My view is that much of the dispute/incoherence in relation to alignment comes from treating the
good alignment as not necessarily good. This produces paradoxical convictions, like
Doing such-and-such is not good but is what ought to be done.
I think that if the word
good (and its opposite,
evil) is taken literally in the alignment context then much of the problems go away. Good people are those who are committed to, and/or who pursue (alignment is an amorphous mix of purpose and deed), good things. In his PHB and DMG Gygax is (deliberately, I think) very inclusive here - he includes as
good upholding rights, and pursuing valuable things like truth, life and beauty, and also pursuing the greatest happiness of the greatest number.
Conversely, someone is
evil if s/he is indifferent to any of these sorts of constraints and just does whatever s/he wants to serve his/her immediate desires for personal satisfaction and power.
Law and
chaos are, then,
means rather than
ends. Lawful good people think that the best way to pursue the good is via organisation and social structure. The chaotic good think individual self-realisation does a better job here, worrying that social structures tend to produce evil outcomes by creating opportunities and temptations to abuse power and subordinate others' interests.
Lawful evils agree with the chaotic good about the means-end relationship but because they're evil they
embrace it and pursue organisation. Conversely, the chaotic evil agree with the lawful good that organisation tends to block selfishness and foster widespread wellbeing - hence they oppose organisation and sociality!
On this conception, the
lawful neutral are not good - obviously - but are not fully evil, because they don't just do whatever they want. Likewise the chaotic neutral. In both cases, though, a means is treated as an end in itself and "fetishised" as worth pursuing on its own account. Hence why they are not good.
So this is pretty much the opposite view from
@doctorbadwolf's. But I think is consistent with Gygax's treatment of alignment. What it
doesn't fit well with is the classic D&D treatment of the outer planes, especially in Planescape. Because these tend to treat the means-end question as unimportant, and to assume that both law
and chaos can yield good (qv The Seven Heavens and Olympus). I think this is incoherent - if both law and chaos can yield good, then what do the LG and CG even disagree about? It would be no different from Dwarves preferring to live in the mountains and elves preferring to live in the forests.
But unfortunately that Planescape-approach now seems to predominate, in my view to the detriment of the utility of the alignment system as anything but a loose system of personality descriptors.