The word ‘mystic,’ which has passed from Greek religion into European literature, is represented in Arabic, Persian, and Turkish, the three chief languages of Islam, by ‘Sūfī.’ The terms, however, are not precisely synonymous, for ‘Sūfī’ has a specific religious connotation, and is restricted by usage to those mystics who profess the Mohammedan faith. And the Arabic word, although in course of time it appropriated the high significance of the Greek--lips sealed by holy mysteries, eyes closed in visionary rapture--bore a humbler meaning when it first gained currency (about 800 A.D.). Until recently its derivation was in dispute. Most Sūfīs, flying in the face of etymology, have derived it from an Arabic root which conveys the notion of ‘purity’; this would make ‘Sūfī’ mean ‘one who is pure in heart’ or ‘one of the elect.’ Some European scholars identified it with σοφός in the sense of ‘theosophist.’ But Nöldeke, in an article written twenty years ago, showed conclusively that the name was derived from _sūf_ (wool), and was originally applied to those Moslem ascetics who, in imitation of Christian hermits, clad themselves in coarse woollen garb as a sign of penitence and renunciation of worldly vanities. The earliest Sūfīs were, in fact, ascetics and quietists rather than mystics. An overwhelming consciousness of sin, combined with a dread--which it is hard for us to realise--of Judgment Day and the torments of Hell-fire, so vividly painted in the Koran, drove them to seek salvation in flight from the world. On the other hand, the Koran warned them that salvation depended entirely on the inscrutable will of Allah, who guides aright the good and leads astray the wicked. Their fate was inscribed on the eternal tables of His providence, nothing could alter it. Only this was sure, that if they were destined to be saved by fasting and praying and pious works--then they would be saved. Such a belief ends naturally in quietism, complete and unquestioning submission to the divine will, an attitude characteristic of Sūfism in its oldest form. The mainspring of Moslem religious life during the eighth century was fear--fear of God, fear of Hell, fear of death, fear of sin--but the opposite motive had already begun to make its influence felt, and produced in the saintly woman Rābiʿa at least one conspicuous example of truly mystical self-abandonment.