This thesis investigates the use of traditional philosophical concepts to legitimise new structures of power in the writings of the fourth-century Greco-Roman elite, with special attention to the emperor Julian “the Apostate” and the philosopher-bishop Synesius of Cyrene, but including also Eusebius of Caesarea, Constantine, Constantius II, Themistius, John Chrysostom, and Gregory of Nazianzus.

When considering the strategies developed by fourth-century leaders to legitimise their authority through literature, what is striking are the level of engagement with philosophical authorities from the past (particularly Plato and Aristotle) and the pervasive use (and abuse) of words related to philosophy, reason, “scientific” method, intellectual training, and spiritual elevation. Religious allegiance, crucially, determined whom fourth-century politicians saw as colleagues in the context of what they depicted as a new “age of philosophy”. My thesis argues that the rivalry between pagans and Christians over philosophy, its definition, and the identity of its true patrons and practitioners, was instrumental to another rivalry, that over the rational/correct interpretation of the destiny of the Roman empire; it served the ambition to deprive religious rivals of the opportunity to lay claims over history and to control the idea that a divine plan regulated its course.

In the context of this conceptual framework, I also reassess the role of the main protagonists of my thesis, Julian and Synesius, within it. Whereas current scholarship tends to isolate Julian from the contemporary political debate, a comparative analysis of his political orations vis-à-vis the imperial propaganda of his predecessors Constantine and Constantius II (ch. 1-3) shows that Julian’s self-projection as a philosopher-emperor was not an innovation, but the (pagan) recovery of a strategy of philosophical self-presentation of the sovereign that had already been exploited by the house of Constantine in a Christian key.

In the second part of my thesis (ch. 4-7), I re-assess Synesius’ political rhetoric by showing that, similarly to Julian’s reaction to the notion of Christian philosophical kingship, Synesius tried to respond as a traditional philosopher to contemporary attempts to depict the Christian power as philosophical. Constantine’s institutionalisation of the Church as an organ of state affairs elicited, on the side of bishops and Christian holy men, a collective effort of self-legitimisation that led them to appropriate traits of the Hellenistic figure of the philosopher-advisor to kings. What strikes one about Synesius’ writings is the antagonistic quality of his efforts to present himself as ideal philosopher and to claim the role of political counsellor to the powerful: my contention is that, as a traditional Neoplatonist, he reacted against what he perceived as the usurpation of long-established philosophical categories on the side of the Christian ascetic and contra-cultural strand of his times (especially that of John Chrysostom).