That's interesting because we have other sources posted here that say the supreme authority for Catholics is either the pope or the "Church".
Pope Pius XI asserted salvation is dependent on obedience to the supreme authority of St. Peter and his legitimate successors, and while the popes are not, yet another said, Holy Scripture is invested with supreme authority by reason of its sure and momentous teachings regarding the faith. Whatever, then, it tells us of Enoch, Elias and Moses - that we believe. We do not, for instance, believe that God's Son was born of the Virgin Mary simply because He could not otherwise have appeared in the flesh and 'walked amongst men' - as Faustus would have it - but we believe it simply because it is written in Scripture; and unless we believe in Scripture we can neither be Christians nor be saved. (http://www.vatican.va/holy_father/benedict_xv/encyclicals/documents/hf_ben-xv_enc_15091920_spiritus-paraclitus_en.html)
Yet what this really means is that Scripture only has authority Rome gives it as being the supreme authority, since the only list of books and interpretations of them that have any authority according to Rome, is that which she gives, while actual warrant from Scripture is not necessary for Rome's doctrines, for she declares truth by fiat, for if she "infallibly" declares something then it is true and cannot be wrong, including that she is infallible. J. Smith presumed the same it seems.
Do you believe that the Gospels (written by the Gospel writers) are infallible? If so, did the writers of the Gospels write infallibly because of their own personal infallibility, or did they write infallibly because of the infallibility provided them by God? (Or do you think God did NOT provide those writers with infallibility when writing those Gospels?)
You have to be able to grasp that Jesus Christ founded His Church, just like He solemnly promised, and He has NOT abandoned His Church, and He said that the gates of hell would NOT prevail against her, and that the Holy Spirit would always guide her. Take Jesus at His word.