Part the Last.
What other powers does the pope have? As part of his papal primacy, the pope also has the full authority of ecclesial teaching. That is, there is no ecclesial teaching authority that he does not have. Nor is there any teaching authority higher than his. (Contra Gallicanism.)
He has the power to teach infallibly on faith and morals and on what pertains to faith and morals (the so-called secondary objects of infallibility). He also has ordinary teaching authority.
As with all Magisterial teachings, one must read the latest pronouncements in the light of the foundation of the past. This is because the latest pope is bound by Tradition and Scripture and these have already authoritatively been interpreted and he and all the baptized are bound to adhere to these interpretations and to these Fonts of Revelation. (Contrary to the rumors of academics, Vatican II did not dispense with this expression ‘fonts of revelation’ even though it did not employ the expression. These are indeed the fonts of revelation when we speak of the articulated expression of the Person and Teachings of Jesus Christ. Where do we find these articulated expressions? In Tradition and Scripture. Thus, they are fonts. The rumors alluded to are red herrings rather unhelpful for the theological enterprise. What Vatican II left explicitly undecided – though it does implicitly teach in this matter – is whether or not Scripture contains everything found in Tradition. No explicit teaching in this regard. However, the implication is clear: No. Where? For instance, the Church gains her knowledge of what books belong in Scripture not from Scripture but from … Tradition! Thus spake Vatican II, Dei Verbum, 8).
Back from the digression. We must therefore situate all recent papal teachings of lesser authority in the context of the absolute truths already infallibly proclaimed. Further, we must situate all recent papal teachings of lesser authority in the context of all the long established papal teachings reiterated over the decades and centuries. Nor is silence of a matter, even prolonged silence, a reason not to hold an established, much less an infallible, teaching. It is also the case, of course, that an infallible teaching in the year 2015 would contextualize all less than infallible and earlier teachings. But antiquity is a key principle. Why? Because seldom are teachings issued infallibly. And it takes time to “establish” a teaching. Since more time is past than is present, already established papal teachings must be a firm anchor of context for almost all later teachings.
That said, I would add one final note. Pius XII lucidly stated that the living Magisterium is the proximate source of theology. What he means is that the living Magisterium, insofar as it voices authoritatively on a subject, provides the theologian with the living insight into past teachings. Thus statement should not be understood in a “dialectical” sense: I.e. it should not be read as meaning that later teachings can mitigate or water down earlier teachings. Rather, it should be understood in the sense that later teachings can help the current person focus on the key matters at stake today and on the meanings of ancient expressions. It is part and parcel of Pius XII’s message, also, that he understood the papal Magisterium to be bearer of a “perennial” mode of expression. Thus, the Magisterium in his time undertook the self-discipline to express itself in a language and thought long tried and true, very precise. So that one could clearly see the line of development leading up to the latest promulgation.
We really cannot say that this mode of expression has been preserved. And since it has not been preserved, many Catholics have thought that previous teachings have themselves been abandoned. That is an error. They have not. And since confusion reigns, I think it very salutary for people to go back and get good solid grounding in Magisterial texts from Pius IX through Pius XII and in the councils of Trent and Vatican I. These are foundational. They presuppose and clearly carry through the achievements of the early councils, which are also crucial: Nicaea through Constantinople III.
The “perennial” philosophy and theology as a very mighty weapon for the Church, to fight confusion and to dispel errors; a very lucid torch whereby to illuminate the world. Unfortunately, some people could not see the real meaning of this language and wanted something more “up to date” or “personally edifying”. Well, that is all fine; provided that one does not lose one’s bearings in the “personal” focus. Thus, some good combination of recent expressions, which bring out the personal, and the classic (which speak from the perennial philosophy) is probably the best recipe for success.
In a nutshell: The pope is servant of Christ, of the Church, of the Tradition, of Scitpure, and of the flock. And that is why he has his authority. If a pope were not to make use of his authority so to feed the flock, I suppose this would be possible. A pope could decide not to use this authority because its use might be taken to be un-ecumenical. However, whether such an action would be wise is a very different matter.