That’s the claim anyway. Michael Shermer is fond of using this kind of argument in debates. He reasons that God’s existence is irrelevant to morality because even if God didn’t exist, people would still think killing, stealing, and lying were wrong. Want proof? If it could be proven to you today that God doesn’t exist, would you go out and kill/steal tomorrow (particularly if you knew you could do so without getting caught and punished by the authorities)? No. There are still good reasons to act morally even in the absence of God. Therefore, it follows, claims Shermer, that God is not necessary for morality.
While this has great rhetorical force in a debate, Shermer misses the point completely. The question isn’t whether one needs to believe in God to know and do good, but whether God’s existence is necessary for the good that we know to actually be “good.”