If there is no God, then there can be no objective standards of right and wrong. All we are confronted with is, in Jean-Paul Sartre’s words, the bare, valueless fact of existence. Moral values are either just expressions of personal taste or the by-products of socio-biological evolution and conditioning. In a world without God, who is to say which values are right and which are wrong? Who is to judge that the values of Adolf Hitler are inferior to those of a saint? The concept of morality loses all meaning in a universe without God.
As one contemporary atheistic ethicist points out, “to say that something is wrong because . . . it is forbidden by God, is . . . perfectly understandable to anyone who believes in a law-giving God. But to say that something is wrong . . . even though no God exists to forbid it, is not understandable. . . .” “The concept of moral obligation [is] unintelligible apart from the idea of God. The words remain but their meaning is gone.” (Richard Taylor)
In a world without God, there can be no objective right and wrong, only our culturally and personally relative, subjective judgments. This means that it is impossible to condemn war, oppression, or crime as evil. Nor can one praise brotherhood, equality, and love as good. For in a universe without God, good and evil do not exist—there is only the bare valueless fact of existence, and there is no one to say you are right and I am wrong.
–William Lane Craig,
The Absurdity of Life without God
The problem, however, is that I have yet to meet anyone, materialist or otherwise, who was able to dispense with value judgments. On the contrary, the literature of materialism is peculiarly marked by its wholesale profusion of denunciations of all sorts. Starting with Marx and Nietzsche, materialists have never been able to refrain from passing continuous moral judgment on all and sundry, which their whole philosophy might be expected to discourage them from doing.
― Luc Ferry
A Brief History of Thought: A Philosophical Guide to Living
Imagine a person who . . . argues ‘no air exists’ but continues to breathe air while he argues. Now intellectually, atheists continue to breathe — they continue to use reason and draw scientific conclusions [which assumes an orderly universe], to make moral judgments [which assumes absolute values] — but the atheistic view of things would in theory make such ‘breathing’ impossible. They are breathing God’s air all the time they are arguing against him.
―Greg L. Bahnsen