We share so much with our Protestant friends, from the love of our Lord Jesus to the Sacred Scriptures. Because of these shared treasures, there is a temptation to overlook our separated status as a lamentable but unchangeable fact of history. This temptation is exactly what the enemy wants. He wants to see division among Christians, a scandal for the world and an obstacle to faith for many. This is such a crucial issue that it was a focus of prayer for our Lord (John 17:21).
Let us work toward unity. As Catholics, we must proceed with respect, joy and love for our separated brethren, inviting them into full communion with the Holy Catholic Church. For any Protestants reading this, please consider the possibility that, if you have not heard about Church teaching directly from Catholic sources, you may hold some misconceptions about Church teaching. One resource is the Catechism of the Catholic Church, which you can access for free online and can search for any topic:
Protestants should cherish their relationship with the Lord as they do, but their ecclesiological position is built on quicksand. This can be shown with just two issues that touch on the core of Protestant belief: the doctrine of the Trinity and the canon of the New Testament.
Protestants hold the doctrine of the Trinity as dearly as Catholic do. Protestants may claim that this doctrine is clearly taught in the Bible. To be sure, the Scriptures do provide much support for the Trinitarian position. On the other hand, anyone interpreting the Scripture on their own might select a number of verses to oppose the Trinitarian position, such as John 14:28. Jehovah's Witnesses are one modern example of a faith community that has rejected the Trinity based on their reading of Scripture, as their official website explains:
In the early Church, a priest named Arius began teaching that Jesus was not an eternal being like the Father and that "the Son has a beginning, but that God is without beginning." The Council of Nicea, with over 300 Catholic bishops from across the Roman Empire, was called in 325 A.D. to further define the Trinity and it condemned the Arian position. Despite this, Arianism continued to flourish during the fourth century. The key question here for Protestants is this: If well-meaning and Bible-reading followers of Christ can reject the doctrine of the Trinity, what authority makes this a doctrine that all Christians must believe?
The Protestant reply to this question may be mixed. A few might actually accept that the Arian position was a valid interpretation based on Scripture. Some might accept the authority of the Council of Nicea but then where did the Church ever get the authority to have a Council issue binding teaching for all Christians? Some Protestants will insist that this doctrine is a clear teaching of Scripture, and that no one could miss it, despite the existence of the Jehovah's Witnesses, Mormons, Arians, and others who have missed it. In any case, this answer presupposes the canon of Scripture, which leads into our second question.
While Catholics can have confidence in the canon of the New Testament from Sacred Tradition and the Magisterium (including councils and synods of the Catholic Church), Protestants reject these sources of authority. So, what authority do Protestants trust to tell them which writings belong to the New Testament? This is a dangerous question which Protestants will try to ignore. The logic is plain: to have an infallible New Testament, you need an infallible authority to say which writings belong in the New Testament and which do not. The "table of contents" must be divinely inspired as well.
The Protestant view is typically that the canon was reached by consensus (a backdoor way of accepting the authority of tradition without explicitly saying it), or based on the obvious merits of the text.
The first option is such a persistent belief because it has some truth to it. The four Gospels, the Acts of the Apostles, and Paul's letters were widely accepted as canonical with extraordinary speed and very little debate within the early Church. However, the problem is that such was not the case for the Catholic epistles and the book of Revelation, which are now also considered to have an equal, divinely-inspired, infallible status within the canon.
The second option is difficult to accept once you understand that the very first time that our 27 New Testament books are listed as the canon by a Church Father is not sometime shortly after the final book (Revelation) was written, but by St. Athanasius in 367 A.D. In the meantime, several other writings were read in liturgical settings, implying that they had a canonical status. Apparently, the canon was not so obvious based on the merits of the text to Christians for over three hundred years.
Did Martin Luther have a solution for this? Actually he decided to remove at least two New Testament books, James and Jude, from his canon!
One Protestant scholar, R.C. Sproul, has famously described the canon as a "fallible list of infallible books." Does that make sense to you? Is that how a Christian should read the Bible, always with a lingering uncertainty about whether he is reading a book that is actually God's word?
Debate over the New Testament canon basically ended in the early fifth century, shortly after synods of the Catholic Church clarified the issue. That is precisely how the Church reached a "consensus." But this is the very authority structure that Protestants reject.
As Catholics, we know that Jesus did not give the apostles a book. He gave them the deposit of faith, which has been explicated over time through the Sacred Scriptures, Sacred Tradition, and the Magisterium. This is a consistent position, in harmony with the real history of the Christian movement and with Jesus' words that "he who hears you, hears me" (Luke 10:16) as the Church has spoken through councils and synods. This confirms our confidence in the canon of Scripture.
Please share this article with your Protestant friends and see what they have to say about these two questions of authority. As separated brethren, we must be able to question the basis of each other's beliefs, with charity, speaking the truth in love (Ephesians 4:15). This is one path toward the full unity that is the will of Jesus for His followers.