Reduced to its simplest and most general terms, the rule of faith is to accept with docile spirit the existing teaching of the Church, and to verify it by searching the Scriptures; for it is the function of the Church to teach and of the Scriptures to prove the Faith. Among us this means practically that an unlearned Anglican should assume that the Church's teaching is correctly embodied in the Book of Common Prayer. If he does otherwise, he rejects providential guidance in favor of incompetent private judgment.
But competent theologians may and ought to test the provincial and current doctrines which they have received, in order to ascertain if such doctrines really have Catholic authority. And such testing, repeated in every generation and in various lands, is one of the chief means under God by which the Faith is preserved in the Church in its original purity and integrity. The method to be employed is implied in the rule of St. Vincent of Lerins: "In the Catholic Church we must take care to hold what has been believed everywhere, always, and by all," "quod ubique, quod semper, quod ab omnibus creditum est." In short, the marks of universality, antiquity, and consent are to be looked for; and this, not to discover the Catholic Faith, but to verify the Catholicity of existing doctrines.
The test of universality is applied first, or the concurrent voice of the living Church, heard in all its various particular portions. If the doctrines considered stand this test, adequately and correctly applied, they will stand the other two tests; for the Church universal ever teaches the same Faith, and the consent meant by St. Vincent is never wanting to universal doctrine.
The test of antiquity is next applied by tracing the doctrine through the ages to primitive days, in order to ascertain if it agrees with what has been taught by the Church from the beginning. This test is of especial importance when dispute exists as to the mark of universality. Legitimate developments in doctrinal language must, of course, be carefully allowed for.
Finally the test of consent is made use of. This does not require us to discover that the doctrine has been explicitly accepted by every Catholic believer, or even by every theologian. A mere counting of heads is futile. What is to be ascertained is, whether the generality of representative Catholic theologians can be seen to agree, when their respective places in theological development, and diverse points of view and modes of expression, are taken duly into account. ...
In the case of certain doctrines, theologians find themselves unable to apply all of the Vincentian tests because of insufficient data. Such failure is not necessarily a proof that the doctrine is not Catholic. If such research as is practicable tends to confirm the ability of the doctrine to stand the necessary tests, this fact, along with the doctrine's ecclesiastical origin, affords sufficient warrant for accepting its Catholic value. In the case of a doctrine imposed by ecclesiastical authority, the burden of proof lies with the subject of such authority who would reject its Catholic value. To disprove this value in such a case one must prove positively, and with adequate knowledge, that the doctrine cannot stand the Vincentian tests. An appeal to silence or to ignorance is not necessarily sufficient.