One of the major humanists of quattrocento Italy, George [of Trebizond] was also a paranoid fanatic who believed in a conspiracy of platonists preparing the coming of the Antichrist. His Comparatio philosophorum Platonis et Aristotelis, finished in 1458, has been described as “one of the most remarkable mixtures of learning and lunacy ever penned.” Not only is Plato attacked there as a pitifully poor philosopher, but he is also accused of every possible error, sin, or weakness (including sexual depravity, drunkenness, idolatry, sorcery, and demon-worship) and described as the very fountainhead of all heresies. To make matters even worse, not only had Plato exerted a pernicious influence on Christianity by means of his writings, but in George’s apocalyptic imagination he had given birth to a whole series of successors who continued his work. Muhammad was the second Plato, Plethon the third, and George’s Comparatio culminated in dire warnings against Cardinal Bessarion, the fourth Plato, who wanted to become pope and might very well succeed. For proper perspective, one should realize that George of Trebizond and Bessarion were both Greek converts to Roman Catholicism; but Bessarion was a former pupil of Plethon who remained faithful to his teacher, and came to the Council as a strong proponent of union. Because George saw Greek Christianity as platonic, and Roman Catholicism as aristotelian, the idea of the “fourth Plato” on the throne of St. Peter evoked the specter of a Greek/platonist takeover of the Church of Christ. Even though Trebizond’s Comparatio circulated only in manuscript, Bessarion responded with his important In calumniatorem Platonis, first written in Greek, then translated into Latin, and printed in 1469. Deeply influenced by Plethon’s perspective, it defended Plato’s thought and argued for its profound compatibility both with Christianity and with Aristotle. It is considered the most important synthesis of Renaissance platonism prior to Ficino’s. With this remarkable couple of Catholic converts (one born in Trebizond and the other from a family that came from there) the battle lines were drawn in the sharpest possible manner.
– Esotericism and the Academy: Rejected Knowledge in Western Culture (2012), pp. 78-9