Summary
In the Fourth Bolgia, Dante sees those who used magic arts, especially the diviners, who foretold the future, moving endlessly around weeping with their heads set backwards on their bodies. Dante weeps for pity to see the human form so distorted, but Virgil rebukes him for grieving at the carrying out of God's justice, and urges him to look, as he points out all the famous prophets from classical myth and history-they tried to look too far ahead, and now they must look only behind. One of the ancient diviners is the woman for whom Mantua, Virgil's native city, was named, and Virgil tells the true story of her role in its founding. Virgil ends by pointing out some famous medieval wizards and fortune-tellers, as well as a crowd of ordinary women who cast spells and told fortunes.

Analysis
In her edition of the Inferno, Dorothy Sayers interprets the basic sin described in this canto as trying to manipulate the material world in the service of the ego. Another way of seeing it is as an obsession with trying to know the future as a way of giving the ego an illusion of knowledge and control. Other interpreters point out how much deception and trickery was involved in the kinds of attempts to know the future that were popular in Dante's time-and perhaps not only then?