18.

 How do the decisions of a local council obtain ecumenical authority?

            The Ecumenical Councils are unerring and express the consciousness and the life of the Church. While the doctrinal definitions of the Ecumenical Councils are infallible, those of local councils of individual bishops are always liable to error. However, if the decisions reached in local councils are accepted by the rest of the Church, they then come to acquire ecumenical authority — that is, a universal authority similar to that possessed by the doctrinal statements of an Ecumenical Council.