The Japanese master Nan-in gave audience to a professor of philosophy. Serving tea, Nan-in filled his visitor's cup, and kept pouring. The professor watched the overflow until he could restrain himself no longer: "Stop! The cup is over full, no more will go in." Nan-in said: "Like this cup, you are full of your own opinions and speculations. How can I show you Zen unless you first empty your cup."