There is really only one question for human beings that matters. What, if any, is the purpose of existence, and what are we here for? It is a question that has underlain religious conviction and philosophic inquiry throughout human history, and to which scientific rationalism in recent centuries has added some important insights. It highlights two contesting views of the nature of reality: is there a purpose behind the universe, or is it a mechanistic universe driven by blind natural forces? Or is there indeed some alternative third explanation? What is one to believe about the ultimates of human existence?