The Latin Vulgate and Its Reliance on the Septuagint
When we arrive at the time of Jerome at the outset of the fifth century A.D., it is perfectly clear that the canon for the Christian Church was a settled issue. It included books “of the first order” (those acclaimed canonical) and “other books” from the second order, most of what would be grouped as a separate collection, sometimes called deuterocanonical, meaning books that were considered secondary and not acceptable for establishing the beliefs of the Church – what we equate with “doctrine.” 
Let me cite Jerome’s explanation for what he elected to include and exclude from his Latin translation. First, his methodology was to use the Hebrew version of the Old Testament but consult the Greek Septuagint as he considered the original Alexandrian Septuagint authentic given its apostolic support. Secondly, for the New Testament, undoubtedly, he relied upon various Greek manuscripts gathered and available to him at the time, which possibly included copies of what we know today as Codex Alexandrinus, Codex Vaticanus, and Codex Sinaiticus.
Sharing Jerome’s actual words:
For if we are to pin our faith on the Latin texts, it is for our opponents to tell us which; for there are almost as many forms of texts as there are copies. If, on the other hand, we are to glean the truth from a comparison of many, why not go back to the original Greek and correct the mistakes introduced by inaccurate translators, and the blundering alterations of confident but ignorant critics, and, further, all that has been inserted or changed by copyists more asleep than awake?
I am not discussing the Old Testament, which was turned into Greek by the Seventy elders, and has reached us by a descent of three steps. I do not ask what Aquila and Symmachus think or why Theodotion takes a middle course between the ancients and the moderns.  I am willing to let that be the true translation that had apostolic approval. [Which was the original Septuagint, aka Alexandrian Septuagint or “the Old Greek.”]
I am now speaking of the New Testament. This was undoubtedly composed in Greek, with the exception of the work of Matthew the Apostle, who was the first to commit to writing the Gospel of Christ, and who published his work in Judæa in Hebrew characters [which may not have been the case]. We must confess that as we have it in our language, it is marked by discrepancies, and now that the stream is distributed into different channels, we must go back to the fountainhead. I pass over those manuscripts which are associated with the names of Lucian and Hesychius [labeled heretics by the Church Fathers] , and the authority of which is perversely maintained by a handful of disputatious persons.
It is obvious that these writers could not amend anything in the Old Testament after the labours of the Seventy; and it was useless to correct the New, for versions of Scripture which already exist in the languages of many nations show that their additions are false. I therefore promise in this short Preface the four Gospels only, which are to be taken in the following order, Matthew, Mark, Luke, John, as they have been revised by a comparison of the Greek manuscripts. Only early ones have been used. But to avoid any great divergences from the Latin which we are accustomed to read, I have used my pen with some restraint, and while I have corrected only such passages as seemed to convey a different meaning, I have allowed the rest to remain as they are. [Comments in brackets are mine.]
Jerome’s frank explanation expresses a conviction that the Apostles relied upon the Old Greek Old Testament as it was initially translated during the third and second centuries B.C. And it should not include the Greek translations completed by Aquila, Symmachus, and Theodotion – because they came after the Apostolic era. And most likely, he agreed with Justin Martyr and other Patriarchs who asserted that the rabbinical Bible we know today as the Old Testament (existing in Protestant Bibles) had been corrupted and was not trustworthy in all its parts. However, his Greek manuscripts had likely been made “Hexaplaric,” thanks to Origen. This means that changes made by Aquila, Symmachus, and Theodotion likely worked their way into what became the “standard” Greek Bible used in the Orthodox Church (the Eastern Roman Church) beginning in the sixth century. Thankfully, they did little damage to the Old Greek LXX’s testimony to the authentic Hebrew Bible of Ezra.
What is Canonical, and What Isn’t?
Thus, Jerome decided which books to include in the Latin Bible. He believed the Septuagint should be regarded as authoritative in this regard. While he did not personally translate all of the books in the Septuagint into Latin, others did, completing a Latin Bible that closely mirrored the Greek LXX. Therefore, Jerome’s Vulgate helped, in its own way, to finalize the canon as it recognized what had been established by the various Church leaders such as Athanasius in 367 A.D. in his so-called “Easter Epistle” (see below). But arriving at this point and determining a canon was a progressive process accomplished by an informal consensus of what the Church valued and used. This then was formalized (in my view) by the Patriarchs and the Church after that.
But first, we start with the statements of Jesus in Luke 11:51 and Matthew 23:55, which begins with Genesis and concludes with the words in 2 Chronicles, “from the blood of Abel to the blood of Zechariah.” Our Lord also referenced the three-fold sections of scripture as the “Law of Moses… the Prophets… and the Psalms” in Luke 24:44-45a: “Then he said to them, “These are my words that I spoke to you while I was still with you, that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled.” Then he opened their minds to understand the Scriptures….”
Secondly, the Apostles confirmed that what we know as the New Testament, which was in a formative process, was or would be Holy Scripture. We see Paul referenced Luke’s Gospel as authoritative (1 Timothy 5:18 with Luke 10:7 and Deuteronomy 25:4). “For the Scripture says, “You shall not muzzle an ox when it treads out the grain,” and, “The laborer deserves his wages.” (1 Timothy 5:18) “For the Scripture says, “You shall not muzzle an ox when it treads out the grain,” and, “The laborer deserves his wages.” (Luke 10:7) “You shall not muzzle an ox when it is treading out the grain.” (Deuteronomy 25:4)
Thirdly, the Church Fathers expressed their opinion. Clement of Rome cited eight New Testament books (95 A.D.); Polycarp, John’s disciple, confirmed 15 books (108 A.D.); Ignatius of Antioch identified seven books (115 A.D.); Irenaeus mentioned 21 books (185 A.D.). Likewise, Hippolytus determined there to be 22 books (sometime in the timeframe 170-235 A.D.) In 170 A.D., the first official canon was the Muratorian Canon which included almost all NT books except Hebrews, James, and 3 John. Three Church Councils would confirm the canon: Laodicea (363 A.D., which included the Old Testament, all 27 books of the New Testament plus the Apocrypha); The Council of Hippo (393 A.D.) and that of Carthage (397 A.D.) These confirmed the 27 books of the New Testament to be authoritative for the Church. 
As mentioned above, Athanasius’ “Pascal Festival Letter” of 367 puts a precise point on the topic of the canon. Below are the final four numbered paragraphs of his letter comprising roughly one-half of his position statement. The numbers supplied here begin at 1 rather than 5 to avoid confusing readers. Citing Athanasius:
- There are, then, of the Old Testament, twenty-two books in number; for, as I have heard, it is handed down that this is the number of the letters among the Hebrews; their respective order and names being as follows. The first is Genesis, then Exodus, next Leviticus, after that Numbers, and then Deuteronomy. Following these there is Joshua, the son of Nun, then Judges, then Ruth. And again, after these four books of Kings, the first and second being reckoned as one book, and so likewise the third and fourth as one book. And again, the first and second of the Chronicles are (considered) as one book. Again Ezra, the first and second are similarly one book. After these there is the book of Psalms, then the Proverbs, next Ecclesiastes, and the Song of Songs. Job follows, then the Prophets, the twelve being reckoned as one book. Then Isaiah, one book, then Jeremiah with Baruch, Lamentations, and the epistle, one book; afterwards, Ezekiel and Daniel, each one book. Thus far constitutes the Old Testament.
- Again, it is not tedious to speak of the [books] of the New Testament. These are, the four Gospels, according to Matthew, Mark, Luke, and John. Afterwards, the Acts of the Apostles and Epistles (called Catholic), seven, viz. of James, one; of Peter, two; of John, three; after these, one of Jude. In addition, there are fourteen Epistles of Paul, written in this order. The first, to the Romans; then two to the Corinthians; after these, to the Galatians; next, to the Ephesians; then to the Philippians; then to the Colossians; after these, two to the Thessalonians, and that to the Hebrews; and again, two to Timothy; one to Titus; and lastly, that to Philemon. And besides, the Revelation of John.
- These are fountains of salvation, that they who thirst may be satisfied with the living words they contain. In these alone is proclaimed the doctrine of godliness. Let no man add to these, neither let him take ought from these. For concerning these the Lord put to shame the Sadducees, and said, ‘Ye do err, not knowing the Scriptures.’ And He reproved the Jews, saying, ‘Search the Scriptures, for these are they that testify of Me.’
- But for greater exactness I add this also, writing of necessity; that there are other books besides these not indeed included in the Canon, but appointed by the Fathers to be read by those who newly join us, and who wish for instruction in the word of godliness. The Wisdom of Solomon, and the Wisdom of Sirach, and Esther, and Judith, and Tobit, and that which is called the Teaching of the Apostles (Didache), and the Shepherd (of Hermas). But the former, my brethren, are included in the Canon, the latter being [merely] read; nor is there in any place a mention of apocryphal writings. But they are an invention of heretics, who write them when they choose, bestowing upon them their approbation, and assigning to them a date, that so, using them as ancient writings, they may find occasion to lead astray the simple.
This final paragraph might need some clarification. Athanasius’ mention of the books of what we call the Apocrypha he positively affirms as profitable for reading, “for instruction in the word of godliness.” All those books named by Athanasius fall into this second order of books (including the Didache – the Teaching of the Apostles, and “the Shepherd” – which is the Shepherd of Hermas). His reference to any apocryphal books he identifies as heretical would be other books he did not name. Books like “the Gospel of Thomas,” “the Apocalypse of Peter,” and many others would fall into this category. We will take up texts like 1 Enoch, Jubilees, and Jasher in a future article within a week or two.
One source, compellingtruth.org, provides a helpful and concise recap of the canon issues. Of special note is its statement regarding the four qualities that any book in the New Testament must possess: “First, the author must be an apostle or have a close connection with an apostle. Second, the book must have been accepted by the body of Christ at large. Third, the book had to contain consistency of doctrine and orthodox teaching. Finally, the book had to bear evidence of high moral and spiritual values that would reflect a work of the Holy Spirit as the divine Author.” 
And then, it concludes with a statement on the nature of Scriptural authority with which I concur:
Most importantly, however, it must be recognized that it was God who determined which books belonged in the Bible. God, via the inspiration of the Spirit, imparted to His followers what He had already decided. The human process of collecting the books of the Bible was flawed, but God, in His sovereignty, and despite the limitations of sinful man, brought the early church to the recognition of the books He had inspired, and those books are recognized today as the canon of Scripture.
Table 2 – New Testament References to the Apocrypha
THIS ARTICLE IS DRAWN FROM MY BOOK, A BIOGRAPHY OF THE CHRISTIAN BIBLE