Catholics believe that the understanding of the Church
about Mary, as about all Christian truth (e.g., the understanding
of the Trinity) deepens and becomes more accurate over
the centuries under the guidance of the Holy Spirit.
"When the Advocate comes whom I will send you from
the Father, the Spirit of truth that proceeds from
the Father, he will testify to me."
"I have much more to tell you, but you cannot bear
it now. But when he comes, the Spirit of truth, he will
guide you to all truth."