No medical specialty addresses fundamental ethical issues more frequently than does neurology. The reason is simple: the brain is so basic to human identity that even the language of transplants must be stood on its head when we talk about it—for who could argue that a "brain transplant" could be anything but a misnomer? If we ever did manage to take Charlie's brain and put it in Billy's head, would we claim that the resulting person was Billy, just because he looked like him, rather than Charlie, whose brain would then be running the show? When something happens that fundamentally changes the way the brain works—stroke, trauma, medication, disease—what does that do to the person whose identity is largely defined by that brain? And when we as clinicians intervene, what are our obligations when we explore the possibilities? What if we do the same to someone who isn't even sick? These and other ethical questions are explored in this month's issue.