[Matthew Shea]

Sin certainly is an abstract concept, but so are karma, love, evil and many other things that most of us accept as "real."

Also, I'd dispute that sin is purely ignorance. That's certainly a big part of it, but not the whole thing. There's an element of rebelliousness, too, which is really what causes problems. Ignorance can be taught, but rebelliousness is much harder to treat. You have to dive deep inside a person to find the individual cause. Take me, for example. I know it's wrong to drive over the speed limit and I'm perfectly aware of the potential consequences, but I continue to do it from time to time knowing I shouldn't. That's a mild example of the rebelliousness I'm referring to and is a big part of what makes the sin.

Finally, I think you're oversimplifying and making a big assumption when you say people all want to gravitate towards love. Some people only truly love themselves, others want to serve others. Love of yourself is fine and there's nothing inherently wrong with taking actions based on that love, but you can certainly do something drastically wrong, even though your reason for acting is "love."