Once Phineas Gage in 1848 recovered from the horrific brain damage that resulted from a three-foot tamping iron being driven through his anterior lobes, his friends were known to remark that "Gage was no longer Gage." A medical curiosity, Gage's story is generally regarded as the first fully detailed example of personality change resulting from brain injury. But what did that statement mean? Should Gage have been considered to be the same person he once was? Or a different entity, having a different sense of self and a different "personhood"? Such questioning about the meaning of personal identity may seem foreign to psychiatric clinicians and a humanistic perspective, but the technical definition of what it means to be a person and to have a personal identity is central to modern philosophical discourse on morality and responsibility. This book is the result of a symposium organized by the Johns Hopkins Berman Institute of Bioethics that brought together three prominent philosophers (Marya Schechtman, Carol Rovane, and John Perry) and two neuroscientists (Michael Gazzaniga and Samuel Barondes) and asked them to consider four case studies in which personal identity was affected by biologic circumstance; the cases chosen included individuals with Alzheimer's disease and frontotemporal dementia, steroid psychosis, and Parkinson's disease treated with deep brain stimulation. The end result, perhaps more surprising to the editors than to the reader, is a relative lack of consensus on the key issues—on who is a person and who is not, on the value of empirical versus conceptual methods, on the importance of conscious versus unconscious motivation, and on the value of physical criteria in assessing psychological capacities. One is reminded of the toast "the Lowells speak only to the Cabots and the Cabots speak only to God"; whether philosophers or neuroscientists are more representative of Lowells or Cabots is a debatable point. The chapter "How Philosophers Thinkâ¦" by Tumulty is the book's most succinct synopsis of variant approaches to the key questions and their complications, esoteric issues of identity made real through analogies to Coke cans and genetically transformed enemies of James Bond in Die Another Day. There is general agreement in both camps that personal identity can be best characterized by an ability to express a self narrative that endorses the concept of "self" and that strives for consistency, rationality, and intentionality. But at the end of the day, the operational utility of this definition remains a dividing point. The editors suggest that philosophy and neuroscience can inform each other through knowledge that Alzheimer's disease, being irreversible and occurring irrespective of personal choice, has a different effect on personal identity than a psychosis resulting from a personal choice to take steroids. It is unlikely that most psychiatrists would concur, but they may be stimulated by the questions posed.