So I was reading wikipedia the other day, looking for something, and stumbled on this>
Psychoanalytic theorists believe that human behavior is deterministic. It is governed by irrational forces, and the unconscious, as well instinctual and biological drives. Due to this deterministic nature, psychoanalytic theorists do not believe in free will.
It's from the wikipedia entry on "psychoanalytic theory," which strangely enough I've never read. Freud has a bad reputation these days, but this one bit "human behavior is deterministic" is a gem and the entire theory behind character arc.
Characters react according to their backstory, which makes them deterministic, which makes stories causal, which--yeah, well anyway. I like it and wrote it down on a sticky.