Few neuroscientists today would defend Cartesian dualism -- the idea that mind and body are separate -- but Damasio takes one more leap: Not only are philosophers wrong to separate brain and body, but psychology's separation of reason from emotion is also wrong. Most neuroscientists agree that what we call the mind reflects the functions of the nervous system -- in short, crudely speaking, the body. Modern science, however, has transferred the old mind-body split into a brain-body dichotomy in which the brain occupies a hierarchically privileged place. But Damasio (Neurology/Univ. of Iowa College of Medicine) democratizes the relationship between brain and body; he posits a powerful interdependence in which our physical experience of the world around us is central to the creation of our sense of self, and colors our behavior. His persuasive argument begins with Phineas Gage, a 19th-century railway worker who suffered brain damage when an iron rod shot through his head like a missile, destroying his left eye and parts of his frontal lobes. The result was not a loss of speech or memory but profound personality and emotional changes and an inability to make rational judgments about the present and future. Damasio and his wife, Hanna, have studied patients with similar frontal-lobe damage and similar effects: IQ, memory, and language are intact, but there is a lack of feeling and an inability to put current events in context and make future judgments. These points are eloquently expressed, along with the anatomical/physiological evidence linking the frontal cortices with sensory-motor areas and emotional networks that feed forward and backward from the body surface and internal organs. Damasio is the first to admit that he cannot prove all he says. In the meantime, one can read with pleasure and share the excitement of a neuroscientist who sees that in the union of the many parts of the human brain lies its strength.