Firstly, I want to check my understanding of the Christian definition of sin... I'm under the impression that it's something like, "transgression against God," and that it has nothing to do with whether or not an act is harmful to another human being. (This is based on the observation that God has often done things, or required others to do things, that hurt people, but are righteous in his eyes.) I'm also under the impression that sin somehow exists independently of individuals' actions, if an infant could be said to be sinful before it is old enough to really do anything yet. (But feel free to expand on this paragraph if need be.)
Anyway, here's what I'm wondering: what really is the nature of sin? How does it work? Is it supposed to be tangible in some form, or is it meant to be taken as a metaphor? Is there any way that we as mortal beings can detect its existence or negation? In particular, I'm wondering about sin both in the sense of "original sin" and in the phrase, "Jesus died for our sins" -- if someone could explain how sin operates in both of these contexts, I'd appreciate it.
Sorry for the number of questions, but since they're all centered around the same basic topic I'm hoping it won't be a problem. Thanks in advance for your responses.