Roman Catholicism, Mormonism, and the Biblical Gospel
Roman Catholicism and Mormonism both undermine the authority of Scripture by claiming that additional revelations — i.e., the Magisterium, the Pope, Tradition; and the Book of Mormon, the Doctrine & Covenants, the Prophet, and so on — are necessary to make sense of Scripture. This is detrimental to the sufficiency of the Word of God for the Spirit to apply Christ’s redemptive work. The Bible calls believers to fides implicita (implicit faith) in Christ alone, while communions such as Roman Catholicism and Mormonism demand its adherents exercise fides implicita in the visible institution. The inconvenient truth of both belief systems is their seminal teaching of extra ecclesiam nulla salutis, “outside of the church there is no salvation.”
Roman Catholicism and Mormonism both append works to faith as a necessary component of justification. The Roman Catholic view and the Mormonism view resemble this: faith + works = justification. The Protestant view, which is reminiscent of the biblical view, is that faith = justification + works. The difference between these two formulas is the difference between understanding and misunderstanding the gospel. If any communion claims to be Christian but denies or condemns an essential truth of Christianity, then far from proving itself to be the true representation of Christianity, at that point that organization betrays itself as apostate and no longer a true church.
Mormonism, like Roman Catholicism, is essentially a sacerdotal communion. They both maintain a view of ex opere operato. In Mormonism, baptism has the power to actually confer grace to its recipient, described in the Book of Mormon as “the gate.” This echoes the Roman Catholic teaching that baptism is “the gateway to life in the Spirit” and “the door” which gives access to the sacraments. It is built into both systems that these sacraments can be performed only by someone with the true authority of the church. Meanwhile, Jesus simply said, “I am the door,” and enunciated implicit trust in Himself as necessary for eternal life, and the precursor to obeying the law of God.