Themistius' close relationship with Christian emperors from Constantius to Theodosius makes him one of the most important political thinkers and politicians of the later fourth century, and his dealings with Julian the Apostate have recently attracted much speculation. This volume presents a new critical edition, translation and analysis of Themistius' letter to Julian about kingship and government, which survives mainly in Arabic, together with texts, translations and analyses of Julian's Letter to Themistius and Sopater's Letter to Himerius. The volume is completed with a text, translation and analysis of the other genuine work of Greek political theory to survive in Arabic, the Letter of Aristotle to Alexander, which dates from an earlier period and throws into relief the particular concerns of Themistius, Julian, and the rulers of the fourth-century Roman world.