Within the Catholic faith there is what we call a “hierarchy” of revealed truth. Within that hierarchy the dogma of the Trinity is higher than the dogma of the perpetual virginity of Mary. So, it is true that the Trinity is a dogma that is more central to our faith than that of Mary’s perpetual virginity. However, both dogmas are taught with dogmatic certitude by the Church and so both must be held as true by faithful Catholics.
Perhaps the deeper issue here is the Church’s authority. It is understandable that it can rankle to be told, “The Church teaches it so you must believe it.” It sounds a bit like the perennial parental dictum, “You have to do it because I say so.” But it may help to understand why the Church has the authority to tell Catholics what is true.
Jesus knew that his earthly ministry would last only about three years. He also knew that Christians of all time would need authoritative assurance on what they were to believe. So he invested his apostles and their successors with his own authority to teach Christians. He told his apostles:
[Jesus said]: “He who hears you hears me, and he who rejects you rejects me, and he who rejects me rejects him who sent me” (Luke 10:16).
When we listen to the Church, we are listening to the apostles and to their successors; thus we are, in turn, listening to Jesus himself. To be a Christian means to be a follower of Christ. If Christ tells us to listen to those whom he has given his own authority to teach us then we obey him by obeying them.
For more information please see the resources linked below. God bless.
Brethren of the Lord
Mary: Ever Virgin
To Know Christ Jesus by Frank Sheed