I've talked about backstory before and how a character's past will inform their motives (why they do what they do) as well as their attitudes (how they respond to the people and events around them), but their past also plays a huge role in shaping their moral compass (or moral code).
What is a moral compass?
This is the code (or guiding principles) by which your character lives (the code which explains their motives and attitudes).
A character will use their moral compass to determine what is right and what is wrong and how they will behave in certain situations.
Though stealing is considered wrong, Character A has no problem robbing from the rich to give to the poor.
Though killing is considered wrong, Character B has no qualms about avenging the death of a loved one.
Though they may be a pacifist, Character C might draw the line when someone weaker is being bullied, stepping in to take care of the situation.
Why?
Well, let's look into their past.
Maybe Character A watched a corrupt billionaire run a company into the ground, ruining her father's livelihood and depleting his retirement savings/pension. So when she stumbles across a hole in the operating software of this billionaire's new company, she sees a chance to make things right. Would she steal if it were any other situation? Probably not, but according to her moral compass, stealing is okay if the victim deserves it.
Maybe Character B lost a parent to a dark lord. When the dark lord returns, he seizes his opportunity. He's no murderer, but how could he pass up the chance to finally even the score?
Maybe Character C was severely bullied growing up. When he sees a kid being terrorized in an alley, he decides to step in. He doesn't go around beating people up for no reason, but his moral compass is set to help those who can't help themselves.
There are reasons why we do the things we do. Sometimes we operate consciously, sometimes it's unconscious, but it always makes sense in relation to our past experiences.
The same applies to our characters: their behavior should make sense in relation to who they are and what they've been through, whether or not those events are fully explored on the page. (Some parts of the backstory are just for the author, after all.)
This isn't to say that a character can't act in opposition to their core values; in fact, this is a great way to show some contradiction and depth.
What if Character A sets out to take everything from that billionaire, but, at the last minute, has a change of heart?
What if your character is vehemently opposed to lying, but witnesses something she is forced to downplay or keep a secret?
What if your character's moral compass swings toward selfishness as a form of self-preservation when he stumbles across a dog in need of a home?
No matter what your character decides to do in any given situation--whether they are acting in accordance with their moral compass or not and whether this is part of the arc that will change them or otherwise--the behavior still needs to make sense based on what we know about them.
Your character's backstory will shape their moral compass.
Know their history, their values, and why they do what they do, but be sure to leave a little room for them to surprise you.
Be Brilliant!
~Katie~