Canto 24 is taken up with the climb of the three poets from the terrace of greed to the terrace of lust, and an extended conversation they have along the way in which Statius explains for Dante's benefit the relationship between the physical body and the soul (according to a mix of theology and Aristotelian biology) and how this accounts for the fact that the bodies of the souls in purgatory cannot die yet can suffer the visible deprivations of hunger. This is a sort of Aristotelian SciFi element to the Divine Comedy which, though doubtless fascinating to its medieval readers, often give the work a reputation for being hard to understand among 20th century readers.
At last, the poets come reach the next terrace, much of which is covered by a wall of fire. They begin to move carefully along the edge of the terrace, with fire to the left and a precipice to their right, and soon realize that there are spirits moving through the fire, and calling out to one another encouragement in the form of examples single and marital of chastity from Christian history and pagan mythology.
From inside the fire, souls call out to Dante asking him who he is that he walks unburned and still in his mortal body, but as he is about to explain he sees another group of souls coming through the fire walking in the opposite direction of those who have stopped to speak to him.
For down the middle of the burning road
Came people with their faces opposite
To these, and they made me stare in suspense.
There I saw all the shades on either side
Hurrying and kissing one another
Without halting, content with this brief greeting:
As ants in black battalions rub their muzzles,
One with another, so as to seek out,
Perhaps, their prospects and their way ahead.
As soon as these break off their friendly welcome,
Before they take the first step to set off,
Each one attempts to outshout all the rest,
The newcomers crying "Sodom and Gomorrah!"
The others, "Pasiphae climbs in the cow
To let the bull come gallop to her lust!"
Then just like cranes that fly away, some
To the Riphean mountains, some toward the sands,
These to escape the frost and those the sun:
One group of people leaves and one comes on,
And they return in tears to their first chants
And to the shout most suitable for them.
(Purg. XXVI, 28-48)
[Note: In Greek mythology, the Cretan queen Pasiphae was taken with a lust for a bull as a result of a spell put on her by the god Poseidon. She had a wooden cow (with necessary openings) made for her so that she could attract the bull's attention, and as a result conceived the Minotaur, half man and half bull.]
Once the other group of souls has moved off, those who had first asked Dante for his story repeat their request, and he explains about how Beatrice's prayers have resulted in the gift of a chance to travel through hell, purgatory and heaven in order that he may return to the road of virtue. Dante then asks the souls the nature of the other group which just passed going in the other direction and they explain the nature of their own sins and those of the other group of souls.
"The people who don’t come with us offended
By that same sin for which Caesar in triumph
Once heard a voice call out against him, ‘Queen!’
"And that is why they run off shouting ‘Sodom!’
Railing against themselves, as you have heard,
And so support the burning with their shame.
"In sinning we were heterosexual:
But since we did not yield to human law,
Following our appetites like beasts,
"To heap opprobrium upon ourselves,
Leaving those shades, we blare the name of her
Who bestialized herself in beast-like planks.
(Purg. XXVI, 76-87)
Dante's point here about the two forms of sexual sin (gay and straight) is interesting: He labels both sodomy and "straight" fornication and adultery as sins against nature, the former for obvious reasons and the latter because they violate the state of faithful natural marriage. Because Dante sees monogamous fidelity as the natural state of the human person, even "straight" sexual sins are deformations of nature's intent.
Sinners gay and straight now share a brief embrace and kiss as they pass each other in the flames, in sign that they now understand the right place of physical affection and do not allow it to be a lure which draws them from the path towards salvation.
The shades speaking to Dante then introduce themselves personally. They prove to be authors of courtly Italian love poetry, which was a great influence on Dante's early style, and the poets take a few moments to express admiration for each others' work before the penitents continue their journey through the flames and Dante (after promising to pray for them) continues along the terrace with his guides.
A little way further and Dante reaches his most difficult point yet on the journey which has taken him from the wasteland of sin, through hell and repentance to this point. They reach the pass up from the terrace of lust, guarded by the angel of chastity.
He stood upon the bank, outside the flames,
And sang aloud, "Blessed are the clean of heart!"
In a voice far more alive than ours.
Then, "You may go no further, holy souls,
Unless the fire sting you: enter it,
And don’t be deaf to what is sung beyond,"
He said to us when we drew near to him;
And when I heard him speak so, I became
Like someone buried in the pit, alive.
I now arched forward over my clasped hands.
Staring at the fire, I clearly pictured
Human bodies I had once seen burned.
My kindly escorts turned in my direction,
And Virgil said to me, "My son, there may
Be suffering here, but there can be no death.
(Purg. XXVII, 7-21)
Despite Virgil's reassurances, Dante is terrified of going through the fire. When Virgil does convince him to go through, it is only with Virgil reminding Dante that it is only by going through the fire that Dante can see Beatrice again.
It's interesting, I think, that this last penance is one suffered at least briefly by every single soul, and which Dante himself (who has not yet actually been subjected to any punishments or penances in his journey through the afterlife) too must suffer from the flames that purge away lust. Lust is, after all, one of the most basic of human sins, and is found admixed in even the most virtuous married relationships. While it was not through sexual sin that Adam and Eve fell, the first sign of their fall was when they realized that they were naked, and became ashamed. As John Paul II pointed out, writing 700 years after Dante, the first result of the fall was that Adam and Eve each realized that they were capable of taking sexual advantage of the other, and as such sought to protect themselves from each others' gaze.
At last, Dante follows Virgil into the fire.
At that he shook his head and said, "What’s this?
You’d have us stay on this side?" Then he smiled,
As one does at a child won by an apple.
Then he stepped in the flames ahead of me,
Requesting Statius, who a long way now
Had walked between us, to approach behind.
Once in the fire, I would have flung myself
Into molten glass to feel cooled off,
The burning heat inside was so intense.
My tender father, trying to comfort me,
Kept talking about Beatrice as we walked,
Saying, "I seem to see her eyes already!"
A singing voice, beyond, was guiding us;
And we, while listening all the time to it,
Came outside at the point which starts to climb.
(Purg. XXVII, 43-57)
Dante finds himself now on the ascending stair from this last terrace of penance. However, sunset and darkness falls on the poets, and they are forced to take their rest on the steps, spending one last night in Purgatory.
Taking one more moment on this last terrace of purgation, in which Dante share (however briefly) in the redemptive suffering, the contrast between the punishments of Purgatorio and Inferno strikes me yet again. Though Dante certainly gives us a powerful image of the heat (wishing he could throw himself into molten glass to cool himself) he spends far more time on his effort to gain the strength of will to enter the fire, and to keep moving through it. No one will push Dante into the fire. While in the Inferno demons, fellow sinners and other keepers constantly force the damned back into their punishments, and capture them if they try to escape, the "punishments" of the Purgatorio are all voluntarily assumed. Dante could, should he have chosen, waited indefinitely on the terrace, refusing to enter the fire.
Climbing a mountain really is the ideal metaphor for Purgatory and for the efforts at spiritual and moral self improvement in life which Purgatory, in Dante' and the reader's earthly lives, represents. It is a difficult task requiring effort and at times suffering, but undertaken because one knows and desires the goal.
No one is going to do anything to these penitents in Purgatory, but they choose to undergo these sufferings because they know that only through the purgation of disordered habits and loves can they reach the promised goal of heaven.
The translation and notes of James Finn Cotter
The translation, original text, and notes provided by AllenMandelbaum
And most especially the translation and extensive commentary by Dorothy Sayers, which Penguin keeps appearing to drop, but never quite has.