Fr. Corapi often said that what God teaches is immutable or unchanging. This teaching has been preserved in the Church for over 2,000 years. Anything concerning moral and faith is immutable.
In Protestantism which started in 1530 by Martin Luther, he teaches two doctrines faith alone and Scripture Alone. None of these were taught in the Jesus Christ, his Apostles, the Apostolic Fathers, and the ECF. Faith Alone and Scripture are new doctrines that divides the revelation of God.
I often heard from James White, a Baptist apologist accused the Catholic Church as Sola Ecclesia. That is a false accusation. The Church operates in three principles. It teaches divine revelation through Sacred Scripture, Sacred Tradition, and Magisterial Teachings (The interpreter). None of these three can be separated or be taken apart.
Fr. Corapi said it best. Where ever there is Sacred Scripture, there is also Sacred Tradition, and Magisterial teaching. Where ever there is Sacred Tradition, there also Sacred Scripture and Magisterial Teaching. Where ever there is Magisterial Teaching, there is also Sacred Tradition and Sacred Scripture. It operates like, wherever there is the the Son, there the Father and Holy Spirit will be.
The Protestantism doctrine of Sola Scripura and Sola Fideli divides. It is a new doctrine and therefore it is not from God. Rather it doctrine are man-made as a result of selfish men on both sides.