Second, I’ll quote “The Doctrinal Authority of Papal encyclicals” by Msgr. Joseph Clifford Fenton
<< These documents have come to be recognized as the most frequently used vehicles of the Holy Father’s ordinary teaching of the flock entrusted to his care.
Despite their manifest and unique importance, however, the papal encyclicals have never been given anything like a completely adequate treatment in the literature of sacred theology.
Some of the text-books used in our seminaries today give no special consideration whatever to the doctrinal authority of these documents.
Others content themselves with a sweeping over-simplification and blithely dismiss all the encyclicals as “non-infallible” pontifical statements.
A third group of authors, more scientific in their approach to this problem, maintain that these documents contain some infallibly true teachings, doctrines presented as infallible on the authority of the encyclicals themselves. Even within this last-mentioned group, however, we find most frequently little detailed explanation of the various norms by which we can recognize infallibly authoritative statements of the Holy Father’s ordinary magisterium in his encyclical letters.
All the theological works dealing with this subject make it perfectly clear that all Catholics are bound seriously in conscience to accept the teaching contained in these documents with a true internal religious assent.
They all insist that even in this portion of his ordinary magisterium the Holy Father has the right to demand, and actually has demanded, a definite and unswerving internal assent to his teaching from all Catholics.
An astonishingly large number of prominent theologians can be found among those who take no adequate cognizance of the encyclical letters in their treatises on papal infallibility. These men content themselves with an examination of and a theological demonstration for the formula by which the Vatican Council defined the Holy Father’s infallibility. As a group these writers frequently give the impression that they consider only those truths proposed by the Holy Father solemni iudicio as infallibly defined, to the exclusion of those truths which he sets forth ordinario et universali magisterio.
The distinguished theologians who deny the papal encyclicals the status of infallible documents teach, none the less, that the faithful are bound in conscience to accord these letters not only the tribute of respectful silence, but also a definite and sincere internal religious assent.
This authority (of the papal encyclicals) is undoubtedly great. It is, in a sense, sovereign. It is the teaching of the supreme pastor and teacher of the Church. Hence the faithful have a strict obligation to receive this teaching with an infinite respect. A man must not be content simply not to contradict it openly and in a more or less scandalous fashion. An internal mental assent is demanded. It should be received as the teaching sovereignly authorized within the Church.
The magisterium of the Church has been equipped with help from God by reason of which the first sort of teaching gives infallible truth, while the second affords infallible security. Employing the plentitude of its power, the teaching Church operates as the auctoritas infallibilitatis. Working, not to define, but merely to take those steps it deems necessary to safeguard the faith, it is the auctoritas providentiae doctrinalis. To this auctoritas providentiae doctrinalis and to the teachings it sets forth, the faithful owe the obedience of respectful silence and of an internal mental assent according to which the proposition thus presented is accepted, not as infallibly true, but as safe, as guaranteed by that authority which is divinely commissioned to care for the Christian faith.
It might be definitely understood, however, that the Catholic’s duty to accept the teachings conveyed in the encyclicals.
The authority which imposes this obligation is that of the Roman Pontiff himself. To the Holy Father’s responsibility of caring for the sheep of Christ’s fold, there corresponds, on the part of the Church’s membership, the basic obligation of following his directions, in doctrinal as well as disciplinary matters. In this field, God has given the Holy Father a kind of infallibility distinct from the charism of doctrinal infallibility in the strict sense. He has so constructed and ordered the Church that those who follow the directives given to the entire kingdom of God on earth will never be brought into the position of ruining themselves spiritually through this obedience. Our Lord dwells within His Church in such a way that those who obey disciplinary and doctrinal directives of this society can never find themselves displeasing God through their adherence to the teachings and the commands given to the universal Church militant. Hence there can be no valid reason to discountenance even the non-infallible teaching authority of Christ’s vicar on earth.
It is and it remains the business of Catholic theologians to adhere faithfully to the teachings of the encyclicals and to do all in their power to bring this body of truth accurately and effectively to the members of Christ’s Mystical Body. >>