To justify their separation from the Catholic Church, Protestants require a theory of "Great Apostasy". This is the idea that the Christian Church vanished from the earth shortly after the death of the last Apostle, leaving us with only the Scriptures as our guide.
But as Devin Rose points out: the Great Apostasy "solves" one problem while introducing another. How can we have any confidence that the "apostate" 4th-century church successfully identified the 27 books of the New Testament without omitting inspired works or introducing spurious texts?
As far as I can tell, Mormon author James E Talmage doesn't answer this question in his 1909 work entitled "The Great Apostasy", and yet Mormons also accept the New Testament canon of the Catholic Church. His Scriptural "proofs" appear in pages 24-38 and only the last couple proofs come from the Book of Mormon.