Mardonius, also spelled Mardonios, was a Roman rhetorician, philosopher and educator of Gothic descent. Mardonius was the childhood tutor and adviser of the 4th century Roman emperor Julian, on whom he had an immense influence.
Mardonius was a eunuch of Gothic origin.[2] He was probably a lifelong pagan.[3] He grew up as a slave in the household of Julius Julianus, who was the praetorian prefect of Licinius. Julianus trained him from an early age to become a scholar.[2] During this time Mardonius acquired extensive knowledge of Greek poetry and philosophy. Mardonius was particularly influenced by the world of Homer, which he contrasted with the decadence of contemporary society.[2][4] He was the teacher of his master's daughter Basilina. In 330, Basilina would marry Julius Constantius, the half-brother of Constantine the Great, who had defeated Licinius and seized control of the entire Roman Empire. The couple had one son, the later emperor Julian.
While Basilina died of natural causes, Julius Constantius was murdered after the death of Constantine the Great. Since 338, Julian lived in the household of his grandfather, with Mardonius as his tutor. Emperor Constantius II issued an imperial decree that Julian was not to be instructed in ancient Greek philosophy, but Mardonius ignored this order.[5] The seven-year-old orphan Julian and Mardonius developed a close emotional bond.[6][2][1] Mardonius introduced Julian to Socrates, Plato and Aristotle, and to the works of Homer, which Julian particularly enjoyed. Mardonius functioned not only as his academic teacher, but also as a moral tutor, the "guardian of his virtue", as the rhetorican Libanius put it.[6] He took great care in bringing up Julian in accordance with his own conservative beliefs and principles, seeking to infuse the young prince with the Homeric virtue of simplicity.[2][4] Mardonius had a particular disdain for entertainment, and because of this, Julian did not attend theaters or horse races until he reached adulthood.[7] He also instructed Julian to walk modestly, with his eyes fixed on the ground, in contrast to the swaggery fashionable with Roman elites at the time.[7] It is likely that the influence of Mardonius contributed to Julian's later decision to abandon Christianity.[3][2]
Julian’s freedom as a student had a powerful influence on him and ensured that for the first time in a century the future emperor would be a man of culture.[8]
Julian was separated from Mardonius at the age of 11, an event which he considered one of the most painful of his life.[6] Mardonius was one of Julian's few personal friends,[7] and after Julian assumed the position of emperor, became one of his advisers, frequently visiting him for dinner in Constantinople.[9]
Mardonius is mentioned in several works by Julian, in particular his satire "Misopogon" ("Beard-Hater"). In the funeral oration on Julian, Libanius mentioned the positive influence Mardonius had on his pupil.