The practice of transplantation of vital organs from "brain-dead" donors is in a state of theoretical disarray. Although the law and prevailing medical ethics treat patients diagnosed as having irreversible total brain failure as dead, scholars have increasingly challenged the established rationale for regarding these patients as dead. To understand the ethical situation that we now face, it is helpful to revisit the writings of the philosopher Hans Jonas, who forcefully challenged the emerging effort to redefine death in the late 1960s.