Here James of Grognardia talks about D&D Alignment
Remember alignment started as labels for factions. Here are the good guys and they cheer you on. Here are the evil guys and you kill them.
However the labels (Law, Neutral, Chaos) combined with the description of the faction members (elves, dwarves, humans vs monsters lead by evil high priests) naturally lead to people attach philosophical ramification to these labels.
The culminated in the introduction of the second axis of good vs evil. Originally only five alignments but later expanded to the familiar nine.
This entire progression of alignment rules was logical at every step. However the end result was less than stellar. A system designed to for wargame factions was shoehorned as the moral philosophy of the D&D universe. Also it got wrapped up with describing the personality of the character.
Now I am not a fan of moral relativism. However I am also not a fan of alignment labels either. The last series of AD&D campaign I ran in the mid 80s jettisoned alignment. Instead which god you followed and which factions you belonged too was more important.
The various Detect Evil and Know Alignment spells were adapted to work with this or jettisoned.
All of this evolved into something similar to D&D 4th. You have a great muddled grey area involving many cultures and different creeds doing what people do over history. Then you have the Demons which represent the creatures that rejected creation and are the enemy of all life in my campaign. They are evil. Even the dark gods of my realm like Set and Kali will happily go hunting for demons.
This is similar to D&D 4th where you have Lawful Good, Good, and Neutral. With Chaotic Evil fighting all of them.
I do miss the personality aspects of Alignment. It was a good short hand for referee a random monster or NPCs. Perhaps a descriptive personality system would better for me and other referee. Perhaps something based on the four "humors".
On one axis you have Extrovert vs Introvert, on the other Labile vs Stable, of course Neutral. The extreme combination will give the four temperaments; Extrovert-Stable (sanguine), Introvert-Stable (phlegmatic), Extrovert-Labile (choleric), Introvert-Labile (melancholic). For our character you would have "nine" basic personalities. N, IN, EN, LN, SN, IS, IL, ES, EL. Combined with notes on what factions and gods will provide a good shorthand as to how to roleplay the character.