A hunter, walking through some woods, came upon a notice. He read the words:
STONE-EATING IS FORBIDDEN
His curiosity was stimulated, and he followed a track which led past the sign until he came to a cave at the entrance to which a Sufi was sitting.
The Sufi said to him:
‘The answer to your question is that you have never seen a notice prohibiting the eating of stones because there is no need for one. Not to eat stones may be called a common habit.
‘Only when the human being is able simultaneously to avoid other habits, even more destructive than eating stones, will he be able to get beyond his present pitiful state.’
From: The Way of the Sufi, by Idries Shah.