In this riveting and timely work, John P. Lizza presents the first comprehensive analysis of personhood and humanity in the context of defining death. Rejecting the common assumption that human or personal death is simply a biological phenomenon for biologists or physicians to define, Lizza argues that the definition of death is also a matter for metaphysical reflection, moral choice, and cultural acceptance. Lizza maintains that defining death remains problematic because basic ontological, ethical, and cultural issues have never been adequately addressed. Advances in life-sustaining technology and organ transplantation have led to revision of the legal definition of death. It is generally accepted that death occurs when all functions of the brain have ceased. However, legal and clinical cases involving postmortem pregnancy, individuals in permanent vegetative state, those with anencephaly, and those with severe dementia challenge the neurological criteria. Is “brain death” really death? Should the neurological criteria be expanded to include individuals in permanent vegetative state, with anencephaly, and those with severe dementia? What metaphysical, ethical, and cultural considerations are relevant to answering such questions? Although Lizza accepts a pluralistic approach to the legal definition of death, he proposes a nonreductive, substantive view in which persons are understood as “constituted by” human organisms. This view, he argues, provides the best account of human nature as biological, moral, and cultural and supports a consciousness-related formulation of death. Through an analysis of legal and clinical cases and a discussion of alternative concepts of personhood, Lizza casts greater light on the underlying themes of a complex debate.