Growing up in the protestant faith, my concept of sin was that it was to do anything god forbade. What that might be was either what it said in the bible not to do, or what the pastor (who supposedly spoke for god) said not to do. A sin was a transgression against god.
It was at the same time that I learned about the concept of forgiveness. (Mind you I was still very young) I was told that the idea of forgiveness was an exclusively christian notion, that other cultures and people did not have this idea of forgiveness. I can remember the person using Japan as an example for some reason.
The interesting thing about sin is that some people define it differently. For me it was usually just going against the 10 commandments. For a few fringe groups, dancing is a sin. (The bible goes both ways on this) The administration at “Liberty” “University” thinks dancing, watching “R” rated movies, and video games are sins.
According to Leviticus 19:27 round haircuts are a sin. Leviticus 11:8 also says football is a sin. Pulling out during sex is a sin. Tattoos, Shellfish, dressing nicely as a woman, and having crushed testicles are also right out according to the bible.
So what about me as an Atheist? What do I think about sin? Does sin exist?
Well since there is no god to transgress against, there can be no sin. This does not mean that there is no such thing as “wrong” in an Atheist’s eyes. I still think that killing, stealing, rape, etc. are wrong. I don’t need a god to tell me that. I don’t, however, think drinking, dancing, sex, games, movies, and shellfish are wrong.
As for forgiveness. I’ve come to realize that this is not an exclusively christian concept. I’m not christian and I still believe in forgiveness. To me, forgiveness is as much about your own healing process as it is about the person who wronged you. You also show higher moral fiber (in my opinion) if you forgive a person instead of holding a grudge.