"The Book of Mormon is additional scripture because Mormons believe that God continues to give revelation to His children in modern times and because Mormons believe that there are many groups which must have had contact with God and His prophets to whom Christ referred to when he said “Other sheep have I which are not of this fold.”

And blessed be he that shall bring this thing (the Book of Mormon) to light; for it shall be brought out of darkness unto light, according to the word of God; yea, it shall be brought out of the earth, and it shall shine forth out of darkness, and come unto the knowledge of the people; and it shall be done by the power of God. And if there be faults they be the faults of a man.