This lecture explores the paintings of Andrea del Sarto, known to his contemporaries as Andrea senza errori (Andrea without errors). Celebrated for his flawless draftsmanship and soft, atmospheric coloring, he was the influential teacher of the first generation of Mannerists. His renowned Madonna of the Harpies, housed in the Uffizi Gallery, is analyzed in detail to understand the peak of Florentine classical balance before its dissolution.