In the discussions prompted by the recent news about the publication in the Acta Apostolicae Sedis (AAS) of two documents pertaining to the interpretation of Amoris laetitia, many people seem to have picked up the idea that the Authentic Magisterium is infallible, as if this were a case of Roma locuta est, causa finita est. But this is not true. Whatever else this recent publication in the AAS may mean, it does not mean that anything has been definitively answered or decided.
The authentic magisterium, to which the faithful owe religious submission of will and intellect (Lumen gentium 25; cf. CIC 752), is not infallible. This is what Lumen gentium says about the authentic magisterium of the pope and the bishops:
In matters of faith and morals, the bishops speak in the name of Christ, and the faithful are to accept their teaching and adhere to it with a religious submission of the soul (religioso animi obsequio). This religious submission of will and intellect (religiosum voluntatis et intellectus obsequium) must be shown in a special way to the authentic Magisterium of the Roman pontiff, even when he is not speaking ex cathedra; that is, it must be shown in such a way that his supreme Magisterium is acknowledged with reverence and that the judgments made by him are sincerely adhered to, according to his manifest mind and will.
Now it should be clear from the reference to the authentic magisterium of the pope “even when he is not speaking ex cathedra,” that this text is talking about non-infallible teaching. But in case that isn’t clear, let me direct your attention to the official notes on this text provided by the Theological Commission at Vatican II in order to explain its meaning to the bishops before they voted on it. When this particular paragraph was added to the second draft of the schema on the Church, the explanation was that it had been added “in order to further determine which assent ought to be given to the teaching of the authentic Magisterium below the grade of infallibility” (Acta Synodalia Sacrosancti Concilii Vaticani II, 2/1, p. 255). Again, in the third draft, the paragraph was relocated with the explanation that this was because “it seemed better to treat of the non-infallible magisterium of the Roman pontiff in the context of the magisterium of the whole episcopal body” (Ibid., 3/1, p. 250).
There should be no doubt, therefore, that when we are talking about the authentic magisterium of the pope, we are not talking about infallible teaching. The pope is only infallible when he speaks ex cathedra. And that is usually referred to as his solemn or extraordinary magisterium. Not his merely authentic magisterium.
However, in case that is not clear enough, let me add a second proof from Pope St. John Paul II’s Catechesis on the Church. In his general audience of March 24, 1993, he clearly and explicitly asserts that the pope speaks infallibly “only (‘solo’) when he speaks ex cathedra.” Now we have it from Lumen gentium 25 that the pope exercises his authentic magisterium “even when not speaking ex cathedra.” So if he is infallible only when he speaks ex cathedra, then he is not infallible when he does not speak ex cathedra, even if he is exercising his authentic magisterium.
Here is another dilemma for anyone who thinks that the authentic magisterium of the pope cannot teach error: John Paul II was exercising his authentic magisterium in the general audience mentioned above, but it certainly didn’t meet the requirements for speaking ex cathedra. So either John Paul II was right and the pope is not infallible in his authentic magisterium when not speaking ex cathedra, or he was wrong. But if one were to argue that he was wrong, then it would mean that he taught something false in his authentic magisterium. In other words, his own error would prove that he was right after all. No matter which way you slice it, the conclusion necessarily follows that popes can teach error in their authentic magisterium when they are not speaking ex cathedra.
Let me insert a brief logic lesson here for the 2+2 = 5 crowd. If it’s not infallible then it’s fallible. And if it’s fallible, then it could be in error. Deny that and you may as well walk right through the door marked Abandon Reason All Ye Who Enter Here.
Now all of this has to be borne in mind in order to understand what is really required by a “religious submission (obsequio) of will and intellect” to the teaching of the authentic magisterium of the pope or of the bishops.
Normally, of course, it means that the teaching in question should be accepted as true, though with the awareness that it could be false. In the scholastic terminology this is the kind of assent characteristic of opinions rather than knowledge. When I say I know that something is true, my assent is certain. When I say I think that something is true, my assent is given, but without certainty and with a recognition of the possibility of error.
Due to the assistance of the Holy Spirit given to the Church, we can be sure that instances of error in this kind of authentic teaching are rare. And yet since they are possible, our response must also take that into account. So what does the obligation of religious submission mean for Catholics in individual cases of teaching from the authentic magisterium? I think it can be summed up best by saying that we should accept that teaching as true precisely to the extent that it does not conflict with irreformable Catholic doctrine.
 The term ‘authentic magisterium’ can be used in a broad or a narrow sense: in a broad sense, it can be used to refer to all official magisterial teaching, whether infallible or not; it is usually used in a more narrow sense to refer to official teaching that is not infallible, but is still authoritative. This is the sense in which it is being used here.