What did the early Christians believe when the Bible was NOT yet compiled, when what was to become the New Testament was NOT yet written? They had the fullness of truth, God's Word preserved orally in the Apostolic Tradition. Think about the early Church and what they did when proclaiming the Gospel and in worship when they had no New Testament. They still had the fullness of the deposit of faith. When that Church compiled their Bible, they didn't throw out the fullness of truth, the Apostolic Tradition. Their Bible commanded them to hold fast to that Tradition. People who came later in 1500s (the many Protestant traditions), the 1800s (the Mormon tradition) certainly can be intelligent, quote verses, and know their tradition backwards. Everyone doesn't read the Bible the same way. They read the Bible differently than the Church of the first century. They have something different than those that held fast to the Apostolic Tradition. You can take a look at what Eastern Orthodox believed as it is an Apostolic faith and compare it to the tradition that you hold, if you prefer.