NICHOLAS THE MYSTIC. — Patriarch of Constantinople (901–907; 912–25), born about the middle of the 9th century in Byzantine Italy. He was a senator and imperial councillor in timo (whence the title “Mystic”) to his predecessor ANTONY CAULLAS. At the beginning of his patriarchate he maintained good relations with the papacy. When, however, Emperor LEO VI turned to the other patriarchs rather than Pope SERGIUS III to obtain a dispensation for a fourth marriage (after the deaths of his first three wives), NICHOLAS was indignant and therefore avoided meeting the envoys of Pope Sergius who came to Constantinople in 906. His intransigent stance was the cause of his deposition decreed by the Emperor.
The Emperor, having first secured a letter of abdication from NICHOLAS, elevated his spiritual father EUTHYMIUS to the patriarchal see; Euthymius accepted this dignity once he learned of NICHOLAS’s abdication and became acquainted with the tenor of the letters from the other patriarchs and the Pope permitting Leo VI’s fourth marriage. After Leo’s death (912), his successor and brother ALEXANDER exiled Euthymius and recalled NICHOLAS to the see. During his second patriarchate (912–25) NICHOLAS wrote several times to Popes ANASTASIUS III and JOHN X to secure peace between his own partisans and those loyal to Euthymius, and to restore harmony between Byzantium and Rome; he also resumed his rigorous stance regarding the tetragamy of the deceased Emperor. Thus, after various unsuccessful attempts, he obtained from Pope JOHN X an embassy in 923. The outcome was favourable for internal Byzantine peace and for the cause of union. NICHOLAS died on 15 May 925; the Greek Church celebrates his memory on the same day. His 63 letters were edited by Cardinal MAI in 1844 and reprinted in PG 111, 1–406.