Augustine's Multiple References to Peter as the "Rock": a Response to Rome's Defenders

This is an addendum to my earlier blog entry: What Was Augustine "Retracting" on Peter, The Rock, and Mathew 16? That entry exegetes Augustine's likely final statement on his interpretation of Matthew 16:18-19.  His later view was that Peter was not the "Rock" the church was founded upon (he admits in his earlier writings he did put forth the opposite view that Peter was the "Rock" the church was founded upon). Augustine's later view is contrary to the modern view espoused by Rome's defenders, for instance, this apologist says, "Only Simon, among all the other personages of the New Testament, received a name change (cf. Matt. 16:18-19). This signified his status as the "rock" upon which Christ would build his Church." Who's correct, Augustine or modern Roman Catholic apologists? 

In response to Protestants bringing up Augustine's later view, some of Rome's defenders have located a number of times Augustine referred to Peter as the "Rock," This webpage states, "Far from repudiating the Catholic understanding of Matt 16:18, I will provide testimony from Augustine to show he interpreted Matt 16:18 in various ways during his life and not exclusively equating "this rock” with Christ Himself." What I've noticed in the quotes they've mined out is the distinction Augustine himself makes between his earlier and later writings on Peter and the "Rock" is blurred or non-existent.

This blog entry will go through their basic list and demonstrate the quotes that most clearly show Augustine referring to Peter as the "Rock" the church was built upon represent his discarded earlier view. The quotes from later in his life do not clearly demonstrate adherence to the earlier view. Certainly Augustine was a great theologian, but he was not an infallible theologian. I would not be at all surprised if he erred in consistency, went through a transition period, or if extant manuscripts contain errors making his comments fuzzy. When I did go through the basic texts being brought forth, it was clear Augustine shifted his view on Peter and the "Rock."

This is the basic list that will be scrutinized below. There are number of variations on this list as the quotes have journeyed through cyber-space over the years. It appears the cumulative case method of citing various statements from Augustine throughout his life is put forth to downplay Augustine's clear later view.  I contend Rome's defenders therefore are spoof-texting Augustine's writings, hiding the very distinction he refers to in the Retractationes. Let's work through each quote. 

1. “Number the bishops from the see of Peter itself. And in that order of Fathers see who succeeded whom, That is the rock against which the gates of hell do not prevail.”Psalmus contra partem Donati, 18 (A.D. 393),GCC 51

Documentation: "salmus contra partem Donati, 18 (A.D. 393),GCC 51." I suspect this quote may have been taken from Scott Butler's book, Jesus, Peter & the Keys, p. 250 (Butler's entire book is found here). Butler's text reads, 

Butler's documentation would explain what the cryptic "GCC,51" reference means: Dom John Chapman, Bishop Gore and Catholic Claims (London: Longmans, Green, and Co., 1903, 51. Chapman appears to be responsible for this particular English translation.  Other English renditions precede his (simply Google search 19th Century books with the phrase, "Number the Bishops even from the very seat of Peter"). Regardless of the documentation rabbit trails of Rome's defenders, the Latin text is: "Numerate sacerdotes vel ab ipsa Petri sede et in ordine illo patrum quis cui successit, videte: Ipsa est petra, quam non vincunt superbae inferorum portae," (PL 43, 30).

This quote comes from A.D. 393-394. It's from roughly the same time period as the lost treatise Augustine mentions in the Retractationes and strongly appears to be representative of his earlier viewpoint. It's not from a treatise per se, but from a hymn Augustine wrote in response to Donatist hymns being sung, therefore not an actual argument or exegesis, merely a passing lyrical phrase (Augustine also mentions it in The Retractations).  "Augustine of Hippo writes in the Retractations that he composed his Psalmus contra Partem Donati (393) as a retort to the rhymed "psalms" which Donatist congregations chanted, and that he had intended his own Psalm for chanting in his congregation (source). This 19th Century writer presents a lengthy argument suggesting that even with Augustine referring to Peter as the "Rock" in this hymn, it does not equal Rome's version of an transmission of an infallible papal office. 

2. “Let us not listen to those who deny that the Church of God is able to forgive all sins. They are wretched indeed, because they do not recognize in Peter the rock and they refuse to believe that the keys of heaven, lost from their own hands, have been given to the Church.” Christian Combat, 31:33(A.D. 397), in JUR,3:51

Documentation: "Christian Combat, 31:33(A.D. 397), in JUR,3:5." If one begins with the later part of the reference the entire reference becomes clear.  "JUR,3:5" refers to William A. Jurgens, The faith of the Early Fathers vol,3, 51. This text says, 

Jurgens mentions the quote comes from Augustine's "Christian Combat (A.D. 396 and 397)" and the location is "31,33." Jurgens appears entirely responsible for this particular English translation, therefore this is the likely source of this popular cut-and-paste. The Latin text of the quote can be found in De agone christiano (PL 40:307). The Christian Combat can be found in a complete English translation, with the quote found here.  Augustine says,

(33) Let us not heed those who deny that the Church of God can remit all sins. Failing to recognize in Peter the ‘rock,’ these unhappy souls have accordingly lost possession of the keys; they are unwilling to believe that the keys of the kingdom of heaven have been given to the Church. These are the people who condemn as adulteresses widows who marry, and who boast that theirs is a purity superior to the teaching of the Apostles. If they would only acknowledge their own names, they would call themselves ‘wordly’ [mundanos] rather than ‘pure’ [mundos]. For, by their unwillingness to be corrected when they have sinned, they have simply chosen to be condemned with this world [mundo]. 

These heretics do not preserve the spiritual health of those to whom they deny forgiveness of sins. They take away medicine from the infirm, forcing their widows to be consumed by the heat of passion, when they will not permit them to marry. Certainly these heretics are not to be accounted wiser than the Apostle Paul, who preferred that widows should marry, rather than be so consumed by passion. 

"Peter the 'rock'" is merely a passing comment. Based on the year it was penned (A.D. 396 - 397), it's within probability that Augustine is holding his earlier view. Note though that while Peter is the "rock," the keys of the kingdom have been given to the church and he also links his detractors think their teaching is superior to that of the Apostles, not just Peter.  This is clarified though in 30:32, "it is not without reason that, among all the Apostles, it is Peter who represents the Catholic Church. For the keys of the kingdom of heaven were given to this Church when they were given to Peter," and speaking of Peter's denial of Christ: "We see that pardon was granted to Peter, who represents the Church... "

3. “For if the lineal succession of bishops is to be taken into account, with how much more certainty and benefit to the Church do we reckon back till we reach Peter himself, to whom, as bearing in a figure the whole Church, the Lord said: ‘Upon this rock will I build my Church, and the gates of hell shall not prevail against it !’ The successor of Peter was Linus, and his successors in unbroken continuity were these: — Clement, Anacletus, Evaristus, Alexander, Sixtus, Telesphorus, Iginus, Anicetus, Pius, Soter, Eleutherius, Victor, Zephirinus, Calixtus, Urbanus, Pontianus, Antherus, Fabianus, Cornelius, Lucius, Stephanus, Xystus, Dionysius, Felix, Eutychianus, Gaius, Marcellinus, Marcellus, Eusebius, Miltiades, Sylvester, Marcus, Julius, Liberius, Damasus, and Siricius, whose successor is the present Bishop Anastasius. In this order of succession no Donatist bishop is found. But, reversing the natural course of things, the Donatists sent to Rome from Africa an ordained bishop, who, putting himself at the head of a few Africans in the great metropolis, gave some notoriety to the name of ‘mountain men,’ or Cutzupits, by which they were known.”
To Generosus, Epistle 53:2(A.D. 400), in NPNF1,I:298

Documentation:  "To Generosus, Epistle 53:2(A.D. 400), in NPNF1,I:298." "NPNF1" refers to 

A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church,  vol. 1. Here is page 298. The text being cited is from a letter from 400 A.D. Augustine, with the Donatists in view. He refers to Peter as "bearing in a figure the whole church" and referred to as the "Rock," yet though again another passing reference, reflective of his stated earlier view. 

4. “When, therefore, He had said to His disciples, ‘Will ye also go away?” Peter, that Rock, answered with the voice of all, “Lord, to whom shall we go? Thou hast the words of eternal life.’ (Homilies on John, Tract 11:5(A.D. 417), in NPNF1,VII:76.

Documentation: "Homilies on John, Tract 11:5(A.D. 417), in NPNF1,VII:76." This is another reference to  A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church,  volume 7. Here is page 76. The crucial aspect of this citation for Rome's defenders is the year "A.D. 417."  This would be a quote from seventeen years past the previous quote. Unfortunately, Augustine simply mentions Peter being called, "that Rock," with no indication that the building of the church is intended to rest on Peter. The text states, 

If thou be without God, thou wilt be less; if thou be with God, God will not be greater. Not from thee will He be greater, but thou without Him wilt be less. Grow, therefore, in Him; do not withdraw thyself, that He may, as it were, diminish. Thou wilt be renewed if thou come to Him, wilt suffer loss if thou depart from Him. He remains entire when thou comest to Him, remains entire even when thou fallest away. When, therefore, He had said to His disciples, “Will ye also go away?” Peter, that Rock, answered with the voice of all, “Lord, to whom shall we go? Thou hast the words of eternal life.” Pleasantly savored the Lord’s flesh in his mouth. The Lord, however, expounded to them, and said, “It is the Spirit that quickeneth.”

5. “And the Lord, to him to whom a little before He had said, ‘Blessed thou art, and upon this Rock I will build my Church,’ saith, ‘Go back behind, Satan, an offence thou art to Me.’ Why therefore ‘Satan’ is he, that a little before was ‘blessed,’ and a ‘Rock’ ?” In Psalms, 56[55]:14[PL 36, 656] (A.D. 418),in NPNF1,VIII:223

Documentation: "In Psalms, 56[55]:14[PL 36, 656] (A.D. 418),in NPNF1,VIII:223." This is a more complicated reference because someone cross referenced NPNF1 VIII:223 to the Latin text: PL 36, 656 ( "PL" stands for "Patrologia Latina")  The quote begins in column 656 and concludes in 657. It's not at all clear that in this quote from A.D. 418 Augustine is expressing his earlier view. Here is a broader context:

The Lord to His disciples was speaking of His Passion that was to be. Peter shuddered, and saith, “Far be it, O Lord;” he that a little before had said, “Thou art the Christ, Son of the living God,” having confessed God, feared for Him to die, as if but a man. But the Lord who so came that He might suffer (for we could not otherwise be saved unless with His blood we were redeemed), a little before had praised the confession of Peter.…But immediately when the Lord beginneth to speak of His Passion, he feared lest He should perish by death, whereas we ourselves should perish unless He died; and he saith, “Far be it, O Lord,  this thing shall not be done.” And the Lord, to him to whom a little before He had said, “Blessed thou art, and upon this Rock I will build my Church,” saith, “Go back behind, Satan, an offence thou art to Me.” Why therefore “Satan” is he, that a little before was “blessed,” and a “Rock”? “For thou savourest not the things which are of God,” He saith, “but those things which are of man.”  A little before he savoured the things which are of God: because “not flesh and blood hath revealed to thee, but My Father which is in the Heavens.” When in God he was praising his discourse, not Satan but Peter, from petra: but when of himself and out of human infirmity, carnal love of man, which would be for an impediment to his own salvation, and that of the rest, Satan he is called. Why? Because to go before the Lord he willed, and earthly counsel to give to the heavenly Leader. “Far be it, O Lord, this thing shall not be done.” Thou sayest, “Far be it,” and thou sayest, “O Lord:” surely if Lord He is, in power He doeth: if Master He is, He knoweth what He doeth, He knoweth what He teacheth. But thou willest to lead thy Leader, teach thy Master, command thy Lord, choose for God: much thou goest before, go back behind. Did not this too profit these enemies? “Turned be Mine enemies backward;” but let them not remain backward. For this reason let them be turned backward, lest they go before; but so that they follow, not so that they remain.

6. “Peter, who had confessed Him as the Son of God, and in that confession had been called the rock upon which the Church should be built.” In Psalms, 69:4[PL 36, 869] (A.D. 418), in Butler, 251

Documentation: "In Psalms, 69:4[PL 36, 869] (A.D. 418), in Butler, 251." Working backward, "Butler, 251" refers to Scott Butler's book, Jesus, Peter and the Keys, page 251. Butler's book says, 

Also cited is PL 36, 869, which was taken from Allnatt's  citation by Scott Butler. It appears to me that Allnatt is responsible for the English translation being utilized of "Petrus, qui paulo ante eum confessus est Filium Dei, et in illa confessione appellatus est petra, supra quam fabricaretur ecclesia." This spoof-texted version of the quote says it's from "A.D. 418," but Allnat says A.D. 400. Granted, this source point out that the dating Augustine's writing on the expositions of the Psalms "are largely hypothetical." It would be the responsibility of Rome's defenders to explain why they're using a later date when the source the quote was taken from indicates A.D. 400 (therefore another example of Augustine's earlier view).  The Latin text reads, 

Nam quod optatum est modo persecutoribus cogitantibus mala, dixit hoc ipse Dominus Petro. Praecedere quippe quodam loco Petrus voluit Dominum. Loquebatur enim Salvator de passione sua, quam si non suscepisset, nos salvi non essemus; et Petrus qui paulo ante eum confessus erat Filium Dei, et in illa confessione appellatus erat Petra, supra quam fabricaretur Ecclesia, paulo post Domino dicente de futura passione sua, ait: Absit, Domine; propitius esto tibi, non fiet istud. Paulo ante, Beatus es, Simon Bar Iona, quia non tibi revelavit caro et sanguis, sed Pater meus qui in coelis est: modo repente, Redi post me, satana. Quid est, Redi post me? Sequere me. Praecedere me vis, consilium mihi dare vis; melius est ut consilium meum sequaris: hoc est, Redi retro, redi post me. Antecedentem compescit, ut retro redeat; et appellat satanam, quia vult praecedere Dominum. Paulo ante, Beatus: modo, Satanas. Unde paulo ante, Beatus? Quia non tibi, inquit, revelavit caro et sanguis, sed Pater meus qui in coelis est. Unde modo, Satanas? Quia non sapis, inquit, quae Dei sunt, sed quae sunt hominum.

It's interesting to note that NPNF, First series, vol. VIII does not include the sentence being cited by Rome's defenders. Why? I have no idea as to why the  text was edited, and no footnote documents the deletion. It does make sense though why Rome's defenders would only cite the Latin text and Butler'a book. NPNF reads:

For that which had been desired but now for persecutors thinking evil things, the same the Lord Himself said to Peter. Now in a certain place Peter willed to go before the Lord.…A little before, “Blessed art thou, Simon Bar-jona, for flesh and blood hath not revealed it to thee, but My Father which is in Heaven:” now in a moment, “Go back behind Me, Satan.” What is, “Go back behind Me”? Follow Me. Thou willest to go before Me, thou willest to give Me counsel, it is better that thou follow My counsel: this is, “go back,” go back behind Me. He is silencing one outstripping, in order that he may go backward; and He is calling him Satan, because he willeth to go before the Lord. A little before, “blessed;” now, “Satan.” Whence a little before, “blessed”? Because, “to thee,” He saith, “flesh and blood hath not revealed it, but My Father which is in Heaven.” Whence now, “Satan”? Because “thou savourest not,” He saith, “the things which are of God, but the things which are of men.”

While this English translation says:

What he needs is to believe in Christ, and follow him; for what the psalm requests for those who harbor evil intentions is what the Lord himself ordered Peter. There was an occasion when Peter wanted to get ahead of the Lord. Our Savior had been speaking about his passion; if he had not accepted it, we should not have been saved. Just before this Peter had confessed him to be the Son of God, and for that confession he was called the Rock, on which the Church was to be built. But immediately afterward, when the Lord was speaking about his forthcoming passion, Peter protested: Far be it from you, Lord, have some pity for yourself. This will not happen. Only a moment ago Peter had been told, Blessed are you, Simon, son of Jonah, for it is not flesh and blood that revealed this to you, but my Father, who is in heaven; but now, suddenly, he is commanded, Get behind me, Satan (Mt 16:22. 1 7.23). What does get behind me mean? Follow me. You want to rush ahead of me, you want to give me advice. It would be much better for you to follow my advice. This is what "Go back, get behind me" implies. He curbs the man who rushes in front,and makes him take his place in the rear; he calls him Satan because he wants to go one better than the Lord. A minute ago Christ called him blessed; now he addresses him as Satan. Why did he deserve to be called blessed? Because it is notf lesh and blood that revealed this to you, but my Father, who is in heaven, said Jesus. Then why does he now deserve the name Satan? Because you have no taste for the things of God, but only for human things.

7. “And if a Jew asks us why we do that, we sound from the rock, we say, This Peter did, this Paul did: from the midst of the rocks we give our voice. But that rock, Peter himself, that great mountain, when he prayed and saw that vision, was watered from above.” In Psalms, 104[103]:16(A.D. 418), in NPNF1,VIII:513

Documentation: "In Psalms, 104[103]:16(A.D. 418),in NPNF1,VIII:513." NPNF1,VIII:513 can be found here. If this text is actually from A.D. 418, Augustine is not expressing his earlier view. In fact, in the context, Augustine say Christ was the "Rock":  

15. But think not that those “fowls of heaven” follow their own authority; see what the Psalm saith: “From the midst of the rocks they shall give their voice.” Now, if I shall say to you, Believe, for this said Cicero, this said Plato, this said Pythagoras: which of you will not laugh at me? For I shall be a bird that shall send forth my voice not from the rock. What ought each one of you to say to me? what ought he who is thus instructed to say? “If anyone shall have preached unto you a gospel other than that ye have received, let him be anathema.” What dost thou tell me of Plato, and of Cicero, and of Virgil? Thou hast before thee the rocks of the mountains, from the midst of the rocks give me thy voice. Let them be heard, who hear from the rock: let them be heard, because also in those many rocks the One Rock is heard: for “the Rock was Christ.” Let them therefore be willingly heard, giving their voice from the midst of the rocks. Nothing is sweeter than such a voice of birds. They sound, and the rocks resound: they sound; spiritual men discuss: the rocks resound, testimonies of Scripture give answer. Lo! thence the fowls give their voice from the midst of the rocks, for they dwell on the mountains.

16. “Watering the mountains from the higher places” (ver. 13). Now if a Gentile uncircumcised man comes to us, about to believe in Christ, we give him baptism, and do not call him back to those works of the Law. And if a Jew asks us why we do that, we sound from the rock, we say, This Peter did, this Paul did: from the midst of the rocks we give our voice. But that rock, Peter himself, that great mountain, when he prayed and saw that vision, was watered from above.…

What Was Augustine "Retracting" on Peter, The Rock, and Mathew 16?

Did Saint Augustine think that Peter was "the Rock" of Matthew 16:18 the church was founded upon? Towards the end of his life, Augustine looked over the scope of his literary output and put together a critique of his own writings, entitled Retractationes (in English popularly known as "retractions," but better understood as corrections, reconsiderations, revisions). He included an explanation of his view of Matthew 16:18, "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." Basically, Augustine says his earlier view was that the church was founded upon Peter, "the rock" and his later view was that Christ was the rock the church was founded upon. 

While this particular section from the Retractationes  is all over the Internet, I haven't found many instances of carefully working through the context. Protestants generally use the comment to demonstrate Augustine's later view doesn't line up with modern Roman Catholic argumentation about the papacy. Rome's defenders have a few different ways to handle the quote. One way suggests harmonizing Augustine's different positions by saying he was dealing with different issues so emphasized different things. Another way says he ultimately was agonistic on the exact meaning of Matthew 16:18. Another way says as a good Roman Catholic, Augustine maintained his earlier view to stay in harmony with the church. Yet another way simply ignores the details of Augustine's view on Matthew 16:18 and argues for Peter's papal primacy based on other writings from Augustine. 

I think, therefore, there are enough interpretative and historical ambiguities in the statement worth taking a close look at.  Augustine's view in the Retractationes is sort of like a football run in different directions depending on who has the ball. I've noticed polemicists on both sides using this quote without actually taking the nuances into account. I've also come across some weird truncated versions. For instance, this defender of Rome only cites "In my first book against Donatus I mentioned somewhere with reference to the apostle Peter that ‘the Church is founded upon him as upon a rock" and completely leaves out the rest of the statement! On the other end, I came across a non-Roman Catholic webpage that left off the last sentence, "Which of these two interpretations is more likely to be correct, let the reader choose." Highlighting one aspect of the quote or leaving out aspects of it is not a proper way to use Augustine's words. Let him say exactly what he said, not what you want him to say.

Let's first take a look at the statement from the Retractationes. Augustine writes,

[In my first book against Donatus] I mentioned somewhere with reference to the apostle Peter that ‘the Church is founded upon him as upon a rock.’ This meaning is also sung by many lips in the lines of blessed Ambrose, where, speaking of the domestic cock, he says: ‘When it crows, he, the rock of the Church, absolves from sin.’ But I realize that I have since frequently explained the words of our Lord: ‘Thou art Peter and upon this rock I will build my church’, to the effect that they should be understood as referring to him whom Peter confessed when he said: ‘Thou art the Christ, the Son of the living God’, and as meaning that Peter, having been named after this rock, figured the person of the Church, which is built upon this rock and has received the keys of the kingdom of heaven. For what was said to him was not ‘Thou art the rock’, but ‘Thou art Peter’. But the rock was Christ, having confessed whom (even as the whole Church confesses) Simon was named Peter. Which of these two interpretations is more likely to be correct, let the reader choose. [Document 156- Retractationes, Book 1, Chapter 21. A.D. 427. [source]

Latin text: 

Contra Epistulam Donati haeretici, liber unus. In quo dixi in quodam loco de Apostolo Petro quod in illo tamquam in petra fundata sit ecclesia; qui sensus etiam cantatur ore multorum in versibus beatissimi Ambrosii ubi de gallo galli-naceo ait Hoc ipsa petra ecclesiae Canente culpam diluet; sed scio me postea saepissime sic exposuisse quod a Domino dictum est Tu es Petrus...meam, ut super hunc intelligeretur quern confessus est Petrus dicens, Tu es Christus filius Dei vivi; ac sic Petrus ab hac petra appellatus personam ecclesiae figuraret, quae super hanc petram aedificatur, et accepit claves regni caelorum. Non enim dictum est illi Tu es petra, sed Tu es Petrus; petra autem erat Christus quem confessus Simon, sicut eum tota ecclesia confitetur, dictus est Petrus. Harum autem duarum sententiarum, quae sit probabilior, eligat lector. (PL32,618)

Alternate English text:

ONE BOOK AGAINST A LETTER OF THE HERETIC DONATUS (Contra epistulam Donati heretici liber unus) 

(1) In this same period of my priesthood, I also wrote a book against a letter of Donatus who, after Majorinus, was the second bishop of the party of Donatus at Carthage. In this letter, he argues that the baptism of Christ is believed to be only in his communion. It is against this letter that we speak in this book.

In a passage in this book, I said about the Apostle Peter; “On him as on a rock the Church was built.” This idea is also expressed in song by the voice of many in the verses of the most blessed Ambrose where he says about the crowing of the cock: “At its crowing he, this rock of the Church, washed away his guilt.” But I know that very frequently at a later time,3 I so explained what the Lord said: “Thou art Peter, and upon this rock I will build my Church,” that it be understood as built upon Him whom Peter confessed saying: “Thou art the Christ, the Son of the living God,” n and so Peter, called after this rock, represented the person of the Church which is built upon this rock, and has received “the keys of the kingdom of heaven.” For, “Thou art Peter” and not “Thou art the rock” was said to him. But "the rock was Christ,” in confessing whom, as also the whole Church confesses, Simon was called Peter, But let the reader decide which of these two opinions is the more probable. [The Fathers of the Church, a New Translation, vol. 60 (Washington D.C., Catholic University, 1968), Saint Augustine, The Retractations Chapter 20.1 (90-91)].

Another Alternate English text can be found here.

I see 4 basic sections to this statement from Augustine. 1) A recollection of his previous view, 2) A mention of Ambrose's view 3) An accounting of Augustine's later view, 4) A final ambiguous conclusion.  

1. Recollection of Augustine's Previous View

 Augustine first mentions what earlier work of his appears to be under the "revising" knife. In this case, it is his writing "In my first book against Donatus" ("Contra Epistulam Donati haeretici, liber unus"). According to all the historical sources I utilized, they uniformly say this book no longer exists. This is not the only place where Augustine critiques Contra Epistulam Donati haeretici, liber unus. The entry continues and Augustine points out more aspects of this writing that need to be corrected. 

Augustine affirms that his earlier view was that the church was established on Peter, the "Rock."  Augustine saw this earlier interpretation and literary location of it so important he needed readers to be aware of it, and that it was not consistent with his later position.  It's unfortunate this early book is missing. It would be interesting to see the extent of Augustine's comments on the issue and why this particular book was singled out. This source points out this may be the only writing from Augustine "directed against the man who is thought to have given his name to the Donatists" and that several treatises from Augustine are missing against the Donatists. 

Note carefully that Augustine speaks here of "a certain passage" rather than passages. One source using this quote says it may be the only instance of Peter being referred to as the "Rock." Some of Rome's defenders though have located other places in Augustine's writings in which he does equate Peter being the Rock. It appears to me this list of instances originated on this webpage (a cut-and-paste of it can be found here). Let's work through these examples. 

An example from roughly the same time period as the lost treatise comes from another similarly anti-Donatist writing: Psalmus contra partem Donati (393-394).  It's not from a treatise per se, but from a hymn Augustine wrote in response to Donatist hymns being sung, therefore not an actual argument or exegesis, merely a passing lyrical phrase (Augustine also mentions it in The Retractations). Another early passing "Rock" reference is found in De agone christiano (The Christian Combat) (396-397), found here. Again, it is simply a passing inference.  In a letter from 400 Augustine, again with the Donatists in view, refers to Peter as "bearing in a figure the whole church" and referred to as the "Rock," yet though again another passing reference.  In another comment from 400 A.D., "Petrus, qui paulo ante eum confessus est Filium Dei, et in illa confessione appellatus est petra, supra quam fabricaretur ecclesia" (Pl 36,869. cf. Allnatt,  11- 12), similar to the previous, just a passing reference. All of these references appear to testify to Augustine's earlier view discussed in Retractationes. 

Rome's defenders also mention later comments from Augustine equating Peter being the "Rock" the church was founded upon... but these refences aren't so clear.  A comment in Augustine's Homilies on John, Tract 11:5, in NPNF1,VII:76 occurs seventeen years later (417 A.D.), but simply mentions Peter being called, "that Rock," with no indication that the building of the church is intended to rest on Peter. Similarly with Augustine's 418 A.D. comment on Psalm 56 in NPNF1,VIII:223: it's not at all clear that Augustine is expressing his earlier view.  Another "that rock" comment occurs in a 418 A.D. writing (NPNF1,VIII:513), again, not clearly expressing the earlier view.  I think we can safely take Augustine at his word that early on (at least those of 393-400 from the quotes I checked), he did indeed say Peter was the "Rock" the church was founded upon. If he used the word "Rock" later (according to the examples from Rome's defenders that I checked), I see no clear-cut contextual evidence the earlier meaning was intended. Granted Augustine was a great theologian, but he was not an infallible theologian. I would not be at all surprised if he erred in consistency, went through a transition period, or if extant manuscripts contain errors.  

 

2. "Ambrose: When the cock crowed, the rock of the church washes away his guilt"

Augustine mentions Ambrose as regarding Peter as the "Rock" with a similar interpretation to his first book against the Donatists. If you're unfamiliar with the hymn, what Augustine is saying may not make much sense, "When it crows, he, the rock of the Church, absolves from sin." Is it that the "rock of the church," Peter the pope, when crowing, absolves from sin? No, it's a poetic rendering of Peter's denial of Christ (Matthew 26 Mark 14, Luke 22,  John 18).

 This source documents Augustine's mention of Ambrose as, "Ambrose, Hymn I (MPL, XVI, Col. 1409): Exameron V, xxiv, 88 (CSEL, XXXII, p. 201)." "Hymn 1" refers to Aeterne rerum conditor. The hymn does have allusions to Peter as the Rock: "The encouraged sailor’s fears are o’er, The foaming billows rage no more: Lo! E’en the very Church’s Rock, Melts at the crowing of the cock," or in another English translation, "Because of him the sailor gathers strength and the expanse of sea grows mild. when he, the herald, crowed, the Rock himself, the foundation of the Church, washed guilt away by his weeping." The "washed away guilt" is a reference to Peter's denial of Christ and the crowing rooster.  Augustine is attributing the hymn of Ambrose popularizing Peter being the "Rock" the church was founded on, "sung in the mouths of many." 

3. Augustine's Later View

Augustine compares these two meager mentions of Peter being the "Rock" to his "frequent" different interpretation that the "Rock" is Christ, not Peter.  He spends much more time explaining the second view. There's nothing in the sense of a repudiation, but rather a description of his later consistent position. Footnote #3 in the alternate translation utilized above mentions only one instance of Augustine's later view, Sermon 76.1.1. There Augustine states, 

1). The Gospel which has just been read touching the Lord Christ, who walked on the waters of the sea;1 and the Apostle Peter, who as he was walking, tottered through fear, and sinking in distrust, rose again by confession, gives us to understand that the sea is the present world, and the Apostle Peter the type of the One Church. For Peter in the order of Apostles first, and in the love of Christ most forward, answers oftentimes alone for all the rest. Again, when the Lord Jesus Christ asked, whom men said that He was, and when the disciples gave the various opinions of men, and the Lord asked again and said, “But whom say ye that I am?” Peter answered, “Thou art the Christ, the Son of the living God.” One for many gave the answer, Unity in many. Then said the Lord to Him, “Blessed art thou, Simon Barjonas: for flesh and blood hath not revealed it unto thee, but My Father which is in heaven.”2 Then He added, “and I say unto thee.” As if He had said, “Because thou hast said unto Me, ‘Thou art the Christ the Son of the living God;’ I also say unto thee, ‘Thou art Peter.’” For before he was called Simon. Now this name of Peter was given him by the Lord, and that in a figure, that he should signify the Church. For seeing that Christ is the rock (Petra), Peter is the Christian people. For the rock (Petra) is the original name. Therefore Peter is so called3 from the rock; not the rock from Peter; as Christ is not called Christ from the Christian, but the Christian from Christ. “Therefore,” he saith, “Thou art Peter; and upon this Rock” which thou hast confessed, upon this Rock which thou hast acknowledged, saying, “Thou art the Christ, the Son of the living God, will I build My Church;” that is upon Myself, the Son of the living God, “will I build My Church.” I will build thee upon Myself, not Myself upon thee.

Augustine immediately goes on to say in point 2: "For men who wished to be built upon men, said 'I am of Paul; and I of Apollos; and I of Cephas,' who is Peter. But others who did not wish to be built upon Peter, but upon the Rock, said, 'But I am of Christ.'"  A number citations from Augustine could be presented at this point to corroborate Augustine's testimony. Rather than reinvent the wheel, this source and this source present a number of Augustine citations affirming the later view of Augustine (though some of the specific dates are unclear to me in some of the utilized citations).  A profound strength of these later citations is they are not passing references like those used to support the earlier view Rome's defenders bring forth. One thing I could not locate from my cursory search of Augustine's writings is any mentions of Peter and his relation to the word "Rock" after the writing of the Retractationes (427). Augustine died a few years later. 

4. "However, the reader may choose which of these two notions is more plausible"

Augustine concludes, "But let the reader decide which of these two opinions is the more probable." If the Retractationes  from Augustine did not include the last sentence, the entire pericope would be easier to interpret.  Of the Protestant sources I checked, the interpretation is similar: Augustine was correcting his earlier view, maintaining his later view, and finally concludes allowing his readers the choice which one was preferred. This seems to be the easiest and most consistent reading of the text. This source makes pertinent observations:

The fact that [Augustine] would even suggest that individual readers could take a different position is evidence of the fact that after four hundred years of church history there was no official authoritative Church interpretation of this passage as Vatican One has stated. Can the reader imagine a bishop of the Roman Catholic Church today suggesting that it would be appropriate for individuals to use private interpretation and come to their own conclusion as to the proper meaning of the rock of Matthew 16? But that is precisely what Augustine does, although he leaves us in no doubt as to what he, as a leading bishop and theologian of the Church, personally believes.

Granted, I know that sometimes the easiest solution (in this case, interpretation) is not always the correct one. I learned that from my many years of searching out Luther quotes and their interpretive conclusions. I'm willing to hear what Rome's defenders have to say: convince me the easiest reading is not the correct interpretation.  From a cursory search, here's what I found being offered as an alternate explanation.   

 This old source makes the following Roman Catholic leaning observation: 

This is interesting, because it shows that Augustine couldn’t make a decision as to whether Peter or Christ was the rock upon which the church was founded. He had earlier held the former point of view, and Lagrange thinks that the former interpretation would be best, because, as a good Catholic, he follows the interpretation Of the Catholic Church at the Vatican Council, which upheld that view.  

Contemporary Roman Catholic interpretations I cobbled together for this entry tend to present even more complicated explanations.  This other defender of Rome states:  

Augustine was not steadfast in his interpretation of Matthew 16:18. Above, Augustine equated the rock with Peter’s faith, Peter’s successors, and Peter himself. It was during his controversies with the Manicheans, Donatists, and Pelagians that he emphasized the role of Christ and identified “this rock” with Christ. In his dealings with the Manicheans, the nature of God was in the forefront; with the Donatist, it was the nature of the Church and clergy; with the Pelagians, it was the nature of grace and its originator, Jesus Christ. Augustine equated “this rock” with Christ not to downplay Peter’s primacy, rather to emphasize Jesus Christ. Against all these heresies, Augustine stressed that the Church’s foundation and grace rested upon a divine and not a human person. Nevertheless, Augustine remained steadfast in his understanding of Peter’s primacy and the primacy of the Roman See. Augustine did not reject the Petrine interpretation, in favor of which he cites Ambrose’s hymn, but leaves it to the reader to choose. Simon remains a rock, a secondary rock dependent on the Rock-Christ, for Augustine writes, ‘Peter having been named after this rock ‘(Retractations1:21).

Trent Horn of Catholic Answers offers, 

Checking Horn's source, Merry del Val offers yet another layer to Rome's response: "Augustine does allude to what he wrote when he was young, as requires correction: but it is also true that he adds in the same sentence that he does not assume even now that what he is writing will be without blemish. He does not say that he prefers a different translation, but only suggests another." 

Rome's defenders are obviously not unified in their explanations of Augustine's final statement. Their explanations amount to, "I know it looks like this, but it could (or does!) mean that." Of the examples above, the first simply assumes Augustine went along with what the late Vatican council held, the second obfuscates by having Augustine adhere to multiple interpretations, the third claims Augustine simply provided an "alternative of what the words could mean," and the last insinuates that even the older Augustine could be mistaken. That Rome's defenders produce multiple interpretations of the text speak against any of their interpretations. If there was a unified body of an alternative interpretation to the obvious, then I think they could be taken more plausibly. 

Conclusion

I see a few interpretive choices here based solely on the text itself. First, Augustine is negating his earlier view, confirming his later view, and then informing his readers they can choose which one they like. Second, Augustine is explaining his earlier view, explaining its difference with his later view, and then telling his readers he doesn't know which one is correct and they can pick which one they like.

As I read the brief context of this statement, Augustine says his earlier view was that "the Church is founded upon [Peter] as upon a rock," and then expresses his current view. He says of his later view, "But I realize that I have since frequently explained the words..." etc. Note the word, "frequently."  Even in this present context, he spends more time explaining the second view. I've not come across any meaningful documentation that his later view changed or that affirms or corroborates his final view of Matthew 16:18 was either ambiguous or agnostic. In his honest appraisal of his life's work, he was aware of the discontinuity between the two views and suspected (or knew) others saw it as well. Add in the fact that interpreting Matthew 16:18 according to his earlier view was popular during his lifetime, that he contrasted the two views and allowed his readers freedom of interpretation makes sense. 

Augustine: "Among these [apostles] Peter alone almost everywhere deserved to represent the whole Church."

 Recently I came upon this quote from Augustine:

Among these [apostles] Peter alone almost everywhere deserved to represent the whole Church. Because of that representation of the Church, which only he bore, he deserved to hear “I will give to you the keys of the kingdom of heaven” (Sermons 295:2 [A.D. 411]

This quote was the first in a cumulative case meant to establish the historical pedigree of the modern Roman Catholic papacy. Out of curiosity, I did a cursory search to see the quote in context. what I discovered was that it did not establish the historical pedigree of the modern Roman Catholic papacy.

Documentation

The reference provided was "Sermons 295:2 [A.D. 411]." This is a typical Roman Catholic sort of vague reference I'm used to dealing with in regard to Luther quotes. If you search out this reference and English wordage, it becomes apparent it's a popular cut-and-paste.  Here's the exact quote form a 2002 This Rock Magazine. This 1983 book uses the same English wording, minus "[apostles]." This 1957 book uses the quote adding the word the word, "shone": "Among these Peter shone almost everywhere deserved to represent the whole Church..." The author gives the reference, "Sermo 295, 2, 2-4, 4 (PL 38, 1349-50), tr. by Giles, op. cit, doc. 155, p. 176." If this is correct, the person who originally did the English translation was E. Giles, Documents Illustrating Papal Authority found on page 176. Someone, therefore, took this English version of Augustine, placed it online, and it's multiplied ever since. 

The actual complete "Sermon 295" isn't all the hard to track down. Here is a PDF of the entire, The Works of Saint Augustine, A Translation for the 21st Century, Sermons III/8 (273-305A) on the Saints. The sermon can be found beginning on page 197. It's a sermon on "the martyrdoms of the most blessed apostles Peter and Paul." The date "411" isn't set in stone. According to the translation utilized below, it was sometime between 405 - 411.

Context

1. This day has been consecrated for us by the martyrdoms of the most blessed apostles Peter and Paul. It's not some obscure martyrs we are talking about. Their sound has gone out into all the earth, and their words to the ends of the wide world (Ps 19:4). These martyrs had seen what they proclaimed, they pursued justice by confessing the truth, by dying for the truth. The blessed Peter, the first of the apostles, the ardent lover of Christ, who was found worthy to hear, And I say to you, that you are Peter. He himself, you see, had just said, You are the Christ, the Son of the living God. Christ said to him, And I say to you that you are Peter, and upon this rock I will build my Church (Mt 16: 16. 18). Upon this rock I will build the faith which you have just confessed. Upon what you have just said, You are the Christ, the Son oft he living God, I will build my Church; because you are Peter.

Peter, Rocky, from rock, not rock from Rocky. Peter comes from petra, rock, in exactly the same way as Christian comes from Christ. Do you want to know what rock Peter is called after? Listen to Paul: I would not have you ignorant, brothers, the apostle of Christ says; I would not have you ignorant, brothers, that our fathers were all under the cloud, and all passed through the sea, and all were baptized in Moses in the cloud and in the sea, and all ate the same spiritual food, and all drank the same spiritual drink. For they drank from the rock that was following them, and the rock was Christ (1 Cor 10:1-4). There you have where Rocky, Peter, is from.

2. Before his passion the Lord Jesus, as you know, chose those disciples of his, whom he called apostles. Among these it was only Peter who almost everywhere was given the privilege of representing the whole Church.2 It was in the person of the whole Church, which he alone represented, that he was privileged to hear, To you will I give the keys of the kingdom of heaven (Mt 16: 19). After all, it isn't just one man that received these keys, but the Church in its unity. So this is the reason for Peter's acknowledged pre-eminence, that he stood for the Church's universality and unity, when he was told, To you I am entrusting, what has in fact been entrusted to all.

I mean, to show you that it is the Church which has received the keys of the kingdom of heaven, listen to what the Lord says in another place to all his apostles: Receive the Holy Spirit; and straightaway, Whose sins you forgive, they will be forgiven them; whose sins you retain, they will be retained (Jn 20:22-23). This refers to the keys, about which it is said, whatever you loose on earth shall be loosed in heaven, and whatever you bind on earth shall be bound in heaven (Mt 16: 19). But that was said to Peter. To show you that Peter at that time stood for the universal Church, listen to what is said to him,3 what is said to all the faithful, the saints:4 If your brother sins against you, correct him between you and himself alone. If he does not listen to you, bring with you one or two; for it is written, By the mouth of two or three witnesses shall every matter be settled. If he does not even listen to them, refer him to the Church; if he does not even listen to her, let him be to you as a heathen and a tax collector. Amen amen I tell you, that whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven (Mt 18:15-18). It is the dove5 that binds, the dove that looses, the building built upon the rock that binds and looses. 

Let those who are bound fear, those who are loosed fear. Let those who are loosed be afraid of being bound; those who are bound pray to be loosed. Each one is tied up in the threads of his own sins (Prv 5:22). And apart from the Church, nothing is loosed. One four days dead is told, Lazarus, come forth in the open (Jn 1 1:43), and he came forth from the tomb tied hand and foot with bandages. The Lord rouses him, so that the dead man may come forth from the tomb; this means he touches the heart, so that the confession of sin may come out in the open. But that's not enough, he's still bound. So after Lazarus had come out of the tomb, the Lord turned to his disciples, whom he had told, Whatever you bind on earth shall be bound in heaven, and said, Loose him, and let him go (Jn 11:44). He roused him by himself, he loosed him through the disciples.

Notes

2. "Almost everywhere," perhaps, because Augustine would sometimes like to think of John, for example, as representing the Church, not to mention all sorts of other New Testament characters, who were not apostles, like the Canaanite woman, or the woman who suffered from the issue of blood. 

3. He has in mind here Christ's answer to Peter's question which follows immediately on this passage, Mt 18:21. The answer was the parable of the unforgiving servant. 

4. "Faithful" and "saints" are treated as interchangeable terms, on the model of Paul's usage. See, for example, Rom 1:7, 1 Cor 1:2, 2 Cor 1:1, Phil 1:1, etc. 

5. A name for the Church, derived from the Song of Songs, 2:14, etc.

 Conclusion

Frankly, there wasn't anything in the sermon I would necessarily quibble about in regard to Peter. The sermon itself was given to commemorate the martyrdoms of Peter and Paul, so that exuberant comments put forth are not surprising. The specific thing I looked for when I read the sermon was anything explicit from Augustine indicating Peter was "the rock" the church was founded on, that Peter had been given charism of infallibility, that papal succession over the universal church began with Peter, etc. I didn't find any of these concepts in the sermon. Certainly, Augustine notes Peter's preeminence in the Biblical record ("first among the apostles"), but this does substantiate the modern Roman Catholic historical papal claims. Perhaps knee-jerk Protestants think that Peter was just some guy among the myriad of first century Christians, but I do recognize that Peter was a main and important apostle.  That's much different though  than reading an infallible papacy back into the historical record!

Early on in the sermon Augustine says that the "rock" is Peter's confession "you are the Christ, the Son of the living God." and then quoting 1 Cor. 10:1-4 that the "rock" was Christ. Then Augustine does go on to say that Peter represented the whole church, but then says it wasn't just Peter that received the keys, but the that the keys had been entrusted to the whole church. That is, when Peter gets the keys, it's like saying the whole church gets the keys. Then Augustine explicitly connects "keys" "to all the apostles" quoting John 20:22-23. At 295:4, Augustine applies "feed my sheep" of John 21, saying it is the church that is to feed.

 One interesting tidbit is that the English source this quote was taken from goes on to say, "Actually Augustine usually maintained that by the 'rock', in Matt. 16.18, our Lord was referring to himself... I believe the only known instance of his referring the 'rock' to Peter is in the next document." That "next document" states: