I know layer cakes have been used for all manner of metaphors. Today, I'm going to use it to help describe fantastic societies in terms of culture. We all know the standard tropes of how different the people are who live on the other side of the mountains, or whatever other geological divide separates your main kingdom from your other kingdoms. You may even have gone through and developed deep and interesting cultures for every land, detailing histories, philosophies, and the architecture of culture that generally shapes thought.
The issue is one that I've confronted over and over again and had pointed out to me by other people. So, after consciously thinking about it for a while, I thought it might be a good idea to highlight it for others to consider. That is this: once you have a very well-defined and developed system of thought, you must also consider how that system is reflected by differences in the social strata.
It's easiest to do this with an example: in the novel I'm currently writing, there is a belief-system called the Kyrian Confession. One of their core beliefs is in a deity that is a Platonic ideal of the One. It has no consciousness, per se, and no personality. The Divinity is equivalent to the Active Intellect or the principle of unity from which all things emanate.
One of the corollaries of this is that the Divinity cannot hear prayers, or even "know" individuals. The Divinity has knowledge of genera, not specific things, because it is the agent intelligence or the principle of unity.
The common folk don't understand or choose to ignore this belief. They pray to the Divinity. Colloquialisms referring to it as an entity have developed. They refute, refuse, or reject the elements of the system that don't mesh with their needs. This rejection doesn't take the form of an active resistance; indeed, if a prelate or priest carefully explained the idea to them, they would probably agree after some convincing that it was true. But, most likely, it wouldn't affect their practice.
This difference, between the philosophical intelligentia and the every day use of cultural norms, is important. Societies aren't homogenous across all levels. Sometimes, as the wealthy in Roman society, one class is a single unified culture. Sometimes, classes differ in both specific regions AND amongst themselves, causing a great profusion of differences. The gap of wealth and prestige creates many cultural artifacts amongst all the strata it separates.