Lanefan
Victoria Rules
If you're a player, sure; that lack of concrete evidence very likely reflects the knowledge of your character.Well, I did say I it would be unpopular
Mostly, I am coming at this from the perspective that people don't know for sure, do not have concrete, empirical evidence, of the overarching spiritual, moral, ethical, and metaphysical underpinnings of the universe are like. I like that degree of ambiguity (and yet I am a man of faith, so please understand that I am not, by any means, denigrating faith).
But if you're the DM I hold that you have to get this cosmology stuff nailed down hard during the design process, before starting play.
I'm of two minds here.I also don't like when the precious cosmology has to be hammered into every setting, regardless if it fits the rest of the setting, or if it removes elements that make said setting unique.
Each setting, and arguably each culture/species within each setting, should have its own (view of) cosmology, its own pantheon of deities, and so forth. This is a large part of what makes each of those cultures what they are. Players would learn of some of these through their characters, in play.
Buuuu-ut, underneath it all I also think there needs to be a universal underlying framework that all these things rest on, a framework that's portable from setting to setting and campaign to campaign such that it only ever needs to be designed once. This framework could be DM-side only, and while players may or may not learn about it in-character during a particular campaign*, they still won't know it applies everywhere.
* - my current campaign is crawling with Corellon Clerics for some reason; imagine their shock when a few high-level PC ones found out that Corellon in in fact just an aspect of another (framework-level) deity!
For me, in D&D setting terms, Spelljammer is far more interesting and fantastical than Planescape (except for the art, because DiTerlizzi is amazing).