What is the theme in Time's Eye by Arthur C. Clarke?

Time vs life is a theme in the story. In an effort to salvage what is believed to be of utmost importance, the Firstborn cause earth's timeline to be fragmented. They do so because they believe that while not human themselves, there is nothing in the universe that is more important than life itself. Having watched the universe since very early time began, they came to appreciate that life is the most precious of all things.