What is the significance of the mountain?

The Mountain of Purgatory rises at a more than forty-five degree angle, and the narrow paths that circle toward its summit are dangerously unrailed. Sinners are not condemned to Purgatory forever. They are there to do penance for their sins. As in Hell, these penances fit the sins. Penance is not punishment; it is remedial and corrective. This is the primary difference between Hell and Purgatory: the shades in Purgatory have time and the desire lo learn from their sins. They know that they will someday rise to Heaven. Hell, on the other hand, is a hopeless place. At the Last Judgment it will be sealed forever, and its residents exist with no opportunity for repentance, completely without hope. This is the worst punishment possible in the Christian universe.

Dante invented the Mountain and placed it opposite Jerusalem, in what medieval mapmakers thought was the uninhabited southern hemisphere. Since these mapmakers thought this hemisphere was landless and covered with water, it makes sense that Purgatory is a mountain and an island. This region's layout is somewhat simpler than Hell's. Dante divided his Mountain into four levels: Antepurgatory, Lower, Middle, and Upper Purgatory. These last three make up Purgatory proper, and Antepurgatory is like Hell's vestibule or entryway. Atop it all sits the Garden of Eden, The four levels are further divided into circles and terraces. Antepurgatory at the bottom has two circles, and these regions have earthly landscapes. (The sun even rises and sets on the Mountain.)

Purgatory proper is made up of seven terraces, all of which are composed of nothing but bare stone. Counting the Garden of Eden at the peak, Antepurgatory's two circles and Purgatory proper's seven levels, there are ten levels in all. The most sinful inhabit the lower levels and are farthest from God.

The first and lowest level of Antepurgatory is home to two groups of sinners who have not yet begun their penance. This first group contains the excommunicated. The second group inhabits terrace two and contains three subgroups, all of whom lacked spiritual passion. They were, in a sense, spiritually indifferent. On the third terrace, just above these late repentants, is Peter's Gate, which an angel guards. The Pilgrim must pass through this gate before he moves to the seven upper terraces of Purgatory, each of which contains shades who committed one of the seven deadly sins. On these levels temporarily reside those who misused love: the proud, the envious, the wrathful, the slothful, the greedy, the gluttonous and the lustful. This order reverses that of Hell, which has the lustful at the highest level and the proud in the pit at the bottom. Therefore, the Pilgrim moves from worst sin in Hell to worst sin on the Mountain. When he reaches the peak, he meets Purgatory's least sinful souls and is closest to God.

The Pilgrim's education continues as he and Virgil wind their way around and up the Mountain to the Garden, much like the souls must do who are destined for Heaven. The Pilgrim participates in his instruction in much the same was as he does in Hell. On the Mountain he encounters various groups and individuals who sinned while alive and who interact instructively with him. From them he learns valuable lessons about, among other things, humility, love of God and misuse of reason, the power of prayer and the power of poetry. Early on an angel inscribes seven "Ps" (for the Latin for "sin," (peccatum) on his forehead, one for each of the deadly sins. As the Pilgrim moves upward toward innocence, one "P" per level is removed by an angel. Reason can lead him only so far, and after crowning his student lord of himself (Purgatory 27), Virgil vanishes from the Garden of Eden (Purgatory 30). This signifies that the Pilgrim has "graduated" and is ready to move to the next and highest level. He has worked his way back to a state of innocence like that lost by Adam and Eve when they lived in the Garden. From Eden, Beatrice and his faith lead the Pilgrim the rest of the way and carry him on to Paradise.