This is a thread for discussing my luminous!Twilight fic, Luminosity (inferior mirror here), its sequel Radiance (inferior mirror), and related topics.
PDFs, to be updated as the fic updates, are available of Luminosity (other version) and Radiance. (PDFs courtesy of anyareine). Zack M Davis has created a mobi file of Radiance.
Initial discussion of the fic under a Harry Potter and the Methods of Rationality thread is here. The first dedicated threads: Part 1, Part 2. See also the luminosity sequence which contains some of the concepts that the Luminosity fic is intended to illustrate. (Disclaimer: in the fic, the needs of the story take precedence over the needs for didactic value where the two are in tension.)
Spoilers are OK to post without ROT-13 for canon, all of Book 1, and Radiance up to the current chapter. Note which chapter (let's all use the numbering on my own webspace, rather than fanfiction.net, for consistency) you're about to spoil in your comment if it's big. People who know extra stuff (my betas and people who have requested specific spoilers) should keep mum about unpublished information they have. If you wish to join the ranks of the betas or the spoiled, contact me individually.
Miscellaneous links: TV Tropes page (I really really like it when new stuff appears there) and thread. Automatic Livejournal feed.
Already gave a number of possible workarounds to demonstrate that any ad hoc rule will leak. This reminds me of computer security - someone puts forward an ad hoc system, someone else immediately breaks it, the first patches the exploit, and so on ad infinitum until eventually the patches start introducing as many security flaws as they fix and they just give up.
I went back and re-read the scene. That could be the right explanation.
But that's not much better. Nothing in the scene forces Alice & Jasper to be there. For all we know, Elspeth could have run through the exact same mental steps with them on the other side of the planet (assuming A&J had telephoned with news of their defection or something): 'Magic, would comparing A&J to Del convince someone of the comparison?' 'Nope!' 'Oh good.' In fact, since truth or falsity do not change, Elspeth could as easily have worded her analogy as 'would comparing A&J at the instant they called to Del convince someone?' and gotten the same answer.
So your reading brings Elspeth down from logical omniscience to 'merely' being able to find out anything anyone has ever known (and maybe will know). Which is still so impressive a power that Alicorn couldn't've intended it.
Her magic changes what she says when she's communicating with people. I agree, nothing in the scene forces A&J to be there, but Elspeth's power--as I understand it--requires her to be communicating to the people she's testing for it to work.
Now, the fact that her magic now has an avatar might change the rules, but as Alicorn obviously didn't intend for it to work like how you are describing, you can assume that her magic is still limited to needing to be in communication with the person in question for it to determine whether the analogies fit.