The Book of Mormon
Believers declare that the Book of Mormon is "God's other testament" in addition to the Bible. According to tradition, God personally imparted the Book of Mormon to Mormon prophet Joseph Smith. To Mormons, no contradiction exists between the Bible and the Book of Mormon. The Bible is incomplete and the Book of Mormon simply fills in the gaps.
Revelations 22: 18-19, however, states in no uncertain terms, "I warn everyone who hears the words of the prophecy of this book: If anyone adds anything to them, God will add to him the plagues described in this book. And if anyone takes words away from this book of prophecy, God will take away from his share in the tree of life and in the holy city, which are described in this book." According to traditional Christians, this proves that the Bible is the only Christian scripture and that after Jesus, there are no other prophets.
Mormon trinity; original sin
Christian doctrine has historically advocated the existence of the Trinity, consisting of the Father, Son, and Holy Spirit, while Mormonism upholds "Three persons in three bodies."
Furthermore, according to traditional Christianity, Adam's and Eve's partaking of the forbidden fruit was a transgression against God's will and brought sin into the world dictating the necessity for judgment for humankind. But according to LDS teachings, Adam's sin was "a necessary step in the plan of life and a great blessing to all mankind."
"These doctrinal differences have caused many Christians to reject Mormonism and to refuse to refer to the Mormon Church as Christian," explains one religious scholar in Taiwan.
Temple enigma
The Three-Fold Mission carried out by members of the Mormon Church includes proclaiming the gospel, perfecting the saints (pursuing the perfection of self and others), and redeeming the dead (by performing vicarious baptisms for the dead--only done in temples).
In order to redeem the dead, the LDS Church encourages followers to carefully trace their family trees. Because of this, they have compiled the world's largest genealogical database.
Church members must wear white robes and non-Mormons are not permitted into the temple during ceremonies for the redemption of the dead. The uniquely Mormon baptism for the dead and the secretiveness of their temples raises hackles among followers of other Christian religions.