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
…if there isn’t any God to issue commandments to us, then why think that we have any moral duties? On the atheistic view, human being don’t seem to have any moral obligations to one another. For example, in the animal kingdom, if lion kills a zebra, it kills the zebra but it doesn’t murder the zebra. If a great white shark copulates forcibly with a female, it forcibly copulates with the female, but it doesn’t rape the female, for there is no moral dimension to these actions. None of these things is prohibited or commanded; they are neither forbidden nor obligatory. So if God doesn’t exist, why think that we have any moral obligations? Who or what imposes such prohibitions or obligations upon us? Where do they come from? It is hard to see why moral duties would be anything more than the illusory by-products of social and parental conditioning.
. . . If there isn’t any moral law giver then there isn’t any moral law that imposes itself upon us.
The point is this: If God does not exist, then life is objectively meaningless; but man cannot live consistently and happily knowing that life is meaningless; so in order to be happy he pretends life has meaning. But this is, of course, entirely inconsistent—for without God, man and the universe are without any real significance.
Suppose that no resurrection or miracles occurred: how then could a dozen men, poor, coarse, and apprehensive, turn the world upside down? If Jesus did not rise from the dead, declares Ditton, then either we must believe that a small, unlearned band of deceivers overcame the powers of the world and preached an incredible doctrine over the face of the whole earth, which in turn received this fiction as the sacred truth of God; or else, if they were not deceivers, but enthusiasts, we must believe that these extremists, carried along by the impetus of extravagant fancy, managed to spread a falsity that not only common folk, but statesmen and philosophers as well, embraced as the sober truth. Because such a scenario is simply unbelievable, the message of the apostles, which gave birth to Christianity, must be true.
Belief in Jesus’ resurrection flourished in the very city where Jesus had been publicly crucified. If the people of Jerusalem thought that Jesus’ body was in the tomb, few would have been prepared to believe such nonsense as that Jesus had been raised from the dead. And, even if they had so believed, the Jewish authorities would have exposed the whole affair simply by pointing to Jesus’ tomb or perhaps even exhuming the body as decisive proof that Jesus had not been raised.
Three great, independently established facts—the empty tomb, the resurrection appearances, and the origin of the Christian faith—all point to the same marvelous conclusion: that God raised Jesus from the dead.
Therefore, when a person refuses to come to Christ it is never just because of lack of evidence or because of intellectual difficulties: at root, he refuses to come because he willingly ignores and rejects the drawing of God’s Spirit on his heart. No one in the final analysis really fails to become a Christian because of lack of arguments; he fails to become a Christian because he loves darkness rather than light and wants nothing to do with God.
-–William Lane Craig, Reasonable Faith: Christian Truth and Apologetics