This was an issue we faced with my brother. He was in a coma when he arrived at the hospital. He exited it sometime later, but I didn't realize it at all - I think I might have needed some kind of training to notice it. He had lost pretty much all brain function. Still later, his organs began to shut down.
I never thought much about brain failure or how medical technology complicates the way we think about death, and never really thought this particular issue was something I'd care that much about. But I've thought a lot about it since then and how we think about these type of cases tends to reveal so much about how we view the nature of life and living.
Most views about the issue of brain failure and death tend to fall into 2 or 3 camps. The first is that we simply do not know if this person is alive or dead and so we must keep them alive. The second views death differently and says that the conscious person is dead, and that technology is keeping a body alive. A third view tends to rely on the severity of neurological impairment as the basis for determining death, without getting into the death of a person or not.
I have sympathies for the second view, but I don't think I really agree with it too much, though I think it is probably how many people react to the situation. But I think that the way many people would arrive at the view doesn't really require it. It is hard to come to grips with this: when medical technology offers no hope of rescuing a quickly deteriorating condition, withdrawing life support can be an ethical decision. You do not need to call the person dead for it to be ethical. However, saying the person is dead is a way to confront and cope with some of the profound emotions that come with it. I understand it - I lived through it, and I did it.
There are some important concepts embedded in the second view that aren't immediately obvious. Like, what is a person? What makes you, you? The Memory Criterion: "Necessarily, a person who exists at one time is identical with a person who exists at a second time if and only if the first person can, at the first time, remember an experience the second person has at the second time, or vice versa." That is: the absence of memories is the absence of a person. Forgetting might not be death, but a person ceases to exist.
So this view - Locke's view, apparently, and one we ought to think about since Western liberal democracy is built on many of his ideas, yes? - is a distinct view of person-ness. A person is a collection of memories. And so following this idea: we grow into our person, live with it for a while, and then slip out of it. Person-ness is a kind of phase of life - there's a pre-person phase, a person phase, and a post-person phase. What is odd about this idea is that - suppose a case of non-fatal brain damage, a single body could house multiple persons through the course of its life. It is the same organism, but a different person.
Parfit addresses some of the particular problems with this idea and introduces new problems with more of a continuous memory criterion. When does a person survive? When do you cease to be You the Person, and become something else? Like a boat that is repaired so often over many years that it has none of its original wood or parts - Is it still the same boat as it was when it was first built? Is the boat an arrangement of pieces of wood and fiberglass, or is it more abstract? To make the leap to humans: if a person is a continuous string of connected memories - not necessarily the same ones, but there is a linkage between them - and we suppose that generally a body houses the same person from moment to moment, when is that person no longer a person, or the same person as some point in the past? When is the difference between two moments too great for it to be considered the same person?
