first patriarch of Constantinople (1454–64) under Turkish rule and the foremost Greek Orthodox Aristotelian theologian and polemicist of his time. Scholarios became expert in European philosophy and theology and was called “the Latinist” derisively by his colleagues. He also taught and commented on Aristotelian and Neoplatonic texts, the chief expressions of classical Greek realism and idealism, respectively.

Scholarios was an imperial judge and lay preacher at the court of the Byzantine emperor John VIII Palaeologus. He was then named a theological consultant to the general Council of Florence (1439) when the Greek Byzantine Church reluctantly consented to a union with the West in order to win military support against the advance of the Ottoman Turks. Later, in Constantinople, Scholarios repudiated the council's statement of doctrinal compatibility between Eastern and Western churches. He assumed leadership of the anti-unionist faction that proclaimed Orthodoxy's absolute autonomy and fundamental differences with Western Christianity. Out of favour with Emperor Constantine XI Palaeologus (1449–53), Scholarios became a monk at Constantinople's monastery of Pantocrator. When that city fell to the Ottoman Turks, May 1453, he was captured by a hospitable Muslim and then invited to assume the vacant patriarchate by Sultan Mehmed II (1451–81) in order to stabilize the political situation. He was invested with ecclesiastical insignia and political authority as head of the Greek population. The Greek Orthodox Church thus became a civil as well as a religious authority and remained as such for nearly 500 years. He helped persuade the Sultan to adopt a more conciliatory policy toward Christian peoples under Islāmic political control.

Scholarios' 10-year patriarchal office was twice interrupted by Greek–Arab tensions, and he finally abdicated and retired to the Prodromos monastery at Sérrai (near modern Thessalonica 【Thessaloníki】, Greece). There he produced a wealth of theological and philosophical literature, including commentaries, on the works of Thomas Aquinas (unusual for an Eastern theologian); polemical tracts supporting Aristotelian thought; and many other compositions in liturgy, ethics, and poetry.