If you’re aiming to describe a pluralistic society in which a number of faiths exist, then the uniqueness or commonality may depend, in part, on whether the religion is revealed or “compiled”. Personally, I believe there may be a revelation in the seed stage of most, if not all, religion, even the ones we think of as animistic. But for the sake of this discussion, I’d say revealed and compiled (or accreted) religion are two distinct forms.
A compiled religion is a response to universal questions: Why does it rain? There must be a power behind the rain that knows when we need rain. What about the Sun — what’s up with that? There must be a deity or power responsible for that, too. Let’s not get them angry — what do you think they like for breakfast?
A revealed religion is simply that: An Avatar or Messiah arises who seems not to be a product of His times. He is inherently different — knows things He shouldn’t know, understands things no one else seems to grasp. He usually claims some connection with a previous revelation (“If ye believed Moses, ye would believe me, for he wrote of me,” as Christ put it.) and He says outrageous things: material existence isn’t everything, love your enemies (yeah, even the Samaritans—sheesh), you’re all brothers under the skin, women and men are equal, etc.
Among our current revealed world religions (i.e. Hinduism, Judaism, Buddhism, Christianity, Islam, the Bahá’í Faith, etc.), there are a body of core teachings that are identical. The Big Three, I guess you could call them:
- Love God;
- Believe in the One He sends;
- Obey His commandments.
The top commandment we are called upon to obey, in all religion, is to love each other. (Really? Aw. Does that mean I have to love <your list of unlovables here>.)
What we know in the West as the Golden Rule: “Therefore, all things whatsoever ye would that men should do unto you, do ye even so unto them.” exists in similar form in all of the above-mentioned faiths. It’s important enough to Christian doctrine that Christ associates it with the “narrow path” that leads to salvation. It’s important enough to Hindu doctrine that Krishna calls it the “sum of duty”—important enough to Jewish teaching that Hillel says “this is the entire law; all the rest is commentary.”
Now, how a faith gets from that to holy war … well, that’s the stuff of epic epics. I could write from now until Sat Yuga (that’s the Hindu version of the Golden Age) and not exhaust all the stories concealed in that bizarre human journey from “love your enemies” to “God hates X.”
Another commonality is that each of these religions has two sets of principles: the spiritual and the social. The spiritual teachings (think Golden Rule) seem to be constant. The social ones change. Sometimes drastically. Think of the kashris or food laws of Judaism. They’re not observed by Christians because Christ didn’t renew them and Peter had a vision that seemed to abolish them. Christ’s commentary was that it wasn’t what a man put into his mouth that made him righteous, but rather what was in his heart. The tension between the relative importance of the spiritual principles and social laws is another rich source of conflict that can inform the cultures you write about.
In writing about an existing, real-world religion, a writer certainly could opt to leave out any of these common elements. And I think, depending on the age or phase the religion is in, that’s realistic. For example, Christ’s exhortation to love our enemies and Muhammad’s warning that “God loveth not the aggressor” have fallen on ears so deaf during some periods of history that we have been treated to horrific atrocities committed by avowed believers. In some cases, the commission of these atrocities has been institutionalized to a point approaching doctrine.
The takeaway from this is that religious history is rife (and ripe) with elements that can enrich story and illuminate and motivate characters. Whether you’re fictionalizing accounts of existing faiths or making up new religions out of whole cloth, life offers a much fabric for art.