Chapter 11 — Part I: The Creed — Article IX: The Holy Catholic Church; the Communion of Saints
Section 18. The Church, therefore, as the Scriptures and the writings of the Saints testify, includes within her fold the good and the bad; and it was in this sense that St. Paul spoke of one body and one spirit. Thus understood, the Church is known and is compared to a city built on a mountain, and visible from every side. As all must yield obedience to her authority, it is necessary that she may-be known by all.