Leonardo Da Vinci

Ludovico Sforza, also known as Il Moro, was the Duke of Milan and Leonardo’s most influential and enduring patron. Their relationship, which spanned nearly two decades beginning in 1482, provided Leonardo with courtly stability, resources, and an environment rich in intellectual exchange. Leonardo initially approached Sforza with a letter touting his abilities not as a painter but as a military engineer—a bold move that aligned with Sforza’s ambitions to fortify Milan’s power and prestige.

Under Sforza’s patronage, Leonardo conceived some of his most ambitious (if unfinished) projects, including the massive equestrian monument to Sforza’s father, which was ultimately destroyed during French invasions. He also painted The Last Supper during this period, designed elaborate court entertainments, and developed his anatomical, hydraulic, and architectural studies. Sforza valued Leonardo’s wide-ranging talents and gave him a unique kind of creative freedom that few artists of the time enjoyed.

Sforza’s political downfall—culminating in the French conquest of Milan in 1499—marked a turning point in Leonardo’s life. The collapse of their patronage relationship underscores a recurring theme in the biography: the fragility of artistic ambition in the face of shifting political power. Yet even after Sforza’s fall, the years Leonardo spent in Milan remained among his most fruitful and formative.

Gian Giacomo Caprotti, better known by his nickname “Salai” (meaning “Little Devil”), was Leonardo’s longtime companion, assistant, and probable lover. Leonardo first took Salai into his household at age 10, and the two remained closely connected for more than two decades. Salai appears frequently in Leonardo’s notebooks, sometimes as the subject of affectionate portraits, other times as the recipient of grumbling notes about theft and mischief. Their relationship was turbulent but enduring, characterized by a blend of exasperation and deep attachment.

Salai’s physical appearance—youthful, androgynous, and often erotically charged—influenced Leonardo’s ideal of beauty and may have served as the model for figures in paintings such as Saint John the Baptist and Bacchus. Isaacson explores how Salai came to represent both Leonardo’s aesthetic sensibility and his emotional complexity, functioning almost as a muse, even when he seemed personally unreliable.

While Salai never demonstrated exceptional artistic talent of his own, his presence in Leonardo’s life helps illuminate aspects of Leonardo’s personal world—his sexuality, his domestic arrangements, and his capacity for loyalty despite disappointment. Salai eventually inherited some of Leonardo’s works, including the Mona Lisa, suggesting the depth of their connection and the trust Leonardo placed in him despite years of frustration.

Francesco Melzi was a young nobleman who became Leonardo’s final and most devoted assistant, student, and heir. Unlike the impish Salai, Melzi was well-educated, respectful, and intellectually inclined, forming what many scholars see as a father-son or mentor-protégé relationship with Leonardo. They met around 1506 during Leonardo’s second Milanese period, and Melzi accompanied him to France, remaining by his side until his death in 1519.

Melzi’s importance lies not only in his companionship but in his role as steward of Leonardo’s legacy. After Leonardo’s death, Melzi inherited his notebooks, drawings, and personal effects, dedicating years to preserving, cataloging, and studying them. He was instrumental in compiling what would eventually become the Treatise on Painting, ensuring that Leonardo’s insights—many of which went unpublished in his lifetime—were not lost to history.

In Isaacson’s portrayal, Melzi represents the ideal pupil: devoted, orderly, and intellectually engaged. His presence offers a counterbalance to Salai’s chaos and a glimpse into the emotional warmth that Leonardo, often perceived as aloof or eccentric, was capable of inspiring. Melzi’s efforts also raise questions about legacy, authorship, and the challenges of preserving genius for future generations.

Andrea del Verrocchio was a prominent Florentine artist and sculptor under whom Leonardo began his formal apprenticeship. Verrocchio’s workshop, one of the most respected in Florence during the late 15th century, was a commercial and collaborative space where apprentices learned multiple disciplines—drawing, painting, sculpting, metalwork, and engineering. For Leonardo, this environment became the first structured arena in which his talents were recognized, nurtured, and refined.

Verrocchio offered Leonardo foundational training not only in technique but also in the spirit of Renaissance interdisciplinarity. It was likely in this studio that Leonardo developed his initial interest in mechanical systems, anatomy, and theatrical spectacle, all of which would later define his notebooks and creative output. Leonardo is believed to have contributed to several of Verrocchio’s works, including Baptism of Christ, where his rendering of an angel’s face and the surrounding landscape already displayed a grace and realism that surpassed his master’s.

Isaacson presents Verrocchio not just as a mentor, but as a formative influence who helped set Leonardo on a lifelong path of observation and experimentation. Their relationship illustrates how Renaissance talent was shaped not only by individual brilliance, but also by shared workshops, collaborative learning, and artistic lineage.

Lisa del Giocondo, née Gherardini, was the Florentine woman believed to be the subject of Leonardo’s Mona Lisa—arguably the most famous painting in the world. Married to a wealthy silk merchant, Francesco del Giocondo, Lisa was around 24 years old when Leonardo began the portrait in 1503. Though the painting was likely commissioned, Leonardo never delivered it, instead refining and reworking the portrait for years and keeping it with him until his death.

Isaacson uses Lisa as a touchpoint for Leonardo’s broader intellectual and artistic concerns. In Mona Lisa, Leonardo fuses his interests in optics, anatomy, psychology, and natural landscape into a single image. Lisa’s famously enigmatic smile becomes a symbol not only of aesthetic mastery, but also of inner life—animated by muscles Leonardo had studied in his anatomical dissections and bathed in sfumato, his signature technique of smoky shading and soft transitions.

While little is known about Lisa herself, her image serves as a vessel for Leonardo’s evolving vision of portraiture—not as mere likeness, but as a profound meditation on human complexity. Her presence in the biography underscores Leonardo’s ability to elevate a private, domestic commission into an eternal icon of artistic and philosophical mystery.

Cesare Borgia, the ruthless and charismatic son of Pope Alexander VI, briefly employed Leonardo as a military engineer during his brutal campaign to consolidate power in central Italy. In 1502, Leonardo joined Borgia’s retinue and traveled across Romagna, inspecting fortifications, sketching maps, and designing tools of war—including bridges, defensive walls, and possibly an early odometer.

Isaacson portrays this period as morally complex for Leonardo, who otherwise professed pacifist and vegetarian ideals. Though he rarely commented on the violence surrounding him, Leonardo’s writings from this time include moments of ethical unease—such as his plea to be spared from the “beastly madness” of war. His partnership with Borgia, who was both admired and feared for his cunning, ambition, and ruthlessness, reveals the tension between Leonardo’s scientific curiosity and the often-violent uses of his talents.

This chapter of Leonardo’s life also intersects with the rise of modern statecraft and Machiavellian realism. Indeed, Niccolò Machiavelli admired Borgia and may have crossed paths with Leonardo during this period. Leonardo’s time in Borgia’s service exemplifies the complex role of the Renaissance artist-engineer: not only a visionary, but also a tool of powerful—and often dangerous—patrons.