An Atheist Ethic
Pretty straightforward question. What is a philosophically consistent atheist ethic composed of? How should one act under the assumption there is no god? What restrictions are(n't) there on behavior? But most importantly, on what is an atheist ethic based which gives it credence?
Note: It's worth pointing out that I ask this out of authentic curiosity. I'm not waiting for some sort of expected response so I can make a rhetorical leap for the jugular.