It seems to me when you look at ancient religions, they mostly function as ways of hardening tribalism. Ancient religions did not really ever say “your gods are not real.” They said, “your gods are inferior.” This fact is sometimes used to prove the greater perniciousness of Christianity, since it drove Christianity to proselytize others, and this is a great evil, to the modern mind. The ancient pagans did not often try to proselytize the followers of other gods. But the forcible conversion of unbelievers is no part of Biblical Christianity and happened more rarely than most people seem to think. On the other hand, when you say, “your gods are inferior,” given the way religion worked in ancient times as an inseparable aspect of a particular ethnic group’s culture, what you were actually saying was, “you are inferior.” The inferiority of another people was justification for attacking and enslaving them. And how did you know they are inferior? Because you were able to attack and enslave them. If their gods were stronger than your gods, they would have protected their people from you. So yes, they didn’t proselytize followers of other gods, but they did attack and enslave them all the time.
This is a fascinating article on Slate Star Codex about tribalism, group identity and ideology. It is long, but well worth it, and will help you understand a lot of what I’m on about here. But here’s the basics of what he’s talking about:
Nations, religions, cults, gangs, subcultures, fraternal societies, internet communities, political parties, social movements – these are all really different, but they also have some deep similarities. They’re all groups of people. They all combine comradery within the group with a tendency to dislike other groups of the same type. They all tend to have a stated purpose, like electing a candidate or worshipping a deity, but also serve a very important role as impromptu social clubs whose members mostly interact with one another instead of outsiders. They all develop an internal culture such that members of the groups often like the same foods, wear the same clothing, play the same sports, and have the same philosophical beliefs as other members of the group – even when there are only tenuous links or no links at all to the stated purpose. They all tend to develop sort of legendary histories, where they celebrate and exaggerate the deeds of the groups’ founders and past champions. And they all tend to inspire something like patriotism, where people are proud of their group membership and express that pride through conspicuous use of group symbols, group songs, et cetera. For better or worse, the standard way to refer to this category of thing is “tribe”.
Tribalism is potentially present in all groups, but levels differ a lot even in groups of nominally the same type. Modern Belgium seems like an unusually non-tribal nation; Imperial Japan in World War II seems like an unusually tribal one. Neoliberalism and market socialism seem like unusually non-tribal political philosophies; communism and libertarianism seem like unusually tribal ones. Corporations with names like Amalgamated Products Co probably aren’t very tribal; charismatic corporations like Apple that become identities for their employees and customers are more so. Cults are maybe the most tribal groups that exist in the modern world, and those Cult Screening Tools make good measures for tribalism as well.
His large point is that a great deal of the ideologies people claim has not much to do with the actual content of the ideologies, and more to do with the groups of people they affiliate with, which happens for complex historical reasons. So, the ideology is not the movement. I think he’s very much right about the way people in general behave, including an awful lot of Christians. I don’t think it’s totally a coincidence that most people in Norway at a certain point were Lutherans or that most Spanish people were Catholics. I don’t think there was necessarily a genetic predisposition to those religions in those areas. I think that history happened, and history ended up with those different faiths becoming dominant for lots of historical reasons and then most people fell in line, because group identity and tribalism really is that powerful.