Tonal machine

The best explanation I've come across so far:

The nagual is the unspeakable. All the possible feelings and beings and selves float in it like barges, peaceful, unaltered, forever. Then the glue of life binds some of them together. When the glue of life binds those feelings together a being is created, a being that loses the sense of its true nature and becomes blinded by the glare and clamor of the area where beings hover, the tonal. The tonal is where all the unified organization exists. A being pops into the tonal once the force of life has bound all the needed feelings together. The tonal begins at birth and ends at death, because as soon as the force of life leaves the body all those single awarenesses disintegrate and go back again to where they came from, the nagual. What a warrior does in journeying into the unknown is very much like dying, except that his cluster of single feelings do not disintegrate but expand a bit without losing their togetherness. At death, however, they sink deeply and move independently as if they had never been a unit.

Also, I think that these feelings and beings and selves aren't constant throughout multiple lives. Due to that, one can't say they were person X or Y in their previous life. Or, rather, they can say that but that's not entirely correct because the feelings, beings and selves mix differently (to some extent even during a single lifetime).

Although in Castaneda's "Tales of Power", this explanation is referred to as the sorcerer's explanation, this is scientist's explanation as well. At least, I think I've arrived at it through articles, experiments and logic. Personally I've considered sorcerer's explanation to be slightly different - assuming that every object is a conscious entity and has a spirit that you can communicate (and must not quarrel) with.

Hmm .. also, FullMetal Alchemist demonstrates this explanation nicely, though in a kind of reversed way.