Arsenius remained intransigent, however, and at length, Michael VIII deposed him and on 28 December 1266 named Joseph to the patriarchate.

Joseph I, soon issued a pardon to the emperor, which enraged the supporters of his predecessor and exacerbated the so-called "Arsenite schism".

[1] For Michael VIII, who was threatened by the ambitions of Charles I of Anjou, the Union was the sole instrument for preventing a full-scale assault by the Western powers on his empire, but the Byzantine clergy and people almost universally opposed the concessions made to the Papacy on matters of doctrine and Papal supremacy.

[3] In 1273, Joseph I swore an oath not to accept the Union under the terms set out by the Pope, and in early 1274, as the Byzantine delegation prepared to travel to Italy to effect the Union, retired from his official duties to the Church of St. George of Samatya Peribleptos Monastery, Mystras.

[2] Following the death of Michael VIII in 1282, Andronikos II reversed his father's ecclesiastical policies, deposing the pro-Unionist John XI of Constantinople and recalling Joseph I to the patriarchate (31 December 1282).