Pastor Aeternus actually made four doctrinal statements about the Office of the Pope: 1. St. Peter's primacy over the Church conferred by Jesus; 2. The permanence of that primacy in the pontiffs succeeding St. Peter; 3. The power and authority of the pontiffs in teaching dogma and morals, discipline, and governance of the Church; and what everyone remembers, 4. 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.
Father Juan Velez explained Blessed John Henry Newman's reactions to the definition in this article for ZENIT in 2010:
[In his Letter to the Duke of Norfolk] Cardinal Newman repeated the teaching of the constitution "Pastor Aeternus"
of Vatican Council I, which asks Catholics for obedience to the Pope only in
matters of faith and morals, and in matters of discipline and ecclesiastical
government. Cardinal Newman explained that by obeying the Pope in such matters,
the moral conscience is neither eliminated nor substituted by the Pope's
As Vatican I asserted, the Pope's authority extends only to matters of
doctrine and morals. We are obliged to believe, for example, what he teaches
about the Holy Eucharist or marriage. His teaching does not extend on how to
organize the water supply of a city, raise taxes, run elections, etc.
Cardinal Newman explained to his fellow Englishmen, who out of prejudice
considered the teaching of the Pope's infallibility as a threat to English
government or sense of pride, that this doctrine does not make Catholics
puppets: did the Pope speak against Conscience in the true sense of the word, he
would commit a suicidal act. He would be cutting the ground from under his feet.
His very mission is to proclaim the moral law, and to protect and strengthen
that "Light which enlighteneth every man that cometh into the world." On the law
of conscience and its sacredness are founded both his authority in theory and
his power in fact…I am considering here the Papacy in its office and its duties,
and in reference to those who acknowledge its claims.
Cardinal Newman pointed out that so many types of acts by a Pope, such as the
excommunication of a person in error or the Pope's blessing of the Spanish
Armada, are not a matter of exercising his pontifical authority in an infallible
manner, which would bind the faithful in conscience. Cardinal Newman wrote that
Catholics are not bound by the Pope's personal character or private acts, but by
his formal teaching (although it should be pointed out that, in the case of a
person excommunicated, that is a canonical act that is indeed binding, whether
or not it is infallible).
If a scholar were to disagree with a doctrinal or moral teaching of the
Church he should submit his judgment to the Church's teaching out of humility
and obedience. Here too Cardinal Newman offered advice and good example. A
theologian or for that matter a pastor should not create unrest among the
faithful, much less confusion. Such a person should have the humility to admit
that his opinion is likely mistaken, especially if the magisterium has already
pronounced on the matter.
Upon being received in the Church Cardinal Newman accepted all its teachings,
including the ones he did not fully understand. As the declaration of papal
infallibility drew near, Cardinal Newman accepted this teaching, even if he
thought that despite its truth it was not an opportune moment to make it. The
English hierarchy had only just been restored in England in 1850, and there was
a lot of prejudice against Catholics in England. In that country the so-called
Ultramontane Catholics who advocated a temporal power by the Pope were making
matters worse. In sum, Cardinal Newman thought this was not the best time for
such a declaration, but he submitted to it.