No single principle is more critical to our ethical stance than the one asserting the sanctity of human life. In debates ranging from the care of anencephalic infants to the maintenance of fragile seniors, the question is, Where are the boundaries of sanctified human life? The generally accepted assumption is that a once firm set of principles and definitions is now eroding in the face of “new realities”—a generation's stunning scientific advance in medicine and medical technology. “There is no doubt,” Joam Graf Haber writes, for example, in a recent issue of Cambridge Quarterly, “that the miracles of medical technology have brought up ethical issues not contemplated by us until the very recent past.”