Pollution, deforestation, elimination of species, greenhouse gases and depletion of the ozone layer. These results of human activity are, as most people would agree, undesirable. But what is the value of the natural world that would be lost if the environment were destroyed or seriously degraded? This is the central question of environmental ethics and the focus of this book. It argues that to properly understand how and why nature can have value requires a radical revision of the way philosophy is understood and practised, and an equally radical restructuring of the concepts and categories upon which modern philosophy has been based.