As Origen of Alexandria, he returned in the second century to the city he had known as St. Mark and was one of the most distinguished theologians of the early Church, setting forth the true teachings of Jesus Christ on reincarnation and the heavenly hierarchy. At the age of eighteen, he was appointed head of the Catechetical School—the first institution where Christians could be instructed in both the Greek sciences and the doctrines of holy scripture. He lived as an ascetic, working day and night with the crowds, lecturing and giving personal consultation. He made a thorough study of Plato, Pythagoras and the Stoics and learned Hebrew in order to properly interpret scripture. But his deep understanding seemed to shallow, worldly minds bizarre and heretical.