Monks

A man is driving down the road and breaks down near a monastery. He goes to the monastery, knocks on the door and says "My car broke down. Do you think I could stay the night?" The monks graciously accept him, feed him dinner, even fix his car. As the man tries to fall asleep he hears a strange sound. A sound unlike anything he's ever heard before. The Sirens that nearly seduced Odysseus into crashing his ship come to mind. He doesn't sleep that night. He tosses and turns trying to figure out what could possibly be making such a seductive sound. The next morning, he asks the monks what the sound was, but they say "We cannot tell you. You are not a monk."
Distraught, the man is forced to leave. Years later, after never being able to forget the sound. the man goes back to the monastery and pleads for the answer. The monks reply "We cannot tell you. You are not a monk." The man says "If the only way I can find out what is making that beautiful sound is to become a monk, then please, make me a monk." The monks reply "You must travel the Earth and tell us how many blades of grass there are and the exact number of grains of sand. When you find these answers, you will have become a monk."
The man sets about his task. After years of searching he returns and knocks on the monastery door. "I have traveled the Earth and have found what you have asked for. By design, the world is in a state of perpetual change. Only God knows what you ask. All a man can know is himself and only then if he is honest and reflective and willing to strip away self deception." The monks replied "Congratulations, you are now a monk. We shall now show you the way to the mystery of the sound."
The monk leads the man to a wooden door where the head monk says "The sound is beyond that door." The monks give him the key and he opens the door. Behind the wooden door is another door made of stone. The man is given the key to the stone door and he opens it, only to find a door made of ruby. And so it went that he needed keys to doors of emerald, gold and diamond.
Finally the monks say "This is the last key to the last door." The man is apprehensive to no end. His life's wish is behind that door. He unlocks the door, turns the knob and behind that door he is utterly amazed to find the source of that haunting and seductive sound...... But I can't tell you what it is because you are not a monk.