When philosophers address personal identity, they usually explore numerical identity: what are the criteria for a person's continuing existence? When non-philosophers address personal identity, they often have in mind narrative identity: Which characteristics of a particular person are salient to her self-conception? This book develops accounts of both senses of identity, arguing that both are normatively important, and is unique in its exploration of a range of issues in bioethics through the lens of identity. Defending a biological view of our (...) numerical identity and a framework for understanding narrative identity, DeGrazia investigates various issues for which considerations of identity prove critical: the definition of death; the authority of advance directives in cases of severe dementia; the use of enhancement technologies; prenatal genetic interventions; and certain types of reproductive choices. He demonstrates the power of personal identity theory to illuminate issues in bioethics as they bring philosophical theory to life. (shrink)

Brain transplants and the dicephalus (an organism just like us except that it has two cerebrums) are thought to support the position that we are essentially thinking creatures, not living organisms. I try to offset the first of these intuitions by responding to thought experiments Peter Unger devised to show that identity is what matters. I then try to motivate an interpretation of the alleged conjoined twins as really just one person cut off from himself by relying upon what I (...) take will be the reader's disagreement with Locke's conjecture that a dreaming Socrates and an awake Socrates are two distinct people. (shrink)