As life-preserving medical technology advanced in the second half of the 20th century, doctors and families were faced with a thorny decision, one with weighty legal and moral implications: How should we define when life ends? Cardiopulmonary bypass machines could keep the blood pumping and ventilators could maintain breathing long after a patient's natural ability to perform those vital functions had ceased.
After decades of deliberations involving physicians, bioethicists, attorneys, and theologians, a U.S. presidential commission in 1981 settled on a scientifically derived dividing line between life and death that has endured, more or less, ever since: A person was considered dead when the entire brain — including the brainstem, its most primitive portion — was no longer functioning, even if other vital functions could be maintained indefinitely through artificial life support.
