Psychology textbooks like to talk about the idea of “roles”: gender roles, professional roles, class roles, etc. This is merely one instance of the greater process of human understanding.
Premise: Reality is infinite and almost infinitely complex.
Premise: Human beings–and their brains/processing power–are finite.
Question: So how do humans manage to interact with and understand the world?
A human being takes a subset of reality, and creates a rule from it. A system of rules for a given topic becomes a model. A group of models is understood through a narrative. Our conception of the world, both physically ad intellectually, is comprised of a series of narratives.
Similarly, when we consider ourselves, there is a process of understanding–
Person -> Perceptions -> Roles -> Ideals -> Narratives -> Identity
–where “person” is a reality whose totality we cannot completely comprehend. When we consider others, we trade out the idea of Identity with the idea of a Label. Now, a person can have many labels and many identities depending on context.
This goes back to the premise that we cannot understand everything all at the same time.
It is possible to move from the Label/Identity layer down into narratives, roles, and perceptions. But no matter how low we go, we can never understand the totality, and this is where we run into the problem of false roles, false narratives, and false labels. The vast majority of our conceptions of other people are flawed, and the other person would probably disagree with a large portion of them. And so we have misunderstandings do to our inability to completely conceive of the totality of a person (or the world).
So, we take the facts we have and try to find what’s called a “best fit” case. When you graph trends in statistics, you draw a line through your data points that best approximates the average location of the points. The same is true when we judge others, no matter on what axis we are judging them. We look at our system of roles, ideas, and narratives, and try to find the set of them that most closely fits our perceptions of the person in question. Then, we construct our idea of their identity from that best fit. In this way, we warp (slightly or egregiously) the unknowable totality of reality as we experience it to fit a narrative. Because our system for understanding and interacting with the universe is only capable of so much, we reduce reality down to something it feels like our system can handle.
The reason that certain character archetypes and narrative trajectories are so popular is because they match the most easily understandable roles and narratives. Good vs. evil is easy for our simplified system to handle. It’s much harder to judge and therefore arrive at an “appropriate” emotional response to grey morality. Because humans and the cultural sea in which we swim impose a localized best “best fit” on our collective consciousness, as writers we can learn about these best fits and cleave to or subvert them for our own purposes in our writing. We can pick where to deviate in order to focus our attention and our chances of successfully getting across our meaning. Just as we can only handle a certain complexity in understanding reality, we are limited in our ability to deviate from the norm successfully. Thus the commonly re-quoted “You get one big lie” in regards to maintaining suspension of disbelief.