De Unitate Ecclesiae: On the Unity of the Church

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It is an astonishing fact that this treatise by Augustine has never, before now, been fully translated into English. One can find portions of the letter translated in various scholarly works, but the full text has never been translated. It is an important historical work dealing with the nature of the true Church and is therefore an important aspect of his overall work. It is a privilege to be able to present this work to English readers for the first time. The following gives a brief overview of the historical context in which Augustine wrote his letter and the nature of the Donatist controversy, the overall principles that goverened Augustine’s perspective on the church and what he considered constituted true unity and the implications his views have for the Reformation controversy with Roman Catholicism.


To properly understand the treatise it is necessary to understand the historical context in which it was written.

At the beginning of the 4th century there arose a schismatical movement within the Church catholic resulting from the Diocletian persecution which became known as Donatism, derived from one Donatus the Great, a charismatic and influential leader of this separatist movement. For over a century it was a source of intense and hostile division between the churches of North Africa.
During the persecutions, any Christian who renounced Christianity and gave up any scriptures to be burned were spared. Those who refused were usually killed. While some Christian clergy resisted and were martyred, many did not. They renounced Christianity, allowed their books to be burned, and were spared. Those who succumbed to the pressures to escape persecution were called traditores.

Once the persecution subsided with Constantine and the Edict of Milan the issue of what the relationship of the church should be to the traditores came to a head.

Primarily the movement arose from a rigorist perspective toward the issue of restoration of those who lapse in times of persecution, especially as it applies to leadership positions within the church. The Donatists felt that anyone who had succumbed to persecution and denied the faith in any way or had betrayed their brethren should forever be excluded from fellowship within the church. Additionally any bishop who had lapsed had forever forfeited any right to exercise spiritual leadership again and any exercise of such leadership they deemed to be invalid. The Roman Church on the other hand held to a much more forgiving attitude. The Donatists subsequently set up opposing churches and bishops and for years there was bitter rivalry between the two.

The controversy evolved into a debate as to what constitutes a true church and that is the theme of Augustine’s letter. It is an anti-Donatist work, addressed to his fellow bishops, on the nature of the true church and its unity written in response to a pamphlet circulated by a Donatist.

An Overview of the Main Theme of the Letter

At the very beginning of the letter in the Introduction Augustine sets forth his purpose in writing. He states that he wants, in light of the claims of the Donatists to be the only true Church, to adress the question where the true church is to be found. Whether it is the catholic church throughout the world or the Donatist churches located primarily in North Africa. Augustine states that he has three major concerns. The first has to do with how one is able to prove what the nature of the true church is and which party truly represents it. Secondly, he asserts that the scriptures the Donatists employ to support their cause are ambiguous and uncertain and subject to the whims of individual interpreters and are therefore illegitimate in their use by the Dobatists. And then thirdly, he states that he will deal with the false charges and slanders made by the Donatists against the catholic church with respect to the church’s giving up of the scriptures in the time of persecution and of the church’s persecution of the Donatists. The following is his actual statement of Introduction:

The question has been proposed: Is the Church of Christ among the Catholics or among the Donatists? This needs to be determined from specific and clear citations in Holy Scripture. First, evidence is brought forth from the Old Testament and then from the New Testament. By this it is shown that it is clearly and specifically taught that the true Church of Christ is spread throughout the whole world. Then it is shown that few passages from these same canonical Scriptures which are usually brought forth by the schismatics on the Donatist side are both ambiguous and uncertain, and these passages cannot of themselves defend their cause since they can be interpreted with contrary arguments in a different sense. Also, other slanders against the Catholics concerning handing over of  Scriptures and the persecution of the Donatists will be refuted when the occasion arises (Introduction)

Maureen Tilley provides the following synopsis of the Letter:

The main issue in the pamphlet and Augustine’s response was how to identify the true church. His method advocated attention to biblical texts.
The opening and closing of the treatise were addressed directly to Catholics, probably to Augustine’s fellow bishops. The remainder of the work was written as if in dialogue with Donatists. Thus it functioned as a handbook of proofs for discussion over a choice between the Catholic and Donatist parties.
+++Augustine began by characterizing the church as the body of Christ united in love to its head. Then he examined the word “catholic,” …which he interpreted as “spread over the whole earth” He found his proof for the Catholic party in a nexus of biblical verses concerning the spread of the posterity promised to Abraham, especially Luke 24:44. He took his proof texts from the Law, represented by Genesis; the Prophets, represented exclusively by Isaiah (although there are selections later in the es­say from Ezekiel); the Psalms, and the Gospels…
+++To prove his point Augustine read Hebrew Bible texts christologically and ecclesiologically and then joined them to Gospel texts of command to show the fulfillment of the texts in his own church. Signif­icant use of the Bible included the employment of parables of separation. In the face of Donatist sec­tarianism and exclusivism, Augustine emphasized the eschatological timing of separation… Throughout the text he repeatedly returned to the theme of unanimity and mutual forgiveness.
+++This treatise shows how Augustine valued ecclesial unity over purity, a unity whose hallmark was charity (Augustine through the Ages (Grand Rapids: Eerdmans, 1999), Maureen Tilley, Catholicos fratres, Ad; or De unitate ecclesiae, pp. 150-51).

At the very outset he sets forth the foundational principle by which he will address the issues at hand. He says that the question of the nature who represents the true church can only be settled by an appeal to the ultimate authority of the written scriptures and that any appeal to Scripture must be to those which are clear and unambiguous in their meaning. Its is highly significant that Augustine does not make his final appeal to the authority of the catholic church as an institution or the bishop of Rome but to tyhe authority of scripture. This treatise is saturated with an appeal to the authority of scripture from both the Old and New Testaments. He says that the claims of individuals, be they Catholic or Donatist, are nothing more than claims without authority and therefore the case can only be settled by an appeal to scripture to determine which claims are in fact true. As Augustine puts it:

But, as I had begun to say, let us not listen to “you say this, I say that” but let us listen to “the Lord says this.” Certainly, there are the Lord’s books, on whose authority we both agree, to which we concede, and which we serve; there we seek the Church, there we argue our case (Chapter 5).

Since both parties adhere to the truth of Scripture and believe them to be the word of God, it is scripture which should be the final arbiter. And in his appeal to Scripture Augustine establishes certain fundamental truths. He makes his appeal from, as he says, the Law, the Prophets and the Psalms and then primarily to the teaching of Jesus and the book of Acts in the New Testament. The point he makes is twofold with respect to what scripture teaches about the nature of the church. First of all he establishes the fact that the church is prophesied in the Old Testament in the covenant with Abraham and that this prophesied church will spread throughout all the nations of the earth and will not be relegated to one minor geographical area of the world as the Donatists claim. He asserts that he is not giving his own arbitrary interpretation to the Old Testament because the apostle Paul gives the interpretation in the New Testament and therefore this meaning of scripture is clear and unambiguous. Over and over again Augustine proclaims the perspicuity of scripture saying that it does not need to be interpreted either because the meaning is obvious on the bare reading of the text or because the scriptures themselves give their own interpretation. He says to the Donatists:

We read in the Acts of the Apostles that it was said of certain believers that they daily examined the Scriptures to see whether these things were so. Certainly, what are these Scriptures, unless the canonical ones of the law and the prophets? To this are added the Gospels, the apostolic Epistles, the Acts of the Apostles, the Apocalypse of John. Examine all these and bring forth something obvious by which you might show that the Church either remained in Africa alone or would come out of Africa so that what the Lord said might be fulfilled, this good news will be proclaimed throughout the world as a testimony to all the nations; and then the end will come (Mt. 24:14). But bring forth something which doesn’t need an interpreter nor from which it might be demonstrated by you something that was said on another matter and that you dared twist to your own opinion. You see that single thing that you are accustomed to bring forth where you pasture them, where you make them lie down at noon (Cant. 1:6) how when we examine all these words in this passage for a while, it indicates something other than you think, and if it means what you want, the Maximinianists would overcome you in this, for at noon whoever are in the province of Byzacian Tripoli, where they are, more than in Numidia where you are in power.
+++They can so much more faithfully and clearly glory in the noon that you could not exclude them from this interpretation unless you hold the true catholic understanding of these words, showing them that according to the four corners of the world the noon is more from the south than from Africa [i.e. the southwest], but according to the figurative speech of the Scriptures, the perfect illumination of the mind and the greatest fervor of love is called the noon, whence it is written your gloom will be like the noonday (Is. 58:10). Therefore, bring forth something that may not be more truly interpreted against you but that does not need an interpreter, just as this doesn’t need an interpreter in your offspring all nations will be blessed (Gen 22:18), since the offspring of Abraham as Christ is not my interpretation but the Apostle’s; just as this doesn’t need an interpreter you shall be called my delight and your land the whole world (Is. 62:4), since it is spoken to her whom no Christian understands as other than the Church of Christ; just as this doesn’t need an interpreter all the ends of the earth shall remember and turn to the Lord and all the lands of the nations shall worship in his sight for dominion is his and he rules over the nations (Ps. 22:27-28 ) since it is written in this psalm where the passion of the Lord is also revealed by the witness of the Gospel; just as this doesn’t need an interpreter it is fitting that Christ suffer and rise again on the third day and that repentance and the forgiveness of sins be proclaimed in his name to all the nations beginning from Jerusalem (Luke 24:46-47); just as this doesn’t need an interpreter and you will be my witnesses in Jerusalem, in all Judea and Samaria to the ends of the earth (Acts 1:8) for the following history, strengthened by canonical documents testifies that the Church began from Jerusalem and went from there around Judea, Samaria, and the other nations; just as this doesn’t need an interpreter and this good news will be proclaimed as a testimony to all nations and then the end will come (Mt. 24:14), for when he was questioned about the end of this age after he spoke about the beginnings of birthpangs he said the end is not yet (Mt. 24:6), he foretold that the end would be after the preaching of the Gospel in the whole world to all nations; just as this doesn’t need an interpreter, the Lord himself whom no one can contradict interpreted it and expounded it in this parable which he himself told and he said the good seed was the children of the kingdom, the field was the world, and the harvest was the end of the age.
+++Bring forth one such thing by which it might very openly be declared that Africa was either left alone among the remainder or alone was preserved as the beginning of renewing and filling the world. It is not commended by so much evidence that Africa was left alone or from it alone the world was renewed and fulfilled. But if you cannot show what we so justly ask of you, submit to the truth, be silent, go to sleep, and awaken from rage into salvation (Chapter 51).

All throughout this passage Augustine quotes scripture with the preface, ‘this needs no interpreter’, and repeatedly throughout the treatise he emphasizes that the scriptural evidence he marshalls is unambiguous and clear. And his main point, again, is that the Scriptures reveal the church will extend to all nations of the earth and that the Donatists are therefore in conflict with Scripture on this important point.

The second major point Augustine brings out about the nature of the church is that scripture, and in particular, Jesus, teaches that the church is a mixed multitude consisting of both wheat and tares. Jesus teaches that throughout the church age the church will be filled with the righteous and the unrighteousness and Christ Himself will make a separation at the end of the age. And therefore the Donatists have no legitimate reason to separate themselves from the unity of the church in schism because they consider the church to be impure.

Augustine argues that the church is constituted the true church because of its adherence to the Head of the Church. If one were to deny fundamental truths related to the person of Christ he could not be in the Church or saved. Augustine puts it this way:

Christ is both head and body. The head is the only begotten son of God and the body is his Church, bridegroom and bride, two in one flesh. Whoever dissents from Holy Scripture concerning the head is not in the Church, even if he is found in all places in which the Church is designated (Chapter 7).

He points out here that it is the truth of scripture that defines the essential truths related to Christ and if one is in fundamental disagreement with those truths one cannot be in union with the Head and part of His body. And therefore by implication what he is saying is that if any church should depart from the essential truths as revealed in scripture with respect to trhe person of Christ, it would cease to be a true church for it would no longer be united to the Head. And the supremely important point that Augustine makes in this treatise is that the true church and its unity is defined, not by its organization but by its adherence to the essential truths of scripture relative to the person of Christ. And this, of course, is directly related to the truth of the gospel which encompasses the truth of Jesus’ person and work.

It is highly significant that Augustine never appeals to Matthew 16 with application to the bishop of Rome as the foundation to unity or that the church of Rome is the embodiment of the nature of the true church and that to be in communion with that particular church regardless of what it teaches is to be in oneness with Jesus Christ, the Head. He does refer to Matthew 16 but his emphasis is on the truth of a right confession of faith in Christ; that the church is built, not upon a particular bishop but upon Peter’s confession which points to Christ as the rock. He says:

And so although good and bad may give and receive the sacrament of baptism, those reborn spiritually in the body and members of Christ are not built up unless they are good, and certainly that Church is in the good when it is said as a lily among the brambles, so is my love among the maidens (Cant. 2:2). He is among these who build upon the rock, that is, who hear the words of Christ and act, because Peter confesses him to be Christ the Son of God, he thus says and on this rock I will build my Church (Mt. 16:18). It is not therefore among those who build on sand, that is, those who hear the words of Christ and do not act, for he said whoever hears these words of mine and builds upon them I will compare to the wise man who builds his house on rock (Mt. 7:24) and a little later whoever hears these words of mine and does not act on them I will compare to the foolish man who builds his house on sand (Mt. 7:26). Whoever then is incorporated by the bond of love in the building established on the rock and the lily shining among brambles, he certainly will possess the kingdom of God. But whoever builds upon sand or is considered among the brambles, who would have doubted that he will not possess the kingdom of God? (Chapter 60).

The reason Augustine does not emphasize the primacy of the Roman Church and its bishop is because Augustine never taught that the church was built upon Peter’s person and then subsequently upon the bishops of Rome but upon Peter’s confession of faith and therefore upon Christ. Which is to say it is built upon the gospel. In one of his sermons Augustine gives this exegesis of the rock of Matthew 16:

Remember, in this man Peter, the rock. He’s the one, you see, who on being questioned by the Lord about who the disciples said he was, replied, ‘You are the Christ, the Son of the living God.’ On hearing this, Jesus said to him, ‘Blessed are you, Simon Bar Jona, because flesh and blood did not reveal it to you, but my Father who is in heaven. And I tell you’…‘You are Peter, Rocky, and on this rock I shall build my Church, and the gates of the underworld will not conquer her. To you shall I give the keys of the kingdom. Whatever you bind on earth shall also be bound in heaven; whatever you loose on earth shall also be loosed in heaven’ (Mt 16:15–19). In Peter, Rocky, we see our attention drawn to the rock. Now the apostle Paul says about the former people, ‘They drank from the spiritual rock that was following them; but the rock was Christ’ (1 Cor 10:4). So this disciple is called Rocky from the rock, like Christian from Christ.
+++Why have I wanted to make this little introduction? In order to suggest to you that in Peter the Church is to be recognized. Christ, you see, built his Church not on a man but on Peter’s confession. What is Peter’s confession? ‘You are the Christ, the Son of the living God.’ There’s the rock for you, there’s the foundation, there’s where the Church has been built, which the gates of the underworld cannot conquer (John Rotelle, O.S.A., Ed., The Works of Saint Augustine (New Rochelle: New City Press, 1993), Sermons, Volume III/6, Sermon 229P.1, p. 327).

This treatise is of great interest historically because of what Augustine does not say constitutes unity. These words by Johann Joseph Ignaz von Dollinger, the most renowned Roman Catholic historian of the 19th century, who taught church history for 47 years, are very telling:

St. Augustine has written more on the Church, its unity and authority, than all the other Fathers put together. Yet, from all his numerous works, filling ten folios, only one sentence, in one letter, can be quoted, where he says that the principality of the Apostolic Chair has always been in Rome—which could, of course, be said then with equal truth of Antioch, Jerusalem, and Alexandria. Any reader of his Pastoral Letter to the separated Donatists on the Unity of the Church, must find it inexplicable…that in these seventy–five chapters there is not a single word on the necessity of communion with Rome as the centre of unity. He urges all sorts of arguments to show that the Donatists are bound to return to the Church, but of the Papal Chair, as one of them, he says not a word (Janus (Johann Joseph Ignaz von Dollinger), The Pope and the Council (Boston: Roberts, 1869), pp. 70-74).

Augustine’s teachings in this treatise have direct implications for the controversy of the Reformation and the opposition of the Reformers to the Roman Catholic Church. Rome claims to be the one true church and center of unity based on her interpretation of Matthew 16:18-19 and that separation from her constitutes precisely the kind of schism and division for which Augustine condemns the Donatists. But there are significant differences between the two controversies. First of all, in Augustine’s day the church was not Roman Catholic, it was merely Catholic. And secondly, Augustine’s interpretation of Matthew 16 is directly opposed to that of Rome which developed at a later time historically. As Augustine points out, the controversy between the Catholic Church of his day and the Donatists was not over essential truths related to Christ, the Head of the Church, but over the body of Christ. Augustine says:

For this reason, since our question with the Donatists is not concerning the head, but concerning the body, that is, not concerning the savior Jesus Christ himself, but concerning his Church; the head over which we agree shows to us the body over which we disagree so that through his words we might now cease from disagreeing (Chapter 7).

Augustine is saying to the Donatists: We agree on the fundamental truths revealed by the word of God regarding the person of the Head and therefore we must not be divided. Schism in this case is wrong and sinful. But the Reformation controversy is of a different nature from that of the Donatists because that controversy deals directly with the person of the Head and His work. Augustine says, ‘Whoever dissents from Holy Scripture concerning the head is not in the Church’ (Paragraph 7). Augustine gives the example in Paragraph 7 that any one who denies that Jesus is the Son of God, regardless of the claims, is not in the Church. Any supposed “Church” therefore that denies such a fundamental truth is not the Church. The teaching of the Roman Catholic Church as promulgated at the time of the Reformation and codified by the Council of Trent contradicts the Scriptures regarding essential truths related to the Head of the Church, Jesus Christ. It contradicts the biblical gospel and therefore what took place at the Reformation was not schism as Augustine defines it in De Unitate. What took place at the Reformation was a necessary separation due to the perversion of the gospel by the Church of Rome. To remain in communion with that organization would require the embracing of a false gospel which the Paul places under anathema in Galatians 1. And therefore to be in communion with that body would be to place oneself under the anathema of God. As John Calvin makes clear in his Institutes, the reformers were convinced by the word of God that the Roman Catholic Church had ceased to be a true church because of her unfaithfulness to the essential truth of the gospel, which, as Augustine emphasizes in De Unitate, is what defines the nature of the true church and is the ultimate standard for defining the nature of unity:

But if you shout or read aloud from some other place, we do not admit, believe, or receive your voice after we have heard the voice of our shepherd through the mouths of the prophets, through his own voice, and through the mouths of the evangelists so openly declared to us. Those who are my sheep, says the heavenly shepherd, hear my voice and follow me (John 10:27). His voice concerning the Church is not enigmatic. Whoever does not want to wander from his flock, hears it and follows it. His very faithful manager, a teacher of the Gentiles in truth and faith (1 Tim 2:7), because he himself [i.e. Jesus] speaks in him, says, I am astonished that you are so quickly deserting the one who called you in the grace of Christ and are turning to a different gospel, because there is no other; unless some are confusing you and wanting to pervert the Gospel of Christ. But even if we or an angel from heaven should proclaim to you a gospel contrary to what we proclaimed to you, let there be anathema upon him. As we have said before, so now I repeat, if anyone proclaims to you a gospel contrary to what you received, let there be anathema upon him (Gal 1:6-9) (Chapter 32).

The center of unity is truth — the word of God — regarding the person and work of Jesus Christ. It is the gospel. That is the voice of the Shepherd. It is this that the scriptures declare defines the nature of the true church and unity. Augustine’s appeal to the Donatists is based on the ultimate authority of the written scriptures and not the claims of individuals or an organization. His main point is that the true church is defined ultimately by its faithfulness to the word of God:

But, as I had begun to say, let us not listen to “you say this, I say that” but let us listen to “the Lord says this.” Certainly, there are the Lord’s books, on whose authority we both agree, to which we concede, and which we serve; there we seek the Church, there we argue our case (Chapter 5).

I do not wish the holy Church to be founded on human evidence, but on divine oracles (Chapter 6).

All such things then removed, let them demonstrate their Church, if they can, not in the speeches and murmurs of African, not in the councils of their bishops, not in the epistles of whatever debates, not in false signs and prodigies, since we are prepared and cautioned against them by the word of the Lord, but in the precept of the law, in the predictions of the prophets, in the songs of the psalms, in the utterances of the one shepherd himself, in the preaching of the evangelists, that is in all the canonical authority of the holy books, and not such that they might gather and cite things that are spoken obscurely or ambiguously or metaphorically which anyone might interpret according to his own opinion as he wishes. Such things cannot be properly understood and explained unless first those things that are said most openly are held with a strong faith (Chapter 47).