Merchants of Despair: Radical Environmentalists, Criminal Pseudo-Scientists, and the Fatal Cult of Antihumanism, by Robert Zubrin (Encounter, 328 pp., $25.95) A ruling idea of the last two centuries has been materialism: the notion, as arch-materialist Daniel Dennett asserts, that “there is only one sort of stuff, namely matter—the physical stuff of physics, chemistry, and physiology—and the mind is somehow nothing but a physical phenomenon.” One consequence of this belief has been the rise of antihumanism—the stripping from people of their transcendent value and a reduction of them to mere things in the world to be studied, understood, reshaped—and ultimately...