overflowNan-in, a Japanese master during the Meiji era (1868-1912), received a university professor who came to inquire about Zen.

Nan-in served tea. He poured his visitor’s cup full, and then kept on pouring.

The professor watched the overflow until he no longer could restrain himself.

Professor: It is overfull. No more will go in!
Nan-in: Like this cup, you are full of your own opinions and speculations. How can I show you Zen unless you first empty your cup?