What if we are missing something?
We are able to build sort of intelligent systems, and we are able to build sort of capable perception systems, and we are able to build sort of life-like robots, and we are able to sort of evolve agents and robots, and we are able to build systems that act sort of like the immune system, but none of these artificial systems we build is ever mistaken for the real thing, for a real living thing. We sort of know how a bacterium works, but we have no real idea on how to build a living machine.
Could it be that we are missing something fundamental about how living things are organized and how they are maintained in the world? What is it that separates living from non-living matter?
I will suggest a bunch of hypotheses and debunk those that are not my favorite.