“I HAVE often then inquired earnestly and attentively of very many men eminent for sanctity and learning, how and by what sure and so to speak universal rule I may be able to distinguish the truth of Catholic faith from the falsehood of heretical pravity; and I have always, and in almost every instance, received an answer to this effect: That whether I or any one else should wish to detect the frauds and avoid the snares of heretics as they rise, and to continue sound and complete in the Catholic faith, we must, the Lord helping, fortify our own belief in two ways: first, by the authority of the Divine Law, and then, by the Tradition of the Catholic Church.
“But here someone perhaps will ask, Since the canon of Scripture is complete, and sufficient of itself for everything, and more than sufficient, what need is there to join it with the authority of the Church’s interpretation? For this reason—because, owing to the depth of Holy Scripture, all do not accept it in one and the same sense, but one understands its words in one way, another in another. . . . Therefore, it is very necessary, on account of so great intricacies of such various error, that the rule for right understanding of the prophets and apostles should be framed in accordance with the standard of Ecclesiastical and Catholic interpretation.
“Moreover, in the Catholic Church itself, all possible care must be taken, that we hold that faith which has been believed everywhere, always, by all. For that is truly and in the strictest sense ‘Catholic’ which, as the name itself and the reason of the thing declare, comprehends all things universally. This rule we shall observe if we follow universality, antiquity, and consent. We shall follow universality if we confess that one faith to be true, which the whole Church throughout the world confesses; antiquity, if we in nowise depart from those interpretations which it is manifest were notoriously held by our ancestors and fathers; consent, in like manner, if in antiquity itself we adhere to the consentient definitions and determinations of all, or at least of almost all priests and doctors.”
~St. Vincent of Lérins: Commonitory, Chap. 2
“HE IS the true and genuine Catholic who loves the truth of God, who loves the Church, who loves the Body of Christ, who esteems divine religion and the Catholic Faith, above every thing, above the authority, above the regard, above the genius, above the eloquence, above the philosophy, of every man whatsoever; who sets light by all of these, and continuing steadfast and established in the faith, resolves that he will believe that, and that only, which he is sure the Catholic Church has held universally and from ancient time.”
~St. Vincent of Lérins: Commonitory, Chap. 20