I'd like to argue that good and evil aren't these ethereal concepts that we invent to help ure work smoother, a 'boogie monster' to keep kids in line, or a 'place in our heads' to escape the real world. That would be a bummer.
No, we derive ethics from facts, from concrete things, i.e the existence of God. If you want to shortcut some awesome stuff, you say, "he likes things done a certain way, and he deserves to be obeyed". But really, we do law ethics because we respect other humans as also created by God, which makes humans equal, and damaging Gods handiwork would dishonor him (not to mention get him angry).
But then there's general niceness too. We do that because compared to God, we and all our possessions are very small, so it really doesn't matter what happens to us or them. Making people happy and strating that we trust God points them towards the supplier of all cool things. People say this function all the time in words like "I love you because God loves me."
(this section I wrote 5 minutes before everything else)
Some people say that people who think about good and evil are just deranged, there isn't such a thing, and this adverse mutation will die off pretty quick. What about all the good things religion has brought us in the form of humanitarian things? Crusades, inquisition, slavery, you say. Yeah, yeah. If I were knuts I could go raze a village in the name of pacifist llamas, and then we'd know that pacifist llamas are really bad people, even though most of the time all they do is chew plants.
I have another idea! But its for a different post again...