The project is coordinated by Katharina Heyden, Professor for Ancient History of Christianity and Interreligious Encounters at the University of Bern (Switzerland), and David Nirenberg, Director and Leon Levy Professor at the Institute for Advanced Study, Princeton (U.S.), and includes a network of collaborators across North America, Europe, and the Middle East.

According to his enemies, the Byzantine philosopher Georgios Gemistos Pletho (ca. 1360–1454) was an apostate who broke away from Christianity and, with a shadowy group of followers, began worshipping the pagan gods of ancient Greece. Gemistos’s Neopagan sect was claimed to be a co-production of the most pernicious kind, whose doctrinal origins went back to Elissaeus, a Jewish apostate alleged to have been Gemistos’s teacher, or to Mohammed, the prophet of Islam, to a nameless Christian heretic from Alexandria, to Epicurus, and, ultimately, to the diabolical philosopher Plato. In this essay I focus on one of Gemistos’s enemies – George of Trebizond (aka Trapezuntius) – to show how he drew on Christian heresiology and fears of Islamic conquest to create a new and monstrous vision of Gemistos. Together, Trapezuntius and others forged a remarkable co-production from the ideas of diverse and competing religious groups: Gemistos Pletho became a Jewish-trained “second Mohammed” and “fourth Plato” whose doctrines were poised to destroy Christianity.