Among the positive elements in the Sūfī discipline there is one that Moslem mystics unanimously regard as the keystone of practical religion. I refer to the _dhikr_, an exercise well known to Western readers from the careful description given by Edward Lane in his _Modern Egyptians_, and by Professor D. B. Macdonald in his recently published _Aspects of Islam_. The term _dhikr_--‘recollection’ seems to me the most appropriate equivalent in English--signifies ‘mentioning,’ ‘remembering,’ or simply ‘thinking of’; in the Koran the Faithful are commanded to “remember God often,” a plain act of worship without any mystical savour. But the Sūfīs made a practice of repeating the name of God or some religious formula, _e.g._ “Glory to Allah” (_subhān Allah_), “There is no god but Allah” (_lā ilāha illa ’llah_), accompanying the mechanical intonation with an intense concentration of every faculty upon the single word or phrase; and they attach greater value to this irregular litany, which enables them to enjoy uninterrupted communion with God, than to the five services of prayer performed, at fixed hours of the day and night, by all Moslems. Recollection may be either spoken or silent, but it is best, according to the usual opinion, that tongue and mind should co-operate. Sahl ibn ʿAbdallah bade one of his disciples endeavour to say “Allah! Allah!” the whole day without intermission. When he had acquired the habit of doing so, Sahl instructed him to repeat the same words during the night, until they came forth from his lips even while he was asleep. “Now,” said he, “be silent and occupy yourself with recollecting them.” At last the disciple’s whole being was absorbed by the thought of Allah. One day a log fell on his head, and the words “Allah, Allah” were seen written in the blood that trickled from the wound. Ghazālī describes the method and effects of _dhikr_ in a passage which Macdonald has summarised as follows: