I’ve been aware of the AD&D setting called Eberron for a long time; what I haven’t quite processed is what this detail might mean:
As described on page 35 of the Eberron Campaign Setting, it is possible for a cleric to have no god and still perform divine magic. This is not, however, the same as having no beliefs; it still requires a strong commitment to an ideal or a philosophy.
Sounds to me like one could (just for the giggles of it) play an atheist cleric in the setting. Especially since the article linked above says things like these:
While many of the deities are portrayed with anthropomorphic icons, they do not walk the mortal world or even the known planes. If they exist at all, deities inhabit a higher plane of existence — a realm that cannot be reached with planar travel. [...] If the gods may not even exist, who do you commune with? [...] Divine magic exists [...] [but a] skeptic may counter that it is the collective unconscious or merely a powerful outsider. [...] Ultimately, belief in a deity is a matter of faith.
In other words: in Faerun (Forgotten Realms) atheism would be, well, stupid, and also likely to bring Bhaal (not a nice guy) to your doorstep with a big stick complaining about your behavior. Eberron seems like a place open to mace-swinging, spell-slinging, zeal-burning priests of the church militant of raving over-the-top atheism! On, on, smash those altars and raise ours in their place! Crush their armies! Repels their magicks and show them the sting of ours! No gods, no fear! Drive them to the sea and utterly obliterate them! Dash their hopes, burn their houses, convert their families, and hack down every bugger who raises a hand against us! Decimate them by sword and word — er, mace and word as clerics don’t use edged weapons — smash and blast them to tiny shivering pieces and let the idols of their dead gods join them in their oblivion! Show them no mercy! Show them what militant atheism really is!
I mean, an interesting thought experiment, and no doubt would be good for letting some steam out. (But wait. “Commitment to ideal or philosophy”? So you could technically speaking have Priests of Communism, Priests of Capitalism, Clerics of WIN/FAIL (“Summon failboat”?), Paladins of Nietzsche, and Cultists of Nihilism? The last ought to be fun. Warrior: “Hey, nihilist! Those gnolls are attacking! Cast something.” — Nihilist: “Life is pointless and every moment but adds to our pain. I cast Instant Party Suicide.” — GM: “Okay; sudden brain aneurysms occur, everyone dies. Gnolls graphically desecrate your bodies. Roll for new characters.”)
(Shortly afterwards, after throttling: “Hey GM, can I play a Cleric of Self-Fouling Incapacitating Trauma-Inducing Cowardice? I think it’s a meme, a cliche, a stereotype and an ‘ideal’ of defeat, so it’s applicable, right?” — GM: “And with the special ability of, what, ‘turn stomaches’?” — “That, and ‘Sudden Party Body Evacuation’ and ‘Instant Party Catatonic Withdrawal’.” — To which ex-Warrior remarks, “Wait. I like the sound of those, especially if we run into something too big to handle, but would you still mind explaining what they really do?”)
Then again —
“So, an altar. Which god do you serve here?”
“What, a goddess? Is she a hot one?”
“No. No god.”
“Oh, I see. Is it spelled No, Noh, Noe or what?”
“Listen, you obstinate heathen swine. We are the atheist clerics of N’gaah, and we serve no god, no divinity, no superlative power or root of existence, in this church of ours.”
“…isn’t that kind of pointless?”
“Well, we still get the same benefits. Like spells. Except our ‘turn undead’ is a bit different.”
“How’s that for an awesome ability?”