The early years of Julian's life were spent in great fear and anxiety. Constantius, regarding him as a possible rival and suspecting him of having designs on the throne, sometimes kept him in provinces far from the capital as a kind of exile and sometimes called him to the capital in order to keep him under observation. Conscious of all the facts about the massacre of many members of his family who had been slain by the order of Constantius, Julian feared death constantly. Constantius forced him to spend a few years in Cappadocia, where he continued the study of ancient writers under the guidance of Mardonius, who accompanied him, and where he also became well acquainted with the Bible and the Gospels. Later Constantius transferred Julian first to Constantinople and then to Nicomedia, where he continued his studies and first exhibited his serious leanings toward paganism.
The greatest rhetorician of that period, Libanius, was lecturing in Nicomedia at that time. He was the true leader of Hellenism, who refused to study Latin, regarding it with disdain. He despised Christianity and attributed the solution of all problems to Hellenism. His enthusiasm for paganism knew no bounds. His lectures were exceedingly popular at Nicomedia. When Constantius decided to send Julian there, he foresaw perhaps what ineffaceable impression the enthusiastic lectures of Libanius might make upon the mind of the young student, and he forbade Julian to attend the lectures of the famous rhetorician. Julian did not formally disobey this imperial command, but he studied the writings of Libanius, discussed the lectures of the inspiring teacher with people who had heard them, and adopted the style and mode of his writings to such an extent that he was afterwards spoken of as a pupil of Libanius. It was also at Nicomedia that Julian studied with enthusiasm the occult neo-Platonic teachings, which at that time aimed to penetrate the future through calling out, by means of certain conjuring formulas, not only ordinary dead people but even the gods (theurgy). The learned philosopher Maximus of Ephesus greatly influenced Julian on this subject.