I do think it's primarily nature, though nurture isn't meaningless. How you react to what you are dealt with is your nature. Good parenting doesn't necessarily make for good children/people, and bad parenting doesn't mean the creation of horrible people. I think the worst thing would be to be isolated with only the influence of parents. The fact that there's a whole world out there means that those who are exposed to it can choose who they want to be. Not having the choice is the saddest thing, I think.