Most Christians view Christianity as beginning with the birth of Christ. Prophets in the Old Testament predicted the coming of the Messiah, but they knew not of the doctrines Christ would teach. Doctrines of The Church of Jesus Christ of Latter-day Saints reveal more about the continuity of Christianity — it has always existed.
Mormons understand God’s plan because of more scripture and modern revelation. Although the Bible says a bit about the fall of Lucifer and a war in heaven, most Christians see only God as preexisting the earth. In the view of the trinity, Christ during His mortal ministry was God incarnate. Discarding His resurrected body after His ascension, He rejoined the God essence.
Mormons reject these ideas. Prophets have revealed that all of us are eternal beings, the literal spirit-children of God the Father. We dwelt with Him for eons in a pre-mortal realm as spirits before being born physically on the earth. The resurrection is the ideal state, and both God the Father and Jesus Christ have perfect, albeit unspeakably glorious, resurrected bodies.
When we dwelt with God in the pre-mortal realm, sometimes called the pre-existence by Mormons, we were taught His great plan. Mortality would be a time to form relationships and families, and to prove our faith, as we progress toward becoming like God. We understood then that Jesus Christ would perform an atoning sacrifice to make up for our sins and transgressions; we knew none of us would live a perfect life. These concepts were plainly taught to Adam and Eve. Adam and his noble sons, grandsons, and great grandsons taught the fulness of the Gospel of Jesus Christ. One of his descendants, Enoch, led a people so righteous, they were taken to heaven.
All of the prophets of old both saw Christ in vision and understood His gospel. They taught it to the extent that their followers would receive it. From Moses on, the Israelites resisted to the point that knowledge and power was withheld from them because of their unworthiness.
Because of this view of Christianity and its eternal nature, Mormons see other ancient religions as atrophied versions of once-had truth. Thus, the student can see commonalities among all world faiths. Truths had trickled down from Adam’s time, and it distilled upon all men and women, who, blessed with the light of Christ as a guaranteed gift to all of God’s children, held on to some truths, even as they lost sight of others.
The Book of Mormon People
The main group of people in the Book of Mormon left Jerusalem around 600 B.C. just before the armies of Babylon destroyed it and took many captive. They were Judaites and Josephites, and they kept the Law of Moses after they arrived in America, looking forward to the coming of Christ. They knew the Law of Moses could not save them. They thoroughly understood that salvation would come through the atonement of Jesus Christ, just as their prophets taught them. They thoroughly understood the doctrines of repentance and faith, and sacrifice, resurrection, etc.
Yea, and they did keep the law of Moses; for it was expedient that they should keep the law of Moses as yet, for it was not all fulfilled. But notwithstanding the law of Moses, they did look forward to the coming of Christ, considering that the law of Moses was a type of his coming, and believing that they must keep those outward performances until the time that he should be revealed unto them.
Now they did not suppose that salvation came by the law of Moses; but the law of Moses did serve to strengthen their faith in Christ; and thus they did retain a hope through faith, unto eternal salvation, relying upon the spirit of prophecy, which spake of those things to come (Alma 25:15, 16).
And we talk of Christ, we rejoice in Christ, we preach of Christ, we prophesy of Christ, and we write according to our prophecies, that our children may know to what source they may look for a remission of their sins.
Wherefore, we speak concerning the law that our children may know the deadness of the law; and they, by knowing the deadness of the law, may look forward unto that life which is in Christ, and know for what end the law was given. And after the law is fulfilled in Christ, that they need not harden their hearts against him when the law ought to be done away (2 Nephi 25:26, 27).
There has always been a religious continuum on the earth, but not necessarily evolution of religious belief. Adam had a perfect knowledge of the doctrine of Christ. Later religions had less. They lost considerable knowledge. But always, the Lord has sent prophets, when there were people to receive them, and He has restored Christ’s primitive church in its fulness, with all its attendant miracles in these last days, just before His Son will come again.