The word “unanimous” comes from two Latin words: únus, one + animus, mind. “Consent” in Latin means agreement, accord and harmony; being of the same mind or opinion. Where the Fathers speak in harmony, with one mind overall - not necessarily each and every one agreeing on every detail but by consensus and general agreement - we have “unanimous consent.” There, the teachings of the Fathers provide us with an authentic witness to the apostolic tradition.

St. Irenaeus (A.D.130-200) writes of the “tradition derived from the Apostles, of the very great, the very ancient and universally known Church founded and organized at Rome” (Against Heresies, III, 3, 2), and the “tradition which originates from the Apostles [and] which is preserved by means of the successions of presbyters in the Churches” (Ibid., III, 2, 2) which “does thus exist in the Church, and is permanent among us” (Ibid., III, 5, 1). Unanimous consent develops from the understanding of the apostolic teaching preserved in the Church with the Fathers as its authentic witness.

St. Vincent of Lerins explains the Church’s teaching: “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 universally. This rule we shall observe if we follow universality, antiquity, 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 no wise depart from those interpretations which it is manifest were notoriously held by our holy ancestors and fathers; consent, in like manner, if in antiquity itself we adhere to the consentient definitions and determinations of all, or at the least of almost all priests and doctors” (Commonitory 2). Notice that St. Vincent mentions “almost all priests and doctors.”

The phrase “unanimous consent of the Fathers” had a specific application as used at the Council of Trent (Fourth Session), and reiterated at the First Vatican Council (Dogmatic Decrees of the Vatican Council, chap. 2). The Council Fathers specifically applied the phrase to the interpretation of Scripture. Biblical and theological confusion was rampant in the wake of the Protestant Reformation. Martin Luther stated, “There are almost as many sects and beliefs as there are heads; this one will not admit baptism; that one rejects the Sacrament of the altar; another places another world between the present one and the day of judgment; some teach that Jesus Christ is not God. There is not an individual, however clownish he may be, who does not claim to be inspired by the Holy Ghost, and who does not put forth as prophecies his ravings and dreams.”

The Council Fathers at Trent (1554-63) affirmed the ancient custom that the proper understanding of Scripture was that which was held by the Fathers of the Church. In this way, they hoped to bring order out of the rising chaos. Opposition to the Church’s teaching is exemplified by William Webster (The Church of Rome at the Bar of History [Carlisle, PA: Banner of Truth Trust, 1995]), who misrepresents the Council Fathers by redefining and misapplying “unanimous consent.” First in redefining, he implies that unanimous consent means 100% affirmation by each Father. This is a false understanding of the phrase and even in American law, unanimous consent “does not always mean that every one present voted for the proposition, but it may, and generally does, mean, when a [verbal] vote is taken, that no one voted in the negative” (Black’s Law Dictionary).

Second, Webster misapplies the term, not to the interpretation of Scripture, as the Council Fathers intended, but to tradition. His assertions are patently untrue, but using a skewed definition and application of “unanimous consent,” he uses selective patristic passages as proof-texts for his analysis of the Fathers.

As an example, individual Fathers may explain the "Rock” in Matthew 16 as Jesus, Peter, Peter’s confession or Peter’s faith. Even the Catechism of the Catholic Church refers to the “Rock” of Matthew 16 as Peter in one place (CCC 552) and his faith in another (CCC 424). Matthew 16 can be applied in many ways to refute false teachings and to instruct the faithful without emphasizing the literal, historical interpretation of Peter as the Rock upon which the Church has been built. Webster and others emphasize various patristic applications as “proof” of non-unanimous consent.

Discussing certain variations in the interpretations of the Fathers, Pope Leo XIII (The Study of Holy Scripture, from the encyclical Providentissimus Deus, Nov., 1893) writes, “Because the defense of Holy Scripture must be carried on vigorously, all the opinions which the individual Fathers or the recent interpreters have set forth in explaining it need not be maintained equally. For they, in interpreting passages where physical matters are concerned have made judgments according to the opinions of the age, and thus not always according to truth, so that they have made statements which today are not approved. Therefore, we must carefully discern what they hand down which really pertains to faith or is intimately connected with it, and what they hand down with unanimous consent; for ‘in those matters which are not under the obligation of faith, the saints were free to have different opinions, just as we are,’ according to the opinion of St. Thomas.”