Leo the Mathematician

Leo the Mathematician or the Philosopher (Greek: Λέων ὁ Μαθηματικός or ὁ Φιλόσοφος, Léōn ho Mathēmatikós or ho Philósophos; c. 790 – after 869) was a Byzantine philosopher and logician associated with the Macedonian Renaissance and the end of Iconoclasm. His only preserved writings are some notes contained in manuscripts of Plato's dialogues. He has been called a "true Renaissance man" and "the cleverest man in Byzantium in the 9th century". He was archbishop of Thessalonica and later became the head of the Magnaura School of philosophy in Constantinople, where he taught Aristotelian logic.

Leo was born in Thessaly, a cousin of the Patriarch of Constantinople, John the Grammarian. He was probably at least in part of Armenian descent. In his youth he was educated at Constantinople, but he travelled to the monasteries of Andros, where he could obtain rare manuscripts and was taught mathematics by an old monk. He originally taught privately in obscurity in Constantinople. The story goes that when one of his students was captured during the Byzantine–Arab Wars, the Caliph al-Mamun was so impressed by his knowledge of mathematics that he offered Leo great riches to come to Baghdad. Leo took the letter from the caliph to the Byzantine emperor Theophilos, who, impressed by his international repute, conferred on him a school (ekpaideutērion) in either the Magnaura or the church of the Forty Martyrs.

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