unlike the story, which is the sum of the parts, a theme is a universal extraction from the parts. Like an orange, the story is the pulp, while the theme is the juice. Most successful novels have themes that rise like a halo from the book, but does not drive the novel. As such, themes are not generally part of the original process, but are grafted on after the substance of the work is finished or in revision. Novels that start with the theme generally sink like lead and stink like skunk. Nipping and tucking a theme into the work after the bread has risen lets the work breath and fills the reader with a sweet literary aroma.
Edward C. Patterson