Apologeticae sive Theologiae Fundamentalis, Tomus II (Pars Altera): Demonstratio Catholica

The ordinary pontifical magisterium is exercised as often as the pope proposes a truth without the manifest intention of defining it infallibly. This he does indeed: by sending encyclical letters, in which matters of faith are set forth without the cathedral form being employed; by responding to the various questions through decretal letters; by publishing or commending catechisms and other books destined for the instruction of the faithful;¹ by prohibiting books dangerous to faith or morals; by noting propositions as rash, scandalous, offensive to pious ears, etc.; finally, by giving any doctrinal judgments whatsoever which are not definitive, but rather directive and, as it were, provisional, according as it has been necessary or opportune and sufficient for the security of doctrine.

The authority of the ordinary pontifical magisterium, although it is not peremptory and definitive, is nevertheless very great. For the Roman pontiff, although teaching in an ordinary manner, acts with the primatial power of feeding divinely committed to him, even if he does not use the whole intensity of this power. Whence all the sheep of Christ are bound to hear the voice of the supreme shepherd and to conform themselves to his magisterium. Indeed, the Church has always held in the highest esteem the magisterium of the supreme pontiff, both as infallibly judging the faith and heresies and as authentically condemning opinions dangerous to the faith and fostering heresy. Rightly, therefore, canonical law lays down: "It is not enough to avoid heretical depravity, but one must also diligently flee those errors which approach it more or less; wherefore all must also observe the constitutions and decrees by which depraved opinions of this kind have been proscribed and prohibited by the holy see."²