_The Mirror of Simple Souls_, as we now have it, is a work of nearly 60,000 words in length. So far from being simple, it deals almost exclusively with the rarest and most sublime aspects of spiritual experience. Its theme is the theme of all mysticism: the soul’s adventures on its way towards union with God. It is not, like the _Melum_ of Richard Rolle, or _Revelations_ of Julian of Norwich, a subjective book; the record of personal experiences and actual “conversations in heaven.” Rather it is objective and didactic, a work of geography, not a history of travel; an advanced text-book of the contemplative life. Only from the ardour and exactitude of its descriptions, its strange air of authority, its defiance of pious convention, can we gather that it is the fruit of first-hand experience, not merely of theological study: though its writer was clearly a trained theologian, familiar with the works of St. Augustine and Dionysius the Areopagite, whom no mystic of the Middle Ages wholly escaped, and apparently with those of St. Bernard, Hugh and Richard of St. Victor, and other mediæval authorities on the inner life. I have said that the _Mirror_, as we have it, purports to be the translation of an unknown French treatise. This translation, so far as we can judge from its language, was probably made in the early years of the fifteenth century, perhaps at the end of the fourteenth. Its author, then, lived at the close of the golden age of English mysticism: he was the contemporary of Julian of Norwich, who was still living in 1413, and of Walter Hilton, who died in 1395. Himself a mystic, he was no servile translator; rather the eager interpreter of the book which he wished to make accessible to his countrymen. Our manuscripts begin with his prologue: an ingenuous confession of the difficulties of the undertaking, his own temerity in daring to touch these “high divine matters,” his fear lest the book should fall into unsuitable hands and its more extreme teachings be misunderstood. It appears from this prologue that our version of the _Mirror_ is a second, or revised edition; the first having failed to be comprehensible to its readers.