> How does this not mean that ultimately, you run out of practitioners? Are only direct descendants allowed to take part? Yep, some have a heavy focus on a kin

> How does this not mean that ultimately, you run out of practitioners? Are only direct descendants allowed to take part? Yep, some have a heavy focus on a kind of ethnocentrism or blood-continuity. Even marrying in sometimes won't get you inducted (indeed, it may mean the other partner is shunned). > Does this include things like having special glasses that allows decryption of the text until they were lost before ultimately losing the text itself? Usually it means not having texts, to any great degree, or having some but carefully guarding them. Think: Freemasons, but even more serious about keeping their proceedings and rules and ideas secret from outsiders. Often this is coupled with a mostly-oral tradition. Judaism's kind of an interesting variant on these—it can be a bit ethnocentric and exclusive (see: maternal lineage rules) and doesn't really seek converts, but has also become enough things to enough people that joining some variant or another is usually possible, for outsiders; and it's heavy on only the initiated being able to meaningfully engage in theology, but, crucially, those proceedings are mostly in letters (in the broad sense), and a great deal of it takes place more-or-less out in the open, such that one can walk into a book store and come out with an armful of deep Jewish theology without needing to ascend some rabbinical hierarchy first. You can see in Judaism a distorted version of these other, extremely-insular religions that are in decline, but with enough of a twist on their rules and practices to keep the religion vital and alive.