Disclaimer: this post is opinion based.
How do we tell if a human is alive (or dead)? We check if the vital organs of the body is alive. How do we tell if an organ is alive well we check if it is parts are ok and so on.
– but just because my skin consists of dead cells, should not mean that it is dead itself. If it is doing what it is supposed to do (holding you together, providing a little support and defense for the rest of the body), then I think it should mean that it is alive.
I think the essence of life should be to function. We should call something is alive or dead depending if it is functioning or not. Of course, then, this depends on the purpose you assign to the thing. If you say a stone’s purpose is to occupy volume then it is alive but then everything else is also alive. So, this whole thing depends on how you measure things (and how you measure begin alive/dead).
If I can measure whether I am alive or not, then I am functioning and I should be alive. But if i cannot measure, then I am dead (and worse than that I don’t exist) and agreeing to this view also has a dull answer to “why are we here” or “why are we alive”. Because otherwise, we would not be able to measure and would not ask the question in the first place.
This is actually quite close to what Descartes said. He says I think, so first I must exist to be able to think. Therefore, I exist. But I think this is a slight generalization of I think therefore i am.