You mean you build your characters according to the story, not the story around the characters?
Er... Good question!
The honest answer is 'it depends'. Most supporting characters, probably yes. And that can be dangerous. Characters need their own life. Where does that life come from? It has to come from yourself. You have to be able to imagine yourself acting like that, even if in real life you never would.
You are a Christian. How has this influenced you?
It's the other way around. The things that prompt me to write about moral confusion, duty and sacrifice also prompt me to be a Christian. What tempts us? What is the Fall like? That's why my books resonate with these ideas. But I don't write to persuade. I ask the questions that interest me.
What's the next book about?
It's set, oh, about fifty years in the future on Triton, the moon of Neptune. That's roughly four billion kilometres away, very cold, and as remote and hostile as you can get. Once you're there, you're there for life. So what would it be like? And what would we be like, to go there?