Medical technology has confused the simplicity of death. One quote from the piece at New Atlantis:
...as long as the ventilator remains, that body does not look like a corpse. It remains warm, like the living, and the organs continue to do the work they have always done, albeit with the assistance of chemical interventions. Most significant and most challenging, from the point of view of common sense, is the fact that the heart still beats. The injury to the brain has destroyed the centers in the brainstem that regulate breathing—thus the perpetual need for the ventilator. But the heart of an animal—even one profoundly injured—has its own “inherent rhythmicity,” its own originative source of motion. This means that heartbeat and circulation have no absolute dependence on the brain in the way that respiration has. The heart, without any input from the brain, can continue to beat as long as its own tissue is intact.
The characteristic puzzle of the total brain failure condition, then, is this: the body remains warm and pink as blood courses through the vessels; the vital organs continue performing their work; but the human being as a whole, permanently unconscious and permanently and profoundly disengaged from his surroundings—eyes closed, making no response to pain, making no effort to breathe—seems something short of alive.
