The Topless Tower

Once upon a time, a king, wishing to teach his son humility, built a small pile of stones on the ground and then asked his son,
"Can you put a stone on top of the top of that pile of stones?".
"Ofcourse", said the son, "Thats easy".
And picking up a stone from the ground he placed it on top of the pile.
"But now the stone you have added has become the top of the pile", said his father, "And so you have not put a stone on top of the top".
"Huh?", said the boy, scratching his head.
"Each time you add a stone to the pile, that becomes the top and so, however high you build the pile of stones, you can never place a stone ontop of the top. There is no final top", explained his father, "And that is like power. However great or powerful you think you are, though you may think you are at the top, there is always someone or something more powerful than you".
"But who is more powerful than you father?", asked the boy.
"Greater than kings are emperors; greater than emperors are gods; greater than gods...", said the king, "Who knows?".