Book excerpt: This important collection focuses on the nature and importance of biodiversity. The concept is clarified and its intrinsic and instrumental value are discussed. Even though the term biodiversity was invented in the 1980s to promote the cause of species conservation, discussions on biological diversity go back to Plato. There are many controversies surrounding biodiversity and a few of them are examined here: What is worthy of protection or restoration and what is the acceptable level of costs? Is it permissible to kill sentient animals to promote native populations? Can species be reintroduced if they have disappeared a long time ago? How should the responsibilities for biodiversity be shared? This book will be of interest to philosophers of science and biologists, but also to anyone interested in conservation and the environment.