The pope teaches infallibly when definitively teaching the whole Church on faith (how we love God) or morals (how we love one another).

Many papal teachings are fallible. We owe intellectual assent to all teachings by the pope as shepherd of his flock, because he is the Vicar of Christ.

Lumen Gentium § 25:

In matters of faith and morals, the bishops speak in the name of Christ and the faithful are to accept their teaching and adhere to it with a religious assent. This religious submission of mind and will must be shown in a special way to the authentic magisterium of the Roman Pontiff, even when he is not speaking ex cathedra; that is, it must be shown in such a way that his supreme magisterium is acknowledged with reverence, the judgments made by him are sincerely adhered to, according to his manifest mind and will.

When the pope teaches infallibly, he also teaches unchangeably. Rabbi Yeshua told us, “I have yet many things to say to you, but you cannot bear them now. When the Spirit of Truth comes, He will guide you into all the truth” Jn 16:12.

The source of the pope’s infallible teaching is supernatural assistance of the Holy Spirit, who protects the supreme teacher of the Church from error. Since God is eternal and therefore does not change Mal 3:6, the Holy Spirit’s teaching is unchangeable.

The distinction between infallible and fallible teachings of the Magisterium is not so much whether we must believe them, we must, but whether or not a future pope may someday change them. That is not something the lay Catholic need be concerned with. All Catholic teaching is authoritative in its time.


The pope speaks infallibly only on matters of faith (how we love God) and morals (how we love one another) Mt 22:3740. Rabbi Yeshua, who said, “I am the good shepherd,” Jn 10:11 told Rabbi Kefa, “Feed my lambs … Tend my sheep … Feed my sheep” Jn 21:1517.

It is always very clear when a pope is speaking definitively. For example, Pope Pius XII’s encyclical Deiparae Virginis Mariae asks, “We wish to know if you, Venerable Brethren, with your learning and prudence consider that the bodily Assumption of the Immaculate Blessed Virgin can be proposed and defined as a dogma of faith, and whether in addition to your own wishes this is desired by your clergy and people.” He is looking for opinions, whether yes or no. But, four years later, his apostolic constitution defining the dogma of the Blessed Virgin Mary’s assumption body and soul into heaven, Munificentissimus Deus, § 44, states: “… we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory.” That’s authority!

Similarly, St. John Paul II’s apostolic letter, Ordinatio Sacerdotalis § 4 (Responsum) states: “I declare that the Church has no authority whatsoever to confer priestly ordination on women and that this judgment is to be definitively held by all the Church’s faithful.”

When such definitive language is present, the pope is clearly speaking infallibly. When it is not present, he may or may not be speaking infallibly. We look for evidence that he is speaking with the full weight of his apostolic authority.

Within the context of the Magisterium, the pope can freely offer his personal views the same as any private theologian. In most cases, when speaking as a private theologian, the pope makes it clear that he is not speaking infallibly, such as by inviting alternate viewpoints. Of course, when a pope speaks as a private theologian and openly invites alternative views, he is speculating rather than teaching. In that case we owe him the great respect due his office but not necessarily the intellectual assent due to authoritative papal teachings.

The Whole Church

The pope speaks infallibly only as shepherd of the whole flock.

When addressing only some of the faithful the pope does not speak infallibly. For example, the Apostolic Letter of Pope John Paul II to the Catholic People of Hungary for the Conclusion of the “Hungarian Millennium” of July 25, 2001 would not contain any infallible teaching.

Faith and Morals

The pope speaks infallibly only on faith and morals. All that we do related to our love for God and one another is faith and morals.

Rabbi Yeshua told us, “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the great and first commandment. And a second is like it, You shall love your neighbor as yourself. On these two commandments depend all the law and the prophets” Mt 22:3740.


All that we do related to our love for God is faith.

Our Father in heaven commanded, “Hear, O Israel, the Lord our God is one Lord; and you shall love the Lord your God with all your heart, and with all your soul, and with all your might” Deut 6:45. He explained: “These words which I command you this day shall be upon your heart; and you shall teach them diligently to your children, and shall talk of them when you sit in your house, and when you walk by the way, and when you lie down, and when you rise. And you shall bind them as a sign upon your hand, and they shall be as frontlets between your eyes. And you shall write them on the doorposts of your house and on your gates” Deut 6:69.

Rabbi Yeshua repeated, “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the great and first commandment” Mt 22:37.


All that we do related to our love for one another is morals.

Our Father in heaven commanded, “You shall love your neighbor as yourself” Lev 19:18.

Rabbi Yeshua repeated, “You shall love your neighbor as yourself” Mt 22:39.

He added, “A new commandment I give to you, that you love one another; even as I have loved you, that you also love one another. By this all men will know that you are my disciples, if you have love for one another” Jn 13:3435. His command is now, “As I have loved you.”

As always, he meant exactly what he said. We are to be willing to accept crucifixion if necessary, for the love of one another. Rabbi Yeshua knows that we remain a fallen race, but he expects us to live as saints on earth in order to be saints in heaven. St. Teresa of Calcutta

“This is my commandment, that you love one another as I have loved you. Greater love has no man than this, that a man lay down his life for his friends. You are my friends if you do what I command you. No longer do I call you servants, for the servant does not know what his master is doing; but I have called you friends, for all that I have heard from my Father I have made known to you. You did not choose me, but I chose you and appointed you that you should go and bear fruit and that your fruit should abide; so that whatever you ask the Father in my name, he may give it to you. This I command you, to love one another. Jn 15:1217.

Church Documents

Pastor Aeternus

Pastor Aeternus, the Dogmatic Constitution of the Church of Christ, approved by Vatican I on July 18, 1870, chapter 4, paragraph 9, defined the extent and limits of papal infallibility.

Therefore, faithfully adhering to the tradition received from the beginning of the christian faith, to the glory of God our savior, for the exaltation of the Catholic religion and for the salvation of the christian people, with the approval of the Sacred Council, we teach and define as a divinely revealed dogma that when the Roman Pontiff speaks EX CATHEDRA, that is, when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals to be held by the whole Church, he possesses, by the divine assistance promised to him in blessed Peter, that infallibility which the divine Redeemer willed his Church to enjoy in defining doctrine concerning faith or morals. Therefore, such definitions of the Roman Pontiff are of themselves, and not by the consent of the Church, irreformable.

Lumen Gentium

Lumen Gentium, the Dogmatic Constitution on the Church, approved by Vatican II including Pope Paul VI on November 21, 1964, clarified the definition. Section 25 states:

And this infallibility with which the Divine Redeemer willed His Church to be endowed in defining doctrine of faith and morals, extends as far as the deposit of Revelation extends, which must be religiously guarded and faithfully expounded. And this is the infallibility which the Roman Pontiff, the head of the college of bishops, enjoys in virtue of his office, when, as the supreme shepherd and teacher of all the faithful, who confirms his brethren in their faith, by a definitive act he proclaims a doctrine of faith or morals. And therefore his definitions, of themselves, and not from the consent of the Church, are justly styled irreformable, since they are pronounced with the assistance of the Holy Spirit, promised to him in blessed Peter, and therefore they need no approval of others, nor do they allow an appeal to any other judgment. For then the Roman Pontiff is not pronouncing judgment as a private person, but as the supreme teacher of the universal Church, in whom the charism of infallibility of the Church itself is individually present, he is expounding or defending a doctrine of Catholic faith. The infallibility promised to the Church resides also in the body of Bishops, when that body exercises the supreme magisterium with the successor of Peter.

Section 27 explains the primacy of each bishop within his diocese and his relation to the Holy Father:

Bishops, as vicars and ambassadors of Christ, govern the particular churches entrusted to them by their counsel, exhortations, example, and even by their authority and sacred power, which indeed they use only for the edification of their flock in truth and holiness, remembering that he who is greater should become as the lesser and he who is the chief become as the servant. This power, which they personally exercise in Christ’s name, is proper, ordinary and immediate, although its exercise is ultimately regulated by the supreme authority of the Church, and can be circumscribed by certain limits, for the advantage of the Church or of the faithful. In virtue of this power, bishops have the sacred right and the duty before the Lord to make laws for their subjects, to pass judgment on them and to moderate everything pertaining to the ordering of worship and the apostolate.

The pastoral office or the habitual and daily care of their sheep is entrusted to them completely; nor are they to be regarded as vicars of the Roman Pontiffs, for they exercise an authority that is proper to them, and are quite correctly called “prelates,” heads of the people whom they govern. Their power, therefore, is not destroyed by the supreme and universal power, but on the contrary it is affirmed, strengthened and vindicated by it, since the Holy Spirit unfailingly preserves the form of government established by Christ the Lord in His Church.

The Primacy of the Successor of Peter in the Mystery of the Church

The Primacy of the Successor of Peter in the Mystery of the Church explains papal primacy in an ecumenical context.

The exercise of the Petrine ministry must be understood – so that it may lose nothing of its authenticity and transparency – on the basis of the Gospel, that is, on its essential place in the saving mystery of Christ and the building-up of the Church. The primacy differs in its essence and in its exercise from the offices of governance found in human societies: it is not an office of co-ordination or management, nor can it be reduced to a primacy of honor, or be conceived as a political monarchy.

The Roman Pontiff – like all the faithful – is subject to the Word of God, to the Catholic faith, and is the guarantor of the Church’s obedience; in this sense he is servus servorum Dei. He does not make arbitrary decisions, but is spokesman for the will of the Lord, who speaks to man in the Scriptures lived and interpreted by Tradition; in other words, the episkope of the primacy has limits set by divine law and by the Church’s divine, inviolable constitution found in Revelation. The Successor of Peter is the rock which guarantees a rigorous fidelity to the Word of God against arbitrariness and conformism: hence the martyrological nature of his primacy.

The Catechism of the Catholic Church

§ 891 The Roman Pontiff, head of the college of bishops, enjoys this infallibility in virtue of his office, when, as supreme pastor and teacher of all the faithful – who confirms his brethren in the faith he proclaims by a definitive act a doctrine pertaining to faith or morals. The infallibility promised to the Church is also present in the body of bishops when, together with Peter’s successor, they exercise the supreme Magisterium, above all in an Ecumenical Council. When the Church through its supreme Magisterium proposes a doctrine for belief as being divinely revealed, and as the teaching of Christ, the definitions must be adhered to with the obedience of faith. This infallibility extends as far as the deposit of divine Revelation itself.

§ 892 Divine assistance is also given to the successors of the apostles, teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a definitive manner, they propose in the exercise of the ordinary Magisterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful are to adhere to it with religious assent which, though distinct from the assent of faith, is nonetheless an extension of it.

Some Additional Observations

The pope teaches infallibly only while he is pope. During the third century, St. Callistus, before becoming Pope, had been associated with Sabellius, the advocate of the monarchian heresy. However, after becoming Pope, St. Callistus condemned Sabellius and excommunicated him.

The pope teaches infallibly only when not under duress. During the fourth century, Emperor Constantius embraced the Arian heresy and forced all the bishops in the empire to proclaim it. St. Athanasius stood virtually alone. When Pope Liberius proclaimed the true faith, Constantius imprisoned and so cruelly mistreated him that Liberius finally agreed to condemn Athanasius. Under extreme pressure Liberius signed an ambiguous confession of faith which was capable of Arian interpretation subordinating the Son to the Father, but he added to it even in prison an anathema on all who said that the Son is not like the Father in substance and in all things.

Papal infallibility addresses only what a Pope teaches, not what he does not teach. During the seventh century Emperor Heraclius at Constantinople promoted the monothelite heresy. Patriarch Sergius of Constantinople accepted this “one will” heresy and wrote to Pope Honorius I asking his opinion. Honorius refused to dispute the issue as Sergius had framed it. Pope St. Agatho affirmed Honorius’ orthodoxy when he declared in a letter to the Emperor that he and all his predecessors “have never ceased to exhort and warn [the monothelites] with many prayers that they should, at least by silence, desist from the heretical error of the depraved dogma.” Honorius is often condemned for negligence in leaving the Lord’s flock exposed to heretical teachers but never for any doctrine attributable to him.

The pope teaches infallibly only on dogma or doctrine, not on discipline. Doctrine is divine law because it comes from divine revelation. Discipline is man-made law. For example Pope Paul VI’s Paenitemini, Apostolic Constitution on Penance, February 17, 1966, states in chapter III that by divine law all the faithful are required to do penance. However, the particular penance of abstinence from meat on all Fridays of the year is a discipline, or man-made law, and may be changed by a pope.

The pope alone teaches infallibly. The Curia or anyone else to whom the pope delegates authority cannot teach infallibly. Curia documents generally receive the approval of the pope before they are published. For example, the declaration Dominus Iesus, by the Congregation for the Doctrine of the Faith, August 6, 2000, states: “The Sovereign Pontiff John Paul II, at the Audience of June 16, 2000, granted to the undersigned Cardinal Prefect of the Congregation for the Doctrine of the Faith, with sure knowledge and by his apostolic authority, ratified and confirmed this Declaration, adopted in Plenary Session and ordered its publication.” This document had the pope’s approval, but not his signature, so the document cannot be considered infallible. When a Curia document repeats a papal teaching, the infallibility of course remains in force but is attached to the original document signed by the pope.

The gift of the Holy Spirit to the Church whereby pastors of the Church, the pope and bishops in union with him, can definitively proclaim a doctrine of faith or morals for the belief of the faithful § § 891. This gift is related to the inability of the whole body of the faithful to err in matters of faith and morals § 92Faith is how we love God. Morals are how we love one another.

Levels of Theological Certainty

Catholic Answers on Papal Infallibility