The Church sees the Fathers as the successors of the apostles, the closest source to the apostolic teaching and tradition, and therefore authoritative. One must ask, why should I trust Protestant Joe X’s interpretation, or his pastor’s, when we can go back to the source and listen to those who knew the apostles?
One must understand what the Church means when she is bound by the “unanimous consent” of the Fathers. The Church cannot, has not, and does not contradict Herself. She can develop doctrine, but she cannot deny what is organically Her heritage and the foundation of her existence in the Scriptures, the Tradition and the Magisterium. The Church does not claim that all her “authority rests” on the consent of the Fathers. It rests on several things including Scripture; the Fathers are one element of this foundation.
Second, the Church has never understood or taught that “unanimous” consent means that the Fathers are individually infallible or that various Fathers have never held an alternative opinion. Any given passage of scripture may have several valid applications and they were all appropriated by the Fathers depending on the matter at hand. Thus, a Father may refer to Jesus as the “Rock”, Peter as the “Rock”, or Peter’s confession as the “Rock”. This in not unusual or unexpected. It certainly does not negate the literal intent of Matthew, nor does it invalidate the “unanimous consent” of the Fathers.
The Catholic Church has organically grown up from the apostles and the Fathers. To say that it does not agree with them is absurd. Now, what is the unanimous consent of the Fathers? The Maryknoll Catholic Dictionary gives a good simple definition:
When the Fathers of the Church are morally unanimous in their teaching that a certain doctrine is a part of revelation, or is received by the universal Church, or that the opposite of a doctrine is heretical, then their united testimony is a certain criterion of divine revelation. As the Fathers are not personally infallible, the counter testimony of one or two would not be destructive of the value of the collective testimony; so a moral unanimity only is required.
The word unanimous comes from two Latin words: unus, one + animus, mind. “Consent”, as was used when coined means “to be of the same mind or opinion.” Where the Fathers speak overall with one mind, not necessarily each and every one, nor numerically complete, but by consensus and general agreement, we have “unanimous consent.”
To illustrate, I cite the following excerpt from Pope Leo XIII (“The Study of Holy Scripture”, from the encyclical Providentissimus Deus, Nov. 1893) where the pope admits that there are varying ideas among the Fathers and that not everything they write is a matter of dogma. He could not say this if he understood “unanimous consent” as having to agree on every detail:
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. In another passage he most prudently holds: “It seems to me to be safer that such opinions as the philosophers have expressed in common and are not repugnant to our faith should not be asserted as dogmas of the faith, even if they are introduced some times under the names of philosophers, nor should they thus be denied as contrary to faith, lest an opportunity be afforded to the philosophers of this world to belittle the teachings of the faith.” (Henry Denzinger, The Sources of Catholic Dogma [London: B. Herder Book Co., 1954], 491-492)