In the Holy Bible, we read, "If I (St. Paul) am delayed, you may know how one ought to behave in the household of God, which is the church of the living God, the pillar and bulwark of the truth. Without any doubt, the mystery of our religion is great..." [1 Tim. 15-16]
In the aforementioned passage, two things stand out. Paul refers to:
i. The Church is the pillar and bulwark of the truth, and
ii. Our religion.
Most Protestants believe that the Bible is the pillar and foundation of the truth. They also believe that no knowledge outside of the Bible is necessary for salvation.
Such a belief, "Sola Scriptura," (meaning only need the Bible) cannot be found anywhere in the Bible. Not only that, they fall short of recognizing that Saint Paul was referring to "our religion, the Roman Catholic Church and its Rites, the only One, Holy, Catholic and Apostolic Chruch that was instituted on earth by Jesus Christ.
The Protestant argument that the Bible is the pillar and bulwark of the truth does not make any sense for two reasons:
i) It was not until the fourth century that the Catholic Church completed its selection of the "canon of Scripture." The Bible could not be the pillar and bulwark of the truth prior to the fourth century because the Holy Bible did not exist.
ii) It was not until the 1600's that the first Bible was printed. Prior to those days, very few Bibles were available, such being hand written and owned by the Church and/or the rich, these being kept under lock and key. So the average person had no access to the Bible. He could not use the Bible as a reference to support that it was the pillar and bulwark of the truth. In fact, the people turned to the Church to learn the tradition, the doctrines, the teachings of the Catholic Church.
The truth is that it is only during the last four hundred years that the Protestants have made claim that the Bible is the pillar and bulwark of the truth. Prior to that, they could not make such a claim because they had no access to the Bible.