How Did the Catholic Church Determine Which Books Belong in the Bible?

Brief Overview

• The Catholic Church used three main tests to decide which writings should be included in the Bible, known as apostolicity, orthodoxy, and universality.
• Apostolicity refers to whether a book was written by an apostle or a close associate of the apostles who lived in the early Church.
• Orthodoxy means that a book’s teachings had to agree with the correct understanding of Christian faith that the Church had received from the apostles.
• Universality required that a book be accepted and used by many Christian communities across different regions, not just in one local church.
• The Church followed this careful process because believers needed to know which writings contained the true message of Jesus and the apostles.
• Different parts of the Bible were accepted at different times, with the New Testament being finalized at the Council of Trent in 1546.

How the Early Church Developed the Canon

The early Church faced a real problem in the first few centuries after Jesus rose from the dead. Christians in different places received various writings and letters, some genuine and some not. The apostles and their closest followers had taught the faith by word of mouth and through letters to specific communities. As time passed and the apostles died, Church leaders needed to decide which written works were truly from the apostles or their inner circle and which were later inventions or false teachings. This process was not quick or simple. It took centuries for the Church to fully work through all the texts and reach agreement on a complete list. The Church did not invent this process out of nowhere. Instead, Church leaders looked for signs that God had guided certain writings to be preserved and widely accepted among believers. They prayed for wisdom and used their knowledge of what the apostles had actually taught. The challenge was that anyone could claim to speak for the apostles, so the Church needed clear standards.

The role of councils and important bishops proved crucial in this work. From the earliest times, different local churches would gather and share information about which books they had been using and trusting. Letters would pass between churches in Rome, Alexandria, Antioch, and other major cities. Leaders like Athanasius of Alexandria wrote lists of what they considered the true scriptures. These leaders did not act alone. They consulted with other bishops and with the tradition passed down through the Church. They also paid attention to what ordinary Christians in their care had been reading and learning from. The process showed that the question of the canon was important to everyone. Bishops took this seriously because they understood that false writings could lead people away from true Christian faith. The Church could not function well if some communities used different scriptures than others.

The Test of Apostolicity

Apostolicity was the first and most important criterion the Church used when deciding if a book belonged in the Bible. This test asked a simple question: did an apostle write this book, or did someone very close to an apostle write it? The apostles were the twelve men Jesus chose and trained personally, along with Paul and a few others Jesus appeared to after the resurrection. These men had lived with Jesus, heard his teaching, and received direct instructions from him. What they wrote or what their close associates wrote carried special weight. Books that came directly from an apostle had the strongest claim to be included. The Gospel of Matthew, for example, was considered apostolic because Matthew himself was one of the twelve. The Gospel of Mark had a good claim because Mark was closely associated with Peter, one of the main apostles. Books written by someone who knew the apostles personally, like Luke who was associated with Paul, also qualified.

However, apostolicity did not mean the author had to be famous or well-known. Some apostles wrote very little. Peter left behind his letters, but we know less about what he wrote than what Paul wrote. The test was not about how much was written but about whether the author had real authority from being with Jesus or sent by Jesus. The Church was careful not to accept books simply because they claimed to be by an apostle. Many false writings appeared later claiming to be from Peter, Paul, or other apostles. These were called apocryphal texts. The Church had to use good judgment to figure out which claims of apostolic authorship were true and which were fake. Church leaders studied the writing style, the historical details, and compared the teachings with what they knew the apostles actually believed. They also checked if there was any early evidence that a particular book had been used and trusted by the earliest Christians.

The test of apostolicity also worked backwards in a way. If a book had been used for a long time by many churches and was known to be of ancient origin, this suggested it probably had apostolic roots. By contrast, if a book suddenly appeared late and had no long history of being used, the Church was right to be suspicious. The apostles could have taught more than what made it into the written scriptures. The Church recognized that apostolic tradition, meaning teachings passed down by word of mouth from the apostles, was also important. Yet the written texts that the Church accepted as scripture held a special place. These texts were seen as the fullest and most reliable record of apostolic teaching. The test of apostolicity therefore served as the Church’s way of staying connected to Jesus through the apostles who walked with him.

The Test of Orthodoxy

The second test used by the Church was orthodoxy, which simply means right teaching or true doctrine. A book could claim to be written by an apostle, but if what it taught was wrong, the Church would reject it. This test protected Christians from being misled. The Church had a clear sense, from the apostles’ own teaching, of what Christian faith actually meant. Jesus taught about God the Father, about salvation through his death and resurrection, about the Holy Spirit, and about how Christians should live. The apostles passed on this core message. Books that taught something different from this core message could not be part of the Bible, even if someone claimed an apostle wrote them.

Many false gospels and other writings appeared in the early centuries. Some taught that matter was evil and the physical body was a prison from which the soul needed to escape. Others denied that Jesus was truly God or truly human. Others claimed that the God of the Old Testament was evil and different from the God that Jesus taught about. These ideas, called heresies, spread in some places and confused Christians. The Church used the test of orthodoxy to keep these false ideas out of the official scriptures. When bishops and councils looked at a book to decide if it should be in the canon, they asked: Does this book teach what we know to be true from the apostles? Does it agree with what the whole Church believes? Is there anything in it that goes against the core message of Christianity that we have received? If the answer was no, the book was rejected.

The connection between apostolicity and orthodoxy was very close. A truly apostolic book, one actually written by an apostle or someone taught directly by an apostle, would naturally teach orthodox doctrine. Conversely, a book that taught false doctrine probably was not genuinely apostolic, even if it claimed to be. The two tests worked together. The Church also understood that the Holy Spirit had guided the process of preserving and recognizing true scripture. God had not abandoned his people by leaving them with only false or misleading writings. Through prayer and careful study, the Church could recognize which books came from God. The test of orthodoxy was not arbitrary. The Church could point to the teaching of the apostles as found in genuinely apostolic writings, in the Creed that Christians recited, and in the consistent teaching of bishops going back to the earliest times. When a new writing was tested against this standard, the Church could make a real judgment about whether it fit.

The Test of Universality

The third test was universality, which meant that a book should be accepted and used by Christian communities across a wide area, not just in one place. If a book was truly from an apostle or apostolic times, it would naturally spread and be valued by many churches. Conversely, if only one small group of people used a book, this raised questions about whether it really had apostolic authority. The Church relied on the judgment of the whole people of God spread across the Mediterranean and beyond. When the gospel of Matthew was used and trusted from Egypt to Gaul to Asia, this showed something real about its authority. When bishops in Rome, Alexandria, Antioch, and Jerusalem all recognized a book as genuine, this carried weight. The test of universality meant the Church did not let one person or one region decide the canon by themselves.

In practice, universality meant that a book had to have a long history of being recognized as scripture by multiple churches. The Church could see which books had been in use since the very earliest times. Some books had clear evidence of being used in the second or third century in many different places. Others appeared in only one region or seemed to come from a later time. The most accepted books had the strongest claim to be canonical. The Church also understood that some areas might take longer to receive and recognize all the books. A letter that Paul sent to one particular church might take time to reach other areas. But eventually, if it was truly apostolic and true in its teaching, it would spread and be recognized. The test of universality worked hand in hand with the tests of apostolicity and orthodoxy. A book that really came from an apostle and taught true doctrine would eventually be known and accepted everywhere Christians gathered.

The practical working out of universality was sometimes slow. Different regions had slightly different lists of accepted books for a time. Some churches in the East were slower to accept the book of Revelation than others. Some churches in the West questioned whether Hebrews was truly by Paul. These differences did not mean the Church was confused. It simply meant that the communication and confirmation of books took time. As time went on and as Church leaders met together at councils, they worked out these minor differences. By the time of major councils, the Church was able to affirm a unified list. The test of universality also protected the canon from being controlled by any one person or political power. No single bishop or emperor could impose a list of books on the whole Church and make it stick if other churches did not agree. The consent of many churches across many lands was needed.

How These Three Tests Worked Together

The three tests of apostolicity, orthodoxy, and universality did not work in isolation from each other. They worked as a unified system that helped the Church make wise decisions. A book might pass one test and fail another, which would raise questions. If a book claimed to be apostolic but taught false doctrine, it failed on orthodoxy. If a book taught correct doctrine but had no real evidence of being apostolic or widely used, questions would remain about its place. The strongest candidates for inclusion in the canon were books that scored well on all three tests. These books had clear apostolic roots, taught the true faith, and were recognized and used by Christians across the whole world.

The Church also understood that these tests worked backwards as well as forwards. If a book had been recognized and used for a very long time by the whole Church and was deeply woven into Christian life and worship, this was powerful evidence that all three tests had been met. The Church did not need to find every piece of historical evidence if the accumulated judgment of Christians over centuries pointed in one direction. The New Testament books were so clearly embedded in the life of the Church that their authenticity seemed obvious. They were read in worship, they were cited by early Church Fathers, they shaped Christian teaching and practice. This universal recognition and use was itself evidence that these books came from the apostles and taught true doctrine. Conversely, books that had never been widely accepted despite the Church’s knowledge of them never became part of the canon because they failed the test of universality.

The Canon of Scripture in the Old Testament and New Testament

The Catholic Church holds both the Old Testament and the New Testament as scripture, but the process for accepting them was different in some ways. The Old Testament, also called the Hebrew Bible or Jewish scriptures, had already been largely settled before the Church existed. Jesus and the apostles used the scriptures that Jewish people recognized as authoritative. The Church therefore received a list of biblical books from Judaism, though different Jewish communities sometimes disagreed about a few of the books. The Catholic Church ultimately accepted all the books in the Septuagint, which was a Greek translation of Jewish scriptures made before the time of Jesus. This included some books that the Hebrew Bible did not include, like Tobit, Judith, Wisdom, and Sirach. The reason the Church valued the Septuagint was partly because that was the translation Jesus and the apostles most often quoted from, at least in their recorded teachings.

The New Testament canon was more directly the work of the Church itself. These were new writings that came from the apostles and their generation. The Church had to decide which ones to include. The Gospels were clearly important because they told the story of Jesus. The letters of Paul were clearly important because Paul was an apostle sent by Jesus. The question was which gospels were genuine, which letters were truly by Paul, and whether other writings deserved to be included. Early Church fathers like Athanasius, Jerome, and Augustine wrote about which books they considered canonical. They did not all agree at first. Some councils addressed parts of the question. The Third Council of Carthage in 397 listed what it considered the complete New Testament. This list was confirmed at a later council in Rome. The Council of Trent in 1546 formally affirmed the complete Catholic canon of scripture, both Old Testament and New Testament (CCC 120). This was the Church’s definitive statement on which books belong in the Bible.

The Role of Church Leaders and Councils

Church leaders played a central role in the process of deciding the canon. Bishops in major cities, whose churches could trace their leadership back to the apostles themselves, had special authority. The bishop of Rome, the Pope, held a place of honor among these leaders. His judgment mattered because Rome was the city where Peter and Paul both ministered and died. Other important bishops in Alexandria, Antioch, and Jerusalem also had great influence. These leaders studied the ancient writings and consulted with each other about which ones were truly apostolic. They also listened to what was happening in the churches under their care. What were the people reading? What had been handed down as authoritative? The judgment of regular Christians also mattered, because if a book was truly apostolic and true in its teaching, ordinary believers would recognize it as such.

Councils brought bishops together to make official judgments that represented the whole Church. The earlier councils mainly addressed questions of doctrine and discipline, not the canon. The Council of Nicaea in 325 focused mainly on defending the truth that Jesus was God. But as time went on, councils began to address which books should be officially recognized as scripture. The Church understood that the Holy Spirit guided these councils. When bishops gathered in prayer and dialogue to discern the truth, they believed the Holy Spirit helped them reach the right conclusion. This did not mean the bishops had magical knowledge. It meant that God worked through their sincere effort to understand and preserve what the apostles had handed down. The councils did not create the canon so much as they officially recognized and confirmed what the Church had already come to believe over a long period of time.

The role of the Church Fathers was also important in this process. These were leading teachers and bishops from the early centuries of Christianity. Men like Ignatius of Antioch, Justin Martyr, Irenaeus of Lyon, Tertullian, Athanasius, Jerome, and Augustine all wrote about which writings they considered scriptural. By studying what these Fathers said, later Church leaders could see which books had been widely recognized as authoritative in the early Church. The Fathers would quote from the gospels and letters as if everyone already knew these were true scripture. This meant these books had already been accepted long before any formal council met to declare it officially. The Fathers also warned against false gospels and false letters attributed to the apostles. They explained why certain writings were not authentic. Their careful work helped the Church avoid being deceived by counterfeits.

False Gospels and Writings That Were Rejected

The Church had to reject many writings that claimed to be apostolic but were not genuine. Some of these false writings appeared very early. The Gospels of Thomas, Peter, and Judas claimed to be written by apostles, but they taught false ideas that went against what the real apostles had taught. These texts often contained teachings influenced by Greek philosophy and false ideas about the physical world and matter. The Gospel of Thomas, for example, taught sayings of Jesus but interpreted them in ways that did not match the teaching of Matthew, Mark, Luke, and John. The so-called Epistle of Barnabas claimed to be from Barnabas, who was a companion of Paul, but scholars found good reasons to think it was written much later by someone else. Many churches considered it scripture for a time, but eventually it was recognized as not truly apostolic.

Other false writings came from heretical groups that wanted to use the authority of apostolic names to spread their false ideas. The Gnostics created many writings, including false gospels and acts of apostles, to support their belief that the physical world was evil and created by a false god. The Marcionites, who denied that the God of the Old Testament was the same as the God Jesus taught about, created their own list of books to support their false teaching. The Church carefully examined these writings and found that they did not match what the apostles had actually taught. They were either too late to be apostolic, or they taught false doctrine, or they had never been recognized by many churches as true scripture. The test of universality was especially useful here. If a book claimed to be apostolic but was only known in one place or one group, this was a red flag. True apostolic writings would have spread and been recognized widely.

The Church also rejected some writings that may have been genuine in the sense that they came from early Christian times but were not seen as having apostolic authority. The Didache, sometimes called the Teaching of the Twelve Apostles, contained useful moral instruction for Christian communities, but it was not written by the apostles themselves. Some churches used it and valued it, but it was never universally accepted as part of scripture. Similar books like the Shepherd of Hermas and the First Letter of Clement were respected as useful guidance but not seen as scripture. They did not pass the tests of apostolicity and universality well enough to be included in the canon. The Church understood the difference between writings that were useful and edifying and writings that were truly apostolic scripture. Both could be helpful to Christians, but only the latter belonged in the Bible.

The Completeness of the Canon and God’s Guidance

The Catholic Church teaches that the canon is closed, meaning no new books should be added to it. The process of recognizing the canon took place over centuries, from the first century to the sixth century, with the most formal declaration coming at the Council of Trent in 1546. Once the Church made this declaration, the work was complete. The Bible contains exactly the books that God intended for the Church to have as scripture. The Catechism teaches that through the Church’s recognition of scripture, we receive the Word of God written down (CCC 105). This means that the process of deciding the canon was itself guided by God. He worked through the Church to ensure that the true apostolic writings were preserved and recognized, while false writings were set aside.

The claim that the canon is closed does not mean the Church was wrong about what it included. Rather, it means that the process of discernment is complete. The Church is confident that the sixty-six books of the New Testament and the books of the Old Testament as listed are the true scriptures. These are the books that contain the apostolic teaching. These are the books that the Church has used for worship, prayer, and instruction for many centuries. These are the books that shaped Christian doctrine and practice. If the Church had failed to recognize some true apostolic writing or had included a false one, this would undermine the whole process and the whole Church. The confidence of the Church in the canon rests on the belief that God protected the Church from such mistakes. The three tests of apostolicity, orthodoxy, and universality worked in the Church’s life to separate the true from the false.

The Significance of the Canon for Catholic Faith

Understanding how the Catholic Church determined the canon matters for how Catholics read the Bible today. When Catholics open the Bible, they can trust that what they are reading comes from the apostles and teaches true doctrine. This trust does not come from nowhere. It is based on centuries of careful work by bishops and scholars who tested writings against clear standards. The canon is not arbitrary or political, though some people outside the Church have claimed this. The Church chose according to objective standards, and these standards made sense. A book had to come from the apostles or their close associates to have ultimate religious authority. A book had to teach true Christian doctrine to be faithful to Jesus. A book had to be recognized and used by many churches to prove its real apostolic authority.

The canon shapes how Catholics understand Jesus and salvation. The four gospels give us the most complete picture of who Jesus was and what he taught. The letters of Paul explain how the apostles understood Jesus’s death and resurrection. The book of Revelation gives hope about God’s final victory. Together, the sixty-six books of the New Testament and the books of the Old Testament as the Church accepts them form a unified library that witnesses to God’s plan for salvation from beginning to end. Catholics cannot pick and choose which parts of the Bible they like and reject the rest. The canon tells us which writings have apostolic authority. When the Church says a book belongs in the canon, this is a statement that its teachings matter for Christian faith and life. The canon is not just a list of books. It is the Church’s way of saying, “These are the books that shaped us, that tell our story, that guide us to Jesus.”

How Catholics Use Scripture

The fact that the Church went through a careful process to establish the canon affects how Catholics approach the Bible in their own lives. The Bible is not just a collection of helpful advice or inspirational stories. It is the Word of God written in human words. The Church accepts all the books of the canon as equally authentic scripture, even though they were written at different times and in different styles. The gospels, the letters, the history books, the wisdom literature, and the prophets all have authority as God’s Word. When Catholics read scripture, they read it as part of the Church’s tradition. They do not read it in isolation or try to interpret it any way they like. The Church teaches that scripture must be interpreted with attention to its human authors, its historical context, and the full teaching of the Church (CCC 109). The canon was established by the Church, and the Church remains the proper interpreter of scripture.

Catholics also understand that not everything the Bible says applies to everyone in the same way today. Some laws in the Old Testament were specific to the ancient people of Israel. Some instructions in the New Testament were meant for specific communities facing specific problems. Yet all of scripture contains God’s Word and has something to teach believers. The canon includes books that sometimes seem to teach different things. Does salvation come through faith or through works? The book of James and the letter of Paul seem to have different emphases on this point. But the Church teaches that there is no real contradiction because both faith and works matter for salvation. Understanding the canon does not solve all questions about how to interpret the Bible, but it tells us that all the canonical books are trustworthy guides to God’s truth.

The Canon as a Gift to the Church

The canon is ultimately a gift that the Church received through God’s guidance. The Church did not invent the canon; the Church recognized it. God provided the apostles to teach the truth about Jesus. God inspired them to write letters and teaching that would guide the Church for all future centuries. God worked through the Church to separate these true, apostolic writings from the false and misleading ones that appeared later. The three tests of apostolicity, orthodoxy, and universality are not arbitrary human inventions. They flow from what the Church knew about how God worked through the apostles and how God protected the Church. A true apostolic writing would come from someone Jesus had chosen and trained. A true apostolic writing would teach what Jesus actually taught. A true apostolic writing would be recognized by the whole Church across many regions because God’s truth cannot be confined to one place. These tests reflect a real understanding of God’s plan for the Church.

The work of establishing the canon shows the partnership between God and the Church. God did not drop the Bible from heaven with a list of contents marked on the cover. Instead, God worked through real people, real bishops, real councils making real decisions. God guided the process through the Holy Spirit, but the people involved had to pray, study, read, consult with each other, and use their best judgment. The Church was not passive. The Church actively examined writings, compared teachings, tested claims of apostolic origin. Yet the Church also trusted that the Holy Spirit would guide this work. The result was that by the sixth century, the Church had reached a clear consensus about which books were scripture. This consensus has remained solid for over a thousand years. The fact that the canon has remained unchanged for so long, despite many challenges and questions, suggests that the Church did its work well under God’s guidance.

Living with the Closed Canon Today

Catholics today live with the finished canon that the Church established over many centuries. No new books will be added to the Bible. The Church might discover new manuscripts of the books that are already in the canon, or scholars might learn new things about when and where the books were written. But the canon itself is closed. This means that when Catholics use the Bible in prayer, study, and worship, they are using exactly what the Church determined to be apostolic scripture. The sixty-six books of the New Testament and the books of the Old Testament as the Church lists them are the Bible. Catholics accept this not because they are forced to, but because they recognize in this canon the authentic voice of the apostles calling them to follow Jesus.

The closure of the canon does not mean the Church has nothing left to do with scripture. The Church continues to interpret scripture for new times and new situations. The Church reflects on how scripture applies to modern problems that the apostles did not face directly. The Pope and the bishops continue to teach based on scripture. Councils can make new declarations about what scripture means for Catholic faith and practice. Priests and teachers help the faithful understand the Bible better. But all of this work happens within the canon that has already been established. The Church does not add new apostolic writings to guide believers. Instead, it helps people understand the apostolic writings that exist. The living tradition of the Church and the written scriptures work together, with scripture always holding a place of supreme importance (CCC 81). For Catholics, this is a source of stability and assurance. The Bible will not change. The apostolic message will remain the same. The Church can develop its understanding, but it will always look back to scripture as the measure of truth.