Professor Scholem, who is professor of Jewish Mysticism in the Hebrew University in Jerusalem, has produced a very important book, which will at once take its place in the list of the most significant books that have appeared on Mystical Religion. Baron von Hügel's The Mystical Element in Religion came at the end of 1908. My Studies in Mystical Religion came out in 1909, and Evelyn Underhill's Mysticism appeared in 1911. We all three were working independently of one another and, without knowing that anyone else was engaged in the undertaking, we produced our results almost simultaneously, and though representing three different types of religious thought, we became intimate friends through our work, and all three books went through various editions. Dean Inge had already, in 1899, published his important book on Christian Mysticism, and in 1902 William James had published his work of genius, Varieties of Religious Experience. Between 1911 and the present date there has been a remarkable output of books on Mysticism, many of them valuable contributions to the subject, and Mysticism has become an important feature of the interpretation of religion in our time. But meantime there had been no adequate interpretation of the great stream of Jewish Mysticism. In 1913 J. Abelson published a valuable little book on Jewish Mysticism, and in 1935 Jacob Minkin wrote a popular book on The Romance of Hasidism.