From a purely scientific perspective, the distinction that you or I might grant to "human life" doesn't exist. That's purely a creation of spirituality and faith. From a scientific view, "human life" is a designation that society has created and grants.It isn't scientific for you or me, but the concept of human life to someone who is an atheist it is scientific - isn't it?
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Some credible scientists will argue that a robot is capable of becoming "alive" simply because we (humans) can impart it with such. So determining "human life" from a purely scientific perspective will be impossible.
And with this scientific view, there is no distinction between human "life" or any other kind of life. Aborting a fetus at conception or the day after it's been born is no different. The organism is more complicated, but that's all. These are all moral and ethical decisions that people and our society has imposed, but they aren't scientific.
Issues of life, by their very definition are spiritual and ethical. If you feel that there is a spirituality, that there is a unique human spirit, then you are ethically required to defend it. And if you can't, then you need to acknowledge the destruction of the "life." And if you take a position like that, I would expect the person to be able to explain why it's acceptable. (as I mentioned in the case of the death penalty.)
I don't think this is a "freedom of religion" question at all. I think it's a fundamental issue that defines our society. Regardless you're religion, you don't have a right to destroy those that society regards as the living. And because a particular religion, sect, or philosophy, doesn't share that recognition, that doesn't exempt them from.
It's far to easy to hide behind "science" in this discussion. The truth is, science doesn't have all the answers. Without the cover of science, we can't fall back on moral relativism and we're forced to contemplate difficult issues.
I don't presume to have the answer for this one... I'm still trying to get my head around the questions.
I think I've pretty much responded to everything in your last post, so I'll avoid any further quoted replies.