Illegitimacy freed him from a conventional path

Leonardo was born in 1452 out of wedlock to a notary father and a peasant mother in the Tuscan town of Vinci, a status that would ordinarily have blocked him from the university education and formal guild professions his father's class expected. Barred from the traditional path, he was instead apprenticed as a teenager to the Florentine painter and sculptor Andrea del Verrocchio.

Isaacson frames this not as a setback but as the accident that let Leonardo become who he became: rather than absorbing the rigid Latin-and-logic education of his era's elite, he learned by direct observation, apprenticeship, and workshop practice, developing an empirical, hands-on relationship with the world that his formally educated peers largely lacked.

His lack of Latin fluency, something he worked to remedy later in life, similarly kept him somewhat outside the classical scholarly tradition — and outside its assumptions, which turned out to be exactly the position from which he could question them.

Takeaway: being excluded from the standard path can sometimes force a more original one.