Vincent of Lérins: "To test the true faith"

“IT ALWAYS was, and is today, the usual practice of Catholics to test the true faith by two methods; first, by the authority of the divine Canon, and then, by the tradition of the Catholic Church. Not that the Canon is insufficient in itself in each case. But, because more interpreters of the Divine Word make use of their own arbitrary judgment and thus fall into various opinions and errors, the understanding of Holy Scripture must conform to the single rule of Catholic teaching—and this especially in regard to those questions upon which the foundations of all Catholic dogma are laid.”

~St. Vincent of Lérins: Commonitory for the Antiquity and Universality of the Catholic Faith, Ch. 29. (A.D. 434)