[Dr. Jeff is “digging himself into a deeper hole”; he concedes that some are calling him a fool or a knave; I do not, because I prefer to argue “ad rem” rather than “ad hominem”; in this case I call(ed) his argument(s) “dubious at best and absurd at worst”]
By Dr. Jeff Mirus | Sep 15, 2016
Necessary Distinctions: Recently I have written both to defend the Pope from the charge of heresy and also to insist that his own private interpretation of Amoris Laetitia does not tell us anything about what that act of the Magisterium requires us to believe. Given the distinctions necessary to such discussions, I suspect I have baited many people into denouncing me as either a knave or a fool.
Some think that to exonerate the Pope from the charge of heresy is to praise his policies, which does not follow at all. Others laugh at me for believing that a gravely evil action can be only venially sinful. But the Church has always taught that awareness of the gravity of the evil and full consent of the will are both always required for a person to be guilty of a mortal sin. This is part of Catholicism 101.
Papal Intentions: Still others have mocked me publicly for explaining that Pope Francis’ private comments on Amoris Laetitia are definitely not a legitimate guide to whatever Magisterial teaching that document might contain. But that ought to be self-evident. The Pope may privately explain what he intended or what he meant; but the Holy Spirit might well have prevented him from fully capturing his intention in the Magisterial document in question.
Indeed, in some cases, that is how the Holy Spirit must work to preserve the Church from error. He may well simply prevent the Pope from accurately stating some point which he had personally intended to make in the exercise of his Magisterium. In fact, Pope Francis’ very odd behavior on this whole issue (“bizarre” was the appropriate word used by another Catholic commentator, Robert Royal) looks suspiciously like the work of a man whom the Holy Spirit simply won’t allow to come right out and Magisterially teach something that is false.
I have said before that sometimes the guaranteed protection of the Holy Spirit is most obvious in the failure of a pope to formally teach what, by all the signs, he seems to want to teach.
Spiritual Complexity: In relation to all these distinctions, I am indebted to one of our readers in New Zealand, Peter Howard, for emailing me a fascinating quotation from Pope Pius XI’s encyclical on Christian Marriage (Casti Connubii, 1930). This encyclical addresses, among other problems, the deliberate frustration of the procreative end of the marital act (this was before “the pill”, which raised new questions leading to Paul VI’s Humanae Vitae in 1968). In number 54 of Casti Connubii, Pius XI clearly teaches: “Since, therefore, the conjugal act is destined primarily by nature for the begetting of children, those who in exercising it deliberately frustrate its natural power and purpose sin against nature and commit a deed which is shameful and intrinsically vicious.”
But, as Howard noted, the Pope then made the following stipulation:
Holy Church knows well that not infrequently one of the parties is sinned against rather than sinning, when for a grave cause he or she reluctantly allows the perversion of the right order. In such a case, there is no sin, provided that, mindful of the law of charity, he or she does not neglect to seek to dissuade and to deter the partner from sin. 
I confess that I missed this distinction for a long time, and have even counseled some people incorrectly. What the Pope teaches authoritatively here is that when one spouse insists on frustrating the procreative end of marriage despite the objections of the other, then the other does not sin in using the marital act for its unitive ends, as long as he or she continues to try to persuade the erring spouse to recognize the evil of contraception and cease to insist on it.
Takeaway: Do I think this translates directly to the sins we have been discussing in invalid marriages? No. But it shows how careful we must be, including me. We dare not settle moral questions without study, still less by the assumption that our own perceptions of reality are free from error, and should be “obvious” to all.