I'm not saying that atheists can't act morally or have moral knowledge. But when I ascribe virtue to an atheist, it's as a theist who sees the atheist as conforming to objective moral values. The atheist, by contrast, has no such basis for morality. And yet all moral judgments require a basis for morality, some standard of right and wrong.
William A. Dembski
Morality, Values, Moral 