LogFAQs > #905457491

Philosophically? It's what successor's teachings should be held as doctrine.

Practically? It's a dispute between two factions with slightly different interpretations of an ancient doctrine, which has the potential to shift the power structure between said factions.

That being said, it's really no different than Christianity, so it shouldn't see too foreign. In fact, it almost perfectly mirrors the schism between Orthodox and Catholic Christians, who disputed Paul's successor(s) (with the former seeing it as an even split between the five Patriarchs, and the latter thinking that the Pope in Rome should rule over the others) and as far as I can understand, Shia and Sunni have a lot more in common than Catholicism and Protestantism.