Every family has to be traced back to its origins. That is why we can say that all these great churches constitute that one original Church of the apostles; for it is from them that they all come. They are all primitive, all apostolic, because they are all one. They bear witness to this unity by the peace in which they all live, the brotherhood which is their name, the fellowship to which they are pledged. The principle on which these associations are based is common tradition by which they share the same sacramental bond.

The only way in which we can prove what the apostles taught—that is to say, what Christ revealed to them—is through those same churches. They were founded by the apostles themselves, who first preached to them by what is called the living voice and later by means of letters.

The Lord had said clearly in former times: I have many more things to tell you, but you cannot endure them now. But he went on to say: When the Spirit of truth comes, he will lead you into the whole truth. Thus Christ shows us that the apostles had full knowledge of the truth, for he had promised that they would receive the whole truth through the Spirit of truth. His promise was certainly fulfilled, since the Acts of the Apostles prove that the Holy Spirit came down on them.