists. All that is accomplished if Hermione is locked up in, say, Nurmengard, and his son vows to stay away from her. Add in a bad publicity campaign smearing the wizingamot "Malfoy says 12 year old girls should be tortured in Azkaban". Harry might even be allowed to visit and banish a few dementors, rather than having to do it clandestinely

5.) Change the board. Determine who really cast the blood chilling charm. Find out who killed Narcissa Malfoy, and give them up. Or the dark path - find someone and give them up as Dracro's assailant/Narcissa's killer, without considering their actual guilt. (Harry could put his minion Lesath Lestrange to good use.) Find something else that Malfoy wants, like say, the philosopher's stone, and give it to him. Become god. All good things to work on, but their timing is not under control, which means this really is a variation of one of the other options with extra work added.

6.) Deus Ex Machina. The author could make anything happen. While it might be that only the author can save them now, it's not something I'd expect the characters to plan for. And I for one would feel cheated if that was the final solution.