SCHOLARIOS, GENNADIOS (c. 1400–1478), born Georgios Scholarios and also known as Georgios Kourtesios, was a patriarch of Constantinople (1454–1456; 1463; 1464–1465), educator, philosopher, theologian, and defender of Orthodox Christianity. Born in Constantinople, Scholarios began as a student of Mark Eugenikos, metropolitan of Ephesus, an opponent of the papacy. Later, Gennadios schooled himself in the humanities, philosophy, and theology. Unlike most Greeks of the time, Gennadios also learned Latin and was an admirer of Thomas Aquinas, some of whose works he translated into Greek. While still a layman, he preached regularly at court, taught in his own school, and served the Byzantine emperor John VIII (1425–1448) as imperial secretary and Judge General of the Greeks.

Gennadios has usually been pictured as a supporter of the union of the Latin and Greek churches at the abortive Council of Florence (1438–1439), but he subsequently made an about-face following the death of his teacher, Mark of...