Were the ecumenical councils infallible? Many in the early church clearly didn’t consider them so. The most vigorous, and vicious, arguments over Arius took place between Nicea and First Constantinople, and the Monophysite controversy continued for a century and more after Chalcedon had condemned Eutyches (as well as Nestorius).

Nestorianism took root in Syria, and from there spread to Persia, China, India, and in Kurdistan up to the First World War. Copts and Ethiopians never accepted Chalcedon.

Winners in the theological battles appealed to conciliar decisions as decisive and final. In the years leading up to Ephesus (449), Dioscorus of Alexandria challenged his opponent, Flavian of Constantinople, for trying to impose a creed other than Nicea. Yet, it’s clear that there was no widespread conviction that the ecumenical councils were unquestionable.