Botticelli and Treasures from the Hamilton Collection, Courtauld Gallery

In Hell, the souls of the damned endure cruelly imaginative punishments for all eternity. Corrupt churchmen are buried headfirst in the ground with their feet set on fire, and soothsayers, who in life presumed to be able to see into the future, have their heads turned 180 degrees and are forced to walk around looking backwards. Drawn in metalpoint strengthened here and there with ink, Botticelli’s lines are as fine as spider’s silk.

Sometimes barely there at all, their extraordinary refinement lends a strange, jarring intensity to the violence and terror they depict. By contrast, their ethereal quality is aptly evocative of the dreamlike state in which Dante undertakes his journey through the afterlife, and the progressively more abstract nature of his narrative.

Spanning a vast emotional, technical and narrative range, this selection of sheets from Botticelli’s most ambitious and enigmatic work, the illustrations for Dante’s Divine Comedy represent an absolute embodiment of Renaissance achievement. Vasari’s brief but evocative description of an artist obsessed with a project, “on which he [Botticelli] wasted much of his time, bringing infinite disorder into his life by neglecting his work” appeals to the Renaissance conception of the artist as an individual creative genius, and Botticelli seems to have laboured for some 15 years to bring the drawings to a state of not even near-completion.

For all their lack of completeness, the drawings serve as an exemplar of that strangely slippery term disegno. Popularised by Vasari, its meaning goes beyond draughtsmanship to encompass design, demonstrated here in the accomplished way that Botticelli wrestles Dante’s complex, epic poem into a coherent visual translation that remains remarkably faithful to its source. 

Throughout the series, Botticelli depicts the human figure in endlessly varied poses and emotional states, with certain sheets, like Inferno XXXIII in which the souls of the treacherous are frozen into myriad contorted poses, providing particularly rich opportunities for Botticelli to exploit. But this isn’t just about showing off: Botticelli’s ability to convey the expressive capabilities of the body give the drawings immense narrative power (pictured above: Punishment of the corrupt in the eighth circle, Divine Comedy, Inferno XXII, c.1481-1495).  

In one of the first sheets seen here, Inferno XVII, Dante clings to his guide, the Roman poet Virgil, as they descend into the abyss on the back of Geryon, a chimeric monster with a man’s head and a scorpion’s tail. At one point Dante’s face is almost completely obscured, but his hunched, shrinking shoulders are a compelling depiction of pure terror.

The encounters between Dante and his beloved Beatrice are perhaps the most complex in the series, and their conversations are made visually eloquent by the careful positioning of their bodies (main picture: Dante and Beatrice in the second planetary sphere of Paradise, Divine Comedy, Paradiso VI, c.1481-1495). In several places you can see how Botticelli adjusted position or gaze, and these pentimenti give some insight into how the expressive capacity of the body is used to convey complex narrative passages.

One of the more curious aspects of the drawings is Botticelli’s decision to use multiple representations of Dante and Virgil, in order to show narrative trajectory. It seems an archaic, almost medieval device and yet simultaneously it evokes modern techniques and genres like stop-motion animation, for instance, or the cartoon strip.

The analogy of a cartoon strip gains force in the very few sheets that have been coloured. Sadly, none of these are on display here, and although most commentators including the late, great Kenneth Clark, thought it a blessing that most of the surviving 92 sheets remain as simple line drawings, those that have been coloured clearly show how the figures of Dante and Virgil might have served as route markers, plotting their progress through the chaotic topography of Hell and Purgatory.

The omission of the coloured sheets removes an intuitive link between Botticelli’s Divine Comedy and the illuminated manuscripts on display here, which provide a wider context for Botticelli's series beyond our admiration for them as virtuoso drawings. (Pictured above left: a page from The Romance of Alexander, c.1290-1300.)

Dating from the late 15^th century, Botticelli’s Dante belongs firmly to the era of the printed book. Drawn on translucent vellum, the text on the back of each sheet shows through as a constant reminder that we are looking at, first and foremost, an extraordinarily ambitious and luxurious book, commissioned by Botticelli’s patron Lorenzo di Pierfrancesco de' Medici.

While the spread of the printing press made texts and books more widely available than ever before, the result was a boom period for the art of manuscript illumination. For Europe’s elite, unique, lavishly decorated books produced by scribe and artist became particularly sought after. In this context, the array of precious books from the Hamilton Collection, amassed during the early 19^th century then sold off a couple of generations later to clear the gambling debts of the good-for-nothing 12^th Duke of Hamilton, represents the last hurrah of an essentially medieval genre, one that would soon be swept away by new technology.

• Botticelli and Treasures from the Hamilton Collection at the Courtauld Gallery until 15 May

@FlorenceHallett