ONe more section from this lovely book that addresses your earlier quote of what I said there Trifecta,
Infallible Popes Versus the Infallible Word of God
Whereas history clearly testifies to these and many other instances of papal error, lawlessness, indecisiveness, and general confusion, the Roman church nevertheless maintains its position that the pope is completely infallible in matters regarding faith and morals when speaking ex cathedra, or "from the Chair [of Peter]." He can make no mistakes in official declarations of what must be believed by the body of Romanists at large. The Catholic Encyclopedia makes this point very clear: "The Roman Pontiff, when he speaks ex cathedra -- that is in the exercise of his office as pastor and teacher of all Christians he defines... a doctrine of faith or morals to be held by the whole Church -- is, by reason of the Divine assistance promised to him in blessed Peter, possessed of that infallibility... and consequently such definitions of the Roman Pontiff are irreformable."(7)
Romanists, like Protestants, claim to receive the Holy Scriptures "with piety and reverence"(8) and insist that "the Bible is everywhere true in the sense intended by the individual sacred writer."(9) It is at this point that the Romanist finds himself on the horns of a dilemma: since both the Bible and papal decrees are viewed as the inspired and infallible Word of God, which of the two possessed the higher authority in the event of a contradiction (which is not an infrequent ocurrence)? Two allegedly infallible, yet disagreeing, sources of revelation both cannot be right; one must give place to the other. This problem does not confront those who seriously heed the Apostle's warning in 1 John 4:1: "Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world." Likewise, in 1 Thessalonians 5:21, we are commanded to "prove all things; hold fast that which is good." How are we to "try the spirits" and "prove all things"? We must do so by the written Word of God alone, as did the Bereans in the First Century (Acts 17:11). The Bible is our measuring rod, or our "once for all delivered" canon (Jude 3), by which all truths claims are to be tested. Without this sure foundation of Scripture, we are only left with our own personal judgments, or those of our fellow men -- both of which are fallible, as we have seen in the preceding chapters and will continue to see evidenced in those to follow.