“This heresy [that the Holy Ghost proceeds from the Father alone], up to the time of Photius, was only held by a few persons, but on his intrusion into the See of Constantinople, in 858, and especially in 863, when he was condemned by Pope Nicholas I., he constituted himself, not alone the chief of the schism, which for so many years has separated the Greek and Latin Churches, but induced the whole Greek Church to embrace this heresy . . . Fourteen times, Osius writes, up to the time of the Council of Florence, held in 1439, the Greeks renounced this error, and united themselves to the Latin Church, but always relapsed again. In the Council of Florence, they themselves agreed in defining that the Holy Ghost proceeds from the Father and the Son, and it was thought that the union would be everlasting, but such was not the case, for after they left the Council, they again returned to their vomit, at the instigation of Mark of Ephesus. I now speak of these Greeks who were under the obedience of the Eastern Patriarchs, for the others who were not subject to them remained united in Faith to the Roman Church.”  —St. Alphonsus de Liguori