Maximus was selected and ordained, in violation of canon law, by Patriarch Anatolius of Constantinople, without the official sanction of the clergy or people of Antioch.
Having thus discreetly assured his position, he was summoned to the Council of Chalcedon in October 451 and took his seat without question, and when the acts of the Second Council of Ephesus were quashed, including the deposition of the other prelates, a special exception was made of the substitution of Maximus II for Domnus II on the express ground that Leo I had opened communion with him and recognized his episcopate (Philippe Labbe, Concilia, iv.
Leo I promised to help him against either Jerusalem or Constantinople, exhorting him to assert his privileges as bishop of the third see in Christendom (i.e. only inferior to Alexandria and Rome).
Maximus II's zeal for the orthodox faith receives warm commendation from Leo I, who exhorts him as consors apostolicae sedis to maintain the doctrine founded by St. Peter speciali magisterio in the cities of Antioch and Rome, against the erroneous teaching both of Nestorius and Eutyches and to watch over the churches of the East generally and keep Leo informed about events.
Leo I closes his letter with a desire that Maximus will restrain unordained persons, whether monks or laity, from public preaching and teaching.