Canto VIII The poets are introduced by Sordello to other souls among the preoccupied, including some known to Dante who ask his prayers and prophesy his forthcoming personal and political difficulties. Two angels descend to guard the valley at nightfall, and drive away a serpent. As night falls the four stars that Dante saw at dawn pass out of sight, and three take their place.

Dorothy Sayers makes the point that the angelic defeat of the serpent is hardly a serious struggle, it is an almost ritual bout. These souls are not seriously at risk from temptation, but they are susceptible to anxiety, they are not yet in Purgatory proper. The angels are dressed in green, the colour of hope. The souls have cause for hope, but have perhaps yet fully to appropriate it. Progress up the mountain is a work of grace; the same grace by which the theological virtues, faith, hope and love, are infused into the soul. These virtues are represented by the three stars, but as Dorothy Sayers says in another astronomical diversion, neither the three stars of the theological virtues nor the four of the cardinal virtues ever set on Mount Purgatory. Both are needed, but in the night, with the enforced rest and angelic guard, perhaps the dependence on the three is most apparent.