(The HPMOR discussion thread after this one is here.)

This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. There haven't been any chapters recently, but it looks like there are a bunch in the pipeline and the old thread is nearing 700 comments. The latest chapter as of 7th March 2012 is Ch. 77.

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.


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: one, two, three, four, five, six, seven, eight, nine.

As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.

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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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 10
New Comment
642 comments, sorted by Click to highlight new comments since:
Some comments are truncated due to high volume. (⌘F to expand all)Change truncation settings
[-]75th260

I see also that the theories about Santa Claus's identity are equally as varied as the ones about Mr. Hat & Cloak. My take on this is similar to my take on H&C: we're meant to understand that Santa Claus is simply Dumbledore.

  • Santa Claus had possession of the Cloak of Invisibility and passed it down to Harry, who Santa somehow knew was its rightful heir.
  • Santa Claus also somehow knows about the full misdeeds of James Potter, many of which are known to no one else.
  • Santa Claus has the political and magical power to create Portkeys on the Hogwarts grounds and get away with it.
  • Santa Claus has deep insight into Dumbledore's true motives, and makes true statements about him without ever stating that Dumbledore is a different person.
  • Santa Claus knows little about Quirrell, but doesn't trust him.
  • Santa Claus says that he cares about Harry Potter's well being and wants him to be more careful in the future.

The only person we know for whom all the above facts are true is Dumbledore.

However, the "S" who left notes for Hermione is not Santa Claus. It's Severus Snape, who we know for a fact was the mysterious person helping SPHEW in its mission. The two signatures happen ... (read more)

I congratulate you on your 100% accurate pre-hoc explanation.

3anotherblackhat
Sirius Black fits Santa as well, if not better, though most of what we know about Sirius comes from Cannon. * In Cannon Dumbledore had possession of The Invisibility Cloak when the Potters were killed, but he didn't necessarily keep it. This wasn't mentioned in books 1-5 though, so EY is probably unaware of that detail. * James' best friend Sirius knows James' misdeeds better than anyone besides James himself, and is much more likely to speak proudly of them than Dumbledore. * The Portkey doesn't have to have been made by Santa - it could have been made by anyone at the Salem Witches' Institute. And it doesn't work on the Hogwarts grounds. * Santa Claus claimed Dumbledore would keep The Invisibility Cloak if he ever got his hands on it, which was completely wrong, and a rather insane thing to say if it's Dumbledore (which doesn't prevent it from being Dumbledore, but still...) * Sirius wouldn't know anything about Quirrell. Dumbledore presumably researched him before offering him the DA job. Neither would trust him. * As Harry's godfather, Sirius would care a great deal about Harry.
5Xachariah
There is also the Meta level to consider. Sirius Black is a major fixture of Harry Potter canon. He has not yet been featured or brushed off yet (eg the Weasleys). Every other major player from the first books has been given screentime so far. It seems incredibly unlikely for Sirius to make it to chapter 78 without a showing in one form or another.
3MartinB
I am pretty sure Santa is someone who works / lives in Hogwarts. Outsiders are not supposed to enter on their own. The bit about not trusting Dumbledore makes sense, even if the cloak came from him, since it allows Dumbledore to show off how trustworthy he is with little effort. And he can check how well Harry can keep a secret.
0coldlyrationalogic
One thing i Just wanted to point out, Mr. Hat&Cloak (or, as Hermione calls him, Mr. Extremely Shifty Guy) appears to shape-shift when talking to her. Has anyone considered that he could be a manifestation of Tonks? Thats a bit far fetched, but whoever he is, he either can shape-shift, OR create illusions to make it look like he does.
0glumph
But why would Dumbledore give Harry a Portkey in the first place? What reason could he have for giving Harry a route out of Hogwarts?

Nothing says the Portkey goes where it says it does. It could be a reasonably good test of "Harry Potter is desperately seeking a way out" if one just monitored his arrival in the destination.

Ch 78 You know, of all the things in the chapter, the law of Potion-Making seems the most important, by far - if I understand it correctly, it has staggering implications.

It's clear that you can extract more than purely physical processes from ingredients - since we have potions that bestow even entirely abstract concepts like luck(and canon!Snape claimed to be capable of brewing fame and glory, I'm unsure if MoR!Snape claimed the same).

So, could you, say, take a CD with some software on it and use it as a Potions ingredient in order to extract the mental work that went into programming that software, creating a Potion of Excellent Programming or something? Or, even better - could you take a copy of some brilliant scientific research paper, extract the brilliant scientific genius out of it and use the resulting Potion in order to create an even more brilliant scientific breakthrough? That's godhood in one shot right there.

I also have to wonder how Potion-Making interacts with the Mind Projection Fallacy. If you use a video game as an ingredient, can you create a Potion of Fun out of the video game or no? Fun isn't an inherent property of video games, it's in the minds of the players.

Might explain all those Nazi book-burnings. Grindelwald's human allies weren't just providing human sacrifices.

My intuition, my sense of fairness, says that you can't get back the work required to create information without sacrificing an appreciable fraction of the number of extant copies of that information.

I would guess that Magic and the Mind Projection Fallacy are sittin' in a tree, K-I-S-S-I-N-G.

You can make copies of books and of software CDs very cheaply. Given a law of conservation, it can't be the case that destroying (sacrificing) a cheap copy would gain you powerful results, or else you could generate infinite resources very quickly (and wizards would realize this).

Maybe destroying the last extant copy of a software would achieve the effect. One wonders what great magic was fueled by the burning of the Library of Alexandria.

9grautry
True, using copies to achieve that kind of power doesn't seem to make much sense - the law even says that you can get as much... let's call it "work" out of the ingredient as was "invested". It's true that there isn't much of an investment of resources in copies. So, forget the copies, let's use the originals. For example, could you take Einstein's original notes/notebooks(copying them beforehand, of course, so that you don't lose information), liquefy them into a Scientific Breakthrough Potion and use that Potion to quickly figure another brilliant breakthrough? That's the kind of thing I'm wondering about.

If this were the case, could Hermione sacrifice the paper marked 42 for a Potion of Humanism?

Or if Harry wrote down his thesis on Partial Transfiguration, Hermione could make a potion from that (without reading it), and write down whatever discovery she made under the influence of the Breaking the Laws of Magic Potion, which Harry could then use to make a potion...

6RolfAndreassen
No, because the notebooks do not "contain" the work Einstein did, Einstein's brain contains it. So you'd need the living brain of a scientist as brilliant as Einstein. Which may not be that difficult; Einstein was good but he was also lucky - he glommed onto exactly the right Big Problem at exactly the right time. It's quite possible that there are any number of equally-brilliant scientists alive today who just happened never to find their Big Problem. The point remains, however, that paper and notebooks are not sufficient, you need the brain which actually contains the comprehension. Moreover, since magic works by sensible-to-humans laws in the MoRverse, even if you copied the brain you'd have to use the original in the potion, and you only have one of those. The reason being, the copy hasn't "done the work" even though it contains the comprehension; and you can only get back out the work that was put in. This of course makes no sense, information should be information, but the laws of magic were apparently designed by a human.
5DanArmak
Not necessary living. And Einstein's brain just happens to be preserved. In fact, it sounds very much like people quarreled over magical ingridients:
3DanArmak
Or the same entity (not Azatoth) designed or modified both humans and the laws of magic.
5liamiak
Or perhaps the original diary of Sir Francis Bacon?
2ajuc
For it to be "fair" destruction of General Relativity you'll need the information to be destroyed, not container. So everybody everywhere in the universe would need to forget it AND you need to destroy every physic book with it, and wikipedia, etc, etc.
0bogdanb
Well, "invested" seems to be interpreted weirdly by magic. Sunlight is stored in acorns in the form of chemical energy, and the light you could get from a few acorns is about the same amount you'd get by burning them thoroughly (say, in oxygen flux). The effects of Harry's potion seemed to be much more powerful than that, I'd say of the level of the light absorbed by the entire oak for a year or more. So it seems like you can get something like "the entire effort" spent to produce something (grow a tree for a year) from just some of the results (nothing indicates they got all or even most acorns from a single tree).
3Dentin
Actually, I don't find the amount of light released to be far from the mark. Burning several pounds of acorns and converting all the released energy into light would be ridiculous - consider that even at a MJ per kilo, you're looking at a million watts worth of incandescent bulbs for 50-100 seconds (incandescents are only 1-2% efficient IIRC.)
5bogdanb
Actually, you might be right. I was thinking in terms of a pound or so of gasoline deflagrating, which would be bright if it happened really quickly but doesn't seem blinding when stretched over more than ten seconds (intuitions based on fires and movie explosions being much brighter than the real stuff). But I was ignoring the spectral focus and the lack of kinetic energy released. Lets's see: Wikipedia gives wood (red oak!) 14.89 MJ per kilogram. Spent over 60 seconds (the Chaos-Dragon battle is said to have lasted "a lot longer" than "very quickly") that would generate 248 kW. Direct sunlight is quoted at reaching 130,000 lux, but even with an albedo near 1 (conservativ, snow reaches .9) that's not bright enough to make you unable to see by shielding your eyes with an arm (based on recent experience of noon sun while skiing). So I'd guess the cauldrons would have to generate more than 1M lux for the effects described (maybe significantly more, brightness is nonlinear). Assuming conservatively that the illuminated surfaces in a battle to be a square at least twenty meters on the side, that's 400 square meters and 400M lumens. With pure green light (the brightest kind) you get 683 lumens/W. But the cauldrons gave everything except green, so let's say 400 lumens per W. So you'd need about 1MW of power to light a square of snow 20m on the side to ten times brightest daylight during one minute, or about four kilograms of red oak. Given that the illuminated area is probably much larger (including light lost to the sky), it's surface has much lower albedo (grass: .25, bare soil: .17, deciduous trees: .15 to .18), acorns probably take more than a gallon per four kilos (and I doubt they had time to gather ten kilos of acorns for both cauldrons), and that the quoted figures for oak involve burning with oxygen, I'd say that the energy in the acorns themselves falls short by at least an order of magnitude. But then again my errors are likely more than an order of magni
4Mass_Driver
Obviously it powered first Julius Caesar's conquest of the Mediterranean, and then Islam's conquest of North Africa.

Another thought: write down a description of a complex magical principle that you understand, but that the interdict of merlin would prevent someone else who was reading it from understanding. Use the parchment you wrote on as an ingredient in a potion to make a potion with the mental work needed to discover/comprehend that principle.

Poof, Interdict of Merlin loses its teeth entirely. :)

Another thought that occurred to me: Felix Felicis. No wonder it's hard to brew. Only way you could brew it is if you literally got lucky in the process of brewing it, by chance, so that you can take that "chance" and put it into the potion.

(hrm... might be able to automate the process of making Felix: Have a machine that keeps mixing the ingredients many times in parallel, ie, many "potential potions", and in the process does something like for each potential potion, has a coin (or some random bit source which can then be physically placed in the potion) which it flips a 100 times. It also tracks the results, and when one of the coins comes up all heads, it drops it into the candidate potion then calls up the wizard to complete the potion.)

Oh, and MoR!Snape did claim you could b... (read more)

Hee hee. But no, I didn't mean a "potion of cleverness", I simply mean "be clever and invent a potion. Then use that potion as an ingredient to place the quality of the mental work of inventing a potion into a potion... then use that potion as an ingredient, etc.."

And actually, we know Harry meant to investigate mental magic, but we're not sure if he ever got around to it. (And, of course, there is Rowena's Diadem, which would seem to be an intelligence augmentation device. If that's in MoR, Harry's got to do something with it at some point. (But then, harry hasn't yet really jumped onto the existence of the Philosopher's Stone, so... well, I guess everyone here's already waiting for when he notices that and Epic Rages at the wizarding world along the lines of "you mean you already know how... you... ARGH!")