The Introduction to The Great Controversy was written by Ellen White. One of the main purposes of this introduction is to deal with the issue of inspiration: both of the Bible, and the purpose of the “spirit of prophecy” promised to the church after the Bible was finalized.
Since Protestants rightly put emphasis on “the Bible and the Bible only” as opposed to tradition, the gift of prophecy promised to the New Testament church seemed needless, since “we have the Bible, what more do we need?” Then when fanatics would arise claiming to be inspired, but who put themselves above the Bible, and either contradicted or minimized it’s teachings, the idea that prophecy was not only needless, but dangerous, seemed to be justified.
So Ellen White made clear in the introduction to The Great Controversy, just what her role was, and how her writings related to the Bible. She also summed up the purpose of this book:
“To unfold the scenes of the great controversy between truth and error; to reveal the wiles of Satan, and the means by which he may be successfully resisted; to present a satisfactory solution of the great problem of evil, shedding such a light upon the origin and the final disposition of sin as to make fully manifest the justice and benevolence of God in all His dealings with His creatures; and to show the holy, unchanging nature of His law, is the object of this book.”