Who exactly was the dark-feathered god of love? The insights this masterpiece reveals about the rebellious artist

A youthful lad cries out as his skull is forcefully held, a massive digit digging into his face as his father's mighty hand grasps him by the neck. This scene from The Sacrifice of Isaac appears in the Uffizi Gallery, creating unease through Caravaggio's harrowing portrayal of the suffering youth from the biblical account. It appears as if the patriarch, commanded by the Divine to kill his son, could snap his spinal column with a solitary turn. Yet the father's chosen approach involves the silvery steel knife he holds in his other hand, prepared to cut the boy's throat. A definite element remains – whoever posed as Isaac for this astonishing work demonstrated remarkable acting skill. Within exists not only dread, shock and pleading in his shadowed gaze but also profound grief that a protector could betray him so completely.

The artist adopted a familiar scriptural story and transformed it so fresh and raw that its terrors seemed to unfold directly in view of you

Viewing before the painting, viewers recognize this as a actual face, an precise depiction of a adolescent subject, because the same boy – recognizable by his disheveled hair and nearly black pupils – features in several additional paintings by Caravaggio. In each instance, that highly emotional visage dominates the scene. In Youth With a Ram, he gazes mischievously from the shadows while embracing a ram. In Amor Vincit Omnia, he smirks with a hardness learned on Rome's streets, his black plumed wings sinister, a unclothed child running riot in a well-to-do residence.

Victorious Cupid, presently exhibited at a London gallery, constitutes one of the most embarrassing masterpieces ever painted. Observers feel totally disoriented gazing at it. The god of love, whose arrows inspire people with often painful longing, is shown as a extremely real, vividly illuminated unclothed figure, straddling overturned items that comprise stringed devices, a musical score, plate armor and an architect's T-square. This heap of possessions resembles, deliberately, the mathematical and architectural equipment strewn across the floor in the German master's print Melancholy – save here, the gloomy disorder is caused by this grinning deity and the mayhem he can release.

"Love sees not with the vision, but with the soul, / And thus is winged Love depicted blind," penned the Bard, just prior to this painting was created around 1601. But the painter's god is not blind. He gazes directly at you. That face – sardonic and ruddy-cheeked, staring with bold confidence as he struts naked – is the same one that screams in terror in The Sacrifice of Isaac.

As the Italian master created his three images of the same distinctive-looking youth in Rome at the dawn of the 17th century, he was the most acclaimed religious artist in a city enflamed by religious renewal. Abraham's Offering reveals why he was commissioned to adorn sanctuaries: he could take a scriptural narrative that had been portrayed many times before and make it so new, so raw and physical that the terror seemed to be happening directly before you.

Yet there existed a different aspect to the artist, evident as soon as he arrived in the capital in the cold season that ended the sixteenth century, as a artist in his initial 20s with no mentor or patron in the urban center, only talent and boldness. Most of the works with which he captured the sacred metropolis's eye were everything but devout. What could be the very first hangs in London's National Gallery. A youth parts his red mouth in a scream of agony: while stretching out his filthy fingers for a fruit, he has instead been attacked. Youth Bitten by a Reptile is sensuality amid squalor: observers can discern the painter's gloomy chamber reflected in the cloudy waters of the glass vase.

The boy sports a rose-colored blossom in his coiffure – a symbol of the erotic commerce in Renaissance art. Venetian painters such as Tiziano and Palma Vecchio depicted courtesans grasping blooms and, in a work lost in the WWII but documented through photographs, the master portrayed a renowned female prostitute, clutching a bouquet to her chest. The message of all these floral indicators is clear: intimacy for sale.

What are we to make of Caravaggio's sensual portrayals of youths – and of a particular adolescent in particular? It is a inquiry that has split his commentators ever since he gained widespread recognition in the twentieth century. The complicated past reality is that the painter was not the homosexual icon that, for instance, the filmmaker put on film in his twentieth-century movie Caravaggio, nor so completely devout that, as some artistic historians improbably claim, his Youth Holding Fruit is actually a portrait of Christ.

His early works do make overt sexual suggestions, or including offers. It's as if Caravaggio, then a penniless youthful creator, identified with the city's prostitutes, selling himself to live. In the Florentine gallery, with this idea in mind, viewers might turn to another early work, the sixteenth-century masterwork the god of wine, in which the god of alcohol stares calmly at you as he begins to untie the dark sash of his garment.

A several years following the wine deity, what could have driven Caravaggio to create Amor Vincit Omnia for the art patron Vincenzo Giustiniani, when he was at last becoming nearly respectable with important church projects? This profane non-Christian deity revives the erotic challenges of his early paintings but in a more intense, uneasy way. Fifty years afterwards, its hidden meaning seemed obvious: it was a portrait of the painter's companion. A British visitor viewed Victorious Cupid in about 1649 and was informed its subject has "the body & face of [Caravaggio's|his] owne youth or assistant that slept with him". The name of this boy was Cecco.

The artist had been dead for about forty years when this account was documented.