The argument goes like this:
1) Consider the Bible simply as a historical document.
2) Existing copies are in substantial agreement and the Bible is the most credible ancient document of that era.
3) No credible historical argument can be made that Jesus did not claim to build His Church on Peter (establishing the office of the papacy-see above) and that the gates of hell would not prevail against It. Jesus also called His Church "the pillar and foundation of truth."
4) History shows an unbroken lineage of Popes from the time of Peter –an unprecedented historical phenomenon.
5) If the Church is "the pillar and foundation of truth" then It could never have taught error, nor could it teach contradictory doctrine. In fact, the Church has never promulgated false doctrine. The Church also posesses a body of non-contradictary doctrine. Both are singular historical accomplishments.
6) The argument provides moral certainty or proof beyond a reasonable doubt that Jesus existed, Jesus is who He claimed to be, and that the Catholic Church is His Church.
7) The Catholic Church determined the canon of scripture and teaches that it is the inspired Word of God.
8) We can know with moral certainty or proof beyond a reasonable doubt that the Catholic Bible is the Word of God.
Furthermore, you have the evidence of miracles (like Lanciano) showing that Church doctrine is true and healing miracles attributed to Saints that prove that these miracles cannot be attributed to Satan ("a kingdom divided...").
The Mormons have a line of succession..and they say they have the keys to the kingdom ..and they agree with you that the scriptures are only correct if they are properly interpreted ..and they are led by a prophet...
How can you prove that you are correct and they are wrong?