Assuming that the NPCs have some sort of minimal attention span. Key to my perspective on this is the notion that what folks are trying to do would require some sort of deception that's long term and sufficient to fool creatures within divine intelligence.
And no one wishes it back. And commune is just an example of one spell that provides this kind of information.
Right. DM fiat/design can absolutely solve this problem. The DM can rule that on Wednesdays every single NPC in the world hops on one foot for one hour. All I was trying to do was outline the issues that in (what I'm calling) the default DnD set up, this sort of thing would seem problematic to me.
Well that is the question, isn't it? Does Commune actually solve the problem or is a D&D world with ambiguity in the divine realm like a world where everyone arbitrarily hops on one foot every third wednesday of the month between 7:00 and 7:30?
The test case was proposed that you would just cast commune and ask "Is Zeus a god?" "Is Zeus chaotic good?" Let's suppose that you asked the question; would the answers really tell you what the situation was?
Consider the following possible situations:
A. Zeus is a greater god, he is chaotic good, the henotheistic god in question is an ascended mortal like the Ptolus deity
B. Zeus is a god like 4e Orcus is a god--a demon and a god at the same time, but he is disguising that fact and from the other deities and from mortals; the henotheistic god in question is an ascended mortal like the Ptolus deity
C. Zeus is a god like 4e Orcus is a god--a demon and a god at the same time, but he is disguising that fact and from the other deities and from mortals; the henotheistic god in question is an omniscient creator god who is good.
D. Zeus is a god, but the monotheistic deity in question is a creator god; he doesn't want to outright obliterate those of his servants who have claimed mortal devotion, but does not believe it is right to worship them.
E. Zeus is a god, like 4e Orcus is a god--a demon and a god at the same time
F. Zeus is not a god, he is just a demon prince who is channeling someone else's power.
G. The mono/henotheistic god in question is an evil rebel or demon prince and Zeus if both really a god and really Chaotic Good.
Now, we'll suppose that two priests cast commune or any other divination spell.
Priest 1 is a priest of the mono (or heno)theistic god in question.
Priest 2 is a priest of Zeus
A1. Is Zeus a God? Unknown/no answer or yes are both possible answers. Maybe because the Ptolus like god has reason to suspect that Zeus might not be a god. Yes because Zeus is obviously receiving worship and distributing spells.
Is Zeus Chaotic Good? Unknown/no answer or yes are both possible answers.
A2. Is Zeus a God? Of course. Is Zeus Chaotic Good? Of course
B1. Is Zeus a God? Unknown/no answer, and yes possible answers. Maybe because the Ptolus like god has reason to suspect that Zeus might not be a god. Yes because Zeus is obviously receiving worship and distributing spells. Yes because the appropriate handbook says that Zeus is the Demongod of such and such.
Is Zeus Chaotic Good? Unknown/no answer, yes, and no are all possible answers. Unknown/no answer because the Zeus depicted by the religion does not exist and has no alignment. Yes because the Zeus officially depicted by the religion has the traits that are associated with Chaotic Good. No because Zeus is really a demon who is chaotic evil.
B2. The priest will say, Of course Zeus is a god. Of course Zeus is Chaotic Good.
Whether his commune indicates that Zeus is Chaotic Good or not is another story--that probably depends upon how subtle the demon Zeus is being with his fake religion. In the event that the priest is lying, however, how would you know? Bluff can be a class skill for clerics with the right domain. Discern lies grants a will save (which clerics are notoriously good at). So does Zone of Truth.
C1. Is Zeus a god? Could be yes or no. If yes, it is because he receives worship and has the powers associated with gods in the experiences of mortals. If no, it is because Zeus is not a god in the same way that said Creator god is a god.
Is Zeus Chaotic Good? Yes.
C2. The priest will say, Of course Zeus is a god. Of course Zeus is Chaotic Good.
Whether his commune indicates that Zeus is Chaotic Good or not is another story--that probably depends upon how subtle the demon Zeus is being with his fake religion. In the event that the priest is lying, however, how would you know? Bluff can be a class skill for clerics with the right domain. Discern lies grants a will save (which clerics are notoriously good at). So does Zone of Truth.
D1. Is Zeus a god? Could be yes or no. If yes, it is because he receives worship and has the powers associated with gods in the experiences of mortals. If no, it is because Zeus is not a god in the same way that said Creator god is a god.
Is Zeus Chaotic Good? No.
D2. The priest will say, Of course Zeus is a god. Of course Zeus is Chaotic Good.
Whether his commune indicates that Zeus is Chaotic Good or not is another story--that probably depends upon how subtle the demon Zeus is being with his fake religion. In the event that the priest is lying, however, how would you know? Bluff can be a class skill for clerics with the right domain. Discern lies grants a will save (which clerics are notoriously good at). So does Zone of Truth.
E1. Is Zeus a god? Yes
Is Zeus Chaotic Good? No.
E2. The priest will say, Of course Zeus is a god. Of course Zeus is Chaotic Good.
Whether his commune indicates that Zeus is Chaotic Good or not is another story--that probably depends upon how subtle the demon Zeus is being with his fake religion. In the event that the priest is lying, however, how would you know? Bluff can be a class skill for clerics with the right domain. Discern lies grants a will save (which clerics are notoriously good at). So does Zone of Truth.
F1. Is Zeus a god? No.
Is Zeus Chaotic Good? No.
F2. The priest will say, Of course Zeus is a god. Of course Zeus is Chaotic Good.
Whether his commune indicates that Zeus is a god and is Chaotic Good or not is another story--that probably depends upon how subtle the demon Zeus is being with his fake religion. In the event that the priest is lying, however, how would you know? Bluff can be a class skill for clerics with the right domain. Discern lies grants a will save (which clerics are notoriously good at). So does Zone of Truth.
G1. Is Zeus a god? No.
Is Zeus Chaotic Good? No.
G2. Is Zeus a god? Yes. Is Zeus Chaotic Good? Yes.
Some of these scenarios assume deception of the level to deceive gods (which is not exactly new to D&D or to mythology--that's one of the things that demons and trickster gods (and sometimes giants) can sometimes do in story and myth). Some of them don't.
Note that, in all cases, the answer that anyone would receive from the priest of Zeus is unchanged and the answer that the priest of Zeus would receive will only change if he is initiated into the cult of the true-evil-Zeus. In most of these cases, all of which presume different scenarios about the divine reality, the exact same set of answers are possible and most notably, in probably the two cases where there is no ambiguity as to which answer might be correct--cases F and G--the answers are exactly the same even though the situation is more or less reversed.
And this assumes complete honesty upon the part of any putatively divine entities in question and no covenant of silence or any other such device by which certain questions might not be answerable. It also assumes that the answers to the question are static and unchanging and ignores the possibility that an individual could become a god by gaining sufficient power (as Orcus did in the transition from 3.5 to 4th edition and Vecna did in the transition from 2nd edition to 3rd edition). In that case, the answer might have been "no, Zeus is not a god (he's really Orcus)" three years ago and "Yes, Zeus is a god (he's really Orcus)" this year. And, it always could be that Zeus was chaotic neutral (on a good day) when Homer was writing stories about him but has since hired an image consultant and taken sensitivity training and cleaned up his act so that he is now chaotic good. In that case, the answer could have been, "no, he is not chaotic good" yesterday and "yes, he is chaotic good" today.
Additionally, the PHB itself suggests that commune is often answered by an important or ranking servant of the deity rather than by the deity directly. In a lot of cases, the answer is ambiguous and it would not necessarily be going outside the RAW to suppose that the same question could yield a different answer based upon which high ranking servant of the god in question answered. "The title god implies worthiness to be worshipped, therefore demon-god Zeus is not a god" is as legitimate a reason for a no answer as "Zeus is a demon with the power of a god--he is a deciever and a usurper but technically, he is a god even though you shouldn't worship him" is a legitimate reason that such a servant might answer yes. I can imagine fantasy theologians saying that there is some ambiguity on the topic of whether or not Zeus is a god and there are many theories as to what that means, but either way, it is clear that we are not supposed to worship him. (People being what they are, it also likely that some fantasy theologians would seize upon that ambiguity as an excuse to participate in offerings to Zeus--especially if they were socially expected, enabled them to meet wealthy potential patrons, or involved hedonistic orgies).
It is also even likely that, whatever the situation, charlatans would attempt to muddy the waters with false claims of definitive answers to your burning questions through real or fake commune spells. We have had plenty of people in the real world from Montanus to Joan of Arc to Joseph Smith to Mary Baker Eddy claim to hear from the beyond/god and I'm pretty sure that they can't all have been telling the truth. In a fantasy world where supernatural claims are more generally plausible, I would expect such things to be more common. From an NPC's perspective, this would make verification by divination more suspect--maybe from a PC's perspective as well if different divinations came up with different answers on the subjects. (If Contact Other plane yields a different answer from Commune, you know there is deception somewhere).
Toss in those sources of ambiguity and there is no guarantee that PCs would be able to obtain a clear picture of the game-world reality by simply using commune and not much of a chance that they would be able to convince NPCs to change their minds on the basis of a commune spell.