‘They also that erred in spirit
shall come to understanding,
and they that murmured
shall learn doctrine.’Isa. 29:1–24
Such is the purpose of the Book of Mormon. Members of false churches who err in spirit, who think they have the truth, are brought by the Book of Mormon to the fulness of the gospel.
Those who have based their beliefs on isolated verses and obscure passages, and who have wondered and murmured at seeming biblical conflicts, come to learn sound doctrine.
No longer do they worry about the atonement, salvation by grace alone, infant baptism, the priesthood, the gifts of the Spirit, the passages about an apostasy, a gospel restoration, and the gathering of Israel.
All things fall into place because of this new witness for Christ and his gospel, this witness which bears the name of the prophet Mormon
(Bruce R. McConkie, The Millennial Messiah, pp. 174–75)