This text analyzes what biodiversity represents to the biologists who operate in broader society on its behalf, drawing on interviews with the scientists most active today in the mission to preserve biodiversity, including Peter Raven, Thomas Lovejoy, Jane Lubchenco and Paul Ehrlich. The author explores how and why these biologists shaped the concept of biodiversity and promoted it to society at large - examining their definitions of biodiversity; their opinions about spirituality and its role in scientific work; the notion of biodiversity as something of intrinsic value; and their views on biophilia, E.O. Wilson's idea that humans are genetically predisposed to love nature. He also looks at the work of 20th-century forerunners of today's conservation biologists - Aldo Leopold, Charles S, Elton, Rachel Carson, David Ehrenfeld - and points out their contributions to the current debates. The book takes readers to Costa Rica, where a group of scientists is using biodiversity to remake nature and society. An extended section profiles the thoughts and work of E.O. Wilson.