I don't see how that follows from what I said. But it is no doctrine of Catholicism that Church leaders are infallible. Rather, the doctrine holds that the Church is infallible in "her objective definitive teaching regarding faith and morals", according to the promise of Christ.
-A8
http://catholicoutlook.com/rock2.php
Protestant Scholars Agree: Peter Is the Rock
Quotations from Protestant scholars who agree that Matthew 16:18 refers to Peter personally
by Gary Hoge
One day, when Jesus was in the region of Caesarea Philippi, he asked his disciples, Who do people say the Son of Man is? (Matt. 16:13). The disciples gave a variety of answers before Peter finally said, You are the Christ, the Son of the living God (Matt 16:16). What happened next is the subject of some controversy:
Jesus replied, Blessed are you, Simon son of Jonah, for this was not revealed to you by man, but by my Father in heaven. And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it. I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven (Matt. 16:17-19).
To whom or to what was Jesus referring when He said, On this rock I will build my Church? What rock was He talking about? Catholics, noting that the name Peter (Greek: Petros) is really just the masculine form of the Greek word for rock (petra), say He was referring to Simon son of Jonah. If theyre right, if the Church was to be built in some sense on Peter himself, as head of the apostles, then this supports the Catholic doctrine of the papacy. Naturally, Protestants arent comfortable with that at all, and so historically, they have claimed that the rock to which Jesus referred was Peters faith, or perhaps, Christ Himself.
But as the passions of the Reformation era have cooled, and Protestant scholars have taken a more dispassionate look at this text, they have come to agree more and more that Jesus was referring to Peter himself as the rock. Of course, they disagree with the Catholic interpretation of what this means, but many now agree that the Catholic explanation of the grammar of the text is correct.
The following quotations, all of which are from Protestant Bible scholars, are taken from the book Jesus, Peter & the Keys: a Scriptural Handbook on the Papacy (Scott Butler et al., (Santa Barbara, CA: Queenship Publishing), 1996).
William Hendriksen
Member of the Reformed Christian Church, Professor of New Testament Literature at Calvin Seminary
The meaning is, You are Peter, that is Rock, and upon this rock, that is, on you, Peter I will build my church. Our Lord, speaking Aramaic, probably said, And I say to you, you are Kepha, and on this kepha I will build my church. Jesus, then, is promising Peter that he is going to build his church on him! I accept this view. (New Testament Commentary: Exposition of the Gospel According to Matthew (Grand Rapids, MI: Baker, 1973), 647.)
Gerhard Maier
Leading conservative evangelical Lutheran theologian
Nowadays a broad consensus has emerged which in accordance with the words of the text applies the promise to Peter as a person. On this point liberal (H. J. Holtzmann, E. Schweiger) and conservative (Cullmann, Flew) theologians agree, as well as representatives of Roman Catholic exegesis. (The Church in the Gospel of Matthew: Hermeneutical Analysis of the Current Debate, Biblical Interpretation and Church Text and Context, (Flemington Markets, NSW: Paternoster Press, 1984), 58.)
Donald A. Carson III
Baptist and Professor of New Testament at Trinity Evangelical Seminary
Although it is true that petros and petra can mean stone and rock respectively in earlier Greek, the distinction is largely confined to poetry. Moreover the underlying Aramaic is in this case unquestionable; and most probably kepha was used in both clauses (you are kepha and on this kepha), since the word was used both for a name and for a rock. The Peshitta (written in Syriac, a language cognate with Aramaic) makes no distinction between the words in the two clauses. The Greek makes the distinction between petros and petra simply because it is trying to preserve the pun, and in Greek the feminine petra could not very well serve as a masculine name. (The Expositors Bible Commentary: Volume 8 (Matthew, Mark, Luke), (Grand Rapids, MI: Zondervan, 1984), 368.)
The word Peter petros, meaning rock (Gk 4377), is masculine, and in Jesus follow-up statement he uses the feminine word petra (Gk 4376). On the basis of this change, many have attempted to avoid identifying Peter as the rock on which Jesus builds his church. Yet if it were not for Protestant reactions against extremes of Roman Catholic interpretations, it is doubtful whether many would have taken rock to be anything or anyone other than Peter. (Zondervan NIV Bible Commentary New Testament, vol. 2, (Grand Rapids, MI: Zondervan, 1994), 78.)
John Peter Lange
German Protestant scholar
The Saviour, no doubt, used in both clauses the Aramaic word kepha (hence the Greek Kephas applied to Simon, John i.42; comp. 1 Cor. i.12; iii.22; ix.5; Gal. ii.9), which means rock and is used both as a proper and a common noun. . . . The proper translation then would be: Thou art Rock, and upon this rock, etc. (Langes Commentary on the Holy Scriptures: The Gospel According to Matthew, vol. 8, (Grand Rapids, MI: Zondervan, 1976), 293.)
John A. Broadus
Baptist author
Many insist on the distinction between the two Greek words, thou art Petros and on this petra, holding that if the rock had meant Peter, either petros or petra would have been used both times, and that petros signifies a separate stone or fragment broken off, while petra is the massive rock. But this distinction is almost entirely confined to poetry, the common prose word instead of petros being lithos; nor is the distinction uniformly observed.
But the main answer here is that our Lord undoubtedly spoke Aramaic, which has no known means of making such a distinction [between feminine petra and masculine petros in Greek]. The Peshitta (Western Aramaic) renders, Thou are kipho, and on this kipho. The Eastern Aramaic, spoken in Palestine in the time of Christ, must necessarily have said in like manner, Thou are kepha, and on this kepha. . . . Beza called attention to the fact that it is so likewise in French: Thou art Pierre, and on this pierre; and Nicholson suggests that we could say, Thou art Piers (old English for Peter), and on this pier. (Commentary on the Gospel of Matthew, (Valley Forge, PA: Judson Press, 1886), 355-356.)
J. Knox Chamblin
Presbyterian and New Testament Professor, Reformed Theological Seminary
By the words this rock Jesus means not himself, nor his teaching, nor God the Father, nor Peters confession, but Peter himself. The phrase is immediately preceded by a direct and emphatic reference to Peter. As Jesus identifies himself as the Builder, the rock on which he builds is most naturally understood as someone (or something) other than Jesus himself. The demonstrative this, whether denoting what is physically close to Jesus or what is literally close in Matthew, more naturally refers to Peter (v. 18) than to the more remote confession (v. 16). The link between the clauses of verse 18 is made yet stronger by the play on words, You are Peter (Gk. Petros), and on this rock (Gk. petra) I will build my church. As an apostle, Peter utters the confession of verse 16; as a confessor he receives the designation this rock from Jesus. (Matthew, Evangelical Commentary on the Bible, (Grand Rapids, MI: Baker, 1989), 742.)
Craig L. Blomberg
Baptist and Professor of New Testament, Denver Seminary
Acknowledging Jesus as The Christ illustrates the appropriateness of Simons nickname Peter (Petros = rock). This is not the first time Simon has been called Peter (cf. John 1:42), but it is certainly the most famous. Jesus declaration, You are Peter, parallels Peters confession, You are the Christ, as if to say, Since you can tell me who I am, I will tell you who you are. The expression this rock almost certainly refers to Peter, following immediately after his name, just as the words following the Christ in v. 16 applied to Jesus. The play on words in the Greek between Peters name (Petros) and the word rock (petra) makes sense only if Peter is the rock and if Jesus is about to explain the significance of this identification. (The New American Commentary: Matthew, vol. 22, (Nashville: Broadman, 1992), 251-252.)
David Hill
Presbyterian minister and Senior Lecturer in the Department of Biblical Studies, University of Sheffield, England
On this rock I will build my church: the word-play goes back to Aramaic tradition. It is on Peter himself, the confessor of his Messiahship, that Jesus will build the Church. The disciple becomes, as it were, the foundation stone of the community. Attempts to interpret the rock as something other than Peter in person (e.g., his faith, the truth revealed to him) are due to Protestant bias, and introduce to the statement a degree of subtlety which is highly unlikely. (The Gospel of Matthew, The New Century Bible Commentary, (London: Marshall, Morgan & Scott, 1972), 261.)
Suzanne de Dietrich
Presbyterian theologian
The play on words in verse 18 indicates the Aramaic origin of the passage. The new name contains a promise. Simon, the fluctuating, impulsive disciple, will, by the grace of God, be the rock on which God will build the new community. (The Laymans Bible Commentary: Matthew, vol. 16, (Atlanta: John Knox Press, 1961), 93.)
Donald A. Hagner
Fuller Theological Seminary
The natural reading of the passage, despite the necessary shift from Petros to petra required by the word play in the Greek (but not the Aramaic, where the same word kepha occurs in both places), is that it is Peter who is the rock upon which the church is to be built. . . . The frequent attempts that have been made, largely in the past, to deny this in favor of the view that the confession itself is the rock . . . seem to be largely motivated by Protestant prejudice against a passage that is used by the Roman Catholics to justify the papacy. (Matthew 14-28, Word Biblical Commentary, vol. 33b, (Dallas: Word Books, 1995), 470.)