Quote Originally Posted by World's End Stella View Post
In which case a person in a vegetative state without any active brain pattern is also a 'human life' and turning off the life support system is the moral equivalent of murder.

See how easily it gets complicated? The human life angle and conception were introduced because of the Catholic church's opposition to abortion. It isn't in anyway disingenuous or dishonest to question the definition of human life and argue that because it is impossible to define it therefore has no bearing on the argument.

Much of that confusion you mention goes away if that is your perspective as well.
No, I'm sorry, but the significant difference here is of potential. The PVS victim has reached a point where life in terms of their brain activity has to all intents and purposes ceased and they can only be sustained artificially. They have no potential for improvement and are alive in name only. When you turn off the machine, nature takes its course.
An embryo, by contrast, is full of potential and to end it is to snuff all of that potential out by a deliberate act of killing. The two are qualitatively different in both ethical and medical terms. One is entirely justifiable in moral terms, while the other is highly morally dubious.
You seem to think that I'm arguing from a position whereby all human life is innately sacrosanct. I'm explicitly not arguing that. I'm arguing that we should acknowledge first of all that we're ending a human life and then work from there.