Anyway, to the point-we were speaking about the potential benefits of schisms & sects, well how about this?
Lets assume that the ability to set the "Doctrine" of a religion belongs only to the founder of the Civ or the Civ which currently controls that Religion's Holy City. This means there might be a lot of Civs who adopted that religion, but are no longer happy with the benefits/penalties they provide. Lets use a hypothetical, in-game example.
The Greeks found Hinduism, & establish it as a Fundamentalist (bonus happiness; science penalty), Ascetic (Bonus Happiness & Health; money penalty) & Militant (bonus XP, religious military unit (Thuggee); happiness penalty from non-state religions & diplomatic penalties) Religion. Now the Greeks can alter these doctrines (at a cost) at any time they want-& the changes will flow to all cities with Hinduism as the State Religion (or only those which have built the appropriate temples etc).
Anyway, early in the game the neighbouring Romans adopted Hinduism as their State Religion, but now no longer like the Doctrines of the Faith. They have a few options open to them: (a) they can use diplomacy to urge the Greeks to change the doctrines, (b) they can launch a war to capture the Hindu Holy City, (c) they can change to another religion or (d) if they have an available Great Prophet, they can force a schism. By forcing a schism, they gain long-term control over doctrine-an option not open to them in (a) or (c), but without the cost associated with (b). They will earn the instant enmity of the Greeks (though this should be modified by how strong a religious flavor the Greek leader has), but this could be overcome-in time-through conciliatory gestures.
Of course forcing a schism should *not* cause all your cities to change religion. Indeed, very few cities should convert at first-forcing you to expend the effort to spread your new Sect. There should also be issues with spreading the new Sect to cities where the old religion still resides, dependent on the respective Tolerance of both the new Sect & the former religion However, another benefit is that it allows the player to form entirely new diplomatic blocs-in a way that Static Religions don't allow!
Aussie.