There are two types of false teachers of Catholicism. The first openly disagrees with Church teaching. Sometimes they even explain Church teaching correctly, but then they disagree, preferring their own thinking to that of Christ and His Church.
I recall a theology professor in college who taught ethics. She correctly taught that some acts are intrinsically evil and therefore always immoral. But then she would argue her own point of view, which is that, in principle, nothing is always wrong. She argued that contraception and abortion were not always wrong. And she was pregnant at the time. (Her due date was so close to the date for final exams for the class that she almost didn’t make it to the exam.) It was surreal to have a pregnant theology professor arguing that abortion isn’t always wrong. But she did, to her credit, present Church teaching correctly.
The other type of false teacher is much worse. They teach grave errors along with the claim that it is merely the correct understanding of magisterial teaching. The uniformed reader will have no way of knowing that this is false. At least, with the other type of false teacher, they tell you what the Church actually teaches. This type of false teacher is very dangerous to souls.
Some of these false teachers, who claim error is doctrine, err out of pride, ignorance, and incompetence. They actually believe that they have presented truth to their readers. But others, I strongly suspect, know that they are teaching a grave distortion of magisterial teaching. They correctly understand what the Church teaches, and reject that teaching, and decide to lie to the faithful, to trick them into believing the errors that they prefer over the teaching of Christ and His Church.
This type of teacher cannot be in the state of grace. The matter of the act is grave: teaching serious errors on matters of faith, morals, and salvation to a large number of souls. They do so knowingly and very deliberately. They continue for many years teaching grave errors knowingly. All the elements of actual mortal sin are present, to a high degree. This is one of the worst actual mortal sins that a person could commit.
But the root of the problem is not the particular teachers. It turns out that their theological arguments are not so subtle or clever that they cannot be easily refuted. There is nothing in their work which could not be duplicated by a large percentage of the sinful members of the Church. They are easily replaceable. If they were to retire, other false teachers would quickly take their place.
The root of the problem is the sinful members of the Church, who wish to sin gravely, while pretending to be faithful. There are many Catholics who will happily openly reject Church teaching, thinking their own understanding to be better. And they prefer the type of teacher who is like them, who also openly rejects magisterial teaching. But, especially among conservatives, some sinful Catholics want both: to pretend to be faithful Catholics who believe what the Church teaches, while instead committing whatever sins they enjoy.
This type of sinner seeks out any priest or theologian who will tell them that their own grave sins are just and holy. This type of sinner praises and supports anyone who provides that particular service. They despise the first type of false teacher, because they don’t want to be seen as rejecting Church teaching (even though that is what they are doing). They glory in the second type, so that they can live a devilish life while pretending to be angelic souls.
The Church is in a very dire state today. Soon She will face a terrible crisis, because so many of Her children have decided, one way or another, to reject truth.
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