Peter of Callinicus
Peter of Callinicus was born at Callinicus (al-Raqqa). His father Paul was a believing and truthful orator. Peter was raised in the best fashion, mastering Greek and Syriac and obtaining a fair knowledge of philosophy and theology. Because of his erudition and excellent character, he was chosen a Patriarch of Antioch and was consecrated at the Monastery of Mar Hananya in the year 581. Then he traveled to Alexandria and the Arab province of Hawran to promote the religious ties between the two Sees of Antioch and Alexandria. He became popular for his dialogue with Damianus the Syriac, Patriarch of Alexandria, who was confused in the exposition of the doctrine of the Trinity while attempting to refute the heresy of Tritheism, not because of adherence to heresy, but because of his shortsightedness in knowledge. When he refused to obey the counsel of Peter and attempted, obstinately, to evade discussion or defense of the matter, Peter refuted him in a book which he wrote in Greek, comprising four treatises in one hundred chapters and supported with testimonies from the authorities of the church. According to Mar Michael the Great this book contained three treatises only. Judging from the Syriac MS. preserved in London which comprises twenty-five chapters, i.e., the second book (second treatise), it is most likely that the book was abridged in fifty chapters by some of the writers who lived soon after his time. A copy of this book at the Vatican contains the second volume or the last book in fifty chapters covering four hundred pages.
Peter also wrote a short treatise against the Tritheists, which is perhaps a part of his above-mentioned lengthy book and a treatise against the doctrine of the abbot John of Barbour as well as against Probus, in which he established that the difference of the definition between the two natures of Christ after the unity is maintained. He also wrote letters, of which two were abridged and incorporated by Michael the Great in his Chronicle and a liturgy beginning thus, "O God the Father and the eternal Almighty." He died at the Outer Monastery of Gubba on the 22nd of April, 591, or perhaps 590.
Sources:
Patriarch Ignatius Aphram I Barsoum (2003), The Scattered Pearls, A History of Syriac Literature and Sciences, Translated and Edited by Matti Moosa, New Jersey