Part 1 can be found here.
Part 1 covered OD&D - 2E (including Holmes, Mentzer and Moldvay). I started this way back in August. Things got busy with the kids going back to school. I finally have the time to wrap it up, so here it goes.
Third Edition gives us an interesting tidbit (PHB, pg 87), 3.5E has identical wording (PHB 102): "Standard characters are good or neutral, but not evil. Evil alignments are for villains and monsters." This is a new statement, not seen in previous editions. 3E also gives us some great baseline ideas for good and evil. (PHB, pg 88): "Good characters and creatures protect innocent life. Evil characters and creatures debase or destroy innocent life, whether for fun or profit."
Third Edition also tags an ideal onto each of the nine alignments: LG "Crusader," NG "Benefactor," CG "Rebel," LN "Judge," N "Undecided," CN "Free Spirit," LE "Dominator," NE "Malefactor," and CE "Destroyer." These tags seem misleading to me. For the first time, it feels as if an alignment is an absolute. LG's tag carries a religious overtone. N's tag makes them seem wishy-washy. Instead of describing the characters, these tags seem to limit the imagination.
Why does my N druid carry a tag of Undecided? Instead, I will take the CN tag of Free Spirit. That's more interesting for sure. My dwarven fighter isn't a "Crusader." I guess I will make him LN so he can "Judge" the evil of my enemies.
Third Edition does do some things very right with the alignment system too. At the end of each description, it gives a "best alignment" statement. Well, for good and neutral anyway. Evil alignments have a "most dangerous alignment" statement.
Overall, Third Edition does a good job of explaining how alignments behave in the world around them. The rules mention that people will not always follow their alignment to perfection, and that is to be expected.
Fourth Edition splits from the 9-point (and even the 3-point) alignment systems drastically. Instead we get a 5-point system: Good, Evil, Lawful Good, Chaotic Evil, and Unaligned. Alignment gets barely 3 columns in the 4E PHB (19-20). In this edition, the alignment system is not a guide for playing the characters, but instead seems to be a tool for the rules. "For the purpose of determining whether an effect functions on a character, someone of lawful good alignment is considered good . . . a lawful good character can use a magic item that is only usable by good aligned characters."
Fourth Edition may have done some things right with the alignments. I have never played the system. Regardless, the alignment system is not build off the previous versions of the game.
Fifth Edition returns to the 9-point alignment system. Again, alignment scores only a little over one-half of a page in the book (PHB, 122). But, even with the truncated text, there are a couple of important points that can be applied over all editions. "For many thinking creatures, alignment is a moral choice. . . According to myth the good aligned gods who created these races gave them free will to choose their moral paths . . ."
"The evil deities who created other races though, made those races to serve them. Those races have strong inborn tendencies that match the nature of their gods."
In addition, 5E keeps the unaligned tag. It is reserved for creatures incapable of making ethical or moral choices. Sharks are given as an example. An apex predator that lives to hunt, but cannot choose not to do so.
Each of the editions changed the way we look at alignments. Some do it better, some worse. But, alignment is a fundamental core of D&D and is a necessary part, regardless of era or rules set. Without alignment, moral decisions become boring. Demons and devils just become a different type of dragon. Kings become more two-dimensional. Alignment, like every other piece of the rules, is a tool. To often, it is disregarded in favor of simplicity. This is a detriment to players, the game and stories everywhere.
To be a great player or DM, the alignment system needs to be understood, if only so one can know when to disregard its interaction with the game.