In his XLI letter to Lucillius, Seneca equals the sublimity of rocks to that of a virtuous man. Very likely, Seneca' Stoic simile haunted the mind of Leonardo da Vinci, when he painted the background of his Virgin of the Rocks after his first journey from Florence to Milan. The rocky backgrounds may have retained that implicit meaning for Leonardo's first Milanese fol­lowers: Boltraffio (who was also affected by Gerolamo Casio's thought) and Marco d'Oggiono. However, as the sixteenth century moved on, in the context of the Cyrenaic philosophy in the wake of Anniceris - possibly introduced from the Veneto by Andrea Solario - the sublimity adumbrated by the painted rock formations in Luini's paintings seems to suggest the sacrifice accepted by the Redeemer for the love of mankind.