A Cup of Tea

A Japenese master received a university professor, who came to inquire about Zen. The master served tea. He poured his visitor's cup full, and then kept on going. The professor watched the overflow until he no longer could restrain himself. "It is overfull. No more will go in!"
"Like this cup," said the master, "you are full of your own opinions and speculations. How could I teach you anything?"