Being wrong is one thing; being wrong because you don’t know any better is another thing entirely. So St Augustine writes:
If, Honoratus, a heretic, and a man trusting heretics seemed to me one and the same, I should judge it my duty to remain silent both in tongue and pen in this matter. But now, whereas there is a very great difference between these two: forasmuch as he, in my opinion, is an heretic, who, for the sake of some temporal advantage, and chiefly for the sake of his own glory and pre-eminence, either gives birth to, or follows, false and new opinions; but he, who trusts men of this kind, is a man deceived by a certain imagination of truth and piety. [De utilitate credendi 1]
I suppose I could add another option (besides just being mistaken) to the non-pejorative possibilities for those who disagree with us: being deceived. And St Augustine shows here that different types of errors warrant different sorts of responses. Generally speaking (for those of us who do not happen to be Doctors of the Church…) the first sort of response ought to be in the range of humility.
But I digress. The point that I wished to make with this post is that there is nothing novel in the Catholic Church’s insistence that the sons and daughters of actual heretics (that is, those who have been formally condemned by the Church as such) are not guilty of formal heresy when they follow in their parents’ footsteps. They err, certainly, if they believe the same heretical things, but they are just not in the same boat with the leaders.
But though the doctrine which men hold be false and perverse, if they do not maintain it with passionate obstinacy, especially when they have not devised it by the rashness of their own presumption, but have accepted it from parents who had been misguided and had fallen into error, and if they are with anxiety seeking the truth, and are prepared to be set right when they have found it, such men are not to be counted heretics. [Letter 43]
So we see that Augustine agrees with the Catholic Church. We should not be surprised to learn that this is the case; after all, he was Catholic. He doesn’t use the words “material heresy,” but the idea is clearly present, as is the distinction between that and formal heresy. There’s nothing “progressive” or “liberal” about the Church saying today that Protestants are our brothers in Christ by virtue of their baptism, nor in denying that they are subject to the anathemas of Trent. It’s simple justice.