Writing to find out

Yesterday I went to a seminar about 'Science in Fiction' where Maggie Gee was in discussion with Philip Pullman, Brian Aldiss and John Carey. At one point Philip Pullman said, 'If you knew what was going to happen when you started writing, you'd go mad. You write to find out.' Everyone wholeheartedly agreed, which surprised me greatly. I imagined that writers all work out the plot completely before they start. How liberating to think you don't!