The Council of Nicaea was convoked by Emperor Constantine mainly to settle issues raised by the controversy of Arius. At that time Sylvester I was the bishop of Rome and it was he who sent two presbyters as his vicars. We know their names, Vitus and Vincentius, from other sources (conciliar lists, Socrates Scholasticus, Ecclesiastical History I.13 [739]; Anonymous (Gelasius) of Cyzicus II.28.1, [849]).