The Mormon church claims that the Bible has been corrupted and does not contain the "fullness of the gospel". Therefore additional (Latter-Day) revelation was and is necessary:

• Mormon scriptures state: "[when] the book [the Bible] proceeded forth from the mouth of a Jew...it contained the fulness of the gospel of the Lord, of whom the twelve apostles bear record" (1 Nephi 13:24), but that afterwards "thou seest the formation of that great and abominable church...after the book hath gone forth through the hands of the great and abominable church, that there are many plain and precious things taken away from the book, which is the book of the Lamb of God. And after these plain and precious things were taken away it goeth forth unto all the nations of the Gentiles" (Book of Mormon, 1 Nephi 13:26,28). See also Doctrines of Salvation, vol.3, p.190-191.
• Joseph Smith claimed: "it was apparent that many important points touching the salvation of men, had been taken from the Bible, or lost before it was compiled" (Teachings of the Prophet Joseph Smith, p.10); "I believe the Bible as it read when it came from the pen of the original writers. Ignorant translators, careless transcribers, or designing and corrupt priests have committed many errors" (Teachings of the Prophet Joseph Smith, p. 327).
• Orson Pratt's stated: "who, in his right mind, could for one moment, suppose the Bible in its present form to be a perfect guide? No one can tell whether even one verse of either the Old or New Testament conveys the ideas of the original author" (Journal of Discourses, vol. 7, p. 28).

Mormons claim additional revelation comes through their scriptures:

• Joseph Smith stated: "I told the brethren that the Book of Mormon was more correct than any book on earth, and the keystone of our religion, and a man would get nearer to God by abiding its precepts, than by any other book" (Teachings of the Prophet Joseph Smith, p.194).
• Apologist Bruce McConkie states: The Bible of the Old World has come to us from the manuscripts of antiquity - manuscripts which passed through the hands of uninspired men who changed many parts to suit their own doctrinal ideas. Deletions were common, and, as it now stands, many plain and precious portions and many covenants of the Lord have been lost. As a consequence, those who rely upon it [the Bible] alone stumble and are confused... (The Ensign, December 1985, p 55).

Mormons claim additional revelation came (and still comes) through their Prophets and Leaders. This claim makes their role very different from that of leaders in orthodox Christian churches.

• Joseph Smith made very clear statements about his importance in God's plan: Neither Paul, John, Peter, nor Jesus ever did it. I boast that no man ever did such a work as I" (History of the Church, vol. 6, p.408-409).
• President and prophet Ezra Taft Benson stated: "...the [Living] Prophet does not have to say 'Thus saith the Lord' to give us scripture" (Fourteen Fundamentals in Following the Prophets, BYU Devotional, Feb 26, 1980, p.3,6).
• Orson Pratt explains that not all prophecy was published in the "Standard Works": "Now I want to prophecy a little...I want to prophecy that all men and women who oppose the revelation which God has given in relation to polygamy will find themselves in darkness..." (Journal of Discourses, vol. 17, p.224-225).
• Brigham Young said: "Joseph Smith in his lifetime did not receive every thing connected with the doctrine of redemption" (Millenial Star, vol.6, p.121).
• Brigham Young also said: "I have never yet preached a sermon and sent it out to the children of men, that they may not call Scripture (Journal of Discourses, vol. 13, p.95).
• F.D. Richards confirms this: "Concerning the doctrine that Adam is our Father and God...the prophet and Apostle Brigham has declared it, and that is the word of the Lord" (Millenial Star, August 26, 1854, vol.16, p.534).
• Mormon Edward W. Tullidge wrote: "When Brigham Young proclaimed to the nations that Adam was our Father and God...-he made the most important revelation ever oracled to the race since the days of Adam himself" (The Women of Mormondom, p.79,179,196-197, 1877).
• Mormon A.F. McDonald commented: "if the President makes a statement it is not our prerogative to dispute it...when I first heard the doctrine of Adam being our Father and God, I was favorably impressed---enjoyed and hailed it as a new Revelation" (Minutes of the School of Prophets, Provo, UT, 1868-1871, p.38-39).
• John Nuttal recorded this: "Prest Young was filled with the spirit of God & revelation & said...Father Adam's oldest son (Jesus the Savior) who is the heir of the family is Father Adam's first begotten in the spirit world" (Wednesday Feb. 7, 1877, Journal of John Nuttal, vol.1, p.18-21).
• An official and widely distributed LDS document states: "When our leaders speak, the thinking has been done. When they point the way, there is no other which is safe. When they give direction, it should mark the end of controversy" (Ward teachers message for June, 1945).
• President Heber C. Kimball said: "But if you are told by your leader to do a thing, do it. None of your business whether it is right or wrong" (Journal of Discourses, vol.6, p.32).
• A letter from the First Presidency (Presidents Benson, Hinckley, and Monson) to all members of the Church states: "The most reliable way to measure the accuracy of any biblical passage is not by comparing different texts [in the Bible], but by comparison with the Book of Mormon and modern-day revelations [through them]". (Church News, June 20, 1992, page 3, letter dated May 22, 1992).
• Ezra Taft Benson stated: "the Living Prophet...is more vital to us than the Standard Works [Bible, Book of Mormon, etc.]...The living Prophet is more important to us than a dead prophet [the Old Testament Prophets]" (Fourteen Fundamentals in Following the Prophets, BYU Devotional, Feb 26, 1980, p.3,6).

In contrast, The Bible claims that written, inerrant, authoritative revelation ended with Jesus and his apostles:

• "You should remember the words spoken beforehand by the holy prophets and the commandment of the Lord by your apostles" (2 Peter 3:2).
• "Paul, according to the wisdom given him, wrote to you, as also in all his letters, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the scriptures..." (2 Peter 3:15-16).
• "Do not add to His words Or He will reprove you, and you will be proved a liar" (Prov. 30:6).
• "You shall not add to the word which I am commanding you, nor take away from it" (Deut. 4:2).
• "I testify to everyone who hears the words of the prophecy of this book: if anyone adds to them, God shall add to him the plagues which are written in this book; and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the tree of life..." (Rev. 22:18-19).

Why is this so important? Because false teachers will inevitably come with a different gospel: