A respected university professor went to visit a famous Zen master. Before the master spoke, the professor said “I should tell you, I know quite a bit about zen already.” The master smiled and quietly served tea. The professor began talking about Zen. The master poured the visitor's cup to the brim, and then kept pouring spilling tea all over the table and the professor. The professor watched the overflowing and then exclaimed. "It's full! No more will go in! What’s the matter with you?" The master smiled. "You are like this cup," the master replied. "How can I show you Zen unless you first empty your cup."