These conditions are best summarized as follows: 1) The pope, when 2) he defines 3) a doctrine concerning faith or morals 4) to be held by the entire Church 5) using his teaching authority as supreme teacher of all Christians, speaks infallibly.
This Divine protection, seen as always belonging to the Deposit of Faith and thus always believed at least implicitly, was explicitly defined (note: not invented) at the First Vatican Council in 1870. In the entire history of the Church, it has been formally invoked only twice--in 1854 by Pope Pius IX to define the dogma of the Immaculate Conception, and in 1950 by Pope Pius XII to define the dogma of the Assumption.
Following the theme of this blog, I would like to examine the writing style--in particular the grammar--used by the aforementioned popes in their infallible definitions. Through their sentence structure and choice of words, these pontifical "Modern Catholic Writers" have, in essence, created a standardized grammatical formula to convey to the world with the utmost clarity both their intention to invoke this infallibility and the defined dogma whose veracity is now forever beyond reproach.
Let's first examine Pius IX's infallible pronouncement on the Immaculate Conception. It is contained in his encyclical Ineffabilis Deus. Below are the two paragraphs containing the definition itself, color-coded for future reference: (Am I the only one who gets the chills when I read this?)
Accordingly, by the inspiration of the Holy Spirit, for the honor of the Holy and undivided Trinity, for the glory and adornment of the Virgin Mother of God, for the exaltation of the Catholic Faith, and for the furtherance of the Catholic religion, by the authority of Jesus Christ our Lord, of the Blessed Apostles Peter and Paul, and by our own: "We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful."
Hence, if anyone shall dare -- which God forbid! -- to think otherwise than as has been defined by us, let him know and understand that he is condemned by his own judgment; that he has suffered shipwreck in the faith; that he has separated from the unity of the Church...
So, we already see a very clearly-defined sentence structure. First, we see an invocation of the authority of the Trinity, the Virgin Mary, the Church, the apostles Peter and Paul, and--equally important in this context--the pope himself, who is making it clear that he is invoking his teaching authority as successor to those apostles (condition #5). Then, we have the three key words--proclaim, declare, define (condition #2)--followed by the dogma itself, which we can see clearly pertains to a matter of faith (condition #3). The last sentence of the first paragraph leaves no doubt that this dogma is to be believed by the entire Church (condition #4).
According to Catholic teaching, this pronouncement is not--cannot be--wrong. Hence the stern warning in the last paragraph to not put one's own judgement over that of Christ speaking through His Vicar on Earth. Don't mess with Pio Nono!
Now let's fast forward 96 years and five more popes to Pope Pius XII's infallible pronouncement on the Assumption. Once again, we provide the relevant two paragraphs from Pope Pius XII's apostolic constitution, Munificentissimus Deus. Watch for the correspondence!
44. For which reason, after we have poured forth prayers of supplication again and again to God, and have invoked the light of the Spirit of Truth, for the glory of Almighty God who has lavished his special affection upon the Virgin Mary, for the honor of her Son, the immortal King of the Ages and the Victor over sin and death, for the increase of the glory of that same august Mother, and for the joy and exultation of the entire Church; by the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, 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.Amazing, isn't it! Or am I the only one who things so? In any event, if you're ever elected pope you now know how to write an infallible statement. Just make sure it's true--otherwise, you'll likely be struck dead before you get it down on paper...
45. Hence if anyone, which God forbid, should dare willfully to deny or to call into doubt that which we have defined, let him know that he has fallen away completely from the divine and Catholic Faith.
Before we conclude, let's briefly examine a papal statement that, in and of itself, is not an infallible pronouncement. Once again, the grammar is the giveaway.
Below is the conclusion of Pope John Paul II's 1994 Apostolic Letter Ordinatio Sacerdotalis (On Ordination to the Priesthood), written in response to demands by some within the church that women be allowed to be ordained priests:
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.See what's missing? For one, nowhere to be found is the word "define" (condition #3). It's also quite a stretch to equate the pope's "ministry of confirming the brethren" with his supreme teaching authority as teacher of all Christians (condition #5). If Pope John Paul II had intended to issue an infallible pronouncement, it would certainly behoove him to use the formula described above.
So, the teaching on the impossibility of women's ordination is up for grabs? Actually, not at all. This is a classic example of a pronouncement being infallible while not being an infallible pronouncement. For example, I can make an infallible statement: "Two plus two equals four." Even if the pope himself "pronounced, declared, and defined" that two pus two equals four, it wouldn't be considered an infallible pronouncement because math has nothing to do with faith and morals. But the statement is still true because math says so, and that's the point.
In the case of women's ordination, its impossibility--due to the fact that Christ chose only men as His apostles so as to establish a mystical spousal relationship between His priests and His bride the Church--is already maintained by what is called the ordinary magistarium of the Church (as opposed to the extraordinary magistarium of infallible papal statements and dogmatic councils). This constant teaching of the Church throughout the centuries is also infallible. Thus, in Ordinatio Sacerdotalis Pope John Paul II was simply repeating something already infallible, something true because the ordinary magistarium says so, and that's the point.
After all, if Catholics only had to believe those two things--namely, the Immaculate Conception and the Assumption--infallibly defined by popes, Catholicism would be one boring (and meaningless) religion indeed.