Byzantine Platonism

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Byzantine Platonism is the name modern historians give to the study of Plato that persisted in the Greek-speaking Christian East, from the survival of the late antique schools through to the fall of Constantinople in 1453. It was never a movement with a creed, and for most of that span it was not even a school. It was a habit of reading kept alive in a culture that had inherited the Greek philosophical texts intact while regarding their pagan content with deep suspicion.

That suspicion is the central tension. The Byzantines possessed Plato, Plotinus, and Proclus in the original — manuscripts the Latin West had lost and would later recover only through them — yet Platonism carried the charge of the paganism Christianity had defeated, and an interest in it could end a career or worse. Plato could be read, mined, and admired, but not believed. The whole long life of the tradition can be read as a sustained negotiation of that line: how much of the philosophy a Christian intellectual might take into his own thinking before the taking became apostasy.

The inheritance: a closed school and an open library

The story opens with an ending. In 529 the emperor Justinian closed the Platonic Academy at Athens — the last institutional descendant of the school Plato had founded nine centuries earlier — and the pagan philosophers who had taught there, Damascius and Simplicius among them, scattered, some briefly to the Persian court. With that act the living, ritual-positive Platonism of late antiquity, the Neoplatonism systematized by Iamblichus and Proclus, lost its last public institution inside the empire. What it did not lose was its books. The dialogues of Plato, the Enneads of Plotinus, the vast Procline commentaries on the Timaeus and Parmenides, the Elements of Theology, the Chaldean Oracles and their theurgical exegesis — all of this remained in Greek, copied and recopied in Byzantine scriptoria for reasons that had as much to do with the prestige of the classical inheritance as with any taste for its metaphysics.

This is the peculiar shape of the tradition. In the Latin West, Plato all but vanished: the medieval reader had the Timaeus in Calcidius’s partial Latin version and almost nothing else, and Platonism survived there as a diffuse influence carried through Augustine, Boethius, and the pseudonymous Dionysian corpus rather than as a body of texts one could actually open — the situation traced under Latin Platonism. In Byzantium the texts themselves were on the shelf, legible, in the author’s own language. The difference was not learning but possession. The East held the corpus; the West held the memory of it. That asymmetry would decide where the Renaissance began.

The habit of reading and its dangers

Because Platonism in the Christian East was a body of reading rather than a confession, it lived in individuals and in the libraries they assembled, flaring up wherever a scholar of sufficient range and nerve chose to take the old texts seriously. The pattern is one of recurrent revivals, each shadowed by the same hazard. To Photios in the ninth century the philosophers were material to be summarized and assessed; the great bibliophile-patriarch read and excerpted them with the cool eye of a cataloger. The danger lay not in reading but in believing — in treating Plato’s account of soul, cosmos, and the divine as true rather than as a magnificent error to be corrected by revelation.

The eleventh century produced the most consequential of these revivals. Michael Psellos (1018 – c. 1078), a court scholar of formidable range who held under Constantine IX the revived title hypatos tōn philosophōn — consul of the philosophers — set out a deliberate programme of recovering Plato, Plotinus, Iamblichus, and Proclus, and wrote a cluster of short treatises expounding the Chaldean Oracles. His Chaldean opuscula are not antiquarian curiosities: they are the structural hinge of the entire later transmission. Roughly a third of the surviving hexameter fragments of the Oracles, and most of what can be reconstructed of Proclus’s lost commentary on them, come down to us only because Psellos summarized, paraphrased, and embedded that material inside a Christian rhetorical frame that could survive ecclesiastical scrutiny. He insisted, in his Apologia and his profession of faith, that he read theurgy as a historian of ideas and not as a practitioner — a genre signal carefully set, and a necessary one. When his old friend John Xiphilinos accused him in the 1050s of forsaking Christ to follow Plato, Psellos answered not with a repudiation of the philosophical project but with a rhetorical recalibration that left the texts and the programme intact.

The line his pupil crossed was drawn more sharply. John Italos, an immigrant from Byzantine Italy who succeeded Psellos as head of the imperially sponsored school of philosophy, applied dialectical reasoning to matters of dogma with a combative confidence that drew first admiration and then alarm. Investigated in 1076/77 and acquitted, he was tried again in 1082, condemned for heterodoxy, and forced into retirement; eleven chapters of anathema against him and his teaching were added to the Synodikon of Orthodoxy, the liturgical text proclaimed each year on the first Sunday of Lent, the Sunday of Orthodoxy. The charges as the anathemas frame them — the eternity of the world, the transmigration of souls, the real existence of Platonic Ideas, a disrespect toward the human nature of Christ and the cult of the saints — are the classic doctrines that mark where Hellenic philosophy and Christian dogma cannot be reconciled. Whether Italos actually held them in the form charged is debated; his own surviving quaestiones do not straightforwardly bear the accusations out, and the synod may have been condemning a method — the application of syllogism to revealed truth — as much as a set of propositions. What matters for the tradition is the precedent. The condemnation was not a passing verdict but a permanent fixture of the liturgy: every year, in every Orthodox church, the anathema against those who pursue Hellenic learning beyond its proper bounds was read aloud. The lesson held for centuries. Plato could be read, mined, and admired, but not believed.

Plethon at Mistra: the line crossed

The figure who finally broke that restraint stands at the very end of the tradition, in its last surviving outpost. George Gemistos Plethon (c. 1355/1360 – 1452), working at Mistra in the Peloponnese — the hill-city that had become the cultural capital of the Despotate of the Morea as Constantinople itself shrank toward its end — came to hold, guardedly in public and openly within his circle, that the Platonic philosophy was not merely a tool for Christian theology but a truer account of the divine than Christianity offered. He had adopted the name Plethon, the full, as a deliberate echo of Platon; the gesture announced an ambition that was no longer exegetical but rival.

In 1438–39 Plethon accompanied the emperor John VIII Palaiologos to the council of union at Ferrara and Florence, the last great attempt to reconcile the Greek and Latin churches before the Ottoman conquest. While the theologians argued over the filioque and the procession of the Holy Spirit, Plethon, on the margins of the official proceedings, lectured Florentine humanists on Plato and composed a treatise, On the Differences of Plato and Aristotle (the De Differentiis), arguing the superiority of Plato over the Aristotle who had dominated Latin scholastic thought for the better part of eight centuries. To an Italian audience hungry for the Greek texts and accustomed to knowing Plato only by report, the lectures were a revelation. The encounter is traditionally credited with prompting Cosimo de’ Medici — the Florentine banker and de facto ruler treated under Cosimo de’ Medici — to conceive the project that became Marsilio Ficino’s Platonic Academy, the workshop from which Ficino’s complete Latin Plato and Plotinus would eventually issue. Ficino himself, looking back, called Plethon a second Plato. Florence is, on this reckoning, the place where the Byzantine library and the Latin appetite for it finally met.

Plethon’s own great work went much further than the lectures dared. The Book of Laws (Nomōn syngraphē), modelled in title and ambition on Plato’s own last dialogue, sketched a reformed religion — a polytheism in which the old gods returned not as the literal deities of cult but as philosophical principles, an ordered hierarchy of being descended from the One, with Zeus as the supreme first cause and the lesser gods as the intelligible and psychic orders beneath him. It supplied a calendar of festivals, prayers, and a metaphysics, an entire system meant to replace both Christianity and Islam with a restored Hellenic wisdom. How far Plethon actually intended a revived paganism, and how far the label was fixed on him by hostile readers, remains a genuinely contested question among scholars. Some read him as a sincere apostate who concealed under philosophical language a real intention to refound Hellenic religion; others as a bold but still recognizably philosophical reformer whose gods were never more than a metaphysical vocabulary. The evidence cannot fully settle it, partly because so little of the Laws survives — and it survives so thinly for a reason. After Plethon’s death the manuscript came into the hands of Gennadios Scholarios, his old philosophical adversary and the first patriarch of Constantinople under Ottoman rule. Judging it the work of a man who had abandoned Christ, Scholarios had it burned. What remains is a set of fragments — chapter headings, a calendar, the sections that copyists had excerpted before the fire — preserved chiefly in the nineteenth-century edition of Charles Alexandre. The most ambitious attempt to turn Byzantine Platonism back into a living religion was destroyed by the last guardian of Byzantine Orthodoxy, in the first years after the empire that had contained them both had ceased to exist.

The transmission west

What was not destroyed was the philosophy, and the books. The decisive figure here is Plethon’s own pupil, Bessarion (c. 1403–1472), who as a young monk had studied at Mistra and who at the Council of Florence argued, against most of his fellow Greeks, for union with the Latin church. He stayed in the West, converted his allegiance to Rome, and was made a cardinal — the highest office a Greek had held in the Latin hierarchy. The case for Bessarion is set out under Bessarion. Where Plethon’s paganism alarmed even his admirers, Bessarion defended Plato in terms a Christian humanist could accept, answering George of Trebizond’s polemical Comparison of Plato and Aristotle with his own measured In Calumniatorem Platonis, the work that more than any other made Plato respectable in Latin Christendom.

And Bessarion collected. Over a lifetime he assembled the greatest private library of Greek manuscripts in Europe, hunting down rare codices across Greece and Italy and having copied what he could not buy, expressly to save the written inheritance of the Greek world from the wreck of Byzantium. In 1468 he gave the whole collection — some 482 Greek and 264 Latin volumes — to the Republic of Venice, on the condition that it be kept as a public library; it became the nucleus of the Biblioteca Marciana, where much of it remains. With that bequest the texts the Byzantine East had guarded for a thousand years, half forbidden, passed bodily into Latin hands at the very moment the world that had guarded them ended. The current was no longer a habit of careful, suspicious reading inside a Christian empire; it had become the raw material of the Florentine revival, the Renaissance Neoplatonism of Ficino and Pico, feeding back into the Christian Neoplatonism of the Latin theologians and on into the whole esoteric inheritance of early modern Europe.

Scholarship and the surviving texts

Because the tradition lived in manuscripts rather than institutions, its modern study is inseparable from the editing of those manuscripts. The genuine philosophical opuscula of Psellos — including the Chaldean treatises that anchor the transmission — were established in the standard critical edition of John Duffy and Dominic O’Meara, Michaelis Pselli Philosophica Minora (2 vols., Teubner, 1989, 1992); the older but still-consulted column reference is J.-P. Migne’s Patrologia Graeca vol. 122 (Paris, 1864), which prints the Expositio in oracula Chaldaica and the Hypotypōsis of Chaldean doctrine. The dialogue De operatione daemonum, read throughout the medieval and early-modern West as Psellos’s own and a foundation of the Western image of Byzantine demonology, was shown by Paul Gautier to be a later work falsely attributed to him; his critical re-edition, “Le De daemonibus du Pseudo-Psellos” (Revue des études byzantines 38, 1980, pp. 105–194), is open access on Persée. The eleventh-century context — Psellos’s programme, the affair of 1054, the milieu in which Italos was condemned — is narrated in Psellos’s own Chronographia; the case of John Italos and the doctrines for which he was anathematized are surveyed in the Stanford Encyclopedia of Philosophy’s entry John Italos, with its account of the eleven chapters added to the Synodikon of Orthodoxy.

For Plethon the indispensable modern study is Niketas Siniossoglou’s Radical Platonism in Byzantium: Illumination and Utopia in Gemistos Plethon (Cambridge, 2011), which argues for a genuine and coherent pagan Platonism behind the fragments — a thesis assessed, with its difficulties, in the open Bryn Mawr Classical Review. The surviving fragments of the Book of Laws were edited with a French translation by Charles Alexandre, Pléthon. Traité des lois (Paris: Firmin Didot, 1858); the critical edition of Plethon’s recension of the Chaldean Oracles is Brigitte Tambrun-Krasker’s Oracles chaldaïques. Recension de Georges Gémiste Pléthon (Athens / Paris / Brussels, 1995). The transmission as a whole — possession, prohibition, and the eventual passage west — is the subject of James Hankins’s Plato in the Italian Renaissance (Brill, 1990) and of Polymnia Athanassiadi’s study of the Byzantine commentators on the Chaldean Oracles. The primary foundation under all of it can be opened directly: the dialogues of Plato in Benjamin Jowett’s translation and the Enneads of Plotinus in Stephen MacKenna’s are hosted in the library, the same two corpora that the Byzantine scribes kept legible across the long centuries when no one in the Latin world could read them at all.

The texts went west; the empire did not. When Constantinople fell, the scholars who had kept Plato in his own language carried him out in their saddlebags and their crates — Bessarion’s to Venice, Plethon’s reordered Oracles to Florence — and the philosophy that a Christian state had held for a millennium without ever quite daring to believe it found, in a Latin world that had only ever half remembered it, readers at last willing to take it as true.

→ In the library: The Dialogues of Plato (Jowett, 1892) · Plotinus — The Enneads (MacKenna, 1926)

→ Related: Neoplatonism · Marsilio Ficino · The One · Middle Ages · Plato · Proclus · Platonism · Christianity · Chaldean Oracles Tradition · Aristotle · Bessarion · Cosimo De Medici · Byzantine Empire · Renaissance Neoplatonism · Christian Neoplatonism · Iamblichus · Latin Platonism