I'm not sure how it worked in canon (and would expect semi-random behavior given Rowling's tendency to fudge world building details that a more mechanistic thinker might nail down) but in MoR it appears that legilimency allows the reader to perceive the "conscious surface thoughts" of the readee, plus the feeling of active reading (used by an occlumens to race ahead and put fake conscious surface thoughts in the way), plus the traces of past reading.

When Albus read Harry early in the story to look for traces he asked Harry what Harry had recently eaten so as to prevent himself from reading anything private in Harry's mind. If words can be used to redirect attention to banal issues so that it is impossible for even Albus to see more deeply, it stands to reason (to me anyway) that visibility is relatively shallow and that words could also be used to redirect attention towards the sensitive issues. So, HAC using legilimency probably couldn't get a verbal reason for lack of trust without a probe to raise "trust of HAC" in Hermione's mind, but once raised he would have been able to tell if she lied or detect any reasons that jumped into her mind that she didn't say out loud for strategic reasons... and not much more.

I could be wrong. "Word of god" might contradict me. But assuming I'm not, then my working model of the fic includes that HAC now knows, for example, that Harry has a deathly hallow (because Hermione would probably have consciously surfaced the most dramatic evidence that Harry totally trusts her when HAC asked about that stuff and that's pretty dramatic evidence). Given how many readers didn't even get that cycles of oblivation were being used on her I'd guess that something too optimized (to the point of silence) would be even less intelligible in text.

I guess a totally "optimized" oblivation/legilimency cycle could probably do a full loop within like 8 seconds and would just involve a "don't think of a polar bear" shout, reading everything brought up by that, then obliviate and repeat. We didn't see that happen at all. Either we didn't see it because it was impossible, or Eliezer didn't think of it, or Eliezer didn't think HAC would think of it, or it would have been too squicky and thereby violated the artistic permissions of the audience.

My bet is that this kind of manipulation would be impossible based on the in-story mechanics of legilimency and related spells... that the pragmatics of the process require a measure of indirection even with naive victims so that their eyes can't be closed, and their thoughts have time to percolate, and things only mentally accessible from within a specific conversational context can occur to them to be read, and so on.

When Albus read Harry early in the story to look for traces he asked Harry what Harry had recently eaten so as to prevent himself from reading anything private in Harry's mind. If words can be used to redirect attention to banal issues so that it is impossible for even Albus to see more deeply

I didn't interpret it that way. Rather, I interpreted it that Dumbledore didn't want to incidentally get data about any other thoughts, he just wanted to look for signs of prior tampering. In that limited context, he didn't want Harry to think about anything that wasn't Dumbledore's business. A skilled legilimens if they are trying might be able to still get more out of that situation.

9Desrtopa9yEven assuming those are the limits of leglimency, I think that "this guy seems really suspicious" would be pretty near the surface of Hermione's thoughts without any additional prompting.
6drethelin9ythe occlumency trainer harry hires is able to read deeply within harry's mind without a lot of trouble. I think thoughts are probably easier or harder to read based on how surface they are. Dumbledore made them think of something else so he wouldn't accidentally read anything private because of how EASY it is to read surface memories, not because thinking of something else prevents being read entirely.

Harry Potter and the Methods of Rationality discussion thread, part 9

by Oscar_Cunningham 1 min read9th Sep 2011725 comments

10


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

The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread.  This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.


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.  The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.

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.