This world to a mystic is like a dome, a dome that gives a re-echo of all that is spoken in it. What is spoken from the lips reaches only as far as the ears, but what is spoken from the heart reaches the heart. The word reaches as far as whence it has come; it depends from what source it has come, from what depth it has risen. The Sufis of all ages have therefore given the greatest importance to the word, knowing that the word is the key to the mystery of the whole life, the mystery of all planes of existence. There is nothing that is not accomplished, there is nothing that is not achieved or known through the power of the word. Therefore in esotericism or mysticism the word is the principal and central theme.