you've already said morality is too complex to be compartmentalized and categorized as it is in D&D... so how can they ever encompass real world meanings? They draw on real world meanings as a basis in most people's campaign settings because it's easy and provides a point of reference for everyone... but the specifics are (usually) determined by what the creator of the campaign setting determines they are.
<snip>
LG is connected to values and ideals, which have a real world basis (for the majority of campaigns) but what the specifics of those ideals are... is usually determined by the creator of the campaign world, since like the designation of a PC as a players territory... cosmology is usually the DM's.
That process of "specification" is what I am referring to as the fictional/fantasy morality. The more weight that is given, the less genuine moral heft a paladin (or cleric, or druid, etc) has. Conversely, the less weight the GM's specification is given, and the more emphasis placed on real world values and ideals, then the weaker the argument that the GM should adjudicate because s/he is the one who decides the ingame morality.
My basic point is that we can't have it both ways: both that characters like paladins and druids have thematic heft because they touch on real world values and ideals,
and that the morality of the gameworld isn't real morality but a fictional morality stipulated and adjudicated by the GM.
Well, then the player's take on mercy, at least. The god probably doesn't think it is merciful (in your example). This has no bearing on whether or not the players can explore mercy, though.
No. But it does entail that the PCs, in the game, might conclude that the god of mercy doesn't really understand mercy. Which was my self-delusion point above. A fantasy world in which it is coherent to suppose that the god of mercy is deluded about what mercy really requires is, in my view, not one which has room for the paladin ideal. It is essentially modernist - as I said above, even nihilistic or cynical (as REH's Conan tends to be).
About the time is gives descriptions of Good, Evil, Lawful, Chaotic, and Neutral, it's set up a fictional morality system.
I regard the d20 SRD as trying to give an account of good that is not fictional. Gygax did the same in AD&D, when he referred to both Benthamite and human rights accounts of goodness in his definitions of the good alignment.
The GM is not the moral arbiter for the table any more than anybody else at the table is. But unlike the real world as far as we can tell, the morality your character exhibits has a real objective effect in the game world and those things need a referee for arbitration.
These two sentences strike me as contradicting one another.
If the GM - the referee - is arbitrating what counts as compliance with ingame moral requirements, then either (i) those ingame moral requirements are fantasy/fiction morality, or (ii) those ingame moral requirements are expressive of real morality. If the latter - which I thought was what you said upthread - then the GM, by arbitrating the ingame requirements of real moral values,
is acting as the moral arbiter for the table.