QuoteI also had a long-standing Call of Cthulhu character who went to being a devout Catholic, and considered all the anti-Christian stuff he was seeing to be a test of people's faith in the End Times.

Nice. My 30's Polish priest considered monstrosities (great snake with human head, and this bhakiye something space vywern) as ante-dilluvian monstrosities that were created by ancients (presumably Nephilims) and should still be treated as natural although monstrous beasts. You know... like pitbulls.

QuoteI remember watching Vikings and noticing that Norse women seemed to have more rights - but at the same time they seemed to be more accepting of murder, robbery, torture, human sacrifice and illiteracy, so I was always rooting for the Christians (I know this is beside the point but I think worth mentioning).

I'd note that in Christian countries ability of women to inherit property were vastly different between various people and were mostly based on local traditions not on Christianity.
Though Hebrew custom presented in Bible generally implies firstborn son should get major part of inheritance after father, and care about widow-mother as his father.
But it's not enforced in Christianity as moral order.

QuoteAs for the reason I'm not sure that starting with cosmology always yields a definition of good and evil is because the rules for morals and ethical codes do not necessarily apply to divine beings.

I mean considering D&D tradition of applying alignment to good, and having many gods of one alignment it always seems cleared to me that deities are below Cosmic Force of Alignment and if they fuck around they can find out just like wanton paladins. Hey why my divine fortress was removed to Gehenna, WTF?

QuoteChristianity's great moral innovations were threefold:
1) It was the first moral system to emphasize forgiveness of sins and enemies as a prerequisite for personal salvation;
2) It was the first system to truly universalize the moral status of all men as brothers in spirit, trumping all worldly considerations of rank, status, wealth or background.  It is not an accident that while slavery coexisted with Christianity for many centuries, it was only people descended from and driven by the Christian philosophical tradition who finally and successfully abolished slavery.
3) It was the first system to completely abolish systematic material sacrifice as a method of interacting with the Divine, emphasizing that God could not be bargained with or bought off as the pagans, or even the Jewish tradition of the Law, held could be the case.

I have mixed feeling about this.
Point 1 is I think spot on, at least I never heard about something simmilar.
Point 2 - while Christianity indeed preached brotherhood of spirit, actual social egalitarism is done by Englightement, enemies of Christendom - because Christianity also supported social hierarchies as Divine Orders, and see no contradiction between their existence and brotherhood. Just like there was hierarchy in early Church with Apostoles leading rest. In this vein one could see Englightement as authistic leading of one Christianity aspect too maximum while abandoning others. And IIRC there were previous antislaving religions - like zoroastrianism in Persia. I agree that Englightement would probably not developed without Christianity as it is clearly twisted form of cherry picked Christian values. (And of course Englightementers replaced slavery wide world wide colonialism so...)
Point 3. Of course not. All Christianity is based on Sacrifice as interacting with Divine. I'd even say The Sacrifice. And plenty Fathers described it precisely with bargain/bought off logic.
This intuition among pagan people was top notch correct. Sacrifice was necessary. The problem was of course 99,9999999% sacrifices in history were not in any way valuable for side they tried to bargain with.

QuoteSo, the answer to this first principle of religion is probably the most important choice you can make in your RPG religions.  Is there a Universal Good, that even gods can be judged by?  Or is Good defined by the declarations of the deity that you follow?  This is especially important in a world where gods might be physically present and directly interact with mortals.  It is interesting to note that, by explicitly categorizing deities in D&D by alignment, Gygax, et al., implicitly reflected their post-Enlightenment cultural beliefs that there is a universal Good and Evil by which those gods can be judged.

I mean yes and not.
Christianity is strictly monotheist and God is Absolute Source of well Everything. Including Good. There is no escaping it. There is no place of primordial Good preceding Triune God. In Enlightement eyes maybe there is that's why they love judge God for killing firstborns of Egypt or wrecking Caanaan. But that's not Christian perspective. In Christianity divine hidden ousia, essence precedes in logical fashion any actions between God and Creation (energies in Greek theology) - and morality is basically whole in energy departament. So yes very clearly Christianity stands in "things are Good by God decrees" but also due to logocentrism - "God decrees are not whimsical but flowing from his unfathomable essence and therefore they cannot be changed in any fundamental way". But that still very different situation to Enlightened notion that you can judge God. You cannot. You may judge Torm, Hextor or Tempus - you cannot judge Absolute - unless you wanna do fool out of yourself.

Now D&D gods are just very powerful beings. You can kill them after all. If there is supreme Absolute God - he is  not intereacting with PCs. So yes in this case Absolute Good (and also Absolut Evil which is Equal to Good - also extremely different perspective from both Christianity and Englightement) precedes Gods.

But also quite frankly maybe by accident, not by plan, maybe just as in-game adjustment Gygax created cosmology that does not really fit any real world one. Gygaxian cosmology is unique and utterly fantastical.

QuoteMy favorite version of leftardism on the Bible is when they say Sodom and Gomorrah were nuked because they were not hospitable to visitors and that's why, not the buttsex or clamdipping.

I mean while this is used by Christian left as method to diminish graveness of homosexual acts, there are good in Bible reason to consider Sodom faith to be more complex than just buttsex thing.
First of all we have open and clear breaking of hospitality - which is very accursed thing in ancient morality - let's remember simmilar case though with woman led to civil war with Beniaminites withing ancient Israel. And Ezekiel speak about Sodom: ""This was the guilt of your sister Sodom: she and her daughters had pride, excess of food, and prosperous ease, but did not aid the poor and needy. They were haughty, and did abominable things before me; therefore I removed them when I saw it.""

So generally holistic perspective is quite clear - Sodom was not destroyed for some one specific incident but for being immoral assholes on every possible field. And the bargain between Abraham and God, when Abraham tries and fail to find 10 just Sodomites kinda confirm the rot on many possible levels.

QuoteLikewise, in Hinduism, the mythic figures would often commit sins and be punished for their sins, as in the Mahabharata. Even the gods have their karma and dharma, which are defined by the universe. I'm not too familiar with it, but I think the Vedic texts describe sins, but don't phrase them as "god commands this" but simply as "this is wrong".

TBH Hebrew word for sin, later translated literally to Greek meant "missing the mark".

QuoteThis gets back to the point I made earlier.  It was entirely predictable that such a discussion would arise.  If this were to come up in one of my gaming groups, the Baptist player and I would say that this is definitely in "thou shalt not" territory.  The Methodist would say its fine.  The two nominal, unenthusiastic Christians would say "who cares?"  I would rather not have this discussion at my gaming table; it could take a lot of time and has the potential for creating acrimony between friends.  There are two ways to avoid this, first as DM I could make sure religious issues never come up in game.  But in this case why am I bothering to include a religion in the first place?  The other way is to create a well defined fictional religion that none of the players have a personal investment in.  That's my preference.

Or just make them all play Coptic Orthodox and follow their tenants (which despite being Christian will probably be somehow alien to all those protsy lot)