Catholicism, being an unBiblical faith, must necessarily undermine the authority and sufficiency of scripture. Many Catholics claim that the Bible gets its authority from the Church, not the other way around. To justify this assertion, many Catholics argue that the Bible itself did not exist prior to 390 A.D. In their view, the councils of Carthage (397 A.D.) and Hippo (393 A.D.) created the Bible, meaning that the Church must ultimately hold more authority than the Bible.
But Catholics also admit that the Bible is inspired by God. This creates a huge plot hole in the argument. A simple question to ask such Catholics is were the scriptures inspired before they were canonised?
If their answer is no, that is both illogical and blasphemous. First, it is illogical, because inspiration comes before manifestation, not after. How can you write what you are not inspired to write? As an author, I can tell you now that a lack of inspiration is called "writer's block", and it is the bane of any author's life. Thus, the Bible must have been inspired before it was canonised.
It is blasphemous because it literally sets the human councils above the word of God. Look throughout history. God spoke to His servants, His servants passed down those words, anyone who obeyed prospered, anyone who disobeyed was punished. No one got to decide whether or not the word of God was the word of God. It really is quite simple: Given a choice between God's word and man's word, God wins, no argument.
But all of that is academic. No Catholic worth his salt is ever going to argue that the scriptures didn't become inspired until the Church decided it was so. Which leaves us with the obvious conclusion that yes, the scriptures were inspired before 390 A.D. What that means is that the Councils did not create the Bible, but at best formally recognised the Bible (and I say at best because evidence from long before Carthage or Hippo shows that the canon was largely agreed upon quite early). That which is scripture has always been scripture. That which is not scripture has never been scripture. No council has ever had the authority to add or remove books from the canon. Doing so is sin, and yields its own punishments (Deuteronomy 4:2; Proverbs 30:5-6; Revelation 22:18-19).
We see, then, that the argument that the Catholic Church has greater authority than the Bible because it produced the Bible is not only wrong from a historical point of view, but is also logically and theologically impossible.
Now for the real problem. Even Catholicism acknowledges that the scriptures are the inspired words of God. Regardless of where the Church claims to get its authority, it is literally claiming authority over the word of God. How can this not be blasphemy? How can it be even remotely possible for a body of sinful human beings to claim to have more authority than the written declarations of the Lord Himself? The very claim that the Catholic Church holds such authority proves indisputably that it doesn't.
But it needs to claim such authority. Without authority over the word, the word holds authority over the Church. That causes problems for the Catholic Church, because the Bible is certainly not a Catholic book. The most notable difference between the two is the emphasis on works in the Gospel. While Catholics believe we are saved by grace and works, the Bible says we are saved by grace, not works (e.g. Ephesians 2:8-9). It even goes as far as to define grace as being the antithesis of works, and thus we cannot possibly be saved by both (Romans 11:6). With authority over the word of God, the Catholic Church can ignore that. Without authority over the word of God, those verses mean what they say, and no Church will ever be able to choose whether or not to believe it. But as we've shown, they cannot possibly have that authority over the word of God. So where does that leave us?