Life-and-death dilemmas. New medical technologies. Controversial treatments. In playing god? we hear from the patients whose lives were transformed—and sometimes saved—by medical innovations and the bioethicists who help guide complex decisions. Ventilators can keep critically ill people alive, but when is it acceptable to turn the machines off? Organ transplants save lives but when demand outpaces supply how do we decide who gets them? Increasingly, novel reproductive technologies can help people have babies in ways that are far beyond what nature allows. So, when should such...