Dante wakes up and finds himself "on the brink of the abysmal valley of pain" (lines 7-8). So pitiful are the wailings that rise from that dark valley that Virgil's face is pale with pity, and Dante takes it for fear and hesitates again. But Virgil explains, and they enter the First Circle, also called Limbo. Here there are only sighs, no wailing, and the only suffering, says Virgil, who dwells in this circle, is that "without hope, we live in desire" (line 42); all the souls here were virtuous, or at least free of sin, but they were never brought into the Christian Church through baptism, either because they lived before Christianity like Virgil, or because the teachings of Christianity never reached them, or because they died before they could be baptized. Dante is full of grief at hearing this. Has no one ever escaped this circle? Virgil answers that a great conqueror came here shortly after Virgil died and set free Adam, Noah, Moses, and many others.
Virgil and Dante then come to an area full of light, where those dwell who have won honorable fame and are therefore favored by Heaven. Virgil is welcomed back to this place, which is his home, by the shades of Homer and three other great poets, and all five accept Dante as one of themselves. They walk on to a noble castle, inside of which is a fresh green meadow, and there Dante sees many men and women of Greece and Rome famous for their deeds, as well as the great Muslim leader Saladin, and then the great philosophers of the ancient world, as well as the two Muslim thinkers Avicenna and Averroes, who transmitted much ancient wisdom (including deeper insight into the philosophy of Aristotle) to western Europe.
Finally Virgil and Dante leave, and he comes out of that quiet and bright place "to a part where there is no light" (line 141).
It has seemed strange to many that the noble souls and the innocent infants in the First Circle must be imagined as having crossed Acheron, along with those sinners who blamed everyone else for their misery. In the Paradiso, Dante the pilgrim gets to ask some questions he's been brooding about, and one of them is how it can be right for virtuous people to be denied the chance to get to Heaven just because they lacked baptism. So we know the question troubled him, and perhaps that trouble is reflected here. One interpretation is that Dante believed it was possible to be virtuous without being able to conceive of God as Universal Love, and that in fact only Christ could reveal that truth. What we cannot know, we cannot choose, and in life after death as Dante conceived of it, people have what they chose while alive. And if we consider the allegorical meaning, the nature of Limbo makes clear that to live even a good and honorable life without knowledge of the true nature of ultimate reality as love and bliss is to live without joy, desiring something more but having no hope of getting it.
The story Virgil tells of a mighty one carrying away souls from Hell reflects the medieval belief that when Christ "descended into Hell," as the Apostle's Creed states, he "harrowed" Hell, defeating Satan and freeing all those who had believed in Christ before his birth.
Clearly, Dante reverenced all those he here depicts as dwelling in the noble castle, and he is pictured here as honored to be treated as an equal by the five great classical poets. Dante saw himself as restoring poetry to the high level of the achievements of Greece and Rome, and he announces his role here.
The Inferno: Novel Summary: Canto 4