Question: If I claim that my faith is entirely based on Scripture, how could I claim to have an infallible understanding of salvation? But if I rely on the teaching of the Catholic Church, I can be sure that my faith is correct because the Church is infallible.

Answer: Do you want me to admit that I don’t have an infallible understanding of salvation? No problem, I admit it! I do not have an infallible understanding of salvation, since I am fallible; I am liable to make mistakes and I can understand the infallible Bible wrongly. That is not to say, however, that in fact I misunderstand the Gospel, for a fallible person can be given grace by the Holy Spirit to understand His Word correctly, even though he is not infallible. Together with millions of fallible human beings throughout history, I rejoice and thank God that, “we know that the Son of God has come and has given us an understanding, that we may know Him who is true; and we are in Him who is true, in His Son Jesus Christ. This is the true God and eternal life” (1 John 5:20).

Well, then, how does this help you? How does my fallibility verify the necessity of an infallible church? Let's see...

If you claim that your faith is entirely based on "scripture plus tradition as interpreted by an infallible Church", can you claim that your understanding of salvation is infallible? Think for a minute! If you are honest, you will reply something like this: "No, because I am fallible (like my Protestant friend, I too can make mistakes) and so it is possible that I misunderstand the infallible Church! (Even if for the sake of argument we assume that the Catholic Church is infallible!)

God has given us an infallible Bible. God's Word is true! We do well to read it for ourselves and to listen to godly teachers who can help us understand it better. Ultimately, only the Lord can open our mind to understand His Word correctly. “For it is the God who commanded light to shine out of darkness, who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ” (2 Corinthians 4:6).