development of widely separated parts of Christendom conformed more or
less closely to a common type. It was due to agencies such as these that
the scattered churches did not go each its own way and become ultimately
separate and diverse institutions. But this general unity became
official, and expressed itself in organization, only with the rise of
the conciliar and metropolitan systems. Already before the end of the
2nd century local synods were held in Asia Minor to deal with Montanism,
and in the 3rd century provincial synods became common, and by the
council of Nicaea (canon 5) it was decreed that they should be held
twice every year in every province. Larger synods representing the
churches of a number of contiguous provinces also met frequently; for
instance, in the early 4th century at Elvira, Ancyra, Neo-Caesarea and
Arles, the last representing the entire Western world. Such gatherings
were especially common during the great doctrinal controversies of the
4th century. In 325 the first general or ecumenical council,
representing theoretically the entire Christian Church, was held at
Nicaea. Other councils of the first period now recognized as ecumenical
by the Church both East and West are Constantinople I. (381), Ephesus
(431), Chalcedon (451), Constantinople II. (553). All these were called
by the emperor, and to their decisions he gave the force of law. Thus
the character of the Church as a state institution voiced itself in
them. (See COUNCIL.)

The theory referred to above, that the bishops are successors of the
apostles, and as such the authoritative conservators and interpreters of
apostolic truth, involves of course the solidarity of the episcopate,
and the assumption that all bishops are in complete harmony and bear
witness to the same body of doctrine. This assumption, however, was not
always sustained by the facts. Serious disagreements even on important
matters developed frequently. As a result the ecumenical council came
into existence especially for the purpose of settling disputed questions
of doctrine, and giving to the collective episcopate the opportunity to
express its voice in a final and official way. At the council of Nicaea,
and at the ecumenical councils which followed, the idea of an infallible
episcopate giving authoritative and permanent utterance to apostolic and
therefore divine truth, found clear expression, and has been handed down
as a part of the faith of the Catholic Church bot