What exactly was Caravaggio's dark-feathered deity of love? What secrets this masterwork uncovers about the rebellious genius

The youthful lad screams as his head is forcefully gripped, a massive thumb digging into his face as his father's mighty palm holds him by the throat. That moment from The Sacrifice of Isaac visits the Florentine museum, evoking unease through the artist's harrowing rendition of the tormented child from the biblical account. It seems as if Abraham, instructed by the Divine to kill his offspring, could snap his spinal column with a solitary turn. Yet Abraham's chosen approach involves the metallic grey knife he holds in his remaining palm, prepared to cut the boy's neck. One definite aspect stands out – whomever modeled as the sacrifice for this breathtaking piece displayed extraordinary acting ability. Within exists not only dread, shock and pleading in his darkened eyes but also deep grief that a protector could betray him so utterly.

He took a well-known scriptural story and made it so vibrant and visceral that its terrors appeared to unfold directly in view of the viewer

Standing before the artwork, viewers identify this as a real countenance, an precise record of a young model, because the same youth – recognizable by his tousled hair and nearly black pupils – features in several additional works by Caravaggio. In each case, that highly emotional visage commands the scene. In John the Baptist, he gazes mischievously from the shadows while holding a lamb. In Amor Vincit Omnia, he smirks with a hardness learned on Rome's alleys, his black plumed appendages demonic, a naked child creating riot in a affluent dwelling.

Amor Vincit Omnia, presently exhibited at a London gallery, constitutes one of the most embarrassing artworks ever created. Viewers feel completely disoriented looking at it. Cupid, whose arrows inspire people with frequently painful longing, is portrayed as a extremely real, vividly lit unclothed form, straddling toppled-over items that comprise stringed instruments, a music score, plate armor and an builder's T-square. This pile of items echoes, deliberately, the geometric and construction gear scattered across the ground in the German master's print Melencolia I – save here, the gloomy disorder is caused by this grinning Cupid and the mayhem he can unleash.

"Love sees not with the eyes, but with the mind, / And therefore is winged Cupid depicted sightless," penned the Bard, shortly before this work was created around the early 1600s. But Caravaggio's Cupid is not unseeing. He stares directly at you. That countenance – ironic and ruddy-cheeked, looking with bold assurance as he struts unclothed – is the identical one that screams in fear in The Sacrifice of Isaac.

When the Italian master created his three images of the same distinctive-looking youth in the Eternal City at the start of the 17th century, he was the most acclaimed religious painter in a metropolis enflamed by Catholic renewal. Abraham's Offering demonstrates why he was commissioned to adorn churches: he could adopt a biblical narrative that had been portrayed many occasions previously and make it so new, so unfiltered and visceral that the terror seemed to be occurring directly before the spectator.

Yet there existed a different aspect to Caravaggio, evident as quickly as he arrived in the capital in the winter that ended 1592, as a painter in his early 20s with no teacher or patron in the urban center, just skill and audacity. The majority of the paintings with which he caught the sacred city's attention were everything but holy. What may be the very first resides in the UK's art museum. A youth opens his crimson lips in a yell of agony: while stretching out his dirty digits for a fruit, he has rather been attacked. Boy Bitten By a Lizard is sensuality amid squalor: observers can discern the painter's dismal room mirrored in the cloudy liquid of the glass vase.

The adolescent sports a pink blossom in his coiffure – a symbol of the erotic trade in Renaissance art. Venetian artists such as Tiziano and Jacopo Palma depicted prostitutes holding flowers and, in a work destroyed in the WWII but documented through images, the master represented a renowned female courtesan, holding a bouquet to her bosom. The meaning of all these floral indicators is obvious: sex for purchase.

What are we to interpret of the artist's sensual depictions of youths – and of a particular boy in particular? It is a question that has split his interpreters since he achieved widespread recognition in the 1980s. The complicated historical truth is that the artist was not the queer hero that, for instance, Derek Jarman presented on screen in his twentieth-century film Caravaggio, nor so completely pious that, as certain art historians improbably assert, his Boy With a Basket of Fruit is actually a portrait of Christ.

His initial works indeed make explicit sexual suggestions, or even offers. It's as if the painter, then a penniless youthful creator, aligned with the city's prostitutes, selling himself to survive. In the Florentine gallery, with this thought in consideration, viewers might look to an additional initial creation, the sixteenth-century masterpiece Bacchus, in which the deity of alcohol stares calmly at the spectator as he begins to undo the dark ribbon of his robe.

A several annums following the wine deity, what could have driven Caravaggio to paint Amor Vincit Omnia for the artistic collector the nobleman, when he was finally growing nearly respectable with important church projects? This profane non-Christian god revives the erotic provocations of his early paintings but in a more powerful, uneasy manner. Half a century later, its secret seemed clear: it was a portrait of the painter's lover. A British visitor viewed the painting in about the mid-seventeenth century and was told its figure has "the body & face of [Caravaggio's|his] own boy or servant that laid with him". The identity of this boy was Francesco.

The painter had been deceased for about 40 years when this account was documented.