We tend to define Good and Evil from the point of view of the community, and the species. Things that increase the size of the species or help to prevent the destruction of memes are considered 'good', things that erode the community or destroy social memes are 'bad', I think that's hard-wired into us at a pretty low level.
I think phsychopaths are people who have got that wiring mixed or broken, we are, by nature a group animal, and our mentality has developed around making that work.
For example, groups rely heavily on trust, so people who steal are considered 'bad', however, stealing from another group was considered good, because you are advancing the purposes of your own group. Nowadays we are capable of actually cogitating on the concepts of theft and property, but applying those group memes to a larger 'supergroup' is a rocky process, we fully accept that members of the group should not have their resources and land abused, but we often struggle to apply that same mentality to other groups, because now we are actually going against several million years of meme.
