The Essay by Mr. Lowell, to which I have already referred (Dante, Lowell's Prose Works, vol. iv.) is the best introduction to the study of the poem. It should be read and re-read.
Dante, an essay by the late Dean Church, is the work of a learned and sympathetic selmolar, and is an excellent treatise on the life, times, and work of the poet.
The Notes and Illustrations that accompany Mr. Longfellow's translation of the Divine Comedy form an admirable body of comment on the poem.
The Rev. Dr. Edward Moore's little volume, on The Time-References in the Divina Cominedia (London, 1887), is of great value in making the progress of Dante's journey clear, and in showing Dante's scrupulous consistency of statement. Dr. Moore's more recent work, Contributions to the Textual Criticism of the Divina Commedia (Cambridge, 1889), is to be warmly commended to the advanced student.
These sources of information are enough for the mere English reader. But one who desires to make himself a thorough master of the poem must turn to foreign sources of instruction: to Carl Witte's invaluable Dante- Forschungen (2 vols. Halle, 1869); to the comment, especially that on the Paradiso, which accompanies the German translation of the Divine Comedy by Philalethes. the late King John of Saxony; to Bartoli's life of Dante in his Storia della Letteratura Italiana (Firenze, 1878 and subsequent years), and to Scartazzini's Prolegomeni della Divina Commedia (Leipzig, 1890). The fourteenth century Comments, especially those of Boccaccio, of Buti, and of Benvenuto da Imola, are indispensable to one who would understand the poem as it was understood by Dante's immediate contemporaries and successors. It is from them and from the Chronicle of Dante's contemporary and fellow-citizen, Giovanni Villani, that our knowledge concerning many of the personages mentioned in the Poem is derived.
In respect to the theology and general doctrine of the Poem, the Summa Theologica of St. Thomas Aquinas is the main source from which Dante himself drew.
Of editions of the Divina Commedia in Italian, either that of Andreoli, or of Bianchi, or of Fraticelli, each in one volume, may be recommended to the beginner. Scartazzini's edition in three volumes is the best, in spite of some serious defects, for the deeper student.
