In Zen an empty-headed fool is almost ready for meditation. A man full of knowledge is far away from meditation. An empty-headed fool is simply a loving way of saying that you are not far away from becoming wise. The fool can become wise; the knowledgeable never. The empty-headed can become empty-minded, but the man who is carrying scriptures and degrees and the universities and the libraries in his head, he is far away. A master will not unnecessarily waste time on such a person.
