Bible believers may still benefit from some apocryphal writings as historical or devotional materials. The testimony of Jesus and the apostles as well as the mainstream of church history, however, weighs against their being recognized as Scripture.
When Protestants talk about the Bible they mean the sixty-six books of the Old and New Testaments. To these, Roman Catholicism and Eastern Orthodoxy add several other apocryphal or deuterocanonical books, plus additions to multiple biblical books. Even more apocryphal books exist, but they are not recognized as Scripture by any branch of professing Christianity.
Obviously, at some point choices had to be made about which writings would be recognized as Scripture and which would not. The process of recognizing some books and rejecting others is known as canonization, and the collection of recognized books is known as the canon. No doctrine of Scripture is complete without a discussion of canonization and canonicity.
The word canon was originally the name for a particular kind of straight reed. People would cut this reed to length and use it as a measuring rod. Eventually the word became a metaphor for any standard of measurement. Then it was applied to the collection of things that measured up to the standard. When we talk about the canon of Scripture, we are talking about the collection of writings that measure up to the standard of being recognized as the word of God. To say that a document is canonical is to say that it is God’s word and consequently that it is authoritative for faith and practice.
What is the standard for canonicity? The short answer is inspiration. A writing is canonical if and only if it has been inspired by the Holy Spirit. Properly speaking, human beings can never declare a writing to be canonical. Even the declarations of church councils do not make a document canonical. All they can do is to recognize its canonicity. Its canonicity depends entirely upon whether it has been inspired.
Consequently, discussions about canonicity are really discussions about inspiration. To know which writings are canonical, we must simply discover which writings have been inspired by the Holy Spirit. How can we do that? This question will have different answers depending upon which testament we are asking about.