Ibas attended the First Council of Ephesus in 431 as a presbyter, was cognizant of the autocratic conduct of Cyril of Alexandria, and wrote in 433 the letter to a man that became known as "Maris, bishop of Hardaschir (or Adashir) in Persia", a letter which later became one of the Three Chapters. The name might well be a misunderstood appellation formula for the bishop of Seleucia-Ctesiphon, a city known as Adashir during the Sassanid period, which at that point was a certain Catholicus Dadyeshu (421-56), head of the Nestorians in Persia. "Maris" had been at Edessa previous to the Nestorian controversy, and Ibas wrote to tell him what had occurred since his visit. Though evidently written under great exasperation, it shows Ibas as a man of independent judgment, and free from partisanship. In the letter, Nestorius is severely censured for refusing the title Theotokos to the Virgin Mary, and Ibas accuses Cyril of Apollinarianism, and denounces the heresy of his 12 chapters, charging him with maintaining the perfect identity of the manhood and Godhead in Christ, and denying the Catholic doctrine of the union of two Natures in One Person.