This is part of how PS resembles the real world in its conflicts. No one can tell you what you "ought" to do with any true authority. It is up to the player to determine what they feel is right and wrong, based on the goals that they set for the multiverse via their character.
The problem with this claim is that it is objectively false and contrary to the rules of Planescape.
Planescape is a setting in which the Great Wheel cosmology is objectively mechanically privileged, as I have shown earlier and you have accepted. Other maps of the universe may have usefulness in the same way that socio-political maps are useful, but the Great Wheel is a geographic as well as a political map.
Now Kamikaze Midget's Planescape might not have the Great Wheel as central to and objectively mechanically privileged. But most of the time we aren't talking about Kamikaze Midget's Planescape
. We are talking about the one written by Zeb Cook
and contained in various sourcebooks. The Great Wheel, Good vs Evil, and Law vs Chaos are woven into Planescape cosmology in the same way they are in most other 2E settings.
Indeed, as written, I would go so far as to say that the 3E Forgotten Realms has a cosmology that's less bound up in externally defined Good and Evil than Planescape does. If you want a D&D setting without cosmological good and evil then Eberron leaves Planescape in the dust.
What Planescape does as written (rather than as played by Kamikaze Midget) is different, and subtle and interesting in its own right. Sigil is Rick's Casino. It's the football match in the middle of WWI. It's Switzerland in the middle of WWII. And is backed up by someone who is powerful enough to upset any form of balance that currently exists. So even in the middle of a great cosmological war
people can find their own factions. But what it does not do is negate that cosmological war.
Further for high level Planeswalkers it asks a different and no less interesting question. "You can't stop the conflict but you can realign it. How would you do so?" This in no sense negates the prior cosmic struggle.
So, for me, when someone gets to the point of telling me to go read academic journals to continue a casual message-board debate, I take it as a simple admission that the counterpoint cannot possibly be understood simply by a person with no prior specialization, and so the "functional" part comes into play. A moral code only accessible to obscure specialists and deadened with jargon isn't of much functional use (at the very least, you get the tl;dr reactions folks in the thread are articulating).
The problem here is that you are extending from one person to all. I have no formal training in analytic philosophy or ethics but have no problem understanding any of [MENTION=42582]pemerton[/MENTION]'s posts. So You are simply wrong that it "cannot possibly be understood simply by a person with no prior specialization". It can because it has been. It just can't by everyone
So it doesn't actually help people in general to answer moral questions. Which means that people trying to answer moral questions in the Real World still must struggle with functional subjectivity. Which is the kind of mindset that PS is made to evoke. And so that mindset is not unthinkably alien, even to those who believe in some objectively real morality.
And this is again Kamikaze Midget's Planescape not Planescape As Written.
As written there is objective good and objective evil. And The Great Wheel. Planescape isn't the shades-of-grey of Eberron however much you would like it to be so.
But indeed the mindset of Planescape is not unthinkably alien especially to those who believe in some objectively real morality. Planescape is much more interesting than that; shades of grey settings outnumber those with objective morality by at least an order of magnitude. Planescape is, when you get into the thematics, a setting about losing faith
. The textbook introduction to Planescape is with a party starting from the Prime Material - and that's where the thematics are strongest, just as Ravenloft is far more intense for PCs that didn't start there. Where the Gods have been a fact of life, and Good and Evil are objectively defined by those very Gods. And suddenly they find themselves in Planescape, somewhere the Gods have no power
and the war does not hold. That cosmological and spiritual war that was a fact of life? It's still out there. But there's no reason it needs to be. And if you free yourself sufficiently you might be able to change or end it. There are still powerful entities who can and do say what good and evil are. But you might (and I mean might) be able to take control of that. And there are all sorts of groups who are offering you ideologies to claim as your own now that the Gods aren't in a position to define them.