Beware the evils of duality. Our world is not a simple matter of black and white, and neither should yours. And, when a character with such dualistic views is placed in a situation that tests those views, it gives the writer a deep well of potential conflict to draw on. Use the past. When the only information we have about the universe is that which happens within the story, the world will seem sterile and contrived.
Every fictional universe has a past, if only an implied one.
Also, remember that the past is different things to different people. When someone in a story has a different view of history than the reader does, the reader will gain some insight into that character's personality and culture. Even if none of these elements make it into the story, it will show if you've thought about them. Like history, it gives the impression that the universe as written extends beyond the pages of the story. Top of Page Make your world essential to your story.