In his book On Christian Doctrine, Augustine gives the following list for the books of the Old Testament canon:
Now the whole canon of Scripture on which we say this judgment is to be exercised, is contained in the following books:—Five books of Moses, that is, Genesis, Exodus, Leviticus, Numbers, Deuteronomy; one book of Joshua the son of Nun; one of Judges; one short book called Ruth, which seems rather to belong to the beginning of Kings; next, four books of Kings, and two of Chronicles—these last not following one another, but running parallel, so to speak, and going over the same ground. The books now mentioned are history, which contains a connected narrative of the times, and follows the order of the events. There are other books which seem to follow no regular order, and are connected neither with the order of the preceding books nor with one another, such as Job, and Tobias, and Esther, and Judith, and the two books of Maccabees, and the two of Ezra, That is, Ezra and Nehemiah which last look more like a sequel to the continuous regular history which terminates with the books of Kings and Chronicles. Next are the Prophets, in which there is one book of the Psalms of David; and three books of Solomon, viz., Proverbs, Song of Songs, and Ecclesiastes. For two books, one called Wisdom and the other Ecclesiasticus, are ascribed to Solomon from a certain resemblance of style, but the most likely opinion is that they were written by Jesus the son of Sirach. Still they are to be reckoned among the prophetical books, since they have attained recognition as being authoritative. The remainder are the books which are strictly called the Prophets: twelve separate books of the prophets which are connected with one another, and having never been disjoined, are reckoned as one book; the names of these prophets are as follows:—Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah, Malachi; then there are the four greater prophets, Isaiah, Jeremiah, Daniel, Ezekiel. The authority of the Old Testamentis contained within the limits of these forty-four books.
All of the books accepted by the Jews are included (Lamentations is often put as part of Jeremiah and 1 and 2 Esdras with Ezra and Nehemiah) along with those not found in the Hebrew Scriptures (Tobias, Judith, 1 and 2 Maccabees, possibly Esdras, Wisdom, and Ecclesiasticus). In contrast, Jerome was the first to refer to these books as “apocryphal” and accepted a canon very close to the Hebrew. This brings us to wonder what Augustine’s reasons for his list might have been.
Interestingly, Augustine differentiates the additional books, Judith excepted, from the others in that no prophet was present to have written them. This is gathered from his City of God when he talks about the prophetic voices that were around before the time of Christ. He ends the prophetic voice at Malachi, Haggai, Zechariah and Ezra and then resumes it on the eve of the nativity, beginning with the father of John the Baptist:
But in that whole time after they returned from Babylon, after Malachi, Haggai, and Zechariah, who then prophesied, and Ezra, they had no prophets down to the time of the Saviour’s advent except…when the nativity of Christ was already close at hand; and when He was already born…But even the reprobate Jews hold Malachi, Haggai, Zechariah, and Ezra as the last received into canonical authority.
This rules out the possibility for a prophetic authorship for his additional books.
At another point, Augustine speaks of the church’s acceptance of Maccabees, not because of prophetic authorship, but on account of the martyrdom of certain Jews before Christ.
From this time, when the temple was rebuilt, down to the time of Aristobulus, the Jews had not kings but princes; and the reckoning of their dates is found, not in the Holy Scriptures which are called canonical, but in others, among which are also the books of the Maccabees. These are held as canonical, not by the Jews, but by the Church, on account of the extreme and wonderful sufferings of certain martyrs, who, before Christ had come in the flesh, contended for the law of God even unto death, and endured most grievous and horrible evils.
On the surface, Jewish martyrdom is a strange canonical criterion. Still, this statement is said in the wider context of Augustine’s understanding of authority. Prophetic authorship was not a determinant in this case, and he did not accept the limited Jewish canon. Clearly, he did not base his decision on a commitment for going back to the source—or perhaps he conceived of going back to a different source: apostolic authority, giving it the ability to recognize significance in inspired works that are not valued for prophetic reasons, but for others such as martyrdom. In this interpretation of Augustine, martyrdom is not a foundational criterion, but apostolic authority is, with martyrdom as simply part of the rational ones with authority have for recognition. With this understood, what is meant when it is said that Augustine uses apostolic authority as foundational? What is apostolic authority?
In a letter to Jerome, Augustine requests Jerome explain why the Hebrew is preferred over the Greek text. He asks this as he appeals to the fact that the apostles use the Greek over the Hebrew, a fact even acknowledged by Jerome who still prefered the Hebrew.
Would you be so kind as to explain what you believe to be the reason why, in many cases, the authority of the Hebrew manuscripts differs from that of the Greek text, known as the Septuagint? For this text is of great importance, seeing that it was so widely diffused and was used by the apostles—a fact which is proved not only by the text itself but which I remember you also confirmed.
This is a significant point. If the apostles themselves used the Septuagint authoritatively, why depend on Jewish sources instead? In a response to Faustus, Augustine further shows us how he understands apostolic authority and its significance.
Will he take our apostles as witnesses? Unless he can find some apostles in life, he must read their writings…Or if he produces his own manuscripts of the apostolic writings, he must also obtain for them the authority of the churches founded by the apostles themselves, by showing that they have been preserved and transmitted with their sanction. It will be difficult for a man to make me believe him on the evidence of writings which derive all their authority from his own word, which I do not believe…The authority of our books, which is confirmed by the agreement of so many nations, supported by a succession of apostles, bishops, and councils, is against you. Your books have no authority, for it is an authority maintained by only a few, and these the worshippers of an untruthful God and Christ. 
Augustine is responding to a claim that Manichaeus was an apostle of Christ. After showing that one only knows of Christ from the Jews and the fulfillment of prophecy, he moves on to apostolic witness as he considers the possibility of a heretical sect producing its own “apostolic writings.” In the previous quote we saw that Augustine thinks apostolic use of the Septuagint is key in deciding its authority. In this response to Faustus we see he believes apostolic authority extends beyond only what they wrote to their witness contained in the churches they founded. This apostolic truth is seen in the form of the church’s agreement supported by apostolic succession, bishops and counsels. This leads us into the other reason Augustine had for accepting the Septuagint, and by extension, additional books. When talking about what method one should use when deciding which books are canonical, he appeals to the church’s usage probably based in it being founded by the apostles and remaining within the line of succession.
Now, in regard to the canonical Scriptures, he must follow the judgment of the greater number of catholic churches; and among these, of course, a high place must be given to such as have been thought worthy to be the seat of an apostle and to receive epistles. Accordingly, among the canonical Scriptures he will judge according to the following standard: to prefer those that are received by all the catholic churches to those which some do not receive. Among those, again, which are not received by all, he will prefer such as have the sanction of the greater number and those of greater authority, to such as are held by the smaller number and those of less authority. If, however, he shall find that some books are held by the greater number of churches, and others by the churches of greater authority (though this is not a very likely thing to happen), I think that in such a case the authority on the two sides is to be looked upon as equal.
Here Augustine is explaining how someone in his time should judge which books should be considered canonical (canon 1). Earlier, he had mentioned an authority based off of agreement, but really there was no clear agreement on which books of the Old Testament were authoritative in a fixed sense yet. This didn’t happen until the council of Trent, which utilized earlier councils Augustine had contributed to. Under the criteria Augustine gives here, the books Jerome accepts would be accepted since those in the Hebrew canon were more or less accepted by the entire church. What about books that were not accepted by the entire church? In that case, one was to defer to those with the greatest authority. Augustine did not conceive of a situation where those with the greater authority were at odds with the majority, but in such a case the two were to be seen as equally valid in making a decision.
Church usage is a problem for Augustine’s view since there wasn’t a clear agreement on which books were canonical and mere church usage of certain books was inconsistent since there was no “agreement between the codices which of the Apocrypha to include.” Different Septuagint copies contained different books. Roger Beckwith points out that even though Origen himself thought the additional books were inspired, as far as the authenticity of the texts went he could only appeal to “the uniform usage of the church, and on the question of the canonicity of the Apocrypha the usage of the church was not uniform. All that was agreed was that the Apocrypha were to be read and esteemed, not that they were to be treated as Scripture.” As an example, the book of Wisdom (one of Augustine’s accepted texts) is put forward. In De Principiis 4.33, Origen is clear that not everyone considers Wisdom authoritative. He makes a claim with the same implicit consequence when it comes to Tobit too. If in Augustine’s day there was no consensus on which books were even read (depending on which Septuagint copy they had) in addition to which were inspired, then appealing to wider church usage and authoritative church usage may not be helpful depending on how widespread the problem was.
One of the biggest reasons Augustine had for accepting the authority of the Septuagint was his dedication to the spurious legend of the seventy. Augustine’s version of the legend says that Ptolemy of Egypt asked the high priest Eleazar to send him the Scriptures and then translators. Seventy(2) translators were sent from the twelve tribes and their Greek translation ended up being called the Septuagint. The more legendary material can be found when he elaborates:
It is reported, indeed, that there was an agreement in their words so wonderful, stupendous, and plainly divine, that when they had sat at this work, each one apart (for so it pleased Ptolemy to test their fidelity), they differed from each other in no word which had the same meaning and force, or, in the order of the words; but, as if the translators had been one, so what all had translated was one, because in very deed the one Spirit had been in them all. And they received so wonderful a gift of God, in order that the authority of these Scriptures might be commended not as human but divine, as indeed it was, for the benefit of the nations who should at some time believe, as we now see them doing.
Earlier it was mentioned that Augustine admitted there were no prophets until the advent of Christ, starting with the father of John the Baptist. Now it is evident he ascribes divine authority to the seventy-two Jewish translators. In the next chapter he even calls them prophetic “For the same Spirit who was in the prophets when they spoke these things was also in the seventy men …so that assuredly they could also say something else, just as if the prophet himself had said both, because it would be the same Spirit who said both”. This appears to be either a blatant contradiction with what was said in book XVII of City of God, or a sudden change of mind. “Basically, the only difference between prophets and translators consists in the fact that the former prophesied earlier.” Then again, it may be more reasonable to qualify Augustine as having the understanding that the Seventy translators had a prophetic interpretative authority so as to distinguish them from those who provided completely new revelation.
Augustine prizes the idea that the translators miraculously came up with the same meaning by divine power—a divine power that could not possibly be in error. When the Jews and Jerome pointed out several errors in the Septuagint, Augustine made appeals to the legend itself by the authority of the church’s reception of it! After all, “no one should be preferred to the authority of so many men”. Jerome is singled out, charitably, as “a man most learned, and skilled in all three languages, who translated these same Scriptures into the Latin speech, not from the Greek, but from the Hebrew” and yet, in the end, it is the legend that is accepted by the church that holds weight with Augustine and not the understanding of a single scholar or the complaints of the Jews. And yet, the legend accepted by Augustine and the church–was just a legend and only true as far as a translation in Greek was probably delivered to Egypt—though not even of any books beyond the first five books of Moses were translated.
Augustine could not get beyond the authority of “so many men” and told Jerome of his unflinching support of the Seventy translators in a letter along with his disbelief in the idea that “so many Latin and Greek authorities” could be wrong. Jerome was not impressed. After revealing his annoyance over Augustine’s misunderstanding about the critical marks in his translation from the Greek (indicating where it diverged from the Hebrew), he attacks Augustine’s appeal to the work of the Seventy by pointing out that Augustine was not even privy to their work untainted and so he could not even know what was truly correct and so was not in a place to discount the work of Hebrew scholars like himself. After all, according to Jerome, if Augustine was consistent and truly devoted to the Septuagint, he would not be reading the Septuagint copy “corrupted by Origen…a Christian, especially when he has removed those additions which came from the edition of a Jew and a blasphemer after Christ’s passion” and further, Augustine should take precautions and “not read what is preceded by an asterisk—in fact [he] should delete such passages from [his] copy” since they would only serve to obscure the authority of the Seventy.
Having already been ever so graciously confronted by Jerome about the differences between the Hebrew and Greek text, Augustine was faced with a dilemma. He could admit there were errors in the Septuagint and turn his back on the legend received by many in the church, or somehow reconcile the differences, some of which seemed to exclude the other in plain meaning. To resolve the difficulty, Augustine chose to believe in a dual inspiration without denying the legend of the Seventy.
…Whatever is found in both editions, that one and the same Spirit willed to say through both, but so as that the former preceded in prophesying, and the latter followed in prophetically interpreting them; because, as the one Spirit of peace was in the former when they spoke true and concordant words, so the selfsame one Spirit hath appeared in the latter, when, without mutual conference they yet interpreted all things as if with one mouth.
This understanding in isolation allows for the Spirit to say something new through the Seventy or enable an interpretation by the translators that went beyond the literal sense contained in the Hebrew. In order to read Augustine’s statement about there being no prophets until the father of John the Baptist and accept his words on the “prophetic” translating power of the Seventy consistently, one would have to understand his statement as referring to the Seventy as having a uniqueinterpretive prophetic authority and not that they were each prophets in their own right delivering new revelation.
Augustine’s resolution presupposes the truthfulness of the legendary account and seeks to explain the discrepancies between the Greek and Hebrew. One could say he seeks to make his pre-established dedication to the Septuagint internally consistent. In the end, “the Bishop of Hippo paid little attention to the historical objections of the scholar from Bethlehem, i.e. that the Seventy translated only the Pentateuch and not all the Scriptures, or that they were only translators and not inspired…”
Augustine’s reasons for accepting additional books to Jerome can be summarized as follows: 1) He bases his understanding in apostolic authority which can be understood through the writings of the apostles as well as the collective understanding and agreement of the church (apostolic succession, bishops, councils and probably an informal, yet evident, majority agreement). Through the writings of the apostles Augustine noticed that they often quoted from the Septuagint authoritatively and so it seemed reasonable that the Septuagint had apostolic sanction and by extension all the additional books contained in it. As far as a collective agreement on canonical lists is concerned, there was none and so he devised a practical way an individual in his time could decide which books to ascribe authority to. The inquisitor ought to accept the books that are considered authoritative by the most number of churches and those church’s with the most authority (perhaps referring to their antiquity). 2) He believed the legend of the Seventy translators was true, and that they were uniquely inspired by the Holy Spirit when it came to interpretation. Since this was the case, differences between the Hebrew and Greek were explained as the Holy Spirit further interpreting what the prophets of long ago were inspired to say in their time. He could easily accept additional books to the Hebrew as inspired by them since he also did not accept Jerome’s understanding that not all the books were translated. Finally, 3) Augustine could not comprehend the thought that so many learned authorities used within the church including the Seventy themselves could all be mistaken and that one man, Jerome and the Jews could be right.
 Augustine. “Christian Doctrine.” Edited by Philip Schaff. In A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church Series 1 Vol. II (Grand Rapids, MI: Eerdmans, 1993), 2.8.13.
 Augustine. “City of God.” Edited by Philip Schaff. In A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church Series I Vol. II (Grand Rapids, MI: Eerdmans, 1993), 17.24.
 Ibid.,18. 36.
 Augustine. “Ep.71” Edited by Caroline White. In The Correspondance (394-419) Between Jerome and Augustine of Hippo (Lewiston, NY: Edwin Mellen Press, 1990), 93.
 Augustine. “Reply to Faustus the Manichaean.” Edited by Philip Schaff. In A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church Series IVol. IV (Grand Rapids, MI: Eerdmans, 1993), 13.4-5.
 Augustine, Christian Doctrine, 2.8.12-13.
 Roger Beckwith, The Old Testament Canon of the New Testament Church: and its Background in Early Judaism (Oregon: Wipf and Stock Pub, 1985), 383.
 Ibid., 394.
 Augustine, City of God, 16.42.
Martin Hengel, The Septuagint As Christian Scripture: Its Prehistory and the Problem of its Canon (Grand Rapids, MI: Baker Academic, 2002), 53.
 Augustine, City of God, 16.43.
 Augustine, Ep.71, Edited by Caroline White, 92.
 Jerome, Ep.112, Edited by Caroline White, 133-134.
 Augustine, City of God, 16.43.
 Hengel, 52.