In this episode of Reason at Large, Craig Biddle answers a question from Nick: "Can there be objective morality without God? In other words, can morality be both secular and absolute?"
In answering, Biddle zeros in on the basic reason people need morality, which is in order to live and prosper, and he explains that objective moral principles are identifications of factual requirements of human life. He discusses Ayn Rand's discovery that man's life is the standard of moral value; the principle that reason is man's basic life-serving value; and several moral virtues—including honesty, productiveness, independence, and justice—by means of which people gain or keep the values they need in order to live and prosper.
Finally, Biddle explains why God-based morality is necessarily subjective and utterly incompatible with genuine, objective morality.