This is a very tricky question. Personally I don't want to be kept alive by a machine, such that if you turned off the machine that the body was not capable to live by itself. But then there's also a tricky one to that, isn't there? For example, Christopher Reeve. Although he is dead now, for many years he wasn't able to keep alive without a breathing machine, but he had the mental capacity and mental presence to choose that he wanted to be kept alive, and he also managed to be able to do a lot of good in the time that he was alive. So it really depends on the brain being alive at that particular time.
As well as far as if a person is in a coma, I recently heard about a person who had been in a coma for twenty odd years, and this person then woke up and they were normal. How do we know? Very difficult. I don't think the person was kept alive by a machine though, other than for feeding. Going back to personally, if I'm in a coma and my body can't live on its own I'm not afraid to die, and so I'd prefer not to be kept alive, but I have the choice to say that and to write that.
Sometimes we have to be careful about these medical terms, alive and dead. How do we know? I mean they are just medical terms. There is also this idea of a person being brain dead so then doctors take their organs away, but I don't know whether they are dead or not? If they are living, and they are still alive to me when the body is alive, we have to look and see whether actually it is our aversion towards the existence of suffering that is motivating us to want to declare them as dead. We have to be careful about this.
It's a very difficult question and as far as life and death, I do believe there is an opportunity at that the time of death and it is a very important moment so I wouldn't want anyone to interfere with that moment. For instance, personally I'm not an organ donor because I wouldn't want anyone to interfere with my body when I'm dying. Because it may upset the consciousness and I believe that the moment of death is very important. and I wouldn't want to upset that moment of death for anybody.