The Audience Strikes Back2008

Herb:
But there is something else, Bill, and that's Satan, because Satan does in fact exist. People often forget this, but God created Satan, and like all things that God creates, Satan has a purpose. Satan's purpose is so that there can be good and evil in the world, which are necessary to the existence of free will. And sometimes, in testing mankind, God allows Satan to win. He allows Satan to win by giving us the power to choose evil, instead of good, when we are tempted by Satan.