The Church has the office of teaching, and the matter of that teaching is the body of doctrine, which the Apostles left behind them as her perpetual possession. If a question arises as to what the Apostolic doctrine is on a particular point, she has infallibility promised to her to enable her to answer correctly. And, as by the teaching of the Church is understood, not the teaching of this or that Bishop, but their united voice, and a Council is the form the Church must take, in order that all men may recognize that in fact she is teaching on any point in dispute, so in like manner the Pope must come before us in some special form or posture, if he is to be understood to be exercising his teaching office, and that form is called ex cathedrâ. This term is most appropriate, as being on one occasion used by our Lord Himself. When the Jewish doctors taught, they placed themselves in Moses’ seat, and spoke ex cathedrâ; and then, as He tells us, they were to be obeyed by their people, and that, whatever were their private lives or characters. “The Scribes and Pharisees,” He says, “are seated on the chair of Moses: all things therefore whatsoever they shall say to you, observe and do; but according to their works do you not, for they say and do not.”
The forms, by which a General Council is identified as representing the Church herself, are too clear to need drawing out; but what is to be that moral cathedrâ, or teaching chair, in which the Pope sits, when he is to be recognized as in the exercise of his infallible teaching? The new definition answers this question. He speaks ex cathedrâ, or infallibly, when he speaks, first, as the Universal Teacher; secondly, in the name and with the authority of the Apostles; thirdly, on a point of faith or morals; fourthly, with the purpose of binding every member of the Church to accept and believe his decision.
These conditions of course contract the range of his infallibility most materially. Hence Billuart speaking of the Pope says, “Neither in conversation, nor in discussion, nor in interpreting Scripture or the Fathers, nor in consulting, nor in giving his reasons for the point which he has defined, nor in answering letters, nor in private deliberations, supposing he is setting forth his own opinion, is the Pope infallible,” t. ii. p. 110. And for this simple reason, because on these various occasions of speaking his mind, he is not in the chair of the universal doctor.
– from The Vatican Definition
