Of all the insults and derogatory comparisons Dante uses in the Commedia on both lost souls and evil demons, one recurs throughout. The wrathful, according to Virgil, are all “dogs.” From then on, in his travel notes through the kingdom of the dead, Dante echoes his master’s ancient vocabulary. Thus, Dante tells us that the wasteful in the seventh circle are pursued by “famished and fast black bitches”; the burning usurers running under the rain of fire behave “like dogs who in the summer fight off fleas and flies with their paws and maw”; a demon who pursues a barrater is like “a mastiff let loose,” and other demons are like “dogs hunting a poor beggar” and crueler than “the dog with the hare it has caught.” Hecuba’s cry of pain is demeaned as a bark “just like a dog”; Dante apprehends the “doglike faces” of the traitors trapped in the ice of Caïna, the unrepentant Bocca “barking” like a tortured dog, and Count Ugolino gnawing at the skull of Cardinal Ruggiero “with his teeth,/which as a dog’s were strong against the bone.”

Angry, greedy, savage, mad, cruel: these are the qualities that Dante seems to see in dogs and applies to the inhabitants of Hell. To call a person a “dog” is a common and uninspired insult in almost every language, including, of course, the Italian spoken in Dante’s thirteenth- and fourteenth-century Tuscany. But mere commonplaces are absent in Dante: when he uses an ordinary expression, it no longer reads as ordinary. The dogs in the Commedia carry connotations other than the merely insulting, but overriding them all is the suggestion of something infamous and despicable. This relentlessness demands a question.

In Dante’s time, life in most Tuscan households continued to be relatively simple and informal. Depictions of interiors in Florence, Siena, and other Tuscan cities in the thirteenth century show sparsely furnished rooms, sometimes decorated with a few tapestries and trompe-l’oeil paintings, often with colorful vases full of flowers. Pets were common. Birds hung in cages by the window, as shown in frescoes by Masaccio and Lorenzetti. Cats snuggled up by the fireplace in the bedroom. (The Florentine Franco Sacchetti advised men rising naked from the bed to make sure that the cat wouldn’t mistake “certain pendulous objects” for playthings.) Even geese were sometimes kept indoors; Leon Battista Alberti, in Il libro della famiglia, recommends the use of geese to keep watch over one’s house. And, of course, there were dogs.

Dogs curled up at the foot of the bed or on the floor by the hearth; dogs watched by the threshold or waited for scraps under the table. Lapdogs kept the ladies company by the spinning wheel, and greyhounds waited patiently for their masters to go hunting. Brunetto Latini noted in his Livre du trésor that dogs loved humans more than did any other animals; only dogs born from the union of bitches and wolves were wicked. Most dogs were faithful unto death: it was not uncommon for dogs to guard their master’s corpse day and night, and sometimes even to die of grief. According to Latini, the dog is able to understand the human voice. A contemporary of Dante, Pierre de Beauvais, observed in his Bestiary that because dogs lick their wounds to heal them, they are like priests who hear our confessions and heal our sorrows. Isidore of Seville, in the Etymologies, explained that the dog (canis) received its name because the dog’s bark was like singing (canor) the lyrics that poets composed.

According to ancient lore, dogs are supposed to recognize angelic presences before humans can see them. The dog that accompanied Tobit’s son Tobias on the journey with the angel is one such example (and the only good dog in the whole of biblical literature). Dogs can not only be aware of the numinous; they themselves can also be saintly. In the thirteenth century, in the region of Lyon, a greyhound was venerated under the name of Saint Guignefort. According to tradition, the dog Guignefort was left to look after an infant in his cradle. A serpent tried to attack the child, and Guignefort killed it. When the master returned, he saw the dog covered in the serpent’s blood and thought that it had attacked the child. Furious, he killed the faithful Guignefort, then discovered the infant safe and sound. Vindicated as a martyr, the dog acquired the status of a saint invoked to protect children.

The only dog mentioned in the Commedia as the incarnation of positive canine qualities is the veltro, or greyhound, first announced by Virgil at the beginning of their journey and later tacitly invoked by Dante himself: the hound that will one day pursue and kill the evil she-wolf. Most commentators identify the greyhound with the emperor Henry VII of Luxembourg, much admired by Dante, who called him “the successor of Caesar and Augustus.” In any case, the greyhound is less a dog than the symbol of a hoped-for salvation, a collective or social “disio.”

Almost all of Dante’s books were written in exile, in houses that he could never consider his own because they were not in his Florence, which in his memory he loved and hated as an unfaithful mistress, both praising her for her beauty and scourging her for her sins. The incipit to his poem reveals the double bind: “Here begins the Commedia of Dante Alighieri, Florentine of nationality, not of morals.” No doubt his hosts—Cangrande, Guido Novello, and the others—were kind to him and provided him with comfortable rooms and intelligent conversation, but home was always somewhere else, the place of absence. Banned from Florence, he must have felt that the city’s gate might have been a parody of the gate of Hell: its sign would be not “Abandon all hope you who enter” but “Abandon all hope you who leave.” And yet Dante, like a whipped dog, was unable to give up all hope of returning home.

In Verona and Arezzo, Padua and Ravenna, Dante sat at his borrowed table, filled with the vision that he wished to put into words and painfully aware that like the forest of the beginning of his voyage, “to say what it was is hard” because human language, unlike a dog, is an unfaithful creature. The vast and overwhelming systems of theology, astronomy, philosophy, and poetry weighed on him and imposed their rules and tenets. Slowly, around the character that bears his name, Dante conjured up his cast: his best-beloved poet, Virgil; the object of his desire, the dead Beatrice; the men and women who inhabited his past; the pagan heroes who inhabited his books; the saints from the church calendar. Also places and scenes: remembered streets and buildings, mountains and valleys, night skies and dawns, workers in the field and in the village, shopkeepers and artisans, farm animals, wild beasts, and especially the birds that flew among the clouds of Florence—all to illustrate, as best he could, what he knew could not be put exactly into a human tongue.

Overwhelmed by the flood of remembered images, Dante may have looked down once again at the dog. As their eyes met, Dante, for whom every experience was a touchstone for another and every memory a link in an endless chain of memories, might have recalled a dog (or several dogs) that wandered through his parents’ house when he was a child, a dog that lay by his side as the five-year-old mourned his mother, and, later, another dog that kept him company as the adolescent Dante watched over the corpse of his emaciated father. A dog trotted alongside his bride four years later on the way to the church where the couple was married; a dog witnessed the birth of his first son, Giovanni; a dog sat quietly in a corner when Dante learned that the fleeting and unforgettable Beatrice Portinari had died as the wife of another man. A pack of remembered dogs: Florentine dogs, Veronese dogs, dogs of Venice and of Ravenna, dogs met on weary roads and in filthy inns, a long line of dogs slowly blending, like the changing shapes of the punished thieves in the eighth circle of Hell, from dog into dog into dog, including his host and protector, Cangrande (Big Dog) della Scala, to whom the Paradiso is probably dedicated.

Thomas Aquinas argued that after death, when the soul has left the body, since people would no longer need food, there would be no animals in Heaven. Accordingly, except for a few allegorical beasts—the eagle, the gryphon—Dante’s Paradise is devoid of animals of feather and fur. Saint Augustine (who infamously argued that animals do not suffer) suggested that, though dumb animals could not compete with the heavenly beauties, they no doubt contribute to the adornment of our earthly realm. “It would be ridiculous,” he wrote,

to regard the defects of beasts, trees, and other mutable and mortal things which lack intelligence, sense, or life, as deserving condemnation. Such defects do indeed effect the decay of their nature, which is liable to dissolution; but these creatures have received their mode of being by the will of their Creator, whose purpose is that they should bring to perfection the beauty of the lower part of the universe by their alteration and succession in the passage of the seasons; and this is a beauty in its own kind, finding its place among the constituent parts of this world.

Popular belief had it that the devil would commonly manifest itself as a “dumb, irrational creature”: a serpent, a goat, a dog. Nevertheless, several fathers of the church, such as Saint Ambrose in his Hexameron, insisted that we at least learn gratitude from dogs:

What shall I say about dogs who have a natural instinct to show gratitude and to serve as watchful guardians of their masters’ safety? Hence Scripture cries out to the ungrateful, the slothful, and the craven: “Dumb dogs, not able to bark.” To dogs, therefore, is given the ability to bark in defense of their masters and their homes. Thus you should learn to use your voice for the sake of Christ, when ravening wolves attack His sheepfold.

Though experience teaches us that most dogs are grateful servants (we expect in animals virtues often lacking in ourselves), gratitude is an aspect of dogs that appears seldom in popular stories. In the twelfth-century fables of Marie de France (which Dante probably read), only one story shows an example of a loyal dog; in all the others they are quarrelsome, envious, gossipy, and greedy. It is their greed (as commentators point out) that makes them return to their vomit. Dogs also incarnate rage: for that reason, the three-headed Cerberus of ancient mythology, placed by Dante to guard the circle of the gluttons, “claws the souls, flays and tears them to pieces.” There was a superstition in Florence that to dream of a dog, especially one nipping at your heels, was a herald of sickness or even death. Also of birth: Saint Dominic’s mother, pregnant with the future founder of the Dominican Order, dreamt of a dog carrying a burning torch in its mouth; after his death his order was charged with lighting the flames of the Inquisition.

Dante’s Commedia is one man’s vision but succeeds in being universal. Dante’s intimate experiences, his convictions, his doubts and fears, his private notions of honor and civic duty are inscribed in a system not of his making, a universe created by an unquestionable God whose terrible love allows the poet an ineffable glimpse of his creation, identical to God’s own tripartite person. Dante must choose from the vast mass of experience, and leave aside certain inspiring and illuminating realities. Nowhere in the Commedia are his wife or his children, for example, and these are only a couple of the deliberate absences in a poem that is supposed to hold the poet’s whole world. And among the experiences Dante left out, regrettably, is that of the companionable dog.

And yet, not the dog itself but a knowledge of something kind and generous and loyal for which the dog is responsible, something that tries to understand and to follow and to obey, surfaces from time to time in the Commedia. From the first canto of Inferno to the twenty-seventh canto of Purgatorio, Dante the protagonist is guided and protected by Virgil, who within the limited capacities of one enlightened not by faith but by intellect teaches his ward to trust his reason, use his memory, and lend meaning to his love. To guide and protect are duties traditionally fulfilled by dogs, but here, in the relationship forged between the lost Christian poet and the poet of ancient Rome, it is the guided one, Dante, who behaves like an errant beast, one of those hounds of Venus that incarnate his disio. And the one who fulfills the guardian functions is Virgil, “my master,” as Dante calls him from the start.

High on Mount Purgatory, on the threshold of the Earthly Paradise, shortly before their leave-taking, Dante describes himself as a goat kept by Virgil the goatherd. “Goat” fits the bucolic scene, but Dante could also have called himself Virgil’s hound because throughout their long and perilous journey, it was always Virgil who gave the orders, Virgil who pronounced the right word or made a clear sign, Virgil who praised or reproved Dante’s judgment and actions, Virgil who, so to speak, “owned” Dante, having been charged by Beatrice with looking after him until he could be delivered into the holy presence. Virgil’s last words to Dante before parting are those a trainer might address to a well-brought-up dog: “Don’t wait again for my word or my sign; your judgment is now free, straight and healthy.” Dante, who now knows how to behave, enters “the divine grove” of Eden, of which the ancient poets sang when they spoke of the Golden Age. Like the faithful, loving creature he has become, Dante looks once more at his master, who has remained smiling at the grove’s edge, and then he turns obediently towards a beautiful lady who will lead him on to his new, expectant mistress.

The Commedia is a poem of evidences and almost invisible subtleties, of explicit and implicit connotations, of orthodox theology and subversive exegesis, of rigorous hierarchies and leveling companionships. To construct its unimaginable edifice, words are borrowed from every available vocabulary, from Latin and Provençal, from common speech and neologistic poetry, from archaic discourse and children’s babble, from scientific jargon and the language of dreams—words stripped of their original function and yet echoing ancestral connotations, made to serve and reveal themselves in an almost endless plurality of meaning. Nothing in the Commedia is only one thing. Much as the dark wood is not only a wood, Dante is not only Dante, the dog used to curse the wicked is not only the wicked dog: it is also the poem’s hero, the pilgrim poet Dante himself, lost like a stray dog in a wild and threatening wood. From the first lines of the Commedia (the readers suddenly realized with amazement) the dog at Dante’s feet, in all its poetic essence, has surreptitiously entered the poem.

Adapted from a chapter of Alberto Manguel’s Curiosity, to be published by Yale University Press on March 17.