The legacy that Charles Darwin has left us forever is his broad and abstract theories about evolution and natural selection, which he subjected to scrutiny in his writings using a vast amount of evidence from natural history. Mark Ridley uses the method of correspondences to show us how carefully Darwin worked when dealing with a problem, and how we can understand his arguments by first trying to discover the possible questions that Darwin posed to himself.

Mark Ridley focuses on excerpts from Darwin's two most important books, "On the Origin of Species" and "The Descent of Man". He also provides information on some lesser-known works of Darwin, which deal with very different topics, such as the origin of animals, earthworms, and human nature.