In the aftermath of the prophecy, his manipulation of Snape and Lily netted him a defeated Dark Lord, a double agent and powerful ally, and a newly horcruxed hero. If the prophecy hadn't occurred, he'd instead have... a bouncing baby boy. It's hard to see what he hoped to accomplish by driving Snape and Lily apart if he didn't intend to prod Voldemort into attacking the Potters.
One possibility is that he didn't intentionally drive Snape and Lily apart. I don't think there's enough evidence of that to overcome the prior probability that Trelawney's prophecy was genuine. Note that Dumbledore himself seems to regard the prophecy as genuine---witness, for example, his apparently genuine interest in discovering the "power [Voldemort] knows not."
Here's another way of looking at it. Assume Dumbledore planned in advance to defeat Voldemort by (i) convincing Voldemort of a false prophecy that would lead him to attempt the murder of a baby, and (ii) somehow manipulating the baby's mother into either performing ritual magic herself, or causing Voldemort to perform ritual magic that would bring about Voldemort's death when he attempted to kill the baby. We might now ask, is there a simpler way that Dumbledore might have tried to enact (i) and (ii), other than the means you have suggested?
Note that a priori, assuming that Dumbledore is primarily concerned with defeating Voldemort, there is no reason for Dumbledore to deliver the false prophecy to Voldemort via an agent who is in love with the mother in question. He must then rely on the agent not understanding the prophecy in time. Furthermore, if the agent figures out the prophecy after relaying it to Voldemort, Dumbledore must then rely on Voldemort disregarding the agent's request to spare the mother. So going out of his way to push Snape and Lily apart, and then using Snape as a messenger, seems like a very unintuitive way for Dumbledore to execute this plot. Why not keep Snape and Lily together, see that they have a child, and then deliver the false prophecy to Voldemort via some other agent?
Now, personally, I do think it's a possibility that Snape and Lily were driven apart by Dumbledore, maybe even intentionally. But I don't think it was for this reason.
Ah. See, my prior probability that Trelawney's prophecy was genuine is not very high.
This story has an epidemic of false prophecy. This looks to me like it's intended to prime the reader to accept that an apparently true prophecy is actually false. I also think this is a consideration, but that appears to be a minority view. I'm expecting a false prophecy, and I'm looking for a reason for it to have occurred and apparently been fulfil...
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 81, which should be published later today. The previous thread passed 400 comments as of the time of this writing, so it will pass 500 comments soon after the next chapter is posted, if not before. I suggest refraining from commenting here until chapter 81 is posted; comment in the 12th thread until you read chapter 81. After chapter 81 is posted, I suggest all discussion of previous guesses be kept here, with links to comments in the previous thread.
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.) When posted, chapter 81 should appear here.
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, ten, eleven, twelve.
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: