The argument for the authority of the Catholic Church is not a circular argument that relies on the conclusion it is trying to establish as one of the premises of the argument. Instead, it is as Karl Keating describes in his book Catholicism and Fundamentalism a spiral argument where the different elements are related but not identical.
In his book Keating says that the authority of the Church does not come from the Bible because the Bible is the inspired Word of God. Instead, if we examine the Bible as an ordinary set of historical documents written in ancient Greek we find that there is good evidence that Jesus of Nazareth rose from the dead and established one Church upon the Apostles, with Peter as the head of the Church.
This authority gives us confidence that the texts gathered into the Biblical canon are inspired. So the argument is not circular. We believe in the Church because we believe in the Bible as a set of reliable, though man-made, historical documents. But then, as Augustine says, we are moved to believe in the inspiration of these biblical books, or their divine authorship, by the authority of the Catholic Church.
