It's a neat question. I recently saw a comment on another forum that basically said "how would we know what is right and wrong without the 10 commandments". Clearly you were not saying the same thing - and went to some lengths to distance yourself from this sentiment.
I think we are all selfish - even the notion of being good to ensure you are well thought of in the afterlife has a selfish dimension. However part of that selfishness recognises this trait in other people and so sometimes, for various reasons to do with social interation (pay forward a favour, form an alliance, angling for sex) we put our self last. This has already be well stated by others posting comments. This is mostly due to empathy. Obviosuly selfish people tend to have less empathy - i.e. the ability to see selfishness in others. So I would suggest empathy is the main source of human decency.
I suppose what I would like to add is that - for whatever reason - people who don't believe in the afterlife generally are as unselfish, decent and kind to others as those who do. This suggests to me an even higher degree of unselfishness. If you believe in god then there is always that overiding motivation to be good, if you don't believe in god, then you do have less motivation, and so this logic would lead me to suggest that ungodly people are less selfish than godly ones.
I think we are all selfish - even the notion of being good to ensure you are well thought of in the afterlife has a selfish dimension. However part of that selfishness recognises this trait in other people and so sometimes, for various reasons to do with social interation (pay forward a favour, form an alliance, angling for sex) we put our self last. This has already be well stated by others posting comments. This is mostly due to empathy. Obviosuly selfish people tend to have less empathy - i.e. the ability to see selfishness in others. So I would suggest empathy is the main source of human decency.
I suppose what I would like to add is that - for whatever reason - people who don't believe in the afterlife generally are as unselfish, decent and kind to others as those who do. This suggests to me an even higher degree of unselfishness. If you believe in god then there is always that overiding motivation to be good, if you don't believe in god, then you do have less motivation, and so this logic would lead me to suggest that ungodly people are less selfish than godly ones.