How does the Inferno reflect both the Christian and Greco-Roman traditions?
Dante Alighieri's Inferno is a classic example of the common theme in medieval Catholic thought of treating Christianity and classical philosophy as a single, shared tradition.
The Christian themes of the text begin at the most basic level: Dante was a Christian and Hell is a Christian concept. Dante's Hell closely followed the Catholic teaching of his time, particularly that of Thomas Aquinas. Aquinas established hierarchies of sin that Dante vividly describes in his descent through Hell's nine rings.
That said, Dante's Hell begins and ends with Greco-Roman themes. The first circle of Hell, the sad and peaceful Limbo reserved for virtuous pagan souls, is full of classical figures, including the Greek poet Homer and the Romans Horace, Lucan, and Ovid. The last punishment on the lowest level of the ninth circle is Lucifer himself, chained in ice, his three mouths each chewing a sinner guilty of treachery. One is Judas Iscariot, betrayer of Christ, while the other two are Brutus and Cassius, who led the coup against Julius Caesar. The two great Christian sinners, Lucifer and Judas, appear with two classical traitors from before the time of Christ.
In between, both Christian and classical touches abound. Demons are given names out of pagan myth, from Charon (the Greek ferryman who conveys Dante and Vergil to Hell) to Geryon (the Monster of Fraud) in the seventh circle, which appears in a story in Vergil's own Aeneid. Yet at the same time Christian figures appear, often as sinners being punished. The Inferno is in part a political text, a screed against Dante's enemies, and Christian noblemen and even popes appear at various points in the text.
The Inferno is a text built on two pillars: without Christian iconography or the classical Greco-Roman tradition, the book could not exist. Christianity provides the structure for Inferno: the concept of Hell, the imagery of flames and demons, and the sins being punished are consistently Christian. The text itself, however, is fundamentally classical. The whole of the Inferno is neatly symbolized by its core characters: Dante the Christian poet, guided and instructed by Virgil the pagan, classical Roman.
The existence of an Inferno (Hell) is an element of the Christian tradition as is the belief in the Holy Trinity. This belief informs the very structure of the Inferno (there are nine circles and the narrative is divided in 33 cantos, plus an introductory canto to the entire Comedy). There are also important references to the Bible and Christian theology. Dante's interpretation of human history is always Christian in nature. This is what Auerbach calls "figural" or "typological" procedure. In this conception, historical events and characters dating back to before the advent of Christianity ultimately represent and pre-figure events and characters belonging to Christianity. For example, the Roman Empire of Augustus which had its official poet in Virgil is read by Dante as an image of God's Kingdom. This procedure was not invented by Dante, but is at the heart of Christianity itself and theologians have explained the relationship of the Old and New Testaments through this concept.
Yet, in Dante's Inferno, Greco-Roman traditions and beliefs are important too. The order of the sinners and the idea of evil are borrowed from Greek and Roman culture and are particularly indebted to Aristotle. In addition, Dante's conception of the universe is clearly derived from the Ptolemaic tradition with the Earth at the center. In this case, however, there is no contrast between the Greco-Roman and Christian traditions as the Church adopted the Ptolemaic model of the universe.
Finally, it shouldn't be surprising that the Inferno and the entire Commedia have both Greco-Roman and Christian elements. Dante's oeuvre was thought as a summa of all cultural traditions and philososphical beliefs that constituted Middle-Ages knowledge.
Many characters from the Greco-Roman tradition populate the Inferno, showing Dante to be well-schooled in classical literature. Dante's guide through hell is Virgil, a Roman poet, and in Canto II we meet up with Aeneas, a Trojan warrior who also took a trip to hell or Hades. In Canto III, Charon, a ferryman from Greek mythology, takes Virgil and Dante across the river Acheron to hell, reminding them that this is a one-way journey.
Not only are characters from the classical world woven into the story, Dante agrees with the Roman concept of hell in which deceit and treachery are the worst sins and designs his circles of hell accordingly.
Christianity is central to the Inferno. The idea of judgment and damnation is an integral part of the New Testament story, which rests on the idea of God's justice being enacted after people die, even if they seem to get away with sins on earth. Blasphemy is severely punished, and Dante's trip to the underworld is meant to get him back on the righteous Christian path after feeling he has lost his way in midlife.
Much of the richness of the Inferno rests on the unabashed way Dante mashes together the imaginative worlds of Greco-Romans and Christians.