Chapter 11 — Part I — Article IX (Of the Church)
Section 271. Q. What great privilege has the Catholic Church? A. She alone has the sublime promises that the gates of hell shall not prevail against her; that the Lord shall be with her even to the end of the world; that in her shall abide the glory of God in Christ Jesus throughout all generations forever; and consequently that she shall never apostatize from the faith, nor sin against the truth of the faith, or fall into error. We undoubtingly confess, as sure truth, that the Catholic Church can not sin, nor err, nor utter falsehood in place of truth; for the Holy Ghost, ever working through his faithful ministers the fathers and doctors of the Church, preserves her from all error. (Missive of the Eastern Patriarchs on the Orthodox Faith, Art. 12.)