Let me lay my cards on the table. If I were to give an award for the single best idea anyone ever had, I'd give it to Darwin, ahead of even Newton or Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning and purpose with the realm of space and time, cause and effect, mechanism and physical law. It is not just a wonderful idea. It is a dangerous idea.
Darwin's Dangerous Idea: Evolution and the Meaning of Life (ed. Simon and Schuster, 2014) - ISBN: 9781439126295