Saint Photios the Great

Patriarch of Constantinople, St. Photius (AD 895), went from layman to patriarch in six days, a man known for his great learning. He was a protector of the Orthodox Church from the power-seeking Roman Pope and Roman innovators of the Faith which inserted the phrase “and the Son” (Lat., filioque) into the Creed concerning the Holy Spirit’s procession. St. Photius commissioned Ss. Cyril and Methodius to evangelize the Slavic peoples of eastern Europe. [Source]