Have you ever looked at your Bible and wondered, "How do we know that these 66 books, and no others, comprise the inspired Word of God?"

That is a critically important question, since there are many today who would deny that these 66 books truly make up the complete canon of Scripture.

The Roman Catholic Church, for example, claims that the Apocryphal books which were written during the inter-testamental period (between the Old and New Testaments) ought to be included in the Bible. Cult groups like the Mormons want to add their own books to the Bible—like the Book of Mormon, The Doctrines and Covenants, and The Pearl of Great Price. And then there are popular books and movies, like The Da Vinci Code, that claim centuries after these books were written Christians (like Constantine) determined what was in the Bible.

So, how do we know that “all Scripture” consists of these 66 books? How do we know that the Bible we hold in our hands is the complete Word of God?

There are a number of ways we could answer such questions; in fact, we could spend weeks studying the doctrine of canonicity, carefully walking through the relevant biblical and historical details. And there are many helpful books that can guide you through that wealth of information.

But in this article, I would like to offer a simple answer that I hope will be helpful – because it gets to the heart of the matter.

It is this:

We believe in the 39 books of the Old Testament, because the Lord Jesus Christ affirmed the Old Testament. And we believe in the 27 books of the New Testament, because the Lord Jesus Christ authorized His apostles to write the New Testament.

The doctrine of canonicity is grounded in the lordship of Jesus Christ. If we believe in Him and submit to His authority, then we will simultaneously believe in and submit to His Word. Because Jesus affirmed the Old Testament canon, we affirm it with Him. Because He authorized His apostles to write the New Testament, we also embrace it.

It was not the Catholic church that determined the canon. Constantine did not determine the canon. Joseph Smith certainly did not determine the canon. No, it is the authority of Christ Himself, the Lord of the church and the incarnate Son of God, on which the canon of Scripture rests.

The Old Testament Canon

When it comes to the Old Testament, Jesus Christ affirmed the Jewish canon of His day—consisting of the very same content that we have today in our Old Testament.

A study of the gospels shows that, throughout His ministry, Jesus affirmed the Old Testament in its entirety (Matt. 5:17–18)—including its historical reliability (cf. Matt. 10:15; 19:3–5; 12:40; 24:38–39), prophetic accuracy (Matt. 26:54), sufficiency (Luke 16:31), unity (Luke 24:27, 44), inerrancy (Matt. 22:29; John 17:17), infallibility (John 10:35), and authority (Matt. 21:13, 16, 42).

He affirmed the Law, the Writings, and the Prophets and all that was written in them; clearly viewing the Old Testament Scriptures as the Word of God (Matt. 15:16; Mark 7:13; Luke 3:2; 5:1; etc.).

The first century Jews did not consider the Apocryphal books to be canonical. And neither did Jesus. He accepted the canon of the Jews as being the complete Old Testament. He never affirmed or cited the Apocryphal books – and neither do any of the writers of the New Testament.

(Some may wonder about Jude’s reference to the Book of Enoch. But the Book of Enoch is not part of the Roman Catholic Apocrypha. It was simply a well-known piece of Jewish literature at that time, which Jude cited for the purpose of an illustration, much like Paul did when he quoted pagan poets on Mars Hill in Acts 17.)

For those who might wonder, “Why don’t Protestants accept the Apocrypha?” the simple answer is that Jesus never affirmed it as Scripture. And neither did the apostles.

Many of the early church fathers also did not regard the Apocryphal books as being canonical. They considered them helpful for the edification of the church, but not authoritative. Even the fifth-century scholar Jerome (who translated the Latin Vulgate -- which became the standard Roman Catholic version of the Middle Ages) acknowledged that the Apocraphyl books were not to be regarded as either authoritative or canonical.

So we accept the canonicity of the Old Testament on the basis of the authoritative affirmation of our Lord. And we reject the canonicity of the Apocryphal books based on the absence of affirmation of those inter-testamental writings by Jesus.

The New Testament Canon

The same principle applies to the New Testament canon. Our Lord not only affirmed the Jewish canon of the Old Testament, He also promised to give additional revelation to His church through His authorized representatives—namely, the apostles.

Jesus made this point explicit in John 14–16. On the night before His death, Jesus said to His disciples:

These things I have spoken to you while abiding with you. But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all that I said to you. - John 14:25–26

That last line is essential for the doctrine of canonicity. Jesus promised the apostles that the Holy Spirit would help them remember all that He had said to them.

That is an amazing promise, the fulfillment of which is found in the four gospel accounts—where the things that our Lord did and said are perfectly recorded.

Two chapters later, in the same context, the Lord promised the apostles that He would give them additional revelation through the Holy Spirit:

I have many more things to say to you, but you cannot bear them now. But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak of His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. He will glorify Me, for He will take of Mine and will disclose it to you. All things that the Father has are Mine; therefore I said that He takes of Mine and will disclose it to you. - John 16:12–15

Where is that additional revelation found? It is found in the New Testament epistles, wherein the Spirit of Christ guided the apostles to provide the church with inspired truth.

The New Testament, then, was pre-authenticated by Christ Himself, as He authorized the apostles to be His witnesses in the world (Matt. 28:18–19; Acts 1:8). We embrace and submit to the New Testament writings because they were penned by Christ’s authorized representatives, being inspired by the Holy Spirit in the same way as the Old Testament prophets (cf. 2 Pet. 3:19–21).

With that in mind we could go book-by-book through the New Testament, and we will find that it meets this criteria.

• The Gospels of Matthew & John were both written by apostles.

• The Gospel of Mark is a record of the memoirs of the Apostle Peter, written by Mark under Peter’s apostolic authority.

• The Gospel of Luke (and the book of Acts) were the product of a careful investigation and eyewitness testimony (Luke 1:2), research that would have included apostolic sources. Moreover, as the companion of the Apostle Paul, Luke wrote under Paul’s apostolic oversight. (For instance, Paul affirmed Luke 10:7 as being part of the Scripture in 1 Tim. 5:18.)

• The Pauline Epistles (Romans–Philemon) were all written by the Apostle Paul.

• The authorship of Hebrews is unknown, but many in church history believed it to have been written by Paul. If not penned by Paul himself, it was clearly written by someone closely associated with Paul’s ministry—and therefore, by extension, under his apostolic authority.

• The General Epistles (the letters of James, Peter, and John) were written by apostles. Peter also acknowledged Paul's writings as being Scripture in 2 Peter 3:15–16.

• The epistle of Jude was written by the half-brother of Jesus (Matthew 13:55; Mark 6:3) who operated under the apostolic oversight of his brother James (cf. Jude 1).

• And finally, the book of Revelation was written by the Apostle John.

Every book of the New Testament was written under apostolic authority—either by an apostle or someone linked to apostolic ministry. Thus, we submit to these books because they originate from Christ’s authorized representatives. In submitting to them, we are submitting to the Lord Himself.

The reason the canon is closed is because there are no longer any apostles in the church today. And there have not been any since the end of the first century, with the conclusion of the foundation age of the church (cf. Eph. 2:20).

So, why these 66 books?

Because God inspired them! They are His divine revelation. And Christ confirmed that fact. He affirmed the Old Testament canon, and He authorized the New Testament canon (cf. Heb. 1:1–2).

The authority of the Lord Jesus Himself, then, is the basis for our confidence that the Bible we hold is indeed “All Scripture."