Ever since the publications of both Archbishop Carlo Maria Viganò and Auxillary Bishop Athanasius Schneider on whether or not the 2nd Vatican Council contains doctrinal errors, people have now been motivated to reconsider the question. Although I have written many articles that bear great relevance to this question (see links below), I’ve decided to write a brief summary of the conceptual seed of what has been going on since the emergence of the 20th century (although it precedes this, especially in the non-Catholic spheres of thinking) in the Catholic Church, is tried by the bishops of the 2nd Vatican Council, and is tested in the forthcoming decades.
Certain men, in their asserted desire to “bring all things into one,” attempt to integrate the Lord Jesus Christ and the world by focusing on the former as the Logos of “all things.” As such, this involves everything that is true, good, and beautiful. Therefore, everything that is true, good, and beautiful is somehow a participation in the one divine logos, the Word made flesh. This means that even the Devil himself, because he partakes of being, has something to him that is true, good, and beautiful. If that is true, then so does even the mass of fallen humanity. And if in the mass of fallen humanity, then also in the activities of that mass [some, at least]. So now, instead of a whole-sale rejection of non-Catholic, non-Christian, and even pagan religions/practices, there is now a calculated partitioning between what is good and bad in them. That calculation is made for the purpose of trying to figure out just how to merge the Christian and the non-Christian in a variety of intersectional religiosity.
So far, this is not heretical, and it is not incorrect…. technically speaking.
But there is a plan in all of this emphasis.
It used to be that Catholics were always required to manifest the singularity of the fullness of what is good, true, and beautiful in the revelation given by Jesus Christ through the Apostles and deposited in the Church, to be guarded and defended by the successors to the Apostles. Thus, it had always been denied to Catholics to pray with heretics, and even more so with non-Christians such as Jews, Muslims, and especially pagans. The idea was that by doing so, indifference would be bred by the act, and thus a violation of divine law committed. This is how the reasoning goes in the old stipulations of the holy office (now, CDF).
But the bishops in the 20th century began to emphasize that there is a way to get around this. Going back to that partition between good and bad in all things, Catholic theologians began to speculate on how Catholics could join up with non-Catholics, at least to the degree of that which is held by the non-Catholic that is good, true, and beautiful. Nice formula! Join where we agree and divide where we disagree!
There was a nasty little addition.
What was added was that non-Catholics should be presumed to be inculpable of their errors, and thus even the pagans, immersed in error as they are, are possibly invincibly ignorant of the bad, lies, and ugly that they are involved in…. which means that we can join up with them somehow in the areas of the good, true, and beautiful.
This is what established greater cohesion in, not just ecumenical dialogue, but ecumenical prayer, worship services, and eventually the meeting of Assisi (1986). Here, members of all religions were brought to Assisi, and were both instructed and requested by the leadership of Pope St John Paul II to activate their own method of divinizations, and Pope John Paul defended this (in a subsequent address to the cardinals in Dec. 1986) by an appeal to the fact that there is a common participation in the good by all men, albeit to different degrees. Catholics have the privilege of the fullness, whereas non-Catholics, of whatever stripe, have it in partiality. But we can ADJOIN in the partiality, and by fiat, pretend we aren’t ADJOINING in the bad.
This edifice of (1) asserting a common participation in the good by everyone (regardless of they are repentant believers or not), (2) the presumption of invincible ignorance as the better possibility, and (3) the common action of religious service, eventually made its way into moral theology (although it had already been there for a long time in the general scholarship), which gave way to the enthronement of a theology of private conscience and the vast complexity of the human psyche. See it perfectly explained/defended here in a small video by Bishop Robert Barron.
Conscience was enthroned.
If you add all of this together, you can begin with the un-heretical premise of a common participation of all things in the good, true, and beautiful. Then you add the un-heretical (albeit imprudent) presumption of invincible ignorance in the infidels. Then you add the speculation of how to manage a *joint* service in religion, only intersecting on those points of commonality. Then you add that one’s own conscience dictates the rightness/wrongness of particular actions.
So far the recipe is not explicitly heretical. This is why Vatican II is so frustrating. You can’t nail down the heresy like you could with Arius, Nestorius, Eutyches, Photius, Martin Luther, and the rest. Because the problem is not an error of proposition, but rather in a demonic invasion of imprudent speculations, and an obsession with all the different possibilities that might be construed given the vast complexity of conscience and the human psyche.
So that is my summary.
Case in point: It is the above recipe which leads to speculative moral thinking like that of Cardinal Blase Cupich who thinks its entirely possible for openly gay couples to be both in a state of grace, receiving communion, grow in grace from communion, all the while still engaging in homosexual acts. He reasons that since there is some common participation in good between the couple, there is probably a great deal of mitigation to moral responsibility due to X or Y, there is an engagement of a least some virtues amidst the vices, and then there is the vast complexity of conscience.
You have a technically-orthodox way to achieve “heresy.”
Apply the same recipe to the doctrine of salvation outside the Church, the necessity of communion with the Church under the Pope, the requirement to abide by the moral law, etc,etc. It can yield the same result of taking any wayward situation and turning it into something religiously legitimate.
And so, to the question of whether Vatican II taught heresy, the answer must be in the negative. There are no propositions, to my knowledge, that can’t be read in an orthodox manner. However, as I’ve shown, that does not mean that the basic thinking framework of some of its parts can’t be used as a recipe to create a disaster upon souls which is just as good as pushing heresy. And perhaps it is that level of speculation that makes for the massive confusion and disdain for the reforms following.