A young gaming friend asked on FB about alignment, and enforcing declared alignment. I think there's more than gaming here.
In the Dungeons & Dragons world, characters chose, or were assigned, a moral alignment. This consisted of two axes: Good-Neutral-Evil and Lawful-Neutral-Chaotic. I never much liked it. It has some function as a narrative and character development tool, but it always struck me as a milk-and-water evasion by secular people who couldn't abide the thought of thousands of Percivales and Frank Merriwethers populating their games, wanting more variety. Fair enough, but that's rather a false stereotype, innit? There are plenty of characters of moral ambiguity in Tolkien after all. So, not understanding good and evil, they came up with a clumsy way around it.
In all gaming there is a tension between narrative truth and real life truth. Go too deeply into a truth that is only game-contained and real people don't identify much anymore. This is why playing characters too many removes from humanness becomes less interesting rather than more. We don't really care to play intelligent rock-creatures or pure spirits for very long. On the other hand, it becomes a little silly to insist too much on realism when one is playing a dark elf from the underworld who is mounted on a flying lizard.
Still, the narrative attraction is often right at this pivot point of where do loyalties lie? Or the courage to stand up for larger values. Or trying to understand deeper truths that are only partly illustrated by the local truths the character grew up with in the Shire or Redwall. Good and evil often are the story, so understanding what they really are in humans must have something to do with how it will play out successfully in a game.
We have to first realise that everyone believes they are on the side of good. The number of people who actively seek evil, even among those who seek to shock us, is vanishingly small. People who claim to be bad are usually posers who are really saying "I'm a lot of fun. I seek pleasure. I have the courage to challenge norms. I don't care what those icky people think." All of these they define as good. One can sometimes find those who reject most ideas of goodness and rather openly seek power, so that cruelty and dishonesty are considered tools of the trade. They might actively enjoy taking advantage of others, who they see as weak or foolish, but really "It's business." This certainly is evil - it is the mentality of criminals - but even these do not worship evil gods because they are evil but because they believe it's all a crock and they side with power.
The standard human morality is the narrow altruism of "What is good for my tribe/clan/class" held in tension with "What is good for me within my group?" Law vs. chaos doesn't much enter into it: it's all law vs. selfishness.
So too in literature. The solo quest is actually not quite what heroic literature is about. The hero starts as a leader of many retainers, all of whom are gradually destroyed, leaving him to quest on - Beowulf, Ulysses, Roland. We don't see that so clearly with our American, Daniel Boone or Jack London eyes, and see the individual hero. Not so in origins - the reality of the clan is still there.
We rationalise stealing from Oppressors or Usurpers or Corporate Interests because they aren't our group. So it isn't really evil, nay nay. They are evil, we only seek to even the score. Trying to stuff that into the traditional D&D alignments is just clumsy. Gygax and Arneson weren't moral philosophers, they were idea-guys who took a guess how human morality, and thus literary morality, and thus gaming morality really works. They guessed wrong, in a very late 1960's way that thought Druids were neutral and law was vaguely Nixonian. Gaming alignment doesn't describe anything real in the character.