Catholic Culture Resources
Catholic Culture Resources

The Nature of Infallibility

By Dr. Jeff Mirus ( bio - articles - email ) | Mar 05, 2010

I’ve alluded frequently enough to the four basic arguments that establish the teaching authority of the popes (for a brief summary see my 2005 blog entry on The Primacy of Peter). But the topic of papal infallibility concerns me again just now in a somewhat more precise way, especially in light of last week’s In Depth Analysis (Escape from Theological Minimalism). The precise issue is this: Granted that the pope can teach infallibly, how do we know when he is doing so?

Infallibility and “Definitions”

This a fair question, and it has received quite a few confusing answers. The confusion tends to come from those who (as I mentioned in my piece on theological minimalism) want to limit what we have to believe to truths that are labeled “definitions”. Thus some have argued that the pope is not infallible unless he explicitly claims to be making a “definition” of faith, in effect defining a dogma. Or to put it in the terms used at Vatican I, it is argued that only such explicit “definitions” qualify as ex cathedra statements whose infallibility is guaranteed.

On this (inadequate) understanding, only two relatively recent Magisterial acts are considered to be infallible, the proclamation of the Immaculate Conception by Pius IX in 1854 and of the Assumption by Pius XII in 1950, both of which were solemnly defined as dogmas. The infallibility of other magisterial teachings has been questioned, for example the teaching against contraception by Paul VI in Humanae Vitae, or even the strong statement by John Paul II on the Church’s inability to ordain women. Let’s take a quick look at the objections to these two statements, as representatives of a type.

When Paul VI taught the immorality of contraception, he first set forth the natural and Christian vision of marriage and procreation. He then concluded as follows:


Therefore We base Our words on the first principles of a human and Christian doctrine of marriage when We are obliged once more to declare that the direct interruption of the generative process already begun and, above all, all direct abortion, even for therapeutic reasons, are to be absolutely excluded as lawful means of regulating the number of children. Equally to be condemned, as the magisterium of the Church has affirmed on many occasions, is direct sterilization, whether of the man or of the woman, whether permanent or temporary.
Similarly excluded is any action which either before, at the moment of, or after sexual intercourse, is specifically intended to prevent procreation—whether as an end or as a means. (Humanae Vitae, #14)

Those who wished to deny the certain truth of this teaching immediately argued that the pope had failed to state that he was “defining” anything, and therefore this statement must be taken as only a very weighty opinion from which, for good reason, theologians may legitimately dissent.

When John Paul II taught that the Church is not authorized to ordain women, he used the following far stronger language:


Wherefore, in order that all doubt may be removed regarding a matter of great importance, a matter which pertains to the Church's divine constitution itself, in virtue of my ministry of confirming the brethren (cf. Lk 22:32) 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. (Apostolic Letter on Reserving Priestly Ordination to Men Alone, #4)

Despite the forcefulness of this statement, some who did not like it actually argued that the pope failed the infallibility test because he hadn’t said he was teaching definitively (he had said instead that his judgment was to be “definitively held”)! Others argued that the Church’s lack of authority is not a positive teaching of faith, and so the statement did not qualify as infallible.

The Nature of Infallibility

In such baseless arguments we begin to see how absurd it is to attempt to tie infallibility to particular verbal formulas. Infallibility depends not on a magic formula but on the very nature of the Church herself as a perfect society salvifically bound to Christ until the end of time. Because the Church is an indefectible society ordered to salvation, she must not only have the light of Christ’s teaching but she must have this light in such a way that she cannot, as a body, fall into error in the matters of salvation for which she was constituted (namely, matters of faith and morals). Indeed, as John Henry Cardinal Newman so wisely observed, if the first generation of Christians had a living and infallible guide, it would create a marked difference in dispensation if subsequent generations lacked such a guide. In fact, it would be a signal that the Church had already been effectively destroyed.

Thus we logically expect that the Church must possess an infallible teaching authority (or Magisterium), and this is exactly what we find in Scripture, Tradition and the Church’s mode of operation from the earliest times. Peter was given the keys to heaven and the power to bind and loose. Christ prayed that Peter would not defect in faith so that he in turn could confirm the faith of his brethren. The earliest Christian community understood that this authority must be passed on to Peter’s successors for the Church to remain what it was, and it acknowledged Peter’s successors in the bishops of Rome. From the first Christians looked to the popes for decisions about the Faith. Heretics and orthodox alike sought vindication in Rome, and this authority was scarcely challenged for several hundred years until a portion of the Church came under pressure from the Byzantine Emperor.

As a matter of fundamental ecclesiology, then, we find two significant truths. First, all the members of the Church are bound to obey Peter and his successors when they purport to settle questions of faith and morals. Second, all the members of the Church cannot be bound to error without the Church being destroyed, the gates of Hell prevailing against her, and Christ’s promise to be with her until the end of time made void. Therefore, from both the promises of Christ Himself and the very necessity imposed by the nature of the Church, the Holy Spirit must preserve the popes from error when they exercise their supreme authority to teach about faith and morals to the whole Church.

Papal Intention

Note again that this protection does not depend on any sort of verbal formula; it is not invoked by the casting of some spell. Rather, it depends simply and solely on the intention of the Pope to teach on a matter of faith and morals. While not all such teachings are “de fide” (that is, not all state something specifically revealed in the deposit of faith), all are nonetheless true, for all are drawn either directly or as corollaries from Revelation or the natural law, the two sources from which we learn how to attain union with God. When the pope speaks about matters of faith and morals, then, the question is not whether he uses a specific formula but whether it is sufficiently clear that he intends (1) by virtue of his supreme authority (2) to explain a doctrine (3) on a matter of faith or morals (4) to be held by the whole Church. Obviously the language he uses must give us the necessary clues, and it is true that the more formal and precise the pope is in stating his intention, the easier it is to tell whether he is teaching infallibly. But if the intention is clear, then the whole Church must obey, and the teaching must by the nature of things be infallible. There is no other option.

This, then, is the explanation behind Vatican II’s expression of the authority of what is called the ordinary magisterium of the Church. Having stated that the faithful must adhere “with a religious assent” to what the bishops teach in communion with the Roman Pontiff (such as what they teach in the documents promulgated by an ecumenical council), the Council goes on to say:


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. His mind and will in the matter may be known either from the character of the documents, from his frequent repetition of the same doctrine, or from his manner of speaking. (#25)

What this means is that we must look to the intention expressed in the document in question to determine what the Pope’s mind and will are. Clearly, we can only know this “either from the character of the documents, from his frequent repetition of the same doctrine, or from his manner of speaking.” And if we discern that his mind and will are to teach to the whole Church by virtue of his Petrine authority on a matter of faith and morals, then we must accept his teaching act as infallible—and the resulting statements as certainly true.

When Wouldn’t He Be Infallible?

Now the pope’s intention might be certain or uncertain and, if certain, it might actually be certain that he did not intend to teach infallibly. Thus, for example, when Pope John Paul II and Pope Benedict XVI both wrote and published books during their pontificates, in which they touched on many points of theology and spirituality, it was obvious from the first that they did not intend this as an exercise of their papal magisterium. Indeed, in the introduction to his own book, Benedict expressly states that anyone is free to disagree with him. In these cases, the popes did not intend to teach, just as they would not intend to teach in an off-hand remark, a telephone conversation, or a private letter. In still other cases, a pope might clearly intend to offer spiritual advice or pastoral counsel, rather than to formally teach on a matter of faith and morals, or he might impose some discipline on the whole Church, requiring obedience but not involving faith, such as a particular fast. Again, if a pope were to say even to the whole Church that we should work as if everything depends on us and pray as if everything depends on God, only a fool would argue that he had thereby given an infallible explanation of the precise nature of our dependence on Divine Providence.

Quite apart from the pope’s intention, there are large areas in which Christ has not promised to protect the pope’s utterances, and equally large areas in which the Holy Spirit is not bound by the nature of the Church to protect the pope from error. If the pope chooses to comment to the whole Church about some situation in the world which is not a matter of faith and morals (such as opining, as John Paul II did, that modern penal systems make the death penalty mostly unnecessary), he has no special protection. He may be right or wrong, and the faithful may agree or disagree. If he teaches theology to a particular class, or makes a spiritual point to a group of pilgrims, or argues a point of doctrine in a private letter to his best friend, the Holy Spirit can see there is no risk of binding the whole Church. In other words, whenever the pope is speaking in his private capacity as a man, or is not addressing the entire Church, or is discussing something other than faith and morals, he is not infallible.

There could also be situations in which the Pope’s intention is uncertain. Either the audience he has in mind might or his desire to teach may be unclear. For example, if in an encyclical a pope were to write that “Mary receives her splendor as the stars receive light from the sun”, it would be at best uncertain that the pope intends to teach what the mistaken scientific reference implies. He has simply used a simile in the service of some larger point, and the simile has (in the light of a more perfect astronomical understanding) fallen flat. Or if the pope writes favorably of the theological achievements of a particular saint in an encyclical commemorating that saint’s birth, we may doubt that he intends to formally teach the saint’s particular views to the whole Church.

However, if one or more popes were to repeat the same idea about faith or morals in various ways and various documents over a period of time, one would at length come to understand that there really is a truth at stake which is being formally taught and which requires assent. Hence, again, the pope’s intent may be known “either from the character of the documents, from his frequent repetition of the same doctrine, or from his manner of speaking.”

Vatican I’s Decree on Infallibility

With all this in mind, and remembering that my first motivation was to refute those who artificially restrict infallibility to “definitions” and “dogma”, let us examine the language used at Vatican I in its justly famous decree on papal infallibility in Chapter 4 of the First Dogmatic Constitution on the Church of Christ:


And so We, adhering faithfully to the tradition received from the beginning of the Christian faith, to the glory of God, our Savior, the elevation of the Catholic religion and the salvation of Christian peoples, with the approbation of the sacred Council, teach and explain that the dogma has been divinely revealed: that the Roman Pontiff, when he speaks ex cathedra, that is, when carrying out the duty of the pastor and teacher of all Christians in accord with his supreme apostolic authority he explains a doctrine of faith or morals to be held by the universal Church, through the divine assistance promised him in blessed Peter, operates with that infallibility with which the divine Redeemer wished that His church be instructed in defining doctrine on faith and morals; and so such definitions of the Roman Pontiff from himself, but not from the consensus of the Church, are unalterable.

Here at last we can see where the words “defining” and “definitions” come in. They come not as terms needed to identify infallible teaching, but as the obvious consequence of having uttered an infallible teaching. The pope is infallible when (1) by virtue of his supreme authority (2) he explains a doctrine (3) of faith or morals (4) to be held by the universal Church. It is precisely this teaching, however expressed, that constitutes the “definitions” the passage later mentions. The pope does not have to state that he is “defining” something or that his teaching is a “definition”. Rather, when he teaches by his supreme authority on a matter of faith or morals to the whole church, the matter is thus defined, and may be referred to henceforth as a definition.

When the pope uses his authority as pope to promulgate a document explaining a matter of faith and morals to the whole Church—as is the case with many encyclicals and apostolic letters, for example—his intention is generally quite clear. Any given document may be long and may touch on many matters by way of introduction, background or implication. But if he is deliberately addressing a particular issue of faith or morals, especially a controverted issue, in order to make Catholic teaching clear, at certain key points the document in question will make more categorical statements to “explain a doctrine”. Wherever this intention is clear, regardless of the specific form of language used, the faithful are bound to adhere to the teaching in question. The pope’s act of teaching is then infallible, and so what he has taught is certainly true.


Jeffrey Mirus holds a Ph.D. in intellectual history from Princeton University. A co-founder of Christendom College, he also pioneered Catholic Internet services. He is the founder of Trinity Communications and See full bio.

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  • Posted by: - Mar. 08, 2010 9:27 AM ET USA

    thanks a much needed refresher

  • Posted by: dschenkjr9859 - Mar. 06, 2010 7:43 AM ET USA

    Jeff, Good info to have. Every year, out of the blue, this topic comes up in some conversation. Everyone has their own opinion. I will file this away for reference and future emailing to my firends who evolve their Catholic beliefs "on the fly".

  • Posted by: - Mar. 05, 2010 4:31 PM ET USA

    Holy Mother Church is many a splendid thing. How wonderful it is to know that in matters of faith and morals, we have no worry that we are getting error. On another blog, the matter of ordaining woman priestesses came up as though it was still debatable and it wasn't until I mentioned papal infallibility, Ordinatio Sacerdotalis, that my Catholic friend finally understood.