Execrable as literature and malevolent as propaganda, Dan Brown’s Inferno cannot help but be merely the latest in a long line of books to pay homage to the original Inferno of Dante Alighieri (1265-1321). The millions who immerse themselves in the sick fantasies of the New Hampshire schlockmeister may never have heard of the Florentine poet, still less have read the Divine Comedy, but we all inhabit the mental world Dante foreshadowed and did so much to make possible — the world in which free individuals pursue their own happiness as they see fit. Dante stands for suffering humanity, created in the image of God. It is no accident that he is the first writer in history whose features — austere, aquiline and cadaverous — are instantly recognisable. Just as his face is a literary gestalt, his life is the archetype of literary biography. It emerges in his Vita Nuova, the “new life” in prose and poetry that marks his ecstatic discovery of love, the force “that moves the sun and the other stars”. His paean there to “benedetta Beatrice” is the source from which every later lover has unconsciously drawn inspiration when praising his or her beloved.

In Dante, the medieval mind encountered modernity. He had studied in Paris, the leading university of the 13th century, and he was abreast of the most advanced science and philosophy of his day. But Dante’s determination to think for himself landed him in trouble with the Church. His life coincided with the high tide of papal megalomania, when Boniface VIII declared in his bull Unam Sanctam of 1302 that “it is absolutely necessary for salvation that every human creature be subject to the Roman pontiff”.

Dante, who belonged to the pro-imperial Ghibelline party, wrote a Latin treatise, De Monarchia, which proved to his satisfaction that “the temporal Monarch derives his authority directly, and without intermediary, from the Source of all authority”, namely God, not the Pope. In his polemic, however, Dante speaks of universalis civilitas humani generis, “the whole process of human society”, which the French medievalist Etienne Gilson regards as the invention of the idea of humanity.

The Florentines did not take kindly to Dante’s idealistic interventions in politics, and he was banished for life. His De Monarchia attracted the attention of the inquisitorial Dominicans, and it was placed on the Index of Forbidden Books. (Dante’s revenge was to damn Boniface for his corruption.)

After a decade of peripatetic exile, traversing “almost all of Italy”, Dante died in Ravenna, soon after completing the Divina Commedia, the magnum opus which immediately elevated him above all his contemporaries. It was the first “modern classic”, the first vernacular work to belong to a “canon” of European literature. At the beginning of the Inferno, his journey into the depths of Hell, Dante is introduced by his guide, Virgil, to the shades of Homer, Ovid, Lucan and Horace, who accept the newcomer as their peer. Immodest? Possibly, but without this unshakeable self-confidence, Dante could never have demonstrated that Italian — and, by extension, other vernacular tongues — were just as capable of linguistic excellence as Latin and Greek. Thus Dante opened the door, not only for his countrymen to create a self-consciously literary culture, but for Shakespeare to occupy the same role in English literature.

Yet Dante’s status as the man who ennobled the Italian language obscured his even greater achievement, as the man who ennobled humanity itself. His vision of cosmic justice was overtaken by the eroticism of Boccaccio, who was given a chair to comment on the Divine Comedy. From the Renaissance to the Enlightenment, he was little read. Rediscovered by the Romantics, who shared his sense of the sublime, if not his theology, Dante became the darling of the Victorians.

What made him popular even, or especially, among the newly educated classes, were the illustrations of Gustave Doré. Big and bold, dark and dramatic, these steel engravings impressed themselves on the Anglo-Saxon imagination more vividly than the orotund accompanying translation by the Revd Francis Cary. Such images of grand guignol as “Mahomet mangled” in the ninth circle of Hell, reserved for schismatics, were the Victorian equivalent of the film of the book. Anticipating the gothic horror of Hollywood is Doré’s evocation of a celebrated passage where the heretic Farinata rises from his fiery tomb to warn Dante that he will be exiled from Florence. It could be Boris Karloff.

Is Dante underrated today? His memory has been kept alive by poets, among them T.S. Eliot, scholars such as Ernst Robert Curtius or Erich Auerbach, and most recently a biography by A.N. Wilson. The secular world may have fought shy of Dante’s devout, if idiosyncratic, Christianity, but those who don’t read his Inferno are missing out on a great book. After eight centuries his laurels are secure, but his spirit knows no rest. What advice would his shade give to the reader of Brown’s Inferno? “Abandon all hope, ye who enter here.”