People who say that the good/evil axis is simplistic or vague IMO misunderstand the purpose of alignment as well as the difficulties of the law/chaos axis. Alignment is not meant to represent the human personality. Nor is it meant to encompass all human worldviews. Nor is it meant to encompass the whole of the allegiances and loyalties of characters or nations. Instead, as I understand it, it is meant to define characters' standing in relation to the moral and supernatural orders.
Just because two characters are good doesn't mean that they will see eye to eye or even that they'll join together and fight against the bad guy. A good king might send his neutral Marquis and a good duke to fight a neighboring kingdom whose evil Emperor might dispatch his armies under the leadership of a good count. The good count might follow the evil king out of respect for the law of succession/divine right/rule of law or because of a pragmatic calculation that any realistic alternative is even worse. He would probably also defend his land (and his liege's) even against the good invaders out of loyalty to the throne or tradition or simple love for his country and a desire to see it ruled by natives who understand it rather than foreigners. When he meets the Duke on the field of battle, odds are good that only one will walk away even though both are good and respect each other and, under different circumstances might have been friends. The romantic myths about Richard the Lionhearted and Saladin during the crusades (although probably not the reality) illustrate this. As does, IIRC, the real life (or at least widely reported as true) example of the friendship of Jesse Owens and Luz Long, the german sprinter at the 1936 Olympics--even though less than four years later, they both served in armies on the opposite sides of World War II.
Alignment is what is supposed describe the difference in how God or the gods would view Luz Long and Jesse Owens and Goerring. It's not meant to tell us Jesse Owens' views on racial integration (although it undoubtedly plays a part in that) or whether or not Luz Long would be willing to serve in the Wehrmacht (although it also plays a part in that).
There's nothing necessarily simplistic about saying that there are good and evil people--in fact, it seems to me to be more simplistic to adopt a shallow relativism that is unable to see real differences in human character.
And responding to a few other posters, Law is said represent absolute control and unmoving, rigid order and chaos to represent constant change (a rather nonsensical understanding when it's applied to physical reality--as it often is when it sullies fantasy literature weith its presence--since the theoretical position of maximum entropy (generally connected with chaos) is actually (as I understand it) quite analogous to motionlessness (generally connected with Law) and real states of maximum order (generally associated with Law) generally involve motion and change (generally associated with Chaos); the decay of a planet's orbit increases entropy and decreases order even though it is a step in the motion towards the elimination of change). Neither of these, however are desired by much of anyone in the world (Fascists talk about freedom in work and order and anarchists dream that people will naturally find a justly ordered society if formal power structures just stopped interfering--they certainly don't see their movements in the terms that Law/Chaos proponents do). In that case, where everyone's professed desire is arguably neutral, there's not much point in having a Law/Chaos axis at all unless it's to claim that the cosmos and spiritual forces of the world are alien, incomprehensible, and utterly uninterested in the good of humanity (which is what I understood to be the worldview of the Elric books when I read them--or more properly I read one, so I may be mischaracterizing them).
And, as to Law/Chaos representing the "ethical" and Good/Evil representing "moral" as another poster put it, what on earth are you smoking? Moral and ethical are used pretty much interchangably--even in philosophical circles, moral theory falls under the field of "ethics." If you wish to create a new distinction not recognized in normal or philosophical English, that's fine but you'll need to clearly define your terms with words that, unlike Law and Chaos have clearly understood meanings.
MerakSpielman said:
Or Chaos-theory mathematicians?
seriously though...
I think just a Good-Neutral-Evil system is too vague. Same with the OD&D Lawful-Neutral-Chaotic system. Combining the two makes a much more complex system that encompasses a greater number of worldviews.
But still, a lot of character concepts are very difficult to fit into a specific alignment, so we just pick one that's kind of close and move on with our lives.
In the rules as written, alignment is a total absolute. It is determinable via spells and abilities. Different weapons do different damage based on your alignment. It is a tried and true FACT that all creatures in the multiverse can be pidgeonholed into one of nine categories.
I don't think we can do away with any particular axis on the alignment grid - it would trivialize the shades of gray we all know exist. We could add MORE axes, to make the system more realistic, but that would get pretty cumbersome pretty fast. We could do away with alignment entirely, but then entire chunks of the game go away.
I dunno. I'm done rambling now.