There is truth and there is the truth.
First a little story. A man is a first time passenger on a great ocean liner of infamy. After some loud noises, the massive ship begins to drastically list. Fear begins to enter into the heart of the man, who is concerned for his family and all the other souls on board. He spies a presumably knowledgeable ranking officer on the deck and puts the question to him. "Sir, the ship is listing badly. Are we all going to drown?" With indifference, the officer says truthfully "I assure you, we will ALL not drown." So the man thanks the officer and runs off to tend to his family. Within a few hours, the man and his family are dead in the freezing ocean. Being dead, it is difficult to ascertain whether the man is comforted by the fact that the Ship's officer technically told him the truth.
We have had discussion around the Catholic internet and here on this website about whether or not there is potentially anything to fear from the upcoming Synods on the family.
In many of these discussions, some writers rely on a few basic truths to allay any and all such fears about the outcome of the synods.
Truth #1. Not to worry, the Church and even the Pope are incapable of changing doctrine. Can't happen. Phew!!
Well, it is true. The Church cannot alter or refute her own doctrine. But what exactly does that guarantee you? Not much it turns out, the guaranteed protection of the Holy Spirit is quite limited. The Church is perfectly capable of doing great damage to the faith with sins of commission and omission when it comes to infallible doctrine. This brings us to Trope #1 which is often used to prove the above, but which actually proves the contrary.
Trope #1. The great document, Humanae Vitae proves this infallibility! In a time of great upheaval, Pope Paul VI confirmed the truth about artificial contraception in the face of enormous pressure to do otherwise. What a great victory for the Church! Huzzah!!
So yes, it is the truth that Pope Paul VI upheld the Church's teaching on artificial birth control. It is also the truth that the Church leadership has been a disgrace on the topic.
In the lead up to Humanae Vitae, Pope St. John XXIII established and Pope Paul VI expanded the Pontifical Commission on Birth Control which recommended allowing artificial birth control. They also allowed the report of the "Pontifical commission" to be publicly available for years and so establish in the minds of many Catholics that such behavior was just fine and established among many others an expectation that the Church would change its teaching on the matter. During these years, many people made up their minds on the topic. Much of the damage was already done before the issuance of Humanae Vitae.
Then Pope Paul VI issued Humanae Vitae upholding the Church's doctrine on the matter. Yay! The Pope did what the Pope had no choice but to do! Yay!
Then what happened? There was an open revolt against the document by many clergy in the Church. And what did the Church do about it? Nothing. As a result, more and more people who looked at their rebellious clergy as authoritative on the matter and they too used contraception. Some were confused and they waited to see what the Church would do about it. When the Church did nothing, they understandably concluded that it must not be really that big a deal if the Church does nothing to stop it and so they went along too.
And then what happened? Aside from an occasional speech that few heard or a document that nobody read, the practical Church went silent on the topic for 45 years. The result? By some indications, 95% of Catholics during these years have contracepted. 95% of Catholics have committed a grave sin which imperils their immortal souls.
But hey! The Church didn't change Her doctrine! A great victory!! Great job infallible Church!
So there is truth and there is the Truth.
So no, the Church cannot change her teaching on the indissolubility of marriage. Great. But it is also clear that it is entirely unnecessary to do so. Those who reject that doctrine, or at least its practical meaning in reality, have also learned the lessons of Humanae Vitae. It is entirely unnecessary to change doctrine when you can simply undermine it with expectation, unsuppressed rebellion, and silence.
Is there reason to fear this will happen again? Only if you take the words of the Papal hand-selected keynote speaker on the topic seriously, which the Pope certainly seems to do. And only if you take the organizer of the synod seriously.
So yes, the truth is the Church's teaching are immutable. But history shows us that Church leadership can practically undermine the immutable by rendering them moot in the minds of many. This is not to say that the Church WILL undermine marriage in the Synod, prayer can do much! I have no prophetical gift, but I do have reason. I think it is perfectly reasonable to have a healthy degree of caution that the Church could mishandle the topic with a repeat of the Humane Vitae debacle.
To bring this post to a conclusion, I will save some other truths told as lies for another time.