What keeps moral persons moral now is not religion, but their own sense of what is right and wrong.

I agree, but the question remains how people develop "their own sense of what is right and wrong." If it is an evolutionary thing, then wouldn't that result in absolute values rather than in relative ones? ("their own [individual] sense of what is right and wrong")

I've become interested in the ideas of Michael Sandel regarding justice. Here's a quote from a Michael Gerson column in the Wash Post about Sandel's ideas --

Sandel, in the good company of Aristotle, contends that knowing "the right thing to do" in any of these institutions requires a determination of its purpose. And the purpose of government is not only to defend individual rights but also to honor and reward civic virtues -- patriotism, self-sacrifice and concern for our neighbor. This third definition of justice, by nature, is a moral enterprise.