The definition of life is growing in importance. We want to know when human life begins for lots of ethical, legal, and religious reasons. We want to know that if we find something crawling around on Mars it can be classified as life. As artificial intelligence evolves, we want to know when to start granting androids rights. And if a human is in a coma, we want to know at what point that individual could be considered no longer alive.
So I was noodling with a functional definition of life that aims to solve our current and future ethical dilemmas. How about defining life as any discreet entity with the following qualities:
This definition keeps our future androids from getting full legal rights, since they can't feel pain. And it would let you pull the plug on anyone who doctor's say has no potential to ever feel pain or learn again. So far, so good.
One thorny issue is that life would begin at conception by this definition. It would be a separate argument as to whether the woman carrying the life has a right to terminate it while it is still in the early potential phase.
My definition keeps a virus from being considered life. And plants too, I think. That feels right. I don't think lettuce needs to be "alive" any more than my watch.
I haven't thought this idea through. I'm just throwing it out there for consideration.