Mike, I appreciate your respect in asking this question. I like it when people are genuinely seeking answers, rather than being self-righteous or antagonistic. I must tell you, however, that there is absolutely positively NO Scriptural support, whatsoever, for the doctrine of Sola-Scriptura. Sola-Scriptura is about as far from “infallible” a doctrine that we can possibly get. With over 33,000 different denominations of Protestants that all claim “Sola-Scriptura,” yet all believe different things, we can CLEARLY and DECISIVELY conclude that individual interpretation of Scripture is anything but “infallible,” or “authoritative,” and that the doctrine of Sola-Scriptura is by NO means, “verified.” Scripture is NOT self-explanatory. All Scripture is true, but not all individual interpretation of Scripture is true, even if one genuinely believes that such interpretation is guided by the Holy Spirit. To believe “Sola-Scriptura” is to be DECEIVED into thinking that you are trusting the Bible alone, when in reality, you are trusting your own comprehension skills, which can easily be tainted by personal bias and prejudices, misunderstandings, or false teachings of others who were in error.
For example, no offense, but your understanding of Deuteronomy 13 and Deuteronomy 18 are both totally off. Deuteronomy 13 tells you not to follow people who try to lead you to worship other gods, even if their signs and prophecies come true. Deuteronomy 18 talks about prophets, telling us that if someone prophesizes something that does not come true, then the prophesy was not from God. Neither of those chapters of Scripture have anything to do with the Church’s authority to define doctrines, interpret Scripture, and preserve the true faith. They merely are giving examples of people not to trust, nowhere providing any formula to verify trustworthiness, but giving examples that can conclude that a prophet is NOT trustworthy. If you are looking for miracles or signs to trust that someone speaks for God, heed the warning in Matthew 24:24. If you are looking for a conclusive formula to “test spirits,” you’ll find that in 1 John 4:2-3, but even that is for spirits, not people. To understand the Church’s authority, you need to see that it was authority established by Christ, Himself.
Christ established His Church (Matthew 16:18-19) which is refered to as the “pillar and bulwark of truth” (1 Timothy 3:15.) That Church gave us the New Testament. If you don’t believe that the Church first had the authority to write and canonize the New Testament, by what logic can you trust the New Testament? It didn’t just magically fall from the sky. Realize that the New Testament comes from the Church, not the other way around. The New Testament, as we know it, today, was not canonized until the late 300s. Also, the “Word of God” is not limited to the written letter. (See 2 Thessalonians 2:15). Sola-Scriptura suggests that people can place more trust in their own personal interpretations of Scripture, than they can trust in Christ’s ability to found a Church that can infallibly teach truth, under the guidance of the Holy Spirit (John 16:13). Read Proverbs 3:5, and realize that the doctrine of Sola-Scriptura outright contradicts Scripture.
There is much more I can say in opposition to Sola-Scriptura, as I can give countless examples of how people have been led astray through their personal interpretations of individual verses of Scripture, but I hope that I made my point clear. While the Bible is 100% true and inspired, individual interpretation of the Bible is NOT. Christ wanted unity (John 17:20-21), and therefore established am authoritative Church that would guide us in all aspects of the faith, including Sacred Tradition, the interpretations of the existing Hebrew Scriptures(Old Testament), and the writing, canonization, and interpretation of the new Scriptures.(New Testament.) This Church can speak with ONE voice, under authority of the Pope (successor of Peter) something that Sola-Scriptura does NOT allow, since Sola-Scriptura makes individual people into their own personal popes, often causing hatred and division, even within the same denominations. Again, the 33,000+ denominations of “Sola-Scriptura” Protestants, as opposed to the One Holy Catholic and Apostolic Church should be enough evidence to prove the point I am making. I sincerely hope this helps you, Mike, and that my words are taken as a genuine heart-felt correction and do not come across antagonistically, as such is not my intent. May God be with you.