OK one more try.
First. I don't feel picked on by you, so no offense taken.
Now-
You said in your original post, Quote:
I want to check my understanding of the Christian definition of sin...
You have had almost 100 replies to this post and looking back through them, most of the persons answering you have given you their "Christian definition of sin". Several replies have stated to you, that as Christians we believe that mankind will always live in sin until our Lord comes again. So it (sin) "exists independently of individuals' actions",
in the sense that it is going to happen, because there is only one whom is perfect.
So the second part of your original post, you asked 4 questions.
1. "what really is the nature of sin?" The nature (which means the characteristic disposition or temperament) of sin is bad, evil, not nice, etc.
2. "How does it work?" It is when you do something bad.
3. "Is it supposed to be tangible in some form, or is it meant to be taken as a metaphor?" It is quite real.
4. "Is there any way that we as mortal beings can detect its existence or negation?" OK get this. There are 613 laws found in the book of Leviticus and other books of the Old Testament Bible. The Ten commandments, as delineated in Exodus and Deuteronomy, form a brief synopsis (like cliff notes) of the 613 laws. If a human breaks any of those 613 laws he is guilty of sin. If you are guilty of sin you will not go to heaven, but you will be forever separated (isolated) from GOD.
Now, get this. GOD loves us (all mankind) so much that he, through Jesus the Christ, accepted and received the punishment (this week some 2000 years ago) that was due us, because we broke one or more of the laws I spoke of earlier. That is we sinned. GOD did this so that one day we can fellowship face to face with (be in Heaven with) our Lord GOD.
By your icon I see you are a professed atheist, so the"same basic thing has been repeated many times in this thread" because you asked some Christians some questions. Instead of asking other questions rhetorically, until you are getting the answer that you want us to give you, you are probably going to need to accept that you have gotten answers for what questions you asked. Maybe not from me, but at least from someone who took the time to answer this post.
I hope this post doesn't sound condescending, I meant it only with all due respect.
I will pray for you. That you will one day enjoy the glorious gift that only Jesus the Christ can give you in your life. Also, I will be happy to fellowship with you if you need someone to visit with.
I, as a Christian, have to disagree with your analysis of sin. It is NOT something you do. It is not the breaking of one of the 613 Levitical laws. The Levites were men, and those are laws of man. God has only three requirements and two commandments.... love mercy, seek justice and walk humbly with God... and the commandments: Love God, Love your neighbor. All else is irrelevant, or redundant. Don't eat shellfish and cloven hooved animals or those that chew their cud, menstruation is unclean, tithe to the temple, blood sacrifices, don't cut your hair or beard, circumcision, blah blah, blah... God cares NOTHING about those things.
For the non believer, it is simplest to think of sin as our reaction to the realization that we are not perfect... and we want to think we are. SO we do selfish, self serving things in order to make ourselves appear better. Steal, lie, cheat, kill... and self medicate. God doesn't think of us as sinners. We think of ourselves as sinners. God has always forgiven us for not being all that we think we should be, accepted us and tried to communicate to us that we are JUST as we were created: Good and becoming better.
So why the crucifixion? We were and are always demanding we be punished for not being perfect, Karl Menninger describes it in his book Man Against Himself, and Freud called it the death instinct.
Menninger said: "Love cures people - both the ones who give it and the ones who receive it."
The solution to this desire to be punished is love.
What better way to punish ourselves than to get rid of anyone that might accept us, might make us whole and complete, might actually accept us for who we are. It wasn't just Jesus, but his execution certainly was the ultimate expression of this self loathing. We kill all our the prophets, all the "messiahs"... MLKjr, Gandhi... just look how the press goes into a feeding frenzy when they go after someone that is leading the people to some moral or ethical revolution. Malcolm X was fine when he advocated violence and separatism, but when he joined MLKjr in preaching peace and nonviolence.... bang.