At a time when technology can sustain marginal life, it is ever more important to understand what constitutes a person. What are the medical, ethical, moral, mental, legal, and philosophical criteria that determine protectable human life? Following immediately on the publication of his highly praised book Choosing Who's to Live, James Walters addresses with depth and wisdom another ambitious and complicated matter: determining the nature of personhood. By providing a much-needed religious/philosophical context for the discussion--examining contemporary thinking on just what constitutes valuable life--Walters broadens his inquiry beyond the human to include other animals and deals with the phenomenon of anencephalic infants, those who are born without higher brains. Searching for a measurable and humane standard of personhood, Walters looks at the current definition of it and declares it inadequate--offering instead the idea of proximate personhood, with criteria for helping to determine which individuals possess a unique claim to life.