Many Protestants object to the Catholic Church by claiming it never believed, in previous times, certain articles of faith that it professes to believe now. They claim this because the Church only authoritatively declared these articles as dogma centuries or millennia later.
Catholics usually respond that the Magisterium (teaching authority of the Church) most often declares something to be dogma in precise formulations after the matter in question is contradicted by heretics.
This is not a modern Catholic apologist cop-out. It is precisely the same answer given by St. Augustine.
He (and other Church Fathers) explains that God uses heretics to rouse the Church’s mind to better understand the Faith and Scripture. This is based on St. Paul’s words to the Corinthians: “for there must be heresies among you in order that those who are genuine among you may be recognized” (1 Cor. 11:19).
When such things occur, God raises up great Catholic teachers, whose teachings are often authoritatively recognized by the Church to be good and true. Indeed, this is precisely what happened at the Council of Jerusalem in Acts 15—heretics were disturbing the mind of the Church (“unsettling your minds,” as verse 24 says), and the Church responded with an authoritative pronouncement after discussing the matter, invoking both their own authority and God’s.
This is not a sixteenth-century argument, nor a fifth-century argument, and definitely not a nineteenth-century argument (as some allege, attributing this idea of “doctrinal development” to St. John Henry Newman). It has been happening for 2,000 years in the Catholic Church. It is how God uses even his enemies to benefit his Church.
Here is a fascinating and illuminating quote from St. Augustine on this topic (Exposition of Psalm 55, §21):
Therefore many men that could understand and expound the Scriptures very excellently, were hidden among the people of God: but they did not declare the solution of difficult questions, when no reviler again urged them.
For was the Trinity perfectly treated of before the Arians snarled thereat? Was repentance perfectly treated of before the Novatians opposed? So not perfectly of Baptism was it treated, before re-baptizers removed outside contradicted; nor of the very oneness of Christ were the doctrines clearly stated which have been stated, save after that this separation began to press upon the weak: in order that they that knew how to treat of and solve these questions (lest the weak should perish vexed with the questions of the ungodly), by their discourses and disputations should bring out unto open day the dark things of the Law…