"A brilliant achievement. The range of learning is enormous, both in medieval scientific, philosophical lore and poetry and in the vast secondary literature on Dante. The authors bring the best traditions of Anglo-American formal analysis to bear upon the "petrose, and produce powerful and original interpretations. . . . This will be a book that all serious readers of Dante's poetry--both of the "petrose and the "Comedy--will want to read."--David Quint, author of "Origin and Originality in Renaissance Literature