These two books make good companions, and it is instructive to read them side by side. In doing so, the reader can reflect upon a central challenge to conservation science, and to the societies within which it carries out its business. Conservation biology, like some other fields of biology, not only aims to generate a coherent account of the phenomena under its purview, but does so for a practical purpose: conservation, however construed. In recent years, the construals center more or less on the protection of biological diversity. In order for this purpose to be achieved, science is not enough. Government action and social engagement are needed, and these must rest to a certain extent not upon data or ”how things are,” nor even on theory or ”how things work and why,” but on a vision of how things are supposed to be. This is at bottom an act of imagination, more or less informed by scientific understanding.