Reincarnation theory (friendslocked)
What I've picked up so far is this: reincarnation theory is complicated and controversial (for scientific as well as religious reasons). They've figured out how to measure and detect it, but no one really knows why it happens. The general idea, though, is that people produce and incorporate complex patterns, patterns that sometimes continue on past the physical existence of the person. I mean that in both ways--in terms of influencing the environment, and in terms of keeping going after the body dies. A person's pattern includes their physical conformation and appearance, their temperament and quirks and talents, and the circumstances of their life.
Most people's patterns are so loose or so well integrated with their surroundings that they just dissolve after death, which (some people think) is the way things are supposed to be. The presence of patterns also encourages other new patterns to form, so new people and new patterns get created.
A fair number of people's patterns are tight or knotted enough that they persist in some form after death, and these people end up getting reincarnated. But what happens with most of them is that their patterns are still loose or fluid enough to be changed by their surroundings--enough so that they're unrecognizable as their earlier selves. The instruments can usually track where and when the patterns have been (for long periods of time--they can't actually tell everywhere you've been because brief trips don't leave enough of an impression) and by going and finding the person's earlier version, you can calculate the percentages of material that the current version has in common with the earlier version(s). Overstrom's glasses were able to tell so much about us at Eupheme because the patterns of famous people (during their lives) have already been documented in this way--once the glasses spotted us, they just matched us up with the data that was already in the system. There are actually people who go around looking for reincarnations of celebrities, hoping to sell their locations and identities to fans or scholars or people like Tamsin & Thomas, although this is usually illegal.
Reincarnation is often correlated with space-time anomaly--either a fold or a rip or a strain or something similar. There are people who are reincarnations of people from their own futures, and some people think it's possible to be the reincarnation of someone from an alternate universe. It could be that different parts of the "fabric" are being touched together, and picking up patterns from each other--or that the pattern is actually moving from one area to the next in some way, and being changed as it goes. Some people think the pattern is like DNA, and it sneaks along through a series of different bodies and lives, only that different components of it show at different times. Some people think that the strength or knottiness of these patterns actually causes the rips and strains.
I don't know how Eupheme fits into this--the secondary reincarnations are apparently very unusual. Neither does TAS, and that's why they're keeping watch on it.