In his book Tide Rising Bruce Theileman used this illustration:
It is said that Satan once called to him the emissaries of hell and said he wanted to send one of them to earth to aid women and men in the ruination of their souls. He asked which one would want to go. One creature came forward and said, “I will go.” Satan said, “If I send you, what will you tell the children of men?” He said, “I will tell the children of men that there is no heaven.” Satan said, “They will not believe you, for there is a bit of heaven in every human heart. In the end everyone knows that right and good must have the victory. You may not go.”
Then another came forward, darker and fouler than the first. Satan said, “If I send you, what will you tell the children of men?” He said, “I will tell them there is no hell.” Satan looked at him and said, “Oh, no; they will not believe you, for in every human heart there’s a thing called conscience, an inner voice which testifies to the truth that not only will good be triumphant, but that evil will be defeated. You may not go.”
Then one last creature came forward, this one from the darkest place of all. Satan said to him, “And if I send you, what will you say to women and men to aid them in the destruction of their souls?”
He said, “I will tell them there is no hurry.”
Satan said, “Go!”