So it is with sounds. But the power of sound is greater than the power of color. Why is this? It is because sound arises from the depth of one's being, and because sound can also touch the depth of one's being. The mantra yoga of the Hindus is based on this principle. The Sufi term for this is zikr: that is the use of words for the unfoldment of the soul. But it is not merely for bringing about any desired result that words can be used in zikr. People often make the mistake of using the word without any spiritual idea behind it, simply for the attainment of some magical power. The Sufis of all ages have warned against this mistake, and have constantly taught that there is only one object worth striving for, the essential object of life, namely God. It is only when the science of words is being used for the attainment of truth, that is, for the attainment of God, that it is being used in the right manner. To use it for any other purpose whatsoever, is just like paying out pearls to buy pebbles.