ike wrote:
Although that's probably true today, I think that's a newer rationale. The reasoning behind banishing people from a given church or religion I think has its roots in the time before people started thinking about separating religion and governance. During that time there wasn't banishment "from the church", there was just banishment. And that essentially was a death sentence, or at least, that's the way people viewed it rather in spite of the fact that it's well known that a person can survive in isolation. So the threat of banishment from your village at the time was the church/government's way of enforcing the majority opinion about what was or wasn't moral. If a person did or suggested doing "immoral" things (like for example cutting their hair or walking through a particular "sacred" area), they could be threatened with banishment to keep them in line. Once we started talking about the possibility of separating our religious notions from our governance I think the church gradually evolved its rationale for banishment while the state gradually modified the concept to imprisonment. So now I think excommunication from a given church is really just a vestigial organ of the church kind of like your appendix.
I don't think it is a newer rationale, because a similar logic is held to by Protestants, as Protestant churches also will kick people out, and the Reformation put a high emphasis on Biblical groundings. Protestants will usually also stress that these actions are called for by biblical demands. Not only that, but the Catholic church historically has excommunicated kingdoms(which would not cause any physical death, but rather is purely a spiritual attack upon a kingdom) and is well known for using that sort of threat, and non-Christians did exist within Christian Europe, for example, there are the Jews. Not only that, but I don't think that the Catholics would just bother *just* banishing heretics, as they were well-known for killing heretical groups, such as the Cathars.