Thanks for elaborating, I think I understand what you mean now! I was really confused when you said that beaver dams are just like fences, because to me they're not at all the same. It sounds like we actually have a very friendly disagreement. =)

I think "nature" is our best way to express these important but nebulous concepts, but you think it hides those exact same concepts. We're probably both right -- it will depend what community we're in, and their understanding and interpretation of the word "nature".