15 So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter.

Scripture tells us to hold onto the Traditions, both the oral teachings of the Apostles, as well as the written Scriptures.

The Protestants have taken seven books out of the Old Testament; Martin Luther tried to take seven more out of the New Testament. Luther added the words "alone" and "only" to St. Paul’s writings when he said people are justified "by faith alone" or they are justified "only by faith." The only place where the Bible actually mentions being justified by faith alone is James 2:24 "You see that a man is justified by works and not by faith alone." The Bible explicitly says that we are not justified by faith alone but by works, too. Therefore, the Catholic Church has always taught what the Scripture teaches on this and on other things.

The Bible contains many riches. When the Catholic Church defines a doctrine that is not explicitly mentioned in the Bible, like the Blessed Trinity, it is because the Scripture texts use other words to get that same idea across. The Church clarifies the doctrine when somebody denies the doctrine. That is her duty as the Church of Jesus Christ. However, she never contradicts the Scriptures.

Let me recommend a few sources for you to examine for further reading: The Catechism of the Catholic Church; Catholicism and Fundamentalism, by Karl Keating (Ignatius Press); Radio Replies, Frs. McCarty and Rumble (Tan Press). These and other books will be a good place to continue to examine the claims and teachings of out Catholic Church.