Students of comparative literature recognize in the story a body of tradition reaching back into remote times and forward to the Renaissance, finding its most perfect expression in Dante's "Divine Comedy" (1321). Mediæval descriptions of hell and heaven were made more vivid by adopting the literary form known as the _vision_. The most familiar sort of vision is that which describes things seen in a dream, after the author has fallen asleep. "The Pilgrim's Progress" is an example of this type. Another sort of vision is that which relates what has been perceived by some one in a state of mystical exaltation, as in the Apocalypse of Saint John. The most realistic form of vision is that of "Saint Patrick's Purgatory," where the experiences are described as if actually undergone, and yet they so transcend human probability that the reader recognizes the apocalyptic element. The term "vision" is usually applied to poems describing mysteries of religious or moral truth, and "dream" is applied to secular works such as "The Romance of the Rose," and many other popular poems. Examples of visions from various epochs should be read in order to trace the history. Easily accessible texts in translation are ST. JOHN. Revelation. (King James Version.) HOMER. Odyssey, Book XI (translated by G. H. Palmer). Houghton Mifflin Company, Boston, 1891. VIRGIL. Æneid, Book VI (translated by J. Conington). The Macmillan Company, New York, 1910. CICERO. Scipio's Dream (translated by C. R. Edmonds in the Bohn Library Cicero). The Macmillan Company, New York. BEDE. The Vision of Dryhthelm (in Cook and Tinker's "Old English Prose," p. 58). Ginn and Company, Boston, 1908. DANTE. The Divine Comedy (translated by C. E. Norton). Houghton Mifflin Company, Boston, 1893. The Pearl (translated by S. Jewett). Thomas Y. Crowell Company, New York, 1908. For critical studies of the vision and for exhaustive bibliographies of the subject, see Apocalypse. Encyclopædia Britannica. WRIGHT, T. Saint Patrick's Purgatory. London, 1844. KRAPP, G. P. The Legend of Saint Patrick's Purgatory. John Murphy Company, Baltimore, 1900. BECKER, E. Mediæval Visions of Heaven and Hell. John Murphy Company, Baltimore, 1899. LANGLOIS, E. Origines et sources du Roman de la Rose, chap. v. Paris, 1890. For information regarding the dream _motif_ in mediæval poems, see OWEN, D. Piers Plowman, A Comparison with some Earlier and Contemporary French Allegories, pp. 134-167. Hodder and Stoughton, London, 1912. NEILSON, W. A. The Origins and Sources of the Court of Love. (See "Dream-setting" in the index.) Ginn and Company, Boston, 1899.