These wretched ones, who never were alive, went naked and were stung again, again by horseflies and by wasps that circled them. The insects streaked their faces with their blood, which, mingled with their tears, fell at their feet, where it was gathered up by sickening worms. (Inf. III, 64-69)
The neutrals are, arguably, the least natural of all the sinners, because they "never were alive" or, in Dante’s definition of living, never made the fundamental human distinction between good and evil. Paralyzed by their fear, they never chose to serve either good or evil, thus missing out on both the joys and misfortunes of life. For their cowardice, Nature itself turns against them and her lowest ranks – insects – punish them.
Inferno Canto XI (the Sixth Circle: the Heretics)
[Virgil]: "From these two, art and nature, it is fitting, if you recall how Genesis begins, for men to make their way, to gain their living; and since the usurer prefers another pathway, he scorns both nature in herself and art, her follower; his hope is elsewhere." (Inf. XI, 106-111)
Following the train of the thought from the last few lines, Virgil arrives at what is natural or good for men to do with their lives: to "make their way, to gain their living." In other words, it is good for man to work and to gain his living by the sweat of his brow, the depth of his mind, the creation of his hands. Usurers violate this natural order by growing fat off man’s greed for money instead of winning their bread through honest work. Thus, usury is a sin against nature.
[Virgil]: "Philosophy, for one who understands, points out, and not in just one place," he said, "how nature follows – as she takes her course – the Divine Intellect and Divine Art; and if you read your Physics carefully, not many pages from the start, you’ll see that when it can, you art would follow nature, just as a pupil imitates his master; so that your art is almost God’s grandchild." (Inf. XI, 97-105)
Virgil explains a central concept in Dante’s vision of Christianity: the Divine is natural, since "nature follows…the Divine Intellect and Divine Art." Man’s instinct is to follow nature and thus follow God. Consequently, anything made by man’s art is usually natural and thus somewhat like "God’s grandchild" (if man is God’s child). As a rule, then, anything that goes against nature inherently goes against God or, in other words, sins.
Inferno Canto XII (the Seventh Circle, First Ring: the Violent against their Neighbors)
[Virgil to Dante]: "But fix your eyes below, upon the valley, for now we near the stream of blood, where those who injure others violently, boil." (Inf. XII, 46-48)
Because Dante ultimately sees violence as a distortion of nature, the landscapes of the Seventh Circle feature some twisted aspects of nature. Here, the boiling river that tortures the tyrants does not flow with water, but with blood. Thus, the violent are punished by natural forces which have been fundamentally perverted.
Inferno Canto XIII (the Seventh Circle, Second Ring: The Violent against Themselves)
No green leaves in that forest, only black; no branches straight and smooth, but knotted, gnarled; no fruits were there, but briers bearing poison. Even those savage beasts that roam between Cecina and Corneto, beasts that hate tilled lands, do not have holts so harsh and dense. (Inf. XIII, 4-9)
In the ring where the suicides reside, not even nature’s growing flora can flourish. Here, trees and plants that normally sprout in healthy shades of green rot to black and do not sprout nourishing fruits, but poisoned thorns. The reference to the living "beasts" between "Cecina and Corneto" implies that even these savage creatures could not survive in such a place. Nature decrees that nothing can live and grow in a place where men have taken their own lives.
Inferno Canto XIV (the Seventh Circle, Third Ring: The Violent against God)
Above that plain of sand, distended flakes of fire showered down; their fall was slow – as snow descends on alps when no wind blows. Just like the flames that Alexander saw in India’s hot zones, when fires fell, intact and to the ground, on his battalions, for which – wisely – he had his soldiers tramp the soil to see that every fire was spent before new flames were added to the old; so did the never-ending heat descend; with this, the sand was kindled just as tinder on meeting flint will flame – doubling the pain. (Inf. XIV, 28-39)
The environment designed for punishing blasphemers perverts nature by raining fire, instead of snowflakes, to the ground. So instead of bringing relief to the sandy desert and allowing things to grow, the fiery rain increases the heat, making it eternally uncomfortable for the sinners trapped there.
Inferno Canto XIX (the Eighth Circle, Third Pouch: Simonists)
[Dante to Pope Nicholas III]: "I’d utter words much heavier than these, because your avarice afflicts the world: it tramples on the good, lifts up the wicked. You, shepherds, the Evangelist had noticed when he saw her who sits upon the waters and realized she fornicates with kings, She who was born with seven heads and had the power and support of the ten horns, as long as virtue was her husband’s pleasure. You’ve made yourselves a god of gold and silver; how are you different from idolaters, save that they worship one and you a hundred?" (Inf. XIX, 103-113)
In condemning the simonists, Dante paints their practices as highly perverted and unnatural. Here, "she who was born with seven heads" is pagan Rome, blessed by seven heads (representing the seven sacraments) and supported by "ten horns" (the ten commandments). Dante’s message: the Catholic Church (represented by the female Rome) only has power as long as her rich husbands, the "kings" with whom she "fornicates," decide to remain virtuous. When they disagree with the Church, they withdraw their financial support and the Church loses influence. To emphasize the Church’s corruption, Dante pictures her as a hideous monster with a writhing gaggle of seven heads, ten horns, and the rampant lust to "fornicate" with any rich man who comes her way. Not only does this undermine the spiritual purity for which the Church stands, degrading God to a material idol of "gold and silver," but also usurps the natural order of good over evil. As Dante puts it, such simony – the selling of the Divine Word for gold and silver – "tramples on the good" and "lifts up the wicked."
Inferno Canto XX (the Eighth Circle, Fourth Pouch: Diviners, Astrologers, and Magicians)
As I inclined my head still more, I saw that each, amazingly, appeared contorted between the chin and where the chest begins; they had their faces twisted towards their haunches and found it necessary to walk backward, because they could not see ahead of them. (Inf. XX, 10-15)
For claiming the superhuman (and thus unnatural) power of seeing the future, the magicians, diviners, and astrologers are subjected to an inversion of their natural form. Their faces, instead of gazing forward, are reversed on their shoulders so that they must face and walk backwards. Their sight has literally been reversed so that their sense of direction (and, possibly, time) is backwards.
Inferno Canto XXVI (the Eighth Circle, Eighth Pouch: the Fraudulent Counselors)
[Ulysses]: "And I and my companions were already old and slow, when we approached the narrows where Hercules set up his boundary stones that men might heed and never reach beyond; upon my right, I had gone past Seville, and on the left, already passed Ceuta. ‘Brothers,’ I said, ‘o you, who having crossed a hundred thousand dangers, reach the west, to this brief waking-time that still is left unto your senses, you must not deny experience of that which lies beyond the sun, and of the world that is unpeopled. Consider well the seed that gave you birth: you were not made to live your lives as brutes, but to be followers of worth and knowledge.’" (Inf. XXVI, 106-120)
Ulysses’ words, however inspiring, urge men to reach further and achieve more than mankind, by nature, can accomplish. By bypassing the Pillars of Hercules, Ulysses’ crew transgresses the boundaries of the known world and passes into the unknown realm where mortal realms end. As if this did not exceed man’s natural boundaries and violate God’s will enough, Ulysses spurs his men to "experience…that which lies beyond the sun" in the name of "worth and knowledge." But like Nimrod’s tower of Babel and Icarus’ flight, Ulysses’ pioneering arrogantly assumes that man can reach God’s level and is thus sinful. For exceeding his nature, God punishes Ulysses by killing him and his whole crew.
Inferno Canto XXIX (the Eighth Circle, Tenth Pouch: the Falsifiers of Metals)
[Capocchio to Dante]: "…see that I’m the shade of that Capocchio whose alchemy could counterfeit fine metals And you, if I correctly take your measure, recall how apt I was at aping nature." (Inf. XXIX, 136-139)
Though the concept of alchemy – changing other metals into gold to enhance one’s wealth – seems beneficial to mankind, it violates the stable nature of the material world. By changing one substance into another, man is imposing his art on nature and mutating it to serve his selfish ends. Such is the crime of alchemy. But what is interesting is that Capocchio relates his sinful practice to Dante’s profession, writing. He implies that writing, like alchemy is just as "apt…at aping nature." This is very true since nothing is easier to change than the flow of words and one’s verbal or textual description of something in the material world, thereby rendering language potentially as invalid as alchemy. In one of the most frightening moments of the Inferno, the legitimacy of poetry (and language in general) is called into question. This sets up one of the crucial questions of the Inferno: is writing a legitimate (or natural) art? And, if not, is one justified in using such an art for Divine justice, as Dante is doing?