In the DOMA thread, the issue of morality came up a few times, and I thought I'd make a separate thread about this issue. There are several theories about the source(s) of our moral principles (evolution, the brain, religion, etc.), and I'm curious to know what you guys think influences our moral principles. Is a God-like figure necessary for morality? Or can we come up with moral principles using reason and logic? On a related note, I've been reading about moral nihilism. It's certainly an idea worth thinking about.