The question of the scope of the canon, or the list of books that make up our Bible, may confuse many people, particularly those who are accustomed to a number of books clearly defined by their particular church confessions. Some have argued that if one questions a particular book’s canonicity, the implication is that one does not believe in a divinely inspired Bible. Perhaps the clearest illustration of this in history comes from the life of Martin Luther who, at one point in his ministry, had strong reservations about including the Book of James in the New Testament canon. Though it is abundantly clear that Luther believed in an inspired Bible, he had questions about whether a particular book should be included in that inspired Bible. Several scholars have tried to see Luther’s questioning of the Book of James to deny that he believed in inspiration. It is very important to see the difference between the question of the scope of the canon and the question of the inspiration of the books that are recognized as included in the canon. In other words, the nature of Scripture and the extent of Scripture are different questions that must not be confused.
From: Can I Trust the Bible? by R. C. Sproul; The Crucial Questions Series, No. 2 (Sanford: Reformation Trust, 2009), pp. 4-5. Originally published under the title Explaining Inerrancy: A Commentary in 1980.