To the English reader the mysticism of Rumi opens a new world of spiritual and poetical experience. God is One but religions are many runs the Sufi teaching; and the English reader can here enlarge his experience by apprehending the mystic intuition of a great Persian poet. The late Professor Nicholson’s beautiful and faithful translations are illuminated by Notes on Sufi doctrine and experience. Professor Nicholson did not finish the Introduction, but it has been completed by his old pupil and friend, Professor A. J. Arberry, who has seen the book through the press.