The Moral Argument (and Counterargument) by Michael Shermer
“The Moral Argument. Humans are moral beings and animals are not. Where did we get this moral drive? Through the ultimate moral being – God. Without God, without the highest of higher moral authorities, anything foes and there would be no reason to be moral.
Counterargument. The argument that we cannot be good without God is easily refuted through a simple and straightforward question: What would you do if there were no God? The question can be followed by an additional question that draws the denouement: Would you commit deception, robbery, rape, and murder, or would you continue being a good and moral person? Either way the argument is over. If the answer is that people would quickly turn to deception, robbery, rape, or murder, then this is a moral indictment of their character, indicating they are not to be trusted because if, for any reason, they turn away from their belief in God (and most people do at some point in their lives), the plug is pulled on their constraints and their true immoral nature is revealed; we would be well advised to steer a wide course around them. If the answer is that people would continue being good and moral, then apparently you can be good without God.”
Shermer, Michael. 1999. How we Believe: The Search for God in an Age of Science. New York: W.H. Freeman, p. 98.