In 1969, Sufi scholar Idries Shah published a volume called The Book of the Book. Its opening pages told of a king whose people would not listen to his teachings, as he lacked an instrument with which to teach them.

The king meets a stranger who tells him of a revered wise man who attributed his knowledge to a tome kept in a place of honor in his room. When the wise man died, his followers eagerly opened the book and found writing on only one page. “When you realise the difference between the container and the content,” it said, “you will have knowledge.”

The rest of Shah’s 200-page book was blank.