mikey838 wrote:Why are we alive? What is the difference between us and a rock? What makes a living organism?
The book The Tree of Knowledge has some interesting things to say about that. Me, I would say that primarily what makes something alive isn't something you can measure..it's just obvious.. sure there are unclear lines in that case, but there are also ambiguities in defining/classifying what's alive on empirical/absolute grounds. The physical aspect of life/its delineation is an observation we make *after* primarily distinguishing life based on the observation that it's animate or not. How would you judge whether a possible way of defining life materially makes sense or not? By comparing it to what's obviously life. (Consider that "life" had a meaning way before science even knew what a cell was, or what organs are for. Consider that "life after death" isn't an oxymoron in essence.)
But yes, the physical makeup of something is a function of whether it's alive or not--or vice versa, the point being that certain physical forms can act as vessels or catalysts for life.. or vice versa. It's "synchronous." A rock turned cellular can become alive, and a person turned rock will have passed on.
But that does leave the question of what characteristics define a form that is suitable for life to inhabit (or at least, be recognized.. a rock could be a very peaceful entity.), and I think that book I mentioned has some good ideas about this. The things that come to *my* mind are holism, synthesis, and structure on the edge of chaos.