A university professor went to visit a famous Zen master. While the master served tea, the professor talked about Zen. The master poured the visitor’s cup to the brim, and then kept on pouring.
The professor watched the overflow until he could no longer restrain himself. "It is overfull! No more will go in!"
"Like this cup," the master said, "you are full of your own opinions and speculations. How can I show you Zen unless you first empty your cup