The First Vatican Council produced only two major documents, Dei Filius and Pastor Aeternus. The former mainly concerns the relation between faith and reason; the latter concerns the charisms of the Roman Pontiff. Both documents provide a firm doctrinal basis for the defense of Pope Francis, as well as every Pope or Ecumenical Council accused of grave error or grave failures of faith. This article compare the teachings of Dei Filius to the claims of those who oppose the magisterial teachings of Pope Francis.
Dei Filus teaches us to rely on faith above reason, and that since our fallen reason can err, we must never put our own reasonings above the teachings of the Faith, which require the assent of faith. But one of the most fundamental errors of those who accuse Pope Francis of grave error — or of heresy and worse — is the assumption that their evaluation of his decisions, using the faculty of reason, suffices to negate teachings that call for the full assent of faith. Therefore, this conflict between Francis and the papal critics can be seen as a kind of specious contradiction between reason and faith. Dei Filius resolves this conflict among fallen sinners by requiring us to believe what the Roman Pontiff and the Ecumenical Councils teach, even contrary to our own evaluation of those teachings using the faculty of reason.
Dei Filius: the Son of God
Some of the most important and specific teachings of Dei Filius, those most useful to correct the subsequent errors of the Francis critics, are reviewed below.
Vatican I, Dei Filius: “The Son of God, Redeemer of the human race, our Lord Jesus Christ, promised, when about to return to his heavenly Father, that He would be with this Church militant upon earth all days, even to the end of the world [Mt 28:20]. Hence never at any time has He ceased to stand by His beloved Bride, assisting Her when She teaches, blessing Her in Her labors and bringing Her help when She is in danger.” 
The Church is indefectible. She can never go astray or lead astray. And the reason for this indefectibility is that our Lord Jesus Christ promised to be with the Church on earth “all days, even to the end”. Therefore, “never at any time” has Jesus failed to keep this promise. And His protection of the Church in Her indefectibility extends to constant divine help when She teaches, guides, labors, and struggles against dangers.
The claim that the Church has gone astray or has led the faithful astray since Vatican II is contrary to the dogma of the indefectibility of the Church. Jesus, at all times assisting the Church in Her teaching, never permits heresy or other grave error to be taught, as this would contradict His promise that the gates of Hell shall never prevail over Her (Mt 16:18).
Dei Filius: “Everybody knows that those heresies, condemned by the fathers of Trent, which rejected the divine Magisterium of the Church and allowed religious questions to be a matter for the judgment of each individual, have gradually collapsed into a multiplicity of sects, either at variance or in agreement with one another; and by this means a good many people have had all faith in Christ destroyed.” 
Those who claim that Pope Francis has erred gravely, has taught heresy, has even failed in faith to the extent of apostasy or idolatry are effectively rebuked by the above teaching by Dei Filius. The faithful of Christ rely upon faith in the teachings of the Magisterium, because that teaching authority is not merely human, but is divine. So it matters not who Pope Francis is as a person, or what his personal failings may be. Saint or sinner, the teachings of Pope Francis under the Magisterium are the teachings of the indefectible Church and Her divine Magisterium.
The common error of all who accuse Pope Francis, other Popes, and Vatican II, is that they have “allowed religious questions to be a matter for the judgment of each individual”. We see this again and again in those Catholics who struggle against magisterial teaching. They offer their own reasoning and explanation as to why the teachings of the Magisterium cannot be true. It seems as if they accept nothing taught by any Pope or Council unless it first passes through their own personal judgment — or that of a subculture to which they adhere.
Yes, those who have relied on their own judgment rather than relying on faith in what the Magisterium teaches have “gradually collapsed into a multiplicity of sects.” The Francis critics are united; they are today comprised of different small groups following one cult of personality or another among the many self-proclaimed guardians of truth who oppose Pope Francis. There are those who claim Pope Benedict XVI is still the Roman Pontiff. Others “recognize” Francis as the valid Pope, but call for the faithful to “resist” him. Still others hold that Francis is a false prophet or is associated with the Antichrist. Those who have refused to trust in the Magisterium are divided among themselves. Once they were faithful believers in Christ and His Church. Now they are like a beautiful crystal bowl that has shattered into thousands of dangerous shards. Their errors endanger the souls of those who are weak in faith.
Dei Filius: “Even though faith is above reason, there can never be any real disagreement between faith and reason, since it is the same God who reveals the mysteries and infuses faith, and who has endowed the human mind with the light of reason.
“God cannot deny himself, nor can truth ever be in opposition to truth. The appearance of this kind of specious contradiction is chiefly due to the fact that either the dogmas of faith are not understood and explained in accordance with the mind of the Church, or unsound views are mistaken for the conclusions of reason.
“Therefore we define that every assertion contrary to the truth of enlightened faith is totally false.” 
Right reason can never contradict the truths of divine revelation. For God is the source of both gifts: reason and faith. However, when we poor fallen sinners, afflicted by concupiscence and by the negative effects caused by our own sins, make use of the gift of reason, we often err. We are human, but the one, holy, catholic, and apostolic Church is both human and divine — like Her Head and Savior, Jesus Christ. So we must always put our faith in the teachings of the Magisterium above our own understanding.
Some Catholics claim that Pope Francis has erred so gravely in his teachings that he has taught or propagated multiple heresies, has committed idolatry, and has failed in faith so thoroughly as to be considered an apostate. These same critics of Francis also tend to justify their accusations by proposing that other Popes have also failed in faith or erred gravely in doctrine. But all these accusations are nothing more than a use of created reason, in opposition to the uncreated truths of divine revelation taught by the Church, to evaluate and condemn whatever teachings of the Magisterium conflict with fallen human reason.
And while these papal critics claim that they are correcting errors that contradict the dogmas of Faith, this conclusion is of reason, not faith. For the Church was founded by Christ on Peter and his successors, along with the Apostolic College; they are the only ones who may teach with the authority of Christ. Their teachings alone require the assent of faith. For as Dei Filius teaches, only those truths of Sacred Tradition and Sacred Scripture which are also proposed by the Magisterium infallibly require the full assent of faith:
Dei Filius: “Wherefore, by divine and Catholic faith all those things are to be believed which are contained in the word of God as found in Scripture and tradition, and which are proposed by the Church as matters to be believed as divinely revealed, whether by her solemn judgment or in her ordinary and universal magisterium.” 
Therefore, when individuals or groups apart from the Magisterium claim that Popes or Councils have erred gravely, and that their understanding of dogma is to be believed instead, we must put our faith in what the Magisterium teaches. For the reasonings of those who reject the teachings of Popes and Councils are just as Dei Filius teaches, a “kind of specious contradiction” which is “contrary to the truth of enlightened faith”. Those who accuse Popes or Councils of heresy rely upon their own reason, rather than faith in what the Magisterium teaches through those Popes and Councils. They have not understood divine revelation better than the Church whom Christ never ceases to stand by, assist, bless, and help. Instead, they accuse the Magisterium of grave errors because “the dogmas of faith are not understood and explained in accordance with the mind of the Church, or unsound views are mistaken for the conclusions of reason.”
That is the fundamental error of all who accuse any Pope or Council of grave errors on faith or morals, or of leading the faithful astray by grave errors on discipline. They rely upon “the conclusions of reason” and their own misunderstandings of dogma, in direct opposition to the decisions of the Church Herself by the successors of the Apostles. But the First Vatican Council teaches us instead to rely on faith in the teachings of the indefectible Church.
This one true Church is Apostolic. She is always only that Church led by the successors of the Apostle Peter and the successors of the other Apostles. These successors can never fall away from the true faith, nor teach grave error. Such is the indefectibility promised by Christ and secured by the Holy Spirit, until the end of time.
Ronald L. Conte Jr.
1. Vatican I, Dei Filius, Introduction, n. 1.
2. Vatican I, Dei Filius, Introduction, n. 5.
3. Vatican I, Dei Filius, chapter 4, n. 5-7.
4. Vatican I, Dei Filius, chapter 3, n. 8.