In The Origin of Species (1859) Darwin challenged many of the most deeply-held beliefs of the Western world. Arguing for a material, not divine, origin of species, he showed that new species are achieved by "natural selection." The Origin communicates the enthusiasm of original thinking in an open, descriptive style, and Darwin's emphasis on the value of diversity speaks more strongly now than ever. As well as a stimulating introduction and detailed notes, this edition offers a register of the many writers referred to by Darwin in the text.