To appreciate this question and its answer, one must first remember that almighty God never handed anyone a complete Bible and said, “Here it is.” Rather, over the centuries of salvation history, the Holy Spirit inspired the authors of Sacred Scripture to write down God’s revelation to us. As time went on, the Church compiled these books to form a Canon– an authoritative set of Sacred Scripture– and declared it “God’s Word.”
The books of the Old Testament were written probably between 1000 and 100 BC, and are usually distinguished as three sets: The Law (or Torah, our first five books of the Old Testament), the Prophets, and the Writings. Even in the New Testament itself, we find references to the reading of the Law and the Prophets in synagogue services (e.g. Luke 4:16-19, Acts 13:15). After the Fall of Jerusalem in AD 70, the Jewish rabbis convened the Council of Jamnia (90-100), at which time they established what books would be considered their Sacred Scripture. At this time, some controversy still existed over what are called the seven “deuterocanonical books”– Tobit, Judith, Wisdom, Sirach, Baruch, I & II Maccabees, and Esther– although they had been incorporated in their entirety or at least partially in versions of the Septuagint, the official Greek translation of the Old Testament by the year 100 BC. Part of the reason for the controversy was because these were the latest writings of the Old Testament and were written in Greek rather than Hebrew; the other books of the Old Testament– the “protocanonical books”– were older and originally written in Hebrew. Modern scholars note that Jamnia did not exclude any books definitively; a rigid fixing of the Jewish canon does not occur until at least 100 years later, and even then other books– including the deuterocanonical books– were read and honored. Many Scripture scholars, however, have no doubt that the apostolic Church accepted the deuterocanonical books as part of its canon of Sacred Scriptures. For instance, Origen (d. 245) affirmed the use of these books among Christians even though some of the Jewish leaders did not officially accept them.
Meanwhile, the writing of the New Testament books occurred between the time of our Lord’s death and the end of the first century. (Recent studies of the Dead Sea Scrolls by some scholars suggest a date of the earliest writings closer to the time of our Lord’s death, whereas much scholarship seems to place the writings between AD 50 and 100). After the legalization of Christianity in 313, we find the Church striving to formalize what writings of the New Testament were truly considered inspired and authentic to the teachings of our Lord. St. Athanasius in his Paschal Epistle (367) presented the complete list of 27 books of the New Testament saying, “These are the sources of salvation, for the thirsty may drink deeply of the words to be found here. In these alone is the doctrine of piety recorded. Let no one add to them or take anything away from them.” This list of 27 books along with the 46 books of the Old Testament (including the deuterocanonical ones) was affirmed as the official canon of Sacred Scripture for the Catholic Church by the synods of Hippo (393), and Carthage I & II (397 and 419). The letter of Pope St. Innocent I in 405 also officially listed these books.
Although some discussion arose over the inclusion of other books into the Church’s canon of Sacred Scripture after this time, the Council of Florence (1442) definitively established the official list of 46 books of the Old Testament and 27 of the New Testament.
With this background, we can now address why the Protestant versions of the Bible have less books than the Catholic versions. In 1534, Martin Luther translated the Bible into German. He grouped the seven deuterocanonical books of the Old Testament under the title “Apocrypha,” declaring, “These are books which are not held equal to the Sacred Scriptures and yet are useful and good for reading.” Luther also categorized the New Testament books: those of God’s work of salvation (John, Romans, Galatians, Ephesians, I Peter, and I John); other canonical books (Matthew, Mark, Luke, Acts, the rest of Pauline epistles, II Peter, and II & III John); and non-canonical books (Hebrews, James, Jude, Revelation, and the seven books of the Old Testament). Many Church historians speculate that Luther was prepared to drop what he called the “non-canonical books” of the New Testament but refrained from doing so because of possible political fall-out. Why Luther took this course of action is hard to say. Some scholars believe Luther wanted to return to the “primitive faith,” and therefore accepted only those Old Testament books written in Hebrew originally; others speculate he wanted to remove anything which disagreed with his own theology. Nevertheless, his action had the permanent consequence of omitting the seven deuterocanonical books of the Old Testament in Protestant versions of the Bible.
The Thirty-nine Articles of Religion (1563) of the Church of England asserted that these deuterocanonical books may be read for “example of life and instruction of manners,” although they should not be used “to establish any doctrine” (Article VI). Consequently, the King James Bible (1611) printed the books between the New Testament and Old Testaments. John Lightfoot (1643) criticized this arrangement because he thought the “wretched Apocrypha” may be seen as a bridge between the two. The Westminster Confession (1647) decreed that these books, “not being of divine inspiration, are no part of the canon of Scripture, and therefore are of no authority of the Church of God; nor to be in any otherwise approved, or made use of than other human writings.” The British and Foreign Bible Society decided in 1827 to remove these books from further publications and labeled these books “apocryphal.” However, many Protestant versions of the Bible today will state, “King James version with Apocrypha.”
The Council of Trent, reacting to the Protestant Reformers, repeated the canon of Florence in the Decree on Sacred Books and on Traditions to be Received (1546) and decreed that these books were to be treated “with equal devotion and reverence.” The Catechism repeats this same list of books and again affirms the apostolic Tradition of the canon of Sacred Scripture.