As we've discussed often, the Deposit of Faith (the Truth about faith and morals) does not change. Jesus entrusted the Deposit of Faith to His Apostles, and that Truth has been handed down, intact, for over 2,000 years. The Church is not static, however. She is a living thing, a supernatural reality that grows and deepens in richness and understanding over the centuries.
This deeper and richer understanding of the Truth is called "development of doctrine". Development of doctrine is not, as some critics of the Church claim, a fancy way of disguising a reversal or change or contradiction of teachings. Quite the opposite; Church teaching does not change. However, under the guidance of the Holy Spirit, the Church is able to unpack the beauty of Church teaching as we go along through salvation history.
Here's an easy analogy:
Imagine you are in a room with the lights down low. The room is filled with furniture, objects, colors. In the dimly lit room, you can make out the outlines, the general shapes and placement of things, and some muted colors.
Now imagine that someone turns the dimmer on the light switch up, gradually. Slowly, over time, you start to see the details you had not been able to see before, you see the colors start to come alive. As the light continues to be turned up, you see even finer details, and more vibrant colors bursting forth.
The room and the objects have not changed nor reversed themselves. Nothing has moved or been inverted, nothing has been added to the room, and nothing has been removed. But you can see everything more clearly, with more detail, color, richness, depth. Our understanding and appreciation of the room is more profound than before, and we see the beauty and reality of it in ways we hadn't when the light was more dim.
This is development of doctrine!
Now a word about theologians, who are very important in the life of the Church.
There is a widely-held misconception that the job of a theologian is to come up with theological truths. But, this is a complete misunderstanding of the theologian's role!
The only legitimate arbiter of the Truth, the only divinely-authorized keeper and protector of the Deposit of Faith, is the Magisterium of the Catholic Church, not the Church's theologians. The Magisterium of the Church is the teaching authority of the Church, comprised of the body of bishops in union with the pope.
We go to the Apostolic Church to know what is doctrinally true.
So what, then, is the role of Catholic theologians?
Well, going back to the room analogy, their job is to turn up the lights. They illuminate the details in the room so that we can explore the treasures all around us and see the colors more deeply. Theologians help plumb the depths and uncover the riches of the Deposit of Faith that was given by Christ to His Church.
Once a Catholic theologian puts himself and his work in opposition to the Deposit of Faith, he has overstepped the bounds of his profession. He has wandered into error and forgotten his role and sacred responsibility. He has left the room, so to speak.
So, a Catholic theologian does not determine or decide what is Christian teaching, but rather he helps the faithful understand Christian teaching more deeply and profoundly, reflecting and addressing the specific circumstances and challenges of every era.
The distinction is crucial, and if you should come across a Catholic theologian who disagrees with Church teaching, that's a red flag. He is not grounded in Truth, so his work is built on a foundation of sand.
The authentic Catholic theologian is one who begins with faithful obedience to the teachings of the Magisterium and goes from there. This is a theologian with integrity, who will bring about authentic development of doctrine. This is a theologian who helps to fulfill Christ's promise to lead us into all Truth, in every age.