Bibliotheca (Photius)

The Bibliotheca (Greek: Βιβλιοθήκη) or Myriobiblos (Μυριόβιβλος, "Ten Thousand Books") was a ninth-century work of Byzantine Patriarch of Constantinople Photius, dedicated to his brother and composed of 279 reviews of books which he had read. It was not meant to be used as a reference work, but was widely used as such in the 9th century, and is generally seen as the first Byzantine work that could be called an encyclopedia. The works he notes are mainly Christian and pagan authors from the 5th century BC to his own time in the 9th century AD. Almost half the books mentioned no longer survive. Reynolds and Wilson call it "a fascinating production, in which Photius shows himself the inventor of the book-review". and say its "280 sections... vary in length from a single sentence to several pages".

Photios I of Constantinople

Photios I (Greek: Φώτιος Phōtios; c.  810 – c. 893), also spelled Photius (/ˈfoʊʃəs/) or Fotios, was the Ecumenical Patriarch of Constantinople from 858 to 867 and from 877 to 886; He is recognized in the Eastern Orthodox Church as St. Photios the Great.

Photios is widely regarded as the most powerful and influential Patriarch of Constantinople since John Chrysostom, and as the most important intellectual of his time, "the leading light of the ninth-century renaissance". He was a central figure in both the conversion of the Slavs to Christianity and the Photian schism.

Photios was a well-educated man from a noble Constantinopolitan family. Photius's great uncle was a previous Patriarch of Constantinople, Tarasius. He intended to be a monk, but chose to be a scholar and statesman instead. In 858, Emperor Michael III (r. 842–867) deposed Patriarch Ignatius of Constantinople, and Photios, still a layman, was appointed in his place. Amid power struggles between the pope and the Byzantine emperor, Ignatius was reinstated. Photios resumed the position when Ignatius died (877), by order of the Byzantine emperor. The new pope, John VIII, approved Photios's reinstatement. Catholics regard a Fourth Council of Constantinople (Roman Catholic) as anathematizing Photios as legitimate. Eastern Orthodox regard a second council named the Fourth Council of Constantinople (Eastern Orthodox), reversing the first, as legitimate. The contested Ecumenical Councils mark the end of unity represented by the first seven Ecumenical Councils.