Pico based his ideas chiefly on Plato, as did his teacher, Marsilio Ficino, but retained a deep respect for Aristotle. Although he was a product of the "studia humanitatis", Pico was constitutionally an eclectic, and in some respects he represented a reaction against the exaggerations of pure humanism, defending what he believed to be the best of the medieval and Islamic commentators, such as Averroes and Avicenna, on Aristotle in a famous long letter to Ermolao Barbaro in 1485. It was always Pico's aim to reconcile the schools of Plato and Aristotle since he believed they used different words to express the same concepts. It was perhaps, for this reason, his friends called him "Princeps Concordiae", or "Prince of Harmony" (a pun on Prince of Concordia, one of his family's holdings). Similarly, Pico believed that an educated person should also study Hebrew and Talmudic sources, and the Hermetics, because he thought they represented the same concept of God that is seen in the Old Testament, but in different words.