TIMOTHEOS I, Nestorian patriarch. — Born in 727 or 728 at Hazza near Arbela, died in 823. A monk in the monastery of St George, he later became bishop of Bejt Bagas and in 779 patriarch.
After two years of struggle to secure universal recognition of his office, he governed his Church with wisdom and firmness for more than forty years, during which it reached its greatest extent. He founded six new ecclesiastical provinces, sent missionaries—generally monks—to the Caspian Sea, Transoxania, as far as distant Tibet and southern Arabia, improved the training of the clergy by founding schools, and took great care in the selection of bishops. With the court of the 'Abbasid caliphs in Baghdad, where he had strong supporters, he always maintained good relations and defended the Christian religion in a public disputation before the caliph al-Mahdi.
Among his writings, first to be noted are his numerous and highly interesting letters (over 200), a series of canonical decisions, and his apology of Christianity before the caliph al-Mahdi. His Christological doctrine is essentially that common to the Nestorians. He acknowledged the necessity of grace; his conception of the Eucharist seems correct; he admitted the validity of baptism administered by Catholic or Monophysite priests; he regarded the five patriarchs as equal among themselves, with a certain pre-eminence for that of Seleucia-Ctesiphon.