Occasionally in fiction, we meet two characters who seem fated to fight. Not because one is good and the other evil; in fact, each considers themselves to be good. They are doing the best they can to live according to whatever their moral code is, and it is rare for anyone to ask more of a person than that.
It’s when there are differences in their moral codes, worldviews, or philosophies that problems between the characters arise. The differences don’t even have to be all that big.
Take Valjean and Javert from the musical Les Miserables (Someday I might read the book, but not today). Both are devout Christians. Yet they spend the entirety of their time on stage together butting heads. Why? They ascribe to the same basic beliefs, even come from similarly disadvantaged backgrounds.
The difference is in their understandings of one element of Christian theology: justice and mercy.
Justice requires that when a law is broken, a consequence follows. It cares little for circumstances or regrets, only that the lawbreaker is punished. This is Javert’s lens for understanding the world, the reason he became a lawman.
Mercy takes circumstances and regrets into account, giving the lawbreaker a chance to do better. In the New Testament, Jesus used mercy frequently when dealing with those who the law had labeled sinners. Valjean sees mercy as being the more important of the two.
Both are essential to Christian doctrine, but which is emphasized more depends on which branch of Christianity is talking.
According to Javert’s understanding, Valjean is a lawbreaker and so must be punished. According to Valjean’s understanding, the law has already taken too much from him for him to build a decent life unless he-you guessed it–breaks more laws, and so he is justified in evading the law. Is either entirely right? Who knows, but since Valjean is the hero we tend to consider him to be more correct than his counterpart.
Their roles get reversed near the end of the show, but not their individual beliefs–Valjean becomes the law enforcer of the fledgling rebellion, and Javert the condemned. Justice and the rebellion’s law both say that Javert must die. After all, he has been interfering (unjustly, to the perspective of the rebellion) in Valjean’s life for years.
Valjean, however, still believes in mercy, and so he lets Javert go. Javert was not expecting this. In fact, he sings a dramatic song about how unexpected this was according to his worldview, and how now he thinks perhaps the criminal Valjean is a better man than him.
(I should point out here that suicide, such as Javert commits at the end of aforementioned dramatic song, is not a healthy way to react to your entire worldview being upended. Get a haircut. Change your major. Don’t die, please.)
That ends the two of them fighting, but Valjean has learned that his past breaking of the law, however necessary for survival it was, is going to catch up to him, because that is what justice does. He worries it will affect his daughter’s marriage, so he leaves. And then he dies too, because this is a really sad musical.
These two characters butting heads over the ancient argument of justice or mercy is only a part of a musical full of characters and intersecting plot lines, but it is the part that stands out most vividly to me. In a better world, Valjean and Javert might have been friends, but in the world of this story, each represents what the other hates most.
Not all opposing characters will clash so dramatically over such small differences in beliefs, but we writers can still use such circumstances to add interest to our stories. In Fantastic Beasts and Where to Find Them, Newt clashes with every other character because his way of seeing his creatures and the way others see them are so incompatible. In Ender’s Game, Peter and Valentine clash because their priorities are so different, though they work together anyways, and the humans and aliens are fighting because neither species thinks the others’ way of expressing sentience is real.
And, of course, we see real people fighting over tiny or not-so-tiny differences in worldview or circumstances all the time. Hopefully, we can get such arguments properly represented in our own stories.