One reason for our failure to save the earth, argues Neil Evernden, is our disagreement about what nature really is--how it works, what constitutes a risk to it, and even whether we ourselves are part of it. Nature is as much a social entity as a physical one. In addition to the physical resources to be harnessed and transformed, it consists of a domain of norms that may be called upon in defense of certain social ideals. In exploring the consequences...