Isa. 35:8, 54:13-17 - this prophecy refers to the Church as the Holy Way where sons will be taught by God and they will not err. The Church has been given the gift of infallibility when teaching about faith and morals, where her sons are taught directly by God and will not err. This gift of infallibility means that the Church is prevented from teaching error by the power of the Holy Spirit (it does not mean that Church leaders do not sin!)
Matt. 16:19 - for Jesus to give Peter and the apostles, mere human beings, the authority to bind in heaven what they bound on earth requires infallibility. This is a gift of the Holy Spirit and has nothing to do with the holiness of the person receiving the gift.
Mark 8:33 - non-Catholics sometimes use this verse to down play Peter’s authority. This does not make sense. In this verse, Jesus rebukes Peter to show the import of His Messianic role as the Savior of humanity. Moreover, at this point, Peter was not yet the Pope with the keys, and Jesus did not rebuke Peter for his teaching. Jesus rebuked Peter for his lack of understanding.
Luke 22:32 - Jesus prays for Peter, that his faith may not fail. Jesus’ prayer for Peter’s faith is perfectly efficacious, and this allows Peter to teach the faith without error (which means infallibly).
*In other words, if non-Catholics argue that Peter ( and his successors) had no infallibility, they have to argue that the Father did not answer Jesus’ prayer. *
Italics mine.
John 11:51-52 - some non-Catholics argue that sinners cannot have the power to teach infallibly. But in this verse, God allows Caiaphas to prophesy infallibly, even though he was evil and plotted Jesus’ death. God allows sinners to teach infallibly, just as He allows sinners to become saints. As a loving Father, He exalts His children, and is bound by His own justice to give His children a mechanism to know truth from error.
Gen. to Deut.; Psalms; Paul - Moses and maybe Paul were murderers and David was an adulterer and murderer, but they also wrote infallibly. God uses us sinful human beings because when they respond to His grace and change their lives, we give God greater glory and His presence is made more manifest in our sinful world.
Gal. 2:11-14 - non-Catholics sometimes use this verse to diminish Peter’s evident authority over the Church. This is misguided. In this verse, Paul does not oppose Peter’s teaching, but his failure to live by it. Infallibility (teaching without error) does not mean impeccability (living without sinning). Peter was the one who taught infallibly on the Gentile’s salvation in Acts 10,11. With this rebuke, Paul is really saying “Peter, you are our leader, you teach infallibly, and yet your conduct is inconsistent with these facts. You of all people!” The verse really underscores, and not diminishes, the importance of Peter’s leadership in the Church.
more at
http://www.scripturecatholic.com/the_church.html#the_church-IV
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