During its first 1,500 years the Catholic Church ruled all Christianity. The Old Heresy Trail was filled with footsteps of the Judaizers, the Gnostics, the Docetists, the Marcionists, the Montanists, the Manichaeans, the Arians and many more. The passing parade came, strutted across the stage of history, and returned to the obscurity from which it came.
The State ruled corporal life and commanded armies while the Church ruled spiritual life. The Church, however, was supreme because it had the power to excommunicate the king.
Vatican II had been well-intentioned. Many issues had accumulated during the past century, and it was time to resolve them. Among them, one in particular is relevant to the subject of Protestant Christianity. It was not much mentioned in the documents but it was very much there.
Then, during the 1500s, the Protestant Reformation gravely wounded the Church’s supremacy. A Protestant king could no longer be intimidated. By the 1960s the Church still had authority within her own parishes but in the wider community a Protestant-secular axis ruled the roost. Vatican II set out to attract Protestant denominations back to the Catholic Church by making it look more Protestant.
The Protestant doctrines were chaotic, so Vatican II resolved to hold fast to Catholic substance while ceding its appearance, continuing to pray the Second Ecumenical Council’s Nicene-Constantinople Creed every Sunday morning as it had since AD 381 while accepting Protestant appearance in language (vernacular replacing Latin), architecture (man-based horizontal lines replacing God-based vertical lines), and disciplines (versus populum replacing ad orientem, Friday abstinence reduced from year-round to Lent-only, etc). It is striking that we can drive past a Catholic parish church today and instantly tell whether it was built before or after 1965.
Completely apart from the matter of preference, Vatican II failed to accomplish its objective. Catholic families became greatly confused over what the Church believed, so Catholic parents stopped teaching their children apologetics, catechesis, and evangelization. When a Protestant kid asked his Catholic friend why he was a Catholic, the Catholic friend could only say, “Because my parents are Catholic.” When the Catholic kid grew up he didn’t teach his own children because he didn’t know, and so on.
Pope Paul VI realized that he needed a new Catechism to replace the Trent Catechism, but he knew it would take a long time, and it did. From 1965 to 1992 we had no Church-published Catechism. We’re starting to recover, but with two generations of no-catechism it’s a long road back.