"This book is a comprehensive study of the ethics of killing in cases in which the metaphysical or moral status of the individual killed is uncertain or controversial. Among the beings whose status is questionable or marginal in this way are human embryos and fetuses, neonates, animals, anencephalic infants, human beings with severe, congenital, cognitive impairments, and human beings who have become severely demented or irreversibly comatose. ". "In an attempt to understand the moral status of these beings, Jeff McMahan develops and defends distinctive accounts of the nature of personal identity, the evaluation of death, and the wrongness of killing. He contends that the morality of killing is not unitary; rather, the principles that determine the morality of killing in marginal cases are different from those that govern the killing of persons who are self-conscious and rational. "--BOOK JACKET.