Theologian Gregory A. Boyd, in his book God of the Possible, discusses the thesis that the future is partly fixed and partly open even to God because the details are unfolding with the participation of free-will agents - i.e. human beings.
"If you give your characters free will they will grow in ways you never anticipated, and they will take the story places you could not have predicted, raising themes you might or might not have intended to explore. Characters shape events; events illuminate the characters. The people in a story begin as seeds, become buds, and blossom in ways that surprise the author, precisely as real people frequently surprise him with their intentions and capacities." (Relentless by Dean Koontz - spoken by the narrator)