The Church is everywhere represented as one. It is one body, one family, one fold, one kingdom. It is one because pervaded by one Spirit. We are all baptized into one Spirit so as to become, says the apostle, on body.
The Church, during the apostolic age, did not consist of isolated, independent congregations, but was one body, of which the separate churches were constituent members, each subject to all the rest, or to an authority which extended over all.