The relative abundance of True Faith and what level of angelic/saintly guidance is available (and whether or not this can sometimes be spoofed by infernal lies) is entirely a troupe decision.
In Mythic Europe (within the Christian world at least) what is sinful/heretic etc is defined by the church through canon law. Whether or not a particular piece of canon law is consistent with the Divine is an entirely different question. If your characters do somehow discover that some particular piece of canon law is actually inconsistent with the Divine, then what your characters do about that discovery is a story.
In real church history, people did not of course, talk about the Divine realm, etc, however the church changing its mind (for various reasons which could perhaps include Divine Revelation) about what was and was not sinful/heretic and other theological questions was something that happened. This is exactly one of the reasons why there are ecumenical councils, and schisms, etc. There is thus plenty of real world precedent and inspiration for what might happen when parts of the church conclude that other parts of the church are wrong about something.
That to me is the root of most of the frustrations I have in Ars Magica- I like to get under the hood so to speak- find ways to combine Covenants with City and Guild, need a cosmology to unite the realms, and keep getting "this is just the way it is, pay no attention to the man behind the curtain" I think I would be happier if the economics were more integrated (different topic) and the entire divine realm book were stamped with something like "This is how it appears to work from hermetic observation and may not be how it actually works"
True Faith? Heretics who wander into the wilds are more likely to have it than Church people. Nor does the Church have the tools to assess it. Those various Divine Mighters? Also not going to follow Church Orthodoxy. Especially if a Muslim Angel decides to bother a Christian.
Not really sure what benefit it provides to the game. I suppose its nice to know the bare bones of what gets Divine Sanction, but that's not much of "this is right/this is wrong" its more of "EVERYONE IS WRONG!" If you worship the creator/sustainer god and only that god, (or goddess, or great spirit, or cosmic horror) its Divine. As I have said before, I'm not a fan of the list of virtues and sins. Maybe even explicitly go the discworld route: Kill all missionaries on sight. If they make you think you're damned you will be.
Here is where I wonder about the question of monotheism-
Say my character (in Hibernia) worships Calleach, Mother of All. She revers the other Gods and Goddesses of the Tuatha De Danu- where is the line (or is there one) between that and revering the saints in Catholicism?
I believe we call that Divine Worship. A magical Calleach, Fae Calleach or Infernal Calleach may show up and yell at you, but worshiping the Creator and revering other people sounds like a pretty clear example of a Divine Religion.
If the worship you describe is a Divine religion, then it's a Divine religion. If not, then it isn't. There is no special formula to work out whether it is or isn't. The way to decide is to look at the RAW, and if it isn't noted in RAW (or if your troupe doesn't like what is written in RAW), then your troupe decides.
There is a big 'if' here, of course. How would the concept of silveroak's character benefit from her worship falling under the Divine?
I have a character, who is an un-Gifted Redcap of partly Lithuanian, partly Sorbian descent, and a devout Pagan. He revers in particular Potrimpos, whom he considers his glorious uncle and celebrates especially when the rivers swell and spring breaks. He pities alienated Christians, who need to hope for paradise as a consolation price for not being able to take a full place in this world any more. Yes, he is polite to the poor devils, who are just too many and too densely packed, but will not enter their churches or graveyards. He is very educated, knowing Divine Lore, Faerie Lore, Magic Lore and Magic Theory, hence also roughly recognizes Divine Auras and their boundaries - but would be as horrified as a Christian priest to find a new Divine Aura in a spring glade after a revel in his uncle's honor. To him, Divine Auras are the supernatural manifestation of alienated worship, and he is quite content to find no Aura at all around the rivers swelling in spring: this shows how his uncle is part of his world, and not of some beyond or empyreum.
Theoretically speaking, my Redcap's religion is clearly an immanent one, and the Divine is expression of a transcendent being which to him is alien, even somewhat cthulhoid. If there is an Aura for immanent powers, it is Magic. The Redcap can e. g. easily sympathize with the Bjornaer protecting their ancestor sites and Great Beasts.
The companion he recently attracted to his revels is the covenant goatherd: strongly Faerie tainted - but she is fun, and you must not be too choosy nowadays.
And finally there are strange, ragged Christians appearing around his covenant, who have some kind of hymn to nature which makes some sense, and which they call 'canticle of the sun'. Do they begin to see what they were missing all the time?
Cheers
EDIT: Checked against character write-up once more.
Part of the issue is that the rules as written basically include the idea that divine worship is right and worship of magical or faerie entities is wrong and deluded. Personally I prefer the idea of any really divine figure existing through all 4 realms- while my example is someone who could be considered polytheist or monotheist depending on perspective, and should be entitled to use the divine auras. It should also be noted that divine auras require a congregation to build and sustain, so any divine aura grove won't be all that secluded...
Yeah, this is what bugs me about the list of sins and virtues. I would have gone for making it reasonable to believe that the Divine is a jerk. Who gives help to both sides in a war? The Lord of War probably would. That guy is an asshole. Too much values dissonance to say "good" IMO. Saying that a monotheistic religion always leads to the influence of a Cthuloid entity IMO is reasonable. It makes for a cool setting. Saying the guy who acts like the The Lord of War is good... not so much.
I need to ask now. Do you refer to the brief summary of sins and virtues in medieval Christian philosophy in RoP:D p.76 right box? Why does that bug you? Nothing there is cast into rules, not even hinted at as generally applying in game. So where's the problem
'Good' is a concept scholastic philosophers tried to define (en.wikipedia.org/wiki/Peter_Abel ... ical_works) and Cathars missed in the world. But it always requires a definition and introduction, before applying it in medieval religions and beliefs.
I think the problem you're encountering is that in Mythic Europe, a great majority of people the characters are likely to encounter believe that statement to be the case. So the setting, at least, should support that idea. I believe that means that the divine realm should be able to have a meaningful effect on the game world, at least as much influence as the other realms, so that these masses can point to it and say, look, the divine is powerful, therefore it is my favorite realm, and since it is my favorite realm, it is the best realm. Other characters don't have to agree with them, but at least in the setting as written this should be an easy and justifiable leap to make.
I also think it's important to separate the rules from the setting. There shouldn't be anything in the rules that says that worshiping the divine is the only correct way to worship, or that those who throw in with faeries or magical beings are wrong or deluded. (Or the infernal, for that matter.) The rules should confirm that those characters associated with the realm receive demonstrations of the realm's power. If you do worship the divine, the game rules give your character appropriate divine rewards. If you worship faeries, the rules give the character other appropriate faerie rewards. All this is true, yes?
I believe the authors of the Realms of Power books tried very hard to come up with thematically appropriate manifestations of each realm's power, and for the most part were very successful. There are admittedly a few rules systems in The Divine book that are very Christianity-centered and don't translate very well to other faiths (saintly intercession and relics immediately come to mind), but I don't think that they prove that Christianity is right so much as suggest that the divine is terribly schizophrenic. Divine tempers are organized against the seven deadly sins, which is again very Christian, but I generally think of them as more of a framework of the sort of environments that divinely-focused characters can foster. Perhaps there are other tempers associated with other divine religions?
Actually, one thing I can think of that might mechanically support the "divine realm is paramount" idea is the manifestation of sin. There are holy powers that can recognize the stain of sin on an individual. The fact that some characters can see this might suggest that the actions taken by the targeted character were "wrong" or "right" according to the divine character's religion. But if we see this effect as instead probing the target's memories, looking for particular actions that the divine character believes oppose her faith's tenets, not seeing signs of objectively "wrong" behavior, then the value judgment on these actions is kept in character where it belongs.
Can you come up with some more examples of rules that you feel enforce the "divine realm is right" idea?
Aside from the name "divine realm" which pretty much starts the conversation off with a nuke by insisting all non-included beliefs are inherently not divine in nature? So if you worship Calleach, or Pan, or Ra, too bad, your God isn't divine.
Then there is the complete imbalance of power- divine realms trumps everything. Even within the book on the realm of magic they suggest that divine realm is more powerful because it is a more fundamental level of reality.
Then there is the way the book twists it's own rules to ensure religions related to Christianity make the grade while arguably more monotheistic ones do not. The Cult of Mithras worshiped the son of a chthonic goddess who slayed a divine bull and was adopted by the god of the sun and the king of heaven as a reward for doing so. While it was merged into Christianity due to similarities of rituals, and makes an interesting bridge from how Yam, the Babylonian demon god of he dark sweet waters became the solar all father and connects the myth of Gilgamesh slaying the bull of heaven into the whole mess, it certainly was not monotheistic.
But I digress.
I would need to check RoP: Divine to see what it says about sin and virtue, but its really bad in RoP: Infernal. How demons are "without virtue", which apparently means moronic and cartoonish. Can't be patient, must be lazy, must have overly complicated plans, etc. That's cartoon villain.
There is just no way to provide complete, peremptory rules of behaviour for any kind of intelligent RPG character. RoP:I p.44ff is no exception in this. If used in an intentionally mechanistic way, it fails: independently of it describing demons in terms of missing virtues.
Well, your God isn't called divine, at least not by the text, if your God is faerie or magical or infernal. But these are just terms to distinguish four realms of power that have different systems associated with them. What your character calls God isn't enforced by the rules in any way. Do you want to worship a deity that is tied to what the game calls the divine realm? That's a (mostly) monotheistic and (mostly) benevolent one. There shouldn't be any mechanical problems with putting Calleach or Pan or Ra into that realm.
You feel that because the realm called the divine realm can do things the others can't, that makes it "right"? I disagree. I think it makes it powerful, yes, indeed much more powerful than the other realms. However, it says nothing about whether or not one who follows the realm is "correct" or "justified" or anything like that. It is a good reason to favor it over the others, but not proof that the others are "wrong" in any way.
My understanding is that the only rules for whether or not a religion is tied to what the game calls the divine realm are that it is at least partially monotheistic and somewhat benevolent. I don't remember seeing the Cult of Mithras explicitly tied to the divine realm in any published Fifth Edition material, but I would certainly meet authors or players halfway on that. Perhaps in the intervening years the cultists have become more "divine" and less "faerie" and are thereby more appropriately aligned to that realm? As far as the rules are concerned, it should take very little effort to apply the powers of the divine realm to any religion of the setting.
Rules note - a Divine aura that requires a congregation to maintain is known as a Dominion aura. One that does not require a congregation is called an Empyrean aura, and can appear in completely natural and wild places. They are described on RoP:D, pg. 12. So it's entirely possible that the aforementioned pagan COULD be offended at a Divine aura appearing during the spring floods, assuming there was a Divine purpose for doing so - in game mechanics, this would likely be something with a Divine might, such as powerful divine creature or a saint living nearby, a holy relic, location of a miracle, or even just a "holy place" - the Tree of Life, for example, has a Divine Aura.
A ravine in the wilderness: a Franciscan friar in holy contemplation interfering with a spring revel in honor of Potrimpos. Yes, that would be a subject for some heavy role playing. :mrgreen:
I also recall 'The Feast' from Tarkovsky's Andrei Rublev for some ideas.
Another interesting possibility occurs to me in terms of the idea of a Druidic Dominion aura that has been out of use for some time- if combined with the idea that past use in worship can cause a magical aura of 1 per century then a dominion aura from a druidic circle might fade to the point where it leaves a magic aura behind, leaving any magi who bear witness to such an event with numerous questions...
Do you refer to the brief summary of sins and virtues in medieval Christian philosophy in RoP:D p.76 right box? Why does that bug you? Nothing there is cast into rules, not even hinted at as generally applying in game. So where's the problem 
Perhaps in the intervening years the cultists have become more "divine" and less "faerie" and are thereby more appropriately aligned to that realm? As far as the rules are concerned, it should take very little effort to apply the powers of the divine realm to any religion of the setting.