Photios I of Constantinople
At the 879–880 Council of Constantinople the Eastern Orthodox Church anathematized the "Filioque" phrase, "as a novelty and augmentation of the Creed", and in their 1848 encyclical the Eastern Patriarchs spoke of it as a heresy. It was qualified as such by some of the Eastern Orthodox Church's saints, including Photios I of Constantinople, Mark of Ephesus, and Gregory Palamas, who have been called the Three Pillars of Orthodoxy. The Eastern church believes by the Western church inserting the "Filioque" unilaterally (without consulting or holding council with the East) into the Creed, that the Western Church broke communion with the East.