  Finally, many have argued that considerations of personal identity can shed light on the nature of death, which itself plays a key role in moral argumentation (Green and Wikler 1980; Zaner 1988; Puccetti 1988; McMahan 2002; DeGrazia 2005). One popular line of thought, based on the Psychological Criterion, has been that when an individual is at the point when she is no longer able to sustain any psychological continuity, her identity has ceased, and so she should be considered dead. This idea has led many philosophers to advocate for a criterion of death known as the “higher brain standard,” according to which death occurs at the point of irreversible loss of the capacity for consciousness (e.g., Green and Wikler 1980). This psychological criterion of death implies that those in a permanent vegetative state are dead, despite their continuing brainstem activities. This philosophically popular view has never, however, been adopted anywhere. Those favoring the Biological Criterion advocate a view much more in line with actual medical practice. If we are essentially human organisms, according to these advocates, then our death occurs at the point when that organism dies. There is still wrangling over when precisely that occurs, however. Some favor a “death of the whole brain standard,” whereas others, dissenters as DeGrazia labels them, adhere to a “circulatory-respiratory standard,” according to which “human death is the permanent cessation of circulatory-respiratory function” (DeGrazia 2005, 149). It is less clear, however, what role personal identity actually plays in this debate. After all, the cessation of my identity may have nothing to do with anything like organismic (or brain) death. On any view of personal identity other than four-dimensionalism, recall, I cease to exist if I undergo fission. There will be no one in existence who is me, but this fact is irrelevant to our thinking about death. It may be the case, then, that seeking the factors involved in cutting off someone's personal, or human, identity will yield no insights into the nature of death itself.  (For further discussion, see DeGrazia 2003, and McMahan 1995 and 2002.)