Charles Darwin's permanent legacy is his broad, abstract theories of evolution and natural selection, theories that he tested against an astonishing array of natural history evidence in his writing. Mark Ridley uses a question-and-answer approach to explain how Darwin carefully tackled problems, and shows here how the reader can understand Darwin's arguments by first working out which question Darwin had implicitly set himself to answer.

Ridley concentrates on understanding Darwin's most important books, On the Origin of Species and The Descent of Man, but he also examines a sample from one of Darwin's other works on the emotions, as one representative from Darwin's lesser-known works that ranged from flower pollination to coral reefs, from animal domestication to landscaping by earthworms.