I've had occasion to consider this with one of my patients. She is only a few months old, but she suffered some considerable complications during or before her birth, it isn't clear which. She will likely never progress from her current state, which is that she can swallow, weakly and only occasionally, she cannot protect her airway, so she aspirates food into her lungs, and she suffers recurrent seizures. She has an EEG displaying burst supression, which is just one step removed from brain dead. In a particularly difficult patient encounter, our pediatric neurologist told the father that, though pediatric brain injury prognosis is difficult to predict, his daughter would likely never feed herself, walk, comunicate, see, hear, or even have a thought. The father's response was "why didn't you kill her along time ago then?"
Though of course actively euthanizing patients in prima facie wrong, I don't know that answer is a good one. Should patients with no hope of recovery be kept alive like this? It's not like that media circus Terri Schiavo case, here the patient has never interacted with anyone. She was born unresponsive and displays nothing but the most primitive of reflexes now. She is only alive because of medical miracles and heroic support measures undertaken at birth, but right now, she doesn't need anything but a tube feed. The argument against letting Mrs. Schiavo die was that a tube feed is not a heroic measure. But I think that's a poor one in this situation.
True, it isn't heroic, but what is heroism but defense of a worthy cause? I'm no longer able to say I believe life is, in the abstract, a worthy cause. I don't know what is. What is it that makes a life worth defending? How do we define "humanness" here? "In the image of God we are made" but how much of that image is interaction, is thought, is contribution, is soul? And how much is the "crude matter" which comprises our physical form?