[T]he third ring [of Hell's seventh circle is] where he pictures the torments of the violent against Divinity. Just as violence can be committed in three ways, this form of violence is likewise divided in three: blasphemy, unnatural sex acts, and usury.
He pictures the mortal sinners—blasphemers, sodomites, and brute fornicators—crisscrossing a field like the sandy plain of Libya trod by Cato. From his station at the edge of this field, or its outer banks, he says it is showered with flames like those Alexander witnessed raining on his army, which he and his armed battalions took care to smother. These flames represent the thoughts and impulses that fire up such infamies as the three sins under discussion here.
One blasphemer he mentions is Capaneus the king, who together with kings Adrastus, Tydeus, Polynices, Amphiaraus, Hippomedon, and Parthenopaeus went against Eteocles, king of Thebes, and mounted a seige against his city. The arrogance of Capaneus was so outsized that he railed against the gods as if they were men, above all Bacchus, god of Thebes. For this he was struck down and killed by Jove amid the fray, about which Statius says:
Here then was Capaneus in a towering passion for war
[....] a confirmed hater of the gods, and of justice
Against such blasphemers, David says [in Psalm 18 / II Samuel 22]: "Hail and coals of fire shot through the clouds that screened the brilliance in His glare [....] He sent His arrows out, and scattered them; He multiplied His bolts of lightning, and threw them into panic." And John in the second chapter of his letter [Nicholas Trevet in his commentary on Boethius's Consolation of Philosophy, 1.M4] says: "Persecution of the haughty is symbolized by a bolt of lightning, because hauteur, like lightning, originates on high." Blasphemy is a sin against the Holy Ghost, for which reason God in Leviticus says to Moses: "The man who curses his god shall bear his sin."
Capaneus's speech "If Jove should" etc. is a poetic expression of his hubris. His words about Jove's blacksmith, Vulcan, and how Jove pleads with him, engage the idiom in which Vulcan is poetically called the god of smiths, since no smith can forge metal without fire. It is said that Vulcan was born from Juno's thigh, and that he was hurled out of heaven by reason of his deformity, and landed on the island of Lemnos, which explains why he is called Lemnius. They say he was born of Juno's "thigh" because [air is Juno's realm, and] lightning is birthed from the bottom of the air. Thus says Lucan:
Lightning sets ablaze the air that's closest to the earth
[Fire] is called by the triple name of Jupiter, Vulcan, and Vesta. Jupiter is the ethereal fire abiding in its own sphere, where it is simple and harmless. Vulcan is the lightning, the middle fire that causes harm, by which Vulcan might be construed as "The Devouring Brilliance" (vorans candor > *Vorcan > Vulcan). And Vesta is the fire whose closeness we enjoy.
[Capaneus boasts that] if Vulcan and all the smiths of Aetna, whom the poets call Cyclopes or Telchines, were to blast him with their lightning, as at the battle of Phlegra, it would be futile. Phlegra is the site of the Gigantomachy, in or around Thessaly. If not for Vulcan and his smiths who munitioned Jove with lightning bolts and arrows, the Giants would have defeated him there. Statius mentions this battle in book two:
Exactly thus did giant Briareus stand against
the arms of Heaven, if you believe in Phlegra of the Getae
From Pietro Alighieri's Commentary on the Comedy of his Father Dante
(Inferno XIV.7–72)
